The recovery of platelet cyclooxygenase activity explains interindividual variability in responsiveness to low-dose aspirin in patients with and without diabetes

BACKGROUND

Interindividual variability in response to aspirin has been popularized as 'resistance'. We hypothesized that faster recovery of platelet cyclooxygenase-1 activity may explain incomplete thromboxane (TX) inhibition during the 24-h dosing interval.

OBJECTIVE

To characterize the kinetics and determinants of platelet cyclooxygenase-1 recovery in aspirin-treated diabetic and non-diabetic patients.

PATIENTS/METHODS

One hundred type 2 diabetic and 73 non-diabetic patients on chronic aspirin 100 mg daily were studied. Serum TXB(2) was measured every 3 h, between 12 and 24 h after a witnessed aspirin intake, to characterize the kinetics of platelet cyclooxygenase-1 recovery. Patients with the fastest TXB(2) recovery were randomized to aspirin 100 mg once daily, 200 mg once daily or 100 mg twice daily, for 28 days and TXB(2) recovery was reassessed.

RESULTS AND CONCLUSIONS

Platelet TXB(2) production was profoundly suppressed at 12 h in both groups. Serum TXB(2) recovered linearly, with a large interindividual variability in slope. Diabetic patients in the third tertile of recovery slopes (≥ 0.10 ng mL(-1) h(-1) ) showed significantly higher mean platelet volume and body mass index, and younger age. Higher body weight was the only independent predictor of a faster recovery in non-diabetics. Aspirin 100 mg twice daily completely reversed the abnormal TXB(2) recovery in both groups. Interindividual variability in the recovery of platelet cyclooxygenase activity during the dosing interval may limit the duration of the antiplatelet effect of low-dose aspirin in patients with and without diabetes. Inadequate thromboxane inhibition can be easily measured and corrected by a twice daily regimen.

Hereditary inclusion-body myopathy with sparing of the quadriceps: the many tiles of an incomplete puzzle

The hereditary inclusion-body myopathies encompass several syndromes with autosomal recessive or dominant inheritance. Despite a different clinical presentation they all have a progressive course leading to severe disability and share similar pathologic findings at the muscle biopsy. Quadriceps-sparing autosomal recessive hereditary inclusion-body myopathy (h-IBM) is the commonest form and is tied to mutations of the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) that codes for a rate-limiting enzyme in the sialic acid biosynthetic pathway. Despite the identification of the causative gene defect, it has not been clarified how mutations of the GNE gene impair muscle homeostasis. Although several lines of evidence argue in favor of an abnormal sialylation of muscle glycoproteins playing a key role in h-IBM pathogenesis, others studies have demonstrated new functions of the GNE gene, outside the sialic acid biosynthetic pathway, that may also be relevant. This review illustrates the clinical and pathologic characteristics of h-IBM and the main clues available to date concerning the possible pathogenic mechanisms of this disorder. Understanding the molecular mechanism underlying h-IBM pathology is a fundamental requisite to plan a future attempt to therapy.

Analysis of NCAM helps identify unusual phenotypes of hereditary inclusion-body myopathy

BACKGROUND

Hereditary inclusion-body myopathy or distal myopathy with rimmed vacuoles (h-IBM/DMRV) is due to mutations of the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, which codes for an enzyme of the sialic acid biosynthetic pathway. By Western blot (WB) analysis, we have previously shown that in h-IBM/DMRV muscle, the neural cell adhesion molecule (NCAM) has increased electrophoretic mobility that reflects reduced sialylation of the protein.

OBJECTIVE

To identify patients with h-IBM/DMRV with atypical clinical or pathologic phenotype using NCAM analysis and the possible cellular mechanism associated with the overall abnormal sialylation of NCAM observed in this disorder.

