Carcinogenesis
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Comparative Study
Association of the DNA repair gene XPD Asp312Asn polymorphism with p53 gene mutations in tobacco-related non-small cell lung cancer.
Lung cancer, a disease related mostly to tobacco smoke exposure and a leading cause of cancer-related death in industrialized countries, is frequently associated with mutations in the p53 tumor suppressor gene. Genetic differences resulting in inter-individual variation in DNA repair capacity may in part account for susceptibility of a cell to genotoxic agents leading to somatic mutations, including p53 mutations, and eventual transformation of a normal cell into a malignant phenotype. The objective of this study is to investigate the relationship between the polymorphisms of two DNA repair genes, the nucleotide excision repair xeroderma pigmentosum group D (XPD) gene (codons 312 and 751) and the base excision repair X-ray repair cross-complementing group 1 (XRCC1) gene (codon 399), and p53 mutations among lung cancer patients. ⋯ No association was found between p53 mutations and either XPD Lys751Gln or XRCC1 Arg399Gln. However, the p53 mutation frequency increased with the increased number of the combined genotypes among XPD 312WT (Asp/Asp), XPD 751VT (Lys/Gln or Gln/Gln) or XRCC1 399VT (Arg/Gln or Gln/Gln) (P = 0.01, trend test). These results suggest that individuals who smoke and have the XPD codon 312 Asp/Asp genotype may be at a greater risk of p53 mutations, especially if combined with other polymorphisms that may result in deficient DNA repair.
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Comparative Study
CYP1A1 and GSTM1 genetic polymorphisms and lung cancer risk in Caucasian non-smokers: a pooled analysis.
Polymorphisms for genes encoding the metabolic enzymes cytochrome P450 1A1 (CYP1A1) and glutathione S-transferase M1 (GSTM1) might contribute to the variability in individual susceptibility to lung cancer. The role of CYP1A1 and GSTM1 in lung carcinogenesis might be more important at low levels of exposure to carcinogens. Non-smokers represent a population at low exposure, however, they are often overlooked because of the small number of cases. ⋯ The OR for the combination of the CYP1A1 Ile(462)Val variant and GSTM1 null genotype was 4.67 (95%CI 2.00-10.9) compared with the concurrent presence of the CYP1A1 wild-type and GSTM1 non-null genotype. We did not observe a modification of the effect of the GSTM1 null genotype according to exposure to environmental tobacco smoke and urban/rural residence. Our study therefore suggests that the CYP1A1 Ile(462)Val variant allele might play a role in lung carcinogenesis among non-smokers, possibly in combination with the GSTM1 null genotype.
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We recently identified PRIMA-1 as a low molecular weight compound that restores tumor suppressor function to mutant p53 proteins and has anti-tumor activity in vivo (1). Here we report the statistical analysis of the effect of PRIMA-1 on a panel of human tumor cell lines using information available in a database at the Developmental Therapeutics Program of the National Cancer Institute (NCI). We extracted growth inhibition profiles for PRIMA-1 and 44 known anticancer agents, p53 status of cell lines, population doubling time, and level of p53 protein expression from the NCI database. ⋯ In contrast, none of several known anticancer drugs showed such preference. PRIMA-1 inhibited the growth of cell lines derived from various human tumor types in a mutant p53-dependent manner. This distinguishes PRIMA-1 from known anticancer drugs and supports the idea that PRIMA-1 can serve as a lead for the development of novel therapeutic compounds.
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The accumulating evidence that erythropoietin and erythropoietin receptor are expressed in various non-haematopoietic organs suggests that erythropoietin signalling might be involved in the growth of tumours, but this possibility has never been examined. We found that mRNAs for erythropoietin and erythropoietin receptor are expressed in malignant tumours of female reproductive organs, where erythropoietin levels are higher than in normal tissues. Furthermore, tumour cells and capillary endothelium showed erythropoietin receptor immunoreactivity. ⋯ Moreover, reduced tyrosine phosphorylation of STAT5 in the experimental blocks was confirmed by western blotting analysis. The results strongly indicate that erythropoietin signalling contributes to the growth and/or survival of both transformed cells and capillary endothelial cells in these tumours. Thus, deprivation of erythropoietin signalling may be a useful therapy for erythropoietin-producing malignant tumours.
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Tangeretin (5,6,7,8,4'-pentamethoxyflavone) is concentrated in the peel of citrus fruits. DNA flow cytometric analysis indicated that tangeretin blocked cell cycle progression at G1 phase in colorectal carcinoma COLO 205 cells. Over a 24 h exposure to tangeretin, the degree of phosphorylation of Rb was decreased after 12 h and G1 arrest developed. ⋯ Tangeretin also increased the content of the Cdk inhibitor p21 protein and this effect correlated with the elevation in p53 levels. In addition, tangeretin also increased the level of the Cdk inhibitor p27 protein within 18 h. These results suggest that tangeretin either exerts its growth-inhibitory effects through modulation of the activities of several key G1 regulatory proteins, such as Cdk2 and Cdk4, or mediates the increase of Cdk inhibitors p21 and p27.