Abnormalities of chromosome 16 in association with acute myelomonocytic leukemia and dysplastic bone marrow eosinophils

Mutations in the neutral sphingomyelinase gene SMPD3 implicate the ceramide pathway in human leukemias

Ceramide is a lipid second messenger derived from the hydrolysis of sphingomyelin by sphingomyelinases (SMases) and implicated in diverse cellular responses, including growth arrest, differentiation, and apoptosis. Defects in the neutral SMase (nSMase) gene Smpd3, the primary regulator of ceramide biosynthesis, are responsible for developmental defects of bone; regulation of ceramide levels have been implicated in macrophage differentiation, but this pathway has not been directly implicated in human cancer. In a genomic screen for gene copy losses contributing to tumorigenesis in a mouse osteosarcoma model, we identified a somatic homozygous deletion specifically targeting Smpd3. Reconstitution of SMPD3 expression in mouse tumor cells lacking the endogenous gene enhanced tumor necrosis factor (TNF)-induced reduction of cell viability. Nucleotide sequencing of the highly conserved SMPD3 gene in a large panel of human cancers revealed mutations in 5 (5%) of 92 acute myeloid leukemias (AMLs) and 8 (6%) of 131 acute lymphoid leukemias (ALLs), but not in other tumor types. In a subset of these mutations, functional analysis indicated defects in protein stability and localization. Taken together, these observations suggest that disruption of the ceramide pathway may contribute to a subset of human leukemias.

Uncommon phenotypes of acute myelogenous leukemia: basophilic, mast cell, eosinophilic, and myeloid dendritic cell subtypes: a review

The potential of the transformed (leukemic) multipotential hematopoietic cell to differentiate and mature along any myeloid lineage forms the basis for the phenotypic classification of acute and chronic myelogenous leukemia. Although most cases of leukemia can be classified phenotypically by the dominant lineage expressed, the genotype within each phenotype is heterogeneous. Thus, covert genetic factors, cryptic mutations, and/or polymorphisms may interact with the seminal transforming genetic mutations to determine phenotype. The phenotype usually is expressed sufficiently to determine the lineage that is dominant in the leukemic clone by light microscopic examination, by cytochemistry of blood and marrow cells, and by immunophenotyping. The basis for the frequency of the AML phenotypes is unclear, although there is a rough concordance with the frequency of marrow precursor cells of different lineages. The least common AML phenotypes are a reflection of the least common blood or marrow cell lineages: acute basophilic, acute mast cell, acute eosinophilic, and acute myeloid dendritic cell leukemia. We discuss the features of these uncommon phenotypes and review the criteria used for their diagnosis.

Acute monoblastic leukemia with t(8;16): a distinct clinicopathologic entity; report of a case and review of the literature

We report a case of acute monoblastic leukemia with t(8;16) in a 71-year-old man who had rapid rise of leukocyte counts from 20.3 x 10(9)/l to 62.7 x 10(9)/l in two weeks. The peripheral blood showed many granular promonocytes that led to the consideration of acute promyelocytic leukemia of the hypogranular variant. The bone marrow, however, revealed mainly monoblasts with erythrophagocytosis. Cytogenetic study finally confirmed the diagnosis of acute monoblastic leukemia with t(8;16). The patient died three days after admission. The demonstration of these two characteristic features of this subtype, granular promonocytes and erythrophagocytosis by monoblasts, separately, in the peripheral blood and bone marrow is unusual and misleading. This cytogenetic abnormality can be demonstrated only in M5 and M4 with characteristic clinical features of disseminated intravascular coagulation, extramedullary involvement, and poor prognosis. Although it is not a common disease, this specific subtype of acute myelogenous leukemia is consistently associated with a specific cytogenetic marker, thus it should be considered a distinct clinicopathologic entity.

A unique structural abnormality of chromosome 16 resulting in a CBF beta-MYH11 fusion transcript in a patient with acute myeloid leukemia, FAB M4

A 43-year-old female with a peripheral white cell count of 118.0 x 10(9)/L and 96% blasts was diagnosed with acute myeloid leukemia (AML), FAB M4. Cytogenetics, performed on a bone marrow sample, revealed the following abnormal karyotype: 46,XX,ins(16)(q22p13.1p13. 3). Fluorescence in situ hybridization (FISH) confirmed the inter-arm insertion using a probe for 16p. The result of this structural rearrangement was the fusion of CBF beta to MYH11 seen commonly in inv(16)(p13q22). The patient commenced high-dose intensive combination chemotherapy (big ICE; Idarubicin, Cytarabine, and Etopiside). Five days post chemotherapy, she developed febrile neutropenia. Despite broad spectrum intravenous antibiotics and antifungal therapy, the patient died at day nine post chemotherapy. This case demonstrates a previously unreported structural abnormality of chromosome 16 in a patient with AML M4, which represents a third mechanism to inv(16)(p13q22) and t(16;16)(p13q22) in producing the CBF beta-MYH11 fusion. CBF beta-MYH11 fusions masked by cryptic translocations at the cytogenetic level have been detected by FISH and PCR techniques. Due to the improved prognosis associated with CBF beta-MYH11 fusions compared to the standard risk group for AML, its detection remains important.

