In this study, the clinical efficacy and safety of apatinib combined with irinotecan in HER2-negative patients with first-line treatment failure for advanced gastric adenocarcinoma and gastroesophageal junction (GEJ) adenocarcinoma were evaluated.

We performed a single-arm, retrospective study at one tertiary hospital in Guangzhou, China. Eligible patients aged 28-77 years with histologically confirmed HER2-negative advanced gastric cancer who had previously received first-line treatment were included. The patients received irinotecan (180 mg/m2 intravenously once every 3 weeks) plus oral apatinib (500 mg once daily on days 1-21 of each 3-week cycle), until disease progression, unacceptable toxicity, or death. The primary endpoints were progression-free survival (PFS) and overall survival (OS), which were calculated via the Kaplan‒Meier method.

Between Feb 21, 2019, and Aug 14, 2023, 79 patients met the inclusion criteria. The median PFS was 3.20 months (95% CI, 1.57‒4.83), and the median OS was 7.60 months (95% CI, 5.11‒10.10). According to RECIST version 1.1, 15 patients (18.99%) achieved an objective response, and 31 patients (39.24%) achieved disease control. In terms of the safety profile, 72.2% of patients experienced treatment-emergent adverse events of any grade, among whom, 59.5% of patients experienced grade 1-2 adverse events and 12.7% of patients experienced grade 3-4 adverse events.

Apatinib combined with irinotecan demonstrates modest efficacy with manageable safety profiles in HER2-negative patients with advanced gastric or GEJ adenocarcinoma for whom first-line treatment has failed. Further prospective studies are warranted.

Claudin 18.2 (CLDN18.2) immunohistochemical (IHC) expression can be used to select patients with gastric/gastroesophageal junction adenocarcinomas for zolbetuximab (IMAB362) therapy, zolbetuximab (IMAB362) being a monoclonal antibody targeting CLDN18.2. The aim of this study was to correlate IHC expression of CLDN18.2 with clinicopathologic and molecular features in a large series of digestive tract cancers. IHC for CLDN18.2 was performed on tissue microarrays from 1404 adenocarcinomas including 155 gastric/gastroesophageal, 74 pancreatic ductal, and 1175 colorectal (576 in the initial test cohort; 599 in the subsequent validation cohort), and correlated with HER2 and mismatch repair (MMR) status. Cases were scored as CLDN18.2 positive or negative, with positivity defined as moderate-to-strong membranous staining in ≥75% of tumor cells. CLDN18.2 expression was correlated with clinicopathologic and molecular features for all colorectal adenocarcinomas. CLDN18.2 was positive in 39% (61/155) of gastric/gastroesophageal adenocarcinomas, 38% (28/74) of pancreatic ductal adenocarcinomas, and 3.4% (40/1175) of colorectal adenocarcinomas (P < .001). For gastric/gastroesophageal and pancreatic ductal adenocarcinoma, there was no correlation between CLDN18.2 expression and either HER2 or MMR status. In contrast, CLDN18.2-positive colorectal adenocarcinomas had distinct clinicopathologic and molecular features. CLDN18.2-positive colorectal adenocarcinomas were more frequently proximally located and were more often MMR deficient and BRAF V600E positive (all with P < .05). Quantitative pathologic analysis using the digital pathology biomarker QuantCRC (Aiforia) demonstrated marked differences in histologic features between CLDN18.2-positive and CLDN18.2-negative colorectal adenocarcinomas, with CLDN18.2-positive tumors having an increased tumor:stroma ratio and %mucin but decreased %immature stroma in both the test and validation cohorts (all with P < .05). In conclusion, CLDN18.2-positive colorectal adenocarcinomas are frequently MMR deficient and BRAF V600E mutated, and demonstrate distinct histologic features. Future studies addressing the efficacy of zolbetuximab therapy in this subset of colorectal cancers are needed.

Claudin 18 isoform 2 (CLDN18.2) is a potential therapeutic target in gastric cancer (GC). However, combining chemotherapy with anti-CLDN18.2 antibodies has shown limited efficacy in CLDN18.2-positive GC, and chemotherapy-induced changes in the tumor microenvironment (TME) remain unclear.

This study analyzed 37 GC samples, including 11 CLDN18.2-positive cases, using single-cell RNA sequencing and multiplex immunofluorescence to assess chemotherapy-driven TME changes in CLDN18.2-positive GC.

In chemotherapy-treated CLDN18.2-positive GC, cytotoxic natural killer (NK) cells displayed antibody-dependent cytotoxicity (ADCC)-related genes at lower levels than in untreated CLDN18.2-positive GC, while regulatory T cells (Tregs) and tumor-associated macrophages (TAMs) showed TGFB1 expression at higher levels. Additionally, NK cells, Tregs, and TAMs were more abundant in chemotherapy-treated than untreated CLDN18.2-positive GC. These chemotherapy-induced changes were absent in CLDN18.2-negative GC. Cell-cell interaction analysis identified unique interactions in chemotherapy-treated CLDN18.2-positive GC, including CCL5-CCR5 signaling between cytotoxic NK cells (Sender) and effector Tregs (Receptor) and TGFB1-TGFBR signaling between effector Tregs (Sender) and TAMs (Receptor). Cytotoxic NK cells expressed CCL5 at higher levels, CCR5-positive Tregs were more prevalent, and TAMs exhibited higher TGF-β receptor signature scores in chemotherapy-treated than untreated CLDN18.2-positive GC.

Our findings indicate that chemotherapy can drive immunosuppressive TME modifications specific to CLDN18.2-positive GC.

Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal, with a five-year survival rate below 15 %. Claudin 18.2 (CLDN18.2) has emerged as a novel potential therapeutic target in PDAC. Zolbetuximab, a monoclonal antibody targeting CLDN18.2, has demonstrated therapeutic benefit in gastric cancers and is now in phase 2 clinical trials for PDAC. Trial eligibility for zolbetuximab requires tumor membranous immunohistochemical staining with the pan-claudin 18 companion diagnostic antibody clone 43-14A. However, the expression of CLDN18 detected using this clone has only been evaluated in 62 patients from a single retrospective study. Herein, we report immunohistochemical staining using 43-14A on surgically resected PDAC samples (n = 120). Samples were stained following the protocol used in clinical trials, using the 43-14A VENTANA antibody in a prediluted kit, and according to the manufacturer's recommended protocol. Positive cases were defined as ≥ 75 % of tumor cells exhibiting membranous staining with an intensity of ≥ 2+. Out of 120 PDAC cases, 39 (32.5 %) stained positive for CLDN18 with 43-14A. A significant association was observed between lower tumor grade and higher 43-14A staining (p < 0.05). CLDN18-positive cases demonstrated significantly improved survival at the cohort's median overall survival (23 months, p < 0.05), suggesting that claudin expression could serve as a both a diagnostic and prognostic marker. Our findings indicate that 32.5 % of PDAC tumors in this cohort are positive for CLDN18, suggesting that a significant proportion of patients with PDAC could benefit from zolbetuximab and other CLDN18.2 targeted immunotherapies if pancreatic cancer therapeutic trials prove successful.

