Potential Role of Tumor Necrosis Factor-α in Downregulating Sex Hormone-Binding Globulin

Altres ajuts:D.M.S. received a grant from the Instituto de Salud Carlos III and is the recipient of a Miguel Servet contract. This work is supported by Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM). CIBERDEM is an initiative of Instituto de Salud Carlos III.Low plasma sex hormone-binding globulin (SHBG) levels are associated with obesity and predict the development of type 2 diabetes. The reason why obese individuals have low circulating SHBG has been attributed to hyperinsulinemia, but no mechanistic evidence has been described. The aim of the current study is to explore whether tumor necrosis factor-α (TNF-α) rather than insulin could be the main factor accounting for low SHBG levels in obesity. We performed in vitro and in vivo studies using human HepG2 cells and human SHBG transgenic mice. In addition, a cross-sectional study to explore the relationship between TNF-α and SHBG in obese patients and an interventional study to examine the effect of insulin administration on circulating SHBG in type 2 diabetic patients were performed. We provide evidence that TNF-α, but not insulin, is the main factor by which SHBG is reduced in obesity. Plasma SHBG was significantly increased rather than decreased after insulin treatment in diabetic patients. TNF-α-induced reduction of SHBG expression was mediated by downregulating HNF4A. Finally, a negative and independent correlation was found between plasma TNF-α receptor 1 and SHBG levels in obese patients. Our results suggest that TNF-α plays an important role downregulating SHBG in chronic low-grade inflammatory diseases such as obesity and type 2 diabetes

Identification, characterization and expression of novel Sex Hormone Binding Globulin alternative first exons in the human prostate

<p>Abstract</p> <p>Background</p> <p>The human Sex Hormone Binding Globulin (SHBG) gene, located at 17p13.1, comprises, at least, two different transcription units regulated by two different promoters. The first transcription unit begins with the exon 1 sequence and is responsible for the production of plasma SHBG by the hepatocytes, while the second begins with an alternative exon 1 sequence, which replaces the exon 1 present in liver transcripts. Alternative exon 1 transcription and translation has only been demonstrated in the testis of transgenic mice containing an 11-kb human SHBG transgene and in the human testis. Our goal has been to further characterize the 5' end of the SHBG gene and analyze the presence of the SHBG alternative transcripts in human prostate tissue and derived cell lines.</p> <p>Results</p> <p>Using a combination of <it>in silico </it>and <it>in vitro </it>studies, we have demonstrated that the SHBG gene, along with exon 1 and alternative exon 1 (renamed here exon 1A), contains four additional alternative first exons: the novel exons 1B, 1C, and 1E, and a previously identified exon 1N, which has been further characterized and renamed as exon 1D. We have shown that these four alternative first exons are all spliced to the same 3' splice site of SHBG exon 2, and that exon 1A and the novel exon 1B can be spliced to exon 1. We have also demonstrated the presence of SHBG transcripts beginning with exons 1B, 1C and 1D in prostate tissues and cell lines, as well as in several non-prostatic cell lines. Finally, the alignment of the SHBG mammalian sequences revealed that, while exons 1C, 1D and 1E are very well conserved phylogenetically through non-primate mammal species, exon 1B probably aroused in apes due to a single nucleotide change that generated a new 5' splice site in exon 1B.</p> <p>Conclusion</p> <p>The identification of multiple transcription start sites (TSS) upstream of the annotated first exon of human SHBG, and the detection of the alternative transcripts in human prostate, concur with the prediction of the ENCODE (ENCyclopedia of DNA Elements) project, and suggest that the regulation of SHBG is much more complex than previously reported.</p

Human SHBG mRNA Translation Is Modulated by Alternative 5′-Non-Coding Exons 1A and 1B

