LSD1 inhibition attenuates targeted therapy-induced lineage plasticity inBRAFV600Ecolorectal cancer

AbstractBRAFactivating mutations occur in approximately 10% of metastatic colorectal cancer (CRCs) and are associated with worse prognosis due to an inferior response to standard chemotherapy. Standard of care for patients with refractory metastaticBRAFV600ECRC is treatment with BRAF and EGFR inhibitors. However, responses are not durable. Lineage plasticity to neuroendocrine cancer is an emerging mechanism of targeted therapy resistance in several cancer types.Enteroendocrine cells (EECs), the neuroendocrine cell of the intestine, are uniquely present inBRAFV600ECRC as compared toBRAFwildtype CRC. Here, we demonstrated that combined BRAF and EGFR inhibition enriches for EECs in several models ofBRAFV600ECRC. Additionally, EECs and other secretory cell types were enriched in a subset ofBRAFV600ECRC patient samples following targeted therapy. Importantly, inhibition of the lysine demethylase LSD1 with a clinically relevant inhibitor attenuated targeted therapy-induced EEC enrichment through blocking the interaction of LSD1, CoREST2 and STAT3.Statement of SignificanceOur findings that BRAF plus EGFR inhibition induces lineage plasticity inBRAFV600ECRC represents a new paradigm for how resistance to BRAF plus EGFR inhibition occurs and our finding that LSD1 inhibition blocks lineage plasticity has the potential to improve responses to BRAF plus EGFR inhibitor therapy in patients.