Abstract 4959: Targeting of the eukaryotic translation initiation factor 4A against breast cancer stemness

Abstract

Abstract Chemoresistance is a clinically significant issue in triple-negative breast cancer (TNBC) patients, leading to minimal residual disease. The surviving breast cancer stem cells (BCSCs) undergo multilineage differentiation and repopulate a more aggressive primary tumor leading to metastasis and subsequent mortality. Not only are BCSCs innately chemo/radioresistant but also contribute to therapy failure through interconversion between BCSCs and bulk tumor cells. Therefore, it is imperative to co-target BCSCs and bulk tumor cells simultaneously. Identifying novel molecular targets is key to eliminate both bulk tumor cells and BCSCs. The eukaryotic protein translation initiation machinery, the eIF4F complex, is a convergence point for many oncogenic signaling pathways. This complex plays a vital role in translation of many oncogenic mRNAs implicated in cell cycle, tumor progression, chemoresistance and metastasis. We have previously demonstrated that the mRNA helicase eIF4A1, of the eIF4F complex, might serve as a vulnerable node to kill TNBC cells. In the current study, we hypothesized that targeting of eIF4A1 would reduce/eliminate both bulk tumor cells and BCSCs and overcome chemoresistance. In order to evaluate the effects of targeting eIF4A1 in BCSCs, we isolated BCSCs based on aldehyde dehydrogenase activity and CD44 expression by Fluorescence Activated Cell Sorting and characterized for stemness. Through pharmacological targeting (Rocaglamide A) and genetic ablation (CRISPR-Cas9) of eIF4A1, we demonstrated that there was a statistically significant reduction in the self-renewal ability indicated by the reduction in primary and secondary mammosphere formation efficiency (MFE) of BCSCs, levels of the pluripotency transcription factors (SOX2, OCT4 and NANOG), expression of drug transporters (ABCG2, ABCB1 and ABCC1) and increased induction of apoptotic cell death. Overall, we demonstrated that targeting eIF4A1 is effective in eliminating BCSCs through reduction in the levels of stemness factors and drug transporters. This sets up a stage to employ small molecule inhibitors against eIF4A1 in co-targeting strategic therapies. Citation Format: Sangita Sridharan, Megan Robeson, Diwakar Tukaramrao Bastihalli, Cory Howard, Boopathi Subramaniyan, Augustus Tilley, Dayanidhi Raman. Targeting of the eukaryotic translation initiation factor 4A against breast cancer stemness [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4959.