Functional activity of voltage-gated sodium channels (VGSC) has been associated to the invasion and metastasis behaviors of prostate, breast and some other types of cancer. We previously reported the functional expression of VGSC in primary cultures and biopsies derived from cervical cancer (CaC). Here, we investigate the relative expression levels of VGSC subunits and its possible role in CaC. Quantitative real-time PCR revealed that mRNA levels of Na V 1.6 a-subunit in CaC samples were~40-fold higher than in noncancerous cervical (NCC) biopsies. A Na V 1.7 a-subunit variant also showed increased mRNA levels in CaC (~20-fold). All four Na V b subunits were also detected in CaC samples, being Na V b1 the most abundant. Proteins of Na V 1.6 and Na V 1.7 a-subunits were immunolocalized in both NCC and CaC biopsies and in CaC primary cultures as well; however, although in NCC sections proteins were mainly relegated to the plasma membrane, in CaC biopsies and primary cultures the respective signal was stronger and widely distributed in both cytoplasm and plasma membrane. Functional activity of Na V 1.6 channels in the plasma membrane of CaC cells was confirmed by whole-cell patch-clamp experiments using Cn2, a Na V 1.6-specific toxin, which blocked 30% of the total sodium current. Blocking of sodium channels VGSC with tetrodotoxin and Cn2 did not affect proliferation neither migration, but reduced by~20% the invasiveness of CaC primary culture cells in vitro assays. We conclude that Na V 1.6 is upregulated in CaC and could serve as a novel molecular marker for the metastatic behavior of this carcinoma.Cervical cancer (CaC) is the third most common female tumor worldwide and the second in developing countries, with an estimated annual incidence of 452,000 cases. 1 In view of the finding that carcinogenic human papillomavirus (HPV) infections cause virtually all CaC cases, recently a new approach for CaC prevention has emerged with the HPV vaccination of younger women (aged 18 years). 2 Despite the highly significant advance that the vaccine itself represents, a mathematical model has predicted an increase in CaC incidence if vaccination is not followed by a continuous Pap smear screening program. 3 Therefore, the finding of effective diagnosis and therapeutic strategies for CaC still remains as a priority.Lately, there has been an increasing amount of evidences that correlate the function of ion channels with several aspects of cancer progression. 4,5 In particular, voltage-gated sodium channels (VGSC) have been clearly associated to invasion and metastasis behaviors in several types of cancer, including breast, colon, lung, ovary and prostate. 6-10 Sodium channels are protein complexes formed by a large a-subunit and smaller auxiliary b-subunits. The a-subunit alone is sufficient to form a functional channel, but its biophysical properties, trafficking and anchoring to the cell membrane are modulated by b-subunits. 11 The VGSC family is composed by nine different a-subunits (Na V 1.1-Na V 1.9) and four bsubunits (Na...

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.

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