ABSTRACT
<p><b>BACKGROUND</b>Increased risk of bladder cancer has been reported in diabetic patients. This study was to investigate the roles of mitogen-activated protein kinase kinase (MEK) 1 and 2 in the regulation of human insulin- and insulin glargine-induced proliferation of human bladder cancer T24 cells.</p><p><b>METHODS</b>In the absence or presence of a selective inhibitor for MEK1 (PD98059) or a specific siRNA for MEK2 (siMEK2), with or without addition of insulin or glargine, T24 cell proliferation was evaluated by cell counting kit (CCK)-8 assay. Protein expression of MEK2, phosphorylation of ERK1/2 and Akt was analyzed by Western blotting.</p><p><b>RESULTS</b>T24 cell proliferation was promoted by PD98059 at 5 - 20 µmol/L, inhibited by siMEK2 at 25 - 100 nmol/L. PD98059 and siMEK2 remarkably reduced phosphorylated ERK1/2. Insulin- and glargine-induced T24 cell proliferation was enhanced by PD98059, suppressed while not blocked by siMEK2. Insulin- and glargine-induced ERK1/2 activation was blocked by PD98059 or siMEK2 treatment, whereas activation of Akt was not affected.</p><p><b>CONCLUSION</b>MEK1 inhibits while MEK2 contributes to normal and human insulin- and insulin glargine-induced human bladder cancer T24 cell proliferation.</p>