Abstract 2445: PPM1G enhances hepatocellular carcinoma stemness via interacting with YBX1

Abstract

Abstract PPM1G is a member of protein phosphatase family, marked as Mg2+/Mn2+ dependent 1G. PPM1G protein mainly has three domains: phosphatase domains at both ends and acidic domain (AD) in the middle. It was highly expressed in both embryonic stem cells and hepatocellular carcinoma (HCC) by mRNA-seq data. From pan-cancer view, it was up-regulated in tumor tissue of 24 pan-cancer types and predicted worse overall survival (OS) for 9 cancers. In GSE40267 dataset, PPM1G overexpressed significantly in lung metastasis HCC patients than patients without metastasis. And both from TCGA and ICGC-JP database analysis showed PPM1G was an independent poor prognostic factor for both OS and disease-free survival (DFS) in HCC patients. In vitro, our functional experiments showed that the stemness features such as sphere formation, ALDH assay and atRA (Tretinoin) assay were undermined by knock down (KD) of PPMIG. In HepG2 and 8024 KD cell lines, the tumor capacity of proliferation, cell-cycle, foci-formation, migration invasion and cisplatin induced apoptosis were also impaired. In vivo, KD of PPM1G strongly suppressed the subcutaneous and liver orthotopic tumor formation and lung metastasis and cancer stemness by limited dilution experiment was also significantly weakened. For the mechanism exploration, firstly, GO analysis showed genes highly positive correlated with PPM1G (Spearman R > 0.5) enriched in mRNA splicing. Secondly, YBX1 (role as RNA m5C and m6A reader protein and chemotherapy resistance gene) was screened out by three database (RBP2GO, HiPredict and GEPIA) followed with in vivo CO-IP experiment and immunofluorescence colocalization. The YBX1 expression level was not affected by PPM1G from Western Blot. Lastly, the AD of PPM1G but not the phosphatase domain was interacted with YBX1 by PPM1G cut-off and CO-IP experiments. So, the above evidence proved that PPM1G could interact with YBX1 to promote HCC stemness and tumor growth and metastasis. Citation Format: Shan Liu, Xiaona Fang, Jie Luo, Jiao Huang, Yuma Yang, Beilei Liu, Jinlin Huang, Ching Ngar Wong, Baifeng Zhang, Lanqi Gong, Liuxian Ban, Qian Yan, Xinyuan Guan. PPM1G enhances hepatocellular carcinoma stemness via interacting with YBX1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2445.