Monoclonal antibodies against claudin (CLDN) 18.2 (a component of tight junctions) in gastric epithelial cells are an emerging therapeutic option for patients with advanced gastric and esophageal adenocarcinoma. Phase 2 and 3 trials have shown clinical efficacy in patients whose tumors show high expression of CLDN18 by immunohistochemistry, and the US Food and Drug Administration has recently approved a drug for patients with advanced gastric and gastroesophageal adenocarcinoma and high CLDN18 expression. Adenocarcinoma of the bile ducts, a.k.a. cholangiocarcinoma (CCA), may share morphologic and immunophenotypic qualities with gastric adenocarcinoma, and are lethal tumors with limited therapeutic options. The purpose of this study was to determine if primary tumors of the bile ducts show expression of CLDN18 with the use of a monoclonal antibody to CLDN18, and if so, if the extent of expression is similar to that seen in the gastric and esophageal tumors of patients who responded to anti-CLDN18.2 therapeutics.

Tissue microarrays containing 41 intrahepatic cholangiocarcinomas, 36 hilar cholangiocarcinomas, and 28 distal bile duct cholangiocarcinomas were stained with a monoclonal antibody which detects CLDN18 (Ventana 43-14A). The percentage of tumor cells staining and intensity was recorded for each case with tumors with 75% of cells showing moderate to strong intensity being considered high expressers.

High expression was seen in 14.63% of intrahepatic, 8.3% of hilar, and 17.8% of distal bile duct cholangiocarcinomas. Overall, 13.33% of CCAs expressed CLDN18 to an extent which would qualify for treatment in the gastric and esophageal trials.

Given the poor prognosis and current lack of therapeutic options, trials of anti-CLDN18.2 inhibitors could be considered in patients with CCA and high expression of CLDN18 by immunohistochemistry.

Anti-claudin 18.2 (anti-CLDN18.2) therapy has been approved for patients with CLDN18-positive gastric and gastroesophageal junction adenocarcinomas. The current study aims at evaluating the expression of CLDN18 in a large cohort of pathologically characterized biliary tract cancers (BTCs).

A series of 237 BTCs were collected and reviewed under the BITCOIN protocol. All samples were assessed for CLDN18 status using immunohistochemistry (clone 43-14A). Tumor positivity for CLDN18 was determined if ≥75% of tumor cells exhibited moderate-to-strong membranous staining.

CLDN18 expression was found in 29.5% of BTCs (70/237), with the highest rates in gallbladder carcinoma (GBC; 62.5%; 20/32) and extrahepatic cholangiocarcinoma (eCCA; 53.4%; 31/58), compared with intrahepatic cholangiocarcinoma (iCCA; 12.9%; 19/147) (P < 0.0001). CLDN18 positivity was detected in 5.5% of cases (13/237), most common in GBC (15.6%; 5/32), followed by eCCAs (8.6%; 5/58) and iCCAs (2.0%; 3/147) (P = 0.0045). Most CLDN18-positive samples (10/13) exhibited a heterogenous staining pattern. In iCCAs, large duct subtypes had higher CLDN18 expression [33.3% (10/30) versus 7.7% (9/117), P = 0.0002] and positivity [6.7% (2/30) versus 0.9% (1/117), P = 0.106] than small duct iCCAs. No significant differences were observed across GBC and eCCA histotypes, and CLDN18 was not associated with IDH1 or FGFR2 status in iCCAs.

This study demonstrates that CLDN18 expression is present in a subset of BTCs, with significantly higher positivity rates in GBCs and eCCAs compared with iCCAs. In iCCAs, CLDN18 expression was more frequent in the large duct subtype but was not associated with IDH1 or FGFR2 status. These findings suggest that CLDN18 could be a potential therapeutic target in BTCs, warranting further prospective studies to evaluate its clinical significance and impact on patient outcomes.

Claudin 18.2 (CLDN18.2) has emerged as a promising therapeutic target for CLDN18.2-expressing gastric cancer (GC). We sought to examine the heterogeneity of CLDN18.2 expression between primary GC (PGC) and metastatic GC (MGC) using various scoring methods.

We retrospectively analyzed data from 102 patients with pathologically confirmed paired primary and metastatic gastric or gastroesophageal junction adenocarcinomas. CLDN18.2 expression was evaluated through immunohistochemistry on formalin-fixed paraffin-embedded tissue samples. We assessed CLDN18.2 positivity using multiple scoring approaches, including the immunoreactivity score, H-score, and the percentage of tumor cells showing moderate-to-strong staining intensity. We analyzed the concordance rates between PGC and MGC and the association of CLDN18.2 positivity with clinicopathological features.

CLDN18.2 positivity varied from 25% to 65% depending on the scoring method, with PGC consistently showing higher expression levels than MGC. Intratumoral heterogeneity was noted in 25.5% of PGCs and 19.6% of MGCs. Intertumoral heterogeneity, manifesting as discordance in CLDN18.2 positivity between PGC and MGC, was observed in about 20% of cases, with moderate agreement across scoring methods (κ=0.47 to 0.60). In PGC, higher CLDN18.2 positivity correlated with synchronous metastasis, presence of peritoneal metastasis, poorly differentiated grade, and biopsy specimens. In MGC, positivity was associated with synchronous metastasis, presence of peritoneal metastasis, and metastatic peritoneal tissues.

CLDN18.2 expression demonstrates significant heterogeneity between PGC and MGC, with a 20% discordance rate. Comprehensive tissue sampling and reassessment of CLDN18.2 status are crucial, especially before initiating CLDN18.2-targeted therapies.

Gallbladder carcinoma (GBC) is frequently diagnosed and treated in advanced stages and has a poor prognosis. Recent studies have identified claudin18.2 (CLDN18.2) as a promising target in digestive system cancer. In this study, we aimed to determine the expression of CLDN18.2 and its correlation with clinicopathological characteristics in patients with GBC.

The expression of CLDN18.2 of 228 patients with GBC was studied via immunohistochemistry. Immunostained samples were evaluated according to the H-score. The samples were divided into low/negative (H-score=0-49) and high/positive (H-score=50-300) expression groups. The correlations between CLDN18.2 and various clinicopathological characteristics, including survival, were assessed. Multiplex immunofluorescence and image acquisition were used to analyse the relationship between CLDN18.2 expression and the immune microenvironment.

The overall positive CLDN18.2 staining rate was 39.91% (91/228); 137 (60.08%) were given 0 points, 30 (13.15%) were given 1 point, 28 (12.28%) were given 2 points and 33 (14.47%) were given 3 points. Low CLDN18.2 expression was correlated with adverse prognostic factors, including poor differentiation, deep infiltration depth, lymph node metastasis and distant metastasis. High CLDN18.2 expression was associated with better survival. Furthermore, the distribution of immune cell subsets significantly differed between the high and low CLDN18.2 expression groups.

The correlations between the expression of CLDN18.2 and clinicopathological characteristics and prognosis suggest that early-stage patients could benefit more from future anti-CLDN18.2 treatment and that CLDN18.2 may function as a pivotal regulatory molecule in patients with GBC. The underlying mechanism may be related to immune activation caused by high CLDN18.2 expression.

