Slug promotes p53 and p21 protein degradation by inducing Mdm2 expression in HCT116 colon cancer cells

Abstract

Our previous study revealed that the tumor suppressor/transcription factor p53 directly binds to its transcriptional target, p21, and that the p53/p21 complex binds to zinc finger protein SNAI2 (Slug), a tumor promoter/transcription factor; thereby promoting the degradation of Slug by Mdm2, an E3 ligase. The present study demonstrated that Slug reduced the cellular expression levels of p53 and p21 in HCT116 colon cancer by decreasing their protein stability. In parallel, Slug increased the mRNA and protein expression levels of Mdm2 in these cells. Moreover, knockdown of Mdm2 using specific small interfering RNAs abolished the ability of Slug to induce the degradation of p53 and p21. Considering the well-known function of Mdm2 in facilitating p53 and p21 degradation, these data suggested that Slug promoted p53 and p21 degradation by inducing Mdm2 expression. Moreover, Slug increased ubiquitination levels of p53 in HCT116 cells. This is consistent with the fact that Mdm2 induces p53 degradation by ubiquitinating p53, and further confirmed that Mdm2 acted downstream of Slug. Comparative studies using HCT116 cells and their p53-or p21-knockout variants have revealed that Slug requires p21 to induce p53 degradation. This result is consistent with our previous study, which revealed that Mdm2 acts more efficiently on p53 in the p53/p21 complex compared with on p53 alone. By contrast, Slug did not require p53 to induce p21 degradation, suggesting that p53 was dispensable in Mdm2-mediated p21 degradation. Notably, the ability of Slug to increase/decrease Mdm2/p53 and p21 levels, respectively, was not confined to HCT116 cells alone, but was also confirmed in A549 and H460 lung cancer cells. Collectively, the results of the present study suggested that Slug could counter p53 and p21. The balance between these two opposing groups (Slug vs. p53/p21) may depend on environmental stresses and the internal physiology of cells.

Opposing Roles of Wild-type and Mutant p53 in the Process of Epithelial to Mesenchymal Transition

“…The latter can also undergo Mdm2-mediated degradation, but this process is p53-independent. In addition, Slug has been shown to directly activate Mdm2 expression ( Kim J. et al, 2021 ). Importantly, the RING domain of Mdm2 was revealed to be able to interact with RNA.…”

P53/MDM2 Complex-Based Targeted Strategies in Colon Adenocarcinoma

“…The molecule increases MDM2 oncogenic activity, and promotes P53 and P21 cellular expression deficiency by degrading them. A study group analyzing its effect in vitro on HCT116 cells showed that a Slug-dependent P53 decrease is an important genetic event that crucially desynchronizes cell cycle phase succession ( 35 ). Moreover, DJ-1 has been found to modulate the TP53/MDM2 signaling pathway by disrupting their interaction and reducing BCL2-, BAX, and CASPASE-3 activity, leading to increased cell proliferation and decreased apoptotic rates ( 36 ).…”

The Roles of Zinc Finger Proteins in Colorectal Cancer

“…ZNF384 [ 100 ], SNAI2 [ 103 ], and ZEB2 [ 107 ] are upregulated in CRC and enhance MMP2 expression and/or activity, promoting angiogenesis. SNAI2 , which expedites p53/p21 degradation by upregulating MDM2 [ 101 ], is essential for mutant-KRAS cancer cell survival after EMT [ 104 ]. ZNF24 represses VEGF expression [ 109 ] to suppress angiogenesis, while ZKSCAN3 , an inducer of VEGF to promote CRC development and invasion, is implicated in carcinoembryonic antigen (CEA)-producing tumor liver metastasis [ 110 ].…”