Ubiquitin-specific protease 13 promotes colorectal cancer progression by stabilizing mitogen-activated protein kinase kinase 3.

The deubiquitinase ubiquitin-specific protease 13 (USP13) has been implicated in various cancers, yet its precise molecular function and clinical significance in colorectal cancer (CRC) remain poorly defined. Here, we identify USP13 as a critical regulator of CRC progression through systematic investigation of its impact on oncogenic signaling pathways. Using luciferase-based pathway screening, we discovered that USP13 activates the mitogen-activated protein kinase (MAPK) signaling cascade. USP13 directly interacts with and stabilizes mitogen-activated protein kinase kinase 3 (MKK3), a key upstream kinase of the p38/MAPK pathway, through removal of K48-linked ubiquitination at the K32 residue. This deubiquitination process requires the UBA domain of USP13 and prevents proteasomal degradation of MKK3, leading to enhanced p38 phosphorylation and activation. Functional validation demonstrated that USP13 and MKK3 significantly promotes CRC cell proliferation, migration, and invasion in vitro. Importantly, in vivo xenograft experiments confirmed that USP13-driven tumor growth depends on MKK3 and can be rescued by constitutive p38 activation. Clinical correlation analysis of CRC patient specimens revealed a strong positive correlation between USP13 and MKK3 expression levels, with elevated USP13 expression associated with advanced disease stage. Our findings not only establish the USP13-MKK3-p38 axis as a crucial molecular pathway in CRC progression but also identify USP13 as a promising therapeutic target.