NRAS and cancer: Moreover, when we analysed a dataset derived from a drug screen using a large panel of cancer cell lines [25], we found not only that NRAS mutant melanoma cell lines were more resistant to pyrimethamine than BRAF mutant melanoma cells (Figure 6D), but that independently of cancer type, mutRAS cancer cells were significantly more resistant to pyrimethamine than mutBRAF cells (Figure 6E).