Human herpesvirus 6 reactivation on the 30th day after allogeneic hematopoietic stem cell transplantation can predict grade 2-4 acute graft-versus-host disease.

BACKGROUND: Viral infections and their occult reactivation occasionally cause not only organ damage, but also exacerbation of acute graft-versus-host disease (aGVHD), which may increase transplantation-related mortality synergistically. To determine correlations between viral reactivation and transplantation-related complications, we performed various viral screening tests on the 30th day after allogeneic hematopoietic stem cell transplantation (HSCT), and assessed the clinical implications. PATIENTS AND METHODS: Between August 2007 and January 2013, 49 patients (37 men, 12 women) underwent HSCT in our hospital. The stem cell sources were bone marrow (n = 21), peripheral blood (n = 13), and cord blood (n = 15). The presence of cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpesvirus (HHV) 6, and HHV7 in plasma samples prospectively collected from HSCT recipients on day 30 after HSCT was assayed by quantitative polymerase chain reaction, and the correlations with transplantation-related complications were evaluated. RESULTS: The positivities of CMV, EBV, HHV6, and HHV7 were 44.9%, 22.4%, 53.1%, and 18.3%, respectively. We analyzed transplantation-related complications, and a significant correlation was found only between HHV6 and grade 2-4 aGVHD from day 30 to day 100 (P < 0.001). Using a receiver operating characteristic curve, the area under the curve was calculated as 0.86 (95% confidence interval [CI], 0.74-0.98) between the viral load (VL) of HHV6 and grade 2-4 aGVHD. The sensitivity and specificity were 79% and 93%, respectively, when a cutoff value of 87 copies/mL was used. In multivariate analysis using the Fine and Gray proportional hazards model, the clinically determined high-risk patients (P = 0.004; hazard ratio [HR], 3.69; 95% CI, 1.52-9.00) and the positivity of HHV6 (P < 0.001; HR, 9.957; 95% CI, 2.68-37.06) were extracted as independent risk factors for the cumulative incidence of grade 2-4 aGVHD on or after post-HSCT day 30. The only risk factor extracted for the elevation of HHV6 VL >87 copies/mL was cord blood transplantation (P = 0.0032; odds ratio, 7.10; 95% CI, 1.98-30.00). CONCLUSION: All of the risk factors previously reported to predict severe aGVHD were obtained only during, but not after, HSCT. Our study suggests that the reactivation of HHV6 (≥ 87 copies/mL) at 30 days after HSCT is a possible predictive marker for grade 2-4 aGVHD on or after post-HSCT day 30.

Fusion of the nucleoporin gene NUP98 to HOXA9 by the chromosome translocation t(7;11)(p15;p15) in human myeloid leukaemia.

Expression of Hoxa7 and Hoxa9 is activated by proviral integration in BXH2 murine myeloid leukaemias. This result, combined with the mapping of the HOXA locus to human chromosome 7p15, suggested that one of the HOXA genes might be involved in the t(7;11)(p15;p15) translocation found in some human myeloid leukaemia patients. Here we show that in three patients with t(7;11), the chromosome rearrangement creates a genomic fusion between the HOXA9 gene and the nucleoporin gene NUP98 on chromosome 11p15. The translocation produces an invariant chimaeric NUP98/HOXA9 transcript containing the amino terminal half of NUP98 fused in frame to HOXA9. These studies identify HOXA9 as an important human myeloid leukaemia gene and suggest an important role for nucleoporins in human myeloid leukaemia given that a second nucleoporin, NUP214, has also been implicated in human myeloid leukaemia.

The t(7;11)(p15;p15) translocation in acute myeloid leukaemia fuses the genes for nucleoporin NUP98 and class I homeoprotein HOXA9.

The t(7;11)(p15;p15) translocation is a recurrent chromosomal abnormality associated primarily with acute myeloid leukaemia (FAB M2 and M4). We present here the molecular definition of this translocation. On chromosome 7 positional cloning revealed the consistent rearrangement of the HOXA9 gene, which encodes a class I homeodomain protein potentially involved in myeloid differentiation. On chromosome 11 the translocation targets the human homologue of NUP98, a member of the GLFG nucleoporin family. Chimaeric messages spliced over the breakpoint fuse the GLFG repeat domains of NUP98 in-frame to the HOXA9 homeobox. The predicted NUP98-HOXA9 fusion protein may promote leukaemogenesis through inhibition of HOXA9-mediated terminal differentiation and/or aberrant nucleocytoplasmic transport.

