CD44 splice variant expression in clear cell carcinoma of the ovary.

OBJECTIVE

CD44 is a surface glycoprotein widely distributed among different tissues. Malignant tumors may show a more complex pattern of CD44 expression, indicating a loss of splice control. The aim of our study is to investigate the expression of CD44 splice variants (CD44v) and its metastatic potential in clear cell carcinoma of the ovary.

METHODS

Twenty-two cases of clear cell carcinoma of the ovary were evaluated for CD44 standard form (CD44s) and splice variants: -4v, -6v, and -9v expression by immunocytochemistry.

RESULTS

Twenty-one primary ovarian tumors and 23 metastatic sites were available for evaluation. Eighteen of 21 (86%) of ovarian sections studied expressed CD44s; 15/21 (71%) expressed CD44-4v; 14/21 (67%) expressed CD44-6v; and 12/21 (57%) expressed CD44-9v. Of 23 metastatic sites evaluated, 87% expressed CD44s. In contrast, only 5 (22%) metastases had CD44-4v and CD44-6v expression and 8 (35%) had CD44-9v immunoreactivity. None of 10 normal contralateral ovaries expressed CD44s or any splice variants. In 2 cases we had tumor available from the primary surgery, and subsequent recurrences. Both recurrences showed decreased expression of CD44-4v and CD44-6v.

CONCLUSIONS

Clear cell carcinoma of the ovary shows an abnormal pattern of CD44s expression and mRNA splicing when compared to the contralateral normal ovary in the same patient. Metastases of clear cell carcinoma show a downregulation in expression of some splice variants. Furthermore, we have data that suggest that as the tumors recur, CD44s and its isoforms are downregulated. Our results suggest that alternative mRNA splicing of CD44 may be important in the development of metastases from clear cell carcinoma of the ovary.