Genetic polymorphisms of superoxide dismutase-1 A251G and catalase C-262T with the risk of colorectal cancer.

Oxidative stress is significant in numerous types of disease including cancer. To protect cells and organs against reactive oxygen species (ROS), the body has evolved an antioxidant protection system that involved in the detoxification of ROS. Single nucleotide polymorphisms (SNP) of anti-oxidative enzymes may dramatically change the activity of the encoded proteins; therefore, certain alleles can be established as risk factors for some kind of multi-factorial diseases including cancer. In present study we investigate the possible association between polymorphisms of superoxide dismutase 1 (SOD1, OMIM: 147450) and catalase (CAT, OMIM: 115500) genes and the risk of colorectal cancer (CRC). The study included 204 colorectal cancer patients and 239 healthy control group matched for gender and age. Genotyping of SOD1 A251G and CAT C-262T were done by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. There was no significant association between CAT C-262T polymorphism and susceptibility to CRC (P>0.05). The carries of the G allele of SOD1 significantly showed higher prevalence in CRC patients compared with the control group (OR=1.84, 95% CI=1.13-2.98, P=0.013). We assessed the effect of combination of genotypes of the study polymorphisms on the risk of CRC. We found that the combination of AG+GG (SOD1) and CC (CAT) increases the risk of developing CRC (OR=2.38, 95% CI=1.25-4.52, P=0.008).

Susceptibility to Colorectal Cancer and Two Genetic Polymorphisms of XRCC4.

The X-ray complementing group 4 (XRCC4, OMIM: 194363) plays a key role in non-homologous end-joining DNA repair pathway in mammalian cells. This pathway is believed to help maintain genomic stability. In the present study, it is hypothesized that genetic polymorphisms in the NHEJ repair XRCC4 gene may be associated with an increased risk in developing colorectal cancer (CRC). We genotyped two polymorphisms of XRCC4, G-1394T (rs6869366) and intron 3 insertion/deletion (I/D; rs28360071) in 200 colorectal cancer patients as well as 256 healthy individuals, and evaluated their association with CRC. We found that in G-1394T polymorphism, neither the TG nor the GG genotypes (versus the TT genotype) were associated with the risk of developing CRC. The results of our study indicate that in comparison with the II genotype, ID and DD genotypes had no significant association with the risk of developing CRC. Subjects with TT genotype and positive family history in colorectal cancer were found to be at a much lower risk of developing CRC in comparison with the reference group (OR = 0.31, 95%CI: 0.11-0.85, P = .023). It should be noted that participants having at least one G allele (TG+GG genotypes) were at a significantly higher risk to develop the disease compared with the reference group (OR = 9.10, 95%CI: 2.00-41.3, P = 0.004). In relation to I/D polymorphism, among participants, those with positive family history, either with ID (OR = .78, 95%CI: 2.26-10.0, P < 0.001) or DD genotypes (OR = 5.73, 95%CI: 1.99-16.4, P = 0.001) had a significantly association with the disease. Among participants with a positive family history in CRC, the haplotype GD dramatically increased the risk of developing CRC (OR = 10.2, 95%CI: 2.28-46, P = 0.002). The results of this study indicate that G-1394T and I/D polymorphisms of XRCC4 among individuals with positive family history for colorectal cancer substantially increase the risk factor for developing colorectal cancers.

Association between polymorphisms at promoters of XRCC5 and XRCC6 genes and risk of breast cancer.

Variation in DNA repair genes is one of the mechanisms that may lead to variation in DNA repair capacity. Ku, a heterodimeric DNA-binding complex, is directly involved in repair of DNA double-strand breaks. Ku consists of two subunits, Ku70 and Ku80, which are encoded by the XRCC6 and XRCC5 genes, respectively. In the present study, we investigated whether common genetic variant in variable number of tandem repeats (VNTR) XRCC5 and T-991C XRCC6 was associated with an altered risk of breast cancer. The present study included 407 females with breast cancer and 395 age frequency-matched controls which were randomly selected from the healthy female blood donors. The XRCC5 and XRCC6 polymorphisms were determined using PCR-based methods. For XRCC5 polymorphism, in comparison with the 1R/1R genotype, the 0R/0R genotype increased breast cancer risk (OR 9.55, 95%CI 1.19-76.64, P = 0.034). The 1R/3R genotype compared with 1R/1R genotype decreased the risk of breast cancer (Fisher's exact test P = 0.015). There was no association between T-991C polymorphism of XRCC6 and breast cancer risk. Mean of age at diagnosis of breast cancer for 0, 1, 2, 3, and >4 repeat in XRCC5 were 39.2, 41.9, 44.3, 45.8, and 47.3 years, respectively. The Kaplan-Meier survival analysis revealed that the number of repeat was associated with age at diagnosis of breast cancer (log rank statistic = 13.90, df = 4, P = 0.008). The findings of the present study revealed that either breast cancer risk or age at diagnosis of breast cancer was associated with the VNTR polymorphism at promoter region of XRCC5.