Telomere length shortening in patients with dementia with Lewy bodies.

BACKGROUND AND PURPOSE: Shortened telomere length has been considered to be associated with various age-related diseases, especially in dementia such as Alzheimer's disease and vascular dementia. However, changes in telomere length in dementia with Lewy bodies (DLB) remain unclear. To elucidate these changes, we set out to determine telomere length in peripheral leukocytes as well as the level of urinary 8-hydroxy-deoxyguanosine (8-OHdG) as a marker of oxidative stress in DLB. METHODS: Blood samples were obtained from 33 patients with a clinical diagnosis of probable DLB and 35 age-matched, non-demented elderly controls (NEC). Telomere length was assessed by quantitative real-time polymerase chain reaction of genomic DNA extracted from leukocytes, whereas oxidative stress was assessed on the basis of urine 8-OHdG level, which was measured using high-performance liquid chromatography. RESULTS: Telomere length was significantly shorter in the DLB group than in the NEC group. Urinary 8-OHdG levels were significantly higher in the DLB group than in the NEC group. There was a negative correlation between telomere length and age in the DLB group; however, there were no significant relationships between telomere length and clinical findings including disease duration, severity of cognitive decline, presence or absence of fluctuation in cognitive function, visual hallucinations, and Parkinsonism. In both groups, the correlation between telomere length and urinary 8-OHdG levels was not significant. CONCLUSIONS: These findings indicate that the etiopathology of DLB is considered to be an accelerated aging process.

Identification and functional signature of genes regulated by structurally different ABL kinase inhibitors.

Dasatinib is an ATP-competitive, multi-targeted SRC and ABL kinase inhibitor that can bind BCR-ABL in both the active and inactive conformations. From a clinical standpoint, dasatinib is particularly attractive because it has been shown to induce hematologic and cytogenetic responses in imatinib-resistant chronic myeloid leukemia patients. The fact because the combination of imatinib and dasatinib shows the additive/synergistic growth inhibition on wild-type p210 BCR-ABL-expressing cells, we reasoned that these ABL kinase inhibitors might induce the different molecular pathways. To address this question, we used DNA microarrays to identify genes whose transcription was altered by imatinib and dasatinib. K562 cells were cultured with imatinib or dasatinib for 16 h, and gene expression data were obtained from three independent microarray hybridizations. Almost all of the imatinib- and dasatinib-responsive genes appeared to be similarly increased or decreased in K562 cells; however, small subsets of genes were identified as selectively altered expression by either imatinib or dasatinib. The distinct genes that are selectively modulated by dasatinib are cyclin-dependent kinase 2 (CDK2) and CDK8, which had a maximal reduction of <5-fold in microarray screen. To assess the functional importance of dasatinib regulated genes, we used RNA interference to determine whether reduction of CDK2 and CDK8 affected the growth inhibition. K562 and TF-1BCR-ABL cells, pretreated with CDK2 or CDK8 small interfering RNA, showed additive growth inhibition with imatinib, but not with dasatinib. These findings demonstrate that the additive/synergistic growth inhibition by imatinib and dasatinib may be mediated in part by CDK2 and CDK8.

Unbalanced translocation der(1;7)(q10;p10) defines a unique clinicopathological subgroup of myeloid neoplasms.

The unbalanced translocation, der(1;7)(q10;p10), is one of the characteristic cytogenetic abnormalities found in myelodysplastic syndromes (MDS) and other myeloid neoplasms. Although described frequently with very poor clinical outcome and possible relationship with monosomy 7 or 7q- (-7/7q-), this recurrent cytogenetic abnormality has not been explored fully. Here we analyzed retrospectively 77 cases with der(1;7)(q10;p10) in terms of their clinical and cytogenetic features, comparing with other 46 adult -7/7q- cases without der(1;7)(q10;p10). In contrast with other -7/7q- cases, where the abnormality tends to be found in one or more partial karyotypes, der(1;7)(q10;p10) represents the abnormality common to all the abnormal clones and usually appears as a sole chromosomal abnormality during the entire clinical courses, or if not, is accompanied only by a limited number and variety of additional abnormalities, mostly trisomy 8 and/or loss of 20q. der(1;7)(q10;p10)-positive MDS cases showed lower blast counts (P<0.0001) and higher hemoglobin concentrations (P<0.0075) at diagnosis and slower progression to acute myeloid leukemia (P=0.0043) than other -7/7q- cases. der(1;7)(q10;p10) cases showed significantly better clinical outcome than other -7/7q cases (P<0.0001). In conclusion, der(1;7)(q10;p10) defines a discrete entity among myeloid neoplasms, showing unique clinical and cytogenetic characteristics.

