Genetic rearrangements in leukaemia and lymphoma / J.M. Goldman, D.G. Harnden.

Date:
1986
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetic rearrangements in leukaemia and lymphoma / J.M. Goldman, D.G. Harnden. Source: Wellcome Collection.

    32/200 (page 16)
    16 GENETIC REARRANGEMENTS since there are still some cases which do not seem to have any abnormality^'. However, in this particular case, the assumption was made that divisions of unstimulated peripheral blood cells were representative of the mahgnant population. Such subclassification is becoming apparent in many cases and led Yunis'^ to suggest that the type of aberration found in the majority of ANLL patients could be predicted on the basis of FAB classification and moreover, that cytogenetic studies in such cases are now an essential part of the diagnosis and assessment of prognosis. The recognition of the association of specific chromosome regions with specific leukaemia types will also facilitate the assignment of genes controlling differentiation and development of haemopoietic cells to specific chromosomal loci. The problem of normal cells Yunis'^ also touched on the second problem, namely the fact that only some of the cells studied show the specific abnormality. In some cases, direct examination of the bone marrow showed only normal cells, whereas short term culture revealed at least a proportion of abnormal cells. This both explains some of the so-called 'normal' cases and gives an indication of the explanation of cases with mixtures of normal and abnormal cells. Cells with normal chromosomes are likely to be normal cells from other lineages not involved in the leukaemic process and not yet displaced from the marrow by the leukaemic cells. This concept first emerged from the study of the chromosomes of cases of acute promyelocytic leukaemia (APL), where a specific translocation t(15;17) has been recognized for some years. At the Second International Workshop on Chromosomes in Leukaemia^^ a curious variation in geographic distribution, (see Table 1.9) of the anomaly was apparent, which suggested that perhaps ethnic or perhaps different environmental factors were involved in the aetiology of the disease. However, recent work by several groups'^ has drawn attention to the probability that this distribution is a technical artefact. Chromosomal preparations from APL patients have been made by different techniques in different laboratories, some direct and some by short term (24-48h) culture. Short term culture gives a higher proportion of positive cells and it has been shown very elegantly that two different populations of cells are being studied - the chromosomally normal erythroblasts and the chromosomally abnormal promyelocytes. In short term culture, metaphases from the promyelocytes predominate and laboratories using short term culture have a high proportion of positive cases. The direct method, usually thought be to preferable in the study of the chromosomes of leukaemic patients, can fail to reveal the abnormal population. When comparisons are made between laboratories using similar techniques, consistent results are obtained and moreover all cases of APL have the t(15;17) translocation. While not all of the currently recognized specific aberrations can be defined in terms of clinical or haematological parameters, it seems possible that in