Phosphorylation status of ASPP2 modulates p53 apoptotic function in oxaliplatin-induced apoptosis of colorectal cancer HCT116 cells / 中华肿瘤杂志

ABSTRACT

<p><b>OBJECTIVE</b>To investigate the role of apoptosis stimulating protein 2 of p53 (ASPP2) phosphorylation status in the regulation of ASPP2-p53 apoptotic pathway activity.</p><p><b>METHODS</b>Cells were individually transfected with green fluorescent protein (GFP)-encoding vector, constitutively non-phosphorylatable ASPP2 mutant-ASPP2 (Am)-encoding vector, and wild type ASPP2 (Aw)-encoding vector) plasmids, respectively, to make them overexpressing phosphorylated and non-phosphorylated ASPP2 proteins, respectively. Cell apoptosis was induced by oxaliplatin. The apoptosis rate of cells was determined by flow cytometry after staining with FITC-conjugated annexin V and PI. ASPP2 protein level and its phosphorylation status were observed by Western blot. The interaction between ASPP2 and p53 was observed by immunoprecipitation assay.</p><p><b>RESULTS</b>Oxaliplatin induced cell apoptosis and caused phosphorylation of ASPP2 at ser92/ser361 in the HCT116 cells. The apoptosis rate of Aw and Am plasmids-transfected cells were (3.8 ± 1.0)% and (3.9 ± 1.2)% respectively, statistically with a non-significant difference (P > 0.05) in comparison with that of the GFP plasmid-transfected cells [(4.0 ± 0.8)%]. After oxaliplatin treatment, the apoptosis rate of Aw plasmid-transfected cells was (46.7 ± 3.9)%, significantly higher than that of the Am and GFP plasmid-transfected cells [(40.1 ± 10.2)% and (37.1 ± 6.9)%, respectively, P < 0.05], however, there was no statistically significant difference (P > 0.05) between Am and GFP plasmid-transfected cells. These results indicate that phosphorylated ASPP2 promoted the oxaliplatin-induced apoptosis of HCT116 cells through a p53-dependent pathway. Phosphorylation status of ASPP2 influenced its binding activity to p53.</p><p><b>CONCLUSION</b>Phosphorylation status of ASPP2 modulates p53 apoptotic function in oxaliplatin-induced apoptosis of colorectal cancer HCT116 cells.</p>