Vemurafenib Sensitizes Melanoma Cells to Temozolomide by Downregulating MGMT Expression.

Abstract BackgroundThe alkylating agent temozolomide (TMZ) is widely used to treat melanoma in clinical practice. However, cells expressing the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) are highly resistant to this drug. Vemurafenib (vMF), a targeted BRAF kinase inhibitor, is applied to treat BRAF-V600 mutant metastatic melanoma. Studies have suggested that blocking this pathway prevents MGMT from affecting TMZ sensitization. However, reports of the use of the combination of vMF and TMZ in the treatment of melanoma are lacking.MethodsCell viability was detected by MTT assay, cell apoptosis was assayed by flow cytometry, and the mRNA level of the MGMT gene was measured by RT-qPCR. Western blotting, immunofluorescence staining were utilized to determine the expression of the protein. The pcDNA3.1-MGMT vector was transiently transfected to generate MGMT-overexpressing cells for experiments. A nude mouse malignant melanoma xenograft model was established for in vivo drug experiments.ResultsvMF increased TMZ-induced cytotoxicity by increasing DNA damage. vMF inhibited the MAPK/ERK signaling pathway and the mRNA and protein expression of the MGMT gene. vMF did not inhibit MGMT protein expression in A375-MGMT OE cells, and the vMF-induced sensitization effect was attenuated. Moreover, TMZ exposure activated ERK activity in malignant melanoma. The expression of MGMT and p-ERK1/2 was positively correlated in melanoma tissues.ConclusionvMF sensitized melanoma to TMZ by inhibiting the MAPK/ERK-MGMT pathway, and the combination of vMF and TMZ is expected to improve the clinical treatment effect on malignant melanoma.