Epigenetic repression of regulator of G‐protein signaling 2 promotes androgen‐independent prostate cancer cell growth

Abstract

G-protein coupled receptor (GPCR)-stimulated androgen-independent activation of androgen receptor (AR) contributes to acquisition of a hormone-refractory phenotype by prostate cancer. We previously reported that regulator of G-protein signaling (RGS) 2, an inhibitor of GPCRs, inhibits androgen-independent AR activation.1 Here, we show reduced RGS2 protein expression in human prostate cancer specimens compared to adjacent normal or hyperplastic tissue. Methylation-specific PCR analysis and bisulfite sequencing indicated that methylation of the CpG island in the RGS2 gene promoter correlated with RGS2 down-regulation in prostate cancer. In vitro methylation of this promoter suppressed reporter gene expression in transient transfection studies, whereas reversal of this promoter methylation with 5-aza-2′-deoxycytidine (5-Aza-dC) induced RGS2 re-expression in androgen-independent prostate cancer cells and inhibited their growth under androgen-deficient conditions. Interestingly, the inhibitory effect of 5-Aza-dC was significantly reduced by an RGS2-targeted short hairpin RNA, indicating that re-expressed RGS2 contributed to this growth inhibition. Restoration of RGS2 levels by ectopic expression in androgen-independent prostate cancer cells suppressed growth of xenografts in castrated mice. Thus, RGS2 promoter hypermethylation represses its expression and unmasks a latent pathway for AR transactivation in prostate cancer cells. Targeting this reversible process may provide a new strategy for suppressing prostate cancer progression by reestablishing its androgen-sensitivity.

Regulator of G protein signaling 2 is a key modulator of airway hyperresponsiveness

“…Immunohistochemistry was performed by using a polyclonal anti-RGS2 C-terminal peptide antibody as previously described. 18 The negative control used nonimmune rabbit IgG as the primary antibody. The intensity of RGS2 protein staining was determined as an average optical density by Image-Pro Plus in 5 randomly chosen airways for each sample.…”

“…Total RNA was extracted from monocytes, and procedures for quantitative real-time PCR of the RGS2 gene were described previously. 18,23 Immunohistochemistry analysis of human lung tissues Archived formalin-fixed, paraffin-embedded lung tissue blocks of subjects with asthma (n 5 3) and healthy controls (n 5 5) were from Dr Reynold A. Panettieri. Immunohistochemistry was performed by using a polyclonal anti-RGS2 C-terminal peptide antibody as previously described.…”

“…[13][14][15] RGS2 repression has been implicated in many human diseases such as hypertension, schizophrenia, and cancer. [16][17][18] RGS2 is abundantly expressed in human lungs, 19 and a recent study suggests that b2-adrenergic receptor agonist-induced RGS2 expression in ASM cells is a mechanism of bronchoprotection. 10 The human RGS2 gene maps to chromosome 1q31, and single-nucleotide polymorphisms at this region were strongly associated with asthma in children.…”

Gene Expression Profiling of Human Myeloid Leukemic MV4-11 Cells Treated with 5-Aza-2’-deoxycytidine

“…Previous gene expression analyses in several myeloid cell lines showed induction of RGS2 expression during granulocytic differentiation [22]. Further, it has been reported that epigenetic repression of RGS2 promotes prostate cancer cell growth [23]. Our microarray and QPCR data showed RGS2 is suppressed in leukemic cells and up-regulated after treatment of 5-aza-dC suggesting that targeting Wnt-signaling may be valuable in treating leukemia.…”

Regulator of G-protein signaling 2 (RGS2) in cardiology and oncology

“…RGS2 mRNA expression is lower in breast cancerous tissues than in normal tissues and research suggests that its overexpression exerts an inhibitory effect of breast cancer cell growth [18]. RGS2 is specifically downregulated in androgen-independent prostate cancer cells (AIPCC) and research found that RGS2 functioned as a growth suppressor for AIPCC [85,86]. An RGS2 decrease may contribute to chronic inflammation leading to metaplasia and may eventually lead to carcinogenicity in the skin keratinocytes [87].…”