Abstract 1972: LIN28 gene targets are key mediators of breast cancer disease processes

Abstract

Abstract LIN28 is an evolutionally conserved RNA-binding protein with critical functions in developmental timing, pluripotency and reprogramming. At the molecular level, most studies indicate that LIN28 modulates gene networks and biological processes by negatively regulating miRNA biogenesis and post-transcriptionally regulating mRNA translation. In addition, increasing evidence suggests that LIN28 is an oncogene, promoting cell growth in various cancers, including breast cancer; however the molecular mechanisms underlying these effects are not known. To provide mechanistic insights into how LIN28 modulates the gene networks that control breast cancer disease processes, we integrate next generation technologies, biochemical approaches and computational analysis to identify LIN28 mRNA targets. Our results demonstrated that endogenous LIN28 binds 843 mRNAs, ∼3.5% of the total human reference genome in breast cancer cells. Gene ontology analyses reveal that the genes targeted by LIN28 are enriched in those that control cell metabolism. Furthermore, using proteomics analysis, we identify heteronuclear ribonucleoprotein A1 (hnRNP A1), a protein with multiple roles in mRNA metabolism, as a LIN28 interacting partner. Importantly, hnRNP A1 is overexpressed and linked to increased cell proliferation and transformation in a wide variety of cancers, including breast cancer. Moreover, and consistent with the observation that majority of mRNAs bound by LIN28 are involved in metabolism, hnRNP A1 is known to regulate the expression of key enzymes that control metabolism in cancer cells. In-depth analysis of the transcriptomes of LIN28 and hNRNPA1 siRNA-treated cells reveal that these two proteins cooperate to regulate alternative splicing and the steady state mRNA expression of genes implicated in various aspects of breast cancer biology. Most notably, depleting LIN28 results in differential isoform expression of the ENAH gene, which is linked to breast cancer metastasis. In summary, by integrating genomic, biochemical and computational approaches, we identify a broad network of LIN28 targets that modulate cancer cell metabolism, cancer cell invasiveness and the immune response, processes that are hallmarks of breast cancer. Citation Format: Harriet K. Kinyamu, Jun Yang, Brian Bennett, Sara Grimm, Pierre Bushel, Trevor Archer. LIN28 gene targets are key mediators of breast cancer disease processes. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1972. doi:10.1158/1538-7445.AM2015-1972