Ether à go-go (EAG) potassium channels display oncogenic properties. In normal tissues, EAG mRNA is almost exclusively expressed in brain, but it is expressed in several somatic cancer cell lines, including HeLa, from cervix. Antisense experiments against eag reduce cell proliferation in some cancer cell lines, and inhibition of EAG-mediated currents has been suggested to decrease cell proliferation in a melanoma cell line. Because of the potential clinical relevance of EAG, we investigated EAG mRNA expression in the following fresh samples from human uterine cervix: 5 primary cultures obtained from cancerous biopsies, 1 cancerous fresh tissue, and 12 biopsies of control normal tissue. All of the control cervical samples came from patients with negative pap smears. Reverse transcription-PCR and Southern-blot experiments revealed eag expression in 100% of the cancerous samples and in 33% of the normal biopsies. Immunochemistry experiments showed the presence of EAG channel protein in cells from the primary cultures and in cervical cancer biopsies sections from the same patients. In addition, we looked for EAG-mediated currents in the cultures from cervical cancer cells. Here we show for the first time EAG channel activity in human tumors. Patch-clamp recordings showed typical EAG-mediated currents modulated by magnesium and displaying a pronounced Cole-Moore shift. Because EAG expression and channel activity have been suggested to be important in cell proliferation, our findings strongly support the idea of considering EAG as a tumor marker as well as a potential membrane therapeutic target for cervical cancer.

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-A. 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]

Cervical cancer (CaC) is the third most frequent cause of death from cancer among women in the world and the first in females of developing countries. Several ion channels are upregulated in cancer, actually potassium channels have been suggested as tumor markers and therapeutic targets for CaC. Voltage-gated sodium channels (VGSC) activity is involved in proliferation, motility, and invasion of prostate and breast cancer cells; however, the participation of this type of channels in CaC has not been explored. In the present study, we identified both at the molecular and electrophysiological level VGSC in primary cultures from human cervical carcinoma biopsies. With the whole cell patch clamp technique, we isolated and identified a voltage-gated Na(+) current as the main component of the inward current in all investigated cells. Sodium current was characterized by its kinetics, voltage dependence, sensitivity to tetrodotoxin (TTX) block and dependence to [Na(+)](o). By analyzing the expression of mRNAs encoding TTX-sensitive Na(+) channel alpha subunits with standard RT-PCR and specific primers, we detected Na(v)1.2, Na(v)1.4, Na(v)1.6, and Na(v)1.7 transcripts in total RNA obtained from primary cultures and biopsies of CaC. Restriction enzyme analysis of PCR products was consistent with the molecular nature of the corresponding genes. Notably, only transcripts for Na(v)1.4 sodium channels were detected in biopsies from normal cervix. The results show for the first time the functional expression of VGSC in primary cultures from human CaC, and suggest that these channels might be considered as potential molecular markers for this type of cancer.

Hepatocellular carcinoma (HCC) has very poor prognosis. Astemizole has gained great interest as a potential anticancer drug because it targets several proteins involved in cancer including the Eag1 (ether à-go-go-1) potassium channel that is overexpressed in human HCC. Eag1 channels are regulated by cancer etiological factors and have been proposed as early tumor markers. Here, we found that HepG2 and HuH-7 HCC cells displayed Eag1 messenger RNA (mRNA) and protein expression, determined by real-time RT-PCR and immunochemistry, respectively. Astemizole inhibited human HCC cell proliferation (assessed by metabolic activity assay) and induced apoptosis (studied with flow cytometry) in both cell lines. The subcellular Eag1 protein localization was modified by astemizole in the HepG2 cells. The treatment with astemizole prevented diethylnitrosamine (DEN)-induced rat HCC development in vivo (followed by studying γ-glutamyl transpeptidase (GGT) activity). The Eag1 mRNA and protein levels were increased in most DEN-treated groups but decreased after astemizole treatment. GGT activity was decreased by astemizole. The Eag1 protein was detected in cirrhotic and dysplastic rat livers. Astemizole might have clinical utility for HCC prevention and treatment, and Eag1 channels may be potential early HCC biomarkers. These data provide significant basis to include astemizole in HCC clinical trials.