Telomere and telomerase: Traditional tumor targets regain their applications for liver cancer diagnosis and prognosis

Abstract

In recent decades, telomeres and telomerase activity have been central to research on cellular aging, stem cell biology, and tumor progression. In our previous work, we developed several targeted therapeutic strategies that successfully suppress the growth of malignant tumors, including hepatocellular carcinoma, in both in vitro and in vivo models. Despite these advances, the clinical application of telomere-based biomarkers for cancer diagnosis and prognosis remains limited. In this context, El-Nakeep et al recently published a study in the World Journal of Gastroenterology, and which demonstrated that telomere length in peripheral leukocytes may serve as a liquid biopsy-based biomarker for the diagnosis and short-term prognostic assessment of hepatocellular carcinoma following loco-regional therapy. This work underscores a novel and clinically relevant application of telomere biology in the management of hepatocellular carcinoma. Thus, future studies should include larger clinical cohorts and extend investigations to additional tumor types to further validate the diagnostic and prognostic significance of telomere length. Moreover, continued exploration of telomerase and telomerase reverse transcriptase as therapeutic targets represents an important research direction, with the potential to integrate biomarker discovery with anticancer therapy development more closely.

Key Words: Hepatocellular carcinoma; Telomeres; Telomerase; Biomarker; Liquid biopsy

Core Tip: This editorial emphasizes the pivotal role of telomere biology in hepatocellular carcinoma, spanning fundamental molecular mechanisms and their clinical implications. It outlines the diagnostic and prognostic value of non-invasive liquid biopsy approaches based on telomere length assessment and TERT mutation analysis. Furthermore, the editorial discusses emerging therapeutic strategies, particularly telomerase-targeted immunotherapies, underscoring their potential to advance precision oncology in hepatocellular carcinoma and other malignancies.

This editorial refers to “Clinical utility of telomeres as diagnostic and short-term prognostic markers in loco-regional treatment of hepatocellular carcinoma” by El-Nakeep et al, 2025; https://dx.doi.org/10.3748/wjg.v32.i46.112530.

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INTRODUCTION

Liver cancer is the sixth most commonly diagnosed malignancy worldwide and the third leading cause of cancer-related mortality[1]. Hepatocellular carcinoma (HCC) represents the predominant histological subtype of liver cancer and constitutes a major global health burden, marked by high incidence and substantial mortality. Although significant advances have been made in surveillance strategies and imaging technologies, early detection of HCC remains a significant clinical challenge, contributing directly to poor patient outcomes. A key limitation is the suboptimal sensitivity of current surveillance approaches in high-risk populations. Abdominal ultrasound, the cornerstone of HCC surveillance, is highly operator-dependent and has limited sensitivity for early-stage lesions smaller than 2 cm, particularly in individuals with obesity or a nodular cirrhotic liver architecture[2]. Similarly, the commonly used serological marker alpha-fetoprotein (AFP) lacks adequate sensitivity and specificity, as approximately 30%-40% of early-stage HCC cases do not show elevated AFP levels[3]. For nodules detected during surveillance that remain indeterminate, a substantial “diagnostic gap” persists. Current international guidelines often require concordant findings across two imaging modalities for lesions measuring 1-2 cm, or histopathological confirmation via biopsy, both of which may delay definitive diagnosis and timely intervention. Liver biopsy, moreover, is invasive, carries risks such as bleeding and needle tract seeding, and is susceptible to sampling error due to intratumoral heterogeneity[4]. These limitations underscore the urgent need for more reliable and non-invasive biomarkers for HCC detection and risk stratification.

