ARPC1B contributes to colorectal cancer progression and is associated with programmed death-ligand 1 expression

Abstract

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer; however, the role and mechanism of ARPC1B in CRC remain unclear.

AIM

To investigate the role of ARPC1B and its biological behavior in CRC.

METHODS

Clinical CRC samples were collected for western blotting of ARPC1B and programmed death-ligand 1 (PD-L1) expression. ARPC1B expression was further verified using The Cancer Genome Atlas and the Human Protein Atlas databases. Its oncogenic role was evaluated using cell counting kit-8, transwell assays, and flow cytometry in HT29 and SW620 cell lines in vitro. A xenograft nude mice model was established to assess tumor progression in vivo. Co-immunoprecipitation (Co-IP) assays examined the association between ARPC1B and PD-L1.

RESULTS

ARPC1B was highly expressed in CRC samples compared with paracancerous or normal samples. ARPC1B knockdown suppressed CRC cell proliferation, migration, and invasion, while promoting apoptosis in vitro. In vivo, ARPC1B knockdown inhibited tumor growth and metastasis. Additionally, PD-L1 expression decreased following ARPC1B knockdown, and Co-IP assays indicated an association between ARPC1B and PD-L1 in the CRC cells. Functional rescue experiments further showed that PD-L1 overexpression partially restored the malignant phenotype impaired by ARPC1B knockdown.

CONCLUSION

Our findings indicate that ARPC1B functions as a tumor-promoting factor in CRC and is positively associated with PD-L1 expression. The above preliminarily supports the potential involvement of ARPC1B in PD-L1-related cancer progression, though investigations into the molecular mechanisms are required.

Key Words: Colorectal cancer; ARPC1B; Programmed death-ligand 1; Biology; Co-immunoprecipitation

Core Tip: ARPC1B promotes colorectal cancer proliferation and metastasis and is associated with programmed death-ligand 1 (PD-L1) expression. Suppressed tumor growth and pulmonary metastasis are observed after knocking down ARPC1B expression. This study functionally links ARPC1B to PD-L1-associated aggressive biological behaviors.

INTRODUCTION

Being the third high-incidence tumor, colorectal cancer (CRC) ranks second in terms of cancer-related mortality[1,2]. CRC significantly threatens public health in China by its new onset and deaths in a greater number of cases annually[3-5]. To lower CRC incidence and mortality, efforts can be made from the perspectives of public awareness enhancement and screening popularization to make early diagnosis possible. Programmed death-ligand 1 (PD-L1), a molecule implicated in immune checkpoint signaling, plays an essential part in CRC immune evasion[6]. When the tumor cell-expressing PD-L1 binds to PD-1 receptors on T cell surfaces, it suppresses T-cell activation and proliferation, triggers apoptosis, and creates conditions for tumor immune evasion[7]. In CRC, PD-L1 expression is shown to be linked to therapeutic effectiveness, patient outcomes[8], microsatellite instability (MSI)[9], and the tumor immune microenvironment[10]. Also, it participates in CRC carcinogenesis and deterioration, while exerting an effect on therapeutic planning. However, further clarification of its regulatory role in CRC is required.

Being an Arp2/3 complex subunit, ARPC1B is an essential cytoskeletal remodeling gene[11]. By modulating actin filament polymerization and branching, it influences cell morphology, motility, and division[11,12]. In multiple cancers, like prostate and ovarian cancers[13,14] as well as glioma[15], ARPC1B dysregulation has been reported. Furthermore, research has revealed the presence of ARPC1B mutations or dysregulation in immunodeficiency-71 with inflammatory manifestations, congenital platelet abnormalities, and combined T- and B-cell immunodeficiencies[16]. ARPC1B has also been proposed as a candidate biomarker or therapeutic target, given its correlation with cancer severity and prognosis. In the CRC context, however, its specific role needs to be defined.

In this study, how ARPC1B functions in CRC and correlates with PD-L1 was investigated. Clinical CRC samples were analyzed for ARPC1B and PD-L1 expression. In vitro and in vivo evaluations were further made to assess ARPC1B’s oncogenic role. Correlation analysis used co-immunoprecipitation (Co-IP) assays. The ultimate goal is to furnish a potential biomarker for CRC.

