In vivo validation of the switch antibody concept: SPECT/CT imaging of the anti-CD137 switch antibody Sta-MB shows high uptake in tumors but low uptake in normal organs in human CD137 knock-in mice

CD137 is an attractive target for cancer immunotherapy, but its expression in normal tissues induces some adverse effects in patients receiving CD137-targeted therapy. To overcome this issue, we developed a switch antibody, STA551, that binds to CD137 only under high ATP concentrations around cells. This study quantified biodistribution of murine switch antibodies in human CD137 knock-in mice to show the viability of the switch antibody concept in vivo. We utilized four antibodies: Sta-MB, Ure-MB, Sta-mIgG1, and KLH-MB. Sta-MB is a switch antibody having the variable region of STA551. The MB is a murine Fc highly binding to murine Fcγ receptor II. Ure-MB has a variable region mimicking the clinically available anti-CD137 agonist antibody urelumab, binding to CD137 regardless of ATP concentration. Sta-mIgG1 has the same variable region as Sta-MB but has the standard murine constant region. KLH-MB binds to keyhole limpet hemocyanin. The four antibodies were radiolabeled with In-111, SPECT/CT imaging was conducted in human CD137 knock-in mice, and the uptake in regions of interest was quantified. 111In-labeled Sta-MB and Sta-mIgG1 showed high uptake in tumors but low uptake in the lymph nodes and spleen in human CD137 knock-in mice. On the other hand, Ure-MB highly accumulated not only in tumors but also in the lymph nodes and spleen. KLH-MB showed low uptake in the tumors, lymph nodes, and spleen. The present study provides evidence that the switch antibody concept works in vivo. Our findings encourage further clinical imaging studies to evaluate the biodistribution of STA551 in patients.

[Successful treatment with L-asparaginase-based combination chemotherapy for refractory T-cell post-transplant lymphoproliferative disorder]

A 31-year-old man underwent kidney transplantation in 1996, and had been on immunosuppressants. In 2005, he presented with discomfort on swallowing. Swelling of the left tonsil and a mediastinal mass were observed. A biopsy of the left tonsil showed a monotonous proliferation of atypical lymphocytes suggesting post-transplant lymphoproliferative disorder (PTLD). The reduction of immunosuppressants did not result in any clinical improvements, and he developed bilateral cervical lymphadenopathy. A biopsy of the cervical lymph node also showed monotonous proliferation of TdT, CD3, CD5, CD7, CD10, and CD34-positive immature cells. T-cell receptor rearrangement, but not EBER, was detected. Based on these findings, monomorphic T-cell PTLD was diagnosed. He was treated with four different chemotherapeutic regimens without any clinical improvements, and the PTLD became leukemic. Chemotherapy consisting of L-asparaginase, vincristine, and dexamethasone (LVD) was then given, which resulted in massive tumor lysis. However, after two courses of LVD, complete remission was achieved. T-cell PTLD is a rare disorder, characterized by its refractoriness to chemotherapy as opposed to B-cell PTLD. Our experience suggests that L-asparaginase-based chemotherapy may improve the prognosis of T-cell PTLD.

Intravascular large B-cell lymphoma with preceding syndrome of inappropriate secretion of antidiuretic hormone

Intravascular large B-cell lymphoma (IVL) is a rare subtype of B-cell lymphoma presenting with neurological and dermatological lesions in addition to generalized symptoms such as fever and malaise. It may also be associated with variable manifestations of affected organs due to extranodal progression predominantly in the lumen of the small vessels. Here, we report a case of IVL with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) as the sole manifestation at the initial presentation. The present case suggests that hormonal disturbances may progress in advance in IVL, before generalized symptoms develop.

