Interstitial insertion of varying amounts of ABL-containing genetic material into chromosome 22 in Ph-negative CML

We studied the cells from three selected patients with Ph-chromosome-negative chronic myeloid leukemia (CML) by Southern blotting, polymerase chain reaction, and in situ hybridization of informative probes to metaphase chromosomes. All three patients had rearrangement of M-BCR sequences in the BCR gene and expression of one or other of the mRNA species characteristic of Ph-positive CML. Leukemic metaphases studied after trypsin-Giemsa banding were indistinguishable from normal. The ABL probe localized both to chromosome 9 and 22 in each case. A probe containing 3' M-BCR sequences localized only to chromosome 22, and not to chromosome 9 as would be expected in Ph-positive CML. Two new probes that recognize different polymorphic regions distal to the ABL gene on chromosome 9 in normal subjects localized exclusively to chromosome 9 in two patients and to both chromosomes 9 and 22 in one patient. These results show that Ph-negative CML with BCR rearrangement is associated with insertion of a variable quantity of chromosome 9 derived material into chromosome 22q11; there is no evidence for reciprocal translocation of material from chromosome 22 to chromosome 9.

Slow evolution of chronic myeloid leukaemia relapsing after BMT with T-cell depleted donor marrow

Thirty-three patients with Philadelphia positive (Ph+) chronic myeloid leukaemia (CML) treated in chronic phase by bone marrow transplantation (BMT) with T-cell depleted HLA-identical sibling marrow were evaluable for relapse at a median follow up of 41 months (range 16-59 months). Twenty-six (78%) had Ph+ marrow metaphases demonstrated at some time post BMT. The subsequent pattern of disease was variable. In 15 of these cases haematological relapse occurred within 24 months of BMT. Four patients proceeded to haematological relapse more slowly. Seven patients had only cytogenetic evidence of relapse. Of the 19 patients with haematological relapse, five received second transplants and two survive; 13 of the other 14 survive in chronic phase at median times from allografting and from recognition of haematological relapse of 41 months (range 25-59 months) and 18 months (range 5-36 months) respectively. For these 13 patients disease progression after relapse seems to be relatively indolent. In the four patients we could study, blood lymphocytes were almost all of donor origin. We suggest that even in patients with cytogenetic or haematological evidence of relapse after T-cell depleted BMT, leukaemic cell proliferation may still be restrained to some extent by a graft-versus-leukaemia effect mediated by donor-derived lymphoid cells.

Cytogenetic and molecular studies in patients with chronic myeloid leukemia and variant Philadelphia translocations

Out of 105 Philadelphia (Ph) positive chronic myeloid leukemia patients analyzed, six (5.7%) carried a variant Ph translocation, namely t(6;9;9;10;22)(q24;p13;q34;p15;q11); t(9;13;22)(q34;q21;q11);der(2)(2pter----2q31::9q21---- 9q34::22q11----22qter) and der(9)t(2;9) (9pter----9q21::2q31----2qter);t(7;9;22)(q11;q34 ;q11), 14q + ;t(7;9;22)(q35;q34;q11), and t(9;11;22) (q34;q13;q11), respectively. Five of these patients were analyzed with Southern blotting. Three of them showed an atypical molecular pattern; namely, the patient with t(9;13;22) showed no rearrangement in the breakpoint cluster region (bcr), the patient with t(7;9;22)(q35;q34;q11) showed a 3' deletion, and the patient with t(7;9;22), 14q + showed a bcr rearrangement 3' to the exon 4 of the M-BCR. Chromosome in situ hybridization studies demonstrated that in patient one, a two-step translocation occurred: the first step moved the 3' bcr from chromosome 22 to chromosome 9, and the second moved the terminal part of 22q, carrying the c-sis protooncogene, to 10p. Variant Ph translocations appear to be associated with atypical molecular breakpoints.

