The combination of PI3Ki and MEKi as a promising treatment option for melanoma patients with NRAS-mutated tumors

Background: Introduction: In recent years, new therapeutic approaches such as immune checkpoint inhibitors and targeted therapies have improved the survival rate of melanoma patients.However, response rates are limited and resistance to immunooncology therapies is a major challenge.The PI3K/AKT signaling pathway is deregulated in 70% of melanomas and contributes to the development of resistance, making PI3K a promising target for inhibitor treatment.In particular, the combination of PI3K and MEK inhibitors could be an effective option, as far as MEKi is the only targeted treatment option for patients with NRAS mutated tumors available.Methods: Methods: To investigate the effects of the PI3Ki and the MEKi on NRAS mutated cell lines the viability and apoptosis induction of were analyzed via MUH assay, cell cycle analysis and expression of cleaved Caspase 3 and cleaved PARP.In vivo, NSG mice were subcutaneously injected into the right flank with NRAS mutated melanoma cells and the tumor-bearing mice were treated via oral gavage with alpelisib (30 mg/kg bodyweight daily), trametinib (0,3 mg/kg bodyweight daily), or both treatments combined for 4 weeks.The efficacy and toxicity were analyzed by measuring the respective tumor sizes and mouse weights accompanied by histological analysis of the protein levels of phospho-ERK (as a marker for MAPK pathway activation) and cleaved PARP (as a marker for apoptosis).Results: Results: In monotherapy, the PI3K inhibitor alpelisib (BYL719), an alpha-specific inhibitor, has limited antitumor activity.However, the combination treatment of PI3K and MEK inhibitor resulted in effective growth inhibition and apoptosis induction in the tested cellular melanoma models, surpassing the effect of MEK inhibition as monotherapy.In the in vivo mouse setting, the combination therapy was able to reduce tumor growth and even significantly prolong overall survival in the NRAS-mutated model.Conclusions: Conclusion: These data indicate that the combination of PI3K inhibitors with MEK inhibitors may represent a new therapeutic option for melanoma patients with NRAS-mutated tumors.