ASSESSMENT OF THE VALUE OF METHYLATION FEATURES IN DIFFERENT TISSUES FOR PREOPERATIVE IDENTIFICATION OF HIGH-RISK BREAST TUMORS.

Epigenetic changes in breast cancer patients have long been believed to be a promising marker for clinical management - early detection, prognostication, etc. Various approaches are available to test global DNA or target gene methylation status. We used some of them in different tissues of patients with breast cancer to analyze possible links between epigenetic parameters and their value for predicting clinicopathological characteristics (most importantly stage and lymph node status) of tumors. Patients with ductal and lobular invasive carcinoma were included in the study along with age-matched controls. Blood, tumor tissue and normal breast ductal epithelial cells were investigated using MS-HRM technique (for BRCA1 gene promoter methylation assessment), COBRA-PCR (for Alu element methylation quantification) and ELISA-based method (for global DNA methylation estimation). These parameters were analyzed in comparison to clinical, histologic and phenotypic characteristics of the tumors. BRCA1 promoter methylation was detected exclusively in tumor tissues and in only two cases, both of which had aggressive phenotype. Alu and global DNA methylation showed markedly low levels in all tissues of cancer patients compared to healthy controls, with extreme hypomethylation in tumor tissue. Changes in these two parameters were not always concordant. Methylation levels detected in blood showed rather weak relationship with clinicopathological characteristics of tumors. We could conclude that tested parameters are not useful for preoperative determination of tumor stage or lymph node status, neither any other clinicopathological characteristics of tumors. Epigenetics signatures of different tissues of the same patient are not homogenous. Given the uniform picture of DNA methylation in blood in some of investigated groups, additional data and very careful approach are required when considering using it as a diagnostic or predictive tool.

LINE-1 METHYLATION IN BLOOD AND TISSUES OF PATIENTS WITH BREAST CANCER.

Methylation is an epigenetic alteration proved to be involved in many disease processes including cancer. This change affects mainly gene promoters and repetitive sequences in genome. Long Interspersed Nuclear Element-1 (LINE-1) is a family of retrotransposons - repetitive elements that modify gene activity and can themselves be targeted by epigenetic mechanisms. LINE-1 methylation level is a surrogate marker for global methylation. In many conditions this parameter is found to be altered not only in affected cell groups, but also throughout other tissues. The aim of our study was to compare LINE-1 methylation pattern in DNA extracted from blood of the patients with benign and malignant breast tissue. In addition, we investigated correlation of LINE-1 methylation in blood and tissues of same patients and relationship of all variables with histopathologic and phenotypic characteristics of tumors. Patients with biopsy-proved ductal invasive carcinoma of breast and no preoperative chemo/radiotherapy were chosen for the study group. Another pool of patients with various benign breast lesions represented controls. Blood samples from both group members were collected preoperatively. Tumor tissue sections were processed for pathology report and part of remaining tissue was used for methylation study. LINE-1 methylation level was quantified using ELISA-based assay. It was analyzed in combination with histologic and phenotypic tumor parameters and compared between different tissues and different study groups. LINE-1 was found to be significantly hypomethylated in breast cancer tissue compared to blood. Blood samples of patients with malignant tumors showed slightly lower methylation level, than samples obtained from control group members. Lymphovascular invasion was the only aggressiveness-determining factor that was found to be at least weakly correlated with LINE-1 hypomethylation in blood. We can conclude, that global hypomethylation measured by LINE-1 methylation level is significant in tumor tissue. But there is no significant difference between LINE-1 methylation levels in blood of patients with benign and malignant breast tumors; therefor LINE-1 hypomethylation in blood cannot be used as a marker for early tumor detection. Neither is it valid for determination of tumor behavior.

MTHFR GENE C677T POLYMORPHISM AND LEVELS OF DNA METHYLTRASFERASES IN SUBCLINICAL HYPOTHYROIDISM.

The aim of our study was to investigate the link between MTHFR gene C677T polymorphism and DNMTs levels in patients with Subclinical Hypothyroidism (SCH). In this study 19 adult patients with subclinical hypothyroidism and 19 healthy controls (mean age 31±5.5 and 33±5.1 years respectively) were recruited. All patients were diagnosed based on serum levels of TSH, FT4, anti-TG and anti-TPO antibodies. Written informed consents were obtained from all study subjects. Genomic DNA was extracted using Quick-DNA Universal Kit (Zymo Research, USA). The MTHFR C677T polymorphism was genotyped by PCR-RFLP method. Levels of DNMT1 and 3a were measured in nuclear extracts of PBMC using DNMTs assay kits (Abcam). Our data indicates that the frequency of genotypes and alleles were different among the patient and the control group. There is a significant increase in CC genotype distribution in the control group when compared to the SCH patient group, while the CT as well as TT genotype distribution were not increased significantly in SCH group versus control group. However the C allele is significantly prevalent in the control group compared to the SCH group, while T allele is prevalent in patients compared to the control group with a statically significant difference. In addition, individuals with TT and CT genotypes and hypothyroidism showed elevated amount of DNMT3a in nuclear extracts of PBMC compared with controls, while no significant difference in DNMT1 levels was observed. This study indicates the MTHFR C677T variant may contribute in alteration of epigenetic regulation such as DNA methylation mediated by DNA methyltransferases in patients with subclinical hypothyroidism and also, carriers of the T allele might have an increasing risk of developing SCH.

