Nejat Dalay

Long non-coding RNAs with low expression levels in cells are enriched in secreted exosomes.

Long non‐coding RNAs (lncRNAs) are involved in regulating chromatin modifications, gene transcription, mRNA translation, and protein function. We recently reported a high variation in the basal expression levels of a panel of lncRNAs in HeLa and MCF‐7 cells and their differential response to DNA damage induction. Here, we hypothesized that lncRNA molecules with different cellular expression may have a differential abundance in secreted exosomes, and their exosome levels would reflect cellular response to DNA damage. MALAT1, HOTAIR, lincRNA‐p21, GAS5, TUG1, CCND1‐ncRNA in exosomes secreted from cultured cells were characterized. A different expression pattern of lncRNAs in exosomes was seen compared to cells. RNA molecules with relative low expression levels (lincRNA‐p21, HOTAIR, ncRNA‐CCND1) were highly enriched in exosomes. TUG1 and GAS5 levels were moderately elevated in exosomes, whereas MALAT1—which was the most abundant molecule in cells—was present at levels comparable to its cellular levels. lincRNA‐p21 and ncRNA‐CCND1 were the main molecules; exosome levels of them best reflect the change of their cellular levels upon exposure of the cells to bleomycin‐induced DNA damage. In conclusion, we provide evidence that lncRNAs have a differential abundance in exosomes, indicating a selective loading.

Investigation of circulating lncRNAs in B-cell neoplasms.

Long non-coding RNAs (lncRNA) which are longer than 200 base pairs in length, play an important role in cellular machinery. Chronic lymphocytic leukemia (CLL) and multiple myeloma (MM) are neoplasms of B-cells. In our study we aimed to investigate circulating lncRNA levels of CLL and MM patients. For this purpose we selected 5 candidate lncRNAs (TUG1, LincRNA-p21, MALAT1, HOTAIR, and GAS5) where the first two are regulated by p53. Analyses were performed by real-time PCR using cDNA synthesized from plasma RNAs. In both disease groups differential levels of plasma lncRNAs were observed. LincRNA-p21 was the only molecule displaying significant changes in the CLL group while all remaining lncRNAs showed significant differences in the MM group. In the MM group only TUG1 showed higher levels than the healthy volunteers. In conclusion, the expression levels of the candidate lncRNA molecules display a general trend for tissue- and disease-specific expression which can provide important potential biomarkers specific to the particular disease type. However, further studies are necessary to elucidate their involvement in disease development and progression.

Promoter DNA methylation of Oncostatin M receptor-β as a novel diagnostic and therapeutic marker in colon cancer

In addition to genetic changes, the occurrence of epigenetic alterations is associated with accumulation of both genetic and epigenetic events that promote the development and progression of human cancer. Previously, we reported a set of candidate genes that comprise part of the emerging “cancer methylome”. In the present study, we first tested 23 candidate genes for promoter methylation in a small number of primary colon tumor tissues and controls. Based on these results, we then examined the methylation frequency of Oncostatin M receptor-β (OSMR) in a larger number of tissue and stool DNA samples collected from colon cancer patients and controls. We found that OSMR was frequently methylated in primary colon cancer tissues (80%, 80/100), but not in normal tissues (4%, 4/100). Methylation of OSMR was also detected in stool DNA from colorectal cancer patients (38%, 26/69) (cut-off in TaqMan-MSP, 4). Detection of other methylated markers in stool DNA improved sensitivity with little effect on specificity. Promoter methylation mediated silencing of OSMR in cell lines, and CRC cells with low OSMR expression were resistant to growth inhibition by Oncostatin M. Our data provide a biologic rationale for silencing of OSMR in colon cancer progression and highlight a new therapeutic target in this disease. Moreover, detection and quantification of OSMR promoter methylation in fecal DNA is a highly specific diagnostic biomarker for CRC.

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.

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 Arg399Gln, 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 399Gln allele (39.7 and 37.4%). Our results do not support evidence for a role of the XRCC1 polymorphism in developing breast cancer.

