Chromosomes and causation of human cancer and leukemia. VI. Blastic phase, cellular origin, and th Ph1 in CML

Management of chronic myeloid leukemia in blast crisis

Due to the high efficacy of BCR-ABL tyrosine kinase inhibition (TKI) in chronic phase (CP) chronic myeloid leukemia (CML), the frequency of blast crisis (BC) is greatly reduced compared to the pre-TKI era. However, TKI treatment of BC has only marginally improved the number of favorable responses, including remissions, which for the most part have only been transitory. Occasionally, they provide a therapeutic window to perform an allogeneic stem cell transplantation (allo-SCT). The challenge remains to improve management of BC with the limited options available. We review and summarize articles pertaining to the treatment of BC CML published after 2002. Additionally, we will discuss whether there is a need for a new definition of BC and/or treatment failure.

Unique secondary chromosomal abnormalities are frequently found in the chronic phase of chronic myeloid leukemia in southern Vietnam

During the Vietnam War, southern Vietnam was exposed to a large amount of dioxin, a strong human carcinogen. Although we have observed much shorter survival in southern Vietnamese chronic myeloid leukemia (CML) patients, the cause remains to be clarified. Here, we report cytogenetic and molecular findings for 47 CML patients. Cytogenetically, the Philadelphia (Ph) chromosome was found in 44 patients (93.6%); of the remaining 3 patients with Ph-negative CML, 2 exhibited BCR/ABL transcripts but no BCR/ABL FISH fusion signals, suggesting the existence of two clones, with and without the BCR/ABL fusion gene. Surprisingly, in 17 patients (36.2%) (4 at diagnosis, 11 during chronic phase, and 2 in accelerated phase), we found several unique secondary chromosome abnormalities including trisomy 13, partial trisomy 13, and abnormalities of 1p, 3p, 6p, 7p, 10p, and 11p, which are different from the so-called additional chromosome abnormalities (extra Ph, +8, i(17q), +19, and +21) observed in blastic phase CML. FISH analysis revealed the Ph translocation with der(9) deletion in 11 patients (23.4%). Of these, 2 had two clones, with and without der(9) deletion, suggesting that der(9) deletion would occur in a subset of patients during disease progression. These observations point to preexisting genetic instability that induces various secondary chromosome abnormalities and multiple clones, resulting in shorter survival.

Cell biology of CML--a model linking the chronic and terminal phases

A model for the pathogenesis of chronic myeloid leukaemia (CML) is proposed. It relies on a comparison between normal steady-state and regenerating haemopoiesis and suggests that chronic phase CML stem cells have a finite capacity for self-renewal. According to the model, metamorphosis of the disease occurs once the potential for chronic phase cell production has been exhausted. The model considers also the generation of leukocytosis in the chronic phase and the origin of the terminal phase. Comparison with normal regenerating haemopoiesis allows discrimination between features of CML that are fundamentally abnormal and those which are normally associated with regeneration.

Chronic myelogenous leukemia. Prolonged survival with spontaneous decline in the frequency of Ph1-positive cells and subsequent development of mixed Ph1-positive and Ph1-negative blast crisis

A 23-year-old man developed Ph1-positive chronic myelogenous leukemia in 1966. After two short courses of busulfan not associated with severe myelosuppression, the frequency of Ph1-positive metaphases in his bone marrow was 40%. Over the next eight years, he remained hematologically stable without further therapy. During that time there was a progressive decline in the frequency of Ph1-positive metaphases in his bone marrow to 3% by 1976. His disease subsequently transformed to an acute lymphoblastic leukemia. Cytogenetic studies of the marrow at the onset of blast crisis and of cultured marrow blast cells suggested that the blasts were a mixture of Ph1-positive and Ph1-negative cells. This patient was thus unique in that he demonstrated spontaneous decline in the frequency of Ph1-positive cells in his bone marrow and he developed blast crisis with an apparent mixture of Ph1-positive and Ph1-negative blasts. These findings demonstrate that a Ph1-positive cell clone may lose its proliferative advantage over Ph1-negative cells and raise the possibility that Ph1-negative cells persisting in patients with Ph1-positive chronic myelogenous leukemia may be abnormal and, like the Ph1-positive cells, may be susceptible to acute leukemic transformation.

