Comparative analysis of the effects of dimethyl sulfoxide and retinoic acid on the antigenic pattern of human ovarian adenocarcinoma cells.

HOC-7 malignant ovarian surface epithelial cells have been exposed to differentiation promoters like dimethyl sulfoxide (DMSO) and retinoic acid (RA) and the resulting cell phenotypes were characterized immunologically. Immunocytochemistry revealed that DMSO caused elevation of membrane-associated staining for epidermal growth factor-receptor (EGF-R) and for desmoplakins I and II (DPI+II). DMSO also stimulated cytoplasmic and surface labelling for CA 125 and extracellular deposition of fibronectin (FN). A fixed-cell ELISA system was used for quantification of these differentiation-like responses and revealed that DMSO efficiently induced expression of EGF-R, CA 125, FN and DPI+II in dose-dependent manner. Immunocytochemistry, ELISA and Western blotting additionally demonstrated that both DMSO and RA caused down-regulation of myc oncoproteins. Densitometer evaluation of electrophoresed proteins revealed a 50% DMSO- and a 25% RA-induced myc reduction. Apart from growth reduction, which was seen for both inducers, inhibition of myc gene expression was the only response of HOC-7 cells to RA-treatment. The extent of myc down-regulation seems, therefore, to be crucial for the initiation of maturational processes in the cells. Subsequent phenotypic differentiation of HOC-7 cells causes elevated levels of EGF-R, CA 125, FN and DPI+II. This cell model might be useful for the distinction between induced growth reduction and differentiation of ovarian cancer cells.