Fulminant Epstein-Barr virus (EBV)-associated T-cell lymphoproliferative disorder with hemophagocytosis following autologous peripheral blood stem cell transplantation for relapsed angioimmunoblastic T-cell lymphoma

Post-transplant lymphoproliferative disorder (PTLD) is a complication that can develop after either solid-organ or hematopoietic stem cell transplantation (HSCT). T-cell PTLD is a rare disorder, especially following autologous HSCT. Here we report a case of T-cell PTLD which occurred after autologous peripheral blood stem cell transplantation (PBSCT) for relapsed angioimmunoblastic T-cell lymphoma (AILT). Three months after the transplant, the patient developed fever with elevated plasma Epstein-Barr virus (EBV)-PCR values. The patient subsequently developed pneumonitis, hepatomegaly and marked pancytopenia due to hemophagocytosis. The patient died of multi-organ failure, despite antiviral and steroid pulse therapy. Our post-mortem study confirmed the marked proliferation of EBV-infected T-cells that differed from the original AILT clone and macrophages/histiocytes were observed in the marrow, liver, lymph nodes and lungs. Phagocytosis was most evident in the bone marrow. The patient's AILT remained in complete remission. To the best of our knowledge, this is the first case of fulminant EBV-associated T-cell lymphoproliferative disorder (LPD) following autologous HSCT.

Establishment of a new human acute monocytic leukemia cell line TZ-1 with t(1;11)(p32;q23) and fusion gene MLL-EPS15

Human leukemia cell lines are of great value in investigating basic and applied aspects of cell biology and clinical medicine. There have been 37 leukemia cell lines carrying 11q23 translocation and MLL rearrangements; however, cell lines harboring with t(1;11)(p32;q23) have not been established. We report here for the first time a new acute monocytic leukemia (AMoL) cell line with t(1;11)(p32;q23), designated TZ-1, and herein describe its biological characteristics. Mononuclear cells isolated from the ascites from a patient with AMoL (French-American-British classification; acute myeloid leukemia M5a) were isolated and passaged by liquid culture medium for a year. TZ-1 cells revealed typical monocytic features in morphology and had a t(1;11)(p32;q23) translocation. The immunoprofiling as determined by flow cytometry showed that TZ-1 cells are positive for myeloid and monocytic markers with lymphoid-associated markers. Fluorescence in situ hybridization and reverse transcription-polymerase chain reaction analyses revealed MLL-EPS15 fusion transcript and protein. Taken together, these results suggest that TZ-1 is a new monocytic leukemia cell line with t(1;11) translocation and fusion gene MLL-EPS15. The established cell line, TZ-1, could provide a valuable model in the analysis of the pathogenesis of MLL-EPS15-positive leukemia and in the development of new agents for this type of leukemia.

Monocyte-derived CXCL7 peptides in the marrow microenvironment

The marrow microenvironment consists of several different interacting cell types, including hematopoietic-derived monocyte/macrophages and nonhematopoietic-derived stromal cells. Gene-expression profiles of stromal cells and monocytes cultured together differ from those of each population alone. Here, we report that CXCL7 gene expression, previously described as limited to the megakaryocyte lineage, is expressed by monocytes cocultured with stromal cells. CXCL7 gene expression was confirmed by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and secretion of protein was detected by enzyme-linked immunosorbent assay (ELISA) and Western blot. At least 2 stromal-derived activities, one yet to be identified, were required for optimal expression of CXCL7 by monocytes. NAP-2, the shortest form of CXCL7 detected in the coculture media, was confirmed to decrease the size and number of CFU-Meg colonies. The propeptide LDGF, previously reported to be mitogenic for fibroblasts, was not secreted by stimulated monocytes. The recombinant form of LDGF produced in a prokaryotic expression system did not have biologic activity in our hands. The monocytic source of CXCL7 was also detected by immunohistochemistry in normal bone marrow biopsies, indicating an in vivo function. We conclude that stromal-stimulated monocytes can serve as an additional source for CXCL7 peptides in the microenvironment and may contribute to the local regulation of megakaryocytopoiesis.

