Biphenotypic leukemia: immunologic and morphologic evidence for a common lymphoid-myeloid progenitor in humans

Myeloid Antigen Expression in Childhood Acute Lymphoblastic Leukemia and Its Relevance for Clinical Outcome in Indonesian ALL-2006 Protocol

The frequency of acute lymphoblastic leukemia (ALL) patients expressing myeloid antigens on their ALL cells varies between 5 and 36% in several different studies. The clinical relevance of myeloid antigen expression in childhood ALL is controversial. In Indonesian patients, no data were present. Therefore, in Yogyakarta, Indonesia, we analyzed 239 ALL patients who were immunophenotyped including myeloid markers (CD13, CD33, CD117, and/or cMPO). Myeloid antigen expression was found in 25% of patients. Expression of myeloid antigen in B-lineage leukemia was 27%, and in T-lineage leukemia, it was 18% (P = 0.15). No association was found between myeloid antigen expression and clinical or biological features. In the whole cohort of patients we did not find a significant association between myeloid antigen expression and survival, although leukemia-free survival at 3 years was higher in the myeloid-negative patients (73% ± 6%) compared to myeloid-positive patients (67% ± 8%). Interestingly, in T-ALL patients, expression of myeloid antigens was an independent adverse prognostic factor (hazard ratio: 3.26, 95% CI: 1.06–9.98, P = 0.04). Kaplan-Meier analysis for event-free survival was also significant (log rank P = 0.03) in this subgroup. In conclusion, in the Indonesian ALL population, in particular, myeloid antigen-expressing T-ALL patients had a higher chance of having induction failure.

Very early onset of an acute myeloid leukemia in an adult patient with B-cell lymphoblastic leukemia

We report on a case of a 30-year-old male with acute B-lymphoblastic leukemia (B-ALL) with immunophenotype CD19(+), CD22(+), CD20(+), CD10(+), with aberrant expression of CD13 and CD117, and IgH gene rearrangements. Three months after treatment with GMALL-2003 and Ida/FLAG protocols bone marrow showed predominance of blasts with myeloid morphology and phenotype MPO(+), CD13(+), CD33(+), CD64(+), CD15(+), CD56(+), EVI-1 gene overexpression and lack of IgH rearrangements. The case is the first report of a very early emergence of myeloid leukemia during the induction treatment for B-ALL in an adult patient. Different pathogenetic mechanisms are discussed - clonal evolution or selection, lineage switch or development of a de novo or therapy-induced leukemia.

Novel insights into the pathogenesis of the Graffi murine leukemia retrovirus

The Graffi murine leukemia virus (MuLV) was isolated in 1954 by Arnold Graffi, who characterized it as a myeloid leukemia-inducing retrovirus. He and his team, however, soon observed the intriguing phenomenon of hematological diversification, which corresponded to a decrease of myeloid leukemias and an increase of other types of leukemias. Recently, we derived two different molecular clones corresponding to ecotropic nondefective genomes that were named GV-1.2 and GV-1.4. The induced leukemias were classified as myeloid based on morphological analysis of blood smears. In this study, we further characterized the two variants of the Graffi murine retrovirus, GV-1.2 and GV-1.4, in three different strains of mice. We show that the Graffi MuLV is a multipotent retrovirus capable of inducing both lymphoid (T- and B-cell) and nonlymphoid (myeloid, erythroid, megakaryocytic) leukemia. Many of these are very complex with concomitant expression of different hematopoietic lineages. Interestingly, a high percentage of megakaryocytic leukemias, a type of leukemia rarely observed with MuLVs, arise in the FVB/n strain of mice. The genetic backgrounds of the different strains of mice influence greatly the results. Furthermore, the enhancer region, different for GV-1.2 and GV-1.4, plays a pivotal role in the disease specificity: GV-1.2 induces more lymphoid leukemias, and GV-1.4 induces more nonlymphoid ones.

Two consecutive immunophenotypic switches in a child with immunogenotypically stable acute leukaemia

A 12-year-old girl presented with a CD33+ precursor B-acute lymphoblastic leukaemia (ALL) and seemed to respond well to ALL treatment. However, 2 weeks after diagnosis her leucocyte count rose rapidly with a predominance of myeloid blasts with M5b morphology and CD19+ myeloid immunophenotype. Acute myeloid leukaemia (AML) treatment was started and remission was achieved after one course of chemotherapy; the AML treatment was continued for 6 months. Two months after cessation of chemotherapy, the patient developed a bone marrow relapse, this time with an undifferentiated blast morphology and a precursor B immunophenotype. Molecular analysis of the immunoglobulin and T-cell receptor genes showed several clonal gene rearrangements at diagnosis: two IGH, two IGK and two TCRD gene rearrangements. All rearrangements were also detected during the AML phase of the disease, suggesting a phenotypic shift of the same leukaemia. At relapse, 8 months later, all rearrangements were preserved except for one TCRD (Vdelta2-Ddelta3) rearrangement. The first phenotypic shift in the genotypically stable leukaemia was remarkably fast. The most probable explanation for our observations is an oncogenic event in an undifferentiated haematopoietic progenitor clone, with a highly versatile phenotype.

