Abstract A019: eIF4A and PDCD4 expression in TNBC underlies sensitivity to natural product translation inhibitor

Abstract

Abstract Despite recent advances in immunotherapy and adjuvant-therapy, resistance to cancer therapeutics is common and requires novel approaches. Moreover, highly aggressive triple-negative breast cancers lack effective targeted treatments. Deregulation of translation factors is associated with the increased proliferation of TNBC cells, heightened CSC activity, and poor patient outcomes. Thus targeting translation regulatory factors upregulated in TNBC is a promising approach to developing novel treatments. Pateamine A (PatA), a natural marine macrodiolide product, inhibits RNA cap-dependent translation by binding and sequestering the eukaryotic translation initiation factor eIF4A. eIF4A promotes the translation of polypurine-rich mRNA sequences, which are enriched within breast cancer oncogenes. Here we report the anticancer efficacy of novel PatA analogs we have synthesized against breast cancer cell lines. The PatA analogs exhibited selective cytotoxicity to breast and colorectal cancers compared to non-cancerous cells measured by Cell Titer-Blue viability studies. Novel analogs show greater antiproliferative potency against models of triple-negative than against human mammary epithelial cells (HMLE). To further elucidate eIF4A as a molecular target, we conducted analyses of patient tissue samples in the Cancer Genome Atlas (TCGA). Our analyses reveal the overexpression of eIF4A in tumor tissues compared to normal tissues and gene correlation studies reveal the upregulation of key co-expressed tumor drivers including beta-catenin, fibronectin, and epithelial-to-mesenchymal transition (EMT) markers such as SNAIL and SLUG. Further analyses show a downregulation of tumor suppressor protein PDCD4, an endogenous inhibitor of eIF4A, in cancer tissues. We have generated eIF4A shRNA knockdown and PDCD4 shRNA knockdown cell lines to uncover the eIF4A-PDCD4 regulatory axis across breast adenocarcinoma and colorectal adenocarcinoma cell types. We show that the loss of eIF4A attenuates the mesenchymal and stem-like phenotype of breast cancer stem cells revealed by phenotypic assays. Our results suggest that targeting translation initiator eIF4A is an effective approach against highly proliferative and metastatic breast cancer types. The presented findings underscore the potential of eIF4A as a promising molecular target and supports translational control as a viable approach against aggressive cancers. Citation Format: Alagu Subramanian, Haoran Xue, Kenneth G Hull, Daniel Romo, Joseph Taube. eIF4A and PDCD4 expression in TNBC underlies sensitivity to natural product translation inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A019.