Role of phosphatase PTEN in the activation of extracellular signal-regulated kinases induced by estradiol in endometrial carcinoma cells.OBJECTIVES:To study extracellular signal-regulated kinase (ERK) activation in the endometrial carcinoma cell line Ishikawa with stimulation by 17-beta-estradiol, and to elucidate the role of phosphatase and tensin homologue (PTEN) and estrogen receptor (ER) subtype on the activation of ERKs.METHODS:Western blot was used to examine the expression of PTEN and PTEN (G129E) in Ishikawa cells after stable transfection as well as ERK activation in Ishikawa-EGFP, Ishikawa- PTEN and Ishikawa- PTEN (G129E) stimulated with various doses of 17-beta-estradiol for different lengths of time. Western blot was also used for examining the expression of ERalpha and ERbeta in NIH3T3 fibroblasts after transient transfection of pCXN2hERalpha and pCXN2hERbeta. Then, ERK activation was examined after stimulation with 17-beta-estradiol.RESULTS:17-beta-estradiol activated ERK cascades (mainly ERK2) in Ishikawa cells. The activation of ERK increased gradually as concentration of 17-beta-estradiol also increased. The maximal activation of ERK2 took place 5 min after stimulation with 17-beta-estradiol. The activation of ERK2 was inhibited markedly by PTEN, but not by PTEN (G129E). 17-beta-estradiol activated ERK cascades in NIH3T3 fibroblasts after transient transfection of pCXN2hERalpha.CONCLUSIONS:17-beta-estradiol activate ERK cascades in Ishikawa cells by integrating with ERalpha. Lipid phosphatase PTEN has an inhibitory role on the activation of ERK stimulated by 17-beta-estradiol in Ishikawa cells.