Abstract
BACKGROUND: Liver metastasis is a leading cause of colorectal cancer mortality. Therefore, the underlying mechanism and potential therapeutic target of colorectal cancer liver metastasis urge to be found. Mounting evidence indicates that cancer-derived sialylated IgG promotes tumor formation and progression. However, the role of sialylated IgG in colorectal cancer liver metastasis remains undefined. MATERIALS AND METHODS: Analysis of sialylated IgG in paired tumor tissues and adjacent normal tissues from 65 colorectal cancer patients was performed using immunohistochemical staining. Functional assays of sialylated IgG were explored in vitro and in vivo. The downstream target of sialylated IgG was investigated by performing gene-set enrichment analysis, ubiquitination assay, cycloheximide chase assay, acetylation assay and co-immunoprecipitation. RESULTS: Here, our investigation reveals that sialylated IgG is significantly upregulated in colorectal cancer and that the increase of IgG is positively associated with liver metastasis and poor overall survival in colorectal cancer patients. Sialylated IgG promotes colorectal cancer cell migration, invasion and liver metastasis. Notably, anti-sialylated IgG antibody effectively blocks colorectal cancer liver metastasis in mouse models. Mechanistically, sialylated IgG upregulates c-Myc protein level by decreasing c-Myc ubiquitination. Moreover, we find that p300/CBP can stabilize c-Myc by reducing c-Myc ubiquitination. Overexpression of p300/CBP protects c-Myc protein level from sialylated IgG-knockdown in a lysine acetyltransferase activity-dependent manner. Furthermore, sialylated IgG upregulates p300 protein level through integrin β4-FAK-Src-Erk signaling. CONCLUSION: Collectively, these results indicate that a novel sialylated IgG-integrin β4-FAK-Src-Erk-p300-c-Myc signaling pathway promotes colorectal cancer liver metastasis, thus providing potential therapeutic targets for colorectal cancer liver metastasis.