Lineage switch in childhood leukemia with monosomy 7 and reverse of lineage switch in severe combined immunodeficient mice

Morphophenotypic lineage switches occur in a small percentage of those with acute leukemia, and the underlying mechanisms are not clear. In this study, we attempted to induce a lineage switch in acute myelocytic leukemia (AML) with monosomy 7, whose lineage had switched from acute T-lymphocytic leukemia (T-ALL) during chemotherapy, in severe combined immunodeficient (SCID) mice. Although the transplanted myeloid cells were engrafted in SCID mice without cytokine administration, T-ALL developed in SCID mice treated with recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. Analysis of the nucleotide sequences of the rearranged T-cell receptor gamma-chain (TCR-gamma) gene revealed that this lineage switch resulted from the selection of the T-lineage subclone in SCID mice, which had expanded at onset. In addition, we found that the T-lineage and myeloid cells belonged to the distinct subclones, which were different in TCR-gamma gene rearrangements, but were derived from a common clone with an identical N-ras gene mutation for both subclones. In in vitro cultures, only the myeloid subclone grew; the T-lineage subclone failed to grow even in the presence of recombinant human granulocyte-macrophage colony-stimulating factor or recombinant human interleukin 3. These results suggested that the initial diagnostic T-lymphoid subclone, whose growth was dependent on these cytokines and the hematopoietic microenvironment, emerged from a bipotential T-lymphoid/myeloid leukemic stem cell, and further genetic event(s) induced the myeloid subclone, which grew independently of these cytokines and the microenvironment.

Lineage switch in Philadelphia chromosome-positive acute lymphoblastic leukemia

BACKGROUND

An 8-year-old boy, initially diagnosed with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) (French-American-British [FAB]-L1), relapsed with Ph+ acute myelogenous leukemia (AML) (FAB-M2) 21 months after successful ALL treatment with standard therapy.

METHODS

The initial ALL presentation and subsequent AML relapse were analyzed by conventional morphologic, cytochemical, immunophenotypic, and cytogenetic studies.

RESULTS

Molecular analysis based on the polymerase chain reaction identified the presence of a bcr-I-abl fusion transcript at initial ALL presentation, the completion of ALL therapy, and AML relapse.

CONCLUSIONS

The cytogenetic and molecular results support a common clonal origin for this process. This is a case of lineage switch in a Ph+ acute leukemia. This case thus illustrates a manifestation of heterogeneous lineage differentiation among Ph+ acute leukemias.

Acute biphenotypic leukaemia: immunophenotypic and cytogenetic analysis

The incidence of acute biphenotypic leukaemia has ranged from less than 1% to almost 50% in various reports in the literature. This wide variability may be attributed to a number of reasons including lack of consistent diagnostic criteria, use of various panels of antibodies, and the failure to recognize the lack of lineage specificity of some of the antibodies used. The morphology, cytochemistry, immunophenotype and cytogenetics of acute biphenotypic leukaemias from our institution were studied. The diagnostic criteria took into consideration the morphology of the analysed cells, light scatter characteristics, and evaluation of antibody fluorescence histograms in determining whether the aberrant marker expression was arising from leukaemic blasts or differentiated bone marrow elements. Fifty-two of 746 cases (7%) fulfilled our criteria for acute biphenotypic leukaemias. These included 30 cases of acute lymphoblastic leukaemia (ALL) expressing myeloid antigens, 21 cases of acute myelogenous leukaemia (AML) expressing lymphoid markers, and one case of ALL expressing both B- and T-cell associated antigens. The acute biphenotypic leukaemia cases consisted of four major immunophenotypic subgroups: CD2+ AML (11), CD19+ AML (8), CD13 and/or CD33+ ALL (24), CD11b+ ALL (5) and others (4). Chromosomal analysis was carried out in 42/52 of the acute biphenotypic leukaemia cases; a clonal abnormality was found in 31 of these 42 cases. This study highlights the problems encountered in the diagnosis of acute biphenotypic leukaemia, some of which may be responsible for the wide variation in the reported incidence of this leukaemia. We suggest that the use of strict, uniform diagnostic criteria may help in establishing a more consistent approach towards diagnosis of this leukaemic entity. We also suggest that biphenotypic leukaemia is comprised of biologically different groups of leukaemia based on immunophenotypic and cytogenetic findings.

Myelomonocytic antigens are rarely expressed on B-lymphocytic leukemia cells

In the light of recent observations reporting that B-lymphocytic leukemia (B-CLL) cells may express a variety of myelomonocytic antigens, 28 patients with B-CLL and B-leukemic lymphocytic lymphoma were studied for the presence of these antigens using monoclonal antibodies to detect CD13, CD33, CD15 and CD14. Analysis of immunofluorescence (IF) was carried out by two procedures; one which employed the standard conventional method of gating used in our laboratory for flow cytometry, while the other procedure increased the sensitivity of the analysis, by moving the marker for IF to the left, so as to widen the gate to include more cells with low IF. Using the conventional methodology, the mean proportion of cells considered positive was less than 3% for any of the 4 markers studied. In only a few patients were 5% or more of the B-CLL cells positive for some of the markers studied (3 patients with 6.2-11.3% CD13+; 2 with 6.0-9.6% CD14+, and one with 11.8% CD15+ cells). No case had more than 2.5% + CD33+ cells. The second procedure with a wider gate to enhance sensitivity for less positive cells, increased the number of positive cells for any of the markers in only 4 patients. These results are contradictory to others reported recently, and some of the possible causes for this discrepancy are discussed. It is suggested that more useful data may be obtained if the level of staining intensity and patterns of positive staining are documented in the future.

Incidence of secondary acute myelogenous leukemia after treatment of childhood acute lymphoblastic leukemia

BACKGROUND

Recent reports of secondary acute myelogenous leukemia (AML) occurring in children previously treated for acute lymphoblastic leukemia (ALL) prompted a review of patients with ALL treated at the Dana Farber Cancer Institute consortium (DFCI) between 1973 and 1987. Seven hundred fifty-two of 779 children treated for ALL entered complete remission. The mean follow-up time for the 752 patients was 4.4 years. Two children had AML develop 12 and 13 months after the diagnosis of ALL, respectively.

METHODS

The estimated overall risk of secondary AML was calculated for the patient population as instances per 1000 patient-years of follow-up. This was compared with recent reported cases from another institution.

