DIETHYLSTILBESTROL-INDUCED IMMORTALIZATION OF HUMAN ENDOMETRIAL CELLS- ALTERATIONS IN P53 AND ESTROGEN-RECEPTOR

Carcinogenesis is a process requiring multiple steps. Immortalization is one step in this process and may be rate limiting. To further our u nderstanding of estrogen-induced carcinogenesis, we evaluated diethyls tilbestrol (DES)-induced immortalization of human endometrial stromal cells. This was achieved by assessing at the restrictive temperature t he colony-forming efficiency of cells that were conditionally immortal ized with a temperature-sensitive simian virus 40 large T antigen. Tre atment with DES for 1 wk did not increase the immortalization frequenc y; however, cultures that were treated for 20 wk had a twofold increas e in immortalization frequency, and continued treatment for a total of 44 wk produced a threefold increase in immortalization frequency that was dose dependent. DES-treated restrictive temperature variants (RTV s) but not spontaneous RTVs lost the temperature-sensitive phenotype. DES-RTVs also had a shorter doubling time than spontaneous RTVs did. p 53 expression was increased in DES-RTVs, and its localization within t he cell was altered. Conversely, expression of the estrogen receptor w as decreased in DES-immortalized cells. These changes in gene expressi on often occur in estrogen-related malignancies, and our results are c onsistent with a causal role for estrogens in these p53 and the estrog en receptor alterations. Immortalization of human cells may be analogo us to initiation of rodent cells, and our results suggest that estroge n-induced alterations in p53 or other genes that regulate life span co uld contribute to estrogen-induced initiation. (C) 1996 Wiley-Liss, In c.