Autophagy (A) inhibition to enhance combined immunotherapy (I) and anti-EGFR treatment (E) in colorectal cancer (CRC).

Abstract

e14554 Background: Resistance to E impairs survival of metastatic CRC (mCRC) patients. The aim of this study is to assess the preclinical activity of triple inhibition of E, I and A in CRC. Methods: RKO and Colo-205 cell lines were treated with E [cetuximab (C) / panitamumab (P)] and/or I [pembrolizumab (PE) or nivolumab (NI) with/without ipilimumab (IPI)] and/or autophagy inhibitor 3-Methyladenine (3-MA). Phosphorylated EGFR (pEGFR), p62 (SQSTM1), MAP1LC3 (LC3B) and PARP protein levels were detected by Western blotting. Cell viability was determined by MTT Assay. Tumor volumes were determined from 3D cell culture on Corning Matrigel Matrix as well as the apoptotic cell death. Results: E+I combination compared to E alone decreased pEGFR and increased A activation through p62 downregulation and LC3II activation. Similar results were shown for cell viability/apoptosis. Cells were also treated with C or P combined with I plus 3-MA. Triple inhibition suppresses EGFR and blocks A. Compared to E+I, triple inhibition reduced more cell growth/viability. Caspase-3 activity was increased as well as proportion of apoptotic cells (Table). Conclusions: Τhese results indicate that the combinatorial inhibition of A, E and I represents a promising treatment strategy in mCRC that needs further testing. [Table: see text]