Characterization and Use of an Antibody Detecting the CBFβ-SMMHC Fusion Protein in inv(16)/t(16;16)-Associated Acute Myeloid Leukemias

The inv(16)(p13q22) and t(16;16)(p13;q22) cytogenetic abnormalities occur commonly in acute myeloid leukemia (AML), typically associated with French-American-British (FAB) AML-M4Eo subtype. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques have been recently developed to detect the presence of several variants of the resultant CBFB-MYH11 fusion gene that encodes a CBFβ-smooth muscle myosin heavy chain (SMMHC) fusion protein. We have now determined the clinical use of a polyclonal antibody [anti-inv(16) Ab] directed against a junctional epitope of the most common type of CBFβ-SMMHC fusion protein (type A), which is present in 90% of inv(16)/t(16;16) AML cases. Using flow cytometry, reproducible methods were developed for detection of CBFβ-SMMHC proteins in permeabilized cells; flow cytometric results were then correlated with cytogenetics and RT-PCR detection methods. In an analysis of 42 leukemia cases with various cytogenetic abnormalities and several normal controls, the anti-inv(16) Ab specifically detected all 23 cases that were cytogenetically positive for inv(16) or t(16;16), including a single AML case that was RT-PCR–negative. In addition to detecting all type A fusions, the anti-inv(16) Ab also unexpectedly identified the type C and type D CBFβ-SMMHC fusion proteins. Molecular characterization of one RT-PCR–positive and Ab-positive t(16;16) case with a non-type A product showed a novel previously unreported CBFB-MYH11 fusion (CBFB nt 455-MYH11 nt 1893). Flow cytometric results were analyzed using the Kolmogorov-Smirnov statistic D-value and the median value for positive samples was 0.65 (range, 0.35 to 0.77) versus 0.07 (range, −0.21 to 0.18) in the negative group (P < .0001). The overall concordance between cytogenetics and RT-PCR was 97%, whereas the concordance between flow cytometry and cytogenetics was 100%. Thus, using the anti-inv(16) Ab, all cytogenetically positive and RT-PCR–positive AML cases with inv(16) or t(16;16) could be rapidly identified. This study demonstrates the use of this antibody as an investigational tool in inv(16)/t(16;16) AML and suggests that the development of such reagents may have potential clinical diagnostic use.

Characterization and Use of an Antibody Detecting the CBFβ-SMMHC Fusion Protein in inv(16)/t(16;16)-Associated Acute Myeloid Leukemias

The inv(16)(p13q22) and t(16;16)(p13;q22) cytogenetic abnormalities occur commonly in acute myeloid leukemia (AML), typically associated with French-American-British (FAB) AML-M4Eo subtype. Reverse transcriptase-polymerase chain reaction (RT-PCR) techniques have been recently developed to detect the presence of several variants of the resultant CBFB-MYH11 fusion gene that encodes a CBFβ-smooth muscle myosin heavy chain (SMMHC) fusion protein. We have now determined the clinical use of a polyclonal antibody [anti-inv(16) Ab] directed against a junctional epitope of the most common type of CBFβ-SMMHC fusion protein (type A), which is present in 90% of inv(16)/t(16;16) AML cases. Using flow cytometry, reproducible methods were developed for detection of CBFβ-SMMHC proteins in permeabilized cells; flow cytometric results were then correlated with cytogenetics and RT-PCR detection methods. In an analysis of 42 leukemia cases with various cytogenetic abnormalities and several normal controls, the anti-inv(16) Ab specifically detected all 23 cases that were cytogenetically positive for inv(16) or t(16;16), including a single AML case that was RT-PCR–negative. In addition to detecting all type A fusions, the anti-inv(16) Ab also unexpectedly identified the type C and type D CBFβ-SMMHC fusion proteins. Molecular characterization of one RT-PCR–positive and Ab-positive t(16;16) case with a non-type A product showed a novel previously unreported CBFB-MYH11 fusion (CBFB nt 455-MYH11 nt 1893). Flow cytometric results were analyzed using the Kolmogorov-Smirnov statistic D-value and the median value for positive samples was 0.65 (range, 0.35 to 0.77) versus 0.07 (range, −0.21 to 0.18) in the negative group (P < .0001). The overall concordance between cytogenetics and RT-PCR was 97%, whereas the concordance between flow cytometry and cytogenetics was 100%. Thus, using the anti-inv(16) Ab, all cytogenetically positive and RT-PCR–positive AML cases with inv(16) or t(16;16) could be rapidly identified. This study demonstrates the use of this antibody as an investigational tool in inv(16)/t(16;16) AML and suggests that the development of such reagents may have potential clinical diagnostic use.

