# Association of a CD44s-v5-v6 Null Phenotype with Advanced Stage Cholangiocarcinoma: A Preliminary Study

## TL;DR

This study found that the absence of three CD44 proteins in bile duct cancer tumors is linked to more advanced disease stages, suggesting a new way to identify high-risk patients.

## Contribution

The study identifies a novel 'CD44s-v5-v6 Null' phenotype associated with advanced-stage cholangiocarcinoma, offering a new biomarker for risk stratification.

## Key findings

- The complete absence of CD44s, CD44v5, and CD44v6 in tumors was associated with advanced TNM stages.
- The 'CD44s-v5-v6 Null' phenotype was observed in 13.1% of patients and showed a trend toward poorer survival.
- Individual CD44 isoforms were not reliable independent prognostic markers in this cohort.

## Abstract

Cholangiocarcinoma is a very aggressive bile duct cancer with poor survival rates, making it crucial for doctors to better predict patient outcomes. Scientists have long studied proteins on the surface of cancer cells, called CD44, as potential clues, but their role has been unclear. This study investigated three specific CD44 proteins in patient tumors to see if their presence could predict the disease’s course. Unexpectedly, the researchers found that the tumors completely lacking all three of these proteins were associated with more advanced-stage cancer. This suggests that the absence of these markers, rather than their presence, could identify a new high-risk patient group. This finding may help doctors better classify tumors and could guide future research into new treatment approaches for these high-risk patients.

Background/Objectives: Cholangiocarcinoma (CCA) is an aggressive malignancy with a poor prognosis, creating an urgent need for novel biomarkers to improve risk stratification. The prognostic significance of the transmembrane glycoprotein CD44 and its isoforms (CD44s, v5, v6) in CCA remains controversial. This preliminary study aimed to investigate whether the combined loss of these isoforms could serve as a distinct prognostic indicator. Methods: We evaluated the expression of CD44s, CD44v5, and CD44v6 via immunohistochemistry on a retrospective cohort of 61 paraffin-embedded CCA patient tissue blocks from Ramathibodi Hospital, Bangkok, Thailand. Expression levels were correlated with clinicopathological parameters. Survival analyses, including Kaplan–Meier and Cox proportional hazards models, were used to determine the prognostic value of individual isoforms and the complete absence of all three. Results: Expression of CD44s, CD44v5, and CD44v6 was found in 52.5%, 47.5%, and 82.0% of tumors, respectively. In univariate and multivariate analyses, the expression of any single isoform was not a significant predictor of overall survival. However, a subgroup of 8 patients (13.1%) was identified whose tumors were negative for all three isoforms, a phenotype we termed “CD44s-v5-v6 Null”. This status was significantly associated with advanced TNM stages (p = 0.022). Patients with these Null tumors also showed a clinically relevant, though not statistically significant, trend towards poorer survival (median 7.0 vs. 12.0 months, p = 0.336). Conclusions: Individual CD44 isoforms did not serve as reliable independent prognostic markers in this cohort. Instead, the complete loss of the CD44 expression program characterizes a potential “CD44s-v5-v6 Null” phenotype associated with advanced-stage disease.