Introduction: The current prognosis of hepatocellular carcinoma (HCC) is unsatisfactory due to high rates of recurrence and metastasis, which has led to research focused on the discovery of metastasis genes.
Methods: In this study, we combined in silico analysis and in vitro transwell experiments to identify a metastasis gene. Then, we used an in vivo experiment to validate the metastasis. Furthermore, a series of experiments such as FACS, Western blot, and ELISA were applied to explore the function of the metastasis gene.
Results: LTBP4  (latent transforming growth factor beta binding protein 4) was confirmed as a metastasis gene, whose expression levels are correlated with the overall survival rate of HCC patients. We further showed that the knockout of LTBP4  in an HCC cell line increased cell proliferation, activated the cell cycle, and induced metastasis events. Moreover, we proved that LTBP4-KO could increase the percentage of active TGFβ 1 secreted by HCC cell lines, as well as the recruitment of MDSCs (myeloid-derived suppressor cells) by active TGFβ 1 (transforming growth factor beta 1), which further inhibited CD8+ T cell proliferation and activated the immune suppression signal.
Conclusion: Our results demonstrate that the LTBP4-TGFβ 1-MDSCs axis is a critical pathway for the immune suppression signals of HCC primary tumors.
Keywords: hepatocellular carcinoma, LTBP4, TGFβ 1, MDSCs, T cell proliferation