cDNA sequence and expression of a gene encoding a pyruvate dehydrogenase kinase homolog of Drosophila melanogaster

Pyruvate dehydrogenase is a catalyst for an irreversible step in the degradation of glucose and its activity is regulated by a highly specific protein kinase, pyruvate dehydrogenase kinase (PDK). PDK belongs to a family of mitochondrial protein kinases unique from other eukaryotic protein kinases. We cloned a cDNA encoding a putative PDK from Drosophila melanogaster (DmPDK). The deduced DmPDK consists of 413 amino acids and shares up to 57.8% homology with human and rat PDK isoenzymes. Developmental Northern blot analysis revealed two major transcripts of 2.1 kb and 2.7 kb. The 2.7-kb transcript was expressed throughout ontogeny, whereas the 2.1-kb transcript was specific to embryos and adult females. Whole-mount in situ hybridization revealed that PDK mRNA is ubiquitously distributed in the embryo. The DmPdk gene was cytologically mapped to the 45CD region on the right arm of the second chromosome.

Application of fluorescence in situ hybridization to detect residual leukemic cells with 9;22 and 15;17 translocations

We performed fluorescence in situ hybridization (FISH) upon 9;22 and 15;17 translocation-positive bone marrow cells to monitor the clinical course of 46 patients with chronic myelocytic leukemia (CML) and nine with acute promyelocytic leukemia (AML M3) who received chemotherapy and/or bone marrow transplantation (BMT). M-BCR-ABL and PML-RAR alpha probes were used to detect translocations of t(9;22) and t(15;17), respectively. Signals from CML patients treated with interferon (17 patients) or BMT (29 patients) were 0.5-15% positive for the 9;22 translocation. Among nine M3 patients who received extensive chemotherapy or BMT, 1-5% were positive for the 15;17 translocation. A highly sensitive FISH procedure using both translocation probes and a whole chromosome Y probe was established and applied to eight sex-mismatched BMT patients (seven CML and one AML M3), in which 0.1-0.6% of signals positive for the specific translocations were detected. These results suggested that interphase FISH is powerful enough to identify minor cell populations of 9;22 or 15;17 translocations after therapy, as well as to detect specific chromosome abnormalities at diagnosis.

In vitro effects of a recombinant toxin, mSCF-PE40, targeting c-kit receptors ectopically expressed in small cell lung cancers

Most small cell lung cancers (SCLCs) ectopically express high levels of the c-kit receptor. We have examined if the receptor can serve as a target for a chimeric toxin, mSCF-PE40 composed of murine stem cell factor (SCF) genetically fused to the N terminus of a modified form of Pseudomonas exotoxin (PE) lacking its cell recognition domain. Selective cytotoxicity was found for human c-kit receptor-negative cells. This agent thus warrants further evaluation for therapy of human CSLCs.

Phase I/II trial of cure-oriented high-dose chemoradiotherapy with transplantation of CD34+ peripheral blood stem cells purified by the immunomagnetic bead method for refractory hematological malignancies. Nagoya CD34+ PBSCT Study Group