Plasma cell leukemia presenting with diplopia due to unilateral abducens paralysis and complex chromosomal abnormalities

Involvement of cranial nerves is rare in plasma cell leukemia (PCL). Here, we report a case of PCL presenting with unilateral abducens paralysis. Cranial magnetic resonance imaging (MRI) disclosed a mass in the sphenoid sinus. Although the patient showed an initial response to chemotherapy, he died of disease progression 5 months later. Cytogenetic analysis showed translocation of chromosomes 11 and 14, t(11;14) (q13;q32), with additional complex abnormalities. This case implies an association between clinical manifestations and chromosomal abnormalities.

Multilineage involvement of light microscopic myeloperoxidase-negative acute leukemia

The classification of acute leukemia has traditionally been based on a combination of morphology and cytochemical staining data, including myeloperoxidase (MPO) reaction; however, a recent World Health Organization (WHO) classification entails use of cytogenetic and molecular findings in addition to the classic morphological and immunophenotypic analyses. Nevertheless, there have been rare cases in which blastic cells show multilineage phenotypes. These cases may be classified as acute leukemia of ambiguous lineage in the recent WHO classification. We report the case of a 49-year-old man with acute leukemia with multilineage phenotypes. Morphological findings led to a diagnosis of acute myeloid leukemia M2 by the French-American-British classification, but at light microscopy the results of MPO staining were negative for blast cells. In contrast, results of reverse transcription polymerase chain reaction and fluorescence-activated cell sorter analyses were positive for expression of MPO messenger RNA and protein. The blast cells expressed CD4, CD19, CD22, CD33, CD38, CD79a, and HLA-DR and showed rearrangement of the immunoglobulin heavy chain and TCR-3 genes. Results of immunoelectron microscopic analysis of the blast cells were positive for MPO, CD19, CD33, CD34, CD38 and glycophorin A but not for platelet peroxidase. According to these results, the blast cells had at least 4 lineage phenotypes. We concluded that the multiparameter analyses conducted in this case, including immunological and ultrastructural assays, were important in arriving at the appropriate diagnosis of acute leukemia of ambiguous lineage in the new WHO classification.

IgD myeloma with systemic amyloidosis with chest discomfort as an initial symptom

A 53-year-old man was admitted to Keio University Hospital because of serious dyspnea and edema of the lower extremities. Eighteen months previously, the patient had complained of chest discomfort, and was then admitted for the first time to our hospital for evaluation of chest pain. Electrocardiography showed poor R wave progression in leads Vl through V4, and diffuse nonspecific ST-segment and T wave abnormalities with low voltage. However, no definitive diagnosis could be made at this initial admission and a calcium-channel blocker was prescribed. Despite this treatment, the patient was readmitted with worsening dyspnea and lower extremity edema. The diagnosis of heart failure and nephritic syndrome was made at the second admission. In addition, immunoelectrophoresis showed a monoclonal IgD (lambda) M protein and increased plasma cells in the bone marrow, suggesting a diagnosis of multiple myeloma. The patient was thus given dexamethasone (20 mg per day for 4 days) intravenously, but his symptoms did not improve. Two weeks later, the patient deteriorated further with congestive heart failure and renal failure, and subsequently died of cardiac arrest with ventricular fibrillation. On autopsy, IgD (lambda)-positive plasma cell proliferation was found in the bone marrow, confirming the diagnosis of multiple myeloma. In addition, amyloid deposition was detected in various organs including the heart, kidneys, esophagus, duodenum, ileum, colon, tongue, and lungs. In particular, the weight of the heart was 650 g demonstrating a hypertrophic septum and amyloid deposition in the myocardium and even coronary arteries. In summary, the final diagnosis was IgD (lambda) multiple myeloma associated with systemic amyloidosis.

