Combination of MG132 and RA induces p53-independent apoptosis and RelA inhibition.

<p>(A, B) The apoptosis induced by MG132 and MG132/RA is p53 independent. (<b>A</b>) Luciferase assay performed on SK-N-BE(2) cells and (<b>B</b>) SH-SY5Y cells to assess transcriptional activity of p53 upon treatment. SK-N-BE(2) cells express mutant p53, SH-SY5Y neuroblastoma cells are wildtype for p53. LRU= Luciferase reference unit. (<b>C</b>) Representative western blot showing the accumulation of p53 protein in response to MG132 treatment. MG132 treatment does not induce up-regulation of the p53 responsive gene p21/Waf1 in SK-N-BE(2) cells, (<b>D</b>) in contrast to SH-SY5Y cells. (<b>E</b>, <b>F</b>) Effects of combined RA/MG132 treatment on NF-κB signalling. Both MG132 as well as RA cause significant decrease of nuclear expression of RelA (p65) protein. (<b>E</b>) Immunofluorescent detection of sub-cellular localization of RelA (p65) protein under the different treatment conditions. Arrows indicate RelA (p65) protein in the nucleus. Scale bar = 25μm. (<b>F</b>) Quantitative data. The reduction of the cell fraction with nuclear RelA expression in response to combined treatment is statistically significant (*) as compared to control (p< 0.037), to RA treated cells (<i>p</i>=0.037), but also to MG132 treated cells (<i>p</i>=0.016).