Nur Buyru

Vitamin D receptor gene polymorphisms in breast cancer

Breast cancer is the leading cause of cancer death among women around the world and its incidence is annually increasing. The vitamin D receptor (VDR) gene is a member of the nuclear receptor superfamily, which is expressed in breast tissue and known to modulate the rate of cell proliferation. Association between the VDR gene polymorphisms and cancer development has been suggested by several studies. However, the relationship between VDR polymorphisms and breast cancer is controversial and has not been confirmed by all studies. The purpose of this study was to investigate the genotype frequencies and association of the VDR Bsm I and Taq I polymorphisms with breast cancer in Turkish patients. In this study, 78 patients with breast cancer and 27 healthy individuals were enrolled. The prevalence of the VDR Taq I and Bsm I alleles and the genotype frequencies in patients with breast cancer was similar to that in the normal population. Our data indicate that no significant differences exist between the patients and control subjects.

Methylation of tumor suppressor genes in ovarian cancer

Aberrant methylation of gene promoter regions is one of the mechanisms for inactivation of tumor suppressor genes in human malignancies. In this study, the methylation pattern of 24 tumor suppressor genes was analyzed in 75 samples of ovarian cancer using the methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) assay. Of the 24 tumor suppressor genes examined, aberrant methylation was observed in 17. The three most frequently methylated genes were CDKN2B, CDH13 and RASSF1, followed by ESR1 and MLH1. Methylation frequencies ranged from 1.3% for CDKN2A, RARβ, CASP8, VHL and TP73 to 24% for CDKN2B. The corresponding normal DNA from each patient was also investigated. Methylation was detected in tumors, although not in normal tissues, with the exception of two samples, indicating aberrant methylation in tumors. Clear cell carcinoma samples exhibited a higher frequency of CDKN2B promoter hypermethylation compared to those of other histological types (P=0.05). Our data indicate that methylation of the CDKN2B gene is a frequent event in ovarian carcinogenesis and that analysis of only three genes is sufficient to detect the presence of methylation in 35% of ovarian cancer cases. However, more studies using a much larger sample size are needed to define the potential role of DNA methylation as a marker for ovarian cancer.

Coexistence of K-ras mutations and HPV infection in colon cancer

BackgroundActivation of the ras genes or association with human papillomavirus infection have been extensively studied in colorectal cancer. However, the correlation between K-ras mutations and HPV in colorectal cancer has not been investigated yet. In this study we aimed to investigate the presence of K-ras mutations and their correlation with HPV infection in colon cancer.MethodsK-ras mutations were analyzed by a mutagenic PCR assay and digestion with specific restriction enzymes to distinguish the wild-type and mutant codons. HPV infection was analyzed by PCR amplification and hybridization with specific probes by Southern blotting. Stattistical analyses were performed by the chi-square and Fishers exact testsResultsHPV gene fragments were detected in 43 tumors and 17 normal tissue samples. HPV 18 was the prevalent type in the tumor tissue. A mutation at codon 12 of the K-ras gene was present in 31 patients. 56% of the HPV-positive tumors also harbored a K-ras mutation. Codon 13 mutations were not observed. These data indicate that infection with high risk HPV types and mutational activation of the K-ras gene are frequent events in colorectal carcinogenesis.ConclusionOur findings suggest that mutational activation of the K-ras gene is a common event in colon carcinogenesis and that HPV infection may represent an important factor in the development of the premalignant lesions leading to the neoplastic phenotype.

Association between APOE polymorphisms and mesial temporal lobe epilepsy with hippocampal sclerosis.

To evaluate the hypothetical link between apolipoprotein E (APOE) polymorphisms and mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE‐HS) and whether presence of APOE epsilon4 allele shortens the latent period between febrile seizures and epilepsy. A further interest is whether presence of APOE epsilon4 allele has an impact on severity of the disease. Forty‐seven patients with MTLE‐HS were compared with 62 controls. APOE polymorphisms were determined from lymphocytes by standard methods. Eight patients (17%) and 10 controls (16.1%) were demonstrated to have one APOE epsilon4 allele. There was not any statistically significant difference in APOE epsilon4 frequency between patients and controls (P > 0.05). There was not any difference statistically according to onset age of epilepsy and the presence of APOE epsilon4 allele within patient group. APOE epsilon4 polymorphisms did not influence the severity of epilepsy. APOE epsilon4 polymorphisms had no impact on outcome after surgery. Patients with bilateral memory deficits, bilateral hippocampal atrophy and with bilateral epileptiform interictal EEG transients, were independently compared with patients having unilateral features and there were not any statistically significant differences. This study has found no association between APOE epsilon4 polymorphisms and presentation of MTLE‐HS in a group of Turkish patients.

Investigation of glutathione S-transferase M1 and T1 deletions in lung cancer

Glutathione S-transferases (GSTs) M1 and T1 are known to be polymorphic in humans. Both polymorphisms are due to gene deletions which are responsible for the existence of null genotypes. Previous studies have suggested that GST genotypes may play a role in determining susceptibility to a number of unrelated cancers, including lung cancer. The GSTM1 and GSTT1 polymorphisms were determined by PCR-based analysis in 75 lung cancer patients and 55 controls. The unconditional logistic regression analysis was used to calculate ORs and 95% CI. The frequencies of GSTM1 and GSTT1 null genotypes were 37.3 and 22.7% in lung cancer patients and 27.3 and 16.4% in controls, respectively. When analyzed by histology the GSTM1 null genotype was more prevalent in squamous-cell carcinoma and adenocarcinoma patients. Whereas, GSTT1 null genotype frequency was lower in small-cell lung cancer patients than controls. But these differences were not statistically significant. According to smoking status, null genotype for both gene are associated with an increase in risk for lung cancer. Our results suggest that GSTM1 and GSTT1 polymorphisms may play a role in the development of lung cancer for some histological subtypes and modifies the risk of smoking-related lung cancer.