Autografting for patients with chronic myeloid leukaemia in chronic phase: peripheral blood stem cells may have a finite capacity for maintaining haemopoiesis

We treated 14 patients with Ph-chromosome-positive chronic myeloid leukaemia still in chronic phase by autografting with blood-derived haemopoietic stem cells. Eleven patients were autografted electively after cytoreductive treatment with busulphan (16 mg/kg) and melphalan (60 mg/m2) and three were autografted after marrow cells from HLA-identical sibling donors had failed to engraft. In 13 patients haemopoiesis recovered; one failed to engraft and died 114 d after autografting. Two other patients became pancytopenic and received further stem cell transfusions at 3 and 40 months respectively after first autografting. One patient entered lymphoid transformation and died 14 months after autografting. Twelve patients survive at a median of 41 months (range 24-53) after autografting. Nine of the survivors have required further chemotherapy after autografting and four of the nine were electively autografted on a second occasion. Three patients surviving after autografting for 28, 43 and 53 months respectively have not required further chemotherapy. In two of these patients haemopoiesis is now predominantly Ph-negative. We conclude that autografting in chronic phase might prolong survival in some cases by reducing the size of the leukaemic stem cell population. The fact that initially successful grafts failed in two patients suggests that blood-derived stem cells may have a finite potential for self-replication.

Molecular analysis of Philadelphia positive essential thrombocythemia

Seven patients with Philadelphia (Ph) chromosome positive essential thrombocythemia (ET) were investigated for the presence of a rearrangement within the major breakpoint cluster region (M-bcr) using the Southern blot technique and, in six cases, for the presence of the hybrid bcr-abl mRNA using the polymerase chain reaction (PCR). The molecular studies showed rearrangement of M-bcr in all cases; there was evidence of the b2a2 mRNA junction in one case and of b3a2 junction in five cases. These findings are identical to what might have been expected in Ph-positive chronic myeloid leukemia. These features may explain the poor prognosis of Ph-positive ET in comparison with cytogenetically normal cases. Conversely, the differences in clinical presentation may be due to other genetic changes.

Rearrangement of the breakpoint cluster region and expression of P210 BCR-ABL in a "masked" Philadelphia chromosome-positive acute myeloid leukemia

The Philadelphia (Ph) translocation t(9;22)(q34;q11) occurs frequently in chronic myeloid leukemia (CML) but is less common in acute lymphoblastic leukemia (ALL) and rare in acute myeloid leukemia (AML). In most cases of CML and some cases of Ph+ ALL the protooncogene ABL from 9q34 is translocated to the breakpoint cluster region (bcr) of the BCR gene at 22q11 to form a chimeric gene encoding a novel 210-kd protein (P210 BCR-ABL) with enhanced tyrosine kinase activity. In other patients with Ph+ ALL and Ph+ AML, the breakpoint probably occurs in the first intron of the BCR gene; this results in a smaller chimeric gene which encodes a P190 BCR-ABL. We studied a patient with AML (FAB M6) arising de novo who had a "masked" Ph chromosome in association with extensive karyotypic changes. The leukemic cells initially showed rearrangement of the bcr, presence of a hybrid mRNA, and expression of the P210 BCR-ABL. These changes were absent in remission. These results support the concept that the BCR-ABL chimeric gene plays a crucial role in leukemogenesis but suggest that factors other than the position of the breakpoint in the BCR gene determine the lineage of the target cell for malignant transformation.

The genomic breakpoint in a patient with Philadelphia-positive acute leukemia is 5' of the breakpoint cluster region