A multicenter phase I/II clinical trial was conducted to evaluate the safety of a device (Isolex System; Baxter Health Corporation, Irvine, Calif., USA) using the immunomagnetic bead method to purify CD34+ stem cells from peripheral blood and to assess the efficacy and toxicity of high-dose chemoradiotherapy with peripheral blood stem-cell transplantation (PBSCT) using purified CD34+ stem cells in patients with refractory hematological malignancies. Patients eligible for the study included those who had T-cell acute lymphoblastic leukemia (T-ALL), lymphoblastic lymphoma (LBL), mantle-cell lymphoma (MCL), high-risk aggressive non-Hodgkin's lymphoma (NHL), and adult T-cell leukemia/lymphoma (ATLL) in first complete remission (CR) and those who had standard-risk aggressive NHL, indolent lymphoma, Hodgkin's disease, or acute promyelocytic leukemia (APL) in second CR or first partial remission (PR) after the completion of first-line chemotherapy and were chemosensitive to salvage chemotherapy, in whom tumor contamination of harvested peripheral blood stem cells (PBSCs) was possible due to bone marrow or peripheral blood involvement. Lack of CD34 expression by tumor cells was an important selection factor. Eight patients with hematological malignancies (six NHL patients, one ATLL patients, and one APL patient) were enrolled; their median age was 41 years (range 26-49 years). After consolidation and mobilization chemotherapy, two or three courses of apheresis were performed in each patient. After high-dose chemo(radio)therapy, in each patient a median of 1.8 x 10(6) cells/kg (range 8.2 x 10(5)-5.1 x 10(6) cells/kg) purified CD34+ PBSCs were infused; granulocyte colony-stimulating factor was given from day 1. Median times to hematopoietic recovery were as follows: WBC of > or = 1,000/microliter, day 11; platelet count of > or = 50,000/microliter, day 19; and reticulocyte count of > or = 10/1000, day 15. Two NHL patients relapsed at 23 and 9 months after PBSCT, respectively; the remaining six patients are alive and in CR. No severe toxicity was observed in any patient. Tumor contamination as measured using a polymerase chain reaction-mediated RNase protection assay at the 10-4 level was detected in the CD34(+)-purified fractions of 2 of the 5 samples analyzed; however, a reduction in contaminating lymphoma cells from the autograft of at least 1,000 to 10,000 orders of magnitude was achieved by CD34+ selection using the immunomagnetic bead method. High-dose chemoradiotherapy with transplantation of CD34+ PBSCs purified by the immunomagnetic bead method was thus shown to be an active and safe therapy for refractory hematological malignancies with bone marrow or peripheral blood involvement. However, it is too early for evaluation of the long-term survival benefit.

Subcellular localization and protein interaction of the human LIMK2 gene expressing alternative transcripts with tissue-specific regulation

In our efforts to explore possible roles of proteins with a LIM domain, which is a cysteine-rich Zinc-binding motif, in differentiation and oncogenesis in the lung, we have cloned a human LIMK2 gene and identified two alternative transcripts, LIMK2a and LIMK2b, which are probably due to variation in transcriptional initiation. The former encodes a protein containing two LIM domains, a PDZ domain, and a kinase domain, while the latter has only one and half LIM domains. The predominance of the two transcripts appears to be regulated in a tissue-specific manner. Alteration of the regulation is also observed in some cancer cell lines. Transfection studies have shown an association of 63-kDa and 58-kDa proteins with the LIMK2a and LIMK2b protein; the former is distributed in the cytoplasm and nucleus and the latter occurs mainly in the cytoplasm and is scarcely translocated to the nucleus. In contrast, a truncated LIMK2-Kinase has a nuclear location, not showing the protein association.

GB virus C/hepatitis G virus infection among Japanese patients with chronic liver diseases and blood donors

Recently, a novel hepatitis virus, GB virus C/hepatitis G virus (GBV-C/HGV), has been isolated. To elucidate the seroprevalence of chronic GBV-C/HGV infection in Japan and the phylogenetic relationship between Japanese strains and the strains previously reported, serum GBV-C/HGV RNA was detected by reverse transcription polymerase chain reaction (RT-PCR) in 203 patients with chronic liver diseases and 200 samples of voluntary blood donors. RT-PCR was performed with primers derived from the 5'-untranslated region which were conserved between GBV-C and HGV and distant from other flaviviruses including hepatitis C virus (HCV). The nucleotide sequences were determined by the dideoxy chain termination method. The phylogenetic analysis was performed by the neighbor-joining method. In 10 (4.7%) of 203 patients with chronic liver diseases and in 1 (0.5%) of 200 blood donor samples, serum GBV-C/HGV RNA was detected. Of 10 patients, 9 patients were positive for anti-HCV and negative for HBsAg, and 1 patient was positive for HBsAg and negative for anti-HCV. The phylogenetic analysis indicated that there were three major groups which were group 1 (GBV-C), group 2 (HGV), and group 3 (a group of Japanese strains). These data indicated that (1) there was a low prevalence of GBV-C/HGV infection in Japanese patients with chronic liver diseases, (2) a high proportion of patients with GBV-C/HGV infection had chronic HCV infection however, and (3) there were at least three groups in strains of GBV-C/HGV.