MATERIALS AND METHODS

Data acquisition

We acquired ARPC1B messenger RNA (mRNA) expression from the colon adenocarcinoma (COAD) and rectum adenocarcinoma (READ) datasets in The Cancer Genome Atlas (TCGA) database and conducted further analysis using the GEPIA website. As to its protein expression measured via immunochemistry (IHC), the data were retrieved from the Human Protein Atlas database.

Samples collection

We collected paired cancerous tissue samples and their adjacent normal counterparts from five CRC patients undergoing treatment at The Second Affiliated Hospital of Fujian Medical University. The Declaration of Helsinki guidelines were followed throughout, and ethics committee approval was secured from The Second Affiliated Hospital of Fujian Medical University Hospital. The specimens were cryopreserved (-80 °C) until further analysis.

Western blotting

Following total protein isolation from cancerous and adjacent non-cancerous tissues with a radio immunoprecipitation assay (RIPA) lysis buffer (Meilunbio, China), protein concentration determination was conducted using the bicinchoninic acid assay. The optimal protein loading concentration was determined to be 45 μg/10 μL. Proteins were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (80 V for 30 minutes, followed by 120 V for 60 minutes) and transferred to polyvinylidene difluoride membranes using a semi-dry transfer apparatus. Then came tris buffered saline-based membrane rinsing and a 2-hour room-temperature incubation in a blocking solution with gentle shaking. A culture with primary antibodies, including PD-L1 (Abcam, ab205921, 1:5000, 30-60 kDa), ARPC1B (Abcam, ab99314, 1:8000, 41 kDa), and β-actin (Proteintech, 81115-1-RR, 1:12000, 42 kDa), was then carried out. The bands of interest were immersed in developing solution for > 30 seconds, placed in an imaging device for photography and development, and the results were analyzed using ImageJ.

Cell culture and transfection

CRC cell lines HT29 and SW620 were cultured in 89% Dulbecco’s Modified Eagle Medium supplemented with 10% fetal bovine serum and 1% penicillin/streptomycin solution at 37 °C with 5% carbon dioxide (CO₂) in a humidified incubator. Cells were passaged using 0.25% trypsin. For transfection, negative control (NC) and ARPC1B short hairpin RNA (shRNA) plasmids (Sangon, Shanghai, China) were transfected using Lipofectamine 3000 according to the manufacturer’s instructions. Cells were transfected for 48 hours. The shRNA sequences were: ARPC1B-shRNA1: 5’-GCGAGACCCTTTCTCTATTAA-3’; ARPC1B-shRNA2: 5’-GCCAGACTCCGTCTCTAAATA-3’; ARPC1B-shRNA3: 5’-GTCAGGCGCTGACAGTATAAA-3’; NC-shRNA: 5’-ATAAAAGTACACGAGCAAGAA-3’.

Quantitative real time polymerase chain reaction

Total RNA was extracted from HT29 and SW620 cells using RNAiso Plus (TaKaRa). First-strand complementary DNA (cDNA) was synthesized from 1 μg total RNA in a 20 μL reaction using a cDNA synthesis kit (Novoprotein, E047-01A). Quantitative real time polymerase chain reaction (qRT-PCR) amplification of cDNA samples was performed in triplicate using the SYBR qPCR kits following the manufacturer’s protocols. The qRT-PCR cycling conditions were as follows: 95 °C for 1 minute, followed by 40 cycles of denaturation at 95 °C for 35 seconds and annealing at 60 °C for 35 seconds. Relative expression was determined using the 2^-ΔΔCT method with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as the internal control. Fluorescent signals were measured after each primer-annealing step at 60 °C. The primer sequences for ARPC1B were: ARPC1B-forward (F): 5’-GTTATTTCGAGCAGGAGAATGAC-3’; ARPC1B-reverse (R): 5’-GTAGGCTGAAAAGATCCGACA-3’; GAPDH-F: 5’-ATGGGGAAGGTGAAGGTCG-3’; GAPDH-R: 5’-TCGGGGTCATTGATGGCAACAATA-3’.

Cell counting kit-8 assay

Cells transfected with ARPC1B-shRNA (sh-ARPC1B) or control (1 × 10⁴ cells/well) were seeded into 96-well plates and incubated at 37 °C with 5% CO₂. Cell counting kit-8 (CCK8) assays (Meilune, China) were performed every 24 hours for three days. After incubation with 10 μL reagent for 2 hours, absorbance at 450 nm was measured using a spectrophotometer.

