Pit-1 is expressed in normal and tumorous human breast and regulates GH secretion and cell proliferation

European Journal of Endocrinology (2005) 153 335–344 ISSN 0804-464




EXPERIMENTAL STUDY
Pit-1 is expressed in normal and tumorous human breast
and regulates GH secretion and cell proliferation


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@usc.es)
Abstract
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.
European Journal of Endocrinology 153 335–344


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