ZNF500 suppresses the proliferation of breast cancer cells and sensitizes them to chemotherapy by stabilizing p53 in a manner that is competitive to MDM2

Abstract

Abstract Background: Zinc finger protein 500 (ZNF500) has an unknown expression pattern and biological function in human tissues. This study was designed to determine what role ZNF500 played in breast cancer progression and chemotherapy resistance. Methods: Firstly, we assessed the expression pattern of ZNF500 by bioinformatics assay and immunohistochemistry staining. Colony formation assay, MTT assay, EdU assay, flow cytometric analysis, western blotting analysis, mice xenograft model, immunofluorescence assay, RT-PCR, PCR-array, GST-pull down assay and immunoprecipitation assay were performed to investigate the effect of ZNF500 on proliferation, chemotherapy sensitivity and P53-P21-E2F4 signaling axis activation. Secondly, we constructed ZNF500-ΔC2H2, ZNF500-ΔSCAN,ZNF500-ΔKRAB, P53-ΔC, P53-ΔDBD, P53-ΔN mutant plasmids. Immunoprecipitation assay, GST-pull down assay, and western blotting analysis were performed to evaluate interaction among ZNF500, P53 and MDM2, as well as their impact on chemotherapy sensitivity. Finally, immunohistochemistry analysis was used to assess the expression of ZNF500, P53 and E2F4 in clinical tissue samples and its correlation with chemotherapy resistance. Results:We found that ZNF500 was highly expressed in breast cancer, but negatively correlated with advanced TNM stage, lymph node metastasis and poor prognosis. ZNF500 overexpression abolished in vivo and in vitro breast cancer cell proliferation by activating the p53-p21-E2F4 signaling axis and directly interacted with p53 via its C2H2 domain. This may prevent ubiquitination of p53 in a manner that is competitive to MDM2, thus stabilizing p53. When ZNF500-∆C2H2 was overexpressed, suppressed proliferation of breast cancer cells was neutralized in vitroand in vivo. In human breast cancer tissues, ZNF500 expression was positively correlated with p53and E2F4 expression. ZNF500 expression was significantly lower in patients with Miller/Payne Grade 1–2 than that in those with Miller/PayneGrade 3–5. Conclusions: Our data suggest that ZNF500 can directly bind to the C-terminal of p53 via its C2H2 domain. This interaction may prevent ubiquitin-mediated degradation by MDM2, thus abrogating the proliferation of breast cancer cells, strengthening DNA damage, and sensitizing breast cancer patients to chemotherapy.