[A new strategy for treating small cell lung cancer]

Recent results from molecular biology have shown that lung cancer is characterized by multiple, sequentially appearing molecular changes that include genetic and epigenetic alterations. Among all types of lung cancer, small cell lung cancer (SCLC) is associated with the lowest rate of 5-year survival. In this symposium, we introduce our findings regarding the c-kit oncogenes in SCLC. We found that the c-kit gene is strongly expressed in SCLC. The c-kit gene was not expressed in normal bronchial epithelial cells, which indicates that this gene is abberantly transcribed in SCLC. In addition, c-kit-positive cases of SCLC showed autophosphorylation in response to recombinant human stem cell factor. Furthermore, adding rh stem cell factor of SCLC cell lines induced a significant chemotactic response and moderate in vitro cell growth. These results strongly suggest that abnormal expression of the c-kit gene may be involved in the pathogenesis of SCLC by autocrine/paracrine stimulation via the c-kit/SCF signal pathway. To overcome drug resistance, we assessed the efficacy of a chimeric toxin targeted to c-kit receptors.

Possible prediction of adverse reactions to pyrimidine chemotherapy from urinary pyrimidine levels and a case of asymptomatic adult dihydropyrimidinuria

Deficiency of dihydropyrimidine dehydrogenase or dihydropyrimidinase, enzymes that catalyze the breakdown of pyrimidine chemotherapy agents such as 5-fluorouracil, may cause serious adverse reactions to these agents. We attempted to establish the reference range for urinary pyrimidines in adults to detect individuals with abnormal pyrimidine metabolism. We analyzed urinary pyrimidine levels in 1133 adults to establish a reference range for persons ages 20 years or older. Urinary dihydrouracil and uracil levels were determined by high-performance liquid chromatography with column switching. The reference range obtained was found to be 0-59.3 micromol/g creatinine for dihydrouracil and 0-129.8 micromol/g creatinine for uracil. In addition, an asymptomatic man with suspected dihydropyrimidinase deficiency was detected on the basis of dihydropyrimidinuria. Although only three cases of this disease have been found worldwide, including one infant reported previously by our group, it may not be so rare as has been thought. In this man, a 10 mg/kg oral uracil loading test yielded a peak blood dihydrouracil level of 192.1 micromol/liter and a peak uracil level of 67.8 micromol/liter. Eight h after loading, the uracil level was still 11.1 micromol/liter, about 17 times that in healthy subjects. Additional research on dihydropyrimininase deficiency may help to prevent adverse reactions to pyrimidine chemotherapy agents in susceptible individuals.

11q23 aberration is an additional chromosomal change in de novo acute leukemia after treatment with etoposide and mitoxantrone

We report on 2 patients with acute leukemia who had an 11q23 chromosomal aberration as an additional change after treatment with etoposide and mitoxantrone, agents that affect topoisomerase II (Topo II). One patient with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (L2) received chemotherapy, including 1,000 mg of etoposide and 75 mg of mitoxantrone. She relapsed 10 months later. Analysis at time of relapse showed a chromosomal aberration of del(11)(q23) as an additional cytogenetic change. The other patient was diagnosed with acute monoblastic leukemia (M5a) and received two autologous peripheral blood stem-cell transplantations. Her cumulative doses of etoposide and mitoxantrone were 6,000 mg and 42 mg, respectively. She also relapsed, and analysis at that time revealed del(11)(q23) as an additional chromosomal aberration. The mixed lineage leukemia/myeloid-lymphoid leukemia (MLL) gene was not rearranged in either case, making these cases distinct from previously described therapy-related leukemias caused by Topo II inhibitors. Based on these two cases, it may be that Topo II inhibitors can cause clonal evolution affecting chromosome band 11q23.

Fusion of the MLL gene with two different genes, AF-6 and AF-5alpha, by a complex translocation involving chromosomes 5, 6, 8 and 11 in infant leukemia

We analysed a complex translocation involving chromosomes 5, 6, 8 and 11 in a case of infant leukemia. Molecular analysis of the MLL gene revealed that MLL was fused with two different genes, AF-6 on chromosome 6q27 and AF-5alpha. AF-5alpha, the 11th partner gene fused with MLL, is a novel gene mapped to chromosome 5q12, which encodes a 31 kDa protein of 269 amino acids and contains a possible nuclear targeting sequence, a potential leucine zipper dimerization motif and an alpha-helical coiled-coil domain. In situ hybridization and molecular cloning analyses demonstrated that two different types of chromosomal recombination had occurred in the cells. One was a three-way translocation among chromosomes 6, 8 and 11, and the other was an insertion of a chromosome 5-derived segment into the breakpoint of chromosomes 8 and 11. Accordingly, the karyotype was defined as del(5)(q11.2q12), der(6)t(6;8) (q27;q11.2), der(8)(8pter-->8q11.2::5q11.2-->5q12::11q23-->++ +11qter), der(11)t(6;11) (q27;q23). Thus, the MLL gene created two different fusion mRNAs, since the chromosome 11 split into two different chromosomes 5 and 6. This is the first report demonstrating fusion of the MLL gene with two different genes by a complex translocation.