Translocation t(8;16)(p11;p13) in acute non-lymphocytic leukemia: report on two new cases and review of the literature

Two new cases of t(8;16)(p11;p13) in acute nonlymphocytic leukemia (ANLL) are described. These two patients in addition to the 34 previously described, showed a striking association with myelomonocytic (M4) or monocytic (M5) leukemia, extramedullary infiltration, erythrophagocytosis and disseminated intravascular coagulation. One of our patients showed a TCRbeta gene rearrangement. Alltogether 36 cases of t(8;16) ANLL have been documented until today. We here review their clinical and cytogenetic features.

A distinct subtype of M4/M5 acute myeloblastic leukemia (AML) associated with t(8:16)(p11:p13), in a patient with the variant t(8:19)(p11:q13)--case report and review of the literature

Acute myeloblastic leukemia (AML) with t(8:16) or its variant t(8:V) has been rarely reported. A high proportion of patients are infants and children, often with a bleeding tendency and disseminated intravascular coagulopathy (DIC). Only one-third of the de novo patients remain in the first complete remission following multiagent chemotherapy and bone marrow transplantation (BMT). Morphocytochemically, the disorder is classified as an M5, M4, or M4/M5 variant. In the presented case, with the variant t(8:19)(p11:q13), comprehensive light and electron microscopic blast cell characterization showed monocytic and granulocytic features compatible with the M4 subtype (on the monocytic predominance range of the French-American-British classification scale). Although hemophagocytosis, one of the hallmarks of the disease, was rare in our patient, numerous autophagic vacuoles were present. Immuno- and genotyping showed a myelomonocytic phenotype with no evidence of early progenitor antigen expression or mixed leukemia. These results and those of previous reports support the high specificity of t(8:16) or its variants to the unique M4/M5 type leukemia and the role of a gene on 8p11 in this specific transformation.

Inversion-associated translocations in acute myelomonocytic leukemia with eosinophilia

Cytogenetic studies of three acute myelomonocytic leukemias with bone marrow eosinophilia (M4EO) revealed chromosome 16 inversion associated with additional abnormalities. The inverted chromosome 16 was involved in two patients. Fluorescence in situ hybridization (FISH) experiments with a YAC probe detecting inv(16) showed that the translocation breakpoints involving chromosome 16 did not implicate the inversion breakpoints. FISH can thus distinguish between true variant translocations and translocations with other breakpoints on chromosome 16 in M4EO.

Cytophagocytosis by the blast cells in acute myeloid leukemia

The occurrence of cytophagocytosis as spontaneous ingestion of cells by blast cells has been poorly investigated in acute leukemia. Cytophagocytosis by blasts in acute myeloid leukemia (AML) was observed in eleven patients who represent 1% of AML cases seen in our institution (one M1, two M2, four M4 and four M5). Prominent features of cytophagocytosis by AML blasts are particularly evident in leukemias involving monocytic cells and were more obvious in the bone marrow than the peripheral blood. AML of the monocytic type with cytophagocytosis are frequently associated with cytogenetic aberrations involving chromosomes 8 and 16. Finally the poor outcome of AML patients with cytophagocytosis and their poor response to therapy and short survival is stressed.

The human beta 2 integrin CD18 promoter consists of two inverted Ets cis elements

To define the minimal promoter responsible for expression of CD18 in myeloid and lymphoid cells, we generated 5' and 3' deletion constructs of a segment extending 785 bp upstream and 19 bp downstream of a major transcription start site and determined their effects on driving expression of the luciferase reporter gene in transfected hematopoietic cell lines. A region extending from nucleotides (nt) -302 to +19 was sufficient for cell-restricted and phorbol ester-inducible expression. DNase I footprinting of this region revealed two adjacent protected segments extending from nt -81 to -68 (box A) and -55 to -41 (box B). When a construct of 47 nt in length containing box A and box B and lacking other 3' or 5' elements was cloned into a promoterless vector, it conferred tissue-specific and phorbol ester-inducible expression. Gel retardation revealed that the protein components of two major protein-DNA complexes that form on both box A and box B and are required for transcriptional activation are members of the Ets oncoprotein family; one is related to the GA-binding protein (GABP), and the other is related to PU.1/Spi-1. The minimal CD18 promoter, lacking TATA, CAAT, and initiator elements and consisting primarily of Ets repeats, may exemplify an emerging class of promoters with which the concerted binding of Ets factors is necessary and sufficient to mediate transcriptional activation through direct recruitment of the basal transcription machinery.

