The influence of hormones on CD44 expression in endometrial and breast carcinomas

The expression of distinct variant isoforms of the cell surface glycoprotei n CD44 (CD44v) has been found to be associated with metastatic potential of rodent adenocarcinoma cells and with an altered prognosis in several types of human cancer. In hormone-dependent gynecological cancers, different CD4 4v expression patterns have been observed. The influence of ovarian steroid hormones and their antagonists on CD44v expression is still unclear, since there are only retrospective correlation studies so far. Therefore, we exa mined the CD44 mRNA expression in a standardized Stimulation experiment in a number of breast and endometrial carcinoma cell lines varying in estrogen receptor (ER) status. Higher CD44 overall expression was observed in ER po sitive endometrial and breast carcinoma cell lines when compared to corresp onding ER negative cell lines. The number and composition of alternatively spliced isoforms showed no clear correlation to the ER expression status. T hree CD44v isoforms were detected in all cell lines expressing CD44v, two o f which have not been reported previously in normal endometrial cells. Thes e isoforms may have specific functions in this type of carcinoma. In the se cond part of the study, the influence of (anti-) hormones on CD44 expressio n in endometrial carcinoma cell lines was examined. CD44 overall expression showed an increase when the cells were grown in medium containing fetal ca lf serum (FCS) as compared to cells maintained in medium-free of FCS. CD44 expression was transiently increased by estradiol (1 h). The CD44 splice pa ttern of endometrial cancer cell lines RL95-2 and Hec-1-A, after treatment with (anti-) hormones showed constant and high expression rates for distinc t CD44v-isoforms such as CD44E (CD44v8-v10), Only certain weakly expressed isoforms changed their expression level during the experimental period, but no direct Correlation to hormone treatment was observed. In conclusion, es tradiol or FCS increase CD44 overall expression, but there seems to be no d irect influence of ovarian steroid hormones on the CD44v splice machinery i n endometrial carcinoma cell lines.