641P - A pan-ErbB family inhibitor, AF8c, promotes apoptosis by DR5/Nrf2 activation via ROS in colorectal cancer cells

Abstract

BackgroundMultifunctional, antiproliferative small molecules are deemed to offer pharmacodynamic and pharmacokinetic benefits over combination therapy, in addition to reducing toxicity, cancer resistance, and therapy costs. In this study, we conducted an in vitro cellular screen of our recently reported series of EGFR/HER2 inhibitors. MethodsCytotoxicity induced by AF8c was confirmed using WST-1 assay. An Annexin V-Fluorescein Isothiocyanate (FITC) Apoptosis Detection Kit, TUNEL assay, and Western blotting were carried out to invastigate apoptosis. A human phosphorylated kinase array was used to identify proteins differentially expressed between control cells and AF8c-treated cell lines. ROS generation was monitored by flow cytometry, confocal microscopy using dihydroethidium (DHE) and MitoSOX. For in vivo tumor xenograft study, four-week-old female BALB/c nude mice were injected subcutaneously with either HT29 Luc+ or HCT116 Luc+ cells (1 × 107 cells in 100μl PBS). When the tumor had reached approximately 100mm3 in size, the mice were randomly divided into three groups (n=8): DMSO-treated, treated with 10mg/kg AF8c, and treated with 20mg/kg AF8c. ResultsAnalysis of the AF8c mode of action in CRC cells revealed that it mediates apoptosis via the generation of endoplasmic reticulum (ER) stress and reactive oxygen species (ROS), as well as selective activation of nuclear respiratory factor 2 alpha subunit (Nrf2) and death receptor 5 (DR5), but not DR4. Silencing of DR5 attenuated the expression levels of Nrf2 and partially inhibited AF8c-induced apoptosis. Additionally, upregulation of Nrf2 by AF8c evoked apoptosis through a decrease in antioxidant levels. Treatment of mice with AF8c also resulted in the upregulation of DR5, Nrf2, and CHOP proteins, subsequently leading to a significant decrease in tumor burden. ConclusionsAF8c-induced apoptosis may be associated with DR5/Nrf2 activation through ER stress and ROS generation in CRC. These findings indicate that AF8c represents a promising polypharmacological molecule for the treatment of human CRC. Moreover, it could also be a potential starting point for the understanding of the structural features of quinazoline-based ErbB family inhibitors targeting the TRAIL cascade. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.