Usp7, also known as Herpesvirus associated Ubiquitin-Specific Protease (HAUSP), is a deubiquitinating enzyme (DUB) belonging to the cysteine protease subfamily. It is involved in multiple cellular processes such as epigenetics, tumour suppression, oncogenesis, DNA damage response, immunity and viral infection [3]. By removing ubiquitin from Ub-modified substrates, it participates in various signalling pathways, some of which are dysregulated in malignant tumours [6].

Research shows that USP7 is overexpressed in many cancers like breast, prostate, colorectal, and lung cancers [1]. In lung cancer, specific silencing of USP7 using siRNA or USP7 inhibitors led to phenotypical and functional changes in M2 tumour-associated macrophages (TAMs), favouring CD8+ T cells proliferation in vitro and delaying tumour growth in mice [2]. In non-small cell lung cancer (NSCLC), USP7 directly deubiquitinates KRAS, stabilizing it and promoting cell proliferation, and USP7 inhibitors suppress NSCLC cell proliferation, especially in cells resistant to the KRAS-G12C inhibitor AMG510 [4]. In triple-negative breast cancers (TNBC), USP7 stabilizes the oncoprotein Forkhead Box M1 (FOXM1) through deubiquitination, and inhibition of USP7 can suppress tumour growth in a p53-independent manner [5].

In conclusion, Usp7 is a crucial regulator in multiple biological processes and is significantly associated with cancer development. Studies using loss-of-function models like siRNA silencing and inhibitor treatments have revealed its role in promoting tumour growth in various cancers, suggesting that targeting Usp7 could be a promising strategy for cancer therapy.