Abstract 622: Rapid non-uniform adaptation to conformation-specific KRAS G12Cinhibition

Abstract

KRAS GTPases are activated in one-third of cancers and KRAS G12C is the most common activating alteration in lung adenocarcinoma. KRAS G12C-specific inhibitors (G12Ci) are in Phase-I clinical trials and early data show only partial responses in lung cancer patients. How cancer cells bypass inhibition, to prevent maximal responses to therapy, is not understood. Because KRAS G12C cycles between an active and inactive conformation, and the covalent G12Ci only bind to the latter, we tested whether isogenic cell populations respond non-uniformly by studying the effect of treatment at a single-cell resolution. Using single-cell RNA sequencing and a fluorescent quiescence biosensor, we show that shortly after treatment, most cancer cells are sequestered in a quiescent state with low KRAS activity, while a small population reactivates KRAS to resume proliferation. This rapid divergent response is due to synthesis of new, drug-free KRAS protein, resulting from increased KRAS transcription in response to suppressed MAPK signaling. Combining cell fate-specific gene expressions and results from a CRISPR-Cas9 screen, we identified that adaptive signals such as epidermal growth-factor receptor and aurora kinase A signaling modulate the heterogeneous response to treatment with G12Ci. These upstream signals help to maintain new KRAS G12C protein in its active, drug-insensitive state, which restores KRAS signaling and transcriptional output in a subset of cells to allow escape from G12Ci-induced quiescence. Cells without these adaptive changes (or cells where they are pharmacologically inhibited) remain sensitive to G12Ci treatment, because new KRAS G12C is either not available, or it exists in its inactive, drug-sensitive state. Combined inhibition of these adaptive signals along with KRAS G12C produced more potent antitumor effects in xenograft models. The direct targeting of KRAS oncoproteins has been a longstanding objective in precision oncology. Our study uncovers a flexible non-uniform fitness mechanism that enables groups of cells within a population to rapidly bypass the effect of treatment. This adaptive process must be overcome to maximize the therapeutic potential of conformation-specific KRAS G12C inhibitors in the clinic. Citation Format: Jenny Y. Xue, Yulei Zhao, Jordan Aronowitz, Trang T. Mai, Alberto Vides, Besnik Qeriqi, Dongsung Kim, Chuanchuan Li, Elisa de Stanchina, Linas Mazutis, Davide Risso, Piro Lito. Rapid non-uniform adaptation to conformation-specific KRAS G12Cinhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 622.

Molecular Biology and Therapeutic Perspectives for K-Ras Mutant Non-Small Cell Lung Cancers

“…ARS-1620 (a potent, orally bioavailable covalent inhibitor of KRAS c.34G > T (p.G12C), when combined with alisertib (AURKA inhibitor), was observed to have a significant synergistic effect in ARS-1620-refractory KRAS c.34G > T (p.G12C) mutant cancer. The mechanistic inhibition of AURKA has been shown not only to impair normal cell division and proliferation but also to affect KRAS–c RAF interaction, leading to a challenging activation of RAF [ 201 ].…”

“…Multiple SHP2 inhibitors are being investigated both as monotherapy and in combination with KRAS c.34G > T (p.G12C) inhibitors like RMC 4630, RMC 4550, RLY 1971, TNO15 [ 180 , 201 , 208 , 209 , 210 , 211 ], (clinicaltrials.gov NCT 04252339, NCT03114319, NCT04699188). A novel inhibition strategy into KRAS c.34G > T (p.G12C) therapeutic approaches has yielded a new target in the SOS1 catalytic domain that affects the EGFR/MAPK pathway.…”