RESULTS

The estimated overall risk of secondary AML was 0.61 instances per 1000 patient-years of follow-up (95% confidence interval: 0.15, 4.4). The difference between the risk of 0.61 among DFCI patients versus previously reported risk of 5.8 among a differently treated group of patients with ALL was statistically significant (P = 0.0008). No epipodophyllotoxin was used in the patients in the DFCI consortium. In contrast, an epipodophyllotoxin was used in 12 of 13 previously reported patients who had secondary AML develop.

CONCLUSIONS

The authors concluded that the use of epipodophyllotoxins may be associated with an increased risk of having secondary AML develop in patients with ALL.

"Jumping translocation" in a 17-month-old child with mixed-lineage leukemia

A 17-month-old child with acute biphenotypic (pre B-ALL/myelomonocytic) leukemia is reported. Extensive cytogenetic analysis performed at various stages of the disease revealed a clonal evolution at the time of initial diagnosis with two types of abnormal clones, one with trisomy 22 and two other related clones with trisomy 22 plus partial trisomy of the long arm of chromosome 1 associated with the telomeric segment of either chromosome 20q or 21p. At the time of relapse the only abnormal clone involved trisomy 22 and partial trisomy of 1q, but this time in association with the telomeric segment of 14p. The unique feature of these translocations is discussed and the possibility of the correlation between the different chromosomal abnormalities and the expression of biphenotypic markers is raised.

Transformation of bilineal hybrid acute leukemia to acute lymphoid leukemia: a case report with serial analyses of cytogenetics and gene rearrangement

A 17-year-old male with bilineal hybrid acute leukemia is described. Two-color flow cytometric analysis of blast surface phenotype revealed that there were two groups of blasts which showed either CD 10+ CD 19+ CD 13- CD 33- or CD 10- CD 19- CD 13+ CD 33+, but not both. He developed a complete remission by treatment with vincristine, prednisolone, adriamycin, and L-asparaginase. After 8 months, however, leukemia relapsed and lymphoid blasts were dominant. Cytogenetic analysis at presentation showed 46,XY,t(3;9)(p21;p22), and at relapse it showed 46,XY,t(1;3;9)(1pter----1q32::3p25----3pter;3 qter----3p21::9p22----9pter; 9qter----9p22::3p21----3p25::1q32----1q ter),t(2;19)(p21;q13). Analysis of the heavy chain joining region at diagnosis showed three hybridizing bands, all rearranged, but at relapse only one rearranged band. Analysis of the constant region for the beta T-cell receptor gene (TCR beta) both at diagnosis and at relapse showed one rearranged and one germline band, suggesting that rearrangement of one allele of TCR beta of not only lymphoid but also myeloid blasts occurred. It is considered that the target cell of lymphoid leukemia cells and that of myeloid leukemia cells at diagnosis were the same, which differentiated to two lineages, and the clone which evolved from lymphoid lineage proliferated at relapse.

11q23 abnormalities in children with acute nonlymphocytic leukemia (M4-M5). Association with previous chemotherapy

Cytogenetic studies of 12 patients aged less than 14 years with acute nonlymphoblastic leukemia (ANLL) (M4-M5) showed structural abnormalities on chromosome 11 at band q23-q24 in five cases (41.8%). Four of these 12 patients had ANLL (M4-M5) after treatment with cytostatics for non-Hodgkin lymphoma in one case and for an acute lymphoblastic leukemia (ALL) in the other three. Three of these four cases had 11q23 abnormalities [one [one 46,XY,t(11;17)(q23;25); another 47,XY,+8,-15,del(11)(q23),+der(15)t(15;?)(p11;?); the third 47,XX,+8,t(3;17) (p11;q25),t(4;11)(q21;q23)] and one had a normal karyotype on being diagnosed ANLL (M4-M5). The notable increase of ANLL (M4-M5) in our patients who had received cytostatics as treatment for a previous neoplasia makes evaluation of our results timely in comparison with those of other groups who use these therapeutic protocols.

Undifferentiated acute leukemia and lineage infidelity (difficulties in classification and management)

The acute leukemias have been considered to represent a clonal expansion of a malignant transformed hematopoietic progenitor cell with adherence to either the myeloid or lymphoid lineage--"lineage fidelity." Lineage fidelity has been challenged by the demonstration of lineage switching or mixed-lineage leukemias. We describe a 7 year old male who presented with undifferentiated acute leukemia and nasopharyngeal and cervical masses. His blasts had the morphologic appearance of myeloblasts (FAB M1) and were positive solely for the myeloid antigen CD15. He entered a complete remission (CR) with acute nonlymphocytic leukemia therapy. At first relapse he had evidence of mixed-lineage leukemia with B-cell lymphoid and myeloid phenotypes. He again relapsed from a second CR with Burkitt-cell leukemia. Cytogenetic findings showed a consistent 14q+, 17p+ abnormality in the blasts and nasopharyngeal mass. The t(8;14) associated with Burkitt's lymphoma was found in the mass tissue only following passage in the nude mouse. Our patient demonstrates that limitations still exist in our ability to classify acute leukemia. That leukemic transformation occurred in a multipotential progenitor cell leading to undifferentiated leukemia at diagnosis and/or that chemotherapy can influence the genetic programs of leukemic cells leading to the evidence of mixed-lineage leukemia and lineage switching is supported.

