Search

A human myeloid leukemia cell line, KBM-7, was developed from a patient in the blastic phase of chronic myeloid leukemia (CML). We characterized its morphology, immunophenotype, cytogenetics, and proliferative capacity. Developed in the absence of exogenous lymphokines, KBM-7 in vitro cloning capacity actually decreased when colony-stimulating factors were added. The cells had an aberrant immature myeloid phenotype, a doubling time of 22 h in suspension cultures and a high cloning efficiency in semisolid system (24 +/- 3)%. Early passages contained one near-haploid (predominant) and one hyperdiploid stem line. Gradually the hyperdiploid stem line became predominant, reaching an average of 49 chromosomes per cell. Cells from passage 89 had two Philadelphia chromosomes [t(9;22)(q34;q11)] and lacked normal copies of chromosomes 9 and 22. Detailed molecular characterization of the breakpoint in the t(9;22)(q34;q11) revealed that KBM-7 had the BCR 2/ABL II splice junction. The cells had high protein kinase (p210BCR-ABL) activity and carried two identified variants of an ABL-BCR message. There was no evidence that normal BCR or c-ABL messages were expressed, assessed with the reverse-transcriptase polymerase chain reaction. When KBM-7 cells were heterotransplanted into nude mice without immunosuppressive pretreatment, one of three mice injected with 1 x 10(7) cells and all mice injected with 1 x 10(8) cells developed slowly growing granulocytic sarcomas within 6-8 weeks. These tumors were locally invasive but did not metastasize. We conclude that the KBM-7 cell line will be of value for investigating molecular events underlying neoplastic transformation in CML, in particular for studying the effects of BCR-ABL and ABL-BCR on the proliferation of CML cells in the absence of normal BCR and c-ABL messages.

Interferon-alpha produces a complete hematologic and cytogenetic remission in approximately 20% of patients with chronic myelogenous leukemia (CML). In this study, we applied fluorescent in situ hybridization (FISH) methodology to examine the possibility that a low level of proliferating Philadelphia-chromosome-positive (Ph+) cells may be present in interferon-treated CML patients who have achieved complete cytogenetic remission (as defined by the absence of Ph chromosome in 20-25 metaphases analyzed). Ten such patients in remission for 6-35 months were studied by this technique, in which a chromosome-22-specific DNA painting probe was used to detect leukemic cells with the characteristic 9;22 chromosomal translocation. In six of the 10 patients (60%), 3-9% Ph+ metaphases were detected. No Ph+ cells were observed in nine control individuals. Thus, this study demonstrates that FISH technology is more sensitive than conventional cytogenetic analysis for the detection of minimal residual disease in CML.

Bone marrow samples collected from acute myeloblastic leukemia (AML) patients in complete clinical and hematological remission were studied for the persistence of cytogenetic abnormalities. AML patients from the three favorable cytogenetic categories [inv 16, t(8;21) and t(15;17)] and patients from the unfavorable cytogenetic categories (+8, -5, -7 and Philadelphia-positive) were studied. Seventy-one patients had evaluable metaphase spreads in remission marrows and 20 (28%) had one or more abnormal metaphases identical to that present in the pretreatment marrow. All 20 of these patients relapsed within 78 weeks, thus there were no false positive studies. Fifty-one patients had only diploid metaphases in their complete remission marrow, 25 relapsed, and 21 remained in continuous complete remission. Thus there was a 49% false negative rate of this study. These data indicate that the failure to detect residual chromosomally abnormal cells in the bone marrow does not guarantee continuous complete remission. Cytogenetic study was most useful in the favorable cytogenetic groups and least useful in the unfavorable groups. The persistence of normal metaphases in pretreatment marrows did not affect outcome or risk of recurrence. Twenty-five of 34 evaluable patients who relapsed after remission had either the identical cytogenetic abnormality present in the pretreatment marrow or showed the identical abnormality with additional chromosomal changes. Thus study indicates that cytogenetic examinations of complete remission bone marrow samples in patients with AML provides an objective method for detecting residual leukemia, and identifies patients with a potential for prolonged disease-free survival.

The retinoic acid receptor-alpha (RAR-alpha) gene was previously localized to chromosome 17q21, a region close to the t(15;17) (q22;q21) abnormality in acute promyelocytic leukemia (APL). We used the RAR-alpha gene as a probe and found that eight of nine APL patient samples with t(15;17) (q22;q21) showed rearranged bands. A tenth APL patient was diploid and demonstrated no rearrangement. One patient who had rearrangement as an acute leukemia did not have rearrangement in remission. The results obtained from intron/exon mapping of the RAR-alpha gene demonstrated that breakpoints of seven of the eight patients occurred within intron 1. Northern blot analysis of leukemic samples indicated the expression of two RAR-alpha mRNA of 2.7 and 3.7 kb. However, two additional mRNA of 4.1 and 3.2 kb were found in an APL patient. We conclude that the RAR-alpha gene is directly involved in the t(15;17) translocation in APL and may transcribe aberrant messages.