Claudin 18.2 is a transmembrane protein, part of the tight-junction complex, selectively expressed in gastric epithelium. It is showing promising results as a target in advanced gastric cancer in phase 3 clinical trials using a monoclonal antibody against claudin 18.2. A systematic review on expression of claudin 18.2 in gastric cancer was performed using the PubMed database. The following search expression was used: ("Stomach Neoplasms" [Mesh]) AND (("claudin-18[TIAB]") OR ("CLDN18[TIAB]")). A total of n=99 articles were retrieved. Of those, 17 preclinical studies about claudin 18.2 expression by immunohistochemistry were selected. The results of those studies showed great variability in the criteria used for defining the thresholds for positivity of the stain. The proportion of claudin 18.2 positive cases varied between 24% and 83%. In works using a positivity threshold set at >40% or >70% of cells with membranous/cytoplasmic staining at 2+/3+ intensity, the average rate of positive cases was 50% or 30%, respectively (similar with clones 43-14A and EPR19202). Positivity of claudin 18.2 was associated with advanced stage, diffuse phenotype and PD-L1 and EBV positivity in some of the studies. Variability in criteria used to define claudin 18.2 positivity, as well as methodological differences, could explain the variation in the proportion of positive cases described, as well as the inconsistency of the association with clinical, molecular, and survival variables. The upcoming anticlaudin 18.2 therapy in advanced gastric cancer should prompt pathology laboratories to adjust their staining protocols and evaluation criteria in their series of patients, to further establish the association of claudin expression with clinical and molecular variables.

Pancreatic ductal adenocarcinoma (PDA) is a highly aggressive tumor with limited treatment options. Zolbetuximab, a monoclonal antibody against the tight junction protein Claudin 18.2 has recently been developed. At present, few and conflicting data have been reported regarding the clinical-pathological features of Claudin 18.2 expression in PDA. The present study investigated the expression of Claudin 18.2 in histological samples from PDA patients with the aim of verifying its utility as a therapeutic biomarker. Claudin 18.2 immunoreactivity was assessed by immunohistochemical staining on 70 formalin-fixed, paraffin-embedded PDA specimens (28 surgical specimens and 42 fine needle aspiration biopsies). The results obtained were associated with the clinicopathological characteristics and the survival rate of patients. Claudin 18.2 was detected only in neoplastic cells, not in normal pancreatic tissue. Claudin 18.2 was positive in 50% of samples and a higher expression was associated with well- and moderately-differentiated tumors and lymph node-negative status. The high expression of Claudin 18.2 in neoplastic tissue and absence in normal cells suggested that this protein had an attractive role in PDA as both a diagnostic and a prognostic-therapeutic marker. High expression of Claudin 18.2 in neoplastic tissue was associated with more favorable prognostic parameters and the high percentage of positive samples obtained suggests that Zolbetuximab may be suitable for a large number of patients.

Anti-claudin-18.2 (CLDN18.2) therapy was recently approved for the treatment of gastric or gastro-oesophageal junction adenocarcinoma. The aim of the present study was to investigate the expression of CLDN18.2 in cholangiocarcinoma (CCA) to determine whether there is a subgroup of patients who might also benefit from anti-CLDN18.2 therapy.

A tissue microarray (TMA) cohort of all CCA patients who underwent surgical resection with curative intent between August 2005 and December 2021 at University Hospital Frankfurt were immunohistochemically evaluated using the VENTANA® CLDN18 (43-14A) antibody. Tumour positivity for CLDN18.2 was determined as follows: ≥ 75% of tumour cells with moderate-to-strong CLDN18 membranous staining. In total, 160 patients with surgically resected CCA were suitable for immunohistochemistry (IHC) analysis. Of the patients, 13.1% (n = 21) showed moderate to strong membranous staining of VENTANA® CLDN18 antibody, while 86.9% (n = 139) were negative. Subtype analysis revealed strong differences in CLDN18 expression. Positive staining of CLDN18 could be observed in 26.5% (n = nine of 34) and 7.4% (n = seven of 95) of the perihilar (pCCA) and intrahepatic (iCCA) subgroup, respectively. CCA patients with CLDN18 expression had a more frequently intraoperative finding of distant metastasis (P = 0.002), lymph node metastasis (P = 0.008) and positive perineural invasion (Pn1) status (P = 0.022).

The present study suggests that a subset of patients with CCA exhibited a marked expression of CLDN18.2. These findings underline the need to perform a clinical study evaluating the efficacy of anti-CLDN18.2 therapy in patients suffering from CCA.

Claudin 18.2 (CLDN18.2) is a promising target for targeted therapies in gastric cancer (GC). This study investigated the prevalence of CLDN18.2 expression in patients with stages II-IV GC or gastroesophageal junction (GEJ) adenocarcinoma and its correlation with clinicopathologic features and other crucial GC biomarkers.

We enrolled 1000 patients diagnosed with stages II-IV GC after surgical treatment. Immunohistochemistry for CLDN18 (43-14A clone), PD-L1 (22C3 pharmDx), HER2, and FGFR2 was performed. CLDN18.2 positivity was defined as moderate-to-strong (2+/3+) membranous staining in ≥75% of tumor cells. CLDN18.2 expression was compared with biomarker expression, Epstein-Barr virus (EBV) association and microsatellite instability status, and clinicopathologic features.

CLDN18.2 was positive in 34.4% of the patients. CLDN18.2 positivity was significantly higher in the middle and upper thirds than in the lower third gastric location (P < .001), but there was no correlation with age, sex, or stage (P > .05). CLDN18.2 positivity was rare (2.8%) in mucinous adenocarcinoma but frequent (90.9%) in a majority of gastric carcinomas with lymphoid stroma. CLDN18.2 positivity was higher in EBV-associated (P < .001) and PD-L1-positive (PD-L1 CPS ≥ 5) GC (P = .014) but lower in HER2 positive GC (P = .005). CLDN18.2 positivity was not significantly associated with overall survival and disease-free survival.

This study provides a comprehensive evaluation of CLDN18.2 status and its correlation with the clinicopathologic characteristics of patients with stages II-IV GC in Korea and with crucial biomarkers. It may be valuable for guiding future drug development, expanding treatment options, and ultimately improving patient outcomes in GC.

The treatment of metastasized gastroesophageal adenocarcinoma largely depends on molecular profiling based on immunohistochemical procedures. Therefore, the examination of HER2, PD-L1, and dMMR/MSI is recommended by the majority of clinical practice guidelines, as positive expression leads to different treatment approaches. Data from large phase-III trials and consequent approvals in various countries enable physicians to offer their patients several therapy options including immunotherapy, targeted therapy, or both combined with chemotherapy. The introduction of novel therapeutic targets such as CLDN18.2 leads to a more complex decision-making process as a significant number of patients show positive results for the co-expression of other biomarkers besides CLDN18.2. The aim of this review is to summarize the current biomarker landscape of patients with metastatic gastroesophageal tumors, its direct clinical impact on daily decision-making, and to evaluate current findings on biomarker co-expression. Furthermore, possible treatment strategies with multiple biomarker expression are discussed.

Small bowel adenocarcinoma (SBA) is a rare malignancy with few established chemotherapy options and a dismal prognosis. We investigated the expression of claudin 18.2, nectin-4, human epidermal growth factor receptor 3 (HER3), and programmed death-ligand 1 (PD-L1) in SBA to identify potential antibody drug targets and analyzed associated clinicopathological features and prognosis.

