Background: BRAFV600E-mediated MAPK pathway activation is associated in melanoma cells with IFNAR1 downregulation. IFNAR1 regulates melanoma cell sensitivity to IFN×alpha;, a cytokine used for the adjuvant treatment of melanoma. These findings and the limited therapeutic efficacy of BRAF-I prompted us to examine whether the efficacy of IFN×alpha; therapy of BRAFV600E melanoma can be increased by its combination with BRAF-I.Methods: BRAF/NRAS genotype, ERK activation, IFNAR1, and HLA class I expression were tested in 60 primary melanomatumors from treatment-naive patients. The effect of BRAF-I on IFNAR1 expression was assessed in three melanoma cell lines and in four biopsies of BRAFV600E metastases. The antiproliferative, pro-apoptotic and immunomodulatory activity of BRAF-I and IFN×alpha; combination was tested in vitro and in vivo utilizing three melanoma cell lines, HLA class I-MA peptide complex-specific T-cells and immunodeficient mice (5 per group for survival and 10 per group for tumor growth inhibition). All statistical tests were two-sided. Differences were considered statistically significant when the P value was less than .05. Results: The IFNAR1 level was statistically significantly (P ×lt; .001) lower in BRAFV600E primary melanoma tumors than in BRAF wild-type tumors. IFNAR1 downregulation was reversed by BRAF-I treatment in the three melanoma cell lines (P ×le; .02) and in three out of four metastases. The IFNAR1 level in the melanoma tumors analyzed was increased as early as 10 to 14 days following the beginning of the treatment. These changes were associated with: 1) an increased susceptibility in vitro of melanoma cells to the antiproliferative (P ×le; .04), pro-apoptotic (P ×le; .009) and immunomodulatory activity, including upregulation of HLA class I antigen APM component (P ×le; .04) and MA expression as well as recognition by cognate T-cells (P ×lt; .001), of BRAF-I and IFN×alpha; combination and 2) an increased survival (P ×gt; .001) and inhibition of tumor growth of melanoma cells (P ×lt; .001) in vivo by BRAF-I and IFN×alpha; combination. Conclusions: The described results provide a strong rationale for the clinical trials implemented in BRAFV600E melanoma patients with BRAF-I and IFN×alpha; combination.
ASJC Scopus subject areas
- Cancer Research