Aberrant methylation of RUNX3 is present in Aflatoxin B1-induced transformation of the L02R cell line. (15th June 2017)

• Record Type: Journal Article
• Authors: Wang, Shan; He, Zhini; Li, Daochuan; Zhang, Bo; Li, Miao; Li, Wenxue; Zhu, Wei; Xing, Xiumei; Zeng, Xiaowen; Wang, Qing; Dong, Guanghui; Xiao, Yongmei; Chen, Wen; Chen, Liping
• Is Part Of: Toxicology. Volume 385(2017)
• Page Start: 1
• Page End: 9
• Publication Date: 2017-06-15
• Subjects: TXNRD1 thioredoxin reductase 1 -- PCNA proliferating cell nuclear antigen -- CCNK cyclin K -- DIAPH3 diaphanous-related formin 3 -- RAB27B ras-related protein rab-27B -- HIST1H2BF histone cluster 1, H2bf -- HMG20B high-mobility group 20B -- JUNB jun B proto-oncogene -- NAV1 neuron navigator 1 -- POLL DNA polymerase lambda -- RUNX3 runt-related transcription factor 3 -- CFLAR CASP8 and FADD-like apoptosis regulator -- CXCR4 chemokine (C-X-C motif) receptor 4 -- INTS1 integrator complex subunit 1 -- MAP3K6 mitogen-activated protein kinase kinase kinase 6 -- RARRES1 retinoic acid receptor responder 1; Aflatoxin B1 -- RUNX3 -- DNA methylation -- Human cell transformation; Toxicology -- Periodicals; Chemicals -- Physiological effect -- Periodicals; 615.9005
• DOI: 10.1016/j.tox.2017.04.011
• Languages: English
• ISSNs: 0300-483X

Abstract

Abstract: Chronic exposure to aflatoxin B1 (AFB1 ) is linked to the development of hepatocellular carcinoma (HCC). To identify differentially methylated genes involved in AFB1 -induced cell transformation, we analyzed DNA methylation patterns in immortal human hepatocyte L02 cells expressing an oncogenic H-Ras allele (L02R cells) and AFB1 -transformed L02R (L02RT-AFB1 ) cells by performing genome-wide methylation profiling. We treated L02R cells with 0.3 μM AFB1 weekly and observed a transformed phenotype at the 17th week post-treatment. The transformed cells (L02RT-AFB1 ) could grow in an anchorage independent fashion and form tumors in immunodeficient mice. qRT-PCR was performed to examine whether gene methylation led to a reduction in gene expression of methylated candidate genes. As a result, the expression of the following seven genes including JUNB, RUNX3, NAV1, CXCR4, RARRES1, INTS1, and POLL was down-regulated in transformed L02RT-AFB1 cells. The reduction of gene expression of these genes could be reversed by treatment of 5-azadeoxycytidine. The methylated CpG sites of RUNX3 genes were verified using bisulfite sequencing PCR (BSP) assay. Furthermore, a dynamic change in RUNX3 methylation was observed over the course of AFB1 -induced cell transformation, which was corresponded to the alteration of gene expression and the extent of DNA damage. In vitro study showed that methylation of RUNX3 tended to abate in L02R cells treated with AFB1 for a short-term period of time. Notably, hypermethylation of RUNX3 appeared in 70% (14/20) of human hepatocellular carcinomas. Moreover, LINE-1 hypomethylation and dynamic changes of DNMTs, TETs and MeCP2 expression were also observed during AFB1 -induced transformation. Taken together, these observations suggest that aberrant methylation of RUNX3 and LINE-1 might be involved in AFB1 -induced carcinogenesis.