Genetic variation in DNA repair gene XRCC7 (G6721T) and susceptibility to breast cancer.

The human XRCC7 is a DNA double-strand break (DSBs) repair gene, involved in non-homologous end joining (NHEJ). It is speculated that DNA DSBs repair have an important role during development of breast cancer. The human XRCC7 is a NHEJ DSBs repair gene. Genetic variation G6721T of XRCC7 (rs7003908) is located in the intron 8 of the gene. This polymorphism may regulate splicing and cause mRNA instability. In the present study, we specifically investigated whether common G6721T genetic variant of XRCC7 was associated with an altered risk of breast cancer. The present study included 362 females with breast cancer. Age frequency-matched controls (362 persons) were randomly selected from the healthy female blood donors, according to the age distribution of the cases. Using RFLP-PCR based method, the polymorphism of XRCC7 was determined. The TG (OR=1.20, 95% CI: 0.83-1.74, P=0.320) and TT (OR=1.01, 95% CI: 0.67-1.53, P=0.933) genotypes had no significant effect on risk of breast cancer, in comparison with the GG genotype. Our present findings indicate that the TT and TG genotypes were not associated with an altered breast cancer risk.

Clinical response to chemotherapy in locally advanced breast cancer was not associated with several polymorphisms in detoxification enzymes and DNA repair genes.

The main aim of the present study was to investigate the association between several genetic polymorphisms (in glutathione S-transferase members and DNA repair genes) and clinical response to chemotherapy in locally advanced breast cancer. A sequential series of 101 patients were prospectively included in this study. Clinical assessment of treatment was accomplished by comparing initial tumor size with preoperative tumor size using revised RECIST guideline (version 1.1). Clinical response was regarded as a response or no response. There was no difference between non-responders and responders for the prevalence of genotypes of the study polymorphisms.

Susceptibility to breast cancer and three polymorphisms of GSTZ1.

Glutathione S-transferases class zeta (GSTζ) is involved in the detoxification of xenobiotic compounds and catalyzes the biotransformation of a variety of α-haloacids including dichloroacetic acid and chlorofluoroacetic acid. It has been reported that, in mice, deficiency of Gstz1 (a member of GSTζ) resulted in the generation of a constant level of oxidative stress. The present study was carried out to investigate the association between genetic polymorphisms of GSTZ1 (in promoter site G-1002A and in coding sites Glu32Lys and Gly42Arg) and risk of breast cancer. We included 106 females with breast cancer and 106 healthy females frequency matched for age. The study polymorphisms were not associated with risk of breast cancer (p>0.05). The polymorphisms of GSTZ1 showed strong linkage disequilibrium among cancer patients and control subjects (p<0.0001). There was no significant difference between cancer patients and controls for frequencies of the GSTZ1 haplotypes (p>0.05). It seems there is no meaningful relationship between the genetic polymorphisms of GSTZ1 and risk of breast cancer.

Parental consanguineous marriages and clinical response to chemotherapy in locally advanced breast cancer patients.

The main aim of the present study was investigating the association between parental consanguinity and clinical response to chemotherapy in females affected with locally advanced breast cancer. A consecutive series of 92 patients were prospectively included in this study. Clinical assessment of treatment was accomplished by comparing initial tumor size with preoperative tumor size using revised RECIST guideline (version 1.1). Clinical response defined as complete response, partial response and no response. The Kaplan-Meier survival analysis were used to evaluate the association of parental marriages (first cousin vs unrelated marriages) and clinical response to chemotherapy (complete and partial response vs no response). Number of courses of chemotherapy was considered as time, in the analysis. Kaplan-Meier analysis revealed that offspring of unrelated marriages had poorer response to chemotherapy (log rank statistic=5.10, df=1, P=0.023).

Association between N142D genetic polymorphism of GSTO2 and susceptibility to colorectal cancer.

