Expression of CD44 standard and variant isoforms v5, v6 and v7 in human ovarian cancer cell lines.

The expression of standard CD44 protein (CD44std) and its splice variants v5, v6 and v7 was investigated in 43 human ovarian carcinoma cell lines by flow cytometry and immunocytochemistry using monoclonal antibodies raised against extracellular epitopes. Twenty six (60%) cell lines expressed CD44 std. Variant isoforms of CD44 were expressed in 12 of the 26 CD44 positive cell lines. All 12 cell lines expressed CD44 v5. In addition 6 cell lines expressed CD44 v6 and one of these expressed CD44 v7 simultaneously. No significant differences of CD44 expression were found between cell lines derived from solid tumors or ascites. In ovarian cancer cells splicing of CD44 v5 appears to be a prerequisite for expression of downstream variable exons. New acquisition of variable CD44 exons may be implicated in the tumorigenesis of ovarian cancer. The CD44 gene provides a biological model to study the role of alternative splicing in gynecologic malignancy.