Estradiol influences p53 expression in a human endometrial adenocarcinoma heterotransplanted into nude mice

The influence of different estradiol concentrations on the expression of the p53 suppressor gene and on cell kinetics was examined by semiquantitative analysis of protein and bromodeoxyuridine labelling in a human endometrial adenocarcinoma grown in nude mice. We found that increasing the circulating estradiol increases (p = 0.001), and decreasing the hormone value decreases (p = 0.001) the expression of p53 in this tumor. The number of cells in the G1/G0 phase of the cell cycle was significantly higher (p = 0.03), and the number of cells in the G2/M phase was significantly lower (p = 0.01) in tumors grown in estradiol-treated mice than in tumors obtained from the nontreated group. Changes in p53 expression may possibly be explained by either altered transcription activity of the gene or increased half-life of the protein. Our results suggest an important role of estradiol in the progression of estrogen receptor (ER) positive human endometrial adenocarcinomas.