Loss of myeloid differentiation antigens precedes blastic transformation in chronic myelogenous leukemia

In order to determine whether antigenic patterns alter with disease progression and are thereby suggestive of impending blast crisis in chronic myelogenous leukemia, 50 bone marrow biopsy specimens from 32 patients were examined retrospectively using indirect immunoperoxidase labeling with three monoclonal antibodies that detect myeloid antigens. Monoclonal antibodies PMN13F6, PMN7C3, and PMN8C7 detect human neutrophil antigens that first appear at the myeloblast, promyelocyte, and metamyelocyte stages of differentiation, respectively, and persist throughout later differentiation. Percentages of antigen-positive bone marrow cells during the chronic phase were compared with percentages of antigen-positive cells at blast transformation, and time from bone marrow biopsy until blast crisis was correlated with the percentage of bone marrow cells expressing these antigens. Bone marrow biopsy samples from patients in the chronic phase who continue to remain clinically stable 4 to 106 months after biopsy expressed PMN13F6 antigen on 82% +/- 9% (mean +/- SD) of cells, PMN7C3 antigen on 62% +/- 14% of cells, and PMN8C7 on 68% +/- 14% of cells. Bone marrow biopsy specimens obtained from patients 1 or more years prior to blast transformation expressed PMN13F6 antigen on 81% +/- 12%, PMN7C3 antigen on 71% +/- 16%, and PMN8C7 on 64% +/- 16% of cells. Bone marrow biopsy samples obtained between 2 months and 1 year prior to blast crisis expressed PMN13F6 antigen on 68% +/- 15%, PMN7C3 on 51% +/- 17%, and PMN8C7 antigen on 46% +/- 18% of cells. Bone marrow biopsy specimens taken at the time of blast transformation expressed PMN13F6 antigen on 20% +/- 25%, PMN7C3 antigen on 19% +/- 25%, and PMN8C7 antigen on 13% +/- 25% of cells. The difference between the mean of antigen-positive cells from bone marrow biopsy samples obtained at the time of blast crisis was significant compared with the mean of positive cells from biopsy specimens obtained at all other phases of the disease (P less than .001 for all three antibodies). There was a positive correlation between loss of myeloid antigens and disease progression as determined by simple regression of log time and correlation analysis (PMN13F6, r = .6533, P less than .005; PMN7C8, r = .6304, P less than .005; PMN8C7, r = .5215, P less than .05). There was a negative correlation between percentage of immature cells and time to blastic crisis (r = -.6206, P less than .005).(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic implications of basophil differentiation in chronic myeloid leukemia

Basophilia has been reported to indicate an accelerated phase of chronic myeloid leukemia (CML), heralding a poor prognosis. We have studied 47 patients with chronic-phase CML by basophil growth and differentiation assays in vitro, demonstrating an association between basophil growth index (BGI) and clinical time to blast crisis as well as overall survival. In addition to confirming an association between positive BGI and phase of CML in a larger group of patients, a positive BGI predicted death or blast crisis within 2 years' study of chronic phase CML (p less than 0.01), with a sensitivity of 78%, specificity, 81%; the positive predictive value of a positive test, 64%; and a negative predictive value of a negative test, 89%. The survival experience of the 22 evaluable patients with chronic-phase CML and a positive BGI was significantly worse than the survival of the 19 patients with a negative BGI (p less than 0.0001). At 1, 2, and 3 years the proportion of surviving patients with a positive BGI was 0.64, 0.32, and 0.23, respectively, compared with 1.00, 0.90, and 0.79 for those with a negative BGI. The median survival of chronic phase CML patients with a positive test at diagnosis (n = 14) was 27 months versus 54 months for those with a negative diagnosis (n = 14) (p less than 0.05). These findings emphasize the prognostic utility of basophil growth assays in CML and suggest a molecular relationship between leukemic transformation and basophil lineage expression.     