Telomeres are specialized nucleoprotein complexes located at the termini of eukaryotic chromosomes, consisting of repetitive DNA sequences (TTAGGG in humans) and associated shelterin proteins[5]. Their primary role is to preserve genomic integrity by preventing chromosomal degradation and end-to-end fusion events. Owing to the “end-replication problem”, telomeres progressively shorten with each round of somatic cell division, ultimately triggering cellular senescence or apoptosis and functioning as a fundamental mitotic clock of cellular aging[6]. Telomerase, a ribonucleoprotein reverse transcriptase, counterbalances telomere attrition by synthesizing telomeric repeats de novo. While telomerase activity is essential in stem cells and germ cells, it is repressed mainly in most adult somatic tissues. Reactivation of telomerase, however, is observed in approximately 90% of human malignancies, conferring unlimited replicative capacity and representing a defining hallmark of cancer[7,8]. Accordingly, telomeres and telomerase have emerged as central biological targets in oncologic research. Inherited defects in telomere maintenance lead to severe telomere biology disorders, such as dyskeratosis congenita, which are characterized by premature aging and multi-organ dysfunction[9]. Under physiological conditions, the liver demonstrates minimal telomerase activity. In the setting of chronic liver disease, persistent inflammation and repeated cycles of hepatocyte regeneration accelerate telomere shortening, promote chromosomal instability, and ultimately drive telomerase reactivation[10]. This distinctive biology presents compelling clinical opportunities. Therapeutic strategies include telomerase inhibition as an anticancer approach, as well as telomerase activation or gene-based interventions to ameliorate telomere-related degenerative disorders, although the latter necessitates rigorous safety evaluation due to potential oncogenic risks[8,11]. The central role of telomere dysfunction in hepatocarcinogenesis thus represents a promising yet underexplored avenue for improving HCC diagnosis and prognosis, an area now poised for renewed progress with the emergence of advanced analytical technologies.

This editorial aims to integrate recent advances in telomere and telomerase biology within the context of liver cancer, with particular emphasis on translating molecular insights into clinically meaningful diagnostic and prognostic tools. We further discuss the therapeutic relevance of targeting telomere-related pathways and consider their broader applicability across oncology, while highlighting developments specific to HCC.

TELOMERE DYNAMICS IN HEPATOCARCINOGENESIS: UPDATED MOLECULAR MECHANISMS

The progression from a normal hepatocyte to a malignant HCC cell is a multistep process in which telomere biology functions as a central molecular regulator. Chronic liver disease is characterized by persistent inflammation that leads to hepatocyte injury, cell death, and compensatory regeneration. Although the liver possesses substantial regenerative capacity[12], this reserve is progressively diminished in chronic liver disease, resulting in accelerated telomere attrition and a consequent limitation of regenerative potential. Telomere shortening is not merely a passive consequence of chronic injury; instead, it actively promotes inflammation and fibrogenesis, reinforcing a pro-carcinogenic microenvironment. Multiple studies have demonstrated that shortened telomeres in cirrhotic liver tissue constitute a strong independent risk factor for the subsequent development of HCC, representing a critical and often irreversible stage in disease progression[13].

In a recent issue of the World Journal of Gastroenterology, El-Nakeep et al[14] reported a prospective study. This investigation evaluated leukocyte telomere length (LTL) as a biomarker in a cohort of 60 Egyptian patients, including 30 individuals with cirrhosis and 30 with HCC. LTL did not differ significantly between the cirrhosis and HCC groups, nor did it change following loco-regional therapy. Within the HCC cohort, patients harboring larger tumors (≥ 5 cm) exhibited significantly shorter baseline LTL. Moreover, among this subgroup, a positive correlation was observed between longer LTL and increasing tumor size. Based on these observations, the authors proposed that LTL may hold prognostic value, particularly in advanced-stage HCC, while its diagnostic utility and role in monitoring treatment response appear limited.

These findings should be interpreted cautiously, given several methodological limitations. The relatively small sample size (n = 60) and the single-center design, confined to a specific regional population, limit both statistical power and generalizability. Therefore, the reported associations, especially those observed in patients with large tumors, require confirmation in larger, multicenter studies involving ethnically diverse cohorts to establish their robustness and broader clinical relevance.

The most compelling genetic evidence implicating telomerase in HCC is the high frequency of somatic mutations within the promoter region of the TERT gene. TERT encodes the catalytic subunit of telomerase, together with the telomerase RNA component. These promoter mutations are often among the earliest detectable genetic alterations in hepatocarcinogenesis, leading to their characterization as HCC-specific “gatekeeper” events[15]. Nault et al[16] reported that such mutations are prevalent in human HCC (59%), present in precancerous cirrhotic nodules (25%), and observed in hepatocellular adenomas undergoing malignant transformation (44%). TERT promoter mutations were not identified in non-neoplastic cirrhotic liver tissue. To date, TERT promoter mutations represent the earliest recurrent genetic events detected in cirrhotic preneoplastic lesions and rank among the most frequent molecular alterations in HCC[17].

