Xin yixue (Apr 2023)

Promoter hypomethylation promotes proliferation of hepatocellular carcinoma cells by mediating NOL9 overexpression

  • Chen Xiyao, Xu Zhen, Wu Zhebin, Zhang Boxiang, Peng Liang, Xie Chan

DOI
https://doi.org/10.3969/j.issn.0253-9802.2023.04.011
Journal volume & issue
Vol. 54, no. 4
pp. 287 – 293

Abstract

Read online

Objective To evaluate the expression of nucleolar protein 9 （NOL9） in hepatocellular carcinoma and the effect of NOL9 on the proliferation of hepatocellular carcinoma cells， aiming to elucidate the molecular mechanism of NOL9 overexpression in hepatocellular carcinoma. Methods Surgical specimens （cancerous and para-cancerous tissues） were obtained from 7 patients with hepatocellular carcinoma. The expression levels of NOL9 in the cancerous and para-cancerous tissues were determined by Western blot and RT-qPCR. Huh7 and HCCLM3 cell were transferred with NOL9 si-RNA. The differences between two groups were analyzed by RT-qPCR， Western blot， colony formation assay and CCK-8 assay. Hepatocellular carcinoma data from TCGA database were used to evaluate the expression level of NOL9 mRNA and promoter methylation level. The correlation between NOL9 and transcription levels of Ten-eleven-translocation enzymes （TET1， TET2 and TET3） was analyzed. After administration of 5-Aza-Dc， the expression level of NOL9 in Huh7 and HCCLM3 cells was detected by RT-qPCR and Western blot. The cells were pretreated with 5-Aza-Dc and transfected with si-RNA， and then colony formation assay and CCK-8 assay were used to analyze the difference of cell proliferation. Results The expression of NOL9 was up-regulated in hepatocellular carcinoma tissues compared with para-cancerous tissues. Knockdown of NOL9 could significantly inhibit cell proliferation and cell colony formation in Huh7 and HCCLM3 cells （all P < 0.01）. The methylation level of NOL9 promoter was negatively correlated with its mRNA level in hepatocellular carcinoma. NOL9 mRNA level was negatively correlated with one CpG region （cg07997941）. In hepatocellular carcinoma， NOL9 was positively correlated with the transcription levels of TET1， TET2 and TET3. After administration of 5-Aza-Dc， the expression level of NOL9 was up-regulated. Treatment with 5-Aza-Dc could reverse the inhibitory effect of NOL9 knockdown on cell proliferation and colony formation. Conclusion NOL9 is highly expressed in hepatocellular carcinoma tissues. Knockdown of NOL9 suppresses the proliferation and colony formation of hepatocellular carcinoma cells. The mechanism underlying NOL9 up-regulation may be related to promoter hypomethylation.

Keywords