Disease relevance of INSL3

• The frequency of INSL3/RLF gene mutations as a cause of cryptorchidism is low, because only 2 of 145 (1.4%) formerly cryptorchid patients were found to have mutations [1].
• Subjects with severe testicular damage, such as men with severe infertility, produce low amount of INSL3, and the concentrations of this hormone seem to reflect the functional status of the Leydig cells [2].
• In the present study we have investigated the expression of human INSL3 in patients with benign prostate hyperplasia (BPH), prostate intraepithelial neoplasia (PIN) and prostate carcinoma tissues [3].
• We screened for mutations in INSL3 gene in 967 subjects with a history of maldescended testes and/or infertility and/or testicular cancer and in 450 controls [4].
• By contrast, thyrocytes of all 15 benign goiter tissues studied were devoid of both INSL-3 isoforms, mRNA and protein [5].

High impact information on INSL3

• The relaxin-like factor (RLF, also named INSL3) is a critical component in the chain of events that lead to the normal positioning of the gonads in the male fetus [6].
• In as much as these major binding residues seem hardly sufficient to explain the strong binding of RLF to LGR8 we searched for and found an extended region where little contributions by individual residues added up to a strong receptor affinity [6].
• Insulin-like peptide 3 (INSL3), a member of the relaxin peptide family, is produced in testicular Leydig cells and ovarian thecal cells [7].
• Additionally, INSL3 has an important function in mediating male and female germ cell function [7].
• Alanine-substituted analogs were used to identify the key residues of INSL3 that are responsible for the interaction with the ectodomain of LGR8 [7].

Chemical compound and disease context of INSL3

• ISS boys with letrozole-induced hypergonadotropic hyperandrogenism had, after 12 months of therapy, higher INSL3 levels than did placebo treated (0.85 +/- 0.54 vs. 0.26 +/- 0.17 ng/ml, P < 0.01) [8].
• INSL3 knockout mice are cryptorchid, and in estrogen-induced cryptorchidism, RLF levels in the testis are significantly reduced [9].
• A second Leydig cell product, insl3, is also significantly down regulated and is likely responsible for the cryptorchidism commonly seen in these phthalate-treated animals [10].

Biological context of INSL3

• In this preliminary report we performed the first analysis in humans of INSL3 using a novel RIA kit to measure INSL3 concentrations in serum of normal men and with different testicular pathologies [2].
• Insulin-like 3 (INSL3) hormone plays a crucial role in testicular descent during embryonic development [11].
• Instead, PC-3 responded to INSL3 with significantly enhanced tumor cell motility and a transcriptional down-regulation of ErbB receptors and EGF [3].
• Recently, the role of insulin-like factor-3 (INSL3; alternatively called relaxin-like factor) has been highlighted through the cryptorchid phenotype of mice where genes for either INSL3 or its receptor have been ablated [12].
• INSL3 expression in fetal testis is inhibited by maternal exposure to estrogens [12].

Anatomical context of INSL3

• Insulin-like factor 3 (INSL3) is a member of the relaxin-insulin family, and it is expressed in pre- and postnatal Leydig cells of the testis [2].
• Three human prostate carcinoma cell lines displayed differential gene activity for INSL3 and LGR8 [3].
• Of the prostate epithelial cells, strongest INSL3 expression was detected in the basal epithelial cell compartment [3].
• In addition to expressing INSL3 mRNA, the LGR8-negative DU-145 also expressed an INSL3 splice form formerly demonstrated in thyroid carcinoma cells [3].
• Weaker INSL3 mRNA expression and immunoreactive INSL3 production were observed in secretory epithelial cells and in interstitial smooth muscle cells [3].

Associations of INSL3 with chemical compounds

• In particular, INSL3 concentrations may be an even more sensitive marker of Leydig cell function than testosterone itself [2].
• All-trans-retinoic acid was demonstrated in PC-3 to up-regulate LGR8 gene activity in a dose- and time-dependent manner while having no effect on INSL3 gene activity [3].
• To identify the structural features that are responsible for the interaction of INSL3 with its receptor, its solution structure was determined by NMR spectroscopy together with in vitro assays of a series of B-chain alanine-substituted analogs [7].
• Northern blot analysis indicated that the LGR8 transcripts are expressed in gubernaculum whereas treatment of cultured gubernacular cells with INSL3 stimulated cAMP production and thymidine incorporation [13].
• We also synthesized analogues of INSL3, with amino acid substitutions in the arginine-binding region [14].

Other interactions of INSL3

• INSL3, in turn, binds LGR8 expressed in germ cells to initiate the meiotic progression of arrested oocytes in preovulatory follicles in vitro and in vivo and to suppress male germ cell apoptosis in vivo [15].
• Thus, relaxin-like hormones appear to be present early during C-cell hyperplasia and potentially functional relaxin/INSL3 ligand-receptor systems are present in human MTC tissues and in MTC cell lines [16].
• METHODS: We isolated genomic DNA from 13 individuals with personal and family histories of cryptorchidism and used polymerase chain reaction to amplify all exons of both INSL3 and GREAT, as well as INSL3 proximal promoter sequence, including a putative SF-1 transcription factor binding site [17].
• Operationally the amino acid sequence homologies between the processed H1 and H2 relaxins and hLey I-L may qualify the specificity claimed for immunostaining the human relaxins in the corpus luteum and trophoblast [18].
• During the winter (December, February), roe deer INSL3 was exclusively detected in a subpopulation of alpha-actin-negative, spindle-shaped peritubular cells [19].

Analytical, diagnostic and therapeutic context of INSL3

• Recently, sequence analysis of the human INSL3 and GREAT genes identified several allelic variants [17].
• INSL3 was measured by using a newly developed fluorescence immunoassay [20].
• Nonradioactive in-situ hybridization with a cRNA probe for equine Insl3 and immunohistochemistry with a specific rabbit INSL3 antiserum localized Insl3 transcripts and immunoreactive INSL3 ligand to Leydig cells in all types of testes investigated [21].
• We employed molecular and immunological techniques to investigate the expression of INSL3, a member of the insulin-like superfamily, in prepubertal testis, postpubertal testes exhibiting normal and disturbed spermatogenesis, and cryptorchid testes of male horses [21].
• Human INSL3 increases the activity of human relaxin in mouse bioassays [14].

References