We retrospectively reviewed patients diagnosed with SBA who underwent adjuvant or palliative chemotherapy at our hospital between July 2010 and July 2023. Pathological samples were immunohistochemically stained for claudin 18.2, nectin-4, HER3, and PD-L1. Overall survival (OS) was assessed in patients receiving palliative chemotherapy to examine its association with the expression of each protein, excluding those with microsatellite instability-high who were treated with immunotherapy.

Pathological samples and clinical data were available for 51 patients. The primary lesion was in the duodenum in 49% of these patients and in the jejunum or ileum in 51%. Positive rates for claudin 18.2, nectin-4, and HER3 were 35%, 82%, and 88%, respectively. All cases expressed at least one of the proteins, and 25% expressed all three proteins. The PD-L1 combined positive score (CPS) was <1, 1-5, and ≥5 in 33%, 32%, and 35%, respectively; nectin-4-positive samples showed higher CPS. Neither claudin 18.2 nor HER3 positivity was associated with OS. However, nectin-4 positivity was associated with significantly shorter OS [12.6 versus 43.2 months, hazard ratio (HR) 5.12, P = 0.006]. Similarly, PD-L1 CPS ≥5 was associated with shorter OS relative to CPS <5 (9.7 versus 18.0 months, HR 2.60, P = 0.028). Multivariate analysis identified nectin-4 positivity (HR 4.55, P = 0.020) as an independent adverse prognostic factor for OS.

Claudin 18.2, nectin-4, and HER3 are potential therapeutic targets in SBA, and nectin-4 positivity is independently associated with an unfavorable prognosis. These proteins may represent new therapeutic targets for SBA.

Claudin-18 isoform 2 (CLDN18.2) is expressed in multiple cancers and is a promising target for antitumor therapy. However, there is limited knowledge regarding the prevalence and characteristics of CLDN18.2-positive colorectal cancer (CRC).

To determine the clinicopathological and molecular features of patients with CLDN18.2-positive CRC.

Single-center retrospective study.

A total of 805 patients who underwent surgical resection for pathological stage I-III CRC at the National Cancer Center Hospital (Tokyo, Japan) between 1997 and 2019 were identified. Expression of CLDN18.2 was evaluated by immunohistochemistry. The association of CLDN18.2 expression with clinicopathological features and treatment outcomes was assessed. The cutoff for CLDN18.2 positivity was defined as ⩾1%.

Among these patients, 17 (2.1%) had CLDN18.2-positive CRC. Right-sided CRC was significantly more common in patients who were CLDN18.2 positive than in those who were CLDN18.2 negative (76.5% vs 28.3%, p < 0.0001), as was mucinous or poorly differentiated adenocarcinoma (17.6% vs 3.0%; 17.6% vs 2.2%, p < 0.0001), T3-4 disease (100% vs 84.3%, p = 0.075), lymphatic invasion (64.7% vs 24.2%, p < 0.0001), BRAF V600E mutation (29.4% vs 4.1%, p < 0.0001), and deficient mismatch repair (MMR) status (47.1% vs 10.0%, p < 0.0001). Multivariate analysis did not identify CLDN18.2 expression status to be an independent predictor of relapse-free survival (RFS) or overall survival (OS).

Approximately 2% of all CRC cases in this study were CLDN18.2 positive and had unfavorable features (e.g., mucinous or poorly differentiated adenocarcinoma, T3-4 disease, lymphatic invasion, BRAF V600E mutation) and deficient MMR status. CLDN18.2 positivity did not have a significant impact on RFS or OS.

Gastric cancer is common globally and has a generally poor prognosis with a low 5-year survival rate. Targeted therapies and immunotherapies have improved the treatment landscape, providing more options for efficacious treatment. The use of these therapies requires predictive biomarker testing to identify patients who can benefit from their use. New therapies on the horizon, such as CLDN18.2 monoclonal antibody therapy, require laboratories to implement new biomarker tests. A multidisciplinary pan-Canadian expert working group was convened to develop guidance for pathologists and oncologists on the implementation of CLDN18.2 IHC testing for gastric and gastroesophageal junction (G/GEJ) adenocarcinoma in Canada, as well as general recommendations to optimize predictive biomarker testing in G/GEJ adenocarcinoma. The expert working group recommendations highlight the importance of reflex testing for HER2, MMR and/or MSI, CLDN18, and PD-L1 in all patients at first diagnosis of G/GEJ adenocarcinoma. Testing for NTRK fusions may also be included in reflex testing or requested by the treating clinician when third-line therapy is being considered. The expert working group also made recommendations for pre-analytic, analytic, and post-analytic considerations for predictive biomarker testing in G/GEJ adenocarcinoma. Implementation of these recommendations will provide medical oncologists with accurate, timely biomarker results to use for treatment decision-making.

Invasive micropapillary carcinoma of the breast is characterized by clusters of cells presenting with inverted polarity. Although the apico-basal polarity is a fundamental property of the epithelium, the biological alterations leading to the inside-out pattern observed in invasive micropapillary carcinoma (IMPC) remain mostly unknown. The regulation of tight junctions in polarity formation and maintenance is acknowledged. By using immunohistochemistry, we have analysed claudin-1, -3, -4, and -7 tight junction proteins expression and their prognostic value on IMPCs and compared them to invasive breast carcinomas of no special type (IBC-NST) tumors. Our cohort consisted of 37 IMPCs, 36 IBC-NST and 9 mixed IMPC/IBC-NST tumors. Two scoring systems were used to quantify protein expression: a 4-tier scoring system and the H-score method. Distant metastasis free survival (DMFS) intervals and overal survival (OS) data were used for prognosis evaluation. The analysed samples were characterized mainly by low or no claudin-1 expression whereas claudins-3, -4 and -7 showed variable positivity. We have found no significant differences in claudin-3 and -4 protein expression between IMPC and IBC-NST groups with either scoring methods, however high claudin-7 expression was found in significantly more IMPCs than IBC-NST tumors according to the H-score system (p = 0.02). The 4-tier scoring method revealed association of claudin-7 expression with molecular tumor subtypes (p = 0.001). IMPC and IBC-NST tumors did not show difference in DMFS (p = 0.70). In the analysis of pure IMPC and IBC-NST tumors, positive/high claudin-4 protein expression was significantly associated with shorter DMFS (p = 0.02/p = 0.008, respectively according to the two scoring methods). Claudin-3 and claudin-7 expression showed no association with DMFS or OS. Changes in epithelial polarity seem not to be related to claudin-1, -3, and -4 expression. Increased claudin-4 expression may have a role in breast cancer progression.

Gastric cancer (GC) is a major global cause of cancer mortality, with a median overall survival of just 12 months. CLDN18.2, a specific isoform of Claudin18 normally expressed in the gastric mucosa, has emerged as a potential therapeutic target and prognostic biomarker due to its exposure on the surface of tumor cells following malignant transformation. This exposure allows CLDN18.2's extracellular loops to bind monoclonal antibodies, presenting new opportunities for targeted therapy and improved prognostic assessment.

