PI3′-kinase inhibition forestalls the onset of MEK1/2 inhibitor resistance in BRAF-mutated melanoma

Abstract

Phosphatidylinositide 3′ (PI3′)-lipid signaling cooperates with oncogenic BRAFV600E to promote melanomagenesis. Sustained PI3′-lipid production commonly occurs via silencing of the PI3′-lipid phosphatase PTEN or, less commonly, through mutational activation of PIK3CA, encoding the 110-kDa catalytic subunit of PI3′-kinase-α (PI3Kα). To define the PI3K catalytic isoform dependency of BRAF-mutated melanoma, we used pharmacologic, isoform-selective PI3K inhibitors in conjunction with melanoma-derived cell lines and genetically engineered mouse (GEM) models. Although BRAFV600E/PIK3CAH1047R melanomas were sensitive to the antiproliferative effects of selective PI3Kα blockade, inhibition of BRAFV60..