Expression pattern analysis has been revealed that glutathione S-transferase omega 2 (GSTO2, a member of class omega) is ubiquitously expressed. Over expression of GSTO2 induced apoptosis. The gene encoding GSTO2 was localized to human chromosome 10q24.3, a region that may harbor gene(s) involved in the developing of colorectal cancer. To investigate the association between GSTO2 N142D genetic polymorphism and susceptibility to colorectal cancer the present study was done. We studied 63 (26 females, 37 males) colorectal cancer patients and 126 (52 females, 74 males) healthy individuals. The control subjects were frequency matched for age and gender with the colorectal cancer group. The genotypes were performed using RFLP-PCR method. The ND and DD genotypes were not associated with risk of colorectal cancer, in comparison with the NN genotype. Family history for cancer in the first degree of relatives significantly differed between cases and controls (P = 0.012). The profiles of GSTO2 genotypes and family history in control and cancerous groups were compared to each other. Subjects with NN genotype and positive family history significantly were at high risk to develop colorectal cancer in comparison with subjects with DD or ND genotypes and negative family history (P = 0.003). Present findings indicating that GSTO2 NN genotype increase the risk of colorectal cancer in persons with positive family history for cancer in the first degree relatives.

Genetic polymorphisms of GSTO2, GSTM1, and GSTT1 and risk of gastric cancer.

OBJECTIVE: The glutathione S-transferases (GSTs) are a superfamily of proteins that participates in detoxification. The GSTs were dividing into several classes including omega (GSTO), micro (GSTM) and theta (GSTT) classes. In human GSTO2, GSTM1, and GSTT1 are polymorphic. In order to study whether GSTO2, GSTM1, and GSTT1 polymorphisms are associated with increased gastric cancer risk in Iranian patients, the present case-control study was done. METHODS: Genomic DNA was extracted from peripheral blood of 67 gastric cancer patients and 134 control subjects. The genotyping was performed using PCR-based method. The possible association of gastric cancer with the GSTO2 N142D polymorphism was estimated with assuming additive, dominant, and recessive effect of the variant 142D allele. To investigate whether profiles of GST genotypes are associated with the risk of gastric cancer, we used unconditional logistic regression analysis. RESULTS: The GSTO2 142D allele in additive, dominant and recessive models was not associated with the risk. Because GSTM1, GSTT1, and GSTO2 genes belong to low-penetrance genes which might be involved in the carcinogenesis, patients and controls without family of cancer in first-degree relatives were also analyzes separately. To investigate whether profiles of GST genotypes are associated with the risk of gastric cancer, we used unconditional logistic regression analysis with GSTM1, GSTT1, and GSTO2 genotypes as predictor factors. The GSTO2 DD genotype was associated with decreased risk as compared to GSTO2 NN genotype (OR = 0.21, 95% CI: 0.05-0.92, P = 0.038). CONCLUSIONS: Present findings show that GSTO2 DD genotype decreases the risk of gastric cancer in individuals without history of cancer in their first-degree relatives.

Genetic polymorphisms of XRCC1 (codon 399) and susceptibility to breast cancer in Iranian women, a case-control study.

The X-ray repair cross-complementation group 1 (XRCC1) protein plays an important role in base excision repair. In the present study, we specifically investigated whether common genetic variant in XRCC1 (exon 10, codon Arg399Gln) was associated with an altered risk of breast cancer. The eligible cases were patients at chemotherapy unit of Nemazi hospital, Shiraz Iran, from October 1999 to August 2000 and from July 2004 to July 2005. The present study included 186 females with breast cancer. Age frequency-matched controls were randomly selected from the healthy females blood donor, according to the age distribution of the cases. A total of 187 healthy females included in the study. Using PCR-based method, the XRCC1 Arg399Gln polymorphism was determined. In control group the 399Gln allele frequency was 32.6%. The genotypic frequencies of the control subjects did not show significant deviation from Hardy-Weinberg equilibrium (chi(2) = 1.683, df = 1, P > 0.05). A statistically significant association was observed in comparison between Gln/Gln and Arg/Arg genotype (OR = 2.01, 95% CI:1.02-3.94, P = 0.041). There was no linear trend for presence of 0, 1, and 2 of the 399Gln allele and risk of breast cancer (chi(2) = 1.212, P = 0.271). In the recessive effect of the Gln allele (comparison between Gln/Gln vs. Arg/Arg+Arg/Gln), Gln/Gln genotype significantly increased the risk of breast cancer (OR = 2.31, 95% CI:1.21-4.35, P = 0.010). In the dominant effect of the Gln allele (comparison between Gln/Gln+Arg/Gln vs. Arg/Arg), Gln/Gln+Arg/Gln genotypes was not associated with the risk of breast cancer (OR = 0.95, 95% CI:0.63-1.42, P = 0.799). It is concluded that 399Gln allele may act as a recessive allele and increase the breast cancer risk.