Relaxin Promotes Prostate Cancer Progression

Abstract

Purpose:To understand the role of relaxin peptide in prostate cancer, we analyzed the expression of relaxin and its receptor in human prostate cancer samples, the effects of relaxin signaling on cancer cell phenotype in vitro, and the effects of increased serum relaxin concentrations on cancer progression in vivo. Experimental Design: The relaxin and its receptor leucine-rich repeat containing G proteinĉ oupled receptor 7 (LGR7) expression were studied by quantitative reverse transcription-PCR (11 benign and 44 cancer tissue samples) and by relaxin immunohistochemistry using tissue microarrays containing 10 normal and 69 cancer samples. The effects of relaxin treatment and endogenous relaxin/LGR7 suppression via short interfering RNA in PC-3 and LNCaP cells were analyzed in vitro. The effect of transgenic relaxin overexpression [Tg(Rln1)] on cancer growth and survival was evaluated in autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP). Results: The relaxin mRNA expression was significantly higher in recurrent prostate cancer samples. In tissue microarrays of the 10 normal tissues, 8 had low staining in epithelial cells, whereas only 1of 9 high-grade prostatic intraepithelial neoplasia lesions had low expression (P = 0.005) and only 29 of 65 cancers had low expression (P = 0.047). Stimulation with relaxin increased cell proliferation, invasiveness, and adhesion in vitro. The suppression of relaxin/LGR7 via short interfering RNAs decreased cell invasiveness by 90% to 95% and growth by 10% to 25% and increased cell apoptosis 0.6 to 2.2 times. TheTg(Rln1) TRAMP males had shorter median survival time, associated with the decreased apoptosis of tumor cells, compared with non-Tg(Rln1) TRAMP animals. Conclusions: Relaxin signaling plays a role in prostate cancer progression.Prostate cancer is the second most common malignancy in men in Western countries. After advancing to the androgenindependent stage, prostate cancer is unresponsive to androgen ablation therapy and is refractory (1). Identification of novel endogenous factors responsible for proliferation, survival, and migration of the prostate cancer cells may generate new therapeutic targets for treatment.Relaxin is a short circulating peptide hormone (2, 3). Two highly homologous genes on human chromosome 9 encode RLN1 and RLN2 peptides with predicted 82% identity at amino acid level. In the corpus luteum, the main source of circulating relaxin in females, only RLN2 is expressed (2 -4). Prostate is the main site of relaxin expression in men (5 -7). Relaxin, secreted from the prostate gland into seminal fluid, is the product of the RLN2 gene; however, the expression of both RLN1 and RLN2 genes has been detected in prostate at mRNA level (8). In nonprimates, there is only one orthologous RLN1 gene. Related peptides, such as RLN3 or INSL3, have a more restricted expression pattern (3). It has been shown that relaxin plays a role in connective tissue remodeling, suppression of fibrosis, dilation of blood vessels, and angiogenesis (2, 3). Th...

Interaction between angiotensin II and relaxin 2 in the progress of growth and spread of prostate cancer cells

“…In this study, it was observed that relaxin 2 improved maintenance of cellular viability and proliferation of both the LNCaP and PC3 prostate cancer cell lines. These results confirm earlier studies showing that this peptide hormone promotes the division of prostate cancer cells (6). Experimental studies report that greater changes of cell proliferation take place in the high AR expression cells (LNCaP) than low AR (B) The change in the level of MMP-2 and MMP-9 secretion determined by the gelatin zymography assay.…”

“…The peptides were used at a final concentration of 10 -8 M for all experiments. This concentration was selected on the basis of earlier research work and trial experiments (6). The medium, FBS and other culture supplements / reagents were purchased from Gibco (Thermo Fisher scientific, Inc.) unless otherwise specified.…”

“…High expression of relaxin 2 and the relaxin receptor LGR7/RXFP1 as well as angiotensin II and angiotensin receptor type 1 (AT1) was observed in tumor tissue compared to normal prostate tissue. Studies suggest that both the expression of the LGR7/ RXFP1 and AT1 receptors can be new early markers of metastatic potential in primary tumors (4)(5)(6)(7)(8).…”

Enhanced sensitivity to androgen withdrawal due to overexpression of interleukin-6 in androgen-dependent human prostate cancer LNCaP cells

“…For example, androgen withdrawal-induced marked downregulation of relaxin, VEGF, vimentin and BMP-6, involved in cancer progression (Soker et al, 2001;Dai et al, 2005;Thompson et al, 2006;Feng et al, 2007;Wei et al, 2008) as well as upregulation of cellular retinol binding protein 7 and interferon-g receptor, negatively regulating cancer progression (Kuppumbatti et al, 2001;Yang et al, 2008), in LNCaP/IL-6#1. In addition, DnaJ, acting as a cytoprotective chaperon in response to stress-induced apoptosis (Cajo et al, 2006), were upregulated in LNCaP/IL-6#1, which might be an adaptive change as observed in Akt and MAPK pathways after androgen deprivation.…”

“…In addition, expression levels of some genes associated with the progression of prostate cancer, such as relaxin, vascular endothelial growth factor (VEGF), vimentin and bone morphogenetic protein-6 (BMP-6) (Soker et al, 2001;Dai et al, 2005;Thompson et al, 2006;Feng et al, 2007;Wei et al, 2008), were significantly downregulated in LNCaP/IL-6#1 compared with LNCaP/Co. Overall, there are several genes listed in Table 1, which are known to have functions mediating cell growth, apoptotsis, and tumorigenesis, showing expression profiles that are reasonable for theoretically elucidating the molecular mechanism mediating enhanced sensitivity to androgen withdrawal by overexpression of IL-6.…”