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. 2017 Feb 15;12(2):e0172243.
doi: 10.1371/journal.pone.0172243. eCollection 2017.

Basic studies on epigenetic carcinogenesis of low-dose exposure to 1-trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo) in vitro

Renjie Wang  1   2   3   4 , Yi Cui  2 , Yi Xu  1   3   4   5 , Joseph Irudayaraj  2
Affiliations

Basic studies on epigenetic carcinogenesis of low-dose exposure to 1-trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo) in vitro

Renjie Wang et al. PLoS One. .

Abstract

1-Trichloromethyl-1,2,3,4-tetrahydro-β-carboline (TaClo) has been widely studied as a neurotoxic substance, however, only few reports have explored its effect on carcinogenicity. Since the aberrant modification of DNA methylation occurs very early in almost all human cancers, the focus of this study is to assess the carcinogenicity of TaClo by characterizing alterations of the epigenetic state, specifically, DNA methylation, upon exposure to TaClo in a HEK 293 model cell line. Our results suggest that TaClo could induce global DNA hypomethylation and transcriptional repression of critical tumor suppressor genes by increasing their promoter methylation. Enhanced cell proliferation, migration and anchorage independent growth were observed in cells exposed to TaClo. Our study highlights the epigenetic toxicity of TaClo, which contributes to its carcinogenicity by altering the DNA methylation status.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Low dose exposure to TaClo decreased global DNA methylation.
(a) Global DNA methylation level detected at different time period indicates a gradual decrease due to TaClo exposure. (b) Immunofluorescence images of global DNA methylation of HEK 293 cells treated under different conditions. n = 4 independent replicates. Scale bar, 400 μm.
Fig 2
Fig 2. qRT-PCR analysis of Dnmts and TETs expression changes after TaClo treatment.
The expression of Dnmts had no significant change, meanwhile the expression of TETs experienced a significant increase after TaClo treatment. (n = 4 independent replicates).
Fig 3
Fig 3. Promoter hypermethylation of selected tumor suppresser genes was observed after low dose exposure to TaClo.
Fig 4
Fig 4. Increased methylation level of selected CpG sites in BRCA1 promoter region induced by lower concentration of TaClo exposure for a prolonged period of time.
Fig 5
Fig 5. qRT-PCR analyses results of selected tumor suppressor gene expression.
(a) Expression of promoter hypermethylated tumor suppressor genes significantly decreased. (b) Heat map for the transcriptional changes of promoter hypermethylated tumor suppresser genes.
Fig 6
Fig 6. Growth curves of control and TaClo treated HEK 293 cells.
Statistically significant difference was observed in day 6.
Fig 7
Fig 7. Analysis of cell migration by in vitro scratch assay.
Images were acquired at 0 and 18 h. Scale bar, 400 μm.
Fig 8
Fig 8. Anchorage independent growth of control and TaClo treated HEK 293 cells.
After TaClo treatment, the fluorescence intensities increased around 1.5 fold.
See this image and copyright information in PMC

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