The Research On Large-conductance Ca²⁺-activated K⁺ Channels In Human Skin Squamous Cell Carcinoma

Objective:To observe the different expression of human large-conductance Ca2+-activated K+ channels (BKCa) in human skin squamous cell carcinoma(SCC) and the normal human skin, the distribution of the BKCa protein in two tissues was to be studied. The effect of the special BKCa blocker Iberiotoxin on proliferation of the human skin squamous cell carcinoma (A431)cell line is to be explored. Methods:1.There were 27 SCC specimens.Patient’s age ranged from 32 to 80 years (median,51.5 years).Seventeen patients were males and ten were females.And there were 10 normal human skin specimens.Patient’s age ranged from 29 to 70 years (median,48 years).Five patients were males and five were females.Immuno-histochemical method to examine the expression of BKCa protein in the two kinds of specimens was being used. The distribution of the BKCa protein in two tissues by microscope was observed and the Image Pro Plus 6.0 soft ware was used to detect the optical density (OD) of every specimen.2.The effect of Iberiotoxin on proliferation of A431 cells was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which was added on the medium containing different concentrations of Iberiotoxin(1,5,10, 20nmol/L) to A431 cells during the vitro culture.After cultivating for 12h,24h and 36h, ELISA reader is used(wavelength is 490nm) to detect the absorbance(A) of every cell.Results:1.After the immuno-histochemical examination, all of the SCC specimens were expressing the BKCa protein and the protein existed in the cytolymph of the cancer cell. The expression rate was 100%.The nucleus and membrane of the cancer cells had negative expression. Besides, the BKCa protein existed in the cytolymph of blood vessel were endothelium cells which were next to cancer cells.10 normal human skin specimens were expressing the BKCa protein and the protein existed in the cytolymph of the normal human skin basal layer cells too.The expression rate was also 100%.The nucleus and membrane of the normal skin basal layer cells had negative expression.The expression of the BKCa protein in the SCC was higher than that of the normal human skin (P<0.05).The differentiation of the SCC was lower, the expression of the BKCa protein was more.2. Iberiotoxin inhibited the proliferation of A431 cells in time and concentration-dependent manner, after 12h and by adding 10 nmol/L Iberiotoxin to A431 cells,the proliferation of A431 cells were inhibited significant. Conclusion:1.The BKCa protein existed in the cytolymph of the SCC cell and normal basal layer cells.2.The expression of the BKCa protein in the SCC was higher than that of the normal human skin and it had a certain correlation with the malignancy,the lower differentiation of the SCC,the more expression of the BKCa protein.3.The large- conductance Ca-activated K+ channel plays an important role in regulating proliferation of A431 cells.Blocking the large-conductance Ca2+-activated K+ channels could inhibit proliferation of A431 cells.Our data suggests that the large-conductance Ca2+-activated K+ channel is a regulator of human skin squamous cell carcinoma.