Abnormal methylation of the calcitonin gene marks progression of chronic myelogenous leukemia

The clinical aspects of disease progression in chronic myelogenous leukemia (CML) are well established, but the nature of the molecular events responsible is not known. We have previously reported a consistent pattern of novel sites of methylation in the 5' region of the calcitonin (CT) gene and other chromosome 11p loci in acute myelogenous and and lymphoid leukemias. In the present study, CT gene methylation patterns were investigated in peripheral blood from 51 patients with CML. Abnormal patterns were found in only 2 of 31 patients in chronic phase, but in 5 of 8 patients in accelerated phase, and in 11 of 12 patients in blast crisis (P less than .005). For one patient studied in blast crisis, abnormal CT gene methylation was found in the peripheral blast cells but not in the granulocytes. In two of three patients studied with CML and having normal peripheral cell patterns, abnormal patterns were found in marrow blast cells. In one patient, only partial normalization of the CT gene methylation pattern was seen after chemotherapy induction of a second chronic phase and the patient relapsed 5 months later. Our findings indicate that abnormal methylation of the 5' region of the CT gene is regularly a marker of disease progression in CML which may prove clinically useful. This abnormal methylation site is part of an imbalance in DNA methylation that may play a role in the progressive genetic instability which characterizes the advancing stages of CML.     

Changes in serum RNase activities in chronic phase and acute crisis of chronic myelocytic leukemia

We investigated serum acid and alkaline RNase activities in 16 cases of acute crisis of chronic myelocytic leukemia (CML), 21 cases of untreated CML, and 13 cases of treated CML, to clarify clinical significance of the determination of RNase activities in acute crisis of CML. We obtained results as follows; the ratio of acid to alkaline Rnase activities (Ac/Al ratio) of chronic phase of CML was 1.64 +/- 0.47 (mean +/- SD) in the untreated cases, and was 1.32 +/- 0.16 in the treated cases. The Ac/Al ratio always indicated over 1.0 in the chronic phase of CML without any relationship to treatments. On the other hand, in the cases of acute crisis, the Ac/Al ratio was significantly lowered (0.94 +/- 0.22) as compared to the chronic phase of CML (p less than 0.001), and was similar to that of acute leukemia. The acid and alkaline RNase activities of the blast from the patients with acute crisis of CML showed remarkably lower value than those of leukemic cells from patients with chronic phase of CML. Therefore, it was Suggested that the return to normal range of Ac/Al ratio in acute crisis of CML depended on marked decrease of RNase activities of blasts. Thus, serial determinations of the enzyme activities are considered to be one of useful tools for prediction of acute crisis of CML.     

Early T-cell features in blast crisis of Ph1-positive chronic myeloid leukaemia

A patient with Ph1-positive chronic myeloid leukaemia (CML) presented in extramedullary blast crisis. Whereas the peripheral blood and bone marrow features were consistent with the chronic phase of CML, study of the enlarged lymph nodes demonstrated massive replacement by Ph1-positive blast cells of lymphoblastic morphology. Such blast cells showed diffuse acid phosphatase positivity, were positive for TdT, and had an enzyme pattern (adenosin-deaminase, purine-nucleosidephosphorilase and lactate-dehydrogenase) typical of immature T-cells. To further characterize the phenotype of the blast cells, they were analyzed for surface markers using a panel of monoclonal antibodies selected to identify differentiation antigens of T cells, B cells and myeloid cells. The results of the latter analysis were consistent with an early T-cell origin of the blast cells, since they were positive for TdT, CRIS1 (T1), E rosettes and OKT10, and were negative for OKT3, Leu3 and OKT8. These features demonstrate that T-cell markers may also be expressed in blast crisis of CML and provide evidence that T-cells may share a common stem cell with myeloid and B-cells in CML.     

