Epigenetics: an alternative pathway in GISTs tumorigenesis.

Many diseases have different pathological backgrounds responsible for abnormal cell behavior and exhibiting altered function and signal transduction. This is especially true for tumors and although changes affecting DNA sequence, irreversible mutations and chromosomal aberrations in gastrointestinal stromal tumors (GISTs) have been widely studied, the importance of reversible epigenetic changes increasingly recognized in many cancers has received insufficient attention in these tumors. Epigenetic mechanisms are part of normal development and gene expression under normal conditions, but malfunction of these processes leads to malignant transformation by disturbing both intra- and intercellular communication. GISTs are a specific group of gastrointestinal tract tumors resistant to conventional chemotherapy and radiotherapy. Although they account for only 1% to 2% of tumors, they are among the most widespread gastrointestinal mesenchymal tumors. DNA hyper/hypomethylation overexpression/underexpression of miRNAs or abnormal histone modification may provide an alternative to the genetic modifications responsible for GIST pathology, response to treatment, prognosis and overall survival. This review summarizes the known epigenetic mechanisms involved in GIST pathogenesis; including onset, progression, and GISTs resistance. Reversible epigenetic changes are a novel and appropriate approach to halt the spread of metastases and the emergence of resistance in GIST treatment, and these changes depend on the type of epigenetic alternation, including inhibitors of histone acetyltranferase and deacetylase and DNA methyltransferases.

Gastrointestinal stromal tumor after tyrosine kinase inhibition therapy: a review of biopsies of 34 patients with clinically suspected relapse and/or progression of the tumor.

Implementation of combined surgical and targeted therapy strategies using tyrosine kinase inhibitors improved the prognosis of patients with aggressive GISTs. The therapeutic answer may be individually different, some patients do not respond properly, or even progress in spite of the therapy. This together with intratumoral heterogeneity and possible development of secondary phenotypical and genetical changes represents a challenge for pathologists examining a biopsy of relapsed tumors and/or their metastases. For this study biopsy files of the national Slovak GIST registry were reviewed to identify patients examined bioptically both prior the therapy and during the TKI treatment due to suspected tumor relapse and/or progression. All the GIST biopsies were analyzed using a standardized algorithm of histological, immunohistochemical and molecular analyses of exon 7, 9, 11, 13 of c-KIT and exons 12, 14, and 18 of PDGFRA genes, with the aim to identify posttherapeutical changes of these parameters. From 34 patients fulfilling the criteria of selection, all were histologically examined during their clinically suspicious first GIST relaps, eight during the 2nd, three during 3rd and one during 4th and 5th relapse resp. All but one posttherapeutical biopsies showed "viable" GIST tissue and so 44 relapses of 33 patients could be evaluated in comparison with identical parameters of diagnostic biopsies. Distinguishing three major histological types (spindle-, epitheloid-cell and mixed cell type), a change of the GIST type was identified in 1/3 of 1st relapse and » of all relapse biopsies. Evaluation of three phenotypical GIST parameters CD117, CD34 and DOG-1, showed that phenotype alteration was always represented by a single change. The most common was either a gain or loss of CD34 positivity appearing in 1/3 of 1st relapse biopsies, while a loss of CD117 positivity was identified in one patient´s biopsy only. Altogether, the phenotypical changes were in » of all relapses. A changed mutational profile was recognized in 38,2% first relaps biopsies and in 33% of all relapses, the change was mostly isolated (in 10/45 relapses) and less often (in 4/45 relapses) it represented a gain of a new mutation in association with persisting original one. In conclusion, the biopsies of patients showing relapse and/or progression on TKI treatment show predominance of viable GIST cells with limited or even absent signs of scaring, as well as relatively low incidence of morphological, pheno- and genotypical changes.

[Methylation of selected tumor-supressor genes in benign and malignant ovarian tumors]. / Metylácia vybraných tumor-supresorických génov v benígnych a malígnych ovariálnych nádoroch.

