Gulsah Cecener

Olea europaea leaf extract alters microRNA expression in human glioblastoma cells.

PurposeGlioblastoma multiforme (GBM) is the most common and the most lethal form of primary malignant tumors in the central nervous system. There is an increasing need for the development of more efficient therapeutic approaches for the treatment of these patients. One of the most attractive cancer therapy methods to date is the induction of tumor cell death by certain phytochemicals. Interestingly, bioactive compounds have been shown to alter micro RNA (miRNA) expression involved in several biological processes at the posttranscriptional level. The present study aimed to evaluate whether Olea europaea leaf extract (OLE) has an anticancer effect and modulates miRNA expression in GBM.Materials and methodsFirstly, the anti-proliferative activity of OLE and the nature of the interaction with temozolomide (TMZ) of OLE were tested in human glioblastoma cell line T98G cells by trypan blue and WST-1 assays and than realized miRNA PCR array analysis. Potential mRNA targets were analyzed bioinformatically.ResultsOLE exhibited anti-proliferative effects on T98G cell lines. Cells were treated with temozolomide (TMZ) in the presence OLE, and changes to miRNA expression levels were identified by PCR array analysis. miRNA target genes are involved in cell cycle and apoptotic pathways. Specifically, miR-181b, miR-153, miR-145, miR-137, and let-7d were significantly upregulated after treatment with both TMZ and OLE.ConclusionOur results suggest that OLE modulates the expression of some miRNAs related to anticancer activity in GBM and the response to TMZ. Further studies and validations are needed, but we suggest that OLE might be used for in vivo studies and future medical drug studies.

The relationship between genetic susceptibility to head and neck cancer with the expression of common fragile sites

Numerous studies have recently been conducted to investigate genetic mechanisms in cancer causes and pathogenesis. Some of these studies have shown that there were certain specific chromosomal defects in normal cells of cancer patients and in their first‐degree relatives. It was suggested that these individuals were susceptible to cancer development when compared with people without these defects.

The Promoter Hypermethylation Status of GATA6, MGMT, and FHIT in Glioblastoma

Glioblastoma (GBM) is an aggressive and lethal cancer, accounting for the majority of primary brain tumors in adults. GBMs are characterized by large and small alterations in genes that control cell growth, apoptosis, angiogenesis, and invasion. Epigenetic alterations also affect the expression of cancer genes, either alone or in combination with genetic mechanisms. The current evidence suggests that hypermethylation of promoter CpG islands is a common epigenetic event in a variety of human cancers. A subset of GBMs is also characterized by a locus-specific and genome-wide decrease in DNA methylation. Epigenetic alterations are important in the molecular pathology of GBM. However, there are very limited data about these epigenetic alterations in GBM. Alterations in promoter methylations are important to understand because histone deacetylases are targets for drugs that are in clinical trial for GBMs. The aim of the current study was to investigate whether the promoter hypermethylation of putative tumor suppressor genes was involved in GBM. We examined the methylation status at the promoter regions of GATA6, MGMT, and FHIT using the methylation-specific polymerase chain reaction in 61 primary GBMs. Our results reveal that there is no promoter hypermethylation of FHIT in the examined GBM tissue specimens. In contrast, the promoter hypermethylation of GATA6 and MGMT was detected in 42.8 and 11.11% of GBMs, respectively. The frequency of MGMT promoter hypermethylation was low in the group of patients we evaluated. In conclusion, our study demonstrates that promoter hypermethylation of MGMT is a common event in GBMs, whereas GATA6 is epigenetically affected in GBMs. Furthermore, inactivation of FHIT by epigenetic mechanisms in GBM may not be associated with brain tumorigenesis.

Common fragile site expression and genetic predisposition to breast cancer

The expression of common fragile sites induced by aphidicolin and caffeine was evaluated on prometaphase obtained from the peripheral blood lymphocytes of 35 women with breast cancer, their 35 clinically healthy female family members, and 20 sex- and age-matched normal controls. As a result of the cytogenetic and statistical evaluation, the number of damaged cells, chromosomal aberrations, and expression frequencies of fragile sites detected in patients with breast cancer and their first-degree relatives were found to be significantly higher than those in the control group. Our findings indicate an increased genetic instability in women with breast carcinomas and their relatives. Therefore, fragile sites may be used as a reliable marker for defining genetic susceptibility to cancer in general.

Impact of novel PTEN mutations in Turkish patients with glioblastoma multiforme

Glioblastoma multiforme (GBM) represents the most common and aggressive type of primary neoplasms of the central nervous system. The PTEN (phosphatase, tensin homologue, deleted on chromosome TEN; MIM # 601728) tumor suppressor gene has an essential biological role in the formation of glioblastomas. It is known that there are variations in genetic alterations in tumors that develop in patients with different ethnic backgrounds and because there is no study evaluating PTEN mutation in Turkish patients with GBM, we aimed to realize the present study. We investigated 62 GBM tumors for mutations of the PTEN gene using single strand conformational polymorphism (SSCP) method followed by DNA sequencing. As a result of our investigation, PTEN mutations were detected in 15 of 62 tumors (24.19%). Nine different sequence variants were identified: one novel promoter site mutation (5′UTR −9C→T), one novel intronic mutation (IVS2-2delA), four novel point mutations (61A→G, 105T→G, 248C→G, and 364C→G), two novel frameshift mutations (213delC) and 378delGATA) and one previously reported global exonic transition type mutation (129G→A). Since the majority of PTEN mutations identified in the present study are novel, we believe that these alterations may be specific to Turkish population. Furthermore, though no significant correlation was found between PTEN mutations and histopathological properties of GBM tumors, our findings indicate that localizations of mutations in PTEN gene may have an effect on clinical aggressiveness of GBM tumors.

