Frozen sections of the tumors were prepared and immunostained for CD31, a repre

Historically antifolate drugs such as methotrexate or edatrexate have shown very little activity in clinical trials supplier INNO-406 with melanoma patients although these trials were per formed before the discovery of BRAF and RAS as drivers of melanomagenesis. The lack of response in mel anoma patients can be explained by several mechanisms of resistance such as melanosomal sequestration of drugs, the upregulation of both DHFR and the pro survival tran scription factor MITF in response to MTX, or the E2F and Chk1 mediated effects, as recently described. Despite the inherent capacity to resist any chemotherapy our data suggest that stratifying patients according to their BRAFRAS mutation status could lead to better responses to antifolate based therapies.<br><br> Importantly, our findings suggest that the correlation be tween NRAS and BRAF mutations and their differential re sponse to antifolate drugs might apply to other cancer types. Therefore, in cancer types where antifolate based therapies contribute to achieve clinical responses in RAS patients. it would be inter esting to assess whether mutBRAF patients supplier Lapatinib show even im proved responses. If that were the case it would open the possibility to use mutational status as a predictor of patient response. In summary, our findings identify the mutually exclusive NRAS and BRAF mutation status as possible pre dictive marker for the response to DNA synthesis inhibitors such as antifolate drugs in melanoma patients. Conclusions In summary in this study we demonstrate that activation of DTIC with white light does not result in a methylat ing agent but in to an inhibitor of purine synthesis.<br><br> We show that RAS mutant melanoma cells are more resist ant to drugs affecting DNA synthesis than BRAF mutant cells. Our data suggests that, the increased resistance to de novo DNA synthesis inhibitors found in RAS mutant cells is due to a superior capacity to salvage DNA. Notably our results suggest the possibility that the correlation Lonafarnib 価格 between RAS and BRAF mutations and the response to antifolate drugs might be relevant in other cancer types although further efforts to confirm this hypothesis are warranted. Materials and methods Cell culture Nine mutant BRAF cell lines and nine mutant NRAS cell lines were used in the study. These cells were a kind gift from Dr. Richard Marais and Dr. Adam Hurlstone. Cell stocks were expanded, frozen, and kept in liquid nitrogen.<br><br> New aliquots were thawed every 5 7 weeks. Cells were cultured in Dulbeccos Modi fied Eagles Medium or in RPMI 164 medium as previously indicated, supple mented with 0. 5% penicillin and streptomycin and 10% bovine calf serum. Cells were grown at 37 C in a 5% CO2 environment. Reagents HAT supplement was from Sigma. Dacarbazine, car mustine, cisplatin and temozolomide and lomeguatrib were from SIGMA. Hypoxanthine, guanosine and 5 guanosine monophosphate were from Sigma. AZD6244 was from Sell eck Chemicals, Newmarket, UK. Mycophenolic Acid and AVN944 were from Sigma and ChemieTek respectively. Aminopterin, pyrimethamine and amethopterin were from Sigma. All drugs were dissolved in dimethyl sulfoxide and, apart from dacarbazine, directly added to cell in culture at the indicated concentrations. Prior to addition onto cells DTIC was exposed to white light for 1 h, as previously described.