Regulation Of Notch Target Gene Hes1 Expression By TGF-α In Human Glioma U251

Objective:1 To evaluate the effects of ERK agonist TGF-αandγ-secretase inhibitor DAPT on the proliferation of human glioma U251.2 To study the interaction between Notch and Ras/MAPK pathways and its potential mechanisms by using DAPT,TGF-αand PD98059 separately or simultaneously in U251 cells.Results:1 DAPT inhibited U251 cell proliferation whereas TGF-αeffectively stimulated cell proliferation in a time- and dose-dependent manner.2 5μM DAPT could effectively inhibit Notch signaling pathway. After 24 hours, the expression of Notch1,RBP-Jκand Hes1 was down-regulated in the level of mRNA and protein. With increased expression of Hes1,Hash1 expression was upregulated as a consequence.3 1ng/ml TGF-αtransiently increased phosphoration level of ERK1/2 in U251cells, which peaked after 6 hours'exposure to 1ng/ml TGF-α. PD98059 which was added 2 hours prior to TGF-αtreatment could inhibit ERK1/2 activation.4 TGF-αinduced Hes1 and Hash1 expression in U251 cells,but it didn't change upstream components Notch1 and RBP-Jκ. Specific inhibitor of MEK1/2 PD98059 had no effect on Notch signaling molecules including Notch1, RBP-Jκ,Hes1 and Hash1. Conclusions:1 DAPT effectively blocked Notch signaling transduction and inhibited proliferation of U251 cells.2 TGF-αtransiently promoted ERK1/2 phosphoration and stimulated cell proliferation in a longer period.3 TGF-αinduced Hes1 expression which was independent on both Notch and ERK activation.