Apoptosis analysis using flow cytometry

HT29 and SW620 cells were seeded in 6-well plates and transfected with sh-ARPC1B or NC for 48 hours. Cells were collected using ethylenediaminetetraacetic acid-free trypsin, washed twice with cold phosphate-buffered saline, and resuspended in binding buffer (1 × 10⁶ cells/mL). A 100 μL aliquot was stained with Annexin V-fluorescein isothiocyanate (5 μL) and propidium iodide (5 μL) for 15 minutes at room temperature in the dark. After incubation, 400 μL of 1 × binding buffer was added to each tube. Importantly, cells were not fixed; they were analyzed immediately using a BD FACSAria^TM III flow cytometer (BD Biosciences) within 1 hour. Data were processed using FlowJo (version 10.8). Each experiment repeated three times.

Xenograft nude mice model

This study used sh-ARPC1B and control vectors ordered from Sangong Co., Ltd. (Shanghai, China) and BALB/c nude mice (male, 6 weeks of age) from Aniphe Biolaboratory Inc. The animals were randomized into four groups (n = 5) for subcutaneous injection of sh-ARPC1B or control HT29/SW620 cells. Tumor volume and weight measurements were conducted at three-day intervals. The animals inhaled CO₂ (30%-70% chamber volume per minute) for euthanasia three weeks later.

IHC staining

Following paraffin embedding, CRC specimens further underwent deparaffinization, rehydration, and overnight incubation at 4 °C with an anti-ARPC1B primary antibody. This was followed by a 60-minute section incubation with an horseradish peroxidase-conjugated secondary antibody, a 3-minute counterstaining process with hematoxylin, and immunostaining image acquisition.

Co-IP

HT29 and SW620 cells were lysed using mild RIPA buffer for 30 minutes. Dynabeads Protein G (50 μL; Life Technologies) were incubated with 3 μg antibody for 1 hour at room temperature, then combined with lysates and incubated overnight at 4 °C. Following incubation, the beads were washed thrice with lysis buffer, and bound proteins were analyzed via immunoblotting along with 10% input.

Statistical analysis

Statistical analyses were performed using SPSS 22.0. Experiments were conducted in triplicate. Data are expressed as means ± SD. Differences were assessed using student’s t-test, with P < 0.05 considered statistically significant.

RESULTS

ARPC1B is highly expressed in patients with CRC

To assess ARPC1B expression in CRC, we first analyzed public datasets and clinical samples. ARPC1B mRNA levels were upregulated in the CRC tissue samples compared with normal samples based on the TCGA database (Figure 1A). Immunohistochemistry further showed higher ARPC1B protein expression in CRC tissues than in normal tissues (Figure 1B). To further validate these findings, five paired CRC and adjacent paracancerous tissues were analyzed by western blotting. Both ARPC1B and PD-L1 were significantly upregulated in CRC tissue samples compared with paracancerous tissue samples (P < 0.05, Figure 1C and D). These results indicate that ARPC1B is highly expressed in CRC. Survival analysis using the Gene Set Cancer Analysis database showed that ARPC1B expression was negatively correlated with overall survival and disease-specific survival in READ (Figure 1E and F). Meanwhile, the ARPC1B copy number variation was significantly positively correlated with its mRNA expression in CRC (Figure 1G and H), suggesting a potential role in tumorigenesis and progression. Together, these data suggest that ARPC1B may function as an oncogene in CRC.

Figure 1 ARPC1B is highly-expressed in colorectal cancer patients. A: The relative messenger RNA (mRNA) expression level of ARPC1B in the colon adenocarcinoma (COAD) and rectum adenocarcinoma (READ) datasets of The Cancer Genome Atlas database. The red boxplot indicates the colorectal cancer (CRC) tumor, and grey boxplot indicates the normal samples; B: The immunohistochemistry results of ARPC1B in CRC tissue and normal tissue were obtained from The Human Protein Atlas database (https://www.proteinatlas.org); C: The relative protein expression level of ARPC1B and programmed death-ligand 1 in 5 pairs of CRC and paracancerous tissue was determined via western blot; D: The statistical analysis of western blot; E: The overall survival of ARPC1B expression in READ by Gene Set Cancer Analysis (GSCA) database; F: The disease-specific survival of ARPC1B expression in READ by GSCA database; G: Spearman correlation between ARPC1B copy number variation (CNV) and mRNA expression in COAD by GSCA database; H: Spearman correlation between ARPC1B CNV and mRNA expression in READ by GSAV database. ^aP < 0.05. ^bP < 0.01. COAD: Colon adenocarcinoma; READ: Rectum adenocarcinoma; CRC: Colorectal cancer; PD-L1: Programmed death-ligand 1; NC: Negative control; OS: Overall survival; DSS: Disease-specific survival; CNV: Copy number variation; mRNA: Messenger RNA; FDR: False discovery rate; RSEM: RNA-sequencing by expectation-maximization.