The human beta 2 integrin CD18 promoter consists of two inverted Ets cis elements

To define the minimal promoter responsible for expression of CD18 in myeloid and lymphoid cells, we generated 5' and 3' deletion constructs of a segment extending 785 bp upstream and 19 bp downstream of a major transcription start site and determined their effects on driving expression of the luciferase reporter gene in transfected hematopoietic cell lines. A region extending from nucleotides (nt) -302 to +19 was sufficient for cell-restricted and phorbol ester-inducible expression. DNase I footprinting of this region revealed two adjacent protected segments extending from nt -81 to -68 (box A) and -55 to -41 (box B). When a construct of 47 nt in length containing box A and box B and lacking other 3' or 5' elements was cloned into a promoterless vector, it conferred tissue-specific and phorbol ester-inducible expression. Gel retardation revealed that the protein components of two major protein-DNA complexes that form on both box A and box B and are required for transcriptional activation are members of the Ets oncoprotein family; one is related to the GA-binding protein (GABP), and the other is related to PU.1/Spi-1. The minimal CD18 promoter, lacking TATA, CAAT, and initiator elements and consisting primarily of Ets repeats, may exemplify an emerging class of promoters with which the concerted binding of Ets factors is necessary and sufficient to mediate transcriptional activation through direct recruitment of the basal transcription machinery.

Identification of cell-specific and developmentally regulated nuclear factors that direct myeloid and lymphoid expression of the CD11a gene

Human CD11a/CD18 is a noncovalently associated heterodimeric receptor expressed exclusively on the surface of lymphocytes and myeloid cells. To begin to understand the mechanisms that direct the expression of the genes encoding this receptor, we have cloned and characterized the promoter region of the CD11a gene and localized cis-acting elements involved in its expression in lymphoid and myeloid cells. One such element is the "LYM" box, which interacts with two sets of DNA-binding activities, one primarily expressed in lymphocytes and preerythroid cells and the other expressed predominantly in myeloid cells. A second element required for expression of the CD11a gene contains the "GAGA" sequence RRRGAGGAAG (R indicates a purine), which interacts with the DNA-binding activities MS-1 and MS-2. MS-1 is expressed exclusively in myeloid cells and probably represents a member of the Ets family of transcription activators. MS-2 is present in epithelial, preerythroid, and lymphoid cells but is only detected in myeloid cells after differentiation. MS-2 also binds to a second element within the CD11a promoter and homologous elements present in the promoter regions of the CD11b and CD43 genes. Since MS-2 interacts with a number of different gene promoters and is developmentally regulated in myeloid cells, it may play a major role in regulating myeloid gene expression.

Inversion of chromosome 16 and bone marrow eosinophilia in a myelomonocytic transformation of chronic myeloid leukemia

We report a case of chronic myeloid leukemia (CML) in myelomonocytic transformation associated with bone marrow (BM) eosinophilia. At diagnosis, all BM cells showed a Ph chromosome. At the time of blastic phase, more than 50% of Ph+ cells had a pericentric inversion of chromosome 16, inv(16)(p13q22). This case confirms that blastic transformation of CML can involve any committed progenitor, and myelomonocytic leukemia with BM eosinophilia is specifically associated with rearrangement of chromosome 16 at band p13 and q22.

Acute myelomonocytic leukemia with marrow eosinophilia showing 5q- and 16q22 mosaicism

We report an 82-year-old Japanese female with acute myelomonocytic leukemia with dysplastic marrow eosinophilia (FAB M4Eo) exhibiting a partial deletion of the long arm of chromosome 5, del(5)(q13q31) and a derivative chromosome 16 with a breakpoint at band 16q22, in addition to 5q-. The patient had a history of a preleukemic phase for several months with marked dysplasia in trilineage marrow cells, in addition to leukemic features compatible with M4Eo. These findings strongly suggested that the leukemic cells in this case were derived from a preleukemic clone with a del(5q).

The promoter of the CD11b gene directs myeloid-specific and developmentally regulated expression

Human CD11b/CD18 (complement receptor type 3) is a member of the beta 2 integrin subfamily which also includes the heterodimers CD11a/CD18 and CD11c/CD18. The CD11 molecules and the common CD18 are the products of different genes that exhibit distinct though overlapping patterns of tissue- and developmental-specific expression. Whereas expression of CD11b and CD11c is almost exclusively restricted to cells of the myeloid lineage, that of CD11a and CD18 is panleukocytic. To begin to understand the mechanisms by which expression of these gene products is restricted to leukocytes and leukocyte subpopulations and to elucidate the mechanisms by which their expression is coordinated, we have cloned and characterized the promoter region of the CD11b gene. A single transcription initiation site has been identified and the region extending 242 base pairs upstream and 71 base pairs downstream of this site has been shown to be sufficient to direct tissue-, cell-, and development-specific expression in vitro, which mimics that of the CD11b gene in vivo. Within this region there are potential binding sites for transcription factors known to be involved in hematopoietic-specific and phorbol ester-inducible gene expression. Further analysis of this region of the CD11b gene and comparison with the promoters of the CD11a, CD11c, and CD18 genes should lead to significant insights into the molecular mechanisms by which these genes are regulated during hematopoietic development and upon activation.