Human marrow stromal cells activate monocytes to secrete osteopontin, which down-regulates Notch1 gene expression in CD34+ cells

The hematopoietic microenvironment, approximated in vitro by long-term marrow cultures (LTCs), consists of both nonhematopoietic-derived stromal elements and hematopoietic-derived monocyte/macrophages. To better understand the consequences of monocyte-stroma interactions, we compared gene expression profiles of CD14+ peripheral blood monocytes and HS-27a stromal cells cultured alone and together in cocultures. Results from 7 separate experiments revealed 22 genes were significantly up- or down-regulated in the cocultures, with osteopontin (OPN) up-regulated more than 15-fold. The microarray OPN data were confirmed by Northern blot, real-time polymerase chain reaction (PCR), and by detection of OPN protein. High levels of OPN gene expression were also detected in 2- to 3-week-old primary LTCs. Using Transwells we determined that stromal cells were secreting a factor that up-regulated OPN gene expression in CD14+ cells. When CD34+ cells were cultured in the presence of purified OPN, tyrosine phosphorylation of a 34-kDa molecule was increased 2- to 3-fold, an effect that was diminished in the presence of an OPN neutralizing monoclonal antibody. In addition, Notch1 gene expression was decreased 5-fold in OPN-treated CD34+ cells. We conclude that interactions between stroma and monocytes can result in activities that limit the role of Notch signaling in hematopoietic regulation.

Telomere shortening in hematopoietic stem cell transplantation: a potential mechanism for late graft failure?

Telomeres serve to maintain the structural integrity of chromosomes, yet each somatic cell division is associated with a decrease in telomere length. The cumulative decrease in telomere length can impose an upper limit for the number of cell divisions that can occur before a cell senesces. When studied in vitro with fibroblasts, this limit is referred to as the Hayflick limit and usually occurs after 40 to 80 cell doublings. In theory, a similar replicative potential in a hematopoietic stem cell could support hematopoiesis in a person for more than 100 years. However, stem cells differentiate, and the telomere length differs among chromosomes within a single cell, among cell types, and among age-matched individuals. This variation in telomere length raises the possibility that long-term hematopoiesis by transplanted stem cells could, depending on the telomere length of the engrafted stem cell and the proliferative demand to which it is subjected, reach a Hayflick limit during the life span of the patient. Although significant shortening of telomeres is reported to occur within the first year posttransplantation, as yet no evidence has indicated that this shortening is associated with marrow function. In this review, we summarize reports on telomere shortening in stem cell transplantation recipients and report 2 cases in which graft failure is associated with significant telomere shortening.

Functional interleukin-7 receptors (IL-7Rs) are expressed by marrow stromal cells: binding of IL-7 increases levels of IL-6 mRNA and secreted protein

DNA spotted microarrays were used to compare gene expression profiles from 2 functionally distinct human marrow stromal cell lines: HS-27a, which supports cobblestone area formation by early hematopoietic progenitors, and HS-5, which secretes multiple cytokines that support the proliferation of committed progenitors. One unexpected result was the high level of interleukin-7 receptor (IL-7R) gene expression in HS-27a stromal cells. Northern blot analysis confirmed the IL-7R RNA expression, and Western blots for the IL-7R protein detected both a full-length (90-kd) IL-7R and a smaller 30-kd fragment in both HS-27a cells and primary stromal cell cultures, whereas only the 90-kd receptor protein was detected in peripheral blood mononuclear cells. Biotinylated IL-7 was shown to bind to HS-27a cells under physiologic conditions, and this binding was inhibited by blocking anti-IL-7 antibodies. Tyrosine phosphorylation of several proteins (55 kd, 30 kd, and 24 kd) in HS-27a cells was rapidly increased after incubation with recombinant IL-7. One of the phosphorylated proteins proved to be the 30-kd IL-7R fragment. Exposure of HS-27a cells to IL-7 resulted in a 10-fold increase in secretion of IL-6 into culture supernatants but no increase in the cytokines stromal cell-derived factor 1, macrophage inflammatory protein 1 alpha, or IL-1 beta. The up-regulation of IL-6 secretion is associated with a rapid but transient increase in detectable levels of IL-6 messenger RNA. These data suggest that IL-7 may function to regulate the milieu of the microenvironment by modulating IL-6 secretion by the IL-7R-expressing stromal elements.