A STUDY OF THE RELATIONSHIP BETWEEN LEVELS OF METHYLTRANSFERASES IN PERIPHERAL BLOOD MONONUCLEAR CELLS AND CHARACTERISTICS OF TUMOR IN PATIENTS WITH DUCTAL INVASIVE CARCINOMA OF BREAST.

The role of epigenetics in tumor development and progression is actively being studied. The aim of our current pilot study is to analyze correlation of changes in the levels of methyltransferases in nuclear extracts of blood cells with some morphological and phenotypic characteristics of breast cancer. The levels of DNMT1, DNMT3a and H3K4 methyltransferase were measured. The results showed that the level of DNMT1 was highest in the control group but correlation with the tumor grade was just moderate. DNMT3a was found in highest level in Grade III cancer group, followed by Grade II and Grade I groups. Correlation of DNMT1 level with tumor grade was moderate. An opposite pattern was seen for H3K4 methyltransferase. DNMT3a level was higher in larger tumors, while the level of H3K4 methyltransferase was lowest in large tumors with significant negative correlation with the tumor size. This primary study shows that there are some changes in methyltransferase levels in PBMC from breast cancer patients. These changes are most probably attributed to modification of initiation as well as sustainment of methylated status of products.

Epigenetic regulation of acute inflammatory pain.

Acute pain is associated with tissue damage, which results in the release of inflammatory mediators. Recent studies point to the involvement of epigenetic mechanisms (DNA methylation) in the development of pain. We have found that during acute inflammatory pain induced by the application of 10% mustard oil on the tongues of rats, levels of DNMT3a and 3b were elevated markedly (36 and 42 % respectively), whereas the level of DNMT1 was not changed significantly. Previous injection of Xefocam with 0,4 mg/kg dose decreased levels of DNMT3a and 3b (25 and 24% respectively). The level of DNMT1 was not changed significantly compared to the control group. The findings support the idea that inhibitors of DNA-methyltransferases could be useful for pain management. Our data suggest that NSAIDs (alone or in combination with DNMT inhibitors) may be proposed as possible epigenetic regulatory agents, which may play a role in epigenetic mechanisms indirectly through altering the activity of inflammatory mediators involved in pain development.

Distribution of cancer stem cells in ductal invasive carcinoma of breast (review).

Despite advances in detection and treatment of breast cancer, mortality from this disease remains high. According to contemporary point of view the reason for this lies in fact, that in addition to intertumor heterogeneity, there is also a high degree of intratumor diversity in cancer cell population. For most cancers it is less clear which cells within the tumor clone possess tumor-initiating cell function. During studying oncogenesis and maligniяation processes a pool of cancer cells with stem characteristics - cancer stem cells (CSC) was identified. Indeed, the specifications of them let us conclude, that exactly these cells comprise the leading substrate for cancer initiation and self-renewal. Breast carcinomas have been reported to contain a subpopulation of CD44(+)/CD24(-)/low cancer cells, which are capable of generating tumors even when implanted in very low numbers. Exactly these cells are considered to be CSCs in different subtypes of breast cancer and cancers with CD44(+)/CD24(-)/low phenotype are confirmed to have a poor prognosis (but some controversies remain concerning this issue). The aim of the review was to assess the current literature published on the breast cancer stem cells. There are not so many studies, revealing the diversity of cancer stem cells in different types, different sizes and different grade of breast cancers. CSC distribution in breast cancer with lymph node involvement, metastasizing and chemoresistant cases, existence of circulating tumor cells in not studied precisely. So the concept of cancer stem cells in breast cancer is still a topic for discussions. This can bring light to a better understanding of the pathological process in breast cancer and ways to target it.

Distribution of CD44/CD24 positive cells in ductal invasive carcinoma of breast of different grade and molecular subtype.

The purpose of our study was to learn the distribution characteristics of cancer stem cell markers (CD24, CD44) in invasive carcinomas with different grade and molecular subtype. For research was used 1324 postoperative breast cancer samples, from which were selected 393 patient with invasive ductal carcinoma samples examined 2008-2012 in Laboratory of "Pathgeo Union of Pathologist" is and N.Kipshidze Central University Hospital. The age range is between 23-73 year. For all cases were performed immunohistochemical study using ER, PR, Her2, Ki67, CK5- molecular markers (Leica Microsystems). For identify cancer stem cells mononuclear antibodies CD24 (BIOCARE MEDICAL, CD44 - Clone 156-3C11; CD24 - Clone SN3b) were used. Association of CD44/CD24 expression in different subtypes of cells, between clinicopathological parameters and different biological characteristics were performed by Pearson correlation and usind X2 tests. Obtained quantitative statistical analyses were performed by using SPSS V.19.0 program. Statistically significant were considered 95% of confidence interval. The data shows, that towards G1-G3, amount of CD44 positive cases increased twice. CD44 positive cases are evenly distributed between Luminal A, Luminal B, HER2+, triple negative basal like cell subtypes and in significantly less (4,8 times) in Her2+ cases. Maximum amount of CD44 negative cases is shown in Luminal A subtype, which could be possible cause of better prognosis and high sensitivity for chemotherapy. For one's part such aggressive subtypes of breast cancer as Luminal B and basal like cell type, are characterized by CD44 positive and antigen high expression, which can be reason of aggressive nature of this types and also reason of chemotherapy resistance. As well as amount of CD24 positive cases according to malignancy degree, also antigen expression features does not show any type of correlation between malignancy degree and CD24 positivity or with CD24 expression features, or presence of stem cells. That can be the reason of tumor aggressivity and chemoresistance. exceptions are Her2 positive tumors because they have different base of carcinogenesis.