MUC1-C IS ESSENTIAL FOR ESTABLISHING AND RECALLING INFLAMMATORY MEMORY OF OSIMERTINIB RESISTANCE IN NSCLC CELLS [H1975-RT_vs_H1975-OR]

MUC1-C is necessary for establishing and recalling resistance of NSCLC cells to osimertinib by driving an inflammatory memory responseThe oncogenic MUC1-C protein functions as a master regulator of NSCLC cell resistance to osimertinib by unclear mechanisms. We report that MUC1-C-mediated regulation of STAT1 and the interferon (IFN) type I/II pathways is necessary for establishing osimertinib resistance. Studies of osimertinib-resistant NSCLC cells selected for growth in the absence of drug further demonstrate that revertant cells are dependent on MUC1-C for recalling resistance to osimertinib. We show that establishing and recalling osimertinib resistance is dependent on activation of the MUC1 gene at (i) a proximal enhancer-like signature 1 (pELS-1) by MUC1-C and STAT1 and (ii) a pELS-2 by MUC1-C, JUN/AP-1 and PBAF. The MUC1 pELS regions function as memory domains for activation of MUC1-C and downstream STAT1 and IFN stimulated genes in conferring osimertinib resistance. Of clinical relevance, we report that the MUC1-C-driven inflammatory responses are induced in patient-derived, osimertinib-resistant MGH170 NSCLC cells with MET amplification. Our results further demonstrate that MGH170 cells are dependent on the MUC1-C-induced inflammatory response for resistance to the osimertinib and combination of osimertinib with the MET inhibitor capmatinib. These findings indicate that MUC1-C is necessary for establishing and recalling resistance of NSCLC cells to osimertinib by driving an inflammatory memory response. Comparison between H1975-OR, the osimertinib-resistant cell line, and H1975-RT cells, which had osimertinib removed for a longer period from H1975-OR and moderately regained sensitivity (H1975-OR vs H1975-RT). Treatment of H1975-OR = Osimertinib Treatment of H1975-RT = None