CHANGES IN METHYLATION IN TUMOR-CELLS - A NEW IN-SITU QUANTITATIVE APPROACH ON INTERPHASE NUCLEI AND CHROMOSOMES

DNA methylation is known to be related to the regulation of gene expre ssion. DNA methylation patterns are modified in tumors compared to nor mal tissue, and in some cases; these variations are linked to cancer p rogression. Molecular biology techniques are generally used to evaluat e DNA methylation status. We describe here a simple and fast immunoflu orescent method ro quantitate in situ DNA methylation using an image a nalyser and a CCD camera. Quantification of relative methylation level s in interphase nuclei and metaphase chromosomes was performed on digi tal images of two types of cells with known methylation levels. The re sults from image cytometry corresponded to those obtained by molecular studies. Advantages of this approach are that all the DNA of a cell m ay be examined rather than a limited restriction sequence, and that it may be done on a cell by cell basis rather than on a heterogenous pop ulation. In addition, with this method, changes in methylation pattern s during tumor progression could be followed and eventually used as a marker for prognosis.