Multiple lineage reactivity in childhood leukemia

The leukemia cells from 63 children with acute leukemia were evaluated by flow cytometry with a panel of monoclonal antibodies that included lymphoid and myeloid lineage-specific antigens. Surface markers from patients with acute lyphocytic leukemia (ALL) did not correlate with their FAB classification except for L3 leukemia. Myeloid leukemias of FAB class M1-M4 were positive for CD13 and CD33, whereas CD14 and MY8 were only detected in FAB class M4 leukemia. Mixed leukemias were subclassified as intralineage (B+T+) or interlineage (B+ or T+/M+). Interlineage leukemias represented 5.6% of ALLs, and all patients are alive after treatment with ALL protocols. Interlineage mixed leukemias represent 7.9% of all leukemias occurring in 3.7% of ALLs and 33% of acute myeloid leukemias (AMLs). All children with mixed interlineage leukemias are alive after treatment with the protocol for the dominant leukemia; however, follow-up periods are too short to predict final outcome. The high proportion of mixed interlineage leukemias in AMLs supports Greaves' theory of lineage promiscuity, that is, there is a normal period of hematopoietic development when individual cells co-express multiple lineage antigens on the cell surface.

Secondary acute myeloid leukemia in children treated for acute lymphoid leukemia

We studied the risk of the development of acute myeloid leukemia (AML) during initial remission in 733 consecutive children with acute lymphoid leukemia (ALL) who were treated with intensive chemotherapy. This complication was identified according to standard morphologic and cytochemical criteria in 13 patients 1.2 to 6 years (median, 3.0) after the diagnosis of ALL. At three years of follow-up, the cumulative risk of secondary AML during the first bone marrow remission was 1.6 percent (95 percent confidence limits, 0.7 and 3.5 percent); at six years, it was 4.7 percent (2 and 10 percent). The development of secondary AML was much more likely among patients with a T-cell than a non-T-cell immunophenotype (cumulative risk, 19.1 percent [6 and 47 percent] at six years). Sequential cytogenetic studies in 10 patients revealed entirely different karyotypes in 9, suggesting the induction of a second neoplasm. In eight of these patients, the blast cells had abnormalities of the 11q23 chromosomal region, which has been associated with malignant transformation of a pluripotential stem cell. There was no evidence of loss of DNA from chromosome 5 or 7, a karyotypic change commonly observed in cases of AML secondary to treatment with alkylating agents, irradiation, or both. We conclude that there is a substantial risk of AML in patients who receive intensive treatment for ALL, especially in those with a T-cell immunophenotype, and that 11q23 chromosomal abnormalities may be important in the pathogenesis of this complication.

Hybrid acute leukemia in an HIV-antibody-positive patient

Although the great majority of acute leukemias have been designated as being of lymphocytic or myelocytic origin, recent reports have described elements of both in some patients. We describe here the first case of hybrid acute leukemia in an HIV-antibody-positive patient as well as the first hybrid involving B-cell (Burkitt) acute lymphocytic leukemia and acute myelomonocytic leukemia proven by cytochemical, immunologic, and cytogenetic methods. This case illustrates the increasingly complex difficulties in the diagnosis and treatment of AIDS-related malignancies.

Childhood biphenotypic leukemia: detection of mixed lymphoid and myeloid populations in bone marrow specimens

In a retrospective study, consecutive bone marrow biopsies and smears from 104 children with leukemia were analyzed for expression of lymphoid and myeloid lineage-associated features. Eighty-six cases were diagnosed as acute lymphoblastic leukemia (ALL), 14 cases as acute non-lymphocytic leukemia (ANLL), and one case as chronic myelogenous leukemia (CML). Finally, three children were classified as biphenotypic leukemia demonstrating mixed populations of lymphoid and myeloid blast cells from the onset of the disease. Thus, leukemia with a dual phenotype was assessed in 2.9% of all cases examined. The recognition of bilineage origin even by conventional methods such as morphology, cytochemistry and marker studies may be important for the selection of an effective treatment.

The role of ultrastructural cytochemistry and monoclonal antibodies in clarifying the nature of undifferentiated cells in acute leukaemia

The nature of the cells in 21 cases of acute leukaemia with blasts which were undifferentiated by light microscopy criteria was investigated by immunophenotyping, ultrastructural cytochemistry and DNA analysis. Two groups of cases were recognized. Fourteen cases were negative with B and T lymphoid markers and expressed one or two myeloid antigens detected by the monoclonal antibodies (McAb) MCS2 (CD13) and MY9 (CD33). Peroxidase activity was demonstrated at ultrastructural level by the method of Roels on unfixed cells in eight out of 10 cases; rearrangement of the immunoglobulin (Ig) genes was demonstrated in one of the three cases investigated. These cases are proliferations of early, MO, myeloblasts which can only be recognized by immunological and ultrastructural cytochemical methods. The remaining seven cases revealed a complex phenotype with expression of myeloid and lymphoid antigens. Peroxidase activity was detected in blasts from two cases with rearrangement of the Ig-heavy chain gene; in one of them the T cell receptor beta and gamma chain genes were also found in rearranged configuration. This group comprises cases of biphenotypic and mixed acute leukaemia which probably involve multipotent stem cells. This study demonstrates that the expression of myeloid antigens on blast cells parallels closely the presence of peroxidase activity and that lymphoid markers correlate with gene rearrangements at DNA level. Our findings are reassuring with respect to the specificity of the antimyeloid McAb for the diagnosis of cases which are unclassifiable by conventional methods.

Phenotypic conversion of T lymphoblastic lymphoma to acute biphenotypic leukemia composed of lymphoblasts and myeloblasts. Molecular genetic evidence of the same clonal origin

Acute biphenotypic leukemia composed of lymphoblasts and myeloblasts developed in a patient with T lymphoblastic lymphoma (T-LBL) who had an anterior mediastinal mass. A novel myeloid cell line, termed TK-1, has been established from his peripheral blood after the leukemic conversion. The identical rearranged pattern of T cell receptor gamma-chain gene was observed among the DNAs derived from lymph node cells in the lymphoma phase, the myeloid cell line TK-1, and the subclones with different karyotypes (TK-1B and TK-1D), which showed that myeloid cells had been derived from the T-LBL of the same patient. This finding demonstrates that phenotypic conversion occurs in the clonally propagating tumor cells and suggests that some hematopoietic cells retain the capacity to adopt either lineage.

