Inhibition of anti-apoptotic BCL2 overcomes adaptive resistance to co-targeting of the protein kinase FAK and MEK in GNAQ-driven uveal melanoma

Abstract

Uveal melanoma (UVM) is the most common eye cancer in adults, with 50% of patients developing overt metastasis that often proves fatal. The majority of UVM harbor mutations in GNAQ or GNA11, encoding constitutively active Gαq proteins. Combined inhibition of MEK and FAK downstream of Gαq has shown promising effects in UVM cells by inducing apoptotic cell death, but resistance to this strategy can occur in the clinic. Here, we aimed to identify new targets to overcome resistance to MEK + FAK inhibition (FAKi + MEKi). Reverse-phase protein array (RPPA) analysis in UVM cells treated with FAKi + MEKi showed increased levels of pro-apoptotic proteins, such as PUMA and BIM, which promoted cell death. However, we observed an adaptive increase in anti-apoptotic proteins, including BCL2, upon FAK + MEK blockade. We generated UVM cells resistant to FAKi + MEKi by prolonged exposure. Whole-exome sequencing did not reveal relevant acquired mutations; instead, resistant cells exhibit increased BCL2 levels. Moreover, expression of a stable BCL2 mutant confers resistance to both FAKi + MEKi and FAKi+"RAF-MEK clamp" (avutometinib) treatment. Of direct translational relevance, we found that an approved BCL2 inhibitor (venetoclax) displays synergistic efficacy with FAK + MEK blockade and overcomes acquired resistance, including when combined with darovasertib, a dual PKC/PKN inhibitor limiting MEK and FAK signaling that is under clinical evaluation. Our findings suggest that resistance to FAKi + MEKi in UVM cells can be driven by an adaptive upregulation of the anti-apoptotic protein BCL2, and that, in turn, BCL2 inhibitors represent a promising precision-targeted strategy to overcome FAKi + MEKi treatment resistance and improve therapeutic outcomes.

Keywords: BCL2; FAK; MEK; avutometinib; darovasertib; resistance; uveal melanoma; venetoclax.