Clonal changes in chronic granulocytic leukemia in blastic transformation and during remission

Cytogenetic studies of the peripheral blood and marrow of a patient with chronic granulocytic leukemia in blastic transformation revealed the following abnormalities: 1) a Philadelphia chromosome with the usual 9:22 translocation; 2) a three break rearrangement (insertion) of chromosome #11; and 3) a deletion of the short arm in chromosome #16. Clinical and hematologic remission developed after three courses of intermittent chemotherapy with transient but complete bone marrow aplasia. Studies performed during remission revealed two cellular clones. One had the same karyotype already described and the second showed only a Ph1 chromosome. We postulate that the pretreatment clone evolved from Ph1-positive cells in this patient with chronic granulocytic leukemia during a short, undiagnosed stable phase. Treatment allowed the reappearance of the Ph1-positive clone. The second abnormal clone was apparently partially eradicated but normal cells did not repopulate the bone marrow, suggesting that either the Ph1-positive cells were greatly resistant to therapy or that there were no remaining normal myelogenous stem cells. In addition, we found that there have been few reports of abnormalities involving chromosomes #11 and #16, and that an inserting chromosome #11 has never been reported.

Chromosome abnormalities, clinical and morphological manifestations in metamorphosis of chronic myeloid leukemia

Seventeen cases of chronic myeloid leukemia (CML) in metamorphosis have been investigated by cytogenetic methods. Six patients were studied in slow transformation and others in the terminal blastic phase of the disease. Of these, 3 cases were myeloid, 3 myelomonocytic, 1 megakaryoblastic, 1 promyelocytic and 4 lymphoid in their morphological and cytochemical appearance. Some correlation could be observed between the clinical, morphological, cytochemical and cytogenetic findings of the different subgroups. The results demonstrate the importance of chomosome investigations in the early diagnosis of metamorphosis and in distinguishing the different subgroups of the terminal stage of CML.

The significance of Ph1 mosaicism: a report of six cases of chronic granulocytic leukaemia and two cases of acute myeloid leukaemia

Six cases of chronic granulocytic leukaemia (CGL) and two cases of acute myeloid leukaemia (AML) with dual populations of karyotypically normal and Philadelphia (Ph1) chromosome-positive cells are described. GTG and QF-banding characterized the Ph1 as resulting from a 9/22 translocation in all eight cases. Four of the patients suffering from CGL presented with 100% Ph1-positive bone marrows, and after receiving intensive chemotherapy, karyotypically normal cells were demonstrated. The other two patients with CGL showed Ph1 mosaicism at presentation. The two patients with AML exhibited Ph1 mosaicism at presentation and throughout the course of the disease. In both of these patients, a marker No. 10 chromosome was found in some of the Ph1-positive cells and in one hyperdiploidy was observed to have developed only in the clone with the additional chromosome anomaly.

Persistence of nucleolar RNA-rich structures and Ph1 duplication in the blastic crisis of chronic myeloid leukaemia

Nucleolar persistence in metaphase plates is a feature observed in most of the cells in neoplastic processes. Pathological persistence or fragmentation of the nucleoli is thought to be the cause of some numerical chromosomal aberrations due to non-disjunction of the chromatids, with particular involvement of the satellite chromosomes. Thus, a combined selective staining of both the nucleoli (amido black 10B according to Mundkur and Brauer's cytochemical technique) and the chromosomes (neutral red) was applied to the metaphase plates of patients with chronic myeloid leukaemia in the blastic crisis. Duplicated Ph1 was associated with amido black-stained areas at a very high rate in some cases. Since the blastic crisis in chronic myeloid leukaemia is characterized by the appearance of an increased number of immature, highly nucleolated cells, these findings lend support to the hypothesis that the duplication of the Ph1 represents a feature possibly favoured by the pathological persistence of nucleolar RNA-rich structures in the metaphase.

Cytogenetic studies of chronic myelocytic leukemia in children and adolescents

In a 3 1/2 year cytogenetic study of 107 leukemia patients diagnosed in childhood and adloescence, 8 presented with chronic myelogenous leukemia (CML). Seven of the 8 had chromosomal abnormalities. Six had the Ph1 chromosome; 5 had the usual 9;22 translocation. Two patients had involvement with chromosome 15; one had a 9;15 translocation in Ph1 positive cells during remission while a second had a 1;15 translocation during blastic crisis. The 2 patients who did not have a Ph1 chromosome survived 13 and 30 months, respectively, considerably less time than the 4+ year survival in most of those with Ph1 positive CML.