Identification of MLL and chimeric MLL gene products involved in 11q23 translocation and possible mechanisms of leukemogenesis by MLL truncation

11q23 chromosome aberrations are frequently observed in infantile as well as therapy-related leukemias. The target gene at 11q23, MLL, is disrupted by the translocation and becomes fused to various translocation partner genes such as AF4/FEL, LTG9/AF9 and LTG19/ENL. The resulting chimeric mRNAs are fused in frame and have been predicted to encode leukemia-specific chimeric proteins. In the present study, we raised antibodies against MLL, LTG9 and LTG19 and demonstrated that MLL and chimeric MLL-LTG9 and MLL-LTG19 products are synthesized in vivo and are localized in the nuclei, using immunofluorescence and cell fractionation studies. The truncated N-terminal portion of the MLL product common to the various types of 11q23 translocation was also localized in the nuclei in a similar fashion. Murine 32Dc13 cells stably expressing the truncated N-terminal MLL protein exhibited an inhibition of differentiation and a growth advantage following stimulation by granulocyte-colony stimulating factor, although the IL-3 dependency was not significantly changed in comparison to the parental cells. These results suggest that the N-terminal portion common to various MLL-chimeric products plays an important role in leukemogenesis.

Introduction of the c-kit gene leads to growth suppression of a breast cancer cell line, MCF-7

Normal ductal cells of the breast are exceptional on that their epithelial cells abundantly express the c-kit receptor. Loss of c-kit expression has been reported in 80-90% of breast cancer specimens, suggesting a possible role in the development of tumors. In the present study, we introduced a c-kit expression vector into a breast cancer cell line. MCF-7, which does not express c-kit but does express its ligand, stem cell factor (SCF). Anchorage dependent and independent growth was found to be inhibited in bulk cultures of the c-kit transfectants, although this suppression appeared to be incomplete, allowing a considerable fraction to tolerate c-kit expression. Heterogeneous sensitivity to the suppressive effects mediated by the c-kit receptor was also observed among individual clones isolated from the bulk cultures. These results suggest that c-kit can mediate inhibitory signals for the growth of breast cancer cells, but that cellular heterogeneity exists regarding the response. Further studies are warranted to elucidate the molecular basis for the inhibitory effects of c-kit.

A novel human leukaemic cell line, CTS, has a t(6;11) chromosomal translocation and characteristics of pluripotent stem cells

A novel human leukaemic cell line, designated CTS, was established from the peripheral blood of a 13-year-old girl suffering from acute myeloblastic leukaemia (AML) in relapse. CTS cells expressed CD7, CD13, CD33, CD34 and HLA-DR antigens, and showed ultrastructural myeloperoxidase activity. In addition, CTS cells showed DNA rearrangements of the immunoglobulin heavy chain gene and the light kappa chain gene, and deletions of the T-cell receptor delta 1 gene. Cytogenetic analysis revealed a human female diploid karyotype with a t(6;11)(q27;q23) chromosomal translocation. Molecular studies demonstrated a DNA rearrangement of the MLL gene, the expression of a truncated 11.0 kb MLL mRNA and the detection of the MLL/AF-6 fusion transcript in CTS cells. To our knowledge, this cell line is the first report of a human leukaemic cell line with a t(6;11) chromosomal translocation. CTS cells showed no significant proliferative response to the cytokines, IL-2, IL-3, IL-6, IL-11, GM-CSF, G-CSF, EPO, SCF, but were induced to differentiate to the T-cell, B-cell, erythroid or megakaryocytic lineage in the presence of particular cytokines. This CTS cell line may provide a useful tool in the study of the oncogenesis of mixed lineage leukaemia with 11q23 abnormalities and for the analysis of growth and differentiation of pluripotent stem cells.