A comprehensive search of PubMed, EMBASE, Cochrane Library, and Web of Science databases was conducted for studies that addressed the correlation of CLDN18.2 with: (1) Progression-free survival (PFS) and (2) Overall Survival (OS). Hazard ratio (HR) and odds ratio (OR) with 95% confidence intervals (CIs) were calculated using a fixed-effects model. Heterogeneity was examined with I2 statistics. P values of ≤ 0.05 were considered statistically significant. Statistical analyses were performed using RStudio, version 4.2.3.

A total of 15 studies encompassing a total of 4,085 patients were included. There were 2,691 (65.8%) male and 1,394 (34.2%) female patients. In the histologic GC analysis, there were 1,582 (38.7%) patients that had intestinal type and 1,280 (31.3%) with diffuse type. Patients with CLDN18.2 negative status exhibited a non-significant trend towards prolonged PFS (HR: 1.25; 95% CI: 0.98-1.61; p = 0.07; I2 = 18%) and a significant prolonged OS (HR: 1.20; 95% CI: 1.07-1.34; p < 0.01; I2 = 37%) when compared to CLDN18.2-positive patients.

Our findings establish CLDN18.2 as a robust negative prognostic indicator for overall survival in GC patients. While its impact on PFS was not statistically significant, the association with OS suggests CLDN18.2 may serve as a marker for complex biological processes underlying tumor advancement.

This study aimed to investigate the prevalence of claudin 18.2 (CLDN18.2) positivity, with a particular focus on intratumoral heterogeneity, and its association with clinicopathological features in metastatic or unresectable gastric cancer (GC).

We investigated 400 patients who received systemic chemotherapy for unresectable, metastatic, or recurrent GC. Immunohistochemistry for CLDN18 (43-14A), human epidermal growth factor receptor 2 (HER2), programmed death-ligand 1 (PD-L1), and fibroblast growth factor receptor 2, as well as HER2 silver in situ hybridization (ISH), Epstein-Barr virus (EBV) ISH, and microsatellite instability testing were carried out. CD3+, CD8+, CD4+, and Foxp3-positive immune cell densities were calculated using digital image analysis.

In GC cases with any CLDN18.2 expression, more than half of the cases (61.3%) showed different expression results between four different tissue microarray (TMA) cores. When comparing CLDN18.2 status between whole tissue sections and the combined results from the four TMA cores, discrepancies were observed in only 2 out of 85 GC cases (2.4%), with 1 false positive and 1 false negative. After considering intratumoral heterogeneity, a CLDN18.2 positivity rate of 31.3% was observed among the 400 GC patients. CLDN18.2 positivity was rare in GCs located in the antrum (or lower third) and in HER2-positive cases but was common in EBV-positive GCs (P < 0.05). No differences in overall survival (OS) were observed according to CLDN18.2 positivity (P = 0.116). Additionally, there was no association between OS and CLDN18.2 positivity in patients treated with fluoropyrimidine plus platinum, chemotherapy plus trastuzumab, paclitaxel with or without ramucirumab, and immuno-oncologic agents. CLDN18.2-positive/PD-L1-high GCs showed statistically significantly longer OS than others (P = 0.025) and higher CD8+ T-cell densities in both the tumor center and periphery (P < 0.001).

Characterizing unresectable, metastatic, or recurrent GC with positive CLDN18.2 expression and evaluating intratumoral heterogeneity and prognostic implications of various therapeutics help advance treatment strategies and develop new therapies for patients with GC.

Claudin18.2 has been established as a putative therapeutic target in human solid malignancies. The aim of this study is to determine claudin18.2 expression as a clinicopathological and prognostic factor in human solid tumors through a systematic review and meta-analysis. Articles were systematically reviewed for studies that included the correlation between claudin18.2 expression and clinicopathological features and prognosis in solid tumors. Meta-analysis was conducted to estimate either odds ratio and 95% confidence intervals (CIs) of clinicopathological factors or hazard ratio and 95% CIs of survival outcomes for claudin18.2 expression in all available solid tumors.

21 studies including 5,331 patients were identified. Overall proportion of claudin18.2 positivity was 29.7%. Analyses of clinicopathological features demonstrated that claudin18.2 positivity correlated with male predominance, lower T stage, more frequent MUC5AC positivity when all primary tumors included. In subgroup analysis, gastric cancer showed significant correlation between high claudin18.2 expression and frequent EBV infection, male predominance and lower T stage. In lung cancer, claudin18.2 expression was associated with favorable overall survival. However, analyses of survival outcomes in all solid tumors showed that claudin18.2 expression was not associated with overall survival and pooled disease-free survival, tumor-specific survival, progression-free survival and relapse-free survival.

Our study emphasizes evaluation of claudin18.2 expression as a potential prognostic factor in lung adenocarcinoma and further exploration in other solid tumors as well.

https://www.crd.york.ac.uk/prospero/, identifier CRD42023468651.

Background: The roles of Forkhead box N1 (FOXN1) in lung squamous cell carcinoma (LUSC) remains elusive. This study was focused on assessing the expression levels of FOXN1 in LUSC and exploring its potential clinical implications. Methods: Utilizing a range of databases, this study conducted an analysis of the FOXN1 gene's expression levels, comparing LUSC samples with those from normal lung tissues. The expression levels of FOXN1 in primary LUSC and corresponding normal lung tissues were assessed using immunohistochemistry (IHC). Histoscore was used to evaluate the staining degree. χ2 test and Fisher's exact test were employed to assess the association between categorical variables that do not possess an ordinal nature. Multivariate survival analysis was conducted using the Kaplan-Meier method, the Wilcoxon test, and the Cox proportional hazards model. Results: In contrast to normal lung tissues, the expression of the FOXN1 gene was found to be significantly elevated in LUSC tissues (P < 0.01). And FOXN1 was expressed in 79 (98.8%) evaluated LUSC tissues, most of which showed compositive IHC-staining intensity, presenting heterogeneously expression. 69 (87.3%) cases were characterized for strong immunostaining intensity, 70 (87.5%) cases showed moderate intensity, and 66 (82.5%) cases presented weak intensity. Only one sample of normal lung tissue, which represents 10% of the total, exhibited weak immunostaining exclusively (P < 0.05). Additionally, the expression of FOXN1 was found to have a significant correlation with the grading of LUSC, the presence of lymph node and distant metastases, the stage of the disease, and the survival outcomes (P < 0.05). Conclusion: The expression of FOXN1 is frequently increased in LUSC, and the patients with high FOXN1 expression have a poorer survival outcome. FOXN1 can be a novel biomarker and prognostic indicator for LUSC patients.

Claudin-18.2 (CLDN18.2) expression evaluated by immunohistochemistry is a new biomarker for gastric and gastroesophageal junction adenocarcinomas that will soon have market authorization for implementation into routine clinical practice. Despite successful testing in the setting of clinical trials, no specific practical testing guidelines have been proposed. Several preanalytical and analytical variables may interfere with adequate CLDN18.2 staining interpretation; thus, this article provides practical guidance on CLDN18.2 testing and scoring in gastric and gastroesophageal junction adenocarcinomas to identify patients who may respond to targeted therapy with monoclonal antibodies directed against CLDN18.2. Based on available data, moderate to strong (2+/3+) membrane staining in ≥75% of adenocarcinoma cells is the proposed cutoff for clinical use of monoclonal antibody anti-CLDN18.2 (zolbetuximab).