Cytogenetic remission in a Ph1-positive case of chronic myelogenous leukaemia

Unusual cytogenetic findings in a case of chronic myelogenous leukaemia in the course of an aplastic crisis induced by busulfan therapy are reported. The proportion of Ph1-positive cells in bone marrow aspirates fell from 100% before treatment to 8.6% following aplasia. It increased gradually during recovery, and normal cells still represented 25.7% of the metaphases 20 months later. After a 38-months' remission without therapy the disease relapsed and the Ph1 chromosome was found in 100% of the bone marrow cells.

Eradication of the intramedullary Ph1 positive cell line without accompanying improved survival in chronic myelogenous leukemia

A patient with Ph1+ chronic myelogenous leukemia is presented who upon entering the accelerated phase of her disease developed aneuoploidy, including duplication of the Philadelphia chromosome. Intensive chemotherapy resulted in a marrow remission and reversion of the marrow karyotype to normal. Rather than entering an anticipated prolonged remission she relapsed four weeks later with return of her aneuploid clone. Postmortem examination revealed several unsuspected areas of extramedullary leukemia, perhaps serving as the source for repopulation of the marrow. If a desired goal of therapy is to eradicate the Ph1+ cell line, then we recommend that it be undertaken early in the disease when there is the least likelihood of extramedullary leukemia.

Trisomy 8 in the chronic phase of Philadelphia negative chronic myelocytic leukaemia

An unusual case of Philadelphia negative chronic myelocytic leukaemia and an extra chromosome 8 in all bone marrow cells is described. The abnormality was present at diagnosis of the disease and throughout the chronic phase which lasted for somewhat less than 2 years. The patient died soon after the blastic transformation with no other chromosomal abnormalities.

Non-leukemic dividing cells in the blood of leukemic patients

Spontaneous mitoses in the blood of 67 patients with acute leukemia were enumerated and their identity determined by cytogenetic methods. Most patients were children with acute lymphoblastic leukemia. Simultaneous 16- to 20-hour cultures of blood leukocytes (Bu) and of bone marrow (BM) cells were performed without phytohemagglutinin (PHA). Blood leukocytes were also cultured with PHA for 72 hours (BPHA). Mitoses in Bu cultures were counted, and karyotypic analysis performed on cells from the three culture types. In 21 control subjects, Bu cultures usually yielded no mitoses. Relapse and remission patients both displayed significantly more Bu mitoses than the controls. The karyotypes of Bu, BPHA, and BM mitoses in remission patients were normal. Fifty percent of relapse patients displayed cytogenetically abnormal leukemia cell lines; the percentage of their abnormal karyotypes was significantly higher in BM cells than in Bu or BPHA cells. The majority of the mitotic cells in Bu cultures from both relapse and remission patients appear to be of a nonleukemic origin. The number of mitoses could not be correlated with type of leukemia, hematologic parameters, or prognosis.

[Myelomonocytic leukemia: clinical, cytological, and cytogenetic studies of acute, subacute, and chronic forms (author's transl)]

44 patients suffering from myelomonocytic leukemia (MML) have been observed over the last four years. They have been subclassified in acute myelomonocytic and acute monoblastic leukemias (AMML, n = 12; AMoL, n = 10), subacute myelomonocytic leukemias (SMML, n = 13), and chronic myelomonocytic leukemias (CMML, n = 9) on the basis of bone marrow cytology(blast and promonocyte counts, maturation of granulopoesis) and cytochemical findings (peroxydase and unspecific esterase reaction). This subclassification has been proved to be of prognostic relevance by its good correlation with the mean survival times (AMML : 4.5 months, AMoL : 2.4 months, SMML : 8 months, CMML : 18 months). The acute forms have been treated in general with combined cytostatic chemotherapy, whereas SMML and CMML have been treated this way only in case of progression to an acute phase. These progressions to an AMML have been observed more often and earlier in subacute forms than in chronic forms. The diagnosis of SMML and CMML is supported by the finding of sea-blue histiocytes in the bone marrow, increased lysozyme levels in serum and urine and by the absence of the Philadelphia-Chromosome.

Chromosomal evolution in a haploid frog cell line: implications for the origin of karyotypic variants

ICR 2A, a haploid cell line derived from Rana pipiens embryos, has remained haploid in number of chromosones and their relative lengths and centromere positions for 500 cell generations. After this time, two new haryotypes appeared; relative length measurements indicate that the first has a translocation from chromosome 4 to 6, the second translocations from 3 and 4 to 6 and 7. The single exchange karyotype is not a precursor for the double exchange according to a statistical analysis. The double exchange karyotype characterized 90% of some cultures although a selective advantage could not be demonstrated for these cells. The observations suggest that a non-clonal or multicellular origin may account for these karyotypic variants.

