Nuclear methylation levels in normal and cancerous thyroid cells.

Background: Most cancers show abnormal DNA methylation and a positive correlation between hypomethylation and tumour progression.

Patients And Methods: In our laboratory the extent of DNA methylation in individual nuclei in normal, cancer and non-cancer thyroid tissue samples was quantified according to a previously described method of computer-assisted semi-quantitative analysis. Cancer and non-cancer samples were obtained from nine patients with different thyroid pathologies (one multinodular goitre and eight carcinomas).

DNA demethylation is directly related to tumour progression: evidence in normal, pre-malignant and malignant cells from uterine cervix samples.

A computer-assisted assay based on the quantitative analysis of DNA methylation in individual interphase nuclei by indirect immunolabelling with anti-5-methylcytosine antibodies was recently developed in our laboratory. In situ analyses were performed on individual nuclei from normal and experimentally hypo- or hypermethylated cultured cells as well as on human peripheral blood B-lymphocytes from normal and chronic lymphoid leukemia (CLL) samples. We present the results obtained on cells from patients affected by different degrees of preneoplastic or neoplastic changes of the uterine cervix as compared to normal controls.

Evaluation of global DNA hypomethylation in human colon cancer tissues by immunohistochemistry and image analysis.

Background: Global hypomethylation of DNA is frequently observed in human tumours. This alteration is detected in early adenomas in colorectal tumorigenesis. Information is currently acquired after extraction of DNA from tissues, digestion with nucleases, and analysis by reverse phase chromatography, or treatment with restriction enzymes followed by gel electrophoresis analysis and Southern hybridisation with radiolabelled probes.