Retinoid X receptors (RXRs) mRNA expression in human pituitary adenomas
Retinoid-X receptors (RXRs) are transcriptional factors that belong to the steroid/thyroid hormone receptor (TR) superfamily. It has been demonstrated that those nuclear receptors act as ligand-activated transcription factors in pituitary cells. To determine whether RXRs play roles in the cell differentiation of pituitary adenomas, we have investigated the expression of RXRγ mRNA in various types of pituitary adenomas usingin situ reverse transcriptase-polymerase chain reaction (RT-PCR). The synergistic function on promoters of specific hormones between these nuclear receptors and pituitary specific transcription factor, Pit-1, has been noticed in in vitro experiments. The colocalization between RXRγ mRNA and Pit-1 protein was examined by combinedin situ RT-PCR and immunohistochemistry. RXRγ mRNA was detected in normal pituitary gland as well as all five growth hormone-(GH)-secreting adenomas and five thyroid stimulating hormone (TSH) secreting adenomas, two of four prolactin- (PRL) secreting adenomas, one of two adrenocorticotropin-(ACTH) secreting adenomas, one of four nonfunctioning adenomas. Byin situ hybridization andin situ RT-PCR followed by immunohistochemistry, the colocalization of Pit-1 mRNA with RXRγ as well as RXRγ mRNA with Pit-1 was observed in adenoma cells of GH-secreting adenomas and TSH-secreting adenomas. We suggest that RXRγ may play a role in cell differentiation and hormonal transcription synergistically with Pit-1 in normal and neoplastic human pituitaries.
Key WordsRetinoid nuclear receptor pituitary neoplasm mRNA in situ RT-PCR
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- 8.Davis KD, Berrodin TJ, Stelmach JE, Winkler JD, Lazar MA. Endogenous retinoid X receptors can function as hormone receptors in pituitary cells. Mol Cel Biol 14:7105–7110, 1994.Google Scholar
- 14.Sanno N, Sugawara A, Teramoto A, Abe Y, Yen PM, Chin WW, et al. Immunohistochemical expression of retinoid X receptor isoforms in human pituitaries and pituitary adenomas. Neuro-endocrinology 65:299–306, 1997.Google Scholar
- 23.Jin L, Qian X, Lloyd RV. Comparison of mRNA expression detected byin situ PCR andin situ hybridization in endocrine cells. Cell Vision 2:314–321, 1995.Google Scholar
- 26.Sanno N, Teramoto A, Osamura RY, Genka S, Katakami H, Jin L, et al. A growth hormone-releasing hormone-producing pancreatic islet cell tumor metastasized to the pituitary is associated with pituitary somatotroph hyperplasia and acromegaly. J Clin Endocrinol Metab 82:2731–2737, 1997.PubMedCrossRefGoogle Scholar
- 30.Yen PM, Sugawara A, Chin WW. Triiodothyronine (T3) differentially affects T3-receptor/ retinoic acid receptor and T3-receptor/retinoid X receptor heterodimer binding to DNA. J Biol Chem 267:23,248–23,252, 1992.Google Scholar
- 33.Perez P, Shonthal A, Aranda A. Repression of c-fos gene expression by thyroid hormone and retinoic acid receptors. J Biol Chem 268:23,538–23,543, 1993.Google Scholar