First class of MEK1 mutants with RAF dependent (D67N, P124L, P124S, L177V), the second class of MEK1 mutants, RAF regulated (E203K, L177M, C121S, F53L, K57E, Q56P, K57N, ΔE51-Q58, ΔF53-Q58) and the third class of MEK1 mutants RAF independent (ΔL98-I103, ΔI99-K104, ΔE102-I103, ΔI103-K104), where Δ is indicating a deletion of an amino acids sequence or the fact that the sequence is missing.525,526 It was demonstrated that P124L and Q56P mutations in MEK1 confer resistance to MEK and RAF inhibitors in melanomas.527. The gene discussed is RAF1; the disease is melanoma.