Telomerase inhibition with a novel G-quadruplex-interactive agent, telomestatin: in vitro and in vivo studies in acute leukemia.

The telomerase complex is responsible for telomere maintenance and represents a promising neoplasia therapeutic target. Recently, we have demonstrated that treatment with a G-quadruplex-interactive agent, telomestatin reproducibly inhibited telomerase activity in the BCR-ABL-positive leukemic cell lines. In the present study, we investigated the mechanisms of apoptosis induced by telomerase inhibition in acute leukemia. We have found the activation of caspase-3 and poly-(ADP-ribose) polymerase in telomestatin-treated U937 cells (PD20) and dominant-negative DN-hTERT-expressing U937 cells (PD25). Activation of p38 mitogen-activated protein (MAP) kinase and MKK3/6 was also found in telomestatin-treated U937 cells (PD20) and dominant-negative DN-hTERT-expressing U937 cells (PD25); however, activation of JNK and ASK1 was not detected in these cells. To examine the effect of p38 MAP kinase inhibition on growth properties and apoptosis in telomerase-inhibited cells, we cultured DN-hTERT-expressing U937 cells with or without SB203580. Dominant-negative-hTERT-expressing U937 cells stopped proliferation on PD25; however, a significant increase in growth rate was observed in the presence of SB203580. Treatment of SB203580 also reduced the induction of apoptosis in DN-hTERT-expressing U937 cells (PD25). These results suggest that p38 MAP kinase has a critical role for the induction of apoptosis in telomerase-inhibited leukemia cells. Further, we evaluated the effect of telomestatin on the growth of U937 cells in xenograft mouse model. Systemic intraperitoneal administration of telomestatin in U937 xenografts decreased tumor telomerase levels and reduced tumor volumes. Tumor tissue from telomestatin-treated animals exhibited marked apoptosis. None of the mice treated with telomestatin displayed any signs of toxicity. Taken together, these results lay the foundations for a program of drug development to achieve the dual aims of efficacy and selectivity in vivo.

Telomerase activity in lung cancer cells obtained from bronchial washings.

BACKGROUND: Telomerase, a ribonucleoprotein enzyme that functions in the maintenance of telomeres (specialized structures at the ends of chromosomes), has been reported to be a novel diagnostic marker for malignant diseases. We sought to determine whether measurement of telomerase activity in bronchial washings is of value in the diagnosis of lung cancer. METHODS: Extracts of cells in bronchial washings were analyzed for telomerase activity by use of a telomeric repeat amplification protocol (TRAP) assay. Telomerase activity inside cells was evaluated by use of an in situ TRAP assay. The results of both TRAP assays were compared with those obtained from cytologic examination, which employed standard Papanicolaou staining. RESULTS: When results from the two TRAP assays were combined, telomerase activity was detected in bronchial washings from 18 (82%; 95% confidence interval [CI] = 60%-95%) of 22 patients with lung cancer. In contrast, cancer cells were detected by cytologic examination in the bronchial washings of nine (41%; 95% CI = 21%-64%) of the same 22 patients, a statistically significant difference (two-sided P = .0061). In patients with lung cancer, telomerase-positive cells could be detected in bronchial washings irrespective of tumor location--11 of 14 (79%; 95% CI = 49%-95%) peripheral cancerous lesions and seven of eight (88%; 95% CI = 47%-100%) central cancerous lesions were detected by use of TRAP assays (for comparison, two-sided P = .5349). CONCLUSIONS: A high percentage of patients with lung cancers had detectable telomerase activity in bronchial washings. Thus, the use of a cell extract-based or an in situ TRAP assay in addition to cytologic examination may make the diagnosis of lung cancer more reliable.

Cytogenetic characterization of putative human myeloblastic leukemia cell lines (ML-1, -2, and -3): origin of the cells.

