Abstract B201: Identification of miRNA modulators to PARP inhibitor response.

Abstract

Abstract Many pre-clinical and clinical studies have shown that inhibitors of the DNA repair protein PARP can have potentiating effects when combined with DNA damaging treatment modalities such as IR and temozolomide. Moreover, PARP inhibitors can be used as an efficient single agent in treatment of tumors carrying homologous recombination (HR) gene defects such as BRCA1 and BRCA2. Genetic screens have previously been used to identify additional genetic deficiencies, which render tumor cells sensitive to PARP inhibitors. As yet, the contribution of microRNAs (miRNAs) to PARP inhibitor sensitivity has not been comprehensively studied. In this study our aim was to identify miRNA determinants of PARP inhibitor sensitivity and resistance, and in doing so potentially refine the eventual clinical use of these agents. The human genome encodes over 1000 well annotated miRNAs. We used a high throughput method of miRNA mimetic screening to identify novel modulators of PARP inhibitor response. The assay involved transfecting cells with a library of approximately 900 miRNA mimics in a 384-well plate format. 48 hours after transfection half of the cells were treated with PARP inhibitor Olaparib and the other half with the drug vehicle. We identified several miRNA mimetics that modulate the response to Olaprib. Hits were validated by long-term survival assays as well as by analyses of DNA damage foci. We used several strategies to determine the target genes of our hits. We performed westerns, qRT-PCR, luciferase reporter assays and immunoprecipitation assays and demonstrated several miRNAs involved in regulating the HR repair pathway. Genes that modulate the response to PARP inhibitors are often implicitly involved in controlling DNA repair by HR and thus frequently found to be mutated in cancers. Our future work will focus upon whether the miRNAs identified in our screen drive HR dysfunction in human tumors and could be used as biomarkers to direct the use of therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B201.