Abstract
Previous studies have shown that ion channels and transporters are indispensable for cell function including normal cell growth and proliferation. Particularly, modulation of Cl− transport via Cl− channel, K+/Cl− cotransporter (KCC) and Na+/K+/2Cl− cotransporter (NKCC) occurs during cell proliferation. However, it is unknown whether proliferation of cancer cells has correlation to NKCC expression and activity. We determined mRNA and functional expression levels of the NKCC and investigated an inhibitory effect of NKCC blocker, furosemide (a loop diuretic), on proliferation in two human cancer cell lines, MKN28 and MKN45, which were respectively established from moderately and poorly differentiated adenocarcinoma. We found that both mRNA and functional expression levels of NKCC were higher in MKN45 than MKN28 cells. Furthermore, furosemide inhibited the cell proliferation delaying the G1/S phase progression in MKN45 cells. Since furosemide may diminish the intracellular Cl− concentration ([Cl−]i) by blocking NKCC, we studied the effect of [Cl−]i reduction on the proliferation of MKN cells. The cells cultured in low Cl− media showed the elevation of the G0/G1 population associated with increased expression of cyclin-dependent kinase inhibitor, p21, one of the critical molecules for G1/S checkpoint. These observations suggest that the NKCC plays important roles in cell cycles and cell proliferation of human gastric cancer cells via regulation of [Cl−]i. [J Physiol Sci. 2007;57 Suppl:S20]