Chromosomes and causation of human cancer and leukemia: XXVIII. Value of detailed chromosome studies on large numbers of cells in CML

Comparison of the chromosome findings obtained on routine examination (10-50 cells) of the marrows from patients with Ph1-positive CML with those based on a large number (110-500 cells) of metaphases in six of these patients, in whom appropriate material was available, revealed the presence of small percentages of aneuploid cells in the marrow during the chronic phase of the disease and not seen with the routine procedure. These aneuploid cells may ultimately constitute the dominant clone during the blastic phase of the chronic myelocytic leukemia (CML). Furthermore, karyotypically abnormal cells, in addition those observed on routine study, were detected in the blastic phase when a large number of cells was examined. The value and implications of these observations are discussed.

Non-random karyotypic evolution in chronic myeloid leukemia

The chromosome banding pattern was analyzed in bone-marrow cells and/or spleen cells of 10 patients in the blastic phase of chronic myeloid leukemia (CML). It was obvious from the karyotype analysis that the chromosome aberrations occurring addition to the Philadelphia chromosome (Ph1) were strictly non-random. An extra Ph1, trisomy 8 and/or trisomy for the long arm of chromosome 17 were observed in all cases. This consistent pattern of chromosome involvement in CML was confirmed in 57 cases from the literature studied with banding techniques. In 88% of the total number of cases with further changes at least one of the three main chromosomal aberrations was found ("major route" of karyotypic evolution).

Extremely long duration of chronic myeloid leukaemia with Ph1 negative and Ph1 positive bone marrow cells

A male patient still surviving 17 years after the diagnosis of chronic myeloid leukaemic (CML) is described. A chromosome analysis of the bone marrow 16 years after the diagnosis revealed 84% Ph1 negative and 16% Ph1 positive cells, all containing the Y chromosome. The disease has been very sensitive to treatment with busulphan but bone marrow hypoplasia has not been induced. It is probable that in some CML patients with such a double cell population the prognosis may be extraordinarily good and that they run a considerable risk of being overtreated due to a pronounced sensitivity to alkylating drugs. Such rare cases should not serve as arguments for aggressive treatment of CML.

Chromosomal mosaicism associated with prolonged remission in chronic myelogenous leukemia

The nature of the relationship between normal stem cells and the leukemic cells of chronic myelogenous leukemia (CML) is of considerable theoretical and practical importance. We studied a patient with CML who has maintained a complete hematologic remission for eight years without therapy. Presently, the only documentable abnormality is mosaicism for the Philadelphia (Ph1) chromosome. Studies of his bone marrow in vitro revealed normal colony formation in agar and normal cellular proliferation and differentiation in liquid culture. Observations in this patient indicate that a Ph1-positive clone may coexist with normal stem cells during prolonged remission in CML and the Ph1-positive cells may not always have a growth advantage over normal cells. The culture studies further suggest that the diminished proliferative capacity of the leukemic cells was not due to in vivo host suppressive factors.

Chromosomes and causation of human cancer and leukemia. XII. Banding analysis of abnormal chromosomes in polycythemia vera

The chromosome constitution of bone marrow cells was determined in 13 patients with polycythemia vera (PV). In 5 of these patients definite karyotypic abnormalities were found: 3 with 46,XY,Fq-; 1 with 46,XY,11q-, 13q-; and 1 with missing Y. The latter cytogenetic finding is thought not to be related to the PV. The 4 patients with partial deletions of chromosomes had been treated with 32P, and 3 of them with chemotherapy also. Karyotypes from 2 of these patients, 1 with 46,XY,20q-, and another with 46,XY,11q-,13q- were examined with G and/or Q banding. From the results of the banding analysis, it appears that the abnormal chromosomes were due to simple deletions at specific sites on their arms, particularly in the cases with the F abnormality (20q11). The breaks occurred in the regions C11q and D12q. The portions missing from the original chromosomes could not be found on any chromosome. Most patients with PV do not develop chromosomal abnormalities through the course of their disease; when such abnormalities appear (20q- in particular), they seem to result exclusively from radiation (and possibly chemo-) therapy. Thus, cytogenetic changes do not appear to play a crucial role in the genesis of PV.