The Wnt signaling pathway plays important roles in embryonic development, homeostatic processes, cell differentiation, cell polarity, cell proliferation, and cell migration via the β-catenin binding of Wnt target genes. Dysregulation of Wnt signaling is associated with various diseases such as cancer, aging, Alzheimer’s disease, metabolic disease, and pigmentation disorders. Numerous studies entailing the Wnt signaling pathway have been conducted for various cancers. Diverse signaling factors mediate the up- or down-regulation of Wnt signaling through post-translational modifications (PTMs), and aberrant regulation is associated with several different malignancies in humans. Of the numerous PTMs involved, most Wnt signaling factors are regulated by ubiquitination and deubiquitination. Ubiquitination by E3 ligase attaches ubiquitins to target proteins and usually induces proteasomal degradation of Wnt signaling factors such as β-catenin, Axin, GSK3, and Dvl. Conversely, deubiquitination induced by the deubiquitinating enzymes (DUBs) detaches the ubiquitins and modulates the stability of signaling factors. In this review, we discuss the effects of ubiquitination and deubiquitination on the Wnt signaling pathway, and the inhibitors of DUBs that can be applied for cancer therapeutic strategies.

In ovarian cancer patients, the 5-year survival rate is 90% for stages I and II, but only 30% for stages III and IV. Unfortunately, as 75% of the patients are diagnosed at stages III and IV, many experience a recurrence. To ameliorate this, it is necessary to develop new biomarkers for early diagnosis and treatment. The ubiquitin–proteasome system is a post-translational modification that plays an important role in regulating protein stability through ubiquitination. In particular, deubiquitinating enzymes (DUBs) regulate protein stability through deubiquitinating substrate proteins. In this review, DUBs and substrates regulated by these enzymes are summarized based on their functions in ovarian cancer cells. This would be useful for the discovery of biomarkers for ovarian cancer and developing new therapeutic candidates.

Epithelial ovarian cancer (EOC) poses a challenge owing to its high rate of recurrence and drug resistance, resulting in a 5-year survival rate of 30% in advanced stages. To elucidate the molecular mechanisms underlying EOC recurrence, we analyzed transcriptome data from patients with EOC and identified elevated USP19, a deubiquitinating enzyme, as being elevated in patients without recurrence in our previous study. Single-cell RNA sequencing analysis revealed that increased USP19 expression in epithelial cells is associated with activation of apoptotic pathways, suggesting that USP19 may inhibit EOC recurrence through deubiquitination of its binding proteins. Using the protein–protein interaction database, we identified DnaJC7 as a binding partner of USP19 and confirmed their interaction experimentally. USP19-mediated deubiquitination of DnaJC7 increases its protein stability. Notably, upregulation of USP19 and DnaJC7 disrupted the interaction between p53 and MDM2, and knockdown of USP19 and DnaJC7 resulted in decreased p53 expression following cisplatin treatment. These findings highlight the therapeutic potential of enhancing the USP19-DnaJC7 axis to stabilize p53 and improve cisplatin efficacy. Promoting USP19-mediated deubiquitination by stabilizing DnaJC7 may offer a novel combination strategy to enhance the efficacy of cisplatin-based cancer therapy.