Chromosomal abnormalities in childhood acute nonlymphocytic leukemia (M4)

A new reciprocal, apparently balanced translocation between chromosomes 7 and 22, i.e., t(7;22)(p22;q13), in association with inv(16)(p13q22) in a child with acute nonlymphocytic leukemia (M4) is reported. Five percent of her bone marrow cells contained both of these aberrations while 90% of her cells have the pericentric inversion of chromosome 16 as the sole abnormality. A clonal evolution of the unusual cell line may be associated with atypical clinical presentation. The presence of inversion 16 in adults has a better prognosis as compared with children. A concise review on the cytogenetic findings in children with ANLL(M4) is also provided.

Acute monoblastic leukemia (FAB-M5b) with t(8;14)(p11;q11.1)

A case of acute monocytic leukemia (FAB-M5b) expressing natural killer cell-associated antigens containing a t(8;14)(p11;q11.1) is presented. We interpret this translocation to represent a variant of the t(8;16) previously reported in FAB-M5b. These findings support the contention that the 8p11 breakpoint site is the critical junction in the oncogenesis of acute monoblastic leukemia with differentiation.

State of the art; the hypereosinophilic syndromes

Many disease states such as parasitic infestations, malignancies, collagen vascular diseases, and allergies are associated with eosinophilia. The diagnosis of idiopathic hypereosinophilic syndrome (HES) requires a persistent elevation in the total eosinophil count (greater than 1500/mm3) for over 6 months, associated organ damage and no detectable underlying cause. This review provides an updated summary of the cytokine cascade that controls eosinophil production and delineates our current understanding of the clinical features of hypereosinophilic states. We also examine the central role of T-lymphocyte activation in eosinophilia, and have attempted to integrate current treatment strategies for HES with the physiology of eosinophilopoiesis.

Acute myelomonocytic leukemia with bone marrow eosinophilia and inv(16)(p13q22),t(1;16)(q32;q22)

A two-year-old girl presenting with de novo acute myelomonocytic leukemia with eosinophilia (French-American-British [FAB] classification, M4Eo) and inv(16)(p13q22), t(1;16)(q32;q22) involving the same chromosome 16 is described. This is the second report of a variant translocation of an inverted chromosome 16 with chromosome 1 at 1q32. However, the segment 1q32----1qter has been exchanged for 16q22----qter and not 16p13----pter, as reported in the previous case. The additional break at 1q32 and the juxtaposition of 1q32----qter onto chromosome 16 could be relevant to the pathogenesis of the disease.

Chromosome 16 abnormalities associated with myeloid malignancies

Twenty-six patients who had cytogenetic analyses performed for myeloid malignancies at St. Vincent's Hospital over a 6-year period were found to have an inversion abnormality of chromosome 16 (25 patients) or t(16;16) (1 patient). Only 16 patients had all the features of M4Eo, while the other 10 patients had diagnoses of M2, M4, M5, RAEB, and RAEB-T; six of these had abnormal eosinophils. Thus, abnormal eosinophils were present in 22 of 26 patients (85%). Thirteen patients had additional cytogenetic abnormalities at diagnosis, the commonest being +8 in 5, del(7q) in 4, and +21 in 3. Twenty-three patients received chemotherapy and 20 (87%) achieved complete remission. The median survival of the treated group was 188 weeks with a 61% 2-year and 45% 5-year survival. No significant difference in survival was observed between those patients with a diagnosis of M4Eo and those with other diagnoses suggesting that it is the abnormality of chromosome 16 which confers an improved prognosis. Additional cytogenetic abnormalities present at diagnosis did not affect prognosis. CNS relapse was observed in only two patients (8%), thus indicating no increased incidence of this complication. This study supports the premise that a chromosome abnormality involving 16p13 and 16q22 defines a good prognosis subset of myeloid leukemia despite morphological variations.

Is trisomy 22 in acute myeloid leukemia a primary abnormality or only a secondary change associated with inversion 16?

In an attempt to confirm the existence of acute myeloid leukemia (AML) with trisomy 22, we studied three patients in whom trisomy 22 imposed as the sole karyotype abnormality. After revision of the karyotypes, however, we were able to identify an inv(16) as the important primary abnormality in all of them. Based on this experience, we investigated whether at least some of the 17 AML cases with trisomy 22 reported so far might possibly have been misinterpreted. Interestingly, ten out of 16 evaluable cases were classified as M4, some of them with bone marrow eosinophilia. As in cases with inv(16), only few metaphases contained trisomy 22. Furthermore, in at least two out of the only four published karyotypes of cases with trisomy 22, an inv(16) is evident and in the other two cases it cannot be ruled out. We therefore believe that at least some of the trisomy 22 cases mentioned in the literature are in fact only secondary changes occurring in AML with an inv(16) and suggest that future reports of AML with trisomy 22 as a specific primary abnormality can only be accepted as such if inv(16) has been excluded with appropriate methods.

