Phenotype-dependent subtyping exposes high MYC activity as a targetable dependency in LuAd

ABSTRACT C-MYC (MYC) occupies a critical nexus of oncogenic signalling and deregulated expression of MYC is widespread across most human cancer types, suggesting that MYC should be an attractive target for therapeutic intervention. Although 30-40% of human Non-Small Cell lung cancers show low level amplification of c-MYC and genetic evidence has shown that c-Myc is a key downstream effector of KRas-driven lung tumourigenesis in mouse models, the functional contribution of MYC to human lung cancer remains unclear. We applied a phenotype-based classifier to the TCGA Lung Adenocarcinoma (LuAd) cohort and found that high MYC transcriptional activity identifies a subset of LuAd with significantly reduced survival. Application of the same methodology to a panel of genetically engineered mouse models identified multiple genotypes that give rise to the high MYC activity phenotype, disease positioning such models as reflective of a distinct subset of human LuAd. We show that high MYC activity predicts sensitivity to a small molecule dual-inhibitor of the MYC co-factors, EZH2 and G9A, HKMTi-1-005, and that treatment with HKMTi-1-005 strongly reduced MYC protein expression, induced B cell-mediated immune surveillance and suppressed growth of autochthonous KRasG12D-driven lung tumours. Statement of significance This work establishes the principle of indirectly targeting MYC in LuAd, via inhibition of associated enzymatic cofactors, EZH2 and G9A, and identifies a large subset of aggressive human LuAd with a high MYC activity signature that may benefit from this approach. Competing Interest Statement RB and MJF are authors of a patent concerning HKMTi-1-005. The remaining authors declare no conflicts of interest.