Overexpression of Na V1.6 channels is associated with the invasion capacity of human cervical cancer

Abstract

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 V1.6 α-subunit in CaC samples were â̂40-fold higher than in noncancerous cervical (NCC) biopsies. A Na V1.7 α-subunit variant also showed increased mRNA levels in CaC (â̂20-fold). All four Na Vβ subunits were also detected in CaC samples, being Na Vβ1 the most abundant. Proteins of Na V1.6 and Na V1.7 α-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 V1.6 channels in the plasma membrane of CaC cells was confirmed by whole-cell patch-clamp experiments using Cn2, a Na V1.6-specific toxin, which blocked â̂30% of the total sodium current. Blocking of sodium channels VGSC with tetrodotoxin and Cn2 did not affect proliferation neither migration, but reduced by â̂20% the invasiveness of CaC primary culture cells in vitro assays. We conclude that Na V1.6 is upregulated in CaC and could serve as a novel molecular marker for the metastatic behavior of this carcinoma. © 2011 UICC.