Exosomal lncRNA-p21 levels may help to distinguish prostate cancer from benign disease

Exosomes are membranous vesicles containing various biomolecules including lncRNAs which are involved in cellular communication and are secreted from many cells including cancer cells. In our study, investigated the exosomal GAS5 and lincRNA-p21 lncRNA levels in urine samples from 30 patients with prostate cancer (PCa) and 49 patients with benign prostatic hyperplasia. Quantification of lncRNA molecules was performed by real-time PCR. We observed a significant difference in the exosomal lincRNA-p21 levels between PCa and BPH patients whereas the GAS5 levels did not reveal a difference. Our data suggest that the discriminative potential of exosomal lincRNA-p21 levels may help to improve the diagnostic prediction of the malignant state for patients with PCa.

BRCA1 and BRCA2 mutations in Turkish breast/ovarian families and young breast cancer patients

To date, BRCA1 and BRCA2 mutations in breast and/or ovarian patients have not been characterized in the Turkish population. We investigated the presence of BRCA mutations in 53 individuals with a personal and family history of breast and/or ovarian cancer, and 52 individuals with a personal history of breast cancer diagnosed below age 50 without additional family history. We have identified 11 mutations (nine BRCA1 and two BRCA2) using combined techniques involving protein truncation test, direct sequencing and heteroduplex analysis. We found eight out of 53 patients (15.1%) with a family history to carry BRCA gene mutations (seven BRCA1 and one BRCA2). Of these, four were found in 43 families presenting only breast cancer histories, and four were found in families presenting ovarian cancer with or without breast cancer. We also demonstrated two BRCA1 and one BRCA2 mutations in three out of 52 (5.8%) early-onset breast cancer cases without additional family history. Three of nine BRCA1 and both BRCA2 mutations detected in this study were not reported previously. These mutations may be specific to the Turkish population. The BRCA1 5382insC mutation, specific to Ashkenazi and Russian populations, was found twice in our study group, representing a possible founder mutation in the Turkish population.

Size distribution of circulating cell-free DNA in sera of breast cancer patients in the course of adjuvant chemotherapy

Abstract Background: The integrity of circulating cell-free DNA (cf-DNA) in serum or plasma appears to be of diagnostic and prognostic value in cancer. Here, we investigated the dynamics of serum DNA levels and the size distribution of cf-DNA during adjuvant chemotherapy of patients with breast cancer (n=73). Methods: By evaluating sera taken at the beginning and the end of the adjuvant chemotherapy, variations of serum DNA levels and the size distribution were analyzed, based on quantification of shorter apoptotic and longer non-apoptotic fragments from abundant genomic ALU fragments amplified by quantitative real-time PCR. Results: The mean DNA level did not change significantly during chemotherapy. However, individual cases revealed considerable variation in the amount of serum DNA. It increased in 43.8% of the patients, whereas it decreased in the remaining majority (56.2%). By calculating a “coefficient of variation” (both decrease and increase) in the level of total DNA and non-apoptotic DNA fragments, we compared the values at the beginning and the end of the therapy. For total DNA, the range was between 1.02- and 26-fold (mean 3.76-fold), whereas for non-apoptotic fragments it ranged from 1.01- to 73-fold (mean 6.9-fold) (p=0.033). In accordance with these findings, the integrity of serum DNA was higher in patients with increasing DNA levels and vice versa. Conclusions: Our findings suggest that non-apoptotic fragments contribute to a higher degree to the change of the DNA level during adjuvant chemotherapy. Clin Chem Lab Med 2008;46:311–7.

Role of DNA methylation in head and neck cancer

Head and neck cancer (HNC) is a heterogenous and complex entity including diverse anatomical sites and a variety of tumor types displaying unique characteristics and different etilogies. Both environmental and genetic factors play a role in the development of the disease, but the underlying mechanism is still far from clear. Previous studies suggest that alterations in the genes acting in cellular signal pathways may contribute to head and neck carcinogenesis. In cancer, DNA methylation patterns display specific aberrations even in the early and precancerous stages and may confer susceptibility to further genetic or epigenetic changes. Silencing of the genes by hypermethylation or induction of oncogenes by promoter hypomethylation are frequent mechanisms in different types of cancer and achieve increasing diagnostic and therapeutic importance since the changes are reversible. Therefore, methylation analysis may provide promising clinical applications, including the development of new biomarkers and prediction of the therapeutic response or prognosis. In this review, we aimed to analyze the available information indicating a role for the epigenetic changes in HNC.

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.