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Estrogens and Human Papilloma Virus Oncogenes Regulate Human Ether-à-go-go-1 Potassium Channel Expression

¹ Departamento de Biología de la Reproducción and ² Departamento de Patología, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; ³ Departamento de Inmunología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional; ⁴ Pharmacology Section, ⁵ Department of Genetics and Molecular Biology, and ⁶ Toxicology Section, Centro de Investigación y de Estudios Avanzados; ⁷ Dirección Médica de la U.M.A.E. Hospital de Gineco-Obstetricia No. 3; ⁸ Departamento de Biología. Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria; ⁹ Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Mexico D.F., Mexico

Requests for reprints: Javier Camacho, Centro de Investigación y de Estudios Avanzados del I.P.N., Pharmacology Section, Avenida Instituto Politécnico Nacional 2508, Mexico D.F., Mexico 07360. Phone: 52-55-57473800, ext. 5416; Fax: 52-55-53430106; E-mail: fcamacho{at}cinvestav.mx.

Key Words: human papilloma virus • estrogen • ion channels • placenta • Eag1

Ether-à-go-go-1 (Eag1) potassium channels are potential tools for detection and therapy of numerous cancers. Here, we show human Eag1 (hEag1) regulation by cancer-associated factors. We studied hEag1 gene expression and its regulation by estradiol, antiestrogens, and human papillomavirus (HPV) oncogenes (E6/E7). Primary cultures from normal placentas and cervical cancer tissues; tumor cell lines from cervix, choriocarcinoma, keratinocytes, and lung; and normal cell lines from vascular endothelium, keratinocytes, and lung were used. Reverse transcription-PCR (RT-PCR) experiments and Southern blot analysis showed Eag1 expression in all of the cancer cell types, normal trophoblasts, and vascular endothelium, in contrast to normal keratinocytes and lung cells. Estradiol and antiestrogens regulated Eag1 in a cell type–dependent manner. Real-time RT-PCR experiments in HeLa cells showed that Eag1 estrogenic regulation was strongly associated with the expression of estrogen receptor-. Eag1 protein was detected by monoclonal antibodies in normal placenta and placental blood vessels. Patch-clamp recordings in normal trophoblasts treated with estradiol exhibited potassium currents resembling Eag1 channel activity. Eag1 gene expression in keratinocytes depended either on cellular immortalization or the presence of HPV oncogenes. Eag1 protein was found in keratinocytes transfected with E6/E7 HPV oncogenes. Cell proliferation of E6/E7 keratinocytes was decreased by Eag1 antibodies inhibiting channel activity and by the nonspecific Eag1 inhibitors imipramine and astemizole; the latter also increased apoptosis. Our results propose novel oncogenic mechanisms of estrogen/antiestrogen use and HPV infection. We also suggest Eag1 as an early indicator of cell proliferation leading to malignancies and a therapeutic target at early stages of cellular hyperproliferation. [Cancer Res 2009;69(8):3300–7]