Immunoglobulin heavy chain gene rearrangements and mixed lineage characteristics in acute leukemias with the 11;19 translocation

Although the origin of acute leukemia with the 4;11 translocation has been shown to be an early myeloid progenitor cell or a stem cell with the potential for differentiation into both lymphoid and myeloid lineage, few precise studies on acute leukemia with the 11;19 translocation have thus far been reported. This study focused on the clinical, morphologic, ultrastructural, and immunologic characteristics as well as the DNA in three cases of acute leukemia with the 11;19 translocation. All three patients were infants and showed hyperleukocytosis. The morphologic feature was French-American-British (FAB)-L2 in two patients, in one of which a few monocytoid blasts were also seen by electron microscopy. Cells from the third patient underwent morphologic changes from FAB-L2 at the time of diagnosis to M5b at relapse. Immunologic marker studies revealed that the blast cells from all three patients expressed Ia and B4, but none expressed B1, CALLA(J5), T antigens, or SIg. Cells from one patient simultaneously expressed myeloid antigen (MCS-II) both at diagnosis and relapse. Cells from two patients expressed myeloid antigen after being cultured for a short time in vitro. An analysis of immunoglobulin genes and T-cell receptor genes revealed rearrangements of the heavy chain genes and germ line configurations of the kappa and lambda light chain genes, and of the T-cell receptor beta chain genes. These findings suggest that acute leukemia with the 11;19 translocation has mixed lineage characteristics as a result of leukemogenesis in a stem cell with the potential for both lymphoid and myeloid, especially monocytic, differentiation.

Clinical importance of myeloid antigen expression in adult acute lymphoblastic leukemia

To determine the clinical importance of immunophenotypes in adult acute lymphoblastic leukemia (ALL), we prospectively studied 76 patients with this condition. Before treatment, lymphoblasts were tested for reactivity with monoclonal antibodies to B-cell, T-cell, and myeloid (My) antigens. Unexpectedly, myeloid antigens (MCS-2 or MY9) were identified in 25 patients (33 percent), usually in conjunction with B-cell or T-cell antigens. Among My+ patients, 15 (60 percent) expressed B-cell antigens (B+T-My+); all 6 tested had rearranged immunoglobulin genes. Five patients (20 percent) expressed T-cell antigens (B-T+My+), and one My+ patient expressed both B-cell and T-cell antigens. Only myeloid antigens (B-T-My+) were expressed in four patients (16 percent); three who were tested had germ-line immunoglobulin and T-cell-receptor gene configurations. Although no significant differences in presenting clinical features were found, My+ patients had fewer complete remissions than My- patients (35 vs. 76 percent, P less than 0.01). No differences in response or survival were observed between My+ and My- patients expressing T-cell antigens. However, among those expressing B-cell antigens, My+ patients had fewer complete remissions (29 vs. 71 percent, P = 0.02) and shorter survival (P = 0.03; median, 8.1 vs. greater than 26 months). These findings indicate that expression of myeloid antigen identifies a high-risk group of patients with adult ALL for whom alternative forms of treatment should be investigated.

A reappraisal of Richter's syndrome. Development of two phenotypically distinctive cell lines in a case of chronic lymphocytic leukemia

Richter's syndrome, the development of a malignant lymphoma in a patient with preexisting chronic lymphocytic leukemia (CLL) is an infrequent but well-documented phenomenon generally thought to represent a monoclonal proliferation of B-lymphocytes arising from the CLL. A heterogeneous population of cells consisting of sheets of transformed lymphocytes in combination with clusters of bizarre, atypical histiocytes developed in a patient with a history of longstanding CLL. Immunocytochemistry using a panel of monoclonal and polyclonal antibodies by immunoperoxidase techniques identified the presence of both B-lymphocytic and monocytic-histiocytic cell lines of differentiation. A mechanism of multiple differentiation is proposed to account for the dual cell population observed in this patient. Review of the literature appears to indicate that this phenomenon often may be involved in cases diagnosed as Richter's syndrome. The demonstration of cellular heterogeneity in the current case underscores the need for establishing a more precise definition for the histologic characterization of the terminal malignancy in Richter's syndrome.

Undifferentiated leukemia of infancy with t(11:17) chromosomal rearrangement. Coexpressing myeloid and B cell restricted antigens

It has been suggested that the malignant transformation, in some of the acute leukemias, may involve totipotent stem cells resulting in a biphenotypic leukemia expressing both myeloid, and lymphoid characteristics. We describe here a hybrid cell acute leukemia, in a 16-day-old infant, in whom leukemic cells coexpressed myeloid and lymphoid B cell antigens. Blast cells in the bone marrow showed L2 morphology according to the French American British (FAB) classification, with positive periodic-acid Schiff, and nonspecific esterase staining. Sudan black, and specific esterase were negative. Terminal deoxynucleotidyl transferase, was strongly positive in 5% of blasts, and faintly reactive with the rest. Karyotypic analysis demonstrated a translocation of t(11:17);(q23;p13). Immunoglobulin gene analysis revealed rearrangement of the heavy chain genes. The blasts' phenotype was HLA/DR+ B4+ My7+ My9+ common acute lymphoblastic leukemia antigen (CALLA) B1- T11-. Dual immunofluorescence staining using anti My7, and My9 fluorescein isothiocyanate, and anti B4 pycoerythrin conjugated monoclonal antibodies, and flow cytofluorometry, revealed a labeling pattern of 25% B4+; 10% to 15% My7+; 17% My9+; and 50% of cells coexpressing B4 My7, and My9 antigens. These results provide evidence for a hybrid leukemia with lymphomyeloblasts being part of a single clone, which may indicate the origin of this leukemic clone from a pluripotent (lymphoid/myeloid) stem cell.

