A Plastic EMP1+ to LGR5+ Cell State Conversion as a Bypass to KRASG12D Pharmacologic Inhibition in Metastatic Colorectal Cancer.

Inhibitors of the oncogene KRAS hold promise for treating metastatic colorectal cancer (mCRC). In this study, we show that a selective, covalent small-molecule inhibitor of the active (ON) conformation of RAS-G12D, RMC-9945, exerts durable disease control in preclinical colorectal cancer models of early liver metastasis, but its therapeutic activity was diminished in the advanced metastatic disease. RMC-9945-treated metastases underwent a transition from a poor prognosis-associated Emp1+ transcriptional state to a WNT-driven Lgr5+ stem cell-like state that withstands the absence of RAS-G12D activity. This cell state change occurred within hours of RAS(ON) inhibitor treatment through a shift in transcription factor usage that involved limited chromatin remodeling. Forced conversion of metastatic cells to the Lgr5+ state through RAS-G12D inhibition, followed by genetic ablation of this population, reduced metastatic burden and prolonged survival in a mouse mCRC model. Overall, these preclinical findings demonstrate a central role for oncogenic KRAS in governing cellular plasticity in mCRC. SIGNIFICANCE: We show that inhibition of oncogenic KRAS in preclinical models of advanced mCRC exerts a limited benefit, primarily due to the reversion of tumor cells to a stem cell-like state. Our findings highlight the context-dependent effects of oncogenic KRAS mutations and underscore cell plasticity as a therapeutic opportunity. See related commentary by Eng and Yilmaz et al., p. 201.