METHODS

WB analysis of NCAM was performed on muscle biopsies of 84 patients with an uncharacterized muscle disorder who were divided in the following 2 groups: 1) 46 patients with a proximal muscle weakness in whom the main limb-girdle muscular dystrophy syndromes had been ruled out; and 2) 38 patients with a distal distribution of weakness in whom a neurogenic affection had been excluded. Patients in whom a reduced sialylation of NCAM was suspected were studied for the presence of GNE mutations.

RESULTS

In 3 patients, we found that NCAM had increased electrophoretic mobility, thus suggesting an abnormal sialylation of the protein. The genetic study demonstrated that they all carried pathogenic GNE mutations. Further studies demonstrated that hyposialylated NCAM, showing increased electrophoretic mobility on WB, is expressed by nonregenerating fibers in h-IBM/DMRV muscle.

CONCLUSIONS

WB analysis of NCAM may be instrumental in the identification of h-IBM/DMRV with atypical clinical or pathologic features.

NCAM is hyposialylated in hereditary inclusion body myopathy due to GNE mutations

The authors found that the neural cell adhesion molecule (NCAM) is hyposialylated in hereditary inclusion body myopathy (HIBM) muscle, as suggested by its decreased molecular weight by Western blot. This abnormality represented the only pathologic feature differentiating HIBM due to GNE mutations from other myopathies with similar clinical and pathologic characteristics. If further confirmed in larger series of patients, this may be a useful diagnostic marker of GNE-related HIBM.

Cyclooxygenase-1, but not -2, is upregulated in NB4 leukemic cells and human primary promyelocytic blasts during differentiation

Cyclooxygenase (COX)-1 or -2 and specific prostaglandin (PG) synthases catalyze the formation of various PGs. We investigated the expression and activity of COX-1 and -2 during granulocyte-oriented maturation induced by all-trans-retinoic acid (ATRA) of NB4 cells, originated from a human acute promyelocytic leukemia (APL), and in blasts from APL patients. The expression of COX isoenzymes or prostaglandin synthases was also investigated in circulating granulocytes and human bone marrow. COX-1 was expressed and enzymatically active in NB4 cells and primary blasts. COX-1 mRNA and protein were induced by ATRA. COX-1 protein increased approximately 2-3.5-fold by culture day 3 in NB4 cells and primary blasts, while basal COX-2 expression was very low and unaffected by ATRA. COX-1-dependent PGE(2) biosynthesis increased during differentiation approx. 5-fold. Indomethacin and the selective COX-1 inhibitor SC-560, but not selective COX-2 inhibition, impaired NB4 differentiation, reducing NADPH-oxidase activity, CD11b and CD11c expression. The immunohistochemistry of granulocytes and myeloid precursors in the bone marrow showed a large prevalence of COX-1 as compared to COX-2. In conclusion, COX-1 is induced during ATRA-dependent maturation and appears to contribute to myeloid differentiation both in vitro and ex vivo, and COX-1 activity may potentiate the differentiation of human APL.Leukemia (2004) 18, 1373-1379. doi:10.1038/sj.leu.2403407 Published online 10 June 2004