Failure of adult marrow-derived stem cells to generate marrow stroma after successful hematopoietic stem cell transplantation

OBJECTIVE

The existence of adult, marrow-derived stem cells that retain the ability to generate various tissues is an appealing concept that has considerable therapeutic potential. The aim of this study was to test the extent of this proposed plasticity by defining the ability of adult marrow and peripheral blood stem cells to generate stromal cells of the marrow microenvironment.

PATIENTS AND METHODS

We examined expanded populations of stromal cells from four patients 1 to 27 years after allogeneic, sex-mismatched marrow, or peripheral blood stem cell transplantation. The cultured stromal cells were stained by immunofluorescence and with nonspecific esterase (NSE) to detect macrophages, which can constitute a significant component of a primary long-term marrow culture. Fluorescence in situ hybridization (FISH) probes for chromosomes X and Y were applied to distinguish donor from host cells.

RESULTS

FISH analysis of replicate slides indicated a good correlation between the number of NSE(+) cells and the number of donor-derived cells. By applying NSE and FISH to the same cells and capturing both bright-field and epifluorescence images, we confirmed that all donor signals were derived from NSE(+) macrophages.

CONCLUSION

After successful allogeneic stem cell transplantation, the marrow stroma remains host in origin, even after 27 years of 100% donor hematopoiesis.

Novel variant isoform of G-CSF receptor involved in induction of proliferation of FDCP-2 cells: relevance to the pathogenesis of myelodysplastic syndrome

Recent studies have shown that point mutations in granulocyte colony-stimulating factor receptor (G-CSFR) are involved in the pathogenesis of severe congenital neutropenia (SCN) and in the transformation of SCN to acute myelogenous leukemia (AML). It is reasonably speculated that the abnormalities in the signal transduction pathways for G-CSF could be partly responsible for the pathogenesis and the development to AML in patients with myelodysplastic syndromes (MDS). Therefore, we investigated the structural and functional abnormalities of the G-CSFR in 14 patients with MDS and 10 normal subjects. In in vitro colony forming assay, MDS samples showed reduced response to growth factors. However, G-CSF, but not GM-CSF and IL-3, enhanced clonal growth in three cases of high risk patients with MDS (RAEB, RAEB-t, and MDS having progressed to acute myeloid leukemia (AML)) and one low risk patient (RA). Eight out of 14 patients including above 4 patients demonstrated a common deletion of the G-CSFR cDNA; a deletion of three nucleotides (2128-2130) in the juxtamembrane domain of the G-CSFR, which resulted in a conversion of Asn(630)Arg(631) to Lys(630). To assess the functional activities of this deletion in the G-CSFR isoform, a mutant with the same three-nucleotide deletion was constructed by site-directed mutagenesis. FDCP-2 cells expressing the G-CSFR isoform responded to G-CSF, and exhibited proliferative responses than did those cells having wild-type G-CSFR. Moreover, these isoforms showed prolonged activation of STAT3 in response to G-CSF than did the wild-type. These results suggest that the deletion in the juxtamembrane domain of the G-CSFR gives a growth advantage to abnormal MDS clones and may contribute to the pathogenesis of MDS.

CD30 and the NPM-ALK fusion protein (p80) are differentially expressed between peripheral blood and bone marrow in primary small cell variant of anaplastic large cell lymphoma

The t(2;5)(p23;q35) translocation results in the formation of a unique chimeric NPM-ALK protein (p80). Expression of this protein is considered to be one of the clinical features of anaplastic large cell lymphoma (ALCL). Recently recognized as one clinical subtype of ALCL, the small cell variant is prone to have a leukemic presentation. Although the small cell variant has been recognized as a subtype of ALCL, the clinical properties of this subtype, especially the immunophenotype of lymphoma cells in peripheral blood, have not yet been fully described. This report shows that neither CD30 nor p80 is detected by immunostaining in the predominant small cell malignant clone and also in large lymphoma cells in peripheral blood, while large cells and occasionally observed small cells in bone marrow were found to be positive for CD30 and p80. Our findings suggest that differential expression of CD30 and p80 between peripheral blood and bone marrow lymphoma cells is a property of the small cell variant of ALCL.

