Effect of Selective Androgen Receptor Modulator (SARM) on Gene Expression in Triple-Negative Breast Cancer Cells, MDA-MB-231-AR

RNA from tumors treated with vehicle or 30 mg/kg GTx-027 were pooled and subjected to microarray analysis. Genes that were increased or decreased by 2-fold or more were considered for further analyses. Unlike in prostate cancer, where AR agonists induce more genes than they repress, in MDA-MB-231-AR tumors, GTx-027 inhibited 2.5X the number of genes (1092 vs. 456) than it activated. Functional clustering of the genes indicated that GTx-027 modified more breast cancer genes than other pathway genes. Genes that regulate the function of others cancers, such as colorectal, lung, and oral, and metabolic diseases were also favorably altered by GTx-027. Breast cancer proliferative genes, such as aurora kinase, ERCC1, IGFBP3 were inhibited and growth inhibitory genes, such as NQO1, PTPRJ were activated by GTx-027. Many of the established androgen responsive-genes were also activated by GTx-027, indicating that breast cancer growth inhibitory role of GTx-027 evolved from its agonistic activity. A mixture of cells was suspended in 0.05 ml RPMI+10% FBS and 0.05 ml Matrigel/animal and was injected subcutaneously. Once the tumor size reached 200-300 mm3, the animals were randomized and treated orally with the indicated drugs formulated in Tween 80:Captex 200:water (0.8:0.2:9). Tumor volume and body weight were measured thrice weekly. At the end of study, animals were sacrificed, tumors excised, weighed, and stored for various analyses. RNA from tumors was isolated and verified qualitatively and quantitatively. Samples from each group (n=8; 100 ng/µl; total 1000 ng) were pooled and hybridized to Affymetrix human ST2.0 gene array. Data from the array were analyzed using Ingenuity Pathway Analysis software (IPA3).