SPECIFICITY OF THE PHILADELPHIA CHROMOSOME; CYTOGENIC STUDIES IN CASES OF CHRONIC MYELOCYTIC LEUKEMIA AND MYELOID METAPLASIA

Isochromosome 17q in Ph-negative chronic myelocytic leukemia

No Ph chromosome was found in three clinically suspected chronic myelocytic leukemia (CML) patients, although one had metaphases with trisomy 13. An isochromosome of the long arm of chromosome 17 [i(17q)] was found in these patients when two of them were in acute blastic crisis (ABC) and the other in an early stage of transformation. Although an i(17q) is frequently seen in ABC of Ph-positive CML, it is rarely reported in Ph-negative CML. The finding of an i(17q) chromosome in Ph-negative CML appears to indicate, as in Ph-positive CML, that the disease is transforming into ABC. A series of cytogenetic studies in this group of patients may possibly aid in predicting the patients' pending ABC and may also lead to understanding the pathogenesis of ABC.

In vivo leukemic transformation: cytogenetic evidence of in vivo leukemic transformation of engrafted marrow cells

A 4-year-old girl with acute myeloblastic leukemia was treated with 50 mg/kg cyclophosphamide daily for 4 days before being given 1.7 X 10(8) bone marrow cells/kg from her HL-A identical, MLC nonreactive, cytogenetically normal brother. The patient died 92 weeks after the marrow graft. Postmortem examination showed increased myeloblasts and promyelocytes. Cytogenetic studies before transplantation showed that all sex determination metaphases had an XX pattern, and 41% of the hyperdiploid metaphases had an additional 19-20(F) chromosome. At autopsy all hyperdiploid metaphases with XY pattern and 43% of the hyperdiploid metaphases with an XX pattern had an additional F chromosome. Occasional metaphases with 47, XX, + F or 47, XY, + F were seen during the follow-up studies. These findings indicated that an acute leukemia had developed in the XY cell line of this artifically induced sex chimeric child. This suggests that a leukemic stimulus other than that proposed to be induced by total-body irradiation existed in this patient and transformed the engrafted cells.

Cytogenetic studies of the spleen in chronic granulocytic leukaemia

Using a technique of short-term in vitro culture, cytogenetic studies were performed on splenic tissue from 12 patients with chronic granulocytic leukaemia. In eight patients the disease was in its chronic phase and had been treated with busulphan (seven cases) or splenic irradiation (one case). In five of these patients, small numbers of dividing cells possessing the Philadelphia (Ph1) chromosome were observed; in one, only Ph1 -negative metaphases, presumably those of lymphocytes, occurred, and in two patients no dividing cells were obtained. In four patients chronic granulocytic leukaemia had undergone metamorphosis to an acute phase: in two of these patients no dividing cells were observed in splenic cultures with or without added phytohaemagglutinin: this result may have been attributable to prior cytotoxic therapy. In cultures from the other two patients in metamorphosis, almost all dividing cells were Ph1 -positve and many cells possessed two Ph1 chromosomes. Full cytogenetic analysis in one of these cases showed that the spleen contained several closely related cell lines, apparently reflecting progressive tumour cell evolution.