The 24 claudin (CLDN) genes in the human genome encode 26 representative CLDN family proteins. CLDNs are tetraspan‑transmembrane proteins at tight junctions. Because several CLDN isoforms, such as CLDN6 and CLDN18.2, are specifically upregulated in human cancer, CLDN‑targeting monoclonal antibodies (mAbs), antibody‑drug conjugates (ADCs), bispecific antibodies (bsAbs) and chimeric antigen receptor (CAR) T cells have been developed. In the present review, CLDN1‑, 4‑, 6‑ and 18.2‑targeting investigational drugs in clinical trials are discussed. CLDN18.2‑directed therapy for patients with gastric and other types of cancer is the most advanced area in this field. The mouse/human chimeric anti‑CLDN18.2 mAb zolbetuximab has a single‑agent objective response rate (ORR) of 9%, and increases progression‑free and overall survival in combination with chemotherapy. The human/humanized anti‑CLDN18.2 mAb osemitamab, and ADCs AZD0901, IBI343 and LM‑302, with single‑agent ORRs of 28‑60%, have been tested in phase III clinical trials. In addition, bsAbs, CAR T cells and their derivatives targeting CLDN4, 6 or 18.2 are in phase I and/or II clinical trials. AZD0901, IBI343, zolbetuximab and the anti‑CLDN1 mAb ALE.C04 have been granted fast track designation or priority review designation by the US Food and Drug Administration.

Poorly cohesive carcinoma (PCC) is a distinct subtype of gastric cancer with limited therapeutic options. This study investigated claudin (CLDN) 18.2 expression status in PCCs using a 43-13 A clone.

We retrospectively collected 178 consecutive surgically resected stage Ⅱ-Ⅲ gastric cancer samples. Tissue microarray blocks were constructed for CLDN18.2 immunohistochemical staining. We studied CLDN18.2 expression and its association with clinicopathologic parameters.

CLDN18.2 positivity (defined by ≥ 75 % of tumor cells showing moderate to strong membranous positivity) was found in 34.8 % of the PCC cases (62/178). Approximately half of the CLDN18.2 positive PCCs demonstrated heterogeneous expression (51.6 %, 32/62). CLDN18.2 positivity was not associated with any clinicopathologic parameters examined. However, CLDN18.2 positivity tended to be more frequent in E-cadherin-positive PCCs (no loss of expression) than in E-cadherin-negative PCCs (loss of expression) (50 % vs. 27.7 %). The CLDN18.2 expression level, represented by the H-score, gradually decreased as the paraffin block storage time increased (P = 0.046). Overall survival and disease-free survival analyses showed no significant difference between CLDN18.2-positive and negative PCCs.

A significant portion of surgically resected PCC specimens showed CLDN18.2 positivity. Additionally, since the expression level of CLDN18.2 gradually decreases with increased paraffin block storage time, reflex testing can be considered at the time of the cancer diagnosis.

Hepatobiliary and pancreatic diseases are becoming increasingly common worldwide and associated cancers are prone to recurrence and metastasis. For a more accurate treatment, new therapeutic strategies are urgently needed. The claudins (CLDN) family comprises a class of membrane proteins that are the main components of tight junctions, and are essential for forming intercellular barriers and maintaining cellular polarity. In mammals, the claudin family contains at least 27 transmembrane proteins and plays a major role in mediating cell adhesion and paracellular permeability. Multiple claudin proteins are altered in various cancers, including gastric cancer (GC), esophageal cancer (EC), hepatocellular carcinoma (HCC), pancreatic cancer (PC), colorectal cancer (CRC) and breast cancer (BC). An increasing number of studies have shown that claudins are closely associated with the occurrence and development of hepatobiliary and pancreatic diseases. Interestingly, claudin proteins exhibit different effects on cancer progression in different tumor tissues, including tumor suppression and promotion. In addition, various claudin proteins are currently being studied as potential diagnostic and therapeutic targets, including claudin-3, claudin-4, claudin-18.2, etc. In this article, the functional phenotype, molecular mechanism, and targeted application of the claudin family in hepatobiliary and pancreatic diseases are reviewed, with an emphasis on claudin-1, claudin-4, claudin-7 and claudin-18.2, and the current situation and future prospects are proposed.

Claudin18.2 (CLDN18.2) has emerged as a significant target in the treatment of advanced gastric cancer. The screening of patients positive for CLDN18.2 is crucial for the effective application of targeted therapies specific to CLND18.2. In this study, we developed a novel nanobody-based probe, [99mTc]Tc-PHG102, for use in nuclear medicine. We analyzed its radiochemical yield and stability to ensure accurate probe characterization. Additionally, we assessed the probe's affinity and specificity toward the CLDN18.2 target and evaluated its efficacy in the BGC82318.2 xenograft model for SPECT/CT imaging of gastric cancer. The binding of [99mTc]Tc-PHG102 to HEK-293T18.2 and BGC82318.2 cells was notably higher than its binding to HEK-293T18.1, HEK-293T, and BGC823 cells, with bound values of 12.87 ± 1.46%, 6.16 ± 0.34%, 1.25 ± 0.22%, 1.14 ± 0.26%, and 1.32 ± 0.07% AD, respectively. The binding ability of [99mTc]Tc-PHG102 was significantly different between CLDN18.2-positive and negative cells (P < 0.001). Imaging results demonstrated a time-dependent tumor accumulation of the radiotracer. Notably, at 0.5 h postinjection, rapid accumulation was observed with an average tumor uptake of 4.63 ± 0.81% ID/cc (n = 3), resulting in clear tumor visualization. By 1 h postinjection, as [99mTc]Tc-PHG102 was rapidly metabolized, a decrease in uptake by other organs was noted. Preliminary clinical imaging trials further confirmed the safety and effectiveness of the probe, indicating specificity for lesions expressing CLDN18.2 in gastric cancer and favorable in vivo metabolic properties. In conclusion, the nanobody-based probe [99mTc]Tc-PHG102 proves to be a safe and effective tool for detecting CLDN18.2 expression levels in gastric cancer tumors and for screening CLDN18.2-positive patients.

Claudin 18.2 has emerged as a viable therapeutic target in gastric cancer (GC), but little is known about the heterogeneity of its expression in GC. This study investigated the heterogeneity of claudin 18.2 expression in 166 patients with metastatic GC whose surgical or paired primary-metastatic specimens were available. The prevalence of claudin 18.2 positivity (moderate-to-strong expression in ≥ 75% by the 43-14A clone) was 47.0%. Claudin 18.2-positive tumors exhibited more frequent peritoneal metastasis and a lower incidence of hepatic and distant lymph node involvement. Survival outcomes were comparable between patients with claudin 18.2-positive and -negative tumors. Intratumoral heterogeneity was noted in 38.5% of surgical specimens. Paired primary-metastatic site analysis revealed that 25.2% of patients had discordant results for claudin 18.2 positivity. Across different metastatic organ categories, peritoneal lesions showed the highest positivity rate (44.3%) and positive concordance rate (31.4%), whereas liver lesions had the lowest positivity rate (17.9%) and concordance rate (12.8%). In conclusion, claudin 18.2 expression exhibits intratumoral and intrapatient spatial heterogeneity in metastatic GC. Claudin 18.2 positivity is associated with more frequent peritoneal metastasis, and peritoneal lesions are more likely to have positively concordant claudin 18.2 results with the primary site than other metastatic sites.

