Abstract 425: Fractionated radiation-induced tumor suppressor microRNAs in human prostate carcinoma cells.

Abstract

Abstract To understand the role of microRNAs (miRNA) in regulation of radiation-induced gene expression and to help define potential radiation-inducible targets, miRNA expression was studied in wild type p53 LNCaP and p53-mutated PC3 and DU145 cells. We have previously investigated the changes in the molecular profiles of tumor cells that were exposed to single dose (SD) versus fractionated radiation (MF) in vitro, and identified immune and stress response pathways that were induced by fractionated but not single dose radiation. Methods: Cells were exposed to 5Gy and 10Gy either as SD or MF radiation radiation. Microarray analyses were done using human Agilent miRNA Microarray Kit (V2). Data were analyzed using Gene Spring software. Validation of the miRNA expression and gene expression of miRNA targets was evaluated by real-time RT-PCR analysis. Target filter analysis of differentially expressed miRNAs (>1.5 fold change and p value<0.05) and their mRNA targets were done. Results: Microarray analyses revealed that radiation differentially expressed 84, 68 and 8 miRNAs with high confidence (>1.5fold change, p<0.05) in LNCaP, PC3 and DU145 cells, respectively. MF radiation affected more miRNAs than SD radiation in all cell lines. In LNCaP and PC3 cells, MF radiation upregulated tumor suppressor microRNAs miR-34a, miR-200, miR-135, miR-221 and let7. Baseline expression of miR-34a was markedly reduced in PC3 cells and DU145 cells compared to LNCaP cells. However, miR-34a was upregulated by fractionated irradiation in LNCaP and PC3 cells, but not in DU145 cells. RT_PCR analysis of 22 experimentally verified miR-34a targets, showed distinct expression patterns in PC3 and LNCaP cells 6 and 24 hours after radiation. An inverse correlation of NOTCH1, E2F5 and MDM4 expression was observed in PC3 cells 6 and 24 hours after MF but not in LNCaP cells. On the other hand, IFNB1 showed an inverse correlation only in LNCaP cells. Majority of the differences in the expression patterns of miR-34a targets were at 24 hours after MF. Conclusion: Differences in the miRNA expression exist between cell lines and after varying radiation regimens. Among the three prostate carcinoma cell lines, tumor suppressor miRNAs are upregulated after MF radiation in LNCaP and PC3 cells. Currently, we are in the process of modulating miRNAs and their targets to examine their effects on radio sensitivity. This work was supported by the Intramural Research Program of the NIH, NCI, CCR. Citation Format: C. Norman Coleman, Molykutty John-Aryankalayil, Adeola Y. Makinde, Sanjeewani T. Palayoor. Fractionated radiation-induced tumor suppressor microRNAs in human prostate carcinoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 425. doi:10.1158/1538-7445.AM2013-425