Establishment of a retinoic acid-resistant human acute promyelocytic leukaemia (APL) model in human granulocyte-macrophage colony-stimulating factor (hGM-CSF) transgenic severe combined immunodeficiency (SCID) mice

To understand the mechanisms and identify novel approaches to overcoming retinoic acid (RA) resistance in acute promyelocytic leukaemia (APL), we established the first human RA-resistant APL model in severe combined immunodeficiency (SCID) mice. UF-1 cells, an RA-resistant APL cell line established in our laboratory, were transplanted into human granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing SCID (hGMTg SCID) mice and inoculated cells formed subcutaneous tumours in all hGMTg SCID mice, but not in the non-transgenic control SCID mice. Single-cell suspensions (UF-1/GMTg SCID cells) were similar in morphological, immunological, cytogenetic and molecular genetic features to parental UF-1 cells. All-trans RA did not change the morphological features of cells or their expression of CD11b. RA did not alter the growth curve of cells as determined by MTT assay, suggesting that UF-1/GMTg SCID cells are resistant to RA. These results demonstrate that this is the first RA-resistant APL animal model that may be useful for investigating the biology of this myeloid leukaemia in vivo, as well as for evaluating novel therapeutic approaches including patients with RA-resistant APL.

Restoration of retinoid sensitivity by MDR1 ribozymes in retinoic acid-resistant myeloid leukemic cells

Complete remission is achieved in a high proportion of patients with acute promyelocytic leukemia (APL) after all-trans retinoic acid (RA) treatment, but most patients relapse and develop RA-resistant APL. We have previously reported that both RA-resistant HL-60 (HL-60R) and APL cells express P-glycoprotein and MDR1 transcripts; and these cells differentiate to mature granulocytes after culture with RA and P-glycoprotein antagonist. Ribozymes have been shown to be able to intercept a target RNA by catalytic activity. To address the role of MDR1 in overcoming RA-resistance in APL cells, we investigated the biologic effects of ribozymes against the MDR1 transcript in HL-60R cells. These ribozymes efficiently cleaved MDR1 mRNA at a specific site in vitro. The 196 MDR1 ribozyme was cloned into an expression vector, and stably transfected (HL-60R/196Rz) cells were obtained. Expression of MDR1 transcripts was decreased in HL-60R/196Rz cells compared with parental HL-60R and empty vector-transfected (HL-60R/neo) cells. Interestingly, RA inhibited cellular proliferation and induced differentiation of HL-60R/196Rz cells in a dose-dependent manner, suggesting reversal of drug resistance in HL-60R cells by the MDR1 ribozyme. These data are direct evidence that P-glycoprotein/MDR1 is responsible in part for acquired resistance to RA in myeloid leukemic cells. The MDR1 ribozyme may be a useful tool for investigating the biology of retinoid resistance and may have therapeutic potential for patients with RA-resistant APL.

Retinoid resistance in leukemic cells

Recent studies have shown that a high proportion of patients with acute promyelocytic leukemia (APL) achieve complete remission after treatment with all-trans retinoic acid (RA). Nevertheless, despite an initial good response, most patients who received continuous treatment with all-trans RA relapsed and develop RA-resistant disease. The detailed mechanisms for this development of RA resistance by APL cells are still unclear. Several possible mechanisms have been considered to explain in vitro resistance to RA. One obvious explanation is the generation of new mutations in the retinoid receptors. However, UF-1 cells (the first permanent APL cell line with RA-resistant features) had no point mutations in the ligand-binding domain of the RAR-alpha gene. Another potential mechanism for clinical RA resistance is the pharmacologic alteration in the metabolism of all-trans RA. Continuous treatment with all-trans RA in APL is associated with a progressive reduction of the plasma concentrations of RA. Induction of cytochrome P-450, cellular RA-binding protein (CRABP) and P-glycoprotein resulted in lower plasma and cellular levels of active retinoids. Thus, acquired resistance to RA may be explained at least in part by drug metabolism in leukemic cells.

