NONRANDOM DISTRIBUTION OF MUTAGEN-INDUCED CHROMOSOME BREAKS IN LYMPHOCYTES OF PATIENTS WITH DIFFERENT MALIGNANCIES

Data regarding specific chromosomal alterations in most solid neoplasm s are scarce because the complex changes observed in tumor biopsies ar e often a challenge to interpret. The present investigation using chro mosomal banding, was designed to analyze exact regions of spontaneous and mutagen-induced lymphocytic chromosomal breaks and investigate if they are unique for different cancers. Tissue from three groups of ind ividuals were included in the study, viz., normal individuals, untreat ed head and neck cancer patients, and untreated melanoma patients. For every individual three samples were analyzed for spontaneous, bleomyc in (radiomimetic)-induced and 4-nitroquinoline-N-oxide(4NQO) (ultravio let rays mimetic)-induced chromosome damage. The results revealed that in melanoma patients, chromosomes 1, 6, and 9 showed a significantly higher number of breaks than other chromosomes. A clustering of breaks was observed at loci 1p32, 1q32, 6p21, 6q21 and 9q11. Among the head and neck cancer patients, a significantly larger number of breaks was found in chromosomes 3 and 7 with clustering of breaks mainly in regio ns 3p21, 3q21, 7q22 and 7q32. Thus, it was found that regardless of th e mutagen used, specific chromosomes are more susceptible to breakage than others. Our results indicate that chromosomal fragility is specif ic for particular cancers and that challenging the cells with mutagens reveals it at a more pronounced rate. Mutagen-induced chromosome brea ks appear to be nonrandom affecting different chromosomes in different cancers. Clustering of breaks that occur in specific regions of these chromosomes might provide definite clues for molecular analysis and f urther in-depth studies of cancer predisposed individuals.