Cytogenetic studies were performed on ML cell lines (ML-1, -2, and -3), as well as on the leukemic cells of a patient from whom the ML cells were derived. The ML-1 cell line showed numerical and structural cytogenetic changes, i.e., -Y, 1p-, 6q-, 11q-, +12, +13q+, 14q-, and 17q-. The ML-2 cell line had two copies of the 13q+, whereas the ML-3 cells contained three clones, i.e., 47,X,-Y,1p-,6q-,11q-,+12,+13q+, 48,X,-Y,1p-,6q-,+6q-,11q-,+12,+13q+, and 49,X,-Y,1p-,6q-,+6q-, 11q-,+12,+13q+,+13q+. The neoplastic cells, when the patient was diagnosed as having T-cell malignant lymphoma (Stage IV), had the 11q- and 13q+. The leukemic cells in a subsequent acute myeloid leukemia phase of this patient contained structural (1p- and 6q-) and numerical (+12, -Y and +2D-group chromosomes: two 13q+) changes in addition to the 11q-. These findings suggest that the acute myeloid leukemic cells of this patient probably originated from the neoplastic cells of the preceding T-cell lymphoma, and that the chromosome changes originally seen in the lymphoma cells were preserved in the established ML cell lines, though the cells of these lines had myeloid characteristics.

Methylation status of T-cell receptor beta-chain gene in B precursor acute lymphoblastic leukemia: correlation with hypomethylation and gene rearrangement.

Epigenetic changes may play a role in genetic alterations in cancer cells, but little is known about this phenomenon. In this study we examined the correlation between rearrangement and methylation status of the T-cell receptor (TCR) beta-chain gene in 23 patients with B precursor acute lymphoblastic leukemia (ALL). In B precursor ALL, all patients had a CCmeGG sequence in the C beta 2 region, a pattern similar to that observed in normal mature B-cells. Approximately 55% of patients with B precursor ALL exhibiting a hypomethylated CCGG sequence at the J beta 1 region showed rearrangement of this region. Furthermore, the same allele of rearranged J beta 1 always contained an unmethylated sequence in the region, although another allele without rearrangement contained methylated J beta 1. By contrast, none of the patients had a rearrangement in the J beta 1 region without hypomethylation. Therefore, rearrangement of the J beta 1 region may link to the hypomethylation status of this region. A close association between hypomethylation of the J beta 1 region may promote accessibility to a putative common recombinase to produce TCR J beta 1 rearrangement. In contrast, about 45% of patients with a hypomethylated J beta 1 did not show rearrangement in this region, thus allowing categorization of B precursor ALL patients into subtypes, according to the combination of TCR beta-chain gene rearrangement and hypomethylation status, especially in the J beta 1 region.

Recurrent chromosome changes at 3p21 in Epstein-Barr virus-transformed cells derived from human prolymphocytic leukemia.

Cytogenetic studies of Epstein-Barr virus-transformed lymphoblastoid cells obtained from a patient with prolymphocytic leukemia revealed the cells to contain recurrent chromosome aberrations involving band 3p21. The in vivo leukemic cells from which the cell lines originated contained a der(3)t(3;17?)(p21;q11?) and a der(13)t(13;3)(q34;p21), as well as numerical (-Y, -8, and -17) and other structural [8p- and der(8)t(8;?)(q13?;?)] changes. The cells in established culture showed additional chromosome aberrations involving band 3p21 of the previously normal and abnormal chromosomes 3. After 200 days of culture, the cells contained a new translocation, i.e., t(3;14)(p21;q32). The cells showed further chromosomal breakage and reunion at band 3p21 at later passages. The affected chromosomal band (3p21) is close to one of the constitutive fragile sites, i.e., 3p14.2. Northern blot analysis of the messenger RNA of the cultured cells did not show an increased or altered expression of the c-raf-1 protooncogene (located at 3p25) when compared with the mRNA of Epstein-Barr virus-transformed lymphoblastoid cell lines from normal subjects with a normal karyotype. Also, the established cells did not show DNA rearrangements or RNA alterations of the c-myc gene.

Loss of a Hu-ets-1 allele in human leukemia cell lines ML-1, -2, and -3 with a chromosome change at 11q24.

The ML cell lines (ML-1, -2, and -3) were derived from the cells of a patient with T-cell malignant lymphoma who developed acute myeloblastic leukemia and whose cells showed a primary chromosome change at band 11q24. Surface marker studies of the ML cells showed that they had both myeloid (MCS-1, MCS-2, and OKM-1) and some T-lymphocyte (3A1/Leu-9 and OKT-4/Leu-3a) characteristics. Molecular studies on these lines were performed in order to determine the possible involvement of the Hu-ets-1 gene, since it is located at band 11q23----q24. All ML cell lines showed half the intensity of the Hu-ets-1 DNA bands as compared to those of controls (karyotypically normal B-cell lines). In contrast, DNAs from leukemia cells with t(4;11)(q21;q23) or t(1;11)(q21;q23 or q24) showed no rearrangement, deletion, or amplification of the ets-1 gene. These findings indicate that a chromosome region (11q24----qter), including the Hu-ets-1 gene, of the ML cells is deleted as a result of the primary cytogenetic change and that heterogeneity is present in the mechanism of human leukemia involving the 11q23----q24 region.

