Genome-wide copy number analysis identifies AKT as a novel therapeutic target in pleural mesothelioma.

PURPOSE: Targeting aberrantly activated kinases in pleural mesothelioma (PM) is a promising therapeutic strategy. To identify potential candidates, we characterized recurrent chromosomal gains in PM and subsequently evaluated the specific inhibition of kinases that were activated by amplification and/or overexpression.

METHODS

42 primary PM were screened for chromosomal alterations using OncoScan technology and AKT expression was assessed using immunohistochemistry. The impact of Ipatasertib (pan-AKT inhibitor) and Sapanisertib (mTOR inhibitor) on cell survival, apoptosis induction, AKT/mTOR signaling, glycolysis was investigated in cell lines and primary cells. Preclinical anti-tumor efficacy was further assessed in a PDX model selected for AKT and mTOR expression.

RESULTS

OncoScan profiling identified eleven regions of significant chromosomal gains. Among them, 14q32.33 and 19q13.2 gains affected AKT1 and AKT2, members of the AKT serine/threonine protein kinase family. AKT1 protein was expressed in 66 % (60/91), AKT2 in 80 % (73/91) and AKT3 in 94 % (86/91) PM. 57 % PM co-expressed AKT1/AKT2/AKT3. Treatment with Ipatasertib impaired cell viability in PM cell lines and induced apoptosis. Combined treatment with Ipatasertib and Sapanisertib had a synergistic cytotoxic effect in all three cell lines and primary cells from two PM patients, even in Cisplatin-resistant cells. We also noted an improved response to the combination in a PDX model. Mechanistically, the combined treatment acted synergistically to inactivate AKT/mTOR downstream signaling, suppress glycolysis, and trigger ATP depletion.

CONCLUSIONS

Our study demonstrates recurrent activation of AKT kinases by copy number gains and upregulated expression in PM. Pharmacological AKT and mTOR inhibition is a promising therapeutic alternative for mesothelioma.