Myelo-monocytic differentiation potential of the CALLA-positive Nalm 6M1 cell line

Nalm 6M1 cells, derived from an acute lymphoblastic leukemia of the non-T, non-B type, are known to possess characteristics of early B-lymphocytes. In order to determine whether these cells are able to differentiate along the granulocyte-monocyte pathway, they were cultured in diffusion chambers, and classified according to morphological, cytochemical and immunological criteria. On the basis of this characterization, Nalm 6M1 cells positively labeling with monoclonal anti-human granulocyte or monocyte-specific antibodies were observed in all cases. These immunological changes were accompanied by the appearance of cells positive for the naphthyl-AS-D-chloroacetate esterase reaction. However, no changes in the blast-like appearance of the cultured cells were seen. From these data, we conclude that Nalm 6M1 cells already committed to the B-cell lineage retain their capacity to develop cellular markers of the granulocyte-monocyte series.

T-cell acute lymphoblastic leukemia relapsing as acute myelomonocytic leukemia and terminating possibly as chronic myelocytic leukemia

A 9-year-old boy suffering from T-cell acute lymphoblastic leukemia (T-ALL) with a mediastinal mass had a complete remission as a result of treatment. Ten months later, he developed a typical acute myelomonocytic leukemia (AMMoL) pattern. Two months after a second relapse, he showed a clinical picture that was indistinguishable from chronic myelocytic leukemia (CML). At autopsy, massive infiltration of CML-like cells was observed even in the thymus (190 g). These observations suggest that the leukemia in this child arose in a pluripotent stem cell capable of differentiation into both T-lymphocytic and myelomonocytic lineages.

Molecular and immunological evidence of B-cell commitment in "null" acute lymphoblastic leukaemia

The DNA configuration of the immunoglobulin (Ig) heavy and light chain genes and the expression of B-cell-related markers were evaluated in 13 cases of non-T, non-B, non-common ("null") acute lymphoblastic leukaemia (ALL). A rearrangement of the Ig heavy-chain gene was found in all cases studied; in 5 of these a structural reorganization of the kappa or lambda light chain gene was also demonstrated. Leukaemic cells from 10 of the 13 cases analysed showed one or more B-cell antigens, the expression of which followed a sequential order of presentation (OKB2, B4, BA-1, B1). The B-cell commitment was confirmed by means of a sensitive immunoperoxidase assay which revealed a weak expression of the common ALL (cALL) antigen in 7/10 cases tested, which were all cALL-negative by conventional immunofluorescence techniques. These findings suggest that in "null" ALL the neoplastic cells show molecular and immunological evidence of B-cell differentiation and that most cases may indeed be characterized by "early" cALL with a very low density expression of the cALL antigen. This was further documented in one case in which the expression of the cALL antigen (and of other B-cell markers) could be induced after exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA). The presence in a few cases of myeloid features, particularly when the cALL antigen could not be demonstrated by the immunoperoxidase assay, suggests that the leukaemic process may sometimes involve a very early progenitor cell capable of both lymphoid and myeloid phenotypic differentiation. The heterogeneity of "null" ALL documented by this study may help to explain the variable clinical course and prognosis of these patients.

Immunophenotypic transformation from acute undifferentiated leukemia to Burkitt's-like acute lymphoblastic leukemia

Progression of more differentiated to less differentiated malignant phenotypes has been described infrequently during the natural evolution or at relapse of treated hematopoietic malignancies. This report describes an unusual instance of immunophenotypic transformation from an immunologically undifferentiated acute leukemia to a leukemia that at relapse possessed morphologic and immunologic markers characteristic of a Burkitt's-like acute lymphoblastic leukemia. A 26-year-old man initially presented with pancytopenia and a bone marrow diffusely replaced with blast cells morphologically most consistent with a French-American-British L2 subclassification. The surface immunophenotype of the blasts at diagnosis showed HLA-DR surface antigen but no myeloid, lymphoid, or immunoglobulin determinants. Despite successful induction and ongoing consolidation chemotherapy, the patient had a relapse five months after diagnosis; blast cells at relapse demonstrated marked cytoplasmic vacuolation consistent with a Burkitt's-like L3 acute lymphoblastic transformation. Immunophenotypic analysis revealed the presence of restricted immunoglobulin determinants (mu heavy chain and kappa light chain), as well as two separate B lineage surface determinants (BA-1 and B-1). Immunophenotypic transformations may reflect the presence of either a multiclonal or multipotent leukemic population; documentation of the frequency of such transformations and genomic analysis of the transformed subpopulations may be helpful in furthering the understanding of molecular mechanisms involved in leukemogenesis.

Murine hematopoietic cells with pre-B or pre-B/myeloid characteristics are generated by in vitro transformation with retroviruses containing fes, ras, abl, and src oncogenes

In vitro infection of bone marrow or fetal liver cells with retroviruses containing fes, abl, ras, or src oncogenes resulted in the transformation of early B lineage cells. All cell lines tested possessed rearrangements at the Ig heavy chain locus and some had rearrangements at the K chain locus. The majority of the lines corresponded phenotypically to Lyb-2+, Ly-5(B220)+, ThB- large pre-B cells, although some were classified as pro-B cells because of their Lyb-2+, Ly-17+, Ly-5(B220)- phenotype. We identified two cell lines that contained subpopulations of cells that coexpressed the B lineage antigens Lyb-2 and Ly-5(B220) and the myeloid lineage antigen Mac-1. Single-cell FMF cloning of these subpopulations showed that Mac-1+ cells were derived from Mac-1- cells and that these Mac-1+-cloned cells further differentiated into cells with phenotypic and functional characteristics of mature macrophages.

