MAPK1 and neoplasm: Thus, a reasonable initial clinical strategy for patients who relapse on single-agent BRAF or MEK inhibitor would be to treat with the combination of a BRAF and a MEK inhibitor if their tumor harbors an ERK-dependent resistance mechanism or to treat with the combination of a PI3K inhibitor and a MEK or BRAF inhibitor if their resistant tumor is driven by an ERK-independent mechanism.