Abstract 155: MicroRNA ‘signature’ during estrogen-mediated mammary carcinogenesis
Authors: Munagala Radha , Vadhanam Manicka , Kausar Hina , Bansal Shyam Sunder , Aqil Farrukh , Jeyabalan Jeyaprakash , Ravoori Srivani , Gupta Ramesh 
Published: June 2012

MicroRNAs (miRNAs) play important role in a wide range of normal biological processes. Dysregulated miRNA expression has been reported with the development and progression of cancers, including breast cancer. The role of estrogens in regulation of cell proliferation and breast carcinogenesis is well known. Recent reports have associated several miRNAs with estrogen receptors in breast tumors. However, identification of miRNA ‘signature’ during estrogen-mediated carcinogenesis may be critical for understanding the effect of estrogen in human breast cancer, as well as for developing strategies for cancer chemoprevention. In this study we analyzed miRNAs at 3 weeks, 12 weeks close to the appearance of first palpable tumor and 28 weeks when tumor incidence reaches 85-90% following treatment of female ACI rats with 17ß-estradiol (E2) silastic implants. Total RNA from mammary tissues and tumors were isolated using mirVana microRNA kit and analyzed using Affymetrix GeneChip miRNAarray. This array had 351 rat specific miRNAs probes. E2 treatment resulted in significant up regulation or repression (2 fold change) of 33 miRNAs at two or more time points. A total of 9 (p&lt;0.00128), 8 (p&lt;0.00113) and 27 (p&lt;0.00384) miRNAs in E2 treated normal mammary tissue, and 73 (p&lt;0.01039) in tumor tissue were differentially expressed when compared to untreated samples from 3, 12, and 28 weeks time point, respectively, with false discovery rate (FDR) at 0.05. These miRNAs were used to predict potential target mRNAs using Partek software. Ingenuity pathway analysis was used to further predict the major functions of the target mRNAs and molecular pathways. Molecular mechanism of cancer was the top canonical pathway of putative target mRNAs at all the time points indicating influence of E2 treatment in mammary carcinogenesis. The five top-ranking miRNAs (miR-196c, miR-34c, miR-375, miR-429 and miR-206) from microarray analysis were confirmed by real-time RT-PCR using Taqman microRNA assays; 5S RNA was used as reference for normalization. The expression of these miRNAs followed the same pattern whether evaluated by microarray or qPCR. These five miRNAs were further predicted to interact with mRNAs involved in estrogen-mediated (e.g. Src, PI3K, Akt, etc.) and EGF-mediated (e.g. Sos, Ras, MEK, etc.) breast cancer pathways. Thus, our results demonstrate miRNA modulations during the estrogen-mediated mammary carcinogenesis in an in vivo model in which, histologically, the mammary tumors resemble human breast cancer. Our future studies are aimed at finding the effect of naturally-occurring anti-cancer agent(s) on these candidate miRNAs to determine their translational importance (Supported by CA-118114, CA-125152 and Agnes Brown Duggan Endowment).

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 155. doi:10.1158/1538-7445.AM2011-155