Translocation of the MOS gene in a rare t(8;16) associated with acute myeloblastic leukemia and Down syndrome

Cytogenetic analysis of an infant with Down syndrome with concomitant acute myelogenous leukemia revealed a unique t(8;16)(q22;q24). In situ chromosomal hybridization was used to demonstrate that the protooncogene MOS was translocated from chromosome 8 to chromosome 16. This is the first report of the transposition of MOS in association with acute leukemia.

Translocation (8;16)(p11;p13) in patients with acute monocytic leukemias. An evolving syndrome?

The case of a patient with a t(8;16)(p11;p13) chromosomal abnormality and acute myelomonocytic leukemia is described. Review of cases with this translocation showed that 11 of 13 patients had acute monocytic or myelomonocytic leukemia with a high frequency of extramedullary disease and phagocytosis of normal blood cells by the malignant cells. While these patients are not clinically distinct from others with acute monocytic leukemia, the characteristic features of this subset of patients will certainly evolve.

Translocation t(8;16) in acute monocytic leukemia

A report is given of three new cases of acute monocytic leukemia, FAB M5a, with a t(8;16)(p11;p13). Two cases showed a marked erythrophagocytosis, including one with phagocytosis of normoblasts and granulocytes. Phagocytosis was absent in the third case. The t(8;16) was the only abnormality in two cases, whereas one case showed clonal evolution with partial trisomy 1q and a deletion of part of the short arms of chromosomes 1 and 3. Treatment results and survival were poor in all cases. A complete remission was achieved in two patients, which lasted only for 3 and 6 months, respectively. In one of these cases a central nervous system relapse occurred. Survival was short, lasting between 1 and 9 months. One patient succumbed to interstitial pneumonitis, a complication of allogeneic bone marrow transplantation without evidence for relapsing leukemia.

The cytogenetics of childhood leukemia: clinical and biologic implications

Cytogenetic studies have revealed a broad spectrum of abnormalities in the chromosomal make-up of human leukemic cells. These abnormalities are acquired during the process of malignant transformation within the neoplastic clone and reflect the genetic lesions and ablations that have occurred. Because cytogenetic abnormalities are tightly linked to the molecular events that lead to leukemogenesis, it is not surprising that these features correlate with immunophenotypic and morphologic features of the leukemic cells, as well as with the clinical characteristics of children at diagnosis and their responsiveness to therapy. Molecular analysis of the disordered structure or disrupted regulation of genes located at critical chromosomal breakpoints in leukemic cells should continue to provide important insight into normal and aberrant hematopoietic cell function.

Chromosome studies on 30 Chinese patients with acute nonlymphocytic leukemia in Taiwan

Cytogenetic studies were performed on 32 consecutive Chinese patients with de novo acute nonlymphocytic leukemia (ANLL) in Taiwan. Of the 30 patients with adequate specimens, 20(66%) had clonal chromosome abnormalities. Structural rearrangements were detected in 18 of them. Seven (four were children) of the 16 patients with M2 ANLL had t(8;21). All six patients with acute promyelocytic leukemia (APL; M3 subtype) had t(15;17). Two patients with M4 type leukemia and abnormal bone marrow eosinophils had inv(16)(p13q22). Another M4 patient with a mild increase of morphologically normal eosinophils in the bone marrow had an abnormal chromosome #16, t(1;16)(q21;p13) in which 16q22 was not involved. One patient with M5 ANLL had t(9;11). Only two patients had a numerical change as the sole abnormality. None of the patients had loss or deletion of chromosome #5 or loss of chromosome #7, and only one had a deletion of 7q. This study revealed a high incidence of t(8;21), t(15;17), and a low incidence of -5/5q- or -7/7q- in Chinese patients with ANLL.

Abnormal chromosome 16 in clonogenic eosinophils from a case of acute myeloid leukemia (FAB,M2)

A case of acute myeloid leukemia (AML, FAB M2) is described in which the leukemic karyotype showed several numerical and structural cytogenetic abnormalities including an abnormal chromosome 16 with breakpoint at band q22, monosomy for chromosomes 5 and 7, and a single pair of double minute chromosomes. There was no patient history of treatment for a previous malignancy or occupational exposure to mutagens. Bone marrow eosinophilia was seen at presentation for refractory anemia with excess blasts in transformation and when AML was diagnosed. When bone marrow buffy coat cells were cultured in soft agar in the presence of colony stimulating factor, 19% of the colonies and 20% of the clusters were of eosinophils. Cytogenetic examination of pooled eosinophil colonies showed the marker chromosomes that identified the leukemic population.

