Figure 1.

Zn (II)-curc induces endoplasmic reticulum (ER) stress in mutant p53H273-carrying cells. (a) Representative photomicrographs of ER-Red Fluorescence staining in U373 cells untreated (Mock) or treated with Zn (II)-curc (100 µg/mL) for 16 h (Original magnification: 40×). (b) Quantization of ER content in U373 cells from ER-Red Fluorescence-stained cells. Mean fluorescence intensity (MFI) of each individual cell was normalized to cell size and expressed as fold-change compared with untreated cells at the same time point. Histograms represent the mean ± SD of three independent experiments. * p ≤ 0.05. (c) Western blot analysis of p53, BiP, total (tot) IRE1α, phosphorylated (p) IRE1α, and XBP1 spliced (s) protein levels evaluated in U373 and HT29 cells untreated or treated with Zn (II)-curc (100 µg/mL) for 24 h. (d) Densitometric analysis was performed using Image J software to calculate the ratio of the protein levels, as detected in (c), vs. β-actin. Histograms represent the mean ± SD of three independent experiments. * p ≤ 0.05. (e) Total mRNA was extracted from U373 and HT29 cells untreated or treated with Zn (II)-curc (100 µg/mL) for 24 h. Spliced (s) Xbp1 gene expression was assayed by the polymerase chain reaction (PCR) of reverse-transcribed cDNA. Densitometric analysis was performed using Image J software to calculate the Xbp1s/28S ratio. Histograms represent the mean ± SD of three independent experiments. * p ≤ 0.05. (f) p53 gene expression was assayed by PCR as in (e). The p53/28S ratio is indicated.