Characterization of CD44v3-containing isoforms in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is a debilitating and deadly disease that is only cured 50% of the time. A better understanding of the molecular mechanisms involved in HNSCC progression may lead to earlier detection and improved cure rates. CD44 is a ubiquitous transmembrane glycoprotein comprising a family of alternatively spliced isoforms involved in cell migration and cell proliferation. CD44 isoforms containing the variant 3 (v3) exon include a growth factor binding site and may be involved in tumor progression. To characterize CD44v3-containing isoforms expression in HNSCC we purified RNA from four HNSCC cell lines and performed RT-PCR using junction primer strategies followed by gel elecrophoresis. Cloning and sequencing of HNSCC cell line PCR products revealed two isoforms. One of these, CD44v3-10, has been previously described. The other isoform, CD44v3, has not been characterized in HNSCC tissues. To further study this isoform, we purified RNA from 19 HNSCC tissues, 7 normal margin tissues and 5 true normal tissues. Following reverse- transcription, we performed quantitative PCR using junction primers specific for CD44v3. Results show that HNSCC tumor tissues expressed mean CD44v3 levels that were elevated 4.5 times more than true normal tissues (p < 0.01). Mean CD44v3 values for HNSCC tumors were 0.43 ± 0.44 while mean levels for true normal tissues were 0.10 ± 0.11. Levels in tumor tissue did not vary significantly with tumor characteristics such as site, stage, prior treatment, or nodal status. In addition, to characterize the role of this molecule plays in tumor progression, we overexpressed CD44v3 in a HNSCC cell line. Our results indicate that although higher levels of CD44v3 did not affect the rate of proliferation, a significant increase in migration was observed. CD44v3 may provide a target for future diagnostic and therapeutic interventions for HNSCC.