Immunocytochemical identification of a relaxin-like protein in gastrointestinal epithelium and carcinoma: a preliminary report

Innate immunity and non-Hodgkin's lymphoma (NHL) related genes in a nested case-control study for gastric cancer risk

Objective

Genetic variants regulating the host immune system may contribute to the susceptibility for the development of gastric cancer. Little is known about the role of the innate immunity- and non-Hodgkin’s lymphoma (NHL)-related genes for gastric cancer risk. This nested case-control study was conducted to identify candidate genes for gastric cancer risk for future studies.

Methods

In the Discovery phase, 3,072 SNPs in 203 innate immunity- and 264 NHL-related genes using the Illumine GoldenGateTM OPA Panel were analyzed in 42 matched case-control sets selected from the Korean Multi-center Cancer Cohort (KMCC). Six significant SNPs in four innate immunity (DEFA6, DEFB1, JAK3, and ACAA1) and 11 SNPs in nine NHL-related genes (INSL3, CHMP7, BCL2L11, TNFRSF8, RAD50, CASP7, CHUK, CD79B, and CLDN9) with a permutated p-value <0.01 were re-genotyped in the Replication phase among 386 cases and 348 controls. Odds ratios (ORs) for gastric cancer risk were estimated adjusting for age, smoking status, and H. pylori and CagA sero-positivity. Summarized ORs in the total study population (428 cases and 390 controls) are presented using pooled- and meta-analyses.

Results

Four SNPs had no heterogeneity across the phases: in the meta-analysis, DEFA6 rs13275170 and DEFB1 rs2738169 had both a 1.3-fold increased odds ratio (OR) for gastric cancer (95% CIs = 1.1–1.6; and 1.1–1.5, respectively). INSL3 rs10421916 and rs11088680 had both a 0.8-fold decreased OR for gastric cancer (95% CIs = 0.7–0.97; and 0.7–0.9, respectively).

Conclusions

Our findings suggest that certain variants in the innate immunity and NHL-related genes affect the gastric cancer risk, perhaps by modulating infection-inflammation-immunity mechanisms that remain to be defined.

Detection of RXFP1 receptors in skin biopsies from children with congenital adrenal hyperplasia: a preliminary report

OBJECTIVE

Relaxin may potentiate the effect of topical estrogen treatment to eradicate post-incisional scarring in congenital adrenal hyperplasia (CAH) patients undergoing genitoplasty. The aim of this study was to determine whether CAH skin is capable of responding to relaxin.

PATIENTS AND METHODS

Skin biopsies were obtained from four female CAH patients (aged 2-9 years; Prader 4-5, salt-wasting, 21-hydroxylase deficiency, Caucasian) during routine genitoplasty surgery and screened for relaxin receptors. All received corticosteroid and mineralocorticoid replacement therapy. Specimens were sectioned, mounted and screened for the presence of the putative H2 relaxin receptor using conventional two-antibody immunohistochemistry. Tissue controls were processed concurrently.

RESULTS

Tissue controls evidenced appropriate staining. Biopsies from CAH patients stained positively for RXFP1 expression while some variation between specimens was evident. Staining occurred adjacent to the basement membrane of the epithelium, localized to germinative basal keratinocytes.

CONCLUSION

Based on a limited patient sample, germinative keratinocytes in CAH patients appear competent to respond to relaxin perhaps topically applied. Given that relaxin downregulates collagen accretion and upregulates collagenases, its use may potentiate the effects of estradiol and abrogate post-incisional wound scarring. More research is needed to confirm or refute this thesis.

Relaxin's involvement in extracellular matrix homeostasis

Burgeoning evidence suggests that the hormone relaxin modulates collagen in the extracellular matrix of diverse tissues. In separate lines of study, we provide further substantiation of this hypothesis. Immunofluorescence was used to probe isolated fibroblasts derived from volar oblique ligament explant culture for vimentin, actin, RXFP1, and estrogen receptor beta. Ligaments were obtained as surgical waste from thumb reconstruction patients. Four specimens have been examined to date. Cells derived from these patients expressed vimentin and actin, consistent with fibroblast morphology. Putative fibroblasts derived from two of three female patients expressed RXFP1 receptors; the solitary male was negative. Given the small sample, however, the data are considered preliminary. Immunohistochemistry was used on frozen sections from 26 skin biopsies obtained from children undergoing genitoplasty. A subset of samples was also probed for transforming growth factor (TGF-beta1) and TGF-beta3. Appropriate controls were used. Finally, a subset of patient blood was assayed for relaxin by using an enzyme-linked immunosorbent assay-based method. The results showed RXFP1 receptor expression in the cells that populate the basement membrane in 96% of patients, regardless of gender. Most tissue expressed TGF-beta. Finally, serology suggested that relaxin was detectable in these children. Our two lines of research provide additional evidence for the diverse tissue tropism of relaxin. In particular, connective tissues as diverse as ligaments and basal lamina keratinocytes express RXFP1. These data lend support to our contention that relaxin affects ligament integrity and wound healing.

