Hepatocellular carcinoma, one of the most common and deadly forms of liver cancer worldwide, often presents challenges in treatment due to its aggressive nature and high rates of recurrence post-surgery. Identifying reliable prognostic biomarkers is therefore crucial for advancing therapeutic strategies and tailoring personalized medicine approaches. Against this backdrop, the study by Lu and colleagues probes the roles of mut-L homolog 1 (MLH1), a key DNA mismatch repair protein, and G-protein coupled receptor C5C (GPRC5C), a less characterized receptor, in HCC biology.

Previous research had implicated MLH1 in cancer initiation and progression, highlighting its frequent loss as a driver of genomic instability. Furthermore, MLH1 was reported to inhibit pancreatic cancer metastasis by downregulating GPRC5C, suggesting a potentially significant interplay between these proteins in tumor dynamics. However, their precise expression profiles and prognostic relevance in hepatocellular carcinoma remained unexplored until now.

The investigative team analyzed tumor samples and adjacent non-tumoral liver tissues from 230 patients who underwent radical resection for HCC. Using tissue microarray-based immunohistochemical staining, they quantified MLH1 and GPRC5C expression levels, enabling a comprehensive comparison between malignant and normal tissue contexts. This large and well-characterized cohort provides robust statistical power to elucidate the molecular correlations within human liver cancer.

Remarkably, the data revealed opposite expression trends for these two genes: MLH1 protein levels were significantly diminished in HCC tumor tissues relative to adjacent normal liver, whereas GPRC5C expression was elevated in the cancerous samples. This inverse relationship was substantiated by a strong negative correlation coefficient, underscoring the antagonistic roles that MLH1 and GPRC5C likely play in tumor biology.

The researchers further investigated correlations between gene expression and clinically relevant parameters. MLH1 exhibited a negative association with alpha-fetoprotein (AFP) levels, a biomarker frequently elevated in liver cancer patients. Conversely, GPRC5C positivity correlated positively with larger tumor size and the presence of vascular invasion, two key indicators of aggressive disease. These findings suggest that reduced MLH1 and increased GPRC5C expressions might respectively signify more favorable and adverse tumor characteristics.

Survival analysis painted a compelling prognostic picture. Patients with high MLH1 expression enjoyed significantly better overall and disease-free survival outcomes, indicating its protective role in the cancer milieu. On the other hand, elevated GPRC5C corresponded with poorer survival metrics, marking it as a potential oncogenic factor. When adjusting for confounding variables in multivariate models, GPRC5C retained its strong prognostic significance for both overall and disease-free survival, whereas MLH1 remained significant primarily for overall survival.

To validate these clinical associations, the study tapped into the publicly accessible Kaplan-Meier Plotter database, which aggregates survival data from diverse gene expression studies. Consistently, MLH1 expression predicted recurrence-free and progression-free survival, reinforcing its utility as a prognostic biomarker in HCC. GPRC5C, while trending toward negative effects on survival, showed less statistical significance in this broader dataset, highlighting the need for continued investigation.

The divergent expression and functional relationships between MLH1 and GPRC5C illuminate a complex regulatory axis that may govern tumor aggressiveness in hepatocellular carcinoma. MLH1, traditionally implicated in maintaining genomic integrity through mismatch repair, appears to confer tumor-suppressive effects. Its loss may unleash oncogenic pathways, partially mediated by increased GPRC5C activity, which promotes tumor growth and invasion.

From a translational perspective, these findings open avenues for developing MLH1 and GPRC5C as biomarkers for risk stratification in HCC patients. Evaluating their expression could help identify individuals who are more likely to benefit from surgical resection or require more intensive follow-up and adjuvant therapies. Furthermore, targeting the GPRC5C pathway might emerge as an innovative therapeutic strategy to curb tumor progression.

The study also emphasizes the utility of tissue microarray platforms combined with immunohistochemistry to unravel complex molecular signatures in cancer specimens. This approach enables high-throughput, standardized assessment across large patient cohorts, bolstering the reproducibility and clinical relevance of biomarker studies.

While the current results are promising, the authors caution that further functional studies and clinical trials are essential to clarify the mechanistic underpinnings of MLH1-GPRC5C interplay in hepatocellular carcinoma. Understanding how these proteins influence signaling cascades, cellular proliferation, and metastatic potential will be pivotal for translating these molecular insights into effective treatments.