Rearrangement and expression of p53 in the chronic phase and blast crisis of chronic myelogenous leukemia

We tested a population of over 60 patients with chronic myelogenous leukemia (CML) for changes in the structure and expression of the p53 gene, which is located on chromosome 17. Six of 27 (22%) blast crisis samples and 3 of 5 (60%) accelerated phase samples had rearrangements of chromosome 17, whereas only 3 of 42 (7%) chronic phase patients had cytogenetic changes in chromosome 17. There was no loss of heterozygosity during the transition to blastic crisis among seven individuals who were informative for polymorphic probes for regions in or around the p53 gene on 17p. One patient in the chronic phase and one patient in the blastic phase of the 61 CML patients studied exhibited rearrangements of the p53 gene that were detectable by Southern analysis. One p53 allele was rearranged in the chronic phase patient and both p53 alleles were rearranged in the blastic phase patient. The p53 messenger RNA (mRNA) was of normal size (2.8 kb) in chronic phase and blast crisis, and the expression of the p53 gene was at least as high or higher in blast crisis as in the chronic phase of CML. The high incidence of abnormalities of chromosome 17 in blast-crisis CML found in our studies and the discovery of rearrangements of the p53 gene in two CML patients studied suggest that further study with probes for the p53 gene and anonymous polymorphic sites in chromosome 17 should be conducted in CML.     

慢性髓细胞白血病急变期形态学及免疫学和细胞遗传学特征研究

目的：探讨慢性髓细胞白血病急变期（CML－BC）的形态学、免疫表型和细胞遗传学法及流式细胞仪进行细胞免疫分型,细胞遗传滂采用直接法或短期培养法制备染色体标本,采用R显带技术进行核型分析。结果：免疫分型结果显示：急变为急性髓细胞白血病（AML）23例占74．2％;急性淋巴细胞白血病（ALL）5例占16．1％,均为B系ALL,其中4例同时伴有髓系表达;急性未分化细胞白血病1例,B系和髓系急性混合细胞白血病（AMLL）2例。31例CML－BC中21例（67．7％）的急变患者CD34^ ,其中4／5（80．0％）ALL,15／23（65。2％）,2／2AMLL均为CD34^ 。AML急变患者中具有CD7和CD34共表达者为8／23（占34．8％）。细胞遗传学分析表明,14／27（51．9％）和急变期患者出现Ph染色体以外的附加核型异常,其中有＋8（3／14）,＋Ph(3/14),i(17q)(2/14),Y染色体丢失（1／14）及复杂易位5／14）。结论：CML－BC是一干细胞疾病,原始细胞分化阻滞在早期阶段,故预后差。MIC分型在CML－BC诊断,预后判断及指导治疗方面均有重要价值。     

Thiotepa, busulfan and cyclophosphamide as a preparative regimen for allogeneic transplantation for advanced chronic myelogenous leukemia.

Thirty-six adults with chronic myelogenous leukemia (CML) in second or greater chronic phase, accelerated phase, or blast crisis underwent marrow or blood stem cell transplantation from an HLA-matched sibling using high-dose thiotepa, busulfan and cyclophosphamide (TBC) as the preparative regimen. All evaluable patients engrafted and had complete donor chimerism. One patient failed to clear meningeal leukemia, and one patient had one of 30 metaphases positive for the Philadelphia chromosome at 2 months post transplant. The remainder of the patients studied had eradication of CML documented by cytogenetics and/or Southern blot for BCR gene rearrangement, and 13 of 15 patients studied became negative for the BCR gene rearrangement by polymerase chain reaction. Three-year relapse rate is 42% (95% CI, 19-64%). The relapse rate was significantly lower for patients transplanted without blast crisis (9% vs 100%, P < 0.001). Eight (22%, 95% CI, 10-39%) patients had severe or fatal veno-occlusive disease (VOD). Elevated liver enzymes within 1 month prior to transplantation and transplantation using marrow were significantly associated with the occurrence of VOD. Three-year survival is 28% (95% CI, 13-43%). Survival was significantly higher for patients transplanted without blast crisis (45% vs 0%, P = 0.01). TBC is an effective preparative regimen for CML in accelerated phase but not refractory blast crisis, and it should be used with caution in patients with prior hepatopathy who have an increased risk of severe VOD.     

