Abstract 2991: Global analysis of miR-210 and miR-21 dysregulation and direct targeting in thyroid cancer during hypoxia

Abstract Introduction: Hypoxia is frequent in solid tumors and stabilizes Hypoxia Inducible Factor-1 (HIF-1). HIF-1, in turn, activates several cellular pathways that promote tumor growth and resistance to chemotherapy. MicroRNA (miRNA) miR-210 is a direct HIF-1 target. HIF-1 binds to a Hypoxia-Response Element (HRE) in the miR-210 promoter, up-regulating its expression. miR-21 is the most widely reported oncogenic miRNA in cancer. miRNAs complexed with Argonaute-2 (AGO2) bind target mRNAs to inhibit translation. Given that a single miRNA can have hundreds of predicted mRNA targets, we sought to identify mRNA targets of miR-210 and miR-21. Identifying dysregulated target genes of miR-210 and miR-21 may highlight new therapeutic targets. Methods: The SW1736 (anaplastic thyroid cancer) cell line was cultured at 2% (hypoxic) or atmospheric (normoxic) O2 for 24 or 48hrs. HIF-1α accumulation relative to normoxia was analyzed by Western blot. miR-210-3p expression was measured relative to normoxia by RT-qPCR. Small and total RNA-sequencing was performed to identify additional differentially expressed miRNAs and mRNAs in hypoxia after 48hrs. To identify direct miRNA targets, SW1736 cells were cross-linked by UV irradiation after 48hrs of normoxic or hypoxic conditions. AGO2 covalently cross-linked to miRNA and target mRNAs were purified by immunoprecipitation after DNA and RNA digestion. miRNA and target mRNAs protected by AGO2 were ligated to generate chimeric miRNA: mRNA molecules followed by sequencing. miRNA: mRNA chimeras were analyzed using the SCRAP bioinformatic pipeline. Results: miR-210-3p expression was up-regulated by ~11-fold at 24hrs and ~19-fold at 48hrs, which was consistent with increased HIF-1α protein levels assessed by Western blot. miR-210-3p and HIF-1α levels were highest after 48hr of hypoxia relative to normoxia. Small RNA-seq showed that miR-210-3p was the only miRNA significantly up-regulated (2-fold) in hypoxia (48hr) in SW1736. Further, miRNA: mRNA chimeric sequencing results confirmed that miRNAs primarily interacted with the 3’UTRs and coding sequences of mRNA. miR-210-3p was most abundant in hypoxia and found in chimeras with HIF-1α mRNA as well as some oncogenic and tumor suppressor transcripts involved in metabolism and mRNA processing. miR-21-5p was the most abundant chimera miRNA in both normoxia and hypoxia and was primarily bound to tumor suppressor mRNAs associated with cell cycle arrest, TGFB signaling, and inhibition of tumor invasion and migration. Conclusions: miR-210-3p and miR-21-5p elevated levels and interactions indicate hypoxia and malignancy in solid tumors including breast, thyroid, prostate, and lung. Further analysis of other miRNA: mRNA interactions and functional validation may aid in identifying novel therapies for solid tumors. Citation Format: Bonita H. Powell, William T. Mills, Andrey Turchinovich, Yongchun Wang, Martha A. Zeiger, Christopher B. Umbricht, Mollie K. Meffert, Kenneth W. Witwer. Global analysis of miR-210 and miR-21 dysregulation and direct targeting in thyroid cancer during hypoxia abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 2991.