We report a case of acute leukemia in which studies at presentation showed both myeloid and lymphoid cell surface markers. At relapse membrane markers studies were consistent with a leukemia of B-lymphoid lineage. However, immunoglobulin (Ig) and T cell receptor (TCR) beta chain genes were both found in a rearranged configuration. The majority of metaphases from the leukemic cells at presentation showed the Philadelphia chromosome, t(9;22)(q34;q11), whereas a minority were normal. At relapse both Ph-positive and -negative metaphases were still present in the bone marrow but some of the Ph-negative metaphases had acquired an additional chromosome #19 [47,XY, + 19]. Southern analysis of DNA from leukemic bone marrow cells at diagnosis showed no rearrangement of breakpoint cluster region (bcr). There was no bcr-abl chimeric mRNA typical of Ph-positive chronic myeloid leukemia (CML). However, the cells expressed an abl-related protein of Mr 190 kd with enhanced tyrosine kinase activity. Leukemic cell metaphases were studied by the technique of in situ hybridization with probes for C-lambda, sis, abl, and 5' bcr. The c-abl probe mapped to chromosome 22q11 in Ph-positive metaphases. The 5' bcr probe mapped to 9q+ in the Ph-positive metaphases and the C-lambda gene mapped to the Ph chromosome. Thus, the genomic breakpoint in this patient must lie upstream of the BCR defined by study of Ph-positive CML and downstream of the C-lambda gene locus. We speculate that the Ph-negative cells in this patient may represent a leukemic proliferation susceptible to acquisition of specific chromosomal changes.

Cytogenetic events after bone marrow transplantation for chronic myeloid leukemia in chronic phase

Forty-eight patients treated by allogeneic bone marrow transplantation (BMT) for Philadelphia (Ph) chromosome-positive chronic myeloid leukemia in chronic phase had serial cytogenetic studies of marrow performed at intervals after transplant. Twenty patients received marrow cells from donors of opposite sex. Ph+ marrow metaphases were identified in 24 of 48 (50%) of patients after BMT; they were first seen early (within 1 year) in 16 cases and late (greater than 1 year after BMT) in eight cases. Ph-positivity after BMT occurred more commonly in recipients of T-depleted than nondepleted marrow (19 of 28 v 5 of 20). In 4 cases the Ph+ metaphases were found only transiently after BMT; in 11 cases the Ph+ metaphases have persisted but hematologic relapse has not ensued; in 9 cases the finding of Ph+ metaphases coincided with or preceded hematologic relapse. Chromosomes in cells of donor origin had morphological abnormalities in two cases. No relapses were identified in cells of donor origin. Our data suggest that the relationship between cells of recipient and donor origin is complex: cure of leukemia may depend on factors that operate for some months or years after BMT.

Do oncogenes determine clinical features in chronic myeloid leukaemia?

Oncogene abnormalities are thought to have a central role in some human malignant disorders, particularly Burkitt leukaemia/lymphoma and chronic myeloid leukaemia (CML). However, the extent to which specific oncogene changes determine the clinical features of these disorders is unknown. This question was studied in two groups of patients with CML negative for the Philadelphia (Ph) chromosome; one group showed clinical features typical of Ph-positive CML and the other group lacked such features. Molecular findings were compared with those of Ph-positive CML. In all ten patients there was evidence for rearrangement of the bcr (breakpoint cluster region) gene. In the four cases studied the c-abl proto-oncogene was translocated to chromosome 22 and in five cases there was transcription of a chimeric bcr-abl mRNA. Thus, the molecular abnormality is the same in both groups of Ph-negative CML and identical to that in Ph-positive CML. Factors other than the bcr/c-abl rearrangement must underlie the clinical heterogeneity of CML.

Establishment and characterization of three new malignant lymphoid cell lines

We have established 3 new EBV-negative cell lines, designated Sc-1, Ri-1 and Ci-1, from patients with B-cell lymphoma/leukemia. We characterized them by cytogenetics and by study of surface membrane antigens with a panel of monoclonal antibodies (MAbs), surface and cytoplasmic immunoglobulin (Ig) expression and Ig heavy- and light-chain genes. All 3 lines had a 14q+ abnormality. Ri-1 also had translocations involving chromosomes 2, 8 and 18. Ci-1 also had abnormalities involving chromosomes 2, 8 and 22 and its karyotype was 46, XX, t(2;8), t(14;22). The t(2;8) had the same breakpoints as those reported in some cases of Burkitt's lymphoma. We also studied a classical Ph1-positive cell line previously established by Pegoraro et al. (1983) and designated BV173. The phenotypes of these 4 lines based on Ig expression and marker studies correlated well with their respective genotypes. Our results are in keeping with the notion that leukaemic cell populations are clonal expansions of cells "frozen" at a particular stage in their differentiation. Specifically, BV173 cells are at an early stage of B-cell differentiation, Ri-1 and Ci-1 cells are at intermediate stages and Sc-1 cells are at a relatively late stage in the B-cell lineage.