[Changes in erythrocyte structure and in platelets in elderly patients with disseminated intravascular coagulation]

We measured the platelet distribution width, the mean platelet volume, the volume percentage of platelets, and the platelet-to-large-cell ratio in 15 elderly patients with disseminated intravascular coagulation (DIC). Peripheral venous blood mixed with ehtylenediaminetetraacetic acid was analyzed with a Sysmex E-4000 analyzer. The underlying diseases were sepsis, pneumonia, pyelonephritis, and other inflammatory diseases. The mean duration of survival from the onset of DIC was 16.9 +/- 23.9 days. The distribution of red cell sizes before the onset of DIC did not differ significantly from that in patients without DIC, but fragmentation of erythrocytes on blood films was more common in the early stage of DIC (p < 0.01). Before the onset of DIC, the two groups did not differ significantly in the frequency of giant platelets on blood smears. At the onset of DIC, the platelet distribution width, the mean platelet volume, and the platelet-to-large-cell ratio were significantly higher than in patients without DIC. The concentration of glutamic-oxaloacetic transaminase and those of other serum enzymes did not change significantly, but the serum creatinine concentration and the blood urea nitrogen level increased as the platelet-to-large-cell ratio increased. No significant relation was evident between the levels of serum C-reactive protein and creatinine, between the platelet-to-large-cell ratio and the mean volume of red blood cells, or between the platelet-to-large-cell ratio and the distribution of red cell sizes. These data suggest that studies of platelets are more useful in the diagnosis of DIC at early stages of impaired organ function than are other indicators of inflammation such as the level of C-reactive protein.

[Anemia in elderly patients with malignant tumors]

Complications, prognosis, and efficacy of treatments were retrospectively studied in elderly patients, some of whom had lung, stomach, colon, pancreatic, and liver cancers. Hemoglobin concentration and characteristics of erythrocytes were measured for up to sixty months. Eighty-eight patients died of cancer, and malignant tumors were detected before death in 57. The average survival periods were 11 months for patients with gastric cancer. 9 months for those with colon cancer, and 7 months for those with lung cancer. Malignancies of the digestive organs and lung were often detected in elderly patients with anemia. In elderly people who were without cancer for more than 78 months the hemoglobin concentration did not change significantly, but in those with a malignancy the hemoglobin concentration continuously decreased. Patients with colon cancer who were given blood transfusions survived longer than those who were not given the transfusions, but the same was not true of patients with gastric or lung cancers. Iron therapy, however, was generally effective in patients with malignant tumors of the gastrointestinal tract. Among those who were near death, the red cell distribution widths differed significantly between patients with different types of carcinomas, but differences in mean corpuscular hemoglobin and in mean corpuscular volume were not statistically significant. In conclusion, hemoglobin concentration and characteristics of erythrocytes should not be neglected in the diagnosis and treatment of cancers in the elderly.

Evaluation of active oxygen effect on photosynthesis of Chlorella vulgaris

The relationship between O2 and an active oxygen scavenging system in Chlorella vulgaris var.vulgaris (IAM C-534) was investigated. When Chlorella vulgaris was exposed to 2% O2, only traces of active oxygen scavenging enzymes were found. When the Chlorella vulgaris was treated with 20% or 50% O2, it was shown that the level of enzyme activity increased as the O2 concentration increased. An increase in enzyme activity was not found in any specific enzyme but in all of the enzymes, but the level of glutathione and ascorbate remained the same in all the cases. In addition, the photosynthetic efficiency also decreased as the concentration of O2 was increased. These results suggest that an O2 enriched environment can lead to an increase in the production of active oxygen species such as O2.- and H2O2 and to a decrease in the photosynthetic efficiency in Chlorella vulgaris. The hydroxyl radical (.OH) was detected directly in the Chlorella vulgaris suspension with a spin trapping reagent. It was also clear that the increase in the .OH intensity as the visible light intensity increased was unrelated to the O2 concentration. It was suggested that the conditions for producting .OH and the other active oxygen species were different, and that two types of oxygen stress should exist in the Chlorella vulgaris.

Clinicopathologic study of PRAD1/cyclin D1 overexpressing lymphoma with special reference to mantle cell lymphoma. A distinct molecular pathologic entity