Biphenotypic lymphoblastic lymphoma. An unusual tumor with lymphocytic and granulocytic differentiation

An unusual example of a lymphoblastic lymphoma with evidence of both T-lymphocytic (Leu-1, Leu-2, Leu-3, OKT-6, terminal transferase-positive) and immature granulocytic (Mo1, chloroacetate esterase, lysozyme, alpha-1-antitrypsin-positive) cell proliferations was studied. The tumor arose in the oropharynx of a 39-year-old man without evidence of blood or bone marrow involvement. This tumor has been termed a "biphenotypic lymphoblastic lymphoma," and the origin of which appears to be from uncommitted progenitor cells capable of both lymphoid and myeloid differentiation. Biphenotypic lymphoblastic lymphomas, like biphenotypic leukemias, may occur more commonly than is appreciated, and may account for reported cases of acute myeloblastic leukemia after lymphoblastic lymphoma.

Conversion of acute undifferentiated leukemia phenotypes: analysis of clonal development

The cellular origin of acute undifferentiated leukemia (AUL) is still a matter of controversy. We report on two cases in which the diagnosis of AUL was established according to restricted criteria. Blast cells of both patients showed phenotypic conversion during the course of disease. In one case, within 24 days from starting treatment, the leukemic phenotype changed from AUL to acute myelomonocytic leukemia (FAB L1, TdT+ to FAB M4, TdT-). The initial phenotype of this acute leukemia was characterized by the co-expression of both B-lymphoid and myeloid markers on the same cell. Moreover, analysis of esterase isoenzyme pattern showed the whole spectrum of isoenzymes typically seen in myelomonocytic leukemias already at diagnosis, yet blast cells additionally contained all three isoenzymes of beta-hexosaminidase typically seen in AUL. However, examination of immunoglobulin (Ig) heavy chain gene rearrangement initially and after conversion revealed an identical monoclonal configuration of Ig heavy chain sequences in both samples. The second AUL patient relapsed after allogeneic bone marrow transplantation with common ALL-antigen (CALLA) positive acute leukemia. Subsequent Southern blot analysis showed a novel rearranged Ig fragment compared to the analysis before transplantation indicating that the leukemic clones prior to and after transplantation were not identical. No chromosomal abnormalities were observed in both cases. These data support the view that AUL cells originate from a pluripotent stem cell that is capable to differentiate in the myelomonocytic lineage (patient 1), and confirm the value of Ig gene analysis as marker for cellular clonality.

Establishment of the DU.528 human lymphohemopoietic stem cell line

We have established the DU.528 cell line from the pretreatment leukemia cells of a patient who underwent a T lymphoblastic-to-promyelocytic phenotype conversion during treatment with the adenosine deaminase inhibitor, deoxycoformycin. The cell line and clones obtained from it by limiting dilution have the same karyotype previously found in the patient's pretreatment T lymphoblasts and post-deoxycoformycin treatment promyelocytes. DU.528 cells in continuous culture for greater than 2 yr display a predominant undifferentiated T lymphoblastoid phenotype. These cells spontaneously generate progeny of at least three lineages, T lymphoid, granulocytic/monocytic, and erythroid. The surface marker most consistently expressed by DU.528 cells in the undifferentiated state is the 3A1 antigen, which has been found on prothymocytes in the embryonic thymus. Some undifferentiated DU.528 cells also expressed the IL-2 receptor, but no other T cell differentiation antigens. Exposure of DU.528 cells to a variety of agents induced myeloid maturation; adenosine and deoxyadenosine, in the presence of deoxycoformycin, induced expression of myeloid differentiation antigens. Our results suggest that DU.528 is a lymphohematopoietic stem cell line and support the hypothesis that differentiation of pluripotent stem cells may be altered by genetic deficiency of adenosine deaminase. DU.528 cells may provide a useful model for examining factors that regulate stem cell proliferation and differentiation.

Childhood leukemia with simultaneously expressed myeloid and lymphoid markers suggesting stem cell origin

A case study is presented of a leukemic patient whose cells express markers of both myeloid and lymphoid cells. Cells were identified from bone marrow which expressed either myeloid antigens, lymphoid antigens, or both myeloid and lymphoid antigens, indicating a possible common stem cell capable of differentiating along either a lymphoid or myeloid cell lineage. Using specific monoclonal antibodies, 40-70% of the cells were reactive with anti-T-cell antibodies, 50% of the cells were reactive with antibodies to the common ALL antigen (CALLA), and 80-90% of the cells were reactive with antibodies directed against myeloid antigens. Using double staining techniques, some cells were found to demonstrate only myeloid markers; others, only lymphoid markers; and others, both myeloid and lymphoid markers. These results suggest that a common stem cell is capable of differentiating along both lymphoid and myeloid lineages.

Characterization of myeloid leukemias with monoclonal antibodies 3C5 and MY9

The expression of two membrane antigens identified by the monoclonal antibodies (McAb) My9 and 3C5 has been investigated in cells from 80 acute leukemias. My9 was positive in the blasts of 33 out of the 38 (87 per cent) cases of acute myeloid leukemia (AML) tested, regardless of FAB subtype, and in 13 of 18 (72 per cent) cases of chronic granulocytic leukemia (CGL) in myeloid blast crisis. The reactivity of 3C5 was confined to myeloblastic (M1) AML, 85 per cent of cases, and to lymphoblastic leukemia (ALL) of B-lineage, 70 per cent of cases, including CGL in lymphoid transformation. My9 was negative in ALL except for an unusual case. The phenotype My9+, 3C5+ was seen exclusively in M1 (69 per cent) and M2 (14 per cent) AML. Ultrastructural analysis with the immunogold method in combination with the myeloperoxidase (MPO) reaction showed that expression of My9 increased in parallel with MPO activity whereas 3C5 was expressed mainly in myeloblasts with little MPO content. We conclude that the use of these two McAb will contribute to the diagnosis and classification of AML and may throw some light to the pathogenesis of biphenotypic acute leukemias, including TdT + AML.

