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Estrogen-induced rat pituitary tumor is associated with loss of retinoblastoma susceptibility gene product.

Authors: Chun, TY  Wendell, D  Gregg, D  Gorski, J 
Citation: Chun TY, etal., Mol Cell Endocrinol. 1998 Nov 25;146(1-2):87-92.
Pubmed: (View Article at PubMed) PMID:10022766

Chronic treatment of rats with the estrogens 17beta-estradiol or diethylstilbestrol (DES) induces pituitary tumors in Fischer 344 but not Brown-Norway or Sprague-Dawley rats. Functional loss of retinoblastoma susceptibility gene product (pRb), a major regulatory protein for the G1 to S transition of the cell cycle, has been shown in several tumors. Here we report a decreased level of pRb in pituitary tumors of the Fischer 344 rat as compared with resistant Sprague Dawley and Brown-Norway strains. pRb protein levels decreased 70% in Fischer 344 rats that were treated with diethylstilbestrol for 10 weeks as compared with tumor resistant control animals. Interestingly, the F1 hybrid (Fischer 344 x Norway) showed an intermediate range of pRb protein expression as compared with those of the parental strains. pRb expression levels in nonhemorrhagic F2 (F1 x F1) rats correlated with the size of the tumors. One week withdrawal of DES increased pRb levels as compared with continuously treated rats. Also, there was a decreased association of cyclin D and cyclin dependent kinase in susceptible tumors, supporting the hypothesis of a physical and possibly functional loss of pRb in the diethylstilbestrol-induced pituitary tumor. These results suggest that the difference in pRb regulation, whether it is a direct or indirect effect of estrogen, is related to tumor resistance or susceptibility in these two rat strains.


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CRRD Object Information
CRRD ID: 8547989
Created: 2014-03-04
Species: All species
Last Modified: 2014-03-04
Status: ACTIVE


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