Effekte von Kinase-Inhibitoren auf die Östradiolwirkung in der endometrialen Adenokarzinomzelllinie Ishikawa

Abstract

Purpose: Interactions between signal transduction cascades involving tyrosine kinase and its receptor and the cellular response to stimulation with estradiol have received a great deal of study. We studied the effect of inhibitors of receptor tyrosine kinases and cytoplasmatic kinases on the cellular response to estradiol in an endometrial adenocarcinoma cell line that expresses estrogen receptors-alpha. Material and Methods: Estrogen effects were measured with a transient reporter gene assay. Ishikawa endometrial adenocarcinoma cells were cultured without serum and transfected with the vector pERE-TA-SEAP via lipofectamines. The vector contains the secreted alkaline phosphatase (SEAP) reporter gene under the control of an estrogen response element (ERE). After transfection the cells were treated with estradiol, the EGFR inhibitor AG1478, and the MEK inhibitors PD98059 and U0126 for 48 hours. The activity of the EREs was quantified with luminometric measurement of the SEAP concentration in the culture supernatant. Cellular proliferation was measured with an ELISA that quantified the uptake of BrDU into replicating DNA. Results: Physiologic estradiol stimuli caused activation of the ERE. Simultaneous treatment with the EGFR inhibitor AG1478 significantly increased the estradiol-induced activation of ERE. In contrast, both MEK inhibitors reduced both ERE activation and estradiol-induced cellular proliferation. Conclusion: Treatment with the EGFR inhibitor AG1478 increased the response of endometrial adenocarcinoma cells to estrogen stimuli. MEK inhibitors can block MAP kinase signal transduction and inhibit cellular estradiol effects. This suggests that inhibitors of cytoplasmatic kinases may be more useful than EGFR inhibitors in the treatment of endometrial cancers that express estrogen receptors.