ARPC1B knockdown suppresses the malignant phenotype of CRC cells

Cellular experiments were performed to evaluate the oncogenic role of ARPC1B. The knockdown efficiency of ARPC1B-shRNA 1-3 in HT29 and SW620 cells is shown in Figure 2A, and ARPC1B-shRNA2 was selected for further experiments. The CCK8 assays showed that ARPC1B knockdown remarkably inhibited the proliferation of HT29 and SW620 cells (Figure 2B). Transwell assays showed reduced invasion in ARPC1B-knockdown cells compared with the NC group (Figure 2C). Furthermore, the HT29 and SW620 cells treated with sh-ARPC1B showed higher apoptosis rate than the NC group (Figure 2D). Collectively, these in vitro results support an oncogenic role for ARPC1B in CRC.

Figure 2 Knockdown of ARPC1B suppresses the malignant phenotype of colorectal cancer cell. A: The knockdown efficiency of ARPC1B-short hairpin RNA (shRNA) 1-3 in HT29 and SW620 cell lines; B: The proliferation of HT29 and SW620 cell lines treated or not treated with ARPC1B-shRNA (sh-ARPC1B) was detected via cell counting kit-8 assay; C: The invasion of HT29 and SW620 cell lines treated or not treated with sh-ARPC1B was detected via transwell assay; D: The apoptosis rate of HT29 and SW620 cell lines treated or not treated with sh-ARPC1B was detected via flow-cytometry assay. n = 3. scale bar = 100 μm. ^aP < 0.05. ^bP < 0.01. ^cP < 0.001. NC: Negative control; sh-ARPC1B: ARPC1B-short hairpin RNA; FITC: Fluorescein isothiocyanate; PI: Propidium iodide.

ARPC1B knockdown inhibits tumor growth and metastasis in xenograft nude mouse model

The oncogenic role of ARPC1B was further investigated in vivo using a xenograft nude mice model. As shown in Figure 3A and B, HT29 xenograft tumors were successfully established, and tumor weight and volume in the HT29-sh-ARPC1B group were significantly lower than those in the NC group (P < 0.001; Figure 3C and D). Similarly, SW620 xenograft models were also successfully established (Figure 3E and F), and tumor weight and volume were reduced in the SW620-sh-ARPC1B group compared with the NC group (P < 0.001; Figure 3G and H). In addition, lung metastasis of CRC induced by HT29 or SW620 cells was suppressed following ARPC1B knockdown (Figure 3I and J). Together, these in vivo findings further support the oncogenic function of ARPC1B in CRC.

Figure 3 Knockdown of ARPC1B inhibits tumor growth and metastasis in xenograft nude mice model. A: The image showed the HT29-xenograft nude mice model was successful established; B: The image showed the tumors obtained from nude mice model; C: The tumor weight of HT29-negative control (NC)-ARPC1B or HT29-ARPC1B-short hairpin RNA (shRNA) (sh-ARPC1B) xenograft nude mice models; D: The tumor volume of HT29-NC-ARPC1B or HT29-sh-ARPC1B xenograft nude mice models; E: The image showed the SW620-xenograft nude mice model was successful established; F: The image showed the tumors obtained from nude mice model; G: The tumor weight of SW620-NC-ARPC1B or SW620-sh-ARPC1B xenograft nude mice models; H: The tumor volume of SW620-NC-ARPC1B or SW620-sh-ARPC1B xenograft nude mice models (n = 5); I: The metastasis of colorectal cancer (CRC) induced by HT29 in nude mice was presented by bioluminescence and fluorescence imaging; J: The metastasis of CRC induced by SW620 in nude mice was presented by bioluminescence and fluorescence imaging (n = 3). ^cP < 0.001. NC: Negative control; sh-ARPC1B: ARPC1B-short hairpin RNA.