The role of cellular maturation in neutrophil heterogeneity

Previous studies have shown that many neutrophil (PMN) characteristics are heterogeneous but the origin of PMN heterogeneity is unknown. It is unclear if PMN functional heterogeneity is secondary to maturational differences or due to distinct subpopulations of cells that possess different functional capacities. The PMN 31D8 antigen is a useful probe for evaluation of PMN subpopulations. The majority of PMNs (approximately 85%) exhibit a high intensity fluorescence after 31D8 monoclonal antibody (MoAb) labeling (31D8 enriched or "bright" PMNs) as determined by flow cytometric analysis. These cells are more functional than cells with low intensity fluorescence (31D8 diminished or "dull" PMNs). Various immunologic, clonogenic and functional techniques were used to study the expression of the 31D8 antigen in HL-60 cells and myeloid cells in order to evaluate antigenic and functional heterogeneity during morphologic maturation. The results of this study indicate that the percentage of 31D8 antigen positive (31D8 antigen enriched and diminished) bone marrow cells increases from 20 +/- 11% in myeloblast cells to 68 +/- 10% in promyelocytes, 93 +/- 2% in myelocytes and 99 +/- 1% in bands and PMNs. 31D8 antigen enriched cells first appear at the myelocyte stage (32 +/- 10%) and increase in bands (52 +/- 13%), marrow PMNs (62 +/- 13%) and peripheral blood PMNs (88 +/- 4%). These data indicate that the heterogeneous expression of 31D8 antigen in PMNs is due, at least in part, to maturational differences within the PMN population and raise the possibility that other heterogeneously expressed PMN characteristics are also maturationally derived. They also suggest that 31D8 antigenic expression may be a more precise indicator of myeloid functional maturation than maturation as identified by cellular morphology.     

Further evidence for the molecular heterogeneity of chronic myeloid leukemia

Summary Cytogenetic and molecular techniques were performed on samples obtained from 29 patients with chronic myelocytic leukemia (CML); 27 were in the chronic phase and two were in blast crisis. A further five cases were also analyzed, two with atypical CML (aCML), one with chronic neutrophilic leukemia (CNL), and two with juvenile CML (JCML). Most of the cases with typical CML were Philadelphia chromosome (Ph) positive and had a rearrangement within the major breakpoint cluster region (M-bcr). One of these cases was shown to be Ph positive but showed no rearrangement within the M-bcr. Two cases with clinical features typical of CML were Ph negative. One of these showed a rearrangement within the M-bcr, but no rearrangement was demonstrated in the other. Both patients in blast crisis were Ph positive and M-bcr positive. One showed a second Ph. Patients with aCML were Ph negative and had no M-bcr rearrangement. A polymorphism within the M-bcr was found withBglII in one case. No Ph chromosome or M-bcr rearrangement was found in CNL or JCML. These data support the molecular heterogeneity reported in CML.     

Ultrastructural histochemical alteration of the plasma membrane in chronic myelocytic leukemia

Ultrastructural histochemical evaluation of the surface of normal human blood and bone marrow cells exposed to the pyroantimonate-osmium (PAO) reaction indicated the selective binding of pyroantimonate to certain cations (calcium, magnesium, and possibly sodium) associated with the plasma membrane of neutrophilic leukocytes and their developmental forms. Other leukocytes and their precursors did not exhibit plasma membrane PAO reactivity. The extent of surface binding was related to cell maturity, with maximal labeling evident in the mid and late promyelocytes; decreased binding occurred with subsequent maturation while myeloblasts were nonreactive. This study was initiated to ascertain if histochemical surface modifications of neutrophilic cells occur in certain myeloproliferative disorders. In this regard, we have been able to demonstrate a distinctive defect in the plasma membrane PAO binding characteristics of the leukemic cells in chronic myelocytic leukemia (CML). Limited binding of pyroantimonate to the plasma membrane of the leukemic cell series in four patients with CML contrasted with that of the normal granulocytic cell series and the neutrophilic cells seen in myelomonocytic leukemia (two patients), myelofibrosis (one patient), and acute myelocytic leukemia (three patients). Comparison of surface PAO reactivity of neutrophilic cells in all stages of maturation in two patients with CML in blast crisis revealed that, in the patient with 30% circulating blast cells, PAO reactivity was identical to that noted in CML, while in the patient with 80% circulating blast forms, the PAO reactivity of the maturing neutrophilic cells more nearly resembled that observed in neutrophilic cells from normal individuals. Many neutrophilic cells from patients with myelofibrosis and myelomonocytic leukemia and from one patient in severe blast crisis had large surface deposits of pyroantimonate considered to reflect increased membrane-associated reactive cation.     