The level of myeloperoxidase (MPO) mRNA is reduced significantly after HL-60 induced differentiation with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). We examined the chromatin structural changes of the MPO gene during TPA induction. Before TPA induction about nine DNase I hypersensitive sites (HS) were found on the 5' upstream and at various intron regions of the MPO gene. A new HS was found on intron 8 within 4 h of induction; its appearance preceded down regulation of the MPO gene. At the same time DNase I HS found in 0.3 and 1-1.5 kb upstream of the MPO CAP site, were significantly reduced or disappeared after TPA induction. These chromatin structural changes could be closely linked to the mechanism which regulates the MPO gene expression.

Northern blot analysis of RNA isolated from HL-60 cells before and after differentiation induction by TPA and DMSO showed that four MPO mRNA species (3.3, 3.1, 2.7, and 2.5 kb, respectively designated alpha 1, beta 1, alpha 2, and beta 2) are expressed in HL-60 cells. However, alpha 2 and beta 2 lack part of the 3' end sequence due to different polyadenylation sites. The steady state levels of alpha 2 and beta 2 MPO mRNA increase significantly after 1 hr of induction, while all four MPO mRNA species decrease dramatically after 10 hr of induction. Our results demonstrate that MPO gene expression is developmentally and differentially regulated. Northern blot analysis of RNA isolated from blast samples of acute myelogenous leukemia (M0-M5) and chronic lymphocytic leukemia (CLL) patients indicate that four MPO mRNA species are expressed in M1-M4 but are undetectable in M5 and CLL. Primer extension and S1 nuclease protection analysis of the MPO mRNA revealed a single transcription initiation site for the MPO gene.

The human myeloperoxidase (MPO) gene has recently been cloned in our laboratory. Southern blot hybridization of our MPO cDNA to DNA from a somatic cell hybrid clone panel revealed that the MPO cosegregated with human chromosome 17. In situ hybridization mapped the MPO gene to chromosome 17q22-24. Although this location is close to the translocation breakpoint which occurs in acute promyelocytic leukemia (APL), t(15;17)(q22;q21-22), Southern blot hybridization with different restriction-digested genomic DNA samples from four APL patients did not reveal MPO gene rearrangement. However, RNA dot-blot hybridization showed that APL patients with the translocation expressed high levels of MPO mRNA. This observation raises the possibility that the high levels of MPO gene expression in APL could be due to the arrest of leukemic cells at a specific stage of differentiation or a consequence of the translocation.

An analysis was conducted of clinical and laboratory variables associated with response to remission induction therapy and remission duration in 440 patients with acute myelogenous leukemia treated between 1975 and 1983. The complete remission rate was 259/440 (59%). Specific cytogenetic abnormalities such as t(8;21), t(15;17), and inv16 were found to be favorable for response to therapy and/or remission duration, whereas those with a normal (diploid) karyotype had an intermediate prognosis. All other karyotypic abnormalities were associated with lower response rates and short complete remission durations. The karyotypes were classified as favorable, intermediate, and unfavorable groups for response and remission duration after allowing for all the other observed clinical and laboratory values related to prognosis. The cytogenetic classification was prospectively validated in an independent test group of 130 patients treated between 1983 and 1986 and showed a consistent relationship to response and remission duration. Logistic regression and proportional hazard models developed from the initial 440 patients were prospectively evaluated in the test group of 130 patients. Clear stratifications of patients into good, intermediate, and poor risk groups were obtained in the prospective tests. The karyotype of the leukemia cells is an independent prognostic variable for response and remission duration in acute myelogenous leukemia.

Leukemic blasts from 40 consecutively admitted adults with untreated acute lymphoblastic leukemia (ALL) were examined for myeloid surface antigen expression. Of these, 14 (35%) were reactive with one or more myeloid monoclonal antibodies. Each example of myeloid surface antigen-positive (My+ ALL) met the standard morphologic and cytochemical criteria for ALL. In addition, none of the 13 samples studied for ultrastructural evidence of myeloperoxidase met the criteria for acute myelocytic leukemia (AML). All patient samples reacted with lymphoid monoclonal antibodies: CD10+ (8 patients), CD19+ CD10- (2 patients), T cell+ (2 patients), and T cell+ CD10+ (2 patients). Coexpression of myeloid and lymphoid determinants was established by two-color immunofluorescence studies using flow cytometry in five of five samples analyzed. Cytogenetic abnormalities that have been associated with myeloid and mixed leukemias were common, including t(9;22), 7q-, abnormalities of 11q with or without a translocation, 20q-, and -5. Blasts from seven patients were studied at the molecular level. Immunoglobulin heavy chain gene rearrangements were detected in five of five samples with B cell+ T cell- phenotypes. One sample that was T cell+ CD10+ was germline for the immunoglobulin heavy chain and the T cell receptor gamma- and beta-chain genes. The other patient with T cell+ CD10+ blasts relapsed with AML following allogeneic bone marrow transplantation. The leukemia cells at the time of diagnosis and the cells at relapse demonstrated similar cytogenetics and the same immunoglobulin gene rearrangement, suggesting a clonal relationship. As a group, the My+ ALL patients had a significantly decreased complete remission rate when compared to My- ALL patients. Further studies at the molecular level will be required to determine the significance of karyotype abnormalities in My+ ALL.