In this paper, we combine kinetic modelling and patient gene expression data analysis to elucidate biological mechanisms by which melanoma becomes resistant to the immune system and to immunotherapy.,To this end, we systematically perturbed the parameters in a kinetic model and performed a mathematical analysis of their impact, thereby obtaining signatures associated with the emergence of phenotypes of melanoma immune sensitivity and resistance.,Our phenotypic signatures were compared with published clinical data on pretreatment tumor gene expression in patients subjected to immunotherapy against metastatic melanoma.,To this end, the differentially expressed genes were annotated with standard gene ontology terms and aggregated into metagenes.,Our method sheds light on putative mechanisms by which melanoma may develop immunoresistance.,Precisely, our results and the clinical data point to the existence of a signature of intermediate expression levels for genes related to antigen presentation that constitutes an intriguing resistance mechanism, whereby micrometastases are able to minimize the combined anti-tumor activity of complementary responses mediated by cytotoxic T cells and natural killer cells, respectively.,Finally, we computationally explored the efficacy of cytokines used as low-dose co-adjuvants for the therapeutic anticancer vaccine to overcome tumor immunoresistance.
B-RAF is the most frequently mutated protein kinase in human cancers.1 The finding that oncogenic mutations in BRAF are common in melanoma2 followed by the demonstration that these tumors are dependent on the RAF/MEK/ERK pathway3 offered hope that inhibition of B-RAF kinase activity could benefit melanoma patients.,Herein, we describe the structure-guided discovery of PLX4032 (RG7204), a potent inhibitor of oncogenic B-RAF kinase activity.,Preclinical experiments demonstrated that PLX4032 selectively blocked the RAF/MEK/ERK pathway in BRAF mutant cells and caused regression of BRAF mutant xenografts.4 Toxicology studies confirmed a wide safety margin consistent with the high degree of selectivity, enabling Phase 1 clinical trials using a crystalline formulation of PLX4032.5 In a subset of melanoma patients, pathway inhibition was monitored in paired biopsy specimens collected before treatment initiation and following two weeks of treatment.,This analysis revealed substantial inhibition of ERK phosphorylation, yet clinical evaluation did not show tumor regressions.,At higher drug exposures afforded by a new amorphous drug formulation,4,5 greater than 80% inhibition of ERK phosphorylation in the tumors of patients correlated with clinical response.,Indeed, the Phase 1 clinical data revealed a remarkably high 81% response rate in metastatic melanoma patients treated at an oral dose of 960 mg twice daily.5 These data demonstrate that BRAF-mutant melanomas are highly dependent on B-RAF kinase activity.