Published online Mar 15, 2022. doi: 10.4251/wjgo.v14.i3.664
Peer-review started: July 27, 2021
First decision: October 3, 2021
Revised: November 10, 2021
Accepted: February 10, 2022
Article in press: February 10, 2022
Published online: March 15, 2022
O6-methylguanine-DNA methyltransferase (MGMT) is a specific enzyme that repairs the mispairing base O6-methyl-guanine induced by methylating environmental and experimental carcinogens. The N-nitroso compounds (NOCs) N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) and N-methyl-N-nitroso-urea (MNU) are monofunctional alkylating agents which can directly bind to the DNA and induce the formation of O6-methylguanine adducts to promote gene mutation and tumorigenesis. They are widely accepted chemical carcinogens for studying the mechanisms of mutagenesis and carcinogenesis induced by NOCs.
The underlying regulatory mechanism of MGMT involved in NOCs-induced tumorigenesis, especially in the initiation phase, remains largely unclear.
To investigate the molecular regulatory mechanism of MGMT in NOCs-induced gastric cell malignant transformation and tumorigenesis.
We established a gastric epithelial cell malignant transformation model induced by MNNG or MNU treatment. Cell proliferation, colony formation, soft agar, cell migration, and xenograft assays were used to verify the malignant phenotype. By using quantitative real-time polymerase chain reaction (qPCR) and Western blot analysis, we detected the MGMT expression in malignant transformed cells. We also confirmed the MGMT expression in clinical early stage gastric tumor tissues by qPCR and immunohistochemistry. MGMT gene promoter DNA methylation level was analyzed by methylation-specific PCR and bisulfite sequencing PCR. The effect of MGMT in cell malignant transformation was analyzed by colony formation and soft agar assays.
MGMT expression was upregulated in NOCs-induced gastric cell malignant transformation and in clinical early stage gastric cancer tissues. The upregulation of MGMT was regulated by the hypo
The upregulation of MGMT expression is mediated by the hypomethylation of its DNA promoter in NOCs-induced gastric cell malignant transformation.
The findings provide a dynamic regulatory mechanism of MGMT expression in cell malignant transformation and tumorigenesis induced by NOCs, supporting that MGMT might be a potential diagnostic and therapeutic target for gastric carcinogenesis.