Clear cell carcinoma of the ovary: characterization of its CD44 isoform repertoire.

Objective: CD44 is a cell surface receptor implicated in tumor metastases. We have previously shown that there is a loss of CD44 splice control in clear cell carcinoma (CCCa) of the ovary. Our aim is to characterize the expression of CD44-3v, -5v, -7v, and -10v in clear cell ovarian tumors and to determine their prognostic value.

Methods: Twenty-two cases of ovarian CCCa were studied for CD44-3v, -5v, -7v, and -10v expression by immunocytochemistry.

Results: The primary tumors showed expression of CD44-3v, -5v, -7v, and -10v in 44, 55, 61, and 39% of the cases, respectively. We were able to compare the expression of CD44 in the primary tumor and metastatic sites from the same patient in 7 cases (metastatic sites n = 16). We observed decreased immunoreactivity of CD44-3v, -5v, -7v, and -10v in 67, 100, 93, and 92% of the sites, respectively. CD44-3v and -10v expression was absent in 100% of the nonaffected contralateral ovaries while -7v and -10v were expressed in 1/11 (9%) of them. When CD44-10v was not expressed in the primary tumor, only 18% of the women recurred or died of disease; in contrast, of the cases where it was present, 71% of the women recurred or died of disease (P = 0.049).

Conclusions: There is aberrant alternative mRNA splicing in the development of CCCa of the ovary when compared to the contralateral nonaffected ovary. The expression of CD44-10v correlates with survival. Larger series are needed to further understand the role of CD44 isoforms in ovarian cancer metastases.