OBJECTIVE: To evaluate the usefullness of examination of methylation status of selected tumor-supressor genes in early diagnosis of ovarian cancer. DESIGN: Prospective clinical study. SETTING: Department of Gynecology and Obstetrics, Department of Molecular Biology, Jessenius Medical Faculty, Commenius University, Martin, Slovak Republic. METHODS: In this study we analyzed hypermethylation of 5 genes RASSF1A, GSTP, E-cadherin, p16 and APC in ovarian tumor samples from 34 patients - 13 patients with epithelial ovarian cancer, 2 patients with border-line ovarian tumors, 12 patients with benign lesions of ovaries and 7 patients with healthy ovarian tissue. The methylation status of promoter region of tumor-supressor genes was determined by Methylation Specific Polymerase Chain Reaction (MSP) using a nested two-step approach with bisulfite modified DNA template and specific primers. RESULTS: Gene methylation analysis revealed hypermethylation of gene RASSF1A (46%) and GSTP (8%) only in malignant ovarian tissue samples. Ecad, p16 and APC genes were methylated both in maignant and benign tissue samples. Methylation positivity in observed genes was present independently to all clinical stages of ovarian cancer and to tumor grades. However, there was observed a trend of increased number and selective involvement of methylated genes with increasing disease stages. Furthermore, there was no association between positive methylation status and histological subtypes of ovarian carcinomas. CONCLUSION: RASSF1A and GSTP promoter methylation positivity is associated with ovarian cancer. The revealed gene-selective methylation positivity and the increased number of methylated genes with advancing disease stages could be considered as a useful molecular marker for early detection of ovarian cancer. However, there is need to find diagnostic approach of specifically and frequently methylated genes to determining a methylation phenotype for early detection of ovarian malignancies.

Association of p53 polymorphisms with breast cancer: a case-control study in Slovak population.

Protein p53 is the tumor suppressor involved in cell cycle control and apoptosis. As a transcription factor p53 controls many cell processes and helps in prevention of cancer development. The p53 gene is polymorphic. Polymorphisms can affect the important regions involved in protein tumor suppressor activity. The well-known polymorphisms are the polymorphisms BstUI in exon 4 and MspI in intron 6. Both are supposed to be associated with cancer development. The purpose of this study was to investigate the genotype frequencies and associations of these polymorphisms with breast cancer in Slovak population. We observed the prevalence of BstUIPro (27.47%) and MspIA1 (17.58%) alleles and BstUIPro/Pro (8.79%) and MspIA1/A1 (5.49%) genotypes in breast cancer patients in comparison with controls 23.40%, 14.10%, 5.77%, 1.92% respectively. However the differences were not significant. After division of the cases and controls according to the age the prevalence of the risk alleles and genotypes in women at the age 50 years or less was higher as compared to women older than 50 years. In the younger women group, the p53 BstUI polymorphism genotype frequencies were 6.2% for BstUIPro/Pro, 31.0% for BstUIArg/Pro and 62.8% for BstUIArg/Arg in controls and 11.11 %, 40.74% and 48.15% in cases respectively. The risk of disease for BstUIPro/Pro genotype was more than two-fold higher in comparison with the BstUIArg/Arg (OR=2.34, 95% CI=0.53-10.24). In p53 MspI the genotype frequencies were 1.77% for MspIA1/A1, 24.78% for MspIA1/A2 and 73.45% for MspIA2/A2 in controls and 11.11%, 18.52% and 70.37% in cases respectively. The risk of disease for MspIA1/A1 genotype was more than six-fold higher in comparison with the MspIA2/A2 (OR=6.55, 95% CI=1.02-41.98). When we evaluated the association of both polymorphisms together with the breast cancer risk we observed that the highest risk was connected with the genotype BstUIPro/Pro / MspIA1/A1 (OR=2.99, 95% CI=0.69-13.06). Our results indicate that both BstUI and MspI p53 polymormphisms might play the role in the breast cancer development especially in women younger than 50 years.