Combination of CYP inhibitor with MEK/ERK inhibitor enhances the inhibitory effect on ERK in BRAF mutant colon cancer cells.

To investigate mechanisms of discrepancy in response to a MEK/ERK inhibitor, U0126, in KRAS- and BRAF-mutant colorectal cancer cells. Multiparametric flow cytometry was performed on two colon cancer cell lines, HCT116 and HT29. Cells were treated with U0126, and phospho-specific antibodies were used to monitor ERK signaling. HCT116 and HT29 cells were treated with increasing amounts of U0126. The western blot analysis revealed that by increasing the amount of U0126 resulted in inhibition of phospho-ERK, in HCT116 and to a lesser degree in HT29 cells. Microarray profiling identified CYP1A1 and 1A2 overexpression in HT29 cells and that inhibition of CYP1A1 with α-naphthoflavone and furanfylline restored sensitivity to U0126 in HT29 cells. Combination of a CYP inhibitor with MEK/ERK inhibitor enhances the inhibitory effect on ERK in BRAF-mutant colon cancer cells.