Chronic myelomonocytic leukemia in a patient with a familial t(6;16)(q13;q22) translocation

A 75-year-old man with chronic myelomonocytic leukemia was found to have a constitutional t(6;16)(q13;q22) translocation, as did his healthy daughter. Chromosomal in situ hybridization studies of the daughter's lymphocytes did not indicate translocation-mediated interruption of the metallothionein gene cluster, at 16q22, although this locus has been reported to be involved in the eosinophilic variant of acute myelomonocytic leukemia. Lymphocytes from the daughter and from the patient's brother (who had a normal karyotype), had no increased fragility at 16q22. The findings do not provide evidence for an association between the familial chromosome abnormality and this patient's leukemia.

An increase in basophils in a case of acute myelomonocytic leukaemia associated with marrow eosinophilia and inversion of chromosome 16

A patient with acute myelomonocytic leukaemia (M4 subtype) with pericentric inversion of chromosome 16, inv(16)(p13q22), and a marked basophilia is described. Results from transmission electron microscopy suggested that the basophils were immature. Clinically, although leukaemic cells had a tendency to infiltrate a number of tissues and organs, such as skin, gingiva, liver and lung, the patient was successfully treated with chemotherapy. The increase in basophils accompanied by marrow eosinophilia may be the result of abnormal differentiation of leukaemic cells that have the capacity to differentiate into both the eosinophilic and basophilic pathways.

Nonrandom additional chromosome changes in acute nonlymphocytic leukemia with inv(16)(p13q22)

Five patients with acute nonlymphocytic leukemia and inv(16)(p13q22), all with additional chromosome changes, are reported. Three were diagnosed as having acute myelomonocytic leukemia (FAB-M4), and the other two as having acute monocytic leukemia (FAB-M5b). All five patients had abnormal eosinophils in the bone marrow at diagnosis. Two had a deletion of the long arm of chromosome #7, del(7)(q31), and a trisomy of chromosome #22. These changes have been reported frequently in acute nonlymphocytic leukemia with inv(16), but are extremely rare in leukemias with other specific rearrangements including t(9;22), t(8;21), and t(15;17). Our findings and review of the literature indicate that inv(16) is observed not only in acute myelomonocytic leukemia but also in acute monocytic leukemia, and that del(7q) and +22 are nonrandomly associated with inv(16) as additional abnormalities. No significant differences in the clinical features seem to exist between the patients with only inv(16) and those with inv(16) and additional chromosome changes, except for the lower white blood cell count in the latter group.

Karyotypic evolution in acute myelomonocytic leukemia with pericentric inversion of chromosome 16

A 37-year-old Japanese male patient with acute myelomonocytic leukemia subtype M4 (according to FAB classification) associated with bone marrow eosinophilia and specific chromosome abnormalities: a pericentric inversion of chromosome 16, inv(16)(p13q22); a long arm deletion of chromosome #7, del(7)(q22q34); and a gain of chromosomes #8 and #22 is reported. In addition to the modal karyotype, 47,XY,7q-,inv(16),+22, there were three other clones whose karyotypes were 46,XY,inv(16); 47,XY,inv(16),+22; and 48,XY,+8,inv(16),+22. As these karyotypes were related to each other, the presence of multiple clones indicated that karyotypic evolution had occurred. The karyotypic evolution associated with 7q- has not been reported previously in patients with M4Eo with inv(16).

A unique 8;16 translocation in two infants with poorly differentiated monoblastic leukemia

Acute monoblastic leukemia is nonrandomly associated with abnormalities involving 11q. Two infants, one a neonate and the other 19 months of age, had the same hitherto undescribed karyotypic abnormality, t(8;16)(p11;p13), associated with acute nonlymphocytic leukemia M5a. The older child had an additional translocation, t(10;11)(q11;p15), but the chromosome arms affected were the opposite to those described in acute nonlymphocytic leukemia M5a of childhood. Therefore, it is postulated that genes involved in monocytic differentiation may be situated on 8p11 or 16p13, as well as on 11q.

High resolution gene mapping of the human alpha globin locus

A combination of polymorphic DNA markers, cytogenetic analysis, and in situ hybridisation has been used for the high resolution assignment of the human alpha globin gene cluster on chromosome 16. Multiallelic DNA probes from within the alpha globin cluster were used to determine the number of copies of this locus in three cell lines containing trisomies of the short arm of chromosome 16 and one with a familial inversion, inv(16). The breakpoints in these rearrangements flank the alpha globin locus and locate a shortest region of overlap to 16p13.1. A meiotic crossover was also localised to this band. In situ hybridisation of biotinylated DNA probes to normal and inverted chromosomes 16 [inv(16)(p13.1;q22)] showed hybridisation sites at opposite ends of the chromosomes, consistent with this regional localisation.