Polymorphonuclear leukocyte heterogeneity in neonates and adults

We have used a mouse monoclonal antibody (31D8) to determine whether differences in neutrophil (PMN) subpopulations might help explain decreased PMN chemotaxis in neonates compared with that of adults. 31D8 has been shown to bind heterogeneously to adult PMNs. Approximately 80% of the PMNs that strongly bind 31D8 (31D8 "bright") are the same cells that depolarize and migrate chemotactically when stimulated with the chemoattractant N-formyl-methionylleucylphenylalanine, while the 20% that weakly bind 31D8 fail to similarly respond. All neonatal PMNs bound 31D8 heterogeneously. There was a smaller population of 31D8 "bright" cells in neonates at birth (76% +/- 6%, n = 45) compared with that of neonates at three to 15 days of age (82% +/- 5%, n = 10, P less than 0.002) and both were smaller than that of adults (88% +/- 4%, n = 45, P less than 0.001 and P less than 0.001). Neonatal cord PMNs, which traversed a micropore filter in a modified Boyden chemotaxis chamber in the presence of a chemoattractant, had an increased percentage of 31D8 "bright" cells (89% +/- 7%) than did PMNs which remained above the filter (82% +/- 7%, n = 10, P = 0.034). PMN chemotaxis was less in neonates at birth (32.7 +/- 4.5 micron) than at three to six days of age (36.8 +/- 11.3 micron) and both were decreased compared with that of adults (69.1 +/- 12.4 micron, P less than 0.001 and P less than 0.001). These findings indicate that decreased PMN chemotaxis in neonates may be due in part to a smaller PMN subpopulation of highly motile cells.     

Alteration in bone marrow adherent layer growth factor expression: a novel mechanism of chronic myelogenous leukemia progression

Philadelphia chromosome1 positive (Ph1) chronic myelogenous leukemia (CML) is characterized by metamorphosis of the chronic phase to blastic crisis. However, cellular events associated with this transition are poorly understood. To examine the possible participation of hematopoietic growth factors in this process, we studied growth factor expression in adherent layers of bone marrows derived from CML Ph1 patients in various stages of the disease. Interleukin-1 beta (IL-1 beta) and IL-6 mRNA were expressed in five of six patients, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in one of six patients with myeloid/undifferentiated blast crisis. In addition, leukemia inhibitory factor (LIF) expression was increased in four of six patients with myeloid/undifferentiated blast crisis phase of the disease. IL-1 beta was also detected in bone marrow adherent layer conditioned medium from two of these patients. These results were in sharp contrast to the lack of detectable levels of uninduced IL-1 beta, IL-6, and GM-CSF mRNA, in samples derived from 4 patients in lymphoid blastic crisis, 3 in accelerated, and 11 in chronic phases of the disease, or from normal controls. The possibility of a paracrine loop formation, whereby the adherent layers representing the bone marrow stroma are induced to express hematopoietic growth factors, was supported by our finding IL-1 beta mRNA expression in the leukemic blast cells in three of four studied patients in blast crisis and IL-1 beta protein production in seven of eight patients studied. Finally, coculturing CML blast crisis cells onto pre-established adherent layers induced the expression of both IL-1 beta and IL-6 genes. From this preliminary study, it appears that abnormal expression of growth factors is a common event with CML Ph1 progression. We hypothesize that IL-1 beta generated by the transformed malignant clone stimulates the marrow stroma to produce various growth factors, and that this process may play a role in disease progression.     

