Association of the XRCC1 gene polymorphisms with cancer risk in Turkish breast cancer patients

The X-ray repair cross-complementing group 1 (XRCC1) gene is believed to play an important role in base excision repair and displays genetic polymorphisms. Data on the role of XRCC1 polymorphisms in cancer susceptibility is inconsistent. In the present study, we investigated the effect of two XRCC1 polymorphisms, Arg194Trp and Arg399GIn, on breast cancer risk in a case-control study involving Turkish breast cancer patients and healthy women. Both alleles exhibited a similar distribution among cases and controls leading to lack of any significant association between the XRCC1 polymorphisms and breast cancer risk, either in homozygotes and heterozygotes or combined. The allele frequency of the codon 194 variant was very low in cases and healthy individuals (5.3 and, 3.9%, respectively) compared to that of the variant 399GIn allele (39.7 and 37.4%). Our results do not support evidence for a role of the XRCC1 polymorphism in developing breast cancer

Expression of the TRAIL receptors in blood mononuclear cells in leukemia

TRAIL receptors are differentially expressed on restricted subpopulations of normal blood cells. In the present study, we investigated the utility of individual TRAIL receptors in evaluating the presence of circulating tumor cells in blood. Patients with chronic myeloid leukemia (CML) carrying the t(9;22) translocation were compared with patients in whom no translocation was detected, with patients with multiple myeloma and with a group of healthy individuals. TRAIL receptor expression was analyzed by RT-PCR in blood mononuclear cells. Blood mononuclear cells of healthy subjects expressed the TRAIL-R1 and TRAIL-R2 death receptors and the TRAIL-R4 decoy receptor while the other decoy receptor TRAIL-R3 was not detectable. This normal expression pattern was also observed in all cases with multiple myeloma and in almost all patients without translocation (42/43; 97.7%). However, in 24/56 (42.9%) of the translocation-positive patients, the expression pattern was completely different. In this group the TRAIL-R4 receptor alone or in combination with TRAIL-R1 disappeared from blood mononuclear cells, while the TRAIL-R2 was expressed at normal level, indicating that the loss of expression is specific for the TRAIL-R4 and TRAIL-R1. This expression pattern was also confirmed by real-time PCR. The differences between the translocation-positive and -negative groups for the TRAIL-R4 and TRAIL-R1 expression were highly significant (p= 0.0001 and p= 0.0004, respectively). However, the differential expression pattern did not correlate with the number of leukemic cells. Our results suggest a correlation between the presence of leukemic cells in circulation and the differential expression pattern of TRAIL receptors in blood mononuclear cells

Homozygosity at the C677T of the MTHFR gene is associated with increased breast cancer risk in the Turkish population

Background: Folate deficiency is implicated in cancer development. Single nucleotide polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene can modulate the effect of folate. In this case-controlled study, a possible effect of the common MTHFR C677T (ala -> val) polymorphism on breast cancer susceptibility in Turkish patients was investigated. Materials and Methods: Polymorphism analysis was performed by melting curve analysis. Results: The variant allele valine (677T) was more frequent among the patients (30.1%) than in controls (23.9%). This difference was weakly significant (p=0.046; OR=1.37) and due to a significantly higher frequency of the valine homozygotes (677TT) among the patients (12.1% vs. 5.4%; p=0.013, OR=2.5). Among the patients diagnosed at more than 40 years of age, a more pronounced association of the valine homozygotes with breast cancer risk was observed (p=0.009; OR=3.3). Conclusion: Homozygosity for the low-activity C677T genotype (TT) may represent a genetic determinant increasing breast cancer risk

A novel application of melting curves: utility of peak area calculation for relative methylation quantification

Background: DNA methylation markers appear to be useful in cancer detection, in evaluating the prognosis associated with disease progression, and in detecting the metastatic potential of tumors

Testing the putative effect of Dicer-substrate siRNAs in regulating gene expression at transcriptional level

RNA interference (RNAi) pathway is a gene silencing process during which small double-stranded RNA (dsRNA) molecules trigger the degradation of homologous RNA targets. Small interfering RNAs (siRNAs) are the mediators of the RNAi that can be induced in vitro and in vivo by direct application of chemically synthesized siRNAs. Recently, promoter-targeted small non-coding RNAs have been described to be capable of regulating gene expression at the transcriptional level. In the present study we tested the hypothesis that Dicer-substrate siRNAs (D-siRNAs), which trigger gene silencing through intrinsic RNAi pathway and are therefore more potent in gene knockdown than traditionally used 21-23mer siRNAs, may also display regulatory effects at the transcriptional level. Synthetic 27mer D-siRNAs targeting the promoter/early coding region of the CDKN2A gene were designed and transfected into HeLa cells, and 48 h post-transfection the CDKN2A expression was analyzed in quantitative real-time PCR using the housekeeping G6PDH gene as reference. In comparison to the mutant version, the CDKN2A gene was effectively knocked-down by the D-siRNA, but no evidence of transcriptional regulation was found. We conclude that the D-siRNA-induced suppression is likely to occur after transcription

Frequent copresence of methylated DNA and fragmented nucleosomal DNA in plasma of lymphoma patients

Background: The circulating DNA in plasma/serum of cancer patients has been shown to reflect the characteristics of the tumor DNA including molecular changes, such as rnethylation, point mutations and microsatellite instability. Fragmented nucleosomal DNA in plasma resulting from apoptotic death of the tumor cells may also provide an indication for tumor DNA. In this study, we comparatively analysed plasma DNA methylation and presence of fragmented nucleosomal DNA in patients with lymphoproliferative diseases. Methods: Methylation in the first exon of the tumor supressor gene p16 was investigated by the methylation-sensitive restriction enzyme-related PCR. DNA fragmentation in plasma was analysed by gel electrophoresis. Results: p16 gene methylation was found to occur in 73% of patients but in none of the 20 healthy controls. Nucleosomal DNA fragmentation was detectable in 81% of patients. In 67% of patients, copresence of both parameters was observed. Presence of both parameters a frequent event and may be used as a marker for early diagnosis and during the follow-up of the disease. (C) 2003 Elsevier B.V. All rights reserved