Abstract 3080: PKM2 inhibition overcomes lapatinib resistance in HER2 overexpressing esophageal adenocarcinoma

Abstract Background: The human epidermal growth factor receptor 2 (HER2) is overexpressed in esophageal adenocarcinoma (EAC) and is a major target for EAC therapies. Lapatinib blocking HER1 and HER2 pathways, fails to improve patient survival. The molecular mechanisms of this lapatinib resistance are still unclear. We therefore explored the role of the glycolytic enzyme pyruvate kinase M2 (PKM2), a key regulator of the Warburg effect, in the lapatinib resistance mechanism of EAC cells. Methods: HER2/pHER2 expression status was evaluated by Western blot analysis in a panel of EAC cell lines (Flo-1, ESO26, OE19, OE33, SK-GT-2, ESO51, OACM5.1C, and LPR-OE19). The lapatinib-resistant OE19 (LPR-OE19) cell line was established from the OE19 cell line by intermittent exposure to increasing concentrations of lapatinib for a period over six months. We investigated the cell growth/migration inhibition and apoptotic signaling effects of treating HER2-overexpressing OE19, LPR-OE19, and OE33 cell lines with lapatinib, PKM2 inhibitor shikonin, and a chemotherapeutic agent nanoparticle albumin-bound paclitaxel (nab-paclitaxel) either alone or in combinations. Lactate production and cellular localization of PKM2/HSP40 were also detected. In addition, we explored the in-vivo antitumor efficacy following lapatinib, shikonin, and nap-paclitaxel mono and combination therapies in murine subcutaneous cell lines and patient-derived xenograft models of human EAC. Results: LPR-OE19 cells showed significantly reduced sensitivity to lapatinib-induced cell growth/migration inhibition and apoptosis compared to parent OE19 cells. Augmented cell growth/migration inhibition and apoptosis were observed in LPR-OE19 cells compared to parent OE19 cells when lapatinib was combined with shikonin. Knockdown of PKM2 in LPR-OE19 cells abolished the reduced sensitivity of lapatinib-induced cell growth inhibition and abolished the augmented cell growth inhibition response when lapatinib and shikonin were combined. Knockdown of HSP40 in OE19 cells enhanced PKM2 expression. LPR-OE19 cells showed enhanced lactate production compared to parent OE19 cells. PKM2 and HSP40 co-localize with each other in the cell nucleus, suggesting that PKM2 bound to molecular chaperone HSP40. In subcutaneous xenografts, shikonin displayed a remarkable tumor regression compared to that of control as monotherapy, and shikonin in combination with either lapatinib or nab-paclitaxel showed a significant enhancement effect of tumor regression. Conclusions: These data suggest that combination therapy of the PKM2 inhibitor shikonin with lapatinib or nab-paclitaxel should be tested as a potent option for lapatinib-resistant HER2-positive EAC patients and could be a novel treatment strategy for specific EAC. In addition, we suggest targeting HSP40-PKM2 interaction as an innovative therapeutic approach to overcome lapatinib resistance in EAC. Citation Format: Annie Ritter, Md Sazzad Hassan, Elizabeth Heffernan, Niranjan Awasthi, Urs von Holzen. PKM2 inhibition overcomes lapatinib resistance in HER2 overexpressing esophageal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3080.