Circulating endogenous thrombopoietin, interleukin-3, interleukin-6 and interleukin-11 levels in patients undergoing allogeneic bone marrow transplantation

To elucidate the physiologic role of thrombopoietin (TPO) for hematologic reconstitution following allogeneic bone marrow transplantation (BMT), serum TPO levels as well as interleukin-3 (IL-3), IL-6 and IL-11 were serially measured in 55 samples from 3 patients who underwent allogeneic BMT using an enzyme-linked immunosorbent assay (ELISA). The TPO level was higher in the serum taken during marrow aplasia than in the pretransplant serum. The serum TPO levels and platelet counts showed a strong inverse relationship in all patients examined. We also sequentially measured endogenous serum TPO levels before and within 36 h after platelet transfusions. Endogenous serum TPO levels were inversely correlated with platelet mass following platelet transfusions. Serum levels of IL-3 had no apparent correlation with platelet counts and serum levels of IL-11 remained below the detection levels (31.3 pg/ml) in all samples. Serum levels of IL-6 were high during myeloaplasia and more upregulated in the febrile period. These findings support the view that TPO is the central regulator for megakaryopoiesis in vivo and the rationale for its clinical use after allogeneic BMT.

Serial quantification of minimal residual disease of t(8;21) acute myelogenous leukaemia with RT-competitive PCR assay

The chromosomal translocation (8;21)(q22;q22) in the AML M2 subtype according to the FAB classification, results in the production of a novel fusion gene AML1/ETO. The chimaeric AML1/ETO transcript is useful for the detection of minimal residual disease (MRD). Recently, several studies on the detection of AML1/ETO transcripts in t(8;21) AML have been reported. However, the clinical significance of a small number of AML1/ETO transcripts by a reverse transcription-polymerase chain reaction (RT-PCR) remains to be elucidated. We have developed a novel quantitative RT-competitive PCR assay and evaluated the clinical usefulness of this method by the monitoring of MRD in eight patients with t(8;21) AML. In four patients in first continuous complete remission (CR) the value of MRD was always < 0.1 fg of the competitor dose throughout their courses, whereas in four relapsed patients there was an increase in the value of MRD to > 0.1 fg of the competitor dose before cytogenetic relapse. We conclude that the detection of the presence of cells with AML1/ETO fusion transcripts by our RT-competitive PCR assay may be useful to monitor disease progression and to predict subsequent relapse.

Establishment and characterization of a novel acute promyelocytic leukemia cell line (UF-1) with retinoic acid-resistant features

All-trans retinoic acid (RA) induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL). Nevertheless, most of these patients develop RA resistance and relapse. The mechanisms of RA resistance by APL cells are still unclear. To understand the characteristics of human leukemia, human leukemic cell lines are useful tools for study. APL cells have a strikingly low proliferation potential in vitro; thus, only one APL cell line has been established. We developed a novel APL cell line (UF-1) from a patient clinically resistant to all-trans RA. Cell surface markers in the UF-1 cells were positive for CD7, CD13, CD33, and CD38. Cytogenetic analyses revealed additional abnormalities, 46XX, add(1)(q44), add(6)(q12), add(7)(q36), t(15;17) (q21;q21). Molecular analyses showed a PML/RAR alpha fusion transcript. Sequence analysis of the RAR alpha gene in RA-resistant HL-60 cells disclosed a point mutation in codon 411 (C to T substitution), whereas UF-1 cells showed the normal sequence. All-trans RA did not change morphological features of the cell, NBT reduction activity, or their expression of CD11b antigens as determined by FACS analysis except at 10(-6) mol/L. RA also did not alter the growth curve of the cells as determined by the MTT assay. These findings suggest that the UF-1 cell is the first permanent cell line with spontaneous RA-resistant APL cells. This RA-resistant APL cell line may be a useful model for molecular studies on the block of leukemic cell differentiation and as a means to investigate the mechanisms of RA resistance.

