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Bentov Y, Jurisicova A, Kenigsberg S, Casper RF. What maintains the high intra-follicular estradiol concentration in pre-ovulatory follicles? J Assist Reprod Genet 2015; 33:85-94. [PMID: 26552664 DOI: 10.1007/s10815-015-0612-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022] Open
Abstract
PURPOSE The purpose of the study was to establish the mechanism by which the estrogen concentration difference between the follicular fluid and the serum is maintained. METHODS We used dialysis membrane with a pore size of <3 KD to characterize the estrogen-binding capacity of the follicular fluid. We performed PCR, western blot, and ELISA on luteinized granulosa cells to determine if sex hormone-binding globulin (SHBG) is produced by granulosa cells, and finally we used affinity columns and mass spectrometry to identify the estrogen-binding protein in the follicular fluid. RESULTS We found that a significant estrogen concentration difference is maintained in a cell-free system and is lost with proteolysis of the follicular fluid proteins. Luteinized granulosa cells are likely not a source of SHBG, as we were not able to detect expression of SHBG in these cells. Perlecan was the most highly enriched follicular fluid protein in the affinity columns. CONCLUSIONS We were able to identify perlecan as the most likely candidate for the major estrogen-binding protein in the follicular fluid.
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Affiliation(s)
- Yaakov Bentov
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada. .,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada. .,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada.
| | - Andrea Jurisicova
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Shlomit Kenigsberg
- CReATe Fertility Centre, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
| | - Robert F Casper
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada.,Toronto Center for Assisted Reproductive Technologies, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
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Nakhla AM, Hryb DJ, Rosner W, Romas NA, Xiang Z, Kahn SM. Human sex hormone-binding globulin gene expression- multiple promoters and complex alternative splicing. BMC Mol Biol 2009; 10:37. [PMID: 19416531 PMCID: PMC2694190 DOI: 10.1186/1471-2199-10-37] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 05/05/2009] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Human sex hormone-binding globulin (SHBG) regulates free sex steroid concentrations in plasma and modulates rapid, membrane based steroid signaling. SHBG is encoded by an eight exon-long transcript whose expression is regulated by a downstream promoter (P(L)). The SHBG gene was previously shown to express a second major transcript of unknown function, derived from an upstream promoter (P(T)), and two minor transcripts. RESULTS We report that transcriptional expression of the human SHBG gene is far more complex than previously described. P(L) and P(T) direct the expression of at least six independent transcripts each, resulting from alternative splicing of exons 4, 5, 6, and/or 7. We mapped two transcriptional start sites downstream of P(L) and P(T), and present evidence for a third SHBG gene promoter (P(N)) within the neighboring FXR2 gene; PN regulates the expression of at least seven independent SHBG gene transcripts, each possessing a novel, 164-nt first exon (1N). Transcriptional expression patterns were generated for human prostate, breast, testis, liver, and brain, and the LNCaP, MCF-7, and HepG2 cell lines. Each expresses the SHBG transcript, albeit in varying abundance. Alternative splicing was more pronounced in the cancer cell lines. P(L)- P(T)- and P(N)-derived transcripts were most abundant in liver, testis, and prostate, respectively. Initial findings reveal the existence of a smaller immunoreactive SHBG species in LNCaP, MCF-7, and HepG2 cells. CONCLUSION These results extend our understanding of human SHBG gene transcription, and raise new and important questions regarding the role of novel alternatively spliced transcripts, their function in hormonally responsive tissues including the breast and prostate, and the role that aberrant SHBG gene expression may play in cancer.
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Affiliation(s)
- Atif M Nakhla
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - Daniel J Hryb
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - William Rosner
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
- Department of Medicine, Columbia University, New York, NY 10032, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA
| | - Nicholas A Romas
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
| | - Zhaoying Xiang
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY 10021, USA
| | - Scott M Kahn
- Department of Urology, Columbia University, New York, NY, 10032, USA
- Institute for Health Sciences, St Luke's-Roosevelt Hospital, 432 W 58th St Room 405, New York, NY, 10019, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA
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Abstract
The present study was undertaken to determine the significance of sex hormone binding globulin, the major and specific binding protein for testosterone and estradiol, in breast cancer. Among breast cancer patients, lower serum levels of Sex hormone binding globulin and higher levels of testosterone were observed. Sex hormone binding globulin showed an inverse relationship with testosterone and total cholesterol, and a direct relation with HDL-cholesterol. By the western blot analyses, Sex hormone binding globulin was detected in all biological samples that we examined. In the breast tumor tissue sections, immuno-staining for Sex hormone binding globulin was confined in cell cytoplasm and 29% cases were positive, which showed no association with the investigated prognostic markers of breast cancer such as ER and HER-2/neu over-expression. In this study, decreased circulating levels of Sex hormone binding globulin in breast cancer patients possibly indicate higher bioavailable estrogens.
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Nkhata KJ, Ray A, Dogan S, Grande JP, Cleary MP. Mammary tumor development from T47-D human breast cancer cells in obese ovariectomized mice with and without estradiol supplements. Breast Cancer Res Treat 2008; 114:71-83. [PMID: 18392696 DOI: 10.1007/s10549-008-9991-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 03/24/2008] [Indexed: 11/29/2022]
Abstract
Obesity is a risk factor for postmenopausal breast cancer, particularly for development of estrogen-receptor (ER)-positive tumors. Additionally, obesity is implicated in breast cancer progression. However, few studies address mechanisms of action of how obesity mediates these responses. Our goal was to address how obesity and/or elevated serum leptin affects tumor formation from ER-positive T47-D cells. In Study 1 ovariectomized CD-1 nude female mice were injected with goldthioglucose (GTG) at 0.5 mg/g body weight in saline or the vehicle at 6 weeks of age. At 10 weeks of age mice were inoculated with T47-D cells and implanted with estrogen pellets. In Study 2 mice were injected with 0.3 mg/g GTG or the vehicle. At 10 weeks of age cells were inoculated and mice were implanted with estrogen or placebo pellets. Mice were followed until 30 weeks of age. Some GTG mice became obese and others were non-responders. In Study 1 no mice developed tumors. In Study 2 mice with placebo pellets developed more tumors than mice with estrogen pellets, 50% vs. 13%. GTG-obese mice with placebo pellets had a 100% tumor incidence compared to 50% and 20% for GTG-lean and controls without estrogen. Serum leptin was higher in obese compared to lean mice and adiponectin was not affected by body weight. Adiponectin:leptin ratio was significantly reduced in obese compared to lean mice. Leptin, leptin receptor and signaling protein expression were determined in mammary and tumor tissue. Leptin and STAT3 were most abundant in tumors. These findings suggest that in vivo estrogen suppressed proliferation of T47-D cells but without supplemental estrogen obesity enhanced tumor development. The exact reason for this is not presently clear.
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Affiliation(s)
- Katai J Nkhata
- Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, MN 55912, USA
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