Association between ARPC1B expression and immune cell infiltration in CRC

Given the importance of immune cells in the immune microenvironment, as they can prognosis of patients with cancer[17]. How ARPC1B correlates with immune cell infiltration was analyzed using the TIMER database in this study (Figure 4). A strong association of ARPC1B expression with several immune cell types in both COAD and READ, like cluster of differentiation 4⁺ T and dendritic cells, as well as macrophages and neutrophils, was identified. This study further utilized the TCGA dataset to conduct a statistical investigation into the correlation of ARPC1B mRNA expression with MSI status and tumor mutational burden (TMB), so as to clarify the potential clinical relevance of ARPC1B to immunotherapy response. As shown in Supplementary Figure 1, ARPC1B expression differed insignificantly with MSI or TMB status in either COAD or READ (P > 0.05). These findings suggest that ARPC1B is not strongly associated with established predictive markers for PD-1/PD-L1 blockade response in CRC, and its role as an independent immunotherapy biomarker requires further investigation.

Figure 4 Correlations between ARPC1B expression and immune infiltration levels in colorectal cancer. CD: Cluster of differentiation; TPM: Transcripts per million; COAD: Colon adenocarcinoma; READ: Rectum adenocarcinoma.

ARPC1B is associated with PD-L1 expression and contributes to CRC progression

In the previous research, PD-L1 expression was increased in the CRC tissue samples compared with paracancerous tissue samples (Figure 1C). To further examine the correlation of ARPC1B and PD-L1, PD-L1 protein levels were assessed in the xenograft tumors. As shown in Figure 5A and B, ARPC1B knockdown led to a reduction in PD-L1 expression in the CRC tumor samples (P < 0.05), which was also supported by IHC analysis (Figure 5C and D). In addition, the Co-IP assays in HT29 and SW620 cells showed an association between ARPC1B combined to PD-L1, which was reduced following ARPC1B knockdown (Figure 5E and F). CCK8 results also showed that PD-L1 overexpression partially restored proliferation in ARPC1B-knockdown cells (Figure 6A). Similarly, Transwell assays indicated that PD-L1 overexpression partially reversed the reduced invasion caused by ARPC1B knockdown (Figure 6B and C). Collectively, these results indicate that ARPC1B contributes to CRC progression and is functionally associated with PD-L1 expression.

Figure 5 ARPC1B regulates programmed death-ligand 1 expression in colorectal cancer. A: The relative protein expression level of programmed death-ligand 1 (PD-L1) in HT29-negative control (NC)-ARPC1B or HT29-ARPC1B-short hairpin RNA (shRNA) (sh-ARPC1B) xenograft nude mice models; B: The relative protein expression level of PD-L1 in SW620-NC-ARPC1B or SW620-sh-ARPC1B xenograft nude mice models; C: The representative immunohistochemistry results of PD-L1 in HT29-NC-ARPC1B or HT29-sh-ARPC1B xenograft nude mice models; D: The representative immunohistochemistry results of PD-L1 in SW620-NC-ARPC1B or SW620-sh-ARPC1B xenograft nude mice models; E: The co-immunoprecipitation (Co-IP) experiments of ARPC1B and PD-L1 in HT29 cells; F: The Co-IP experiments of ARPC1B and PD-L1 in SW620 cells (n = 3). scale bar = 100 μm. ^cP < 0.001. NC: Negative control; sh-ARPC1B: ARPC1B-short hairpin RNA; PD-L1: Programmed death-ligand 1; IP: Immunoprecipitation; IB: Immunoblotting; IgG: Immunoglobulin G.

Figure 6 ARPC1B regulates programmed death-ligand 1 expression to promote colorectal cancer progression. A: Cell counting kit-8 assay showed the light absorption value at 450 nm after 48 hours of HT29 and SW620 cells proliferation; B and C: Transwell showed the invasion of HT29 and SW620 cells under negative control, ARPC1B-short hairpin RNA (sh-ARPC1B), programmed death-ligand 1 (PD-L1)-over expression and sh-ARPC1B + PD-L1-over expression condition (n = 3). scale bar = 100 μm. ^aP < 0.05. ^bP < 0.01. ^cP < 0.001. NC: Negative control; sh-ARPC1B: ARPC1B-short hairpin RNA; PD-L1: Programmed death-ligand 1; OE: Over expression; OD: Optical density.