Therapy related leukemias: susceptibility, prevention and treatment

Acute leukemia is the most frequent therapy-related malignancy. Together with the increasing use of chemo- and radiotherapy, individual predisposing factors play a key role. Most of secondary leukemias can be divided in two well-defined groups: those secondary to the use of alkylating agents and those associated to topoisomerase inhibitors. Leukemias induced by alkylating agents usually follow a long period of latency from the primary tumour and present as myelodysplasia with unbalanced chromosomal aberrations. These frequently include deletions of chromosome 13 and loss of the entire or of part of chomosomes 5 or 7. The loss of the coding regions for tumor suppressor genes from hematopoietic progenitor cells is a particularly unfavourable event, since the remaining allele becomes susceptible to inactivating mutations leading to the leukemic transformation. The tumorigenic action of topoisomerase inhibitors is on the other hand due to the formation of multiple DNA strand breaks, resolved by chromosomal translocations. Among these, chromosome 11, band q23, where the myeloid-lymphoid leukemia (MLL) gene is located, is often involved. Frequent partners are chromosomes 9, 19 and 4 in the t(9;11), t(19;11) and t(4;11) translocations. Younger age, a mean period of latency of 2 years and monocytic subtypes are characteristic features of this type of leukemia. Among patients at risk for secondary leukemia, those with Hodgkin's disease are the most extensively studied, with the major impact of alkylating agents included in the chemotherapy schedule. The same is true for non-Hodgkin's lymphoma, while in multiple myeloma and acute lymphoblastic leukemia determinants are the dose of melphalan and of epypodophyllotoxin, respectively. Patients with breast, ovarian and testicular neoplasms are also at risk, in particular if trated with the association of alkylating agents and topoisomerase II inhibitors. According to the EBMT registry, in patients with lymphoma treated with high-dose therapy and autologous stem cell transplantation the cumulative risk of inducing leukemia at 5 years is 2.6%. Among treatment options, supportive therapy is indicated in older patients, while allogeneic stem cell transplantation, related or matched-unrelated, is feasible in younger patients. These data indicate the need for the identification of predisposing factors for secondary leukemia. In particular, frequent follow-up of patients at high-risk should be performed and any peripheral blood cytopenia should be considered suspicious. Whenever possible, the exclusion of drugs known to be leukemogenic from the treatment schedules should be considered, especially in young patients.

High cyclin-dependent kinase inhibitors in Bcl-2 and Bcl-xL-expressing CD34+-proliferating haematopoietic progenitors

We have previously described the isolation of primitive, slow-proliferating progenitors from normal, circulating CD34+ cells by using the fluorescent dye 5-6-carboxyfluorescein diacetate succinimidyl ester (CFDA-SE). CFDA-SE(bright) (primitive) and CFDA-SE(dim) (differentiating) cells were isolated following cytokine stimulation on the basis of their different proliferation rates. In the present work we analysed the expression levels of a number of proteins involved with differentiation, proliferation and survival/apoptosis in CFDA-SE(bright)/CD34+/slow-proliferating cells that were previously defined as progenitors capable of differentiating into different lineages. The aim of this work was to gain a better understanding of our model system in order to define some of the important parameters that regulate differentiation in haematopoietic progenitors. GATA-1 and PU.1 RNA levels were similar in freshly isolated (d 0) CD34+ and in CFDA-SE(bright) (bright) cells, whereas they increased in CFDA-SE(dim) (dim) cells. Accordingly, Nm23 was expressed at higher levels in bright cells. Moreover, bright cells had higher p21WAF1/CIP1, p27KIP1 and p16Ink4 protein levels than dim cells. Consistently, Cdc2 and Cdk2 kinase activity was much higher in the dim than in the slower proliferating bright cells. C-myc and p53 levels were higher in bright cells than in d 0 CD34+ and dim cells, and so was Bcl-xL, which followed the trend we have previously described for Bcl-2. Thus, bright cells, despite having a higher proliferation rate than the starting d 0 CD34+ population, have strikingly elevated levels of cyclin-dependent kinase inhibitors, which are likely to also act as inhibitors of differentiation.

Allelic loss in the progression of myelodysplastic syndrome

To elucidate the genetic events that may play an important role in the progression of myelodysplastic syndrome (MDS) to acute myeloid leukemia (AML), we performed allelotype analysis of 24 individuals using matched MDS and AML samples from the same patients. Because the evolution can take years to occur, we used DNAs extracted from archival samples. These samples were analyzed with 79 microsatellite markers, which mapped to each of the autosomal arms except the short arms of the acrocentric chromosomes. Loss of heterozygosity on at least one locus was observed in 18 of the 24 cases (75%) as the disease progressed. Frequent allelic loss in >20% of the informative cases was observed on chromosome arms 6q (31%), 7p (23%), 10p (31%), 11q (27%), 14q (25%), and 20q (23%). Although cytogenetic information was available for many of our cases with allelic loss on 6q, 7p, 10p, 11q, 14q, and 20q, no deletions were observed on these arms. Fractional allelic loss, calculated for each sample as the total number of chromosomal arms lost per total number of arms with information, showed a median value of 0.06 and a mean of 0.15 (range, 0-0.59). No microsatellite instability at more than one marker was found in any of the samples. These results suggest that tumor suppressor genes exist on 6q, 7p, 10p, 11q, 14q, and 20q that have an important role in the evolution of MDS to AML when they are mutated.

