Fig. 6.

Notch1 confers GC resistance by activating Akt with subsequent inhibition of GSK3. A and B, Overexpression of ICN-Notch1 confers GC resistance on 2B4, but not on PD1.6 cells. 2B4 (A), 2B4Notch1 cells overexpressing ICN-Notch1 (A), PD1.6 (B) or PD1.6Notch1 cells overexpressing ICN-Notch1 (B) were exposed to Dex for 20 h. Apoptosis was measured by PI exclusion. C, ICN-Notch1 is transcriptionally active in 2B4 cells, but not in PD1.6 cells. RT-PCR analysis was performed on the indicated cell lines for detection of the mRNA of GR, SRG3, a gene product related to GC sensitivity (86 ), and the Notch-regulated gene Deltex1. The housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was included as a control. D, 2B4Notch1 cells show elevated Akt phosphorylation. Western blot analysis of untreated or Dex-treated (100 nm, 2 h) 2B4 and 2B4Notch1 cells. E, Mcl-1 is induced in 2B4 cells overexpressing Notch1. Total extracts of the indicated cell lines were analyzed by Western blotting.