Poly(ADP-ribose) glycohydrolase silencing down-regulates TCTP and Cofilin-1 associated with metastasis in benzo(a)pyrene carcinogenesis

Benzo(a)pyrene (BaP) is a ubiquitously distributed environmental pollutant. BaP is a known carcinogen and can induce malignant transformation of rodent and human cells. Many evidences suggest that inhibitor of poly(ADP-ribose) glycohydrolase (PARG) is potent anticancer drug candidate. However, the effect of PARG on BaP carcinogenesis remains unclear. We explored this question in a PARG-deficient human bronchial epithelial cell line (shPARG cells) treated with various concentration of BaP for 15 weeks. Soft agar assay was used to examine BaP-induced cell malignancy of human bronchial epithelial cells and shPARG cells. Mechanistic investigations were used by 2D-DIGE and mass spectrometry. Western blot analysis and Double immunofluorescence detection were used to confirm some of the results obtained from DIGE experiments. We found that PARG silencing could dramatically inhibit BaP-induced cell malignancy of human bronchial epithelial cells in soft agar assay. Altered levels of expression induced by BaP were observed within shPARG cells for numerous proteins, including proteins required for cell mobility, stress response, DNA repair and cell proliferation pathways. Among these proteins, TCTP and Cofilin-1 involved in malignancy, were validated by western blot analysis and immunofluorescence assay. PARG inhibition contributed to down-regulation of TCTP and Cofilin-1. This is the first experimental demonstration of a link between PARG silencing and reduced cell migration after BaP exposure. We propose that PARG silencing might down-regulate TCTP and Cofilin-1 associated with metastasis in BaP carcinogenesis.