No abstract

Deubiquitinases (DUBs) have important biological functions, but their roles in breast cancer metastasis are not completely clear. In this study, through screening a series of DUBs related to breast cancer distant metastasis-free survival (DMFS) in the Kaplan-Meier Plotter database, we identified ubiquitin-specific protease 12 (USP12) as a key deubiquitinating enzyme for breast cancer metastasis. We confirmed this via an orthotopic mouse lung metastasis model. We revealed that the DMFS of breast cancer patients with high USP12 was worse than that of others. Knockdown of USP12 decreased the lung metastasis ability of 4T1 cells, while USP12 overexpression increased the lung metastasis ability of these cells in vivo. Furthermore, our results showed that the supernatant from USP12-overexpressing breast cancer cells could promote angiogenesis according to human umbilical vein endothelial cell (HUVEC) migration and tube formation assays. Subsequently, we identified midkine (MDK) as one of its substrates. USP12 could directly interact with MDK, decrease its polyubiquitination and increase its protein stability in cells. Overexpression of MDK rescued the loss of angiogenesis ability mediated by knockdown of USP12 in breast cancer cells in vitro and in vivo. There was a strong positive relationship between USP12 and MDK protein expression in clinical breast cancer samples. Consistent with the pattern for USP12, high MDK expression predicted lower DMFS and overall survival (OS) in breast cancer. Collectively, our study identified that USP12 is responsible for deubiquitinating and stabilizing MDK and leads to metastasis by promoting angiogenesis. Therefore, the USP12–MDK axis could serve as a potential target for the therapeutic treatment of breast cancer metastasis.

Background: Metastasis is the leading cause of the high morality of esophageal squamous cell carcinoma (ESCC), so early monitoring metastasis of esophageal cancer is the key to improve the survival rate of ESCC patients. However, there have not been effective biomarkers for predicting metastasis of ESCC patients,it is an urgent need to identify ESCC metastasis-related proteins. Methods: iTRAQ-based proteomic method was performed in highly metastatic 30M cell established in our previous study and the corresponding parental cells KYSE30.The expression of IFI16 was verified using western blotting and immunohistochemistry (IHC). Then, cck8, transwell assay,mouse metastasis experiments were performed to determine the functional role of IFI16 in esophageal cancer. Finally, RAN-Seq, qpcr, transwell assay were used to investigate the underlying mechanism of IFI16 in esophageal cancer metastasis. Results: The data showed that IFI16 was upregulated in 30M cell compared with KYSE30 cell. IFI16 also increased in ESCC tumor compared with non-tumor tissue. Kaplan-Meier survival curve analysis showed that the relapse-free survival (RFS) of patients with high IFI16 level was worse than that of patients with low IFI16 level (P=0.0449). In addition, IFI16 knockdown did not affect the cell growth, but inhibited ESCC cell migration and invasion in ESCC cells. Moreover, IFI16 knockdown suppressed the lung metastasis of 30M cells in mouse models. Finally, we performed an RNA-Seq assay in IFI16-knocking down 30M cells and identified that knocking down IFI16 downregulated the expression of fibroblast growth factor proteins (FGF1, FGF2 etc.). Furthermore, overexpressing FGF1 and FGF2 rescued the lost of migration and invasion ability of 30M mediated by IFI16 knockdown. Conclusion: Our results demonstrated that IFI16 was a key ESCC metastasis-related protein and played a role in ESCC metastasis through promoting the FGF proteins expression.