Relaxin becomes upregulated during prostate cancer progression to androgen independence and is negatively regulated by androgens

BACKGROUND

Relaxin is a potent peptide hormone normally secreted by the prostate. This study characterized relaxin expression during prostate cancer progression to androgen independence (AI), and in response to androgens.

METHODS

The prostate cancer cell line, LNCaP, was assayed by microarrays and confirmatory Northern analysis to assess changes in relaxin levels due to androgen treatment and in LNCaP xenografts following castration. Relaxin protein levels were examined by immunohistochemistry (IHC) in tissue microarrays of human prostate cancer samples following androgen ablation.

RESULTS

Relaxin levels decreased in a time and concentration-dependent manner due to androgens in vitro, and increased in xenografts post-castration. Relaxin increased in radical prostatectomy specimens after 6 months of androgen ablation and in AI tumors, was highest in bone metastases.

CONCLUSIONS

Relaxin is negatively regulated by androgens in vitro and in vivo, which correlates to clinical prostate cancer specimens following androgen ablation. The role of relaxin in angiogenesis and tissue remodeling suggests it may contribute to prostate cancer progression.

The R273H p53 mutation can facilitate the androgen-independent growth of LNCaP by a mechanism that involves H2 relaxin and its cognate receptor LGR7

Mutations in p53 occur at a rate of approximately 70% in hormone-refractory prostate cancer (CaP), suggesting that p53 mutations facilitate the progression of CaP to androgen-independent (AI) growth. We have previously reported that transfection of p53 gain of function mutant alleles into LNCaP, an androgen-sensitive cell line, allows for AI growth of LNCaP in vitro. We herein confirm the in vivo relevance of those findings by demonstrating that the R273H p53 mutation (p53(R273H)) facilitates AI growth in castrated nude mice. In addition, we demonstrate that H2 relaxin is responsible for facilitating p53(R273H)-mediated AI CaP. H2 relaxin is overexpressed in the LNCaP-R273H subline. Downregulation of H2 relaxin expression results in significant inhibition of AI growth, whereas addition of recombinant human H2 relaxin to parental LNCaP promotes AI growth. Inhibition of AI growth was also achieved by blocking expression of LGR7, the cognate receptor of H2 relaxin. Chromatin immunoprecipitation analysis was used to demonstrate that p53(R273H) binds directly to the relaxin promoter, further confirming a role for H2 relaxin signaling in p53(R273H)-mediated AI CaP. Lastly, we used a reporter gene assay to demonstrate that H2 relaxin can induce the expression of prostate-specific antigen via an androgen receptor-mediated pathway.

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.

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.

Suppression of relaxin gene expression by retinoids in squamous differentiated rabbit tracheal epithelial cells

Northern blot analysis of total RNA from a variety of rabbit tissues indicated that placenta is the primary site of expression of the protein hormone relaxin (previously called SQ10) in rabbits. Relaxin was not detected by this method in other rabbit tissues, including normal trachea and several squamous tissues. However, relaxin is highly induced during squamous cell differentiation in cultured rabbit tracheal epithelial (RbTE) cells. Retinoic acid and retinoids that selectively bind to the nuclear retinoid receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs), and induce RARE- or RXRE-dependent transactivation as well as repression of AP-1-dependent transactivation, were all effective in suppressing relaxin expression. In addition, the retinoid SR11302, which exhibits only anti-AP-1 activity but does not induce RARE- or RXRE-dependent transactivation, was also able to inhibit relaxin expression. These results suggest that the suppression of relaxin expression is related to the anti-AP-1 activity of retinoids. To determine whether the relaxin gene is regulated by retinoids at the level of transcription, a 4.3 kb fragment of the 5' flanking region of the rabbit relaxin gene was cloned and analyzed. This regulatory region included a classic TATA-box as well as consensus sequences for several transcription factors, including CREB, NF-kappaB and AP-1. The ability of the 4.3 kb regulatory region to control the transcription of a luciferase reporter gene was analyzed in transiently transfected, squamous-differentiated RbTE cells. The results demonstrated that this regulatory region caused strong transactivation of the reporter gene. This transactivation was inhibited by retinoic acid, suggesting retinoid control at the transcriptional level. Deletion analysis indicated that multiple regulatory elements are involved in the regulation of relaxin gene expression during squamous differentiation as well as in the suppression by retinoids.