This concept is further supported by a recent integrative genomic analysis of 1502 patients, which demonstrated that TERT alterations, including promoter mutations, copy number gains, structural variations, and viral integration events, occur in approximately 78.5% of HCC cases, with promoter mutations constituting the most common mechanism (57.8%). HCCs arising in livers with shortened telomeres, a defining feature of cirrhosis, showed a significant enrichment of TERT promoter mutations. This observation reinforces telomerase reactivation as a critical step in malignant transformation in the setting of chronic liver injury[10]. These findings support the notion that telomerase reactivation is a prerequisite for the progression of hepatocytes from cirrhosis to overt carcinoma.

Although TERT promoter mutations are the dominant mechanism driving telomerase reactivation in HCC, they are not the sole pathway. Alternative mechanisms include chromosomal amplification of the TERT locus[17], transcriptional activation mediated by viral oncoproteins such as those encoded by the hepatitis B virus[18], and dysregulation of upstream signaling pathways, including nuclear factor kappa-B[19] or Wnt/β-catenin[20], all of which can directly enhance TERT transcription.

An emerging area of research concerns the interplay between telomere biology and epigenetic regulation. Xie et al[21] reported that telomere methylation-related genes are closely associated with regulatory T cell and proliferative T cell subsets within the HCC tumor microenvironment. These telomere methylation-associated genes may influence HCC prognosis by affecting chromosomal stability and cell cycle regulation. However, aberrant telomere methylation, together with telomere shortening, can also promote genomic instability and contribute to tumor initiation[22]. As a result, the precise relationships among telomere methylation, telomere attrition, and the initiation, progression, and prognosis of liver cancer remain to be fully elucidated and warrant further investigation. Based on these considerations, we present a schematic illustration summarizing the core mechanisms of telomere biology across the multistage development of HCC (Figure 1).

Figure 1 The core mechanism of telomere biology in the multistep development of hepatocellular carcinoma[50]. Chronic liver injury leads to repeated hepatocyte death and regeneration, resulting in progressive telomere shortening, which ultimately exhausts the liver’s regenerative reserve and induces cirrhosis. In the setting of cirrhosis, genomic instability caused by telomere crisis forms the foundation for carcinogenesis. To survive, hepatic precursor cells achieve telomerase reactivation through various mechanisms, most notably via TERT gene promoter mutations, thereby bypassing senescence or apoptosis, acquiring immortality, and completing malignant transformation. Following the establishment of hepatocellular carcinoma, telomere biology interacts with epigenetic regulation (e.g., telomere region methylation) to influence the tumor immune microenvironment, collectively promoting tumor heterogeneity and progression. Treg: Regulatory T cell; CH₃: Methyl.

DIAGNOSTIC INNOVATIONS BASED ON TELOMERE FOR EARLY DETECTION AND PROGNOSIS OF LIVER CANCER

The progression of telomere measurement technologies, from conventional Southern blotting to quantitative polymerase chain reaction (qPCR) and next-generation sequencing, has been instrumental in advancing telomere research[23]. Although Southern blotting remains the reference standard for absolute telomere length assessment in tissue samples, its substantial DNA requirements and limited throughput constrain its clinical applicability[24]. The introduction of qPCR has greatly expanded access to telomere length analysis, particularly for high-throughput studies using peripheral blood leukocytes (PBLs)[25]. In addition to improved efficiency, these approaches enable locus-specific evaluation of telomere content, providing greater analytical resolution.

Tissue-based telomere assessment, most commonly performed using qPCR or telomere-specific fluorescence in situ hybridization on biopsy specimens, has been fundamental in establishing telomere shortening as a critical driver of HCC pathogenesis. Various studies have consistently demonstrated that shortened telomeres in cirrhotic liver tissue represent a strong, independent risk factor for subsequent HCC development, reflecting an advanced and often irreversible stage of liver disease[26]. However, tissue-based analyses are inherently limited by their invasive nature, associated procedural risks, and, importantly, sampling bias arising from pronounced intratumoral heterogeneity in telomere length and maintenance mechanisms[4]. This spatial variability, coupled with the impracticality of repeated sampling, significantly restricts the value of tissue biopsies for routine diagnosis and longitudinal prognostic evaluation in HCC.

These limitations have driven a paradigm shift toward liquid biopsy, a minimally invasive strategy that captures systemic tumor-related information through blood-based analyses. This approach is particularly transformative for studying telomere biology, as it enables dynamic monitoring of hepatocarcinogenesis. Principal circulating targets include cell-free DNA (cfDNA) and circulating tumor DNA (ctDNA)[27]. Assessment of telomere length in cfDNA, which represents a composite of DNA released from multiple cell types, has indicated that significant telomere shortening may serve as a signal of HCC presence[28]. Moreover, ctDNA has demonstrated substantial utility in HCC diagnosis, disease monitoring, and prognostic stratification. Xu et al[29] showed a strong concordance between the methylation profiles of HCC tumor DNA and matched plasma ctDNA. Using a large cohort comprising cfDNA samples from 1098 patients with liver cancer and 835 healthy controls, they developed a diagnostic prediction model that achieved high sensitivity and specificity for HCC detection.