In summary, Lu and colleagues present compelling evidence that MLH1 and GPRC5C serve as potent, inversely correlated prognostic markers in resectable hepatocellular carcinoma. Their work offers a nuanced perspective on liver cancer pathology, underscoring the interplay between DNA repair deficiency and G-protein coupled receptor signaling in dictating tumor behavior.

As hepatocellular carcinoma incidence continues to rise globally, driven by factors such as chronic hepatitis infections and metabolic disorders, the need for precise biomarkers and targeted interventions intensifies. Investigations like this one provide critical stepping stones toward personalized oncology, wherein molecular profiling of tumors guides therapeutic decision-making and ultimately improves patient survival.

Future research should explore how modulation of MLH1 and GPRC5C expression affects tumor microenvironment interactions, immune evasion, and response to emerging therapies such as immune checkpoint inhibitors and targeted agents. Integrating these molecular biomarkers with clinical parameters promises to refine existing staging systems and optimize management of hepatocellular carcinoma.

This landmark study thus marks a significant advance in the cancer biomarker field and highlights the dynamic interplay between DNA repair processes and receptor-mediated signaling in the pathogenesis and progression of hepatocellular carcinoma.

Subject of Research: Expression patterns and prognostic significance of MLH1 and GPRC5C in resectable hepatocellular carcinoma.

Article Title: Expression and prognostic significance of MLH1 and GPRC5C in resectable hepatocellular carcinoma

Article References:
Lu, J., Li, L., Chen, Q. et al. Expression and prognostic significance of MLH1 and GPRC5C in resectable hepatocellular carcinoma. BMC Cancer 25, 1215 (2025). https://doi.org/10.1186/s12885-025-14591-1

Image Credits: Scienmag.com

DOI: https://doi.org/10.1186/s12885-025-14591-1

Circular RNAs (circRNAs) have emerged as a novel class of endogenous non-coding RNAs characterized by covalently closed loop structures, devoid of 5’ caps and 3’ polyadenylated tails, conferring exceptional stability in biological fluids. Their unique configuration resists exonuclease-mediated degradation, thereby positioning circRNAs as highly promising candidates in cancer biomarker research. While circRNAs have been implicated in various cancer biology mechanisms, their clinical utility, particularly in hepatocellular carcinoma, remains largely under-explored, making this study a pioneering endeavor.

In this pivotal cross-sectional analysis, researchers measured serum levels of hsa_circ_101555 using quantitative real-time polymerase chain reaction (qRT-PCR) among 62 Egyptian patients clinically and radiologically diagnosed with HCC, juxtaposed against 30 healthy controls. Measurements were taken at baseline prior to treatment and subsequently three months post-therapy, enabling a dynamic assessment of circRNA expression in relation to tumor behavior and therapeutic response.

Strikingly, the study revealed a profoundly elevated mean expression level of hsa_circ_101555 in HCC patients (7.66 ± 3.74) relative to healthy individuals (1.21 ± 0.96). Such a significant differential underscores the potential diagnostic value of this circRNA in distinguishing malignant from non-malignant hepatic states. Receiver operating characteristic (ROC) analyses further substantiated this premise, highlighting an exceptional discriminatory capacity with an area under the curve (AUC) of 0.984 at a threshold value of 1.966, thus exhibiting almost perfect accuracy.

Beyond diagnosis, hsa_circ_101555 demonstrated considerable prognostic relevance. Its post-interventional serum levels exhibited a notable ability to differentiate between patients showing tumor progression or regression, classified through the Response Evaluation Criteria in Solid Tumors (RECIST) and its modified iteration (mRECIST). At a cutoff of 5.1150, the circRNA yielded an AUC of 0.891, indicative of strong predictive performance for disease trajectory and therapeutic outcomes. This relationship was substantiated through comprehensive statistical assessments reflecting the biomarker’s sensitivity in capturing tumor dynamics.

