Overexpression of NaV1.6 channels is associated with the invasion capacity of human cervical cancer

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 NaV1.6 a-subunit in CaC samples were similar to 40-fold higher than in noncancerous cervical (NCC) biopsies. A NaV1.7 a-subunit variant also showed increased mRNA levels in CaC (similar to 20-fold). All four NaV beta subunits were also detected in CaC samples, being NaV beta 1 the most abundant. Proteins of NaV1.6 and NaV1.7 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 NaV1.6 channels in the plasma membrane of CaC cells was confirmed by whole-cell patch-clamp experiments using Cn2, a NaV1.6-specific toxin, which blocked similar to 30% of the total sodium current. Blocking of sodium channels VGSC with tetrodotoxin and Cn2 did not affect proliferation neither migration, but reduced by similar to 20% the invasiveness of CaC primary culture cells in vitro assays. We conclude that NaV1.6 is upregulated in CaC and could serve as a novel molecular marker for the metastatic behavior of this carcinoma.