Beyond telomere length, telomere fusions in peripheral blood are highly specific biomarkers of malignancy. Telomere fusions constitute a direct molecular imprint of prior “telomere crisis”, a phase marked by extreme genomic instability. Their detection in circulation strongly suggests active, advanced tumorigenesis and is associated with unfavorable clinical outcomes[30]. Similarly, the clinical relevance of PBL telomere length is being explored. Although its diagnostic performance in differentiating HCC from cirrhosis has been variable, shorter PBL telomeres are frequently associated with increased tumor burden and poorer prognosis, likely reflecting the cumulative systemic effects of chronic liver disease[14]. Finally, the most direct strategy involves detecting circulating telomerase-positive cells, which captures a defining hallmark of cancer biology[31].

Given the biological heterogeneity and complexity of HCC, the future of telomere-based diagnostics is unlikely to rely on any single biomarker. Instead, integrated multi-analyte panels are expected to provide greater clinical value by combining quantitative liquid biopsy parameters, such as ctDNA telomere length, telomere fusion status, and levels of circulating telomerase-positive cells, with conventional markers, including AFP and imaging findings, to establish a robust combinatorial diagnostic algorithm. This integrative approach is essential to overcome the limitations inherent to individual assays, improving sensitivity for early detection and enhancing diagnostic specificity. A comprehensive comparison of telomere-related biomarkers for HCC diagnosis is presented in Table 1.

Table 1 Comprehensive comparison of telomere-based diagnostic biomarkers for hepatocellular carcinoma[30,31,51-56].

Biomarker type	Sample source	Detection method	Sensitivity (%)	Specificity (%)	AUC	Clinical readiness	Ref.
Peripheral blood leukocyte telomere length	Peripheral blood	qPCR	40-65	60-80	Approximately 0.65	Clinical research phase	Liu et al[51]; Ma et al[52]
Circulating tumor DNA telomere length	Plasma	qPCR, NGS	70-85	80-90	0.80-0.87	Advanced clinical research	Campani et al[53]
Telomere fusions in plasma	Plasma	NGS	Approximately 90 (advanced HCC)	Approximately 95	NA	Early clinical research	Maciejowski and de Lange[30]
Circulating telomerase-positive cells	Peripheral blood	TRAP assay, FISH-flow cytometry	60-75	85-95	Approximately 0.85	Exploratory/technology development	Zhang et al[31]; Sapi et al[54]
Tissue TERT promoter mutations	Tumor tissue	Sanger sequencing, ddPCR, NGS	Approximately 60	Approximately 100	NA	Used for molecular subtyping/clinical research	Lombardo et al[55]
Multi-analyte integrated panel (e.g., ctDNA TL + TERT mutation + AFP)	Plasma/blood	Combination of methods	85-95	90-95	0.90-0.95	Cutting-edge exploratory/validation phase	Akuta et al[56]

AUC: Area under the receiver operating characteristic curve; AFP: Alpha-fetoprotein; ctDNA: Circulating tumor DNA; TL: Telomere length; qPCR: Quantitative polymerase chain reaction; NGS: Next-generation sequencing; TRAP: Telomeric repeat amplification protocol; FISH: Fluorescence in situ hybridization; ddPCR: Droplet digital polymerase chain reaction; HCC: Hepatocellular carcinoma; NA: Not applicable.

