Abstract 4391: CD95L mRNA is toxic to cancer cells

Abstract

Abstract CD95/Fas ligand (CD95L) is best characterized for its role in activating extrinsic apoptosis through binding to its receptor, CD95. However, we recently reported that the CD95L mRNA is enriched in sequences that when converted to si- or shRNAs kill cancer cells through an RNAi-dependent mechanism. When loaded into the RNA Induced Silencing Complex (RISC), CD95L-derived small RNAs downregulate genes critical for cancer cell survival, eliciting a unique form of cell death we call Death Induced by Survival Gene Elimination (DISE). We now report that expression of full-length CD95L mRNA itself is toxic to cells. Acute expression of either wild-type CD95L mRNA in CD95-deficient cells or a CD95L mRNA with a premature stop codon in CD95 wild-type cells induces cell death. RNA-Seq analysis of small RNA reveals that CD95L mRNA is specifically processed into discrete clusters ~19-25 nucleotides long that map along the CD95L ORF. These clusters of CD95L sequences were bound by AGO proteins in cells about to die, suggesting that the mRNA may be killing cells through an RNAi-dependent mechanism. Generation of AGO-bound CD95L mRNA sequences does not appear to be dependent on the canonical miRNA biogenesis pathway, as clusters of CD95L mRNA were detectable in both Drosha and Dicer deficient HCT116 cells. We propose that CD95L mRNA is toxic to cells through processing and loading of small CD95L-derived RNA sequences into the RISC. Citation Format: William Putzbach, Ashley Haluck-Kangas, Quan Gao, Aishe A. Sarshad, Elizabeth Bartom, Austin Stults, Abdul S. Qadir, Denise M. Scholtens, Markus Hafner, Marcus Peter. CD95L mRNA is toxic to cancer cells [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 4391.