Complete remission after autografting for chronic myeloid leukaemia

A previously untreated 31-yr old female with Ph-positive chronic myeloid leukaemia (CML) received busulphan and melphalan at high dosage followed by an autograft of peripheral blood stem cells collected 4 weeks earlier. Though recovering haemopoiesis was at first mainly Ph-positive, Ph-negative haemopoiesis predominated at 12 months and has persisted until the most recent study (24 months post-autograft). Her haemopoietic cells now show no rearrangement of the bcr gene, unlike the cells collected at diagnosis. Autografting carried out soon after diagnosis could be valuable for obtaining cytogenetic remissions in other patients with CML.

Rearrangement of the bcr gene in Philadelphia chromosome-negative chronic myeloid leukemia

We studied the clinical, hematologic, cytogenetic, and molecular biologic features of seven patients with Philadelphia (Ph1) chromosome-negative chronic myeloid leukemia (CML). In five cases the hematologic findings were indistinguishable from those of patients with classical Ph1-positive disease. Myeloid cells were studied by chromosome-banding techniques. One patient had a masked Ph1 chromosome (with translocation t(4;9;22)), one had a deletion involving chromosome 16, and one had a small minority population of 22q- cells without 9q+ but otherwise normal metaphases; metaphases from the other four patients were entirely normal. DNA prepared from the myeloid cells was digested with the restriction enzymes EcoRI, HindIII, BamHI and BglII. Southern analysis using a 0.6-kb fragment of the breakpoint cluster region (bcr) gene showed the presence in each patient's DNA of a germline fragment together with a rearranged fragment or fragments with at least one of the restriction enzymes. We conclude that genomic changes in the bcr gene characteristic of CML can be present in the absence of a Ph1 chromosome.

Philadelphia-positive metaphases in the marrow after bone marrow transplantation for chronic granulocytic leukemia

A 28-year-old man with Ph-positive chronic granulocytic leukemia (CGL) was treated by high-dose chemoradiotherapy and transplantation of marrow cells harvested from his HLA-identical brother. One year after bone marrow transplantation (BMT) examination of his marrow showed a minority population of Ph-positive cells; their proportion subsequently fell such that 2 years after transplant analysis of marrow cells showed only cytogenetically normal cells. The patient remains clinically normal with a persisting mild lymphocytosis but without hematological evidence of leukemia. We cannot in this patient distinguish between persisting leukemia that later could no longer be recognized and relapse of leukemia that is now suppressed, perhaps only temporarily. This case emphasizes the need for caution in interpreting chromosomal finding after BMT for CGL.

Correlation between chromosomal abnormalities and blast phenotype in the blast crisis of Ph-positive CGL

We carried out cytogenetic analysis in 23 patients with Ph-positive chronic granulocytic leukemia in blast crisis. In all cases the type of blast cell was characterized by cytochemistry, immunologic markers, and ultrastructural studies. Twelve cases were classified as myeloid transformation, six as lymphoid, two as mixed (lymphoid and myeloid), and two were unclassifiable. Duplication of Ph was the most frequent abnormality in the whole series. Trisomy 8, i(17q) and trisomy 19 were seen only in patients with myeloid blast crisis (53%, 30%, and 23%, respectively). Our findings suggest that the nature of additional chromosome abnormalities arising in blasts with features of myeloid differentiation are different from those in blasts showing lymphoid differentiation.