WWOX gene may contribute to progression of non-small-cell lung cancer (NSCLC)

Lung cancer is the most common cause of cancer-related death worldwide and, like many other cancers, is affected by different genetic, epigenetic, and environmental factors. The WW domain-containing oxidoreductase (WWOX) gene is a tumor-suppressor gene located on chromosome 16q23.3–24.1, and it has been shown that it loses its function due to alterations in genetic and epigenetic mechanisms. The aim of this study is to investigate the relationship between lung cancer and WWOX gene. Tumor tissue samples, corresponding normal tissues, and blood samples obtained from 50 lung cancer patients were involved in the study. We analyzed methylation profile by methylation-specific PCR and mutations and polymorphisms by DNA sequencing. Methylation analysis showed that promoter hypermethylation was present in 38 of 50 (76%) patients. In addition, promoter region of WWOX gene of younger patients was more frequently methylated than older patients. Using DNA sequencing, we found four genetic alterations in WWOX gene. Two of them were germline mutations (Exon 4 and 7), and two of them were polymorphic (Exon 6 and 8). We found a new mutation in exon 7 (Arg-254→Cys) which has not been described previously. The changes in the short-chain dehydrogenase domain of the protein caused by the genetic alterations may affect the function of the gene. We conclude that hypermethylation of WWOX gene promoter region and mutations in the gene might be related to lung carcinogenesis.

Methylation Profiles in Breast Cancer

In this study, we sought to assess the aberrant methylation of multiple tumor-suppressor genes in a single reaction by using methylation-specific multiplex ligation-dependent probe amplification. Breast tumors and corresponding normal tissues of 77 patients were analyzed. In this study, 17 of 24 genes displayed promoter methylation in one or more of the tumor samples. The most frequently methylated genes were RASSF1 and GSTP1, followed by DAPK1 and CDKN2B. Our data indicate that the methylation of specific genes is a frequent event in breast cancer and show that MS-MLPA is a powerful tool to analyze epigenetic alterations for diagnostic, as well as therapeutic, purposes.

Lack of association between IL-1β/α gene polymorphisms and temporal lobe epilepsy with hippocampal sclerosis

Summary Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is one of the most common medically intractable epilepsy syndromes and the pathogenesis of HS remains highly obscure. Recent studies demonstrated controversial results about the relationship between interleukin (IL) gene polymorphism and epilepsy in different ethnic groups. This correlation was investigated in Turkish patients with MTLE-HS. The allele distribution of IL-1α and IL-1β in 47 patients of Turkish ancestry was determined and compared with 99 ethnically matched control subjects. Analysis of genotype frequencies between patients and controls showed no statistically significant difference ( p >0.05). Our data suggest that IL-1α and IL-1β gene polymorphisms do not act as a strong susceptibility factor for MTLE-HS in individuals of Turkish ancestry.

Genetic alterations of the WWOX gene in breast cancer

FRA3B and FRA16D are the most sensitive common chromosomal fragile site loci in the human genome and two tumor suppressor genes FHIT (Fragile Histidine Triad) and WWOX (WW domain-containing oxidoreductase gene) map to this sites. The WWOX gene is composed of 9 exons and encodes a 46-kD protein that contains 414 amino acids. Loss of heterozygosity, homozygous deletions, and chromosomal translocations affecting WWOX has been reported in several types of cancer, including ovarian, esophageal, lung and stomach carcinoma, and multiple myeloma. The aim of this study was to determine the role of WWOX as a tumor suppressor gene in patients with breast cancer. Tumor and adjacent non-cancerous tissue samples were obtained from 81 patients with breast cancer. DNA was isolated from all tissue samples, and all exons and flanking intronic sequences of the WWOX gene were analyzed by PCR amplification and direct sequencing. We detected 14 different alterations in the coding sequence and one base substitution at the intron 6 splice site (+1 G-A). In addition to exonic and splice-site alterations, we detected 23 different alterations in the non-coding region of the gene. All coding region mutations identified in this study were in the exons between 4 and 9. We did not observe any alterations in exons 1–3. We conclude that mutations in critical region of the WWOX gene are frequent and may have an important role in breast carcinogenesis.

Factor V Leiden, Prothrombin G20210A, and Protein C Mutation Frequency in Turkish Venous Thrombosis Patients

Several inherited polymorphisms are associated with risk of venous thrombosis, including mutation at codon 506 of the factor V gene, mutation at position 20210 of the prothrombin gene, and mutations in the protein C gene. In this study, genotyping for factor V, prothrombin, and protein C mutations was performed in 50 patients and 25 control subjects by polymerase chain reaction—based analysis. The prevalence of factor V and prothrombin mutations was not significantly different from that in the general population. Nine of the patients had heterozygous protein C mutation. There was a high prevalence of the mutated protein C allele in the pulmonary emboli group (42.8%). Protein C mutation incidence was higher in the pulmonary emboli group than in the deep vein thrombosis (8.33%) and cerebral vein thrombosis (16.1%) groups. These results indicate that patients with protein C deficiency have a greater risk of thrombosis than patients with factor V or prothrombin G20210A mutation.