BACKGROUND: The human sex hormone-binding globulin (SHBG) gene comprises at least 6 different transcription units (TU-1, -1A, -1B, -1C, -1D and -1E), and is regulated by no less than 6 different promoters. The best characterized are TU-1 and TU-1A: TU-1 is responsible for producing plasma SHBG, while TU-1A is transcribed and translated in the testis. Transcription of the recently described TU-1B, -1C, and -1D has been demonstrated in human prostate tissue and prostate cancer cell lines, as well as in other human cell lines such as HeLa, HepG2, HeK 293, CW 9019 and imr 32. However, there are no reported data demonstrating their translation. In the present study, we aimed to determine whether TU-1A and TU-1B are indeed translated in the human prostate and whether 5' UTR exons 1A and 1B differently regulate SHBG translation. RESULTS: Cis-regulatory elements that could potentially regulate translation were identified within the 5'UTRs of SHBG TU-1A and TU-1B. Although full-length SHBG TU-1A and TU-1B mRNAs were present in prostate cancer cell lines, the endogenous SHBG protein was not detected by western blot in any of them. LNCaP prostate cancer cells transfected with several SHBG constructs containing exons 2 to 8 but lacking the 5'UTR sequence did show SHBG translation, whereas inclusion of the 5'UTR sequences of either exon 1A or 1B caused a dramatic decrease in SHBG protein levels. The molecular weight of SHBG did not vary between cells transfected with constructs with or without the 5'UTR sequence, thus confirming that the first in-frame ATG of exon 2 is the translation start site of TU-1A and TU-1B. CONCLUSIONS: The use of alternative SHBG first exons 1A and 1B differentially inhibits translation from the ATG situated in exon 2, which codes for methionine 30 of transcripts that begin with the exon 1 sequence

Expressió i funció del receptor d’andrògens i de les seves unitats de transcripció alternatives en el càncer de pròstata i en la diabetis

El càncer de pròstata és el segon tumor més freqüent i la segona causa de mort per malaltia oncològica en els homes del món occidental. Per a créixer, les cèl·lules epitelials del tumor necessiten els andrògens, les accions dels quals són mediades pel receptor d’andrògens, l’AR, un factor de transcripció que pertany a la família dels receptors hormonals esteroïdals. L’AR és clau en el desenvolupament del tumor de pròstata i per això és la major diana terapèutica en el tractament amb deprivació hormonal en aquesta patologia. La teràpia és efectiva durant un cert període de temps, però després els tumors esdevenen resistents a la castració, augmentant la seva agressivitat. La diabetis melitus (DM) s’ha associat amb un risc augmentat de patir nombrosos càncers. No obstant, diversos estudis demostren que la DM comporta menys risc de patir càncer de pròstata. Amb tots aquests antecedents en la literatura vam voler investigar quin paper jugava l’AR en el procés de l’hormonoresistència i si era un factor que influïa en el menor risc de patir càncer de pròstata en els pacients diabètics. Els resultats obtinguts en la tesi (gràcies a l’ús de models cel·lulars i un model animal xenograft de càncer de pròstata) demostren que hi ha un procés de metilació durant la supressió hormonal, però aquest procés només té lloc en el promotor de l’AR quan la supressió és constant i prolongada en el temps. A més a més s’ha comprovat que en absència d’hormones l’AR es localitza majoritàriament a la mitocòndria. Hem demostrat l’existència de 5 unitats de transcripció de l’AR, 3 de les quals no havien estat descrites anteriorment, que no presenten illes CpG i que podrien jugar un paper important en el càncer de pròstata i el seu progrés. Finalment vam comprovar que la hiperglicèmia redueix els nivells d’AR, a través de l’activació de NF-kB, per tant, els pacients diabètics tindrien menys risc de patir càncer de pròstata degut al silenciament de l’AR canònic. De tos els resultats obtinguts en la tesi podem concloure que el receptor d’andrògens té una gran importància en el desenvolupament i la progressió del càncer de pròstata i que és una molt bona diana per desenvolupar nous fàrmacs.Prostate cancer is the second most common tumour and the second cause of cancer death in men in western world. To grow, tumour epithelial cells need androgens whose actions are mediated by androgen receptor, a transcription factor that belong to the family of hormonal receptors. AR is essential in the development of prostate cancer and for this reason is the main target in most of the therapies of the tumour. Androgen depletion is effective for a certain period of time but at the end the tumors become resistant to castration, increasing their aggressiveness. Diabetes mellitus (DM) is associated with an increased risk of developing many cancers. However, several studies show that the DM carries less risk of prostate cancer. With all this background in literature we wanted to investigate the role played by AR in the process of hormone resistance and if it AR was a key factor in the reduced risk of prostate cancer in diabetic patients. Our results show that there is a process of methylation during hormonal suppression but it only occurs in AR promoter when the androgen ablation is prolonged in time. In addition, it was found that in the absence of hormones AR is located basically in mitochondria. We have demonstrated the existence of 5 transcription units of the AR, 3 of which had not been previously described, with no CpG islands. These new transcription units could play an important role in prostate cancer and its progression. Finally we found that hyperglycemia reduces AR levels through the activation of NF-kB, so diabetic patients have less risk of prostate cancer due to silencing of canonical AR. As a summary, our results indicate that the androgen receptor has a important role in the development and progression of prostate cancer and is a key target for developing new drugs