T-cell receptor beta chain gene rearrangement in acute myeloid leukemia always occurs at the allele that contains the undermethylated J beta 1 region.

The epigenetic phenomenon could play a role in the interaction between chromatin and DNA-binding enzymes, allowing us to consider an association between the phenomenon and gene rearrangement. The correlation between methylation status and rearrangement of the T-cell receptor (TCR) beta chain gene in leukemia cells obtained from patients with acute myeloid leukemia (AML) was examined. All of the AML patients with a TCR-beta rearrangement had hypomethylated CCGG sequences within the J beta 1 region on the rearranged allele, while the germline allele had completely methylated CCmeGG sequence in this region, indicating a strong association between hypomethylation status and rearrangement of the TCR beta chain gene. In the DNA from AML patients with or without a TCR-beta rearrangement, the C beta 2 region contained completely methylated CCmeGG sequences, even though they express T-cell-associated antigens, including CD7; this pattern is quite different from that observed in T-cell neoplasias. Moreover, some AML patients showed a TCR-beta rearrangement without the presence of immunoglobulin heavy-chain gene rearrangement, suggesting that TCR beta chain gene involvement in AML is required for unknown factors other than common recombinase activity.

Telomere shortening associated with disease evolution patterns in myelodysplastic syndromes.

We identified the telomere length at different hematological phases in 16 patients with myelodysplastic syndromes (MDS), showing disease evolution with a conventional Southern blot hybridization using the (TTAGGG)4 probe. The MDS patients studied were classified into three groups according to the pattern of telomere length reduction. The first group had telomere shortening at the time of disease diagnosis. In four of the six MDS patients in this group, the disease progressed within 6 months postdiagnosis and each of them survived for less than 1 year. Moreover, in this group four patients showed a 5q anomaly with or without additional changes, and 50% of patients in this group had complex chromosome abnormalities. The patients in the second group showed reductions in telomere length after disease progression; two of these three patients showed gradual disease progression and had one or two chromosome abnormalities. The third group comprised the remaining seven MDS patients; they showed no telomere reduction by disease evolution. Two patients in this group experienced rapid disease progression. These results may indicate that telomere reduction is linked to disease evolution in some MDS patients, perhaps as a result of genomic instability because patients with complex chromosome abnormalities were clustered in the first group. However, because some MDS patients show disease progression without telomere reduction, genetic changes, including point mutations of certain gene(s), may also contribute to disease progression. We further noted that telomere shortening at the time of MDS diagnosis might indicate a poor MDS prognosis.

Cytological detection of telomerase activity using an in situ telomeric repeat amplification protocol assay.

A previously reported highly sensitive assay for measuring telomerase activity on cell and tissue extracts indicates that most human tumor tissues, but not cells adjacent to tumors, have detectable telomerase activity. Although this assay has provided a significant amount of information about the presence or absence of telomerase activity, it does not indicate whether all cells within a tumor have telomerase activity or whether only a subset does. The present report demonstrates the ability to advance this technology to an in situ assay. Using fluorescent telomerase primers and in situ PCR, we show that telomerase activity can be detected at the cellular level. This study demonstrates that telomerase activity is not detected in normal cells but is detected in tumor cells of clinical specimens and in tumor-derived cell lines.

Cytogenetic studies of tumor tissue from patients with nonfamilial renal cell carcinoma.

A method combining an enzymatic technique and short term culture was applied to 27 tumor tissues from 22 patients with nonfamilial renal cell carcinoma in order to establish the chromosome changes in these tumors. Chromosome analyses were successfully carried out in quinacrine mustard-Hoechst 33258 and G-banded preparations of 14 tumors from 12 patients, including 2 cases in which established cell lines were obtained after 43 and 64 days in culture and maintained for 25 and 30 passages in an in vitro system, respectively. The modal chromosome numbers ranged from 38-46 in 11 samples, involving chromosomes in structural and numerical changes and 72 chromosomes in one case, with the remaining 2 samples showing a variety of chromosome numbers. Banding analysis revealed 45 clonal aberrations in 11 tumor samples from 10 patients and nonclonal aberrations in the remaining 3 samples from 2 of the patients. Rearrangements of chromosome 3 were observed in 12 tumors, with the breakpoints on this chromosome almost totally clustered from p11 to p21. In one case both primary and metastatic tumors were studied, and an isochromosome for the long arm of chromosome 1 was observed as clonal in origin in the metastatic tissue. Two cases showed nonclonal changes. The remaining case had one clonal abnormality, i.e., deletion of 6q. Of the remaining 33 clones, chromosomes 1, 2, 6, 11, and 17 were frequently involved. These results suggest that renal cell carcinoma may be cytogenetically classified into 3 categories: (a) tumors with changes of chromosome 3: (b) tumors with other clonal aberrations; and (c) tumors without clonal changes. Rearrangements of chromosome 3 may be possibly associated with the genesis and/or progression of renal cell carcinoma.