DISCUSSION

In this study, ARPC1B was found to be highly expressed in CRC patient samples compared with paracancerous or normal tissue samples. ARPC1B knockdown suppressed the malignant phenotypes in CRC cells, including reduced proliferation, migration, and invasion, as well as increased apoptosis. Additionally, ARPC1B knockdown reduced tumor growth and metastasis in xenograft nude mice model. Together, these findings demonstrate that ARPC1B is upregulated in CRC and promotes malignant behaviors. Furthermore, we observed a positive association between ARPC1B and PD-L1 expression.

The Arp2/3 complex is evolutionarily conserved and, as a cytoskeletal protein, promotes actin network branching[18]. Dysregulated activation of the Arp2/3 complex has been associated with tumor progression[19]. ARPC1B, a regulatory subunit of this complex, plays a key role in its assembly and maintenance[11,20]. Previous studies have shown that ARPC1B mutations are linked to immune-related autosomal recessive syndromes, impaired T-cell migration and proliferation, and thrombocytopenia[21]. Additionally, ARPC1B expression correlates with the aggressive features in cancers such as melanoma[22], osteosarcoma[23], and oral squamous cell carcinoma[24]. However, its role in CRC has not been previously reported. In this study, ARPC1B knockdown suppressed CRC cell proliferation, migration, and invasion, while promoting apoptosis, and reduced tumor growth and metastasis in a xenograft nude mice model. These findings indicate, for the first time, that ARPC1B functions as an oncogene in CRC in vitro and in vivo models.

The binding of PD-1 and PD-L1 molecules leads to T-cell dysfunction and immune tolerance within the tumor microenvironment[25]. This interaction reduces T-cell activity and proliferation, impairing their ability to recognize and eliminate tumor cells[26], thereby facilitating tumor growth and metastasis[27]. High PD-L1 expression has been associated with poor prognosis in patients with CRC[28]. However, the regulatory mechanisms underlying PD-L1 expression in CRC remain unclear. PD-L1 expression is regulated by multiple factors, including gene amplification, DNA damage, oncogene and tumor suppressor gene mutations, transcriptional regulation, epigenetic modifications, and posttranslational modifications[29-31]. For example, MYC is an oncogenic factor that is overexpressed in various tumors and participates in PD-L1 regulation across various tumors[32], and PTEN loss increases PD-L1 protein levels[33]. Given the role of the Arp2/3 complex in cytoskeletal remodeling, it may affect immune cell behavior and indirectly affect PD-L1 expression or its interaction with PD-1[19]. Additionally, ARPC1B involvement in T-cell activation and function may intersect with PD-L1-mediated immunosuppression[34,35]. To the best of our knowledge, this is the first study to report an association between ARPC1B and PD-L1 expression in CRC. Although ARPC1B expression was not strongly associated with MSI status or TMB in our database analysis (Supplementary Figure 1), its positive correlation with PD-L1 and oncogenic role suggest potential indirect relevance to the tumor immune microenvironment. Future studies using immune-competent models and patient cohorts receiving immune checkpoint inhibitors are needed to determine whether ARPC1B could serve as a predictive or prognostic biomarker.

However, our study has several limitations. Although ARPC1B knockdown reduced PD-L1 expression and attenuated the malignant phenotypes of CRC cells, the current evidence is insufficient to establish direct molecular regulation. The Co-IP results indicate an association within a protein complex but do not confirm direct binding or transcriptional/posttranslational regulation. ARPC1B may indirectly affect PD-L1 expression through cytoskeletal remodeling, membrane protein trafficking/stability, or other tumor-related signaling pathways. Additionally, the clinical sample size is small and serves only as preliminary validation. the bioinformatic immune correlation analysis is observational and requires functional confirmation, including tumor immune cell coculture models, immune-related cytokine/effector assays, and validation in immune-competent in vivo models.

CONCLUSION

In conclusion, ARPC1B appears to function as a tumor-promoting factor in CRC and is positively associated with PD-L1 expression. While these findings support a functional link between ARPC1B and PDL1-related malignant phenotypes, they do not establish a direct molecular regulatory mechanism. Further mechanistic research, as well as investigations into the tumor microenvironment, is required to clarify this relationship.