Biphenotypic leukaemia: a case of mixed T lymphoblastic and myeloblastic leukaemia

A case of mixed acute leukaemia with T lymphoblastic, myeloblastic, and monocytic components is described. The use of immunological markers, ultrastructural morphology, cytochemistry, immunochemistry, and combined techniques, simultaneously detecting two markers in individual cells, made it possible to define the different blast cell populations.

Leukemia with a novel 4q11q rearrangement

Translocation (4;11)(q21;q23) is characteristic of a distinct acute leukemic syndrome. We report an 8-wk-old male patient with the clinical features ascribed to t(4;11), but with an unusual chromosome rearrangement consisting of an insertion of the 11q23 band into the q21 region of chromosome #4.

11;19 translocation in a congenital leukemia with two cell populations of lymphoblasts and monoblasts

This report describes a case of a female infant of congenital leukemia with a chromosomal translocation t(11;19) (q23;p13) which presented initially with lymphoid features and at relapse with monocytic ones. The clinical course and the results of sequential cytochemical, cytogenetic and immunological studies are considered to be consistent with the interpretation of leukemogenesis of the myelo-monocytoid progenitor cell which still retains the capability of exhibiting lymphoid features to a limited extent. Although leukemia with t(11;19) has been classified as ANLL, most commonly M5 of FAB classification, the patient with this chromosomal abnormality may have a mixed leukemia in which cells with lymphoid features and those with monocytic ones exist.

In vitro drug testing using hemopoietic cells: goals and limitations

In vitro drug sensitivity is one of many biologic variables which may predict in vivo drug response. Even if in vitro assays provide relevant data, for some tumors, variable levels of stem-cell origin, differentiation, tumor heterogeneity, or self renewal may be more important than cytotoxicity to proliferating cells. Although ANLL has been used here frequently as a model, it may not be the most appropriate tumor for study. Unlike many cancers, in ANLL, primary drug resistance is unusual, and in relapse, secondary drug resistance is usually incomplete. It has been suggested that in vitro drug sensitivity predicts remissions for patients who do not die of infection or remain aplastic during induction therapy. However, for the majority of patients, this argument acknowledges the overriding importance of biologic variables other than in vitro drug cytotoxicity. For rapidly growing tumors, such as Burkitt's lymphoma, rapid emergence of drug resistance related to disease burden may be the most important response determinant. Perhaps in other tumors, in vitro drug sensitivity will be an independent variable of overriding importance. To determine the role of in vitro drug testing, trials examining in vitro drug sensitivity must meet stringent criteria. The assays should use well-defined and reproducible cultures and drug exposures. The trials must be large enough, contain homogenously treated patients, and use carefully defined response and survival endpoints. Decision rules derived from such trials must be further tested by prospective evaluation. Investigators conducting these trials must be prepared to search for important in vitro results reflecting tumor biology and to analyze in vitro drug sensitivity as only one continuous variable determining in vivo responses. Such trials will be difficult to conduct and expensive. In the final analysis, in vitro assays may find their most important roles as preclinical drug screens and models for in vitro drug resistance. Further insights into molecular genetics of malignant transformation and drug resistance may make such assays obsolete, but for the present, they provide important insights into tumor variability and mechanisms of drug response.

Reproducibility of the French-American-British classification of acute leukemia: the Southwest Oncology Group Experience

After initial French-American-British (FAB) diagnosis by a multiinstitutional Southwest Oncology Group panel, slides of acute leukemia cases were recirculated to panel members for second review. The reproducibility of the FAB classification is analyzed. The classification is reproducible in the 70% range in panel reviewer hands and allows remarkable reproducibility in the morphologic and cytochemical distinction of acute lymphoid leukemia (ALL) from acute myeloid leukemia (AML). The limitations of a morphologic and cytochemical classification of acute leukemia are discussed. A simplification of the FAB system, merging M1, M2, and M4 as M7, is proposed; this simplification improves the system's reproducibility.

Conversion of a stem cell leukemia from a T-lymphoid to a myeloid phenotype induced by the adenosine deaminase inhibitor 2'-deoxycoformycin

Selective failure of lymphoid development occurs in genetic deficiency of adenosine deaminase (ADA). We examined the in vivo effects of a potent inhibitor of ADA, 2'-deoxycoformycin, which was used to treat a patient with refractory acute leukemia. Unexpectedly, within 7 days of starting treatment, the leukemic phenotype underwent complete conversion from T lymphoblastic to promyelocytic, with kinetics that suggested a precursor-product relationship between the two cell populations. Pretreatment T lymphoblasts and posttreatment promyelocytes had the same abnormal karyotype. Upon culture in vitro, the former transformed spontaneously over several weeks into mature myeloid cells. We conclude that the leukemia arose from a multipotent stem cell capable of both lymphoid and myeloid differentiation. Effects of ADA inhibition on leukemia cells during treatment included expansion of the deoxyadenosine nucleotide pool and accumulation of S-adenosylhomocysteine, a potent inhibitor of S-adenosylmethionine-dependent methylation. The influence of these changes on the leukemic phenotype is discussed in terms of (i) selective cytotoxicity to T lymphoblasts, which accumulated deoxyadenosine nucleotides more efficiently than did the patient's promyelocytes during in vitro incubation with deoxycoformycin plus deoxyadenosine, and (ii) induction of an altered program of differentiation.