Relaxin-like factor expression in a human ovarian Sertoli-Leydig cell tumor

Distinct activation modes of the Relaxin Family Peptide Receptor 2 in response to insulin-like peptide 3 and relaxin

Relaxin family peptide receptor 2 (RXFP2) is a GPCR known for its role in reproductive function. It is structurally related to the human relaxin receptor RXFP1 and can be activated by human gene-2 (H2) relaxin as well as its cognate ligand insulin-like peptide 3 (INSL3). Both receptors possess an N-terminal low-density lipoprotein type a (LDLa) module that is necessary for activation and is joined to a leucine-rich repeat domain by a linker. This linker has been shown to be important for H2 relaxin binding and activation of RXFP1 and herein we investigate the role of the equivalent region of RXFP2. We demonstrate that the linker’s highly-conserved N-terminal region is essential for activation of RXFP2 in response to both ligands. In contrast, the linker is necessary for H2 relaxin, but not INSL3, binding. Our results highlight the distinct mechanism by which INSL3 activates RXFP2 whereby ligand binding mediates reorientation of the LDLa module by the linker region to activate the RXFP2 transmembrane domains in conjunction with the INSL3 A-chain. In contrast, relaxin activation of RXFP2 involves a more RXFP1-like mechanism involving binding to the LDLa-linker, reorientation of the LDLa module and activation of the transmembrane domains by the LDLa alone.

Relaxin family peptides and their receptors

There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.

H2 relaxin overexpression increasesin vivo prostate xenograft tumor growth and angiogenesis

Our study reports a preliminary investigation into the role of human H2 relaxin in prostate tumor growth. A luciferase-expressing human prostate cancer cell line, PC-3, was generated and termed PC3-Luc. PC3-Luc cells were transduced with lentiviral vectors engineering the expression of either enhanced green fluorescent protein (eGFP) or both H2 relaxin and eGFP in a bicistronic format. These transduced cells were termed PC3-Luc-eGFP and PC3-Luc-H2/eGFP, respectively. To gauge effects, PC3-Luc-H2/eGFP and PC3-Luc-eGFP cells were injected into NOD/SCID mice and monitored over 6 weeks. PC-3 tumor xenografts overexpressing H2 relaxin exhibited greater tumor volumes compared to control tumors. Circulating H2 relaxin levels in sera increased with the relative size of the tumor, with moderately elevated H2 relaxin levels in mice bearing PC3-Luc-H2/eGFP tumors compared to PC3-Luc-eGFP tumors. Zymographic analysis demonstrated that proMMP-9 enzyme activity was significantly downregulated in H2 relaxin-overexpressing tumors. An advanced angiogenic phenotype was observed in H2 relaxin-overexpressing tumors indicated by greater intratumoral vascularization by immunohistochemical staining of endothelial cells with anti-mouse CD31. Moreover, PC3-Luc-H2/eGFP tumors exhibited increased VEGF transcript by reverse-transcription PCR, compared to basal levels in control animals. Taken together, our study provides the first account of a potential role of H2 relaxin in prostate tumor development.

Sertoli-Leydig cell tumor - a rare androgen secreting ovarian tumor in postmenopausal women. Case report and review of literature

Sertoli-Leydig cell tumors (SLCT) constitute only 1-0.5% of all primary ovarian neoplasms. We report a SLCT in a postmenopausal woman aged 69 years. The physical examination revealed severe hirsutism. Basal hormonal evaluation showed high plasma testosterone and estradiol values, with suppressed plasma gonadotropins. Computer tomograph scan revealed a right ovarian tumor mass of 4,3/3 cm, confirming an androgen secreting ovarian tumor. The histopathological and immunocytochemical examination established the diagnosis of well differentiated Sertoli-Leydig cell tumor. The tumor was positive for cytokeratin KL 1 and S-100 protein and, in isolated tumor cells, positive for alpha-fetoprotein. Postsurgical evolution was favorable; controls after 6 months and 3,5 years showed marked reduction of hirsutism, normal plasma testosterone values and gonadotropins in normal postmenopausal range. We discuss the complex aspects of etiology and pathogenesis, the clinical and hormonal settings, the role of immunocytochemical markers in diagnosis, as well as the therapy and the prognostic features of this ovarian tumor.

Relaxin-like peptides in cancer

The members of the relaxin-like hormone family, relaxin and INSL3, also known as relaxin-like factor (RLF) or Leydig cell-derived insulin-like factor (LEY-I-L), are implicated in various mechanisms associated with tumor cell growth, differentiation, invasion and neovascularization. The recent discovery of the relaxin receptor LGR7 and the INSL3/relaxin receptor LGR8 has provided evidence of an auto/paracrine relaxin-like action in tumor tissues and enables the elucidation of the cellular pathways involved in the proposed functions of relaxin in tumor biology. Our review summarizes our current knowledge of the expression of relaxin and INSL3 in human neoplastic tissues and discusses the etiological roles of these heterodimeric peptide hormones in cancer. Discussion of possible cellular cascades involved in actions linking relaxin-like peptides and neoplasia include the role of relaxin-like peptides in tumor cell growth and differentiation; the effect of relaxin in stimulating the synthesis of the vasodilatory and tumor cell cytostatic and antiapoptotic molecule, nitric oxide; the potential ability of relaxin to upregulate vascular endothelial growth factor to promote angiogenesis and neovascularization and the concerted fine-tuned action of relaxin on the matrix metalloproteinases on the extracellular matrix to facilitate tumor cell attachment, migration and invasion.

Patients with ovarian cancer have elevated (51)Cr-EDTA plasma clearance early post-operatively

Plasma clearance of (51)Cr-EDTA (Clp(EDTA)) is widely used to determine glomerular filtration rate prior to carboplatin based chemotherapy. We have observed that many patients with ovarian cancer have elevated Clp in the early post-operative phase compared to later phases. The purpose of this study was to examine whether this observation reflects a systematic difference. We retrospectively analysed data from 53 patients who had undergone surgery for ovarian cancer. Twenty-six patients had Clp(EDTA) measured early after the operation (mean, 8 days (range, 3-16 days)) (early group), and 27 patients had Clp(EDTA) measured late post-operatively (mean, 32 days (range, 19-48 days)) (late group). Clp(EDTA) values was measured before the first, third and fifth course of chemotherapy. Additionally, age, height, weight, cancer stage, ascites and tumour histology were noted. Mean Clp(EDTA) in the early group was significantly higher than in the late group (104+/-4.4 vs 89+/-3.5 ml.min(-1) per 1.73 m(2); P =0.005). Clp(EDTA) declined significantly in the early group from the first measurement after the operation until measurement before the third course of chemotherapy but remained constant in the late group. Clp(EDTA) was not correlated to ascites, cancer stage or tumour histology. It is concluded that patients with ovarian cancer have significantly higher Clp(EDTA) in the early post-operative phase than similar patients with Clp(EDTA) measured late post-operatively.