Showing papers by "Thomas D. Schmittgen published in 2010"

MicroRNAs Are Mediators of Androgen Action in Prostate and Muscle

Abstract: Androgen receptor (AR) function is critical for the development of male reproductive organs, muscle, bone and other tissues. Functionally impaired AR results in androgen insensitivity syndrome (AIS). The interaction between AR and microRNA (miR) signaling pathways was examined to understand the role of miRs in AR function. Reduction of androgen levels in Sprague-Dawley rats by castration inhibited the expression of a large set of miRs in prostate and muscle, which was reversed by treatment of castrated rats with 3 mg/day dihydrotestosterone (DHT) or selective androgen receptor modulators. Knockout of the miR processing enzyme, DICER, in LNCaP prostate cancer cells or tissue specifically in mice inhibited AR function leading to AIS. Since the only function of miRs is to bind to 3′ UTR and inhibit translation of target genes, androgens might induce miRs to inhibit repressors of AR function. In concordance, knock-down of DICER in LNCaP cells and in tissues in mice induced the expression of corepressors, NCoR and SMRT. These studies demonstrate a feedback loop between miRs, corepressors and AR and the imperative role of miRs in AR function in non-cancerous androgen-responsive tissues.

Strong inverse correlation between microRNA-125b and human papillomavirus DNA in productive infection.

Abstract: Infection by the human papillomavirus (HPV) is a cause of cervical intraepithelial neoplasia (CIN) and cancer. microRNA (miRNA) in situ analysis of the transformation zone epithelia, the site of initial cervical HPV infection, showed that miRNAs let-7c, -99a, 26a, and 125b were the most abundantly expressed. In situ testing of CIN 1 showed a dramatic reduction in miR-125b expression in the koilocytes, the cytologic marker of productive HPV infection. A marked reduction in miR-125b was likewise observed in the HPV-infected cells of the condyloma acuminatum, verruca vulgaris, and epidermodysplasia verruciformis. Reverse transcriptase in situ polymerase chain reaction (PCR) showed that the pre-miRNA 125b was present in the koilocyte, suggesting direct inactivation of the mature miRNA. HEK cells transfected with only the antimiR-125b showed perinuclear halos equivalent to HPV-infected koilocytes. NIH 3T3 cells transfected with the HPV 16 full-length genome and mimetic miR-125b showed a marked reduction in viral DNA and protein synthesis by quantitative PCR and in situ-based analyses, respectively (P=0.002). Alternatively, cotransfection with anti-miR-125b and HPV 16 markedly increased HPV DNA (P=0.002). Sequence analyses showed strong homology between L2 of different HPV genotypes and miR-125b. Transfection with HPV 16 L2 resulted in a marked reduction in miR-125b levels in the NIH 3T3 cells. HPV L2-induced inactivation of miR-125b is associated with the classic cytologic changes of the koilocyte, and the exogenous application of mimetic miR-125b markedly inhibits HPV DNA synthesis.

miR-31: a master regulator of metastasis?

Abstract: Evaluation of: Valastyan S, Reinhardt F, Benaich N et al.: A pleiotropically acting microRNA, miR-31, inhibits breast cancer metastasis. Cell 137(6), 1032-1046 (2009). Several microRNAs (miRNAs) regulate various steps of the metastatic cascade; however, they typically regulate both metastasis-related genes and genes involved in proliferation, cell-cycle regulation or apoptosis. miR-31 was determined to regulate a number of metastasis-related genes in breast cancer cells and tissues. Using a variety of approaches, it was demonstrated that cellular levels of miR-31 correlated with the cell's ability to invade and metastasize; cells with increased levels of the miRNA were less metastatic. These studies were extended to patient's tissues, demonstrating that breast cancer patients with higher miR-31 expression, or lower expression of the miR-31 target genes, had prolonged survival. A miRNA that works pleiotropically to regulate invasion and metastasis has been identified, suggesting a new pathway for therapeutic intervention of metastasis in breast cancer.