Mantle cell lymphomas (MCLs) are frequently associated with the overexpression of PRAD1/cyclin D1, activated by 11q13 translocation and its molecular counterpart BCL-1 gene rearrangement. We recently described the correlation of positive nuclear staining using monoclonal antibody against a PRAD1/cyclin D1 product with mRNA overexpression in MCLs. In the present study, we immunohistochemically investigated the PRAD1/cyclin D1 protein in a large series of 334 lymphoproliferative disorders, including 39 cases of MCLs on paraffin sections. Based on the cyclin D1 positivity, CD5 expression, and the morphologic features of the tumor tissue, four groups of MCL-related lesions were identified among the B-cell lymphomas examined: 36 cases with cyclin D1 overexpression, 35 (95%) of which exhibited CD5-positivity and MCL-morphology (Group 1); four cases of lymphomas with MCL morphology and CD5 expression but lacking cyclin D1 overexpression (Group II); four cases of lymphomas without cyclin D1 overexpression and surface CD5 but that fall within the morphologic boundaries of MCLs (Group III); and 11 cases of CD5-positive diffuse large cell lymphomas without cyclin D1 overexpression (Group IV). The Group I cases demonstrated quite homogeneous clinicopathologic features identical to those of MCLs. This group showed a poor prognosis (11% had 5-year survival), which is highly contrasted with that of Group II (100%). Although the four groups of MCL-related lesions sometimes overlapped in their histologic or phenotypic spectrums, each appeared to show distinct clinicopathologic and prognostic profiles. Our study provides a basis for further clarification of the nature of the neoplasms of Groups II, III, and IV. Moreover, this comprehensive study may indicate that the overexpression of PRAD1/cyclin D1 is biologically essential to defining MCLs.

Frequency and clinical significance of the MLL gene rearrangements in infant acute leukemia

We have analyzed the frequency and clinical significance of the MLL gene rearrangements in 42 cases of infant acute leukemias; including 37 cases of acute lymphoblastic leukemia (ALL) and five cases of acute myeloid leukemia (AML). MLL gene rearrangements were found in 27 of the 37 ALL cases (73 percent), and in all five AML cases. Cytogenetic studies showed 11q23 abnormalities in 24 of 27 ALL cases with MLL gene rearrangements. MLL gene rearrangements were significantly correlated with absence of CD10 expression and poor prognosis, but not with age under 6 months, hyperleukocytosis, myeloid-associated antigen expression, or CNS leukemia. The 3-year overall survival rate for ALL cases with MLL gene rearrangements was 5.3 +/- 5.2 percent, compared with 88.9 +/- 10.5 percent for cases with germline MLL (P=0.0001). Absence of CD10 expression was also associated with poor prognosis (9.9 +/- 6.6 percent vs 85.7 +/- 13.2 percent, P = 0.0003). Of the five AML cases, three have remained alive for 27 months to 67 months. These findings suggest that infant ALL with MLL gene rearrangement is strongly associated with poor prognosis. We consider that infant ALL should be treated on different chemotherapy protocols according to the presence or absence of MLL gene rearrangement.

The Drosophila tamou gene, a component of the activating pathway of extramacrochaetae expression, encodes a protein homologous to mammalian cell-cell junction-associated protein ZO-1

In Drosophila sensory organ development, the balance of activities between proneural genes and repressor genes defines a proneural cluster as a population of competent cells for neural development. In this study, we report the isolation and analysis of the tamou (tam) gene that encodes a cell-cell junction-associated protein, which is homologous to mammalian ZO-1, a member of the membrane-associated guanylate kinase homolog family. The tam mutation reduces the transcription of a repressor gene, extramacrochaetae, and causes enlargement of a proneural cluster where supernumerary precursor cells emerge, resulting in extra mechanosensory organs in the fly. These results suggest that the membrane-associated Tam protein is involved in the signaling pathway that activates emc expression.

Expression of costimulatory molecules in human leukemias

In order to determine the indication of B7 (B7-1 and B7-2) molecules-mediated immuno-gene therapy for human leukemias, we investigated 94 human leukemic samples for the expression of MHC molecules required for tumor antigen-specific signals and of B7-1, B7-2, and ICAM-1 molecules required for non-specific costimulatory signals. All samples were strongly positive for MHC class I and 84% for class II antigen. B7-1, B7-2 and ICAM-1 were expressed in 5%, 22% and 16% of the total cases, respectively. Especially in 54 AML samples, B7-1 was only expressed in one case, while B7-2 was detected in as many as 15 cases (28%). We have also examined 13 human myelo/monocytic cell lines for the expression of class II and costimulatory molecules and found that significant expression of costimulatory molecules was induced in human leukemic cells by some suitable drugs, among which interferon-gamma (IFN-gamma) was the most potent inducer. Our results indicate that when the B7-mediated immuno-gene therapy was applied to human leukemias, especially to AML, B7-1 was rather preferable to B7-2 in that the latter was more widely expressed on human leukemic cells. Furthermore, since gene-transfer systems occasionally accompany serious problems, it should be taken into account that costimulatory molecules on human myelo/monocytic leukemic cells could be induced ex vivo without the introduction of exogenous genes.

