Abstract 2031: Regulation of glucocorticoid receptor in multiple myeloma by microRNA

Abstract

Abstract Resistance to glucocorticoid-based therapies affects the treatment options of many diseases including Multiple Myeloma (MM). Glucocorticoids (GCs) are the most successful treatment for MM, causing apoptosis in the malignant cells. Unfortunately, patients ultimately become resistant to this therapy and despite the application of novel therapeutics, this disease is ultimately fatal. Expression of glucocorticoid receptor (GR) is required for response to therapy and patients who express higher levels of GR have improved survival. To examine the regulation of GR, our lab has previously established tissue culture cell lines from a myeloma patient who had been treated with GCs and become resistant to that treatment. From the initial patient isolate, we established a cell line that is sensitive to GCs (MM.1S) and two phenotypes of GC resistance (MM.1Re and MM.1RL). We hypothesize that miRNA expression in the GC resistant cells cause a decrease in GR expression. To test this hypothesis, we transfected both GC-sensitive and -resistant MM cells with a luciferase reporter construct containing the GR 3′UTR. We measured a decrease in luciferase activity in the GC resistant cells indicating that miRNAs are most likely involved in GR regulation. To identify which miRNAs may be responsible for this regulation, we used deep sequencing miRNAome analysis of the MM.1S, MM.1Re and MM.1RL cell lines. miRNAs more highly expressed in the GC-resistant cells and containing seed sequences which could target the GR 3′UTR were considered candidates. Expression of the candidate miRNAs was validated by Taqman qRT-PCR. GR regulation by candidate miRNAs was tested by transfection of MM.1S cells with miRNA mimics and the luciferase reporter expressing the GR 3′UTR. When exogenously expressed with the luciferase reporter, miR-130b is able to significantly decrease luciferase activity compared to controls as well as reducing the endogenous GR protein expression. In addition, miR-130b over expression partially blocks GC induced cell death, suggesting a role for this miRNA in the regulation of GR and in GC resistance in MM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2031.