A Ki-1 (CD30)-positive T (E+, CD4+, Ia+)-cell line, DL-40, established from aggressive large cell lymphoma.

A new human lymphoma cell line, designated DL-40, was established from the peripheral blood of a 64-year-old woman with leukemic conversion of aggressive large cell lymphoma. The cell line grew in suspension with or without forming clumps of cells and exhibited large, round, or multiple nuclei in the relatively abundant cytoplasm that was positive for acid phosphatase. The cells expressed a Ki-1 antigen (CD30), E+, CD2+, CD4+, CD45+, Ia+ phenotype and had rearranged T-cell receptor beta chain but were negative for CD15, HTLV-I, and Epstein-Barr virus nuclear antigen. Chromosome analysis of this cell line showed a human female karyotype with complex hyperdiploid abnormalities. DL-40 cells produced tumors histologically similar to the original lymphoma when transplanted into nude mice and immunosuppressed hamsters. The DL-40 cell line could provide a useful tool for the understanding of biology of the Ki-1-positive non-Hodgkin's lymphoma.

Potential molecules implicated in downstream signaling pathways of p185BCR-ABL in Ph+ ALL involve GTPase-activating protein, phospholipase C-gamma 1, and phosphatidylinositol 3'-kinase.

Constitutive activation of BCR-ABL tyrosine kinase fusion protein has been shown to be an essential step in the pathogenesis of Philadelphia chromosome (Ph)-positive leukemias. We studied the tyrosine phosphorylated proteins which might be involved in the signaling pathway p185BCR-ABL using a Ph-positive acute lymphoblastic leukemia cell line. p185BCR-ABL but not p145c-abl was constitutively phosphorylated on tyrosine in this cell line. p21ras GTPase-activating protein (GAP) was physically associated with p185BCR-ABL, but not with p145c-abl, and GAP-associated proteins p62/p190 were found to be tyrosine-phosphorylated. Furthermore, p185BCR-ABL was also physically associated with phospholipase C-gamma 1 (PLC-gamma) and phosphatidylinositol 3'-kinase (P13-kinase). Concomitantly, both PLC-gamma and p85 subunit of P13-kinase are tyrosine-phosphorylated in the cells with p185BCR-ABL. These data suggest that GAP, GAP-associated proteins, PLC-gamma, and P13-kinase may participate in downstream signaling for p185BCR-ABL tyrosine kinase.

Chromosome change at 16q22 in nonlymphocytic leukemia: clinical implication on leukemia patients with inv(16) versus del(16).

Nineteen patients with inv(16)(p13q22) or del(16) in myeloid leukemia are described. Eight showed inv(16)(p13q22), including one with de novo acute myeloid leukemia (AML-M2) and seven with de novo acute myelomonocytic leukemia (AMML-M4). Additional chromosome changes were detected in five of the cases; the most common change was trisomy 22. All but one of the de novo M2 and M4 leukemia patients with inv(16)(p13q22) showed initial bone marrow eosinophilia (greater than 5%) with basophilic granules. The remaining 11 showed deletion of the long arm of a chromosome no. 16 [del(16)(q22 or q23)]. Eight of the 11 were diagnosed as having chronic myelomonocytic leukemia, three transformed into an acute phase with M4 morphology; none of them gained complete remission. Two of the remaining three patients with del(16) were diagnosed as having M4 leukemia without marrow eosinophilia. The remaining one was a case of M4 leukemia following a myelodysplastic syndrome. The findings indicate that del(16) might be related to chronic myelomonocytic leukemia or leukemia with a prior history of myelodysplastic syndrome without evidence of marrow eosinophilia. On the other hand, inv(16)(p13q22) is highly associated with de novo AML especially AMML-M4 with bone marrow eosinophilia and a favorable prognosis.