Proliferation and Differentiation in Diffusion Chambers of Marrow,Blood and Spleen Cells from Patients with Chronic Myeloid Leukaemia during Chronic Phase and Blastic Transformation

The proliferative and differentiating capacity was compared between immature normal marrow cells and marrow, blood or spleen cells from patients with chronic myeloid leukaemia (CML) in chronic and blastic phases. Low density cells highly enriched in myeloblasts and promyelocytes were cultured in diffusion chambers (DC) and implanted into the peritoneal cavity of mice pretreasted with cyclophosphamide. In CML of chronic phase cell production was higher than normal with the exception of spleen cells. Total cell production was lower in blastic phase than in CML chronic phase. The [³H]-TdR labelling index of myeloblasts of blastic phase CML increased considerably upon implantation in DC consistent with re-entry into active proliferation. Immature normal cells give rise mostly to macrophages while the corresponding CML cells of chronic phase give a much higher PMN production with peaks after 12–18 d. Also in CML of blastic crisis the blasts differentiate into mature PMNs, but the maturation time is shortened with peaks of PMNs after 5–10 d. DC cultures of spleen cells from patients with CML showed a less differentiating capacity with a very low PMN production compared to cultures of marrow or blood cells. Our results indicate intrinsic differences in growth and maturation capacity between normal immature granulopoietic cells and cells from patients with CML of chronic phase or blastic crisis. The results may also indicate intrinsic differences between spleen, blood or marrow cells in CML.     

Imatinib induces hematologic and cytogenetic responses in patients with chronic myelogenous leukemia in myeloid blast crisis: results of a phase II study

Blast crisis is the most advanced stage of chronic myelogenous leukemia (CML) and is highly refractory to therapy. CML is caused by expression of the chimeric BCR-ABL tyrosine kinase oncogene, the product of the t(9;22) Philadelphia translocation. Imatinib (Glivec, formerly STI571) is a rationally developed, orally administered inhibitor of the Bcr-Abl tyrosine kinase. A total of 260 patients with CML were enrolled in a phase II trial, of whom 229 had a confirmed diagnosis of CML in blast crisis. Patients were treated with imatinib in daily oral doses of 400 mg or 600 mg. Imatinib induced hematologic responses in 52% of patients and sustained hematologic responses lasting at least 4 weeks in 31% of patients, including complete hematologic responses in 8%. For patients with a sustained response, the estimated median response duration was 10 months. Imatinib induced major cytogenetic responses in 16% of patients, with 7% of the responses being complete. Median survival time was 6.9 months. Nonhematologic adverse reactions were frequent but generally mild or moderate. Episodes of severe cytopenia were also frequent and were attributable to the underlying condition and treatment with imatinib. Drug-related adverse events led to discontinuation of therapy in 5% of patients, most often because of cytopenia, skin disorders, or gastrointestinal reactions. These results demonstrate that imatinib has substantial activity and a favorable safety profile when used as a single agent in patients with CML in blast crisis. Additional clinical studies are warranted to explore the efficacy and feasibility of imatinib used in combination with other antileukemic drugs.     

