CD44 variant 6 isoform (CD44v6)

Molecular Classification

Receptor, Cell adhesion molecule, Type 1 transmembrane glycoprotein, Co-receptor

Other Names

CD44v6, CD44 exon v6-containing isoform, CD44 variant exon 6 isoform

Disease Roles

Cancer (including colorectal, lung, liver, prostate, pancreatic, endometrial, head and neck squamous carcinomas)MetastasisChemoresistance

CD44 variant 6 isoform Overview

CD44 variant 6 isoform (CD44v6) is a type 1 transmembrane glycoprotein and a splice variant of the CD44 receptor, produced by alternative splicing of the CD44 gene mRNA to include exon v6. CD44v6 is distinguished by its extracellular v6-encoded domain, which confers unique functional properties distinct from the standard isoform (CD44s). CD44v6 participates in cell adhesion, migration, and signal transduction by acting as a co-receptor for ligands such as hyaluronic acid, osteopontin, and various growth factors. Notably, CD44v6 is implicated in regulating key pathways for cell proliferation, survival, apoptosis resistance, and autophagy, contributing to tumor progression, metastasis, and chemoresistance in several cancers. CD44v6 can promote resistance to cell death by physically interfering with the FAS apoptotic pathway and by acting as a necessary co-receptor for receptor tyrosine kinases like c-Met and VEGFR-2, amplifying growth and survival signaling in tumor cells. Its expression is upregulated in many cancers and correlates with more aggressive disease, making it a promising therapeutic target and clinical biomarker, albeit with concerns about on-target toxicity due to low-level expression in normal tissues[1][2][3][4][5][6].

Mechanism of Action

Antibody blockade of CD44v6 prevents its interaction with partners and impairs its function as a co-receptor, thereby reducing tumor cell survival, migration, and invasiveness[6]. - Inhibition of CD44v6-mediated chemoresistance and apoptosis evasion (e.g., through FAS pathway modulation)[4]. - Interference with growth factor presentation (e.g., hepatocyte growth factor [HGF] and c-Met activation), which can disrupt tumor signaling pathways[6].

Biological Functions

Cell adhesion

Signal transduction

Cell proliferation

Cell migration and invasion

Apoptosis regulation

Angiogenesis

Chemoresistance

Autophagy regulation

Disease Associations

Cancer (including colorectal, lung, liver, prostate, pancreatic, endometrial, head and neck squamous carcinomas)

Metastasis

Chemoresistance

Tumor progression

Inflammation (limited evidence)

Possibly others (context-specific)

Safety Considerations

Potential for on-target off-tumor toxicity, since CD44v6 is expressed at low levels in certain normal tissues (especially epithelium), raising risk for toxicity of antibody-drug conjugates[6].
Previous clinical trials of anti-CD44v6 antibodies have noted dermatological and mucosal toxicity.

Interacting Drugs

Antibody-based therapeutics (e.g., anti-CD44v6 antibodies such as bivatuzumab)

Peptide inhibitors of CD44v6

No widely approved small molecule inhibitors as of 2024, but molecule development and preclinical studies are ongoing[6].

Associated Biomarkers

Biomarker
CD44v6 expression status in tumors is used as a biomarker for poor prognosis in several cancers, such as colorectal cancer, gastric cancer, and others[2][3][6].
CD44v6 can serve as a potential marker for predicting chemoresistance and metastatic potential in tumors[1][4].