Characterization of a human melanoma cell line with non-oestrogen receptordependent tamoxifen resistance

While investigating the mechanism of synergistic cytotoxicity between tamox ifen (TAM) and cisplatin (DDP) we developed a TAM-resistant variant of the human melanoma cell line T-289. We sought to characterize this cell line wi th respect to the effect of TAM resistance on a variety of different intrac ellular cell cycle control and apoptotic pathways, A TAM-resistant variant cell line (289 TAM(6)) was developed and the technique of Western analysis was to determine the changes in protein expression that occurred as a resul t of the development of TAM resistance. In this model, TAM resistance resul ted in an increase in the detectable basal levels of cyclin E, GADD 153, p1 6, BAX, Bcl-X-L, and wild-type and mutant p53, an increase in TAM induction of p16, and a decrease in the detectable basal levels of cyclin D-1, p21 a nd p27. There were no detectable changes in the revels of pRb. In the TAM-r esistant variant, p21 levels were essentially undetectable, while p27 was p resent and maintained its response to TAM induction, albeit at a much lower level. This investigation demonstrates that the development of TAM resista nce is associated with a change in the detectable levels of a variety of ce ll cycle control and apoptosis-related proteins. While the exact role that each change plays in the development of tamoxifen resistance remains to be determined, these data suggest that the development of resistance to a part icular agent results in changes in multiple, seemingly unrelated pathways. These data have implications for future studies in both the laboratory and the clinic. (C) 1999 Lippincott Williams & Wilkins.