Expressió i funció del receptor d'andrògens i de les seves unitats de transcripció alternatives en el càncer de pròstata i en la diabetis

El càncer de pròstata és el segon tumor més freqüent i la segona causa de mort per malaltia oncològica en els homes del món occidental. Per a créixer, les cèl·lules epitelials del tumor necessiten els andrògens, les accions dels quals són mediades pel receptor d'andrògens, l'AR, un factor de transcripció que pertany a la família dels receptors hormonals esteroïdals. L'AR és clau en el desenvolupament del tumor de pròstata i per això és la major diana terapèutica en el tractament amb deprivació hormonal en aquesta patologia. La teràpia és efectiva durant un cert període de temps, però després els tumors esdevenen resistents a la castració, augmentant la seva agressivitat. La diabetis melitus (DM) s'ha associat amb un risc augmentat de patir nombrosos càncers. No obstant, diversos estudis demostren que la DM comporta menys risc de patir càncer de pròstata. Amb tots aquests antecedents en la literatura vam voler investigar quin paper jugava l'AR en el procés de l'hormonoresistència i si era un factor que influïa en el menor risc de patir càncer de pròstata en els pacients diabètics. Els resultats obtinguts en la tesi (gràcies a l'ús de models cel·lulars i un model animal xenograft de càncer de pròstata) demostren que hi ha un procés de metilació durant la supressió hormonal, però aquest procés només té lloc en el promotor de l'AR quan la supressió és constant i prolongada en el temps. A més a més s'ha comprovat que en absència d'hormones l'AR es localitza majoritàriament a la mitocòndria. Hem demostrat l'existència de 5 unitats de transcripció de l'AR, 3 de les quals no havien estat descrites anteriorment, que no presenten illes CpG i que podrien jugar un paper important en el càncer de pròstata i el seu progrés. Finalment vam comprovar que la hiperglicèmia redueix els nivells d'AR, a través de l'activació de NF-kB, per tant, els pacients diabètics tindrien menys risc de patir càncer de pròstata degut al silenciament de l'AR canònic. De tos els resultats obtinguts en la tesi podem concloure que el receptor d'andrògens té una gran importància en el desenvolupament i la progressió del càncer de pròstata i que és una molt bona diana per desenvolupar nous fàrmacs.Prostate cancer is the second most common tumour and the second cause of cancer death in men in western world. To grow, tumour epithelial cells need androgens whose actions are mediated by androgen receptor, a transcription factor that belong to the family of hormonal receptors. AR is essential in the development of prostate cancer and for this reason is the main target in most of the therapies of the tumour. Androgen depletion is effective for a certain period of time but at the end the tumors become resistant to castration, increasing their aggressiveness. Diabetes mellitus (DM) is associated with an increased risk of developing many cancers. However, several studies show that the DM carries less risk of prostate cancer. With all this background in literature we wanted to investigate the role played by AR in the process of hormone resistance and if it AR was a key factor in the reduced risk of prostate cancer in diabetic patients. Our results show that there is a process of methylation during hormonal suppression but it only occurs in AR promoter when the androgen ablation is prolonged in time. In addition, it was found that in the absence of hormones AR is located basically in mitochondria. We have demonstrated the existence of 5 transcription units of the AR, 3 of which had not been previously described, with no CpG islands. These new transcription units could play an important role in prostate cancer and its progression. Finally we found that hyperglycemia reduces AR levels through the activation of NF-kB, so diabetic patients have less risk of prostate cancer due to silencing of canonical AR. As a summary, our results indicate that the androgen receptor has a important role in the development and progression of prostate cancer and is a key target for developing new drugs

