Targeting the relaxin hormonal pathway in prostate cancer.

Targeting the androgen signalling pathway has long been the hallmark of anti-hormonal therapy for prostate cancer. However, development of androgen-independent prostate cancer is an inevitable outcome to therapies targeting this pathway, in part, owing to the shift from cancer dependence on androgen signalling for growth in favor of augmentation of other cellular pathways that provide proliferation-, survival- and angiogenesis-promoting signals. This review focuses on the role of the hormone relaxin in the development and progression of prostate cancer, prior to and after the onset of androgen independence, as well as its role in cancers of other reproductive tissues. As the body of literature expands, examining relaxin expression in cancerous tissues and its role in a growing number of in vitro and in vivo cancer models, our understanding of the important involvement of this hormone in cancer biology is becoming clearer. Specifically, the pleiotropic functions of relaxin affecting cell growth, angiogenesis, blood flow, cell migration and extracellular matrix remodeling are examined in the context of cancer progression. The interactions and intercepts of the intracellular signalling pathways of relaxin with the androgen pathway are explored in the context of progression of castration-resistant and androgen-independent prostate cancers. We provide an overview of current anti-hormonal therapeutic treatment options for prostate cancer and delve into therapeutic approaches and development of agents aimed at specifically antagonizing relaxin signalling to curb tumor growth. We also discuss the rationale and challenges utilizing such agents as novel anti-hormonals in the clinic, and their potential to supplement current therapeutic modalities.

Relaxin receptor antagonist AT-001 synergizes with docetaxel in androgen-independent prostate xenografts.

Androgen hormones and the androgen receptor (AR) pathway are the main targets of anti-hormonal therapies for prostate cancer. However, resistance inevitably develops to treatments aimed at the AR pathway resulting in androgen-independent or hormone-refractory prostate cancer (HRPC). Therefore, there is a significant unmet need for new, non-androgen anti-hormonal strategies for the management of prostate cancer. We demonstrate that a relaxin hormone receptor antagonist, AT-001, an analog of human H2 relaxin, represents a first-in-class anti-hormonal candidate treatment designed to significantly curtail the growth of androgen-independent human prostate tumor xenografts. Chemically synthesized AT-001, administered subcutaneously, suppressed PC3 xenograft growth by up to 60%. AT-001 also synergized with docetaxel, standard first-line chemotherapy for HRPC, to suppress tumor growth by more than 98% in PC3 xenografts via a mechanism involving the downregulation of hypoxia-inducible factor 1 alpha and the hypoxia-induced response. Our data support developing AT-001 for clinical use as an anti-relaxin hormonal therapy for advanced prostate cancer.

Factors associated with recent HIV testing among younger gay and bisexual men in New Zealand, 2006-2011.

BACKGROUND: Understanding HIV testing behaviour is vital to developing evidence-based policy and programming that supports optimal HIV care, support, and prevention. This has not been investigated among younger gay, bisexual, and other men who have sex with men (YMSM, aged 16-29) in New Zealand. METHODS: National HIV sociobehavioural surveillance data from 2006, 2008, and 2011 was pooled to determine the prevalence of recent HIV testing (in the last 12 months) among YMSM. Factors associated with recent testing were determined using manual backward stepwise multivariate logistic regression. RESULTS: Of 3,352 eligible YMSM, 1,338 (39.9%) reported a recent HIV test. In the final adjusted model, the odds of having a recent HIV test were higher for YMSM who were older, spent more time with other gay men, reported multiple sex partners, had a regular partner for 6-12 months, reported high condom use with casual partners, and disagreed that HIV is a less serious threat nowadays and that an HIV-positive man would disclose before sex. The odds of having a recent HIV test were lower for YMSM who were bisexual, recruited online, reported Pacific Islander or Asian ethnicities, reported no regular partner or one for >3 years, were insertive-only during anal intercourse with a regular partner, and who had less HIV-related knowledge. CONCLUSION: A priority for HIV management should be connecting YMSM at risk of infection, but unlikely to test with appropriate testing services. New generations of YMSM require targeted, culturally relevant health promotion that provides accurate understandings about HIV transmission and prevention.

Iron content of Cambodian foods when prepared in cooking pots containing an iron ingot.

OBJECTIVES: To investigate the effect of cooking with an iron ingot on the iron content of several water and Cambodian food preparations. METHODS: Various food and water samples were prepared, in replicate, in glass and aluminium pots with and without an iron ingot. The samples were subjected to iron content analysis using standard ICP-OES procedures. RESULTS: Prepared with an ingot, the iron content was 76.3 µg iron/g higher in lemon water, 32.6 µg iron/g higher in pork soup and 3.3 µg iron/g higher in fish soup, than in the same foods prepared without an ingot. Acidity of the food samples was positively associated with iron leaching. CONCLUSIONS: Even when taking into account the low bioavailability of contaminant iron, approximately 75% of the daily iron requirement can be met by consuming 1L of lemon water prepared with an iron ingot. Its use may be a cheap and sustainable means of improving iron intake for those with iron-deficient diets.

