Abstract 848: Hyper O-GlcNAcylation plays an oncogenic role in hepatocellular cancer
Authors: Nie Yongzhan , Chu Yi , Fan Daiming , Jiang Mingzuo , Wu Nan , Li Hongwei 
Published: August 2019

Background: It is universally accepted that change of specific proteins is of great significance in the development of tumor and post translational modification (PTM) is a major way to modify protein activity. O-GlcNAcylation,as one of post translational modifications of proteins regulated by OGT and OGA, has linked glucose metabolism disorders with the malignancies. Numerous studies have demonstrated the aberrant activation of O-GlcNAcylation and OGT in tumors. The aim of this study is to investigate the potential role and underlying mechanisms of O-GlcNAcylation in HCC progression.

Methods: The level of O-GlcNAcylation was detected by IHC staining and western blot. Function of O-GlcNAcylationin HCC proliferation was investigated by CCK8, BrdU, colony forming, cell cycle assay and subcutaneous xenograft tumor model. Scratch healing, transwell assay and 3D spheroid invasion assay were employed for testing metastatic ability of cells. Moreover, Mass-spectrum and co-IP assay were performed to explore novel OGT binding proteins.

Results: Total O-GlcNAcylation level of proteins was markedly overexpressed in HCC compared to adjacent normal tissues and the upregulation of O-GlcNAcylation was associated with poor outcome of patients. The results of in vitro and vivoexperiments showed consistently that high level of O-GlcNAcylation could promote HCC proliferation and metastasis. A large number of studies show that the O-GlcNAcylation of key protein is the crucial step for O-GlcNAcylation regulation in tumor. We examined the mass spectrum results of HCC cell line IP-OGT samples and found 214 eligible candidates. Then GO annotation and the KEGG pathway analysis was employed to try to find targets within the tumor related range. Among the potential candidates which could related to tumor transcription misregulation, we find out that SIX1 which could regulate a series of downstream oncogenic factors and glycolysis related genes including c-myc, cyclin D1, GLUT1 and ENO1 to be a possible effect factor of O-GlcNAcylation. The further data demonstrated that SIX1 was modified by O-GlcNAcylation, and O-GlcNAcylation could maintain the high expression status of SIX1 by inhibiting its

ubiquitination degradation.

Conclusions: In conclusion, our data suggest that O-GlcNAcylation significantly increased in HCC compared to normal tissues. The high expression of O-GlcNAcylation could be an independent prognostic factor in HCC and was associated with poor outcome of patients. Further, we find out SIX1 was the underlying executor of O-GlcNAcylation in HCC. By inhibiting SIX1 ubiquitination, O-GlcNAcylation could maintain SIX1 and its downstream factors in a high level persistently and therefore promote HCC progression. Here in our study, we for the first time identified a neo-posttranslation O-GlcNAcytion modification pathway in HCC, which could provide potential therapy for HCC treatment.

Citation Format: Yongzhan Nie, Yi Chu, Daiming Fan, Mingzuo Jiang, Nan Wu, Hongwei Li. Hyper O-GlcNAcylation plays an oncogenic role in hepatocellular cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 848.