8-hydroxyguanine and Pancreatic-Neoplasms

In pancreatic Panc-1 cancer cells, an increase of oxidative stress enhances the level of 7,8-dihydro-8-oxoguanine (8OG) more in the

Topics: Benzimidazoles; Cell Line, Tumor; DNA-Binding Proteins; G-Quadruplexes; Gene Expression Regulation, Neoplastic; Gene Silencing; Guanine; Heterogeneous Nuclear Ribonucleoprotein A1; Humans; Hydrogen Peroxide; Oxidative Stress; Pancreatic Neoplasms; Poly (ADP-Ribose) Polymerase-1; Promoter Regions, Genetic; Proto-Oncogene Proteins p21(ras); Transcription Factors; Up-Regulation

Elevated levels of oxidatively induced DNA lesions have been reported in malignant pancreatic tissues relative to normal pancreatic tissues. However, the ability of the pancreatic cancer cells to remove these lesions has not previously been addressed. This study analyzed the effectiveness of the pancreatic cancer cell line, BxPC-3 to repair 8-hydroxyguanine (8-OH-Gua) relative to a nonmalignant cell line. We show that BxPC-3 cells repair 8-OH-Gua less effectively than the nonmalignant cells. This repair deficiency correlated with significant downregulation of the hOGG1 protein and the corresponding mRNA (30-fold lower than GAPDH) in BxPC-3 cell line. The repair defect was complemented in vivo by transient transfection of the hOGG1 gene and in vivo by recombinant hOGG1. These results are the first to show a deficiency of 8-OH-Gua repair in BxPC-3 cells, implicating this defect in the risk factor of pancreatic cancer.

Topics: Cell Line, Tumor; DNA Damage; DNA Glycosylases; DNA Repair; Genetic Complementation Test; Guanine; Humans; Pancreatic Neoplasms; Recombinant Proteins; Risk Factors; RNA, Messenger

The breast and ovarian cancer susceptibility genes, BRCA1 and BRCA2, are likely to participate in DNA lesion processing. Oxidative lesions, such as 8-oxoguanine, occur in DNA after endogenous or exogenous oxidative stress. We show that deficiency for either BRCA1 or BRCA2 in human cancer cells leads to a block of the RNA polymerase II transcription machinery at the 8-oxoguanine site and impairs the transcription-coupled repair of the lesion, leading to a high mutation rate. Expression of wild-type BRCA1 from a recombinant adenovirus fully complements the repair defect in BRCA1-deficient cells. These results represent the first demonstration of the essential contribution of BRCA1 and BRCA2 gene products in the repair of the 8-oxoguanine oxidative damage specifically located on the transcribed strand in human cells. This suggests that cells from individuals predisposed to breast and/or ovarian cancer may undergo a high rate of mutations because of the deficiency of this damage repair pathway after oxidative stress.

Topics: Adenoviridae; BRCA1 Protein; BRCA2 Protein; Breast Neoplasms; Cell Line, Transformed; DNA Damage; DNA Repair; Female; Fibroblasts; Genes, BRCA1; Genetic Vectors; Germ-Line Mutation; Guanine; Humans; Neoplasm Proteins; Oxidative Stress; Pancreatic Neoplasms; Recombinant Proteins; RNA Polymerase II; Transcription Factors; Transcription, Genetic; Transfection