Genética hereditária: pesquisas atuais

Abstrato

Gross Chromosomal Aberrations are Early Alarms for Malignancy: A Re-Emphasis

Hit Kishore Goswami*

A few chromatin dots of variable sizes were encountered in squashes of brain tumour tissues viz. medulloblastoma, ependymoma and tuberculoma along with hyper and hypoploid chromosome counts way back in 1973. Similar chromosomal features were again observed in metaphases of persons exposed to methylisocyanate gas in Bhopal during midnight of 2nd to 3rd December, 1984. Follow-up studies continued during 1984-1999 and comparative assessments on chromosomal damages were attempted by SCE (sister chromatid exchanges) as well as by scoring more than a dozen types of chromosomal aberrations on 678 individuals by C and G-banding and Feulgen’s and Aceto-orcein staining procedures on cultured-lymphocytes, details of which, have been published earlier. This short paper reemphasizes the importance of certain chromatin dots (named as Marker dots) which were seen emanating from chromosomes. These marker dots appeared reliable early indicators of neoplastic transformations. During follow-up studies on various malignancies we had recorded presence of these marker dots in almost all of them. This computation of slides involved careful scrutiny of more than 40,000 metaphases from patients of various malignancies, pathological disorders and newly discovered chromosome syndromes (e.g. Crossed Renal Ectopia with pelvic lipomatosis; Hemihypertrophy with melanosis of Ito, etc.). Intriguingly, only selective chromosomes are involved (chromosomes 1, 2, 3, 5, 6, 8, 9, 11, 12, 13, 16, 17 and Y) in emanating marker dots. Obviously, it appears that the molecular attenuation of chromatin structures movable from chromosomes is related with triggering neoplastic transformations. Specific attention was paid on appearance of “marker dots” which were observed in seemingly normal persons but later, after a gap of 2 to 6 years, some of them exhibited signs of malignancy. Such observations were possible only on those persons who could be re investigated after a gap of 2 or 3 years. Gross chromosomal aberrations such as PCD (premature centromeric divisions) acrocentric associations, hyperploid cells, translocations and deletions with marker dots appear to be precursors to firm installation of chromosomal mutagenesis in cultured lymphocytes. Obviously, search for marker dots and these aberrations in metaphases of person(s) belonging to a cancer-patient family can be of vital importance to warn for early diagnosis and prognostic approach. Marker dots simply “alarm” to inform firm installation of chromosomal mutagenesis which encompasses various chromosomal aberrations. In turn, due to many other intragenic factors, cells are transformed to malignant cells in certain individuals.