Inactivation of multiple tumor-suppressor genes involved in negative regulation of the cell cycle, MTS1/p16INK4A/CDKN2, MTS2/p15INK4B, p53, and Rb genes in primary lymphoid malignancies

It is now evident that the cell cycle machinery has a variety of elements negatively regulating cell cycle progression. However, among these negative regulators in cell cycle control, only 4 have been shown to be consistently involved in the development of human cancers as tumor suppressors: Rb (Retinoblastoma susceptibility protein), p53, and two recently identified cyclin-dependent kinase inhibitors, p16INK4A/MTS1 and p15INK4B/MTS2. Because there are functional interrelations among these negative regulators in the cell cycle machinery, it is particularly interesting to investigate the multiplicity of inactivations of these tumor suppressors in human cancers, including leukemias/lymphomas. To address this point, we examined inactivations of these four genes in primary lymphoid malignancies by Southern blot and polymerase chain reaction-single-strand conformation polymorphism analyses. We also analyzed Rb protein expression by Western blot analysis. The p16INK4A and p15INK4B genes were homozygously deleted in 45 and 42 of 230 lymphoid tumor specimens, respectively. Inactivations of the Rb and p53 genes were 27 of 91 and 9 of 173 specimens, respectively. Forty-one (45.1%) of 91 samples examined for inactivations of all four tumor suppressors had one or more abnormalities of these four tumor-suppressor genes, indicating that dysregulation of cell cycle control is important for tumor development. Statistical analysis of interrelations among impairments of these four genes indicated that inactivations of the individual tumor-suppressor genes might occur almost independently. In some patients, disruptions of multiple tumor-suppressor genes occurred; 4 cases with p16INK4A, p15INK4B, and Rb inactivations; 2 cases with p16INK4A, p15INK4B, and p53 inactivations; and 1 case with Rb and p53 inactivations. It is suggested that disruptions of multiple tumor suppressors in a tumor cell confer an additional growth advantage on the tumor.

Translocation (9;11;22)(p22;q23;q11). A new type of complex variant translocation of t(9;11)(p22;q23) with MLL rearrangement

We describe a patient with acute monocytic leukemia (M5a, FAB classification) associated with a new type of variant translocation (9;11). Southern blot analysis showed the rearrangement of the MLL (ALL-1/HRX) gene at 11q23. Fluorescence in situ hybridization (FISH) with painting probes of chromosomes 9, 11, and 22 revealed the translocation as t(9;11;22) (p22;q23;q11). This is more evidence that the production of chimeric mRNA following the translocation of the LTG9 (MLLT3/AF9) gene at 9p22 to 11q is a critical event in this leukemia subtype.

Allelic-expression imbalance of the insulin-like growth factor 2 gene in hepatocellular carcinoma and underlying disease

It has been well documented that the liver is an exceptional organ in which the monoallelic expression of insulin-like growth factor 2 (IGF2) due to genomic imprinting is relaxed during the postnatal period, resulting in biallelic expression thereafter. In the present study, changes in the status of genomic imprinting were examined in 15 hepatocellular carcinomas (HCCs) as well as in 29 liver biopsies of chronic hepatitis or liver cirrhosis without clinical evidence of HCC, following screening for heterozygotes with an ApaI polymorphism in IGF2 in 34 HCCs and 80 such non-HCC cases. Extreme allelic-expression imbalance, leading to restoration of monoallelic IGF2 expression, was observed in 15 (100%) of 15 informative HCCs for the polymorphism with this monoallelic IGF2 expression appearing to be non-random from the paternal allele. Interestingly, the same allelic-expression imbalance was also present in a significant fraction of noncancerous liver specimens of patients with underlying disease known to be associated with HCC development. In contrast, the status of genomic imprinting of H19, another gene closely mapped at 11p15 under opposite imprinting, was strictly maintained in seven (100%) of seven cases informative for an RsaI polymorphism of H19. Together with the previous reports on altered genomic imprinting of IGF2 and H19 in embryonal lesions such as Wilms tumors as well as in lung cancers, the results suggest that perturbations of imprinting status occur as locus and tumor-type specific events in the development of human cancers.