Expression of glutathione S-transferase M2 in stage I/II non-small cell lung cancer and alleviation of DNA damage exposure to benzo[a]pyrene

Glutathione S-transferases (GSTs) are a family of inducible enzymes that are important in carcinogen detoxification GST-Mu class is showing the high activity towards most polycyclic aromatic hydrocarbon (PAH) epoxide Our objective is to clarify the expression of GST-M2 in non-small-cell lung carcinoma (NSCLC) patients and to determine the role of GST-M2 in protecting against DNA damage. We detected changes in GST-M2 expression at mRNA levels with a panel of lung cell lines and clinical samples of malignant and paired adjacent non-malignant tissues from 50 patients with stage I or II non-small-cell lung carcinoma using real-time RT-PCR Comet assay and gamma-H2AX were used to clarify whether DNA damaged was protected by GST-M2 Our data demonstrate that the expression of GST-M2 in tumor tissues is significantly lower than in paired adjacent non-malignant tissues (p = 0 016) Loss of GST-M2 is closely associated with age, gender, T value, N value and cell differentiation (p < 0.05) in early stage I/II patients Downregulation of GST-M2 is mediated through aberrant hypermethylation in lung cancer cell lines. Protection against B[a]P-induced DNA damage by GST-M2 in lung cancer cells was detected by Comet assay and gamma-H2AX. In conclusion, DNA hypermethylation altered and reduced GST-M2 expression that resulted in susceptible to benzo[a]pyrene (B[a]P) induced DNA damage It implies that GST-M2 reduction occurs prior to tumorigenesis (C) 2009 Elsevier Ireland Ltd All rights reserved