Gene Expression profile of Cetuximab response in Colorectal Cancer Derived Xenograft

EGFR blockade by the monoclonal antibodies cetuximab or panitumumab causes objective tumor regressions in selected patients with metastatic colorectal cancer (mCRC). However, residual disease reservoirs almost invariably remain even after maximal response to therapy, leading to treatment failure and tumor relapse. Using mCRC patient-derived xenografts (PDXs), we observed that residual cancer cells surviving EGFR inhibition exhibited gene expression patterns reminiscent of a quiescent subpopulation of normal intestinal secretory precursors with Paneth-cell traits. These drug-tolerant cells had reduced expression of EGFR-activating ligands, consistent with lower EGFR dependence, and displayed higher HER2/HER3 pathway activity and persistent PI3K signaling. Mechanistically, cell fate reprogramming towards the Paneth cell-like phenotype was mediated by inactivation of YAP – a master regulator of intestinal epithelium recovery after injury – following cetuximab-induced neutralization of the MAPK cascade. Clinically, tumors from patients in whom cetuximab was not effective were enriched for markers of secretory commitment/Paneth-cell differentiation. In PDX therapeutic experiments, Pan-HER antibodies minimized residual disease burden and induced long-term tumor control after treatment discontinuation. We propose that tolerance to EGFR inhibition in CRC is typified by the adaptive disengagement of an in-built lineage program that jointly drives intestinal regenerative signaling and tumorigenesis. Further, our findings motivate therapeutic strategies to pre-emptively target residual disease before acquisition of irreversible resistance. 120 samples including treated and untreated CRC PDX in ex-vivo setting