Current Insights into the Role of BRAF Inhibitors in Treatment of Melanoma

Melanomas represent only 4% of all skin cancers, but their mortality rate is more than 50 % of any other skin cancer. Alteration in genetic and environmental factors are the risk factors for melanoma development. The RAS/RAF/MEK/ERK or Mitogen-activated protein kinase (MAPK) pathway is activated in melanoma. BRAF activation is necessary to govern differentiation, proliferation, and survival. Mutations in BRAF were found in 80-90% of all melanomas. Over 90% of BRAF mutations occur at codon 600, and over 90% of them are BRAFV600E other common mutations are BRAFV600K, BRAFV600R, BRAF V600'E2', and BRAF V600D. Based on αC-helix and DFG motif (αC-helix-IN/DFG-IN), (αC-helix-IN/DFG-OUT), (αC-helix-OUT/DFG-IN) and (αC-helix-OUT/ DFG-OUT) are four structural types of inhibitors for targeting BRAF. Sorafenib, Vemurafenib, Dabrafenib, and Encorafenib are FDAapproved for the treatment of BRAF. Understanding melanoma pathogenesis, RAS/RAF/MEK/ERK or MAPK pathway, and BRAF conformations, mutations, the problems with FDA approved BRAF inhibitors will be important for new drug discovery, modification of existing BRAF barriers to improve target specific action, and prevent increasing response levels while minimizing toxicity.

Landscape of drug-resistance mutations in kinase regulatory hotspots

More than 48 kinase inhibitors (KIs) have been approved by Food and Drug Administration. However, drug-resistance (DR) eventually occurs, and secondary mutations have been found in the previously targeted primary-mutated cancer cells. Cancer and drug research communities recognize the importance of the kinase domain (KD) mutations for kinasopathies. So far, a systematic investigation of kinase mutations on DR hotspots has not been done yet. In this study, we systematically investigated four types of representative mutation hotspots (gatekeeper, G-loop, αC-helix and A-loop) associated with DR in 538 human protein kinases using large-scale cancer data sets (TCGA, ICGC, COSMIC and GDSC). Our results revealed 358 kinases harboring 3318 mutations that covered 702 drug resistance hotspot residues. Among them, 197 kinases had multiple genetic variants on each residue. We further computationally assessed and validated the epidermal growth factor receptor mutations on protein structure and drug-binding efficacy. This is the first study to provide a landscape view of DR-associated mutation hotspots in kinase's secondary structures, and its knowledge will help the development of effective next-generation KIs for better precision medicine.