Non-random chromosome changes in the blastic transformation stage of Ph1-positive chronic granulocytic leukaemia

Characterization of two novel sublines established from a human megakaryoblastic leukemia cell line transfected with p210(BCR-ABL)

Disease progression in chronic myelogenous leukemia (CML) is usually accompanied by chromosomal abnormalities such as an additional Ph chromosome, trisomies of chromosome 8 or 19, or i(17) in addition to the standard translocation t(9;22) (q34;q11). However, detailed studies of the various steps involved during this evolution are difficult to perform, thereby making the study of cell lines that contain the transposed genes BCR-ABL, especially those of human origin, an important focus. In this analysis we investigated the human megakaryoblastic cell line MO7e and its subline transfected with BCR-ABL, MO7e/p210. Initial studies demonstrated that the phenotype of the MO7e line was consistent with a megakaryocytic lineage as originally described and was growth factor dependent in liquid culture. The MO7e/p210 subline, however, was growth factor independent and could be further separated into two distinct sublines based on expression of glycophorin A using the monoclonal antibody R10. The subline R10 negative (R10-) was similar to the parent line MO7e but R10 positive (R10+) cells had a distinct erythroid phenotype. In addition, the R10- and R10+ sublines demonstrated strikingly different colony morphology when cultured in semisolid medium. Furthermore, R10+ cells had additional chromosomal abnormalities not detected in the R10- population. These results demonstrate that the insertion of the BCR-ABL in this human leukemia cell line resulted in two distinct subpopulations of cells, each now growth factor independent, but one with a phenotype and karyotype identical to the parent cell line and the other with a different phenotype and additional chromosomal abnormalities. These two subpopulations derived from the MO7e/p210 transfected cell line may prove useful in further understanding the multistep events that occur in the progression of this disease.

Chromosome 11 rearrangement at band 11q21 in a patient with essential thrombocythemia

A case of essential thrombocythemia with a partial deletion of the long arm of chromosome 11, del(11)(q21) as a sole chromosomal anomaly is reported. Rearrangement of chromosome 11 at band 11q21 has been reported in six patients with chronic myeloproliferative disorders: four with post-polycythemic myelofibrosis, one with myelofibrosis with myeloid metaplasia, and one with Ph+ chronic myeloid leukemia in blastic phase. Except for the last patient, all patients had been treated with 32P and/or an alkylating agent prior to cytogenetic examination. This is the first report of the 11q21 abnormality in essential thrombocythemia seen at diagnosis.

Karyotype evolution in CML: high frequency of translocations other than the Ph

The karyotypes of 33 Philadelphia-positive chronic myelogenous leukemia patients during the blastic phase are reported. Only three patients (9%) had a Philadelphia clone without further chromosomal aberrations, whereas, all the others had karyotype evolution. Aside from some nonrandom abnormalities (+8, i(17q), +Ph, +19) we found a higher frequency of clones with random structural rearrangements (13 cases, 39.4%) than previously reported. From a clinical point of view, however, the additional chromosomal (structural) abnormalities do not significantly influence the patients' survival.

The concept of preleukemia: clinical and laboratory studies

Thirty-five years ago, a handful of astute clinical hematologists began to notice that some of their patients with acute nonlymphocytic leukemia had a history of a preceding ill-defined hemopathy. This "preleukemic" hemopathy was increasingly reported anecdotally and through careful retrospective analyses. In more recent prospective studies, this syndrome has been relatively well defined. Indeed, it is widely accepted that there exists a hematopoietic abnormality not recognizable as classical, overt, acute nonlymphocytic leukemia, which, nonetheless, can represent an early phase of leukemia. In this manuscript, the author reviews the original case reports, the initial retrospective studies, and the prospective studies which have clarified some of the clinical and laboratory features of the preleukemic syndrome. The notion that the preleukemic syndrome represents an established neoplastic process will be reviewed with special attention to assessment of clonal hematopoiesis, cytogenetic studies, and clonal evolution. Studies on induced leukemia and preleukemia in experimental animals and humans will be reviewed as will be the semantic issues which have complicated our ability to compare interinstitutional studies. A simple classification scheme of the myelodysplastic syndromes will be presented as will be a framework agenda for future studies on the pathophysiology of these syndromes.

Chronic granulocytic leukemia: correlation of blastic transformation type with karyotypic evolution

Over a 3-year period, 26 patients with Philadelphia chromosome-positive chronic granulocytic leukemia were studied cytogenetically in both the chronic and blastic transformation phases of the disease; a further three patients were studied only after blastic transformation. Sixteen were considered to have adequate evidence of the type of transformation and form the basis of the report, where chromosome changes have been correlated with the morphological type of blastic transformation. Seven patients developed a myeloblastic transformation, seven a lymphoblastic transformation, and two an erythroblastic transformation. All patients in the myeloid group acquired one or more of the nonrandom changes associated with CGL blastic transformation, viz. +8,i(17q), +19, +22q-. Patients in the lymphoblastic group acquired structural abnormalities, apparently random in nature and usually in a small percentage of cells. The two patients with erythroblastic transformation developed markedly hyperdiploid cells (greater than 50 chromosomes) with both numerical and structural abnormalities. Patients in the lymphoblastic group appeared to have a slightly better prognosis than the myeloid group, whilst the patients with erythroblastic transformation had a very poor prognosis.