Physiologically, claudin 18 splice variant 2 (CLDN18.2) expression is restricted to the gastric epithelium, but its expression has been detected in solid cancers. Zolbetuximab, a chimeric IgG1 antibody targeting CLDN18.2, has demonstrated promising effects in patients suffering from CLDN18.2-positive, HER2-negative locally advanced gastric cancer and is currently being studied further. To date, little is known about CLDN18.2 expression in other histological subtypes of tubo-ovarian carcinoma (TOC) and their matching metastases.Using a cohort of all histological TOC subtypes, we investigated the immunohistochemical (IHC) CLDN18.2 expression in both TOCs (n = 536), their matching metastatic tissue (n = 385) and in 93 metastases without primary. Tissue microarrays comprised both the tumor center and periphery. IHC positivity was defined as biomarker expression of ≥ 75% in tumor cells with moderate-to-strong membranous staining.Overall CLDN18.2 positivity was 4.1% (21/515) in the TOC centers and 3.6% (18/498) in their peripheries. In primaries of mucinous tubo-ovarian carcinoma (MTOC), CLDN18.2 positivity rates were 45% (18/40) and 36.6% (15/41), respectively. Positivity rates for the corresponding metastases were 33% (4/12, center) and 27% (3/11, periphery). The expression was relatively homogenous throughout all tumor sites. With no expression in 99.5% of nonmucinous tumors, CLDN18.2 positivity was almost exclusively seen in the mucinous subtype.In tubo-ovarian carcinoma, CLDN18.2 expression was, with rare exceptions, restricted to the mucinous subtype. Among them, 33% of metastasized MTOCs presented with CLDN18.2 positivity. Hence, CLDN18.2 might display a promising target for personalized therapy in patients with advanced MTOC.

Claudin18.2 is a tight junction protein, highly selective, generally expressed only in normal gastric mucosal epithelial cells, which can effectively maintain the polarity of epithelial and endothelial cells, thus effectively regulating the permeability and conductance of the paracellular pathway. Abnormal expression of Claudin18.2 can occur in various primary malignant tumors, especially gastrointestinal tumors, and even in metastatic foci. It regulates its expression by activating the aPKC/MAPK/AP-1 pathway, and therefore, the Claudin18.2 protein is a pan-cancer target expressed in primary and metastatic lesions in human cancer types. Zolbetuximab (IMAB362), an antibody specific for Claudin18.2, has been successfully tested in a phase III clinical trial, and the results of the study showed that combining Zolbetuximab with chemotherapy notably extends patients' survival and is expected to be a potential first-line treatment for patients with Claudin18.2(+)/HER-2(-) gastric cancer. Here, we systematically describe the biological properties and oncogenic effects of Claudin18.2, centering on its clinical-pathological aspects and the progress of drug studies in gastric cancer, which can help to further explore its clinical value.

Claudin 18.2, a tight-junction molecule predominantly found in the nonmalignant gastric epithelium, becomes accessible on the tumour cell surface during malignant transformation, thereby providing an appealing target for cancer therapy. Data from two phase III trials testing the anti-claudin 18.2 antibody zolbetuximab have established claudin 18.2-positive advanced-stage gastric cancers as an independent therapeutic subset that derives benefit from the addition of this agent to chemotherapy. This development has substantially increased the percentage of patients eligible for targeted therapy. Furthermore, newer treatments, such as high-affinity monoclonal antibodies, bispecific antibodies, chimeric antigen receptor T cells and antibody-drug conjugates capable of bystander killing effects, have shown considerable promise in patients with claudin 18.2-expressing gastric cancers. This new development has resulted from drug developers moving beyond traditional targets, such as driver gene alterations or growth factors. In this Review, we highlight the biological rationale and explore the clinical activity of therapies that target claudin 18.2 in patients with advanced-stage gastric cancer and explore the potential for expansion of claudin 18.2-targeted therapies to patients with other claudin 18.2-positive solid tumours.

Claudin 18.2-targeted therapy has shown significant efficacy in treating claudin 18.2-positive cancers. However, limited systematic studies have investigated characteristics of claudin 18.2 expression in neuroendocrine neoplasms (NENs).

Data and specimens from 403 cases of digestive NENs were retrospectively collected, and claudin 18.2 expression was detected using immunochemical staining.

Claudin 18.2 was positive in 19.6% (79/403) of the digestive NENs. The highest positive rate of claudin 18.2 was observed in gastric NENs (72/259, 27.8%), accounting for 91.1% (72/79) of all positive cases. The positivity rate was significantly higher in gastric NENs compared to pancreatic (2/78, 2.6%) or colorectal NENs (2/38, 5.3%; p < 0.05). For digestive NENs, claudin 18.2 positivity was significantly higher in neuroendocrine carcinomas (NECs) (37/144, 25.7%) than in neuroendocrine tumours (NETs; 14/160, 8.8%; p < 0.001), but no significant difference was found between gastric NECs (59/213, 27.7%) and gastric NETs (13/46, 28.3%; p > 0.05). The positivity was significantly higher in large-cell NECs (LCNECs; 28/79, 35.4%) and MiNEN (mixed neuroendocrine-non- neuroendocrine neoplasms)-LCNECs (23/66, 34.8%) compared to small-cell NECs (SCNECs; 9/65, 13.8%) and MiNEN-SCNECs (5/33, 15.2%; p < 0.05). Claudin 18.2 expression was more prevalent in gastric NENs than in pancreatic (12.5 ×; p = 0.001) and colorectal NENs (5.9 ×; p = 0.021). Claudin 18.2 staining was a useful method for identify the gastric origins of NETs, with a sensitivity of 28.3% and a specificity of 99.1%.

The expression characteristics of claudin 18.2 in NENs were characterized, which may provide a clinicopathological reference for targeted therapies in patients with NENs.

Claudin 18 isoform 2 (CLDN18.2) is an emerging biomarker and therapeutic target in gastric and gastroesophageal junction (G/GEJ) adenocarcinoma. This study aimed to obtain deeper understanding of CLDN18.2 positivity patterns, prognostic implications, and associations with various demographic, clinical, and molecular characteristics in G/GEJ adenocarcinoma.

Archived tumor tissue samples from 304 patients with G/GEJ adenocarcinoma in the United States were assessed for CLDN18.2 positivity by immunohistochemistry. CLDN18.2 positivity was defined as ≥50% or ≥75% of tumor cells with CLDN18 staining intensity ≥2+. CLDN18.2 positivity patterns were analyzed for association with prognosis and clinicopathologic/demographic characteristics. Where possible, CLDN18.2 positivity was analyzed for matched tissue samples to assess concordance between primary and metastatic tumors and concordance before and after chemotherapy.

