The tripartite motif (TRIM) protein family is a highly conserved group of E3 ligases with 77 members known in the human, most of which consist of a RING-finger domain, one or two B-box domains, and a coiled-coil domain. Generally, TRIM proteins function as E3 ligases to facilitate specific proteasomal degradation of target proteins. In addition, E3 ligase independent functions of TRIM protein were also reported. In hepatocellular carcinoma, expressions of TRIM proteins are both regulated by genetic and epigenetic mechanisms. TRIM proteins regulate multiple biological activities and signaling cascades. And TRIM proteins influence hallmarks of HCC. This review systematically demonstrates the versatile roles of TRIM proteins in HCC and helps us better understand the molecular mechanism of the development and progression of HCC.
Background Hepatocellular carcinoma (HCC) is one of the most common cancers with the highest mortality rate in the world. Receptor tyrosine kinases play an important role in the occurrence and development of cancer. Discoid protein domain receptors 1 (DDR1) are a special type of transmembrane receptor tyrosine kinase. Here, we show DDR1 is significantly increased in Hepatocellular carcinoma(HCC), which is related to poor prognosis of HCC patients. Methods DDR1 expression in HCC cell lines and paired HCC specimens were determined by western blot and immunohistochemistry (IHC). At the same time, the correlation between the DDR1 and SLC1A5 was also studied in HCC specimens. Cell proliferation ability were evaluated by CCK8 and colony formation assays. Knock-down and overexpression experiments, CHX, NH4CL and Mg132 intervention experiments, Immunoprecipitation experiments, and nude mouse xenograft models were used to determine the potential mechanism by which DDR1 promotes tumorigenesis in vitro and in vivo. Results In this study, we find that overexpression of DDR1 promotes the proliferation of HCC cells and accelerates the growth of tumor xenografts, while downregulation of DDR1 has the opposite effect. We also proved that loss or gain of DDR1 could affect the cell cycle progression of liver cancer cells. Mechanistically, DDR1 interacts with the SLC1A5 that belongs to the solute carrier (SLC) family of transporters and regulates its stability, thereby regulating the mTORC1 signaling pathway. In addition, we found that the regulation of SLC1A5 by DDR1 can be restored by lysosome inhibitors. Otherwise, we found that DDR1 was highly expressed in HCC and elevated DDR1 expression predicted shorter overall survival (OS) time for HCC patients. We further revealed that the expression of SLC1A5 was positively correlated with DDR1.In summary, our data shows that DDR1 is a tumor-promoting factor that can control cell proliferation and cell cycle by stabilizing SLC1A5 in a lysosome-dependent pathway, which provides a new treatment target for HCC. Conclusions This study reveals a new mechanism through which DDR1 can play the role of cancer-promoting genes in the progression of liver cancer. We also found that the expression of DDR1 is an independent prognostic indicator of OS, and the expression of DDR1 and SLC1A5 are positively correlated in clinical samples. Our findings provide a new perspective for understanding the development of HCC, which may provide new targets for the treatment and management of this challenging cancer.
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