Abstract:

Objective ·To investigate the biological functions of ubiquitin-specific protease 37 (USP37) in the development and progression of hepatoblastoma (HB), and to explore the molecular mechanism by which USP37 promotes tumor progression through regulation of the protein stability of myelocytomatosis viral oncogene homolog (c-MYC). Methods ·Relevant literature published in the PubMed database up to March 31, 2026, was searched. HB transcriptomic data and clinicopathological characteristics were integrated to systematically screen USP family members potentially involved in the regulation of c-MYC protein stability. Real time fluorescent quantitative polymerase chain reaction (qPCR) and receiver operating characteristic (ROC) curve analysis were performed to validate the expression pattern and diagnostic performance of USP37. Exploratory survival analysis was conducted using the hepatocellular carcinoma cohort from the Kaplan-Meier Plotter database. Stable USP37 knockdown models were established in HuH6 and HepG2 cells. Cell proliferation and colony formation assays were performed to evaluate the biological functions of USP37, and rescue experiments were conducted using an shRNA-resistant USP37 expression vector. qPCR, Western blotting, cycloheximide (CHX) chase assays, proteasome inhibition assays, co-immunoprecipitation (Co-IP), and deubiquitination assays were performed to investigate the regulatory effects of USP37 on c-MYC expression and protein stability. Results ·Through integrated screening based on literature evidence, transcriptomic differential expression, and clinicopathological characteristics, USP37 was identified as a potential key regulatory molecule in HB. Analysis of clinical samples and public databases showed that USP37 was significantly upregulated in HB tissues. ROC curve analysis based on qPCR results from eight paired HB and adjacent non-tumor tissues yielded an area under the curve (AUC) of 0.942 7, indicating that USP37 could discriminate HB tissues from adjacent non-tumor tissues. Clinicopathological analysis of 33 patients with HB showed that high USP37 expression was significantly associated with tumor metastasis (P=0.028) and increased tumor volume (P=0.031). In vitro functional assays demonstrated that USP37 knockdown significantly inhibited the proliferation and colony-forming ability of HuH6 and HepG2 cells, whereas USP37 re-expression effectively rescued the proliferation-inhibitory phenotype. Mechanistically, USP37 overexpression increased c-MYC protein levels in a dose-dependent manner but did not significantly affect c-MYC mRNA expression. Conversely, USP37 knockdown significantly reduced c-MYC protein levels without markedly altering its mRNA expression. CHX chase assays showed that USP37 overexpression prolonged the half-life of c-MYC protein in 293T cells from 2.357 h to 4.796 h (P=0.006), whereas USP37 knockdown shortened the half-life of c-MYC protein in HuH6 and HepG2 cells from 1.504 h and 1.585 h to 0.986 h and 0.792 h, respectively (P=0.006 and 0.005). MG132 treatment restored c-MYC protein levels in USP37-knockdown cells. Reciprocal Co-IP assays further confirmed the interaction between USP37 and c-MYC, while deubiquitination assays demonstrated that USP37 overexpression reduced the ubiquitination level of c-MYC. Conclusion ·USP37 functions as a key deubiquitinase that promotes HB cell proliferation and tumor progression by stabilizing c-MYC protein, suggesting that the USP37-c-MYC axis may serve as a potential therapeutic target.

Key words: ubiquitin-specific protease 37 (USP37), myelocytomatosis viral oncogene homolog (c-MYC), hepatoblastoma, protein stability, deubiquitination