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EXPERIMENTAL STUDY |
1 Departments of Physiology, 2 Morphological Sciences and 3 Obstetrics and Gynecology, School of Medicine, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
(Correspondence should be addressed to R Perez-Fernandez; Email: fsropefe{at}usc.es)
Background: The transcription factor pituitary-1 (Pit-1) is mainly expressed in the pituitary gland, where it has critical roles in cell differentiation and as a transcriptional factor for GH and prolactin (PRL). It is also expressed in human extrapituitary tissues (placenta, lymphoid and haematopoietic tissues) and cell lines (human breast adenocarcinoma cells, MCF-7). Despite the widely suggested roles of GH and PRL in the progression of proliferative mammary disorders, Pit-1 expression in human mammary gland has not yet been reported.
Objective: To evaluate the expression of Pit-1 in human breast and, using the MCF-7 cell line, to investigate whether Pit-1 overexpression regulates GH expression and increases cell proliferation.
Methods: Using real-time RT-PCR, western blotting and immunohistochemistry, we evaluated the expression of Pit-1 mRNA and protein in seven normal human breasts and 14 invasive ductal mammary carcinomas. GH regulation by Pit-1 in MCF-7 cells was evaluated using RT-PCR, western blotting, ELISA and transfection assays. Cell proliferation was evaluated using bromodeoxyuridine.
Results: We found expression of Pit-1 mRNA and protein in both normal and tumorous human breast. We also found that Pit-1 mRNA levels were significantly increased in breast carcinoma compared with normal breast. In MCF-7 cells, Pit-1 overexpression increased GH mRNA and protein concentrations and significantly increased cell proliferation.
Conclusions: These findings indicate that Pit-1 is expressed in human breast, that it regulates endogenous human mammary GH secretion, and that it increases cell proliferation. This suggests that, depending on its level of expression, Pit-1 may be involved in normal mammary development, breast disorders, or both.
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S. Seoane, I. Ben, V. Centeno, and R. Perez-Fernandez Cellular Expression Levels of the Vitamin D Receptor Are Critical to Its Transcriptional Regulation by the Pituitary Transcription Factor Pit-1 Mol. Endocrinol., July 1, 2007; 21(7): 1513 - 1525. [Abstract] [Full Text] [PDF]
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S. Seoane and R. Perez-Fernandez The Vitamin D Receptor Represses Transcription of the Pituitary Transcription Factor Pit-1 Gene without Involvement of the Retinoid X Receptor Mol. Endocrinol., April 1, 2006; 20(4): 735 - 748. [Abstract] [Full Text] [PDF]
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