Chromosomal characteristics of chronic and blastic phases of Ph-positive chronic myeloid leukemia

To evaluate the appearance of chromosome changes, in addition to the Philadelphia (Ph) chromosome, as predictive and diagnostic parameters of transformation in chronic myeloid leukemia (CML), such changes were analyzed in the chronic phase (CP) and compared with those of the blastic phase (BP) of CML. The common chromosome changes observed in the CP were loss of a Y (-Y), trisomy 8 (+8), an isochromosome for the long arm of chromosome #17 [i(17q)], a double Ph (+Ph), reciprocal translocations, and partial deletions. In most patients with chromosome changes in addition to the Ph, the percentage of abnormal clones increased steadily during the CP and was accompanied by other chromosome changes shortly before or at the onset of the BP, except for cases with -Y or i(17q) clones. In general, most chromosome changes observed shortly before or at the BP were complex. These facts suggest that complex chromosome changes could be utilized as predictive and diagnostic parameters of blastic transformation in CML.

Chromosome banding patterns in patients with chronic myelocytic leukemia

One hundred and nine patients with Ph1-positive chronic myelocytic leukemia were cytogenetically studied with banding methods. Seventy-eight patients were studied in the chronic phase and 39 patients in the blastic phase. The standard translocation was present in 107 cases. Two patients showed complex translocations involving chromosomes No. 6, 9, 22, 11 and No. 9, 22, 11, respectively. Ph1-negative cells were detected in 8 cases (7%). Chromosome aberrations in addition to the Ph1 chromosome were observed in 6 cases (8%) during the chronic phase. The karyotypic findings during the blastic phase were similar to those reported in the past [trisomy 8, iso(17q), and a second Ph1]. The significance of Ph1-negative cells, the geographic heterogeneity of the chromosomal aberrations, the effect of chemotherapy on the appearance of new clones, and the importance of the materials and methods used for the comparison of cytogenetic patterns at different laboratories are discussed.

3. The value of chromosome studies in the classification and management of the leukemias

Chromosome identification techniques have shown the non-random nature of cytogenetic changes in leukemia. In addition, they have identified structural chromosome abnormalities occurring in specific types of acute leukemia as classified by the FAB criteria. Such cytogenetic sub groups are associated with differing prognoses. In acute lymphocytic leukemia, even the ploidy of the leukemic cells appears important in predicting prognosis. Identification of the Philadelphia (Ph1) chromosome has diagnostic significance in chronic granulocytic leukemia. This makes possible the classification of patients into Ph1 + and Ph1 - varieties which have different responses to therapy. Similar variations are found between the 2 groups of patients who do or do not develop additional abnormalities with blastic transformation. The implication of these findings in both acute and chronic leukemia may influence choice of therapy in the future.

Karyotype evolution in a case of chronic myelogenous leukemia with an unusual Philadelphia chromosome translocation, t(4;22), and an additional translocation, t(3;5)

A patient with chronic myelogenous leukemia was found, at the time of diagnosis, to have an unusual Philadelphia chromosome translocation, t(4;22) (q35;q11) and an additional previously unreported translocation, t(3;5) (q27;q22). The blastic crisis, which occurred after 14 months, was characterized by the appearance of i(17q). Ten months later, two different hyperdiploid cell lines with 50 chromosomes were found in about 20% of the metaphases examined.

Chromosomes and causation of human cancer and leukemia: XL. The Ph1 and other translocations in CML

To date, 85 cases with unusual Ph1 translocations have been described and are summarized in the present work. Of the 85 translocations, 41 were simple and 44 complex. Only chromosomes #1, #4, #8, and #20 and the Y have not been found to be involved in simple translocations and #12, #16, #18, #20 and the Y in complex ones. Chromosomes #18, #20, and Y have not been involved to date in either complex or simple Ph1 translocations. Four cases have been reported in whom more tan three chromosomes were involved in the Ph1 translocation and only four cases in whom the #9 was not involved in complex Ph1 translocations. The chromosomal changes, in addition to the Ph1, accompanying unusual Ph1 translocations in CML are not different from those seen in cases with the standard type of Ph1 translocation. Translocations (other than the Ph1) in CML occur in less than 1% of the cases and, to date, have found to involve all the chromosomes except the X and Y. With rare exceptions, in complex Ph1 translocations 1) the distal end of #22 is translocated to a third chromosome (i.e., other than #9), a part of which is translocated to #9, #2) the breaks in the involved chromosomes probably occur concomitantly, and 3) a characteristic PH1 chromosome is present. The survival of patients with CML and unusual or complex Ph1 translocations does not differ significantly from that of patients with the standard Ph1-translocation.