Genomic instability of microsatellite repeats and its association with the evolution of chronic myelogenous leukemia [see comments]

Tumorigenesis has been shown to proceed through a series of genetic alterations involving protooncogenes and tumor-suppressor genes. Investigation of genomic instability of microsatellites has indicated a new mechanism for human carcinogenesis in hereditary nonpolyposis colorectal cancer and sporadic cancer and this instability has been shown to be related to inherited predisposition to cancer. This study was conducted to determine whether such microsatellite instability is associated with the evolution of chronic myelogenous leukemia (CML) to the blast crisis. Nineteen CML patients clinically progressing from the chronic phase to accelerated phase or blast crisis and 20 other patients in the CML chronic phase were studied. By polymerase chain reaction assay, DNAs for genomic instability in five separate microsatellites in chromosome arms 5q (Mfd27), 17p (Mfd41), 18q (DCC), 3p (CI3-9), and 8p (LPL) were examined. Differences in unrelated microsatellites of chronic and blastic phase DNAs in 14 of 19 patients (73.7%) were demonstrated. Somatic instability in five microsatellites, Mfd27, Mfd41, DCC, CI3-9, and LPL, was detected in 2 of 19 (10.5%), 8 of 19 (42.1%), 11 of 19 (57.9%), 4 of 17 (23.5%), and 4 of 17 (23.5%) cases. In 10 of 19 cases (52.6%), genetic instability in at least two of five microsatellites was observed and was categorized as replication error (RER+) phenotype. CML evolution cases with myeloid, lymphoid, and mixed phenotypes and the blast crisis and accelerated phase showed somatic instability in a number of microsatellites. No alterations in leukemic cells at the chronic phase could be detected in any microsatellites. These data indicate instability of microsatellites (RER+) but not familial predisposition to possibly be a late genetic event in the evolution of CML to blast crisis. In the microsatellite of the DCC gene, complicated alterations in band patterns caused by instability as well as loss of heterozygosity (LOH) were observed in 13 of 19 cases (68.4%): instability in 9 cases, instability plus LOH in 2 cases, and only LOH in 2 cases. These highly frequent alterations in microsatellites, including instability and LOH, suggesting that secondary events due possibly to loss of fidelity in replication and repair machinery may be significantly associated with CML evolution.     

The role of alternative splicing patterns of BCR/ABL transcripts in the generation of the blast crisis of chronic myeloid leukaemia

Three major types of mRNA can be expressed as a result of the Philadelphia translocation, dependent on the position of the break within the BCR gene on chromosome 22. In addition, alternative splicing of the mRNA transcribed from the BCR/ABL fusion gene has been reported and it has been suggested that this may play a role in the generation of the acute phase of Philadelphia positive chronic myeloid leukaemia (CML). We have examined the fusion RNA present in 24 cases of chronic phase CML and 21 cases of patients with CML in blast crisis using the polymerase chain reaction. In no case was it possible to detect the presence of the e1a2 junction which encodes the p190 hybrid protein product. We conclude that the acquisition of the p190 does not play a significant role in the generation of the blast crisis of CML. Neither could we detect a significant difference in the number of cases which simultaneously express both b2a2 and b3a2 junction products in samples isolated from chronic phase and blast crisis. In the series analysed by ethidium bromide stained gels, there was, however, an increase in the percentage of cases expressing the b3a2 junction in the mononuclear cells of blast crisis patients as compared to the white blood cells of patients in chronic phase.     

Myeloid/natural killer cell precursor blast crisis of chronic myelogenous leukemia with two Philadelphia (Ph-1) chromosomes

We report on a 30-year-old patient with blast crisis of a chronic myelogenous leukemia (CML) that shows immunophenotypic features similar to those of the myeloid/natural killer (NK) cell precursor leukemia previously described. Expression of CD13/CD33/CD65 as well as MPO+/LF- blasts was classified as a myelogenous blast crisis of a CML. In addition, the blasts were positive for CD7/CD56. Other lymphoid markers were not expressed. Cytogenetic and molecular cytogenetic examinations showed two Philadelphia (Ph-1) chromosomes and a trisomy 8. Similar to expression of the myeloid/NK cell precursor phenotype in acute myelogenous leukemia (AML), it is possible to exhibit this phenotype in Ph-1-positive CML. Only one case report of myeloid/NK precursor phenotype blast crisis of CML was found in the literature. Therefore, it is not clear whether this phenotype is a distinct biologic and clinical disease entity of CML, as is the case in the respective AML phenotype.