Delving deeper, the study uncovered significant positive correlations between post-treatment hsa_circ_101555 levels and several established laboratory indices indicative of liver insult and dysfunction. These included the albumin-bilirubin (ALBI) score, where the correlation coefficient (r) was 0.424 (p = 0.001), as well as the neutrophil-to-lymphocyte ratio (NLR) with r = 0.410 (p = 0.001). Additional correlations emerged with alpha-fetoprotein (AFP), aspartate aminotransferase/alanine aminotransferase ratio (AST/ALT), fibrosis-4 (FIB-4) index, and the aspartate aminotransferase to platelet ratio index (APRI), all underscoring the association of hsa_circ_101555 with hepatic inflammation, fibrosis severity, and overall disease burden.

Notably, hsa_circ_101555 levels also correlated with pivotal clinical and pathological tumor characteristics essential for staging and therapeutic decision-making. Elevated circRNA levels were significantly linked to larger tumor size (greater than 5 cm), increased tumor multiplicity (more than three nodules), the presence of vascular invasion, advanced Barcelona Clinic Liver Cancer (BCLC) stage C, and higher Tumor, Node, Metastasis (TNM) staging. These correlations affirm the circRNA’s potential in reflecting tumor aggressiveness and metastatic potential.

The intricate interplay between circRNAs and oncogenic processes has garnered increasing attention, as they can function as microRNA sponges, interact with RNA-binding proteins, and modulate transcriptional and posttranscriptional networks crucial to tumor biology. The upregulation of hsa_circ_101555 observed in this study suggests that it may exert functional roles in hepatocarcinogenesis, potentially contributing to tumor proliferation, invasion, and resistance mechanisms. However, elucidating its exact molecular mechanisms remains an imperative frontier for future translational research.

From a clinical perspective, the identification of serum-based, non-invasive biomarkers such as hsa_circ_101555 carries profound implications. They could complement existing imaging modalities and serological tests, enabling earlier diagnosis, real-time monitoring of therapeutic response, and timely detection of disease progression or recurrence. This is of paramount importance in HCC, where prognosis is often poor due to late presentation and limited effective treatments in advanced stages.

Furthermore, the study presents hsa_circ_101555 as a candidate biomarker customized to the Egyptian population, addressing the regional epidemiological burden of HCC. Given genetic and environmental factors modulating disease prevalence and characteristics across populations, such region-specific biomarkers offer tailored clinical utility and pave the way for personalized medicine approaches in oncology.

Technically, the use of qRT-PCR for circRNA quantification in serum illustrates the assay’s sensitivity and reproducibility for clinical application. The methodology employed underscores robust molecular techniques adapted for biomarker validation, including normalization strategies and data analysis adhering to rigorous statistical standards. These technical advances enable the transition of circRNAs from bench to bedside.

While promising, the study’s cross-sectional design and sample size do suggest caution, emphasizing the need for longitudinal studies with larger cohorts to validate the findings, establish causality, and assess circRNA dynamics over extended treatment timelines. Additionally, integrating multi-omics data encompassing transcriptomic, proteomic, and epigenetic landscapes could illuminate the broader regulatory impact of hsa_circ_101555 in HCC.

In summary, this landmark investigation offers compelling evidence that serum-derived hsa_circ_101555 harbors significant oncogenic and biomarker potential in hepatocellular carcinoma. Its elevated expression correlates robustly with disease presence, severity, progression, and key clinical features. As researchers and clinicians grapple with the complex challenge of HCC management, circRNAs like hsa_circ_101555 may soon emerge as indispensable tools, transforming diagnostic paradigms and enabling more precise prognostication—and ultimately improving patient outcomes.

The groundbreaking implications of this study mark a pivotal step towards harnessing the untapped universe of circular RNAs. With further validation and mechanistic exploration, hsa_circ_101555 may herald a new era in non-invasive cancer biomarker discovery, transforming the landscape of hepatocellular carcinoma diagnosis and prognostication worldwide.

Subject of Research: Hepatocellular carcinoma; circular RNA biomarkers; non-invasive diagnosis and prognosis.

Article Title: The Potential Oncogenic Role of Serum-derived hsa_circ_101555 as a Non-invasive Diagnostic/Prognostic Marker in Patients with Hepatocellular Carcinoma

News Publication Date: 17-Mar-2025

Web References: http://dx.doi.org/10.14218/GE.2025.00012

Keywords: Hepatocellular carcinoma; Circular RNA; hsa_circ_101555; Biomarkers; Diagnosis; Prognosis; Liver cancer; Non-coding RNA; qRT-PCR; Tumor progression; Liver fibrosis; Oncogenic markers