Enhancement of sialyltransferase in two melanoma cell lines that are growth-inhibited by retinoic acid results in increased sialylation of different cell-surface glycoproteins.

Previous studies have demonstrated the ability of retinoic acid (RA) to inhibit the growth of two spontaneous murine melanoma cell lines (B16-F1 and S91-C2) and to augment both sialyltransferase activity and the sialylation of an Mr 160,000 cell-surface glycoprotein. The present study examined the effects of RA on an ultraviolet irradiation-induced murine melanoma cell line K-1735P. Like the two spontaneous melanomas, the uv-induced melanoma exhibited susceptibility to the growth-inhibitory action of RA. Both the anchorage-dependent and the anchorage-independent growths of the K-1735P cells were suppressed by RA, with IC50 values of 5 X 10(-9) and 3 X 10(-12) M, respectively. Sialyltransferase activity in both S91-C2 and K-1735P cells treated with 10(-6) or 10(-5) M RA increased two- and three-fold, respectively, as compared with untreated cells. In contrast, cell-surface sialo- and galactoglycoproteins, revealed by labeling with periodate and tritiated borohydrate or with neuraminidase, galactose oxidase, and tritiated borohydrate, respectively, varied between the S91-C2 and the K-1735P cells, and each cell line's modulation by RA was also distinct. These findings suggest that although RA can increase the activity of sialyltransferase in different melanoma cells, this increased activity may, in turn, result in an increased sialylation of distinct cell-surface glycoproteins.