[Erythroblastic transformation of chronic myelogenous leukemia associated with an additional chromosome abnormality translocation (6;9]

A 57-year-old female was diagnosed being in the blastic phase of chronic myelogenous leukemia (CML) on her second admission in May 1993. The patient was previously treated with vincristine and prednisolone in the accelerated phase of CML in December 1991 without improvement. Other chemotherapeutic agents such as BHAC-DMP (enocitabine, daunorubicin, mercaptopurine, prednisolone), interferon, mercaptopurine and ranimustine were also administered. After the second chronic phase was achieved, she was treated with busulfan as an outpatient. On her second admission, the diagnosis of erythroblastic transformation was made, and cytogenetic study revealed t(9;22) (q34;q11) with the additional chromosomal abnormalities, t(6;9) (p23;q34). This karyotype rearrangement has been reported neither in Ph-positive CML nor in blastic crisis.

Serious adverse effects induced by simultaneous administration of two nonsteroidal anti-inflammatory drugs

We have described the case of a 58-year-old woman in whom acute hemolytic anemia, renal failure, and granulocytopenia developed after intake of mefenamic acid and diclofenac. Results of direct and indirect Coombs' tests were negative, but the lymphocyte transformation test was positive for these two nonsteroidal antiinflammatory drugs (NSAIDs). We suggest that the immune complex mechanism could have induced these adverse reactions. Although these drugs are very popular, simultaneous administration should be avoided because serious adverse effects can potentially occur.

[Development of Stevens-Johnson syndrome following sulindac administration in a patient with mixed connective tissue disease]

Nineteen-year-old woman with mixed connective tissue disease developed Stevens-Johnson syndrome following treatment of arthritis using sulindac. Involvements of infectious and malignant diseases have been ruled out and sulindac has strongly been suspected as a causative agent for Stevens-Johnson syndrome. Ten out of 13 cases with Stevens-Johnson syndrome associated with non-steroidal anti-inflammatory drugs, sulindac has been administrated. Four cases also presented with severe liver disease. Patients who developed Stevens-Johnson syndrome following sulindac administration did not have apparent common clinical or laboratory findings which might be implicated for development of this severe side effects. Among the various non-steroidal anti-inflammatory drugs, safety of sulindac has widely been appreciated. However, occurrence of severe adverse events as reported here indicated that sulindac should be administrated as carefully as other non-steroidal anti-inflammatory drugs.

Delineation of the gastric muscularis mucosae and assessment of depth of invasion of early gastric cancer using a 20-megahertz endoscopic ultrasound probe

Using a 20 MHz endoscopic ultrasound system, delineation of the gastric muscularis mucosae and estimation of the depth of malignant invasion was attempted by in vivo scanning during the process of routine endoscopic observation or in vitro scanning of excised sections of 34 early gastric cancers in 32 patients. The muscularis mucosae was visualized as a single hypoechoic layer in 16 of 32 lesions (50%) scanned in vitro. Comparison of lesions in which delineation of the muscularis mucosae was or was not possible revealed no significant differences with respect to either the thickness of the lamina propria and muscularis mucosae or with respect to the degree of inflammatory cell infiltration of the lamina propria or the conditions of the boundary between the lamina propria and the muscularis mucosae. This indicates that improvement of the operability characteristics of the ultrasonic apparatus will be needed to achieve improved delineation of the muscularis mucosae. The accuracy of invasion depth estimation of early gastric cancer was 67% (16 of 24 lesions scanned in vivo) and 73% (8 of 11 lesions) in cases in vivo where the muscularis mucosae and the tumor were delineated on the same screen. The principal factors causing erroneous staging were the presence of dilated benign glandular ducts, ulcer scars, and attenuation of the ultrasound waves.