Abstract 2841: Her2/neu expression as potential marker of regorafenib resistance in CRC

Nature Reviews Clinical Oncology, (2017). doi:10.1038/nrclinonc.2017.43 Jason J. Luke 0 0 2017-03-27T13:39:00Z 2017-11-29T14:35:00Z 1 312 1781 14 4 2089 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0cm; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Regorafenib is a multikinase inhibitor currently approved for the treatment of chemorefractory mCRC patients. No predictive biomarkers of efficacy have been identified. We recently reported that amplification or mutations in HER-2/neu might predict resistance to regorafenib in a small cohort of patients treated with Regorafenib. We therefore sought to better investigate the role of HER-2/neu in response to Regorafenib in preclinical and clinical models. Short-term proliferation assay with Regorafenib was performed in a panel of CRC cell lines. Basal protein expression of total and phospho Her2 were analized by WB analysis. RPPA data from MD Anderson cell lines project were used for external validation of total and phospho HER-2/neu. Sperman correlation was applied to correlate the expression levels of total and phospo HER2/neu and IC50 to Regorafenib. HT29 CRC cell line (HT29) was made resistant to Regorafenib (HT29R). WB analysis of basal levels of proteins of the EGFR and Her2 axis were investigated in both HT29 and HT29R. Moreover, HT29 and HT29R were treated with EGFR inhibitors, Her2/neu inhibitors, MAPK and PIk3Ca inhibitors. Apoptosis was perfromed by FACs analysis by using Annexin-V staining. We found a negative correlation between pHer2 expression and response to Regorafenib in both our data set of CRC cell lines and in the MD Anderson panel. Overexpression of all the epitelial markers of the EGFR and HER2/neu axis was observed in HT29R as compared to HT29. This translated to an increased sensitivity and apoptosis to Trastuzumab in HT29R as compared to HT29 (IC50 with 50 times fold change) and PIk3Ca inhibitor (IC50 with 5 times fold change). No differences of IC50 were observed with other inhibitors. Moreover, combined treatment with Trastuzumab and PIk3Ca inhibitor induced significantly early and late apoptosis in HT29R as compared to HT29. Our preliminary data indicate pHer2 levels to be predictive of resistance to Regorafenib in CRC. Functional work and IHC analysis of CRC patients treated with Regorafenib is ongoing and will be presented. Citation Format: Loredana Vecchione, Stefania Napolitano, Valentina Belli, Erika Martinelli, Nunzia Matrone, Christophe Hapke, Ulrich Keilholz, Josep Tabernero, Fortunato Ciardiello, Teresa Troiani. Her2/neu expression as potential marker of regorafenib resistance in CRC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2841.