Granulocyte colony-stimulating factor perturbs lymphocyte mitochondrial function and inhibits cell cycle progression

Sera from healthy subjects receiving recombinant human granulocyte colony-stimulating factor (rHuG-CSF) to mobilize CD34(+) peripheral blood progenitors (PBPC) have been recently shown to induce unresponsiveness of allogeneic lymphocytes to mitogenic challenge. In the present investigation, the effects of rHuG-CSF on the early stages of lymphocyte activation-induced apoptosis and on lymphocyte cell cycle entry were evaluated. Sera were obtained from HLA-identical donors receiving rHuG-CSF to mobilize CD34(+) PBPC for allogeneic transplantation. Normal peripheral blood mononuclear cells (PBMC) were challenged with phytohemagglutinin (PHA) in the presence of serum collected before (preG) or after rHuG-CSF administration (postG). Mitochondrial function, that is, incorporation of 3,3'-dihexyloxacarbocyanine iodide [DiOC(6)(3)] and generation of reactive oxygen species (ROS) as well as expression of c-Myc and Bcl-2 family members (Bcl-2, Bcl-X(L), Bax) were evaluated by multiparameter flow cytometry. The activation-induced fragmentation of genomic DNA was detected by highly sensitive LM-PCR assay.CD4(+)DiOC(6)(3)(low) and CD8(+)DiOC(6)(3)(low) T lymphocytes increased and reached 32% (range 27%-38%) and 20% (range 15%-23%) of circulating T cells, respectively, on day 4 of rHuG-CSF administration. Hypergeneration of ROS could be demonstrated in 65% (range 58%-82%) of CD4(+) T lymphocytes and in 0.4% (range 0.2%-0. 8%) of circulating CD8(+) T cells. rHuG-CSF determined no alteration of mitochondrial function if added to allogeneic PBMC in vitro, thus suggesting indirect effects mediated by soluble factors; on the contrary, when PBMC were challenged with PHA in the presence of postG serum, both perturbation of mitochondrial transmembrane potential (Deltapsi(m)) and hypergeneration of ROS were induced, and lymphocytes were predominantly arrested in a G(0) -like phase of the cell cycle and displayed genomic DNA fragmentation. Interestingly, the preincubation of PBMC with a blocking antibody directed against CD95 abrogated the perturbation of lymphocyte Deltapsi(m), suggesting that the CD95 signaling pathway might play a role in the induction of apoptosis after PHA stimulation in the presence of postG serum. Moreover, Bax protein was overexpressed in postG (median fluorescence intensity = 180, range 168-186) compared with preG cultures (median fluorescence intensity = 75, range 68-80; p < 0.01), while no differences in Bcl-2, Bcl-X(L), and c-Myc staining intensity were observed. Our findings demonstrate a humoral-mediated rHuG-CSF-induced dissipation of lymphocyte mitochondrial Deltapsi(m); these effects might be mediated by Bax overexpression, with imbalance between apoptosis-promoting and apoptosis-inhibiting Bcl-2 family members and with subsequent induction of mitochondrial permeability transition. Whether immune dysfunction will favorably impact on incidence and severity of acute graft vs host disease after allogeneic PBPC transplantation remains to be determined.