Trisomy 22--a new abnormality found in acute leukemia characterized by eosinophilia and monocytoid blasts expressing immature differentiation antigens

Bone marrow cells from three patients with acute myeloid leukemia, with marrow eosinophilia and monocytoid blasts, showed a new nonrandom chromosomal abnormality, trisomy 22. In two patients the classification of leukemia was M4 and in the third patient M2 (FAB classification). Pretreatment bone marrows in these patients revealed 31%, 30%, and 4% eosinophils, respectively. Blast cells isolated from peripheral blood were Ia-positive and expressed immature monocyte lineage antigens (U26, U28, U48) in 26%-92% of cells. All three patients had a population of bone marrow cells characterized by an extra chromosome #22. One patient also had inversion of chromosome #16. Trisomy 22, bone marrow eosinophilia, and monocytoid blasts displaying early monocyte differentiation antigens may represent a new subgroup of patients with acute myeloid leukemia.

Genetics and cytogenetics of pediatric cancers

It is clear that genetic factors play an important role in the development of some human cancers. These factors may be particularly influential in the pediatric age group because environmental exposures have been minimal. Several pediatric solid tumors, including retinoblastoma and Wilms' tumor, are hereditary. Specific constitutional chromosome abnormalities have been found in these patients, thus implicating certain gene regions as being involved in tumorigenesis. Molecular genetic studies have provided insight into the events occurring at the DNA level in these gene regions. The role of genetics in the development of sporadic pediatric malignancies is also beginning to be elucidated as specific acquired chromosome abnormalities are being discovered in the malignant cells of these otherwise karyotypically normal individuals. This paper will review selected hereditary and nonhereditary pediatric cancers that demonstrate the importance of genetic considerations in the diagnosis and management of children with cancer.

Detection of clonal karyotypic abnormalities in most patients with acute nonlymphocytic leukemia examined using short-term culture techniques

Cytogenetic studies using short-term culture methods, both with and without methotrexate synchronization, were performed on 53 consecutive patients with acute nonlymphocytic leukemia. Among 50 patients with adequate specimens, 42 (84%) showed a clonal karyotypic abnormality. Numerical changes were observed in 22 cases. Chromosome #8 was most frequently gained (eight cases), whereas chromosome #7 was most frequently lost (five cases). Structural rearrangements were detected in 35 cases. A 5q- was seen in three cases, 6q- in two, 7q- in four, standard or variant t(8;21) in four, 11p- in two, t(11q23;-) in two, t(15;17) in four, inv(16) in two, and inv(20) in two. In five patients small abnormal clones were observed, which represented less than 10% of the total cells analyzed. In five other patients the sole abnormality detected was a tiny structural rearrangement. There was no significant difference in remission rate or in survival among groups of patients without clonal abnormality, with a mixture of normal and abnormal karyotypes or with only abnormal cells. Patients who showed complex karyotypes (four or more chromosomal alterations) had a very poor prognosis. In contrast, patients with t(8;21) tended to have a favorable survival outlook. A normal karyotype was associated with an intermediate prognosis.

Acute myeloid leukemia with marrow hypereosinophilia and chromosome 16 abnormality

This article reports six cases of acute nonlymphocytic leukemia (ANLL) and an abnormal chromosome #16. All had the same hematologic pattern at diagnosis, i.e., peripheral blood hyperleukocytosis with a high percentage of monocytes and blast cells. The bone marrow showed three different cell populations: (a) myeloblasts, (b) monocytes and promonocytes, and (c) abnormal eosinophils. In three cases, an ultrastructural study confirmed the cytologic data. In all six cases, the diagnosis was acute myelomonocytic leukemia with bone marrow eosinophilia (M4-Eo). All cases showed an abnormal chromosome #16 in the bone marrow cells; in four cases, well-banded chromosomes were obtained, showing a pericentric inversion inv(16)(p13;q22). One patient had a 4-year remission, and another is still in remission 14 months after diagnosis. Three patients relapsed 7, 9, and 20 months after diagnosis. The last patient died soon after diagnosis. Thus, we do not support the hypothesis that patients with M4-Eo ANLL and chromosome #16 abnormality have a favorable prognosis.

Acute nonlymphoblastic leukemia with bone marrow eosinophilia and structural anomaly of chromosome 16

A patient with acute myelocytic leukemia in relapse presented with t(16;21) (p12;q22). Hematologic studies revealed a large number of abnormal eosinophils in the bone marrow. The complexity of chromosome #16 rearrangements associated with acute nonlymphocytic leukemia and the possible significance of chromosomes #16 and #21 in relation to the concomitant eosinophilia are briefly discussed.