Abstract 4443: A post-transcriptional program of chemoresistance regulators in quiescent cancer cells
Authors: Lee Sooncheol , Truesdell Samuel S. , Bukhari Syed I. , Boukhali Myriam , Lee Dongjun , Mazzola Maria A. , Raheja Radhika , Langenbucher Adam , Haradhvala Nicholas J. , Lawrence Michael , Gandhi Roopali , Sweetser David A. , Haas Wilhelm , Vasudevan Shobha 
Published: August 2018

Abstract
Quiescent (G0) cells are a clinically relevant fraction in several cancers, which include dormant cancer stem cells, and resist clinical therapy. G0 cells reveal extensive changes in gene expression at the protein and translation levels. We previously identified that the translation mechanism is altered in G0 cancer cells. MicroRNAs, noncoding RNAs that target distinct mRNAs to alter gene expression—were found to associate with an important RNA-binding protein, and enable specialized functions in G0—where they recruit non-canonical translation factors to regulate specific mRNA translation. We find that G0 leukemic cells show similar proteome and translatome to cells isolated post-chemotherapy. These data suggest that specialized post-transcriptional and translational mechanisms in G0 leukemic cells regulate a distinct translatome to mediate chemoresistance.
To understand the role of post-transcriptional and translational regulation in chemoresistance, we compared global RNA, translational and proteome profiling in chemoresistant G0 acute monocytic leukemic (AML) cells. We find that chemotherapy or G0 induction leads to DNA damage responsive ATM and stress signaling, which alter post-transcriptional and translational mechanisms. ATM and stress activated p38 MAPK/MK2 increase AU-rich-element (ARE) bearing pro-inflammatory cytokine and immune gene mRNAs by regulating a key ARE RNA binding protein, and by activating STAT1/interferon pathway to alter canonical translation. AREs are present on 3'UTRs of critical, tightly regulated oncogenes and cytokines to post-transcriptionally control their expression. These changes permit translation of ARE bearing pro-inflammatory cytokine TNFα, and immune and cell-migration modulators that promote survival. Co-inhibiting p38 MAPK and TNFα that promote anti-apoptosis—prior to or alongwith chemotherapy—decreases chemoresistance in AML cell lines, in vivo, and in patient samples, without affecting normal cells. These studies reveal a pro-inflammatory subpopulation in AML that mediates chemoresistance, enabled by DNA damage- and stress-regulated post-transcriptional and translational mechanisms that are mediated by AU-rich-elements and a critical ARE RNA binding protein. Disrupting ARE regulation reduces TNFα and chemoresistance, revealing AREs and an important ARE RNA binding protein as key regulators of inflammation-mediated chemoresistance. These studies reveal the significance of post-transcriptional regulation of inflammation/immune gene-mediated chemoresistance.
Correspondence: vasudevan.shobha@mgh.harvard.edu
Citation Format: Sooncheol Lee, Samuel S. Truesdell, Syed I. Bukhari, Myriam Boukhali, Dongjun Lee, Maria A. Mazzola, Radhika Raheja, Adam Langenbucher, Nicholas J. Haradhvala, Michael Lawrence, Roopali Gandhi, David A. Sweetser, Wilhelm Haas, Shobha Vasudevan. A post-transcriptional program of chemoresistance regulators in quiescent 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 4443.