The overall prevalence of CLDN18.2-positive tumors (with ≥75% cutoff) was 44.4% (n = 135 of 304). CLDN18.2-positive tumors had a prevalence of 51.4% (n = 91 of 177) in gastric and 34.6% (n = 44 of 127) in GEJ adenocarcinoma. With a ≥50% cutoff, the prevalence of CLDN18.2-positive tumors was 64.4% (n = 114 of 177) in gastric adenocarcinoma and 44.9% (n = 57 of 127) in GEJ adenocarcinoma. There was no association between overall survival and CLDN18.2 positivity using either threshold. Statistically significant associations were noted between CLDN18.2 positivity and sex, histologic type of G/GEJ adenocarcinoma, and adenocarcinoma subtype (≥75% cutoff), and metastasis site and tumor grade (≥50% cutoff). The overall concordance of CLDN18.2 positivity (≥75% cutoff) was 73% (27 of 37) for matched primary versus metastatic tumor samples and 74% (29 of 39) for matched samples before and after chemotherapy.

This study demonstrated that CLDN18.2 positivity did not correlate with survival in G/GEJ adenocarcinoma, consistent with published data. On the basis of matched sample analysis, CLDN18.2 appears to demonstrate >70% concordance as a biomarker. Observed correlations with certain patient/tumor characteristics warrant further study.

Claudins are a family of 27 proteins that have an important role in the formation of tight junctions. They also have an important function in ion exchange, cell mobility, and the epithelial-to-mesenchymal transition, the latter being very important in cancer invasion and metastasis. Therapeutic targeting of claudins has been investigated to improve cancer outcomes. Recent evidence shows improved outcomes when combining monoclonal antibodies against claudin 18.2 with chemotherapy for patients with gastroesophageal junction cancer. Currently, chimeric antigen receptor T-cells targeting claudin 18 are under investigation. In this review, we will discuss the major functions of claudins, their distribution in the normal as well as cancerous tissues, and their effect in cancer metastasis, with a special focus on the therapeutic targeting of claudins to improve cancer outcomes.

Claudin 18.2 (CLDN18.2) is a highly anticipated target for solid tumor therapy, especially in advanced gastric carcinoma and pancreatic carcinoma. The T cell engager targeting CLDN18.2 represents a compelling strategy for enhancing anti-cancer efficacy.

Based on the in-house screened anti-CLDN18.2 VHH, we have developed a novel tri-specific T cell engager targeting CLDN18.2 for gastric and pancreatic cancer immunotherapy. This tri-specific antibody was designed with binding to CLDN18.2, human serum albumin (HSA) and CD3 on T cells.

The DR30318 demonstrated binding affinity to CLDN18.2, HSA and CD3, and exhibited T cell-dependent cellular cytotoxicity (TDCC) activity in vitro. Pharmacokinetic analysis revealed a half-life of 22.2-28.6 h in rodents and 41.8 h in cynomolgus monkeys, respectively. The administration of DR30318 resulted in a slight increase in the levels of IL-6 and C-reactive protein (CRP) in cynomolgus monkeys. Furthermore, after incubation with human PBMCs and CLDN18.2 expressing cells, DR30318 induced TDCC activity and the production of interleukin-6 (IL-6) and interferon-gamma (IFN-γ). Notably, DR30318 demonstrated significant tumor suppression effects on gastric cancer xenograft models NUGC4/hCLDN18.2 and pancreatic cancer xenograft model BxPC3/hCLDN18.2 without affecting the body weight of mice.

Immunotherapeutic outcomes and clinical characteristics of claudin 18 isoform 2 positive (CLDN18.2-positive) gastric cancer (GC) vary in different clinical studies, making it difficult to optimize anti-CLDN18.2 therapy. We conducted a retrospective analysis to explore the association of CLDN18.2 expression with clinicopathological characteristics and immunotherapeutic outcomes in GC.

A total of 536 advanced GC patients from 2019 to 2021 in the CT041-CG4006 and CT041-ST-01 clinical trials were included in the analysis. CLDN18.2 expression on ≥40% of tumor cells (2+, 40%) and CLDN18.2 expression on ≥70% of tumor cells (2+, 70%) were considered the two levels of positively expressed GC. The clinicopathological characteristics and immunotherapy outcomes of GC patients were analyzed according to CLDN18.2 expression status.

CLDN18.2 was expressed in 57.6% (cut-off: 2+, 40%) and 48.9% (cut-off: 2+, 70%) of patients. Programmed death-ligand 1 (PD-L1) and CLDN18.2 were co-expressed in 19.8% [combined positive score (CPS)≥1, CLDN18.2 (cut-off: 2+, 40%)] and 17.2% [CPS≥5, CLDN18.2 (cut-off: 2+, 70%)] of patients. CLDN18.2 expression positively correlated with younger age, female sex, non-gastroesophageal junction (non-GEJ), and diffuse phenotype (P<0.001). HER2 and PD-L1 expression were significantly lower in CLDN18.2-positive GC (both P<0.05). Uterine adnexa metastasis (P<0.001) was more frequent and liver metastasis (P<0.001) was less common in CLDN18.2-positive GC. Overall survival and immunotherapy-related progression-free survival (irPFS) were inferior in the CLDN18.2-positive group.

CLDN18.2-positive GC is associated with poor prognosis and worse immunotherapeutic outcomes. The combination of anti-CLDN18.2 therapy, anti-PD-L1/PD-1 therapy, and chemotherapy for GC requires further investigation.

Claudin 18.2 (CLDN18.2), due to its highly selective expression in tumor cells, has made breakthrough progress in clinical research and is expected to be integrated into routine tumor diagnosis and treatment.

In this research, we obtained an scFv-Fc fusion protein (SF106) targeting CLDN18.2 through hybridoma technology. The scFv-Fc fusion protein was labeled with radioactive isotopes (124I and 177Lu) to generate the radio-probes. The targeting and specificity of the radio-probes were tested in cellular models, and its diagnostic and therapeutic potential was further evaluated in tumor-bearing models.

The molecular probes [124I]I-SF106 and [177Lu]Lu-DOTA-SF106 possess high radiochemical purity (RCP, 98.18 ± 0.93 % and 97.05 ± 1.1 %) and exhibit good stability in phosphate buffer saline and 5 % human serum albumin (92.44 ± 4.68 % and 91.03 ± 2.42 % at 120 h). [124I]I-SF106 uptake in cells expressing CLDN18.2 was well targeted and specific, and the dissociation constant was 17.74 nM [124I]I-SF106 micro-PET imaging showed that the maximum standardized uptake value (SUVmax) was significantly higher than CLDN18.2-negative tumors (1.83 ± 0.02 vs. 1.23 ± 0.04, p < 0.001). The maximum uptake was attained in tumors expressing CLDN18.2 at 48 h after injection. [124I]I-SF106 and [177Lu]Lu-DOTA-SF106 dosimetric study showed that the effective dose in humans complies with the medical safety standards required for their clinical application. The results of treatment experiments showed that 3 MBq of [177Lu]Lu-DOTA-SF106 in CLDN18.2-expressing tumor-bearing mice could significantly inhibit tumor growth.

These results indicate that radionuclide-labeled scFv-Fc molecular probes ([124I]I-SF106 and [177Lu]Lu-DOTA-SF106) provide a new possibility for the diagnosis and treatment of CLDN18.2-positive cancer patients in clinical practice.