Novel germline BRCA1 and BRCA2 mutations in Turkish women with breast and/or ovarian cancer and their relatives.

BRCA1 and BRCA2 gene mutations in patients with breast and/or ovarian cancer have been not characterized in the Turkish population until now. A total of 87 female subjects from two sets of families (38 families total) provided blood samples from which DNA was extracted. All coding exons of the BRCA1 and BRCA2 genes were screened for mutations with heteroduplex analysis and sequencing. Fourteen of the families (49 subjects comprising 17 patients and 32 unaffected relatives) had at least 2 women affected by breast and/or ovarian cancer. The other 24 families (38 subjects unaffected by breast and/or ovarian cancer) also had a history of these 2 forms of cancer. Six different sequence variants were detected: one previously described truncating mutation (5382insC) and one novel polymorphism (3663C→A) in BRCA1, and 2 novel truncating mutations (9329insC and 9934insG), one novel intronic polymorphism 7069+41(TTTT→AAAG), and one previously reported global polymorphism (1093A→C) in BRCA2. BRCAPRO software was used for analysis, and the results showed that the level of risk for both breast and ovarian cancer increased with age in women who carried the mutation. In conclusion, these findings contribute significantly to what currently is known about the types and impact of germline BRCA1 and BRCA2 mutations in Turkish women.

BRCA1/2 germline mutations and their clinical importance in Turkish breast cancer patients.

BRCA1/BRCA2 genes were screened in 117 patients with breast cancer by sequencing. Fourteen percent of patients tested positive for BRCA1/BRCA2 mutations. Four frame shift mutations, four pathogenic missense mutations, and 25 different sequence variations were detected. BRCA mutation positivity was significantly associated with Ki67 (p = .001). BRCA protein expressions were decreased in the patients harboring important mutations and polymorphisms (BRCA1;P508stop, V1740G, Q1182R, Q1756P and BRCA2;V2466A) related with disease. Our findings contribute significantly to the types of germline BRCA1/BRCA2 mutations and their biological effects in Turkish women. These data could help guide the management of BRCA1/BRCA2 mutation-carrying patients when considering breast-conserving therapy.

Analysis of mismatch repair gene mutations in Turkish HNPCC patients

Hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome) is caused by the inheritance of a mutant allele of a DNA mismatch repair gene. We aimed to investigate types and frequencies of mismatch repair (MMR) gene mutations in Turkish patients with HNPCC and to identify specific biomarkers for early diagnosis of their non-symptomatic kindred’s. The molecular characteristics of 28 Turkish colorectal cancer patients at high-risk for HNPCC were investigated by analysis of microsatellite instability (MSI), immunohistochemistry and methylation-specific PCR in order to select tumors for mutation analysis. Ten cases (35.7%) were classified as MSI (+). Lack of expression of the main MMR proteins was observed in MSI (+) tumors. Hypermethylation of the MLH1 promoter region was observed in one tumor. Nine Lynch syndrome cases showed novel germ-line alterations of the MMR gene: two frame-shifts (MLH1 c.1843dupC and MLH1 c.1743delG) and three missense mutations (MLH1 c.293G>C, MLH1 c.954_955delinsTA and MSH2 c.2210G>A). Unclassified variants were evaluated as likely to be pathogenic by using the in-silico analyses. In addition, the MSH2 c.2210G>A alteration could be considered as a founder mutation for the Turkish population due to its identification in five different Lynch syndrome families and absence in control group. The present study adds new information about MMR gene mutation types and their role in Lynch syndrome. This is the first detailed research on Turkish Lynch syndrome families.

Molecular approach to genetic and epigenetic pathogenesis of early-onset colorectal cancer

Colorectal cancer (CRC) is the third most frequent cancer type and the incidence of this disease is increasing gradually per year in individuals younger than 50 years old. The current knowledge is that early-onset CRC (EOCRC) cases are heterogeneous population that includes both hereditary and sporadic forms of the CRC. Although EOCRC cases have some distinguishing clinical and pathological features than elder age CRC, the molecular mechanism underlying the EOCRC is poorly clarified. Given the significance of CRC in the world of medicine, the present review will focus on the recent knowledge in the molecular basis of genetic and epigenetic mechanism of the hereditary forms of EOCRC, which includes Lynch syndrome, Familial CRC type X, Familial adenomatous polyposis, MutYH-associated polyposis, Juvenile polyposis syndrome, Peutz-Jeghers Syndrome and sporadic forms of EOCRC. Recent findings about molecular genetics and epigenetic basis of EOCRC gave rise to new alternative therapy protocols. Although exact diagnosis of these cases still remains complicated, the present review paves way for better predictions and contributes to more accurate diagnostic and therapeutic strategies into clinical approach.

P53 gene mutations in surgical margins and primary tumor tissues of patients with squamous cell carcinoma of the head and neck.

Aims and Background The frequency of p53 mutations in primary tumors, the effect of the mutations on some clinical and pathological features of head and neck squamous cell carcinoma, and the impact of p53 mutations in the surgical margins on local recurrence were determined. Material and Methods We investigated the presence of p53 mutations in primary tumor samples and in the surgical margins of 34 patients with head and neck cancer using single strand conformational polymorphism and sequencing analysis. Results The p53 mutations (codons 175addAT, 175delGC, 206G→A, and 248delC) were found in the primary tumor samples of 15 of 34 patients (44.12%) and in the surgical margins of 5 of the 15 tumors (33.33%) with p53 mutations. Conclusions We found no statistically significant association between the presence of p53 mutations in the primary tumor, the clinical and pathological features, or outcome of head and neck squamous cell carcinoma in this study. Furthermore, the presence of p53 mutations in the surgical margins may not increase the risk of local-regional recurrence, but probably increases the risk of developing distant metastases or second primary tumors.