Iron-deficiency anaemia in rural Cambodia: community trial of a novel iron supplementation technique.

BACKGROUND: More than 3.5 billion people are affected by iron-deficiency anaemia (IDA). Previous studies have shown that the use of iron pots in daily cooking ameliorates IDA. We report a study on the use of a novel treatment to address IDA in rural women in Cambodia, where the use of iron pots is not common. METHODS: A community-wide randomized controlled trial was conducted in the village of Preak Ruessei, Kandal Province, Cambodia. Rural women (n = 189) were enrolled and randomly assigned by household to one of three groups: (i) control, (ii) iron treatment with no follow-up and (iii) iron treatment with follow-up visits to provide IDA education. Haemoglobin, serum iron and C-reactive protein concentrations were measured at baseline, 3 and 6 months. A reusable fish-shaped iron ingot was distributed to the two treatment groups and participants were directed to use them daily for cooking. We hypothesized that iron from the ingot would leach iron into food providing an effective iron source. RESULTS: Blood iron levels were higher in women in the iron fish plus follow-up at 3 months compared with controls, but this was not maintained. At 6 months, haemoglobin and serum iron had fallen in all groups and the proportion of anaemic women had increased. CONCLUSIONS: This study shows that the iron ingot was effective in the short but not longer-term against IDA. Though a novel treatment option, further research is warranted to determine bioavailability of leached iron and whether or not the surface area is large enough for sufficient iron leaching.

Analog of H2 relaxin exhibits antagonistic properties and impairs prostate tumor growth.

Hormone antagonists can be effective tools to delineate receptor signaling pathways and their resulting downstream physiological actions. Mutation of the receptor binding domain (RBD) of human H2 relaxin (deltaH2) impaired its biological function as measured by cAMP signaling. In a competition assay, deltaH2 exhibited antagonistic activity by blocking recombinant H2 relaxin from binding to receptors on THP-1 cells. In a flow cytometry-based binding assay, deltaH2 demonstrated weak binding to 293T cells expressing the LGR7 receptor in the presence of biotinylated H2 relaxin. When human prostate cancer cell lines (PC-3 and LNCaP) were engineered to overexpress eGFP, wild-type (WT) H2, or deltaH2, and subsequently implanted into NOD/SCID mice, tumor xenografts overexpressing deltaH2 displayed smaller volumes compared to H2 and eGFP controls. Plasma osmolality readings and microvessel density and area assessment suggest that deltaH2 modulates physiological parameters in vivo. In a second murine model, intratumoral injections of lentivectors engineered to express deltaH2/eGFP led to suppressed tumor growth compared to controls. This study provides further evidence supporting a role for H2 relaxin in prostate tumor growth. More importantly, we report how mutation of the H2 relaxin RBD confers the hormone derivative with antagonistic properties, offering a novel reagent for relaxin research.

Central effects of long-term relaxin expression in the rat.

A recombinant adenovirus containing the human H2 preprorelaxin (hH2) cDNA and a reporter gene was coinjected with a transactivator virus (Ad-tTA) into the lateral cerebral ventricles of female rats. Cardiovascular effects were measured over a 21-day period. Circulating vasopressin in the periphery was significantly greater (P < .0001) in the relaxin-treated group throughout the experimental period, compared with controls. There was a significant decrease in plasma osmolality (P < .05) by approximately 10 mmol/L in the treated group by day 14. Immunofluorescence for hH2 present in cryosections showed rAd transduction and hH2 expression from ependymal cells of the ventricular system. Adenovirus-mediated delivery of hH2 to the brain is capable of producing bioactive relaxin that affects cardiovascular parameters.

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.

Adenovirus-mediated expression of human prorelaxin promotes the invasive potential of canine mammary cancer cells.

This study reports the characterization of a recombinant adenoviral vector containing a tetracycline-regulatable promoter, driving the bicistronic expression of the human H2 preprorelaxin (hH2) cDNA and enhanced green fluorescent protein, via an internal ribosomal entry site. An hH2 ELISA was used to measure the secreted levels of recombinant hH2 in transfected canine (CF33.Mt) and human (MDA-MB-435) mammary cancer cell lines over a 6-d period; secreted peptide peaked on d 2 and 4 for the canine and human cell types, respectively. An unprocessed hH2 immunoreactive form of approximately 18 kDa was identified by Western blotting analysis and confirmed by mass spectrometry, suggesting that prorelaxin remains unprocessed in these cell types. The biological activity of the adenovirally expressed human prorelaxin was measured in the established human monocytic cell line THP-1 cAMP ELISA and in an in vitro Transwell cell migration system. Exogenous recombinant hH2 and adenovirally-mediated delivery of prorelaxin to CF33.Mt cells conferred a significant migratory action in the cells, compared with controls. Cell proliferation assays were performed to discount the possibility that the effect of relaxin was mitogenic. Thus, we have demonstrated that prorelaxin has the ability to facilitate cell migration processes exclusive of its ability to stimulate cell proliferation. In validating this adenovirus-based system, we have created a potential tool for further exploration of the physiology of relaxin in mammalian systems.