DISCUSSION

The central involvement of telomeres and telomerase in HCC extends beyond diagnostic and prognostic applications and offers substantial therapeutic potential. Our group previously exploited the human TERT promoter to drive the replication of oncolytic adenoviruses selectively and to regulate the expression of adeno-associated virus vectors carrying therapeutic genes, achieving tumor-specific cytotoxicity and targeted gene delivery in preclinical HCC models[32,33]. Moreover, non-viral strategies have been developed, including antisense oligonucleotides and small-molecule inhibitors that directly target telomerase or its RNA component. Several of these agents, such as Imetelstat, have advanced into clinical evaluation[8,34-36]. Imetelstat (GRN163 L), a 13-mer oligonucleotide that competitively binds the template region of telomerase RNA (TERC), is the most clinically advanced telomerase inhibitor to date. By sterically blocking telomere elongation, it has demonstrated clinical activity in phase II trials involving hematologic malignancies, including myelofibrosis and myelodysplastic syndromes, where reductions in mutant allele burden and transfusion independence have been observed in selected patient subsets[37]. However, its therapeutic efficacy in solid tumors, including HCC, remains uncertain. Early-phase trials in solid malignancies have reported limited single-agent activity, likely reflecting the slow kinetics of telomere shortening that necessitate prolonged treatment, as well as potential barriers to effective drug delivery[13].

Among emerging approaches, telomerase-targeted immunotherapy is among the most promising. Telomerase functions as a near-universal tumor-associated antigen, making it an attractive target for immune-based strategies. T cells engineered with chimeric antigen receptors or T cell receptors directed against telomerase-derived peptides, such as GV1001, are currently under active investigation[38,39]. These strategies aim to harness the cytotoxic capacity of the immune system to selectively eliminate HCC cells while sparing normal tissues, where telomerase expression is largely absent. Such advances support the concept of telomere-guided precision oncology, in which a tumor’s specific telomere maintenance mechanism, such as the presence of TERT promoter mutations, can inform therapeutic selection, including the preferential use of telomerase-targeted interventions in genetically defined patient subsets[40,41].

The diagnostic, prognostic, and therapeutic relevance of telomere biology is not confined to HCC and extends across a broad spectrum of malignancies. Even among primary liver cancers, substantial heterogeneity exists in telomere maintenance mechanisms. In intrahepatic cholangiocarcinoma, TERT promoter mutations are uncommon[42], suggesting a greater reliance on alternative telomere lengthening or compensatory pathways. In comparison, hepatoblastoma, a pediatric liver cancer, frequently shows telomerase reactivation, although this process appears to be governed by distinct, developmentally regulated mechanisms compared with adult HCC[43]. Insights from HCC research, therefore, provide a robust, translatable framework for understanding telomere-driven oncogenesis in other tumor types. Beyond hepatic malignancies, TERT promoter mutations are a defining molecular feature of glioblastoma and are associated with poor prognosis[44]. Similarly, these mutations are highly prevalent in urothelial carcinoma and melanoma, where they carry significant diagnostic and prognostic implications[45,46]. The concept of telomere crisis as a driver of genomic instability, initially characterized in hepatocarcinogenesis models, is now recognized as a fundamental mechanism underlying the evolution of multiple epithelial cancers. Similarly, telomere shortening or telomerase activity in liquid biopsies is being actively explored as a universal biomarker for early cancer detection and for monitoring minimal residual disease in malignancies such as lung, breast, and pancreatic cancers[47-49]. The integration of telomere-based markers into multi-analyte diagnostic panels thus holds broad applicability and promise for improving early detection and risk stratification across oncology.

CONCLUSION

In summary, telomeres and telomerase have evolved from basic biological concepts into central components of the clinical management of HCC and other cancers. The convergence of advanced liquid biopsy technologies, integrative multi-analyte diagnostic strategies, and innovative therapeutic approaches targeting telomere biology signals the advent of a new era in precision oncology. Realizing this potential will require a focused translational roadmap. From a diagnostic perspective, key challenges include assay standardization, establishing clinically meaningful thresholds, and demonstrating incremental value over existing markers such as AFP. Prospective, multicenter studies are essential to validate telomere-based liquid biopsies in high-risk surveillance and in monitoring residual disease. From a therapeutic standpoint, successful clinical implementation of telomerase-targeted agents will depend on optimized patient selection using predictive biomarkers, rational combination strategies, and careful management of treatment-related toxicity. Addressing these challenges through interdisciplinary collaboration will be critical to accelerating the translation of telomere biology into clinical practice and ultimately improving outcomes for patients with HCC.

ACKNOWLEDGEMENTS

The authors would like to express their sincere gratitude to Professor Wang YG for his invaluable guidance and insightful critiques throughout the preparation of this manuscript. His expertise and mentorship were instrumental in shaping the direction and depth of this work. We are also deeply thankful to Sultan MH for his significant contribution during the initial phase of this project, particularly for his thoughtful input in helping to conceptualize the article’s framework and outline. Furthermore, we acknowledge all colleagues and collaborators who provided technical support and constructive discussions.