PO-019 PTPN11 is a therapeutic target in KRAS mutant lung cancer

Abstract

IntroductionNon-Small-Cell Lung Cancer (NSCLC) accounts for approximately 85% of lung cancers, and mutations in the KRAS oncogene represent the most common driving event (Molina et al., Mayo Clin Proc 2008). So far, inhibition of the oncoprotein itself has proven difficult, and attempts to target downstream effectors have been hampered by the activation of compensatory resistance mechanisms (Bernards et al., Cell 2012). Notably, while MEK inhibition initially leads to ERK inactivation, P-ERK levels are quickly restored thanks to the upregulation of multiple growth factors receptors (Sun et al., Cell Reports 2014). Here we explored the possibility of targeting PTPN11 as a key mediator of receptor tyrosine kinase signalling in order to overcome intrinsic resistance to MEK inhibition.Material and methodsUsing a panel of 6 KRAS mutant NSCLC cell lines, we studied the biochemical and cell proliferation effect of combining the PTPN11 inhibitor SHP099 (Chen et al., Nature 2016) with the MEK inhibitor AZD6244. We confirmed our findings in CRISPR-based PTPN11 knockout clones of H2122 and H1944 cells. Importantly, we studied the effect of SHP099 in vivo in xenograft and PDX models, as well as in KRASLSLG12D p53fl/fl genetically engineered mouse model of NSCLC. To gain mechanistic insights into the effect of PTPN11 inhibition on mutant RAS activity, we used a panel of isogenic Rasless murine embryonic fibroblasts (Esposito et al., Semin Cancer Biol. 2018; NCI RAS Initiative) expressing human wild-type or mutant (G13D, G12C, G12D, G12V or Q61R) KRAS genes.Results and discussionsOur data show that depletion or inhibition of PTPN11 in KRAS mutant NSCLC cell lines invariably induces sensitivity to AZD6244. Surprisingly, in vivo models suggest that targeting PTPN11 is by itself sufficient to impair tumour growth, mainly due decreased RAS-GTP loading and induction of cellular senescence under growth factor-limiting conditions. Of note, our data suggest a correlation between the residual GTP hydrolysis capacity of the distinct KRAS mutants and their responsiveness to upstream regulators like PTPN11.ConclusionWhile in the past efforts have been focused on targeting KRAS downstream effectors, our data suggest that inhibiting upstream mediators like PTPN11 could be effective either alone or in combination with downstream inhibition. Our results suggest that targeting PTPN11 could be of clinical utility especially for tumours driven by KRAS mutants with high residual GTP hydrolysis capacity.