Diabetes protects from prostate cancer by downregulating androgen receptor: new insights from LNCaP cells and PAC120 mouse model.

Type 2 diabetes has been associated with decreased risk of prostate cancer in observational studies, and this inverse association has been recently confirmed in several large cohort studies. However the mechanisms involved in this protective effect remain to be elucidated. The aim of the present study was to explore whether different features of type 2 diabetes (hyperinsulinemia, hyperglycemia and tumor necrosis factor alpha [TNF-α]) protect against the development of prostate cancer. For this purpose LNCaP cells were used for in vitro experiments and nude mice in which PAC120 (hormone-dependent human prostate cancer) xenografts had been implanted were used for in vivo examinations. We provide evidence that increasing glucose concentrations downregulate androgen receptor (AR) mRNA and protein levels through NF-κB activation in LNCaP cells. Moreover, there was a synergic effect of glucose and TNFα in downregulating the AR in LNCaP cells. By contrast, insulin had no effect on AR regulation. In vivo experiments showed that streptozotocin-induced diabetes (STZ-DM) produces tumor growth retardation and a significant reduction in AR expression in PAC120 prostate cancer mice. In conclusion, our results suggest that hyperglycemia and TNF-α play an important role in protecting against prostate cancer by reducing androgen receptor levels via NF-κB

Treatment with streptozotocin reduces prostate tumor growth in PAC120 mouse model.

<p>(<b>A</b>) Pictures of tumors developed in vehicle treated mice (n = 5) (i), STZ treated after or before tumor implantation (n = 7 for both) with reduced (ii) or no tumor growth (iii). (<b>B</b>) Comparison of tumor volume for non-treated (n = 5) and citrate treated (n = 5) mice. (<b>C</b>) Tumor volume of STZ-treated animals after tumor implantation compared with tumor volume of citrate treated mice. (<b>D</b>) Tumor volume of STZ-treated animals before tumor implantation compared with tumor volume of citrate treated mice. Data are mean ± SD. *P<0.05 and **P<0.01 compared with the control.</p

Treatment with streptozotocin reduces androgen receptor staining in prostate tumors in PAC120 mouse model.

<p>(<b>A</b>) HE staining of prostate tumor xenografts from control mice, (<b>D</b>) citrate treated mice, (<b>G</b>) STZ-treated before tumor implantation and (<b>J</b>) STZ-treated after tumor implantation. (<b>B</b>) AR staining of prostate tumor xenografts from non-treated mice, (<b>E</b>) citrate treated mice, (<b>H</b>) STZ-treated mice before tumor implantation and (<b>K</b>) STZ-treated mice after tumor implantation. (<b>C</b>) Cytokeratine staining of prostate tumor xenografts from control mice, (<b>F</b>) citrate treated mice, (<b>I</b>) STZ-treated mice before tumor implantation and (<b>L</b>) STZ-treated mice after tumor implantation.</p