P5091

USP7 regulates growth and maintains the stemness of p53-mutant colorectal cancer cells via stabilizing of mutant p53

Introduction:
TP53 is among the most frequently mutated genes across various cancers, with mutations observed in over 40% of colorectal cancers (CRCs). The accumulation of mutant p53 can promote the cancer stem cell (CSC) phenotype and accelerate colorectal tumorigenesis. Therefore, targeting and reducing mutant p53 protein levels presents a promising anticancer strategy.

Methods:
CSC-enriched cancer cells were generated using a tumor sphere formation assay. The impact of USP7 on cancer cell proliferation was assessed through MTS and colony formation assays. A wound healing assay evaluated the cells’ migratory ability. To analyze mRNA and protein expression levels of CSC markers, USP7, and p53, qPCR and western blotting were performed. The interaction between USP7 and p53 was confirmed using a co-immunoprecipitation assay.

Results:
Our findings revealed that both USP7 and mutant p53 were significantly elevated in CSC-enriched colorectal cancer cells, with USP7 expression closely linked to the self-renewal and maintenance of CCSCs. USP7 played a crucial role in regulating cell proliferation, stemness, and migration. Knockdown of USP7 notably inhibited cancer cell growth and reduced the self-renewal capacity of CSC-enriched cells. Additionally, USP7 depletion significantly decreased mutant p53 protein levels in both CRC and CSC-enriched cells. Further analysis demonstrated that USP7 stabilized mutant p53 by directly interacting with it. Treatment with the USP7 inhibitor P5091 also diminished the self-renewal of CCSCs and lowered mutant p53 levels.

Conclusion:
In summary, our study highlights the role of USP7 in maintaining the stemness of CCSCs and identifies it as a key regulator of mutant p53 stability. These findings suggest that USP7 is a potential therapeutic target for cancers harboring p53 mutations.