Modulation of bcl-2 and p27 in human primitive proliferating hematopoietic progenitors by autocrine TGF-beta1 is a cell cycle-independent effect and influences their hematopoietic potential

Primitive, proliferating hematopoietic progenitors (defined as cytokine low-responding primitive progenitors; CLRPP), isolated from human CD34+ cells, expressed endoglin (CD105) and produced transforming growth factor-beta1 (TGF-beta1). Culture of CLRPP in serum-free conditions with anti-TGF-beta1 monoclonal antibody produced a substantial decrease in bcl-2 protein/RNA levels and a significant reduction of cloning and long-term culture-initiating cell (LTC-IC) activities. GATA-1 and PU.1 RNA levels were significantly up-regulated in anti-TGF-beta1-treated CLRPP, which generated an increased number of cells expressing CD15/CD11b/glycophorin-A. The described effects of TGF-beta1 neutralization were observed in the absence of any relevant effect on cell cycle; number of cell divisions; p53, c-myc, and p21 RNA levels; bcl-xL and bax protein levels; and c-myc/p16/p21/p107/Rb cell cycle-related protein levels. A relevant increase in p27 protein levels was observed in anti-TGF-beta1-treated CLRPP, suggesting a role for p27 in the regulation of the hematopoietic potential. The present study on human progenitors and previously reported data on TGF-beta1 knockout mice suggest that, at the autocrine level, the cell cycle inhibitor TGF-beta1 plays an important role in regulating the survival and differentiation of primitive proliferating hematopoietic progenitors by cell cycle-independent mechanisms.

Expression of cyclin-dependent kinase inhibitor p15(INK4B) during normal and leukemic myeloid differentiation

OBJECTIVE

Expression of the cyclin-dependent kinase inhibitor p15(INK4B) frequently is altered in myeloid malignancies. We previously demonstrated that p15(INK4B) is expressed in normal myeloid cells. The aim of this study was to investigate whether p15(INK4B) expression is restricted to the granulomonocytic lineage and to evaluate its modulation during normal and leukemic myeloid differentiation.

MATERIALS AND METHODS

Normal CD34(+) cells were cultured in serum-free media to obtain granulomonocytic, erythroid, or megakaryocytic unilineage differentiation. NB4 promyelocytic cell line and fresh leukemic blasts from seven patients with acute promyelocytic leukemia were cultured with all-trans retinoic acid. At different times of culture, cell samples were collected to evaluate p15(INK4B) by semiquantitative reverse transcriptase polymerase chain reaction.

RESULTS

p15(INK4B) mRNA was found during granulomonocytic and megakaryocytic, but not erythroid, differentiation. In the granulomonocytic lineage, p15(INK4B) was detectable when the majority of cells were at the promyelocytic stage and increased progressively in more mature elements. In the megakaryocytic lineage, p15(INK4B) was expressed in the early phase of differentiation, before megakaryoblasts had appeared, and was mantained throughout the time of culture. NB4 cell line and five of seven leukemic samples displayed undetectable or very low level of p15(INK4B) that rapidly increased during retinoic acid-induced differentiation. Two leukemic samples (both collected from two patients developing all-trans retinoic acid syndrome) showed high basal levels of p15(INK4B), which was not modified by retinoic acid treatment.

CONCLUSIONS

p15(INK4B) upregulation occurs specifically during normal granulomonocytic and megakaryocytic commitment. In acute promyelocytic leukemic blasts, p15(INK4B), which is detectable at a very low level, is promptly increased by retinoic acid. In contrast, two acute promyelocytic leukemia samples obtained from patients who developed all-trans retinoic acid syndrome showed high basal levels of p15(INK4B) that did not increase further during all-trans retinoic acid-induced differentiation.

Chromosome band 1p36 contains a putative tumor suppressor gene important in the evolution of chronic myelocytic leukemia

Chronic myelocytic leukemia (CML) is a common neoplasm of hematopoietic pluripotent stem cells. Although the evolution from chronic phase to blast crisis (BC) in CML patients is an inevitable clinical feature, little is understood about the mechanisms responsible for the transformation. We have previously performed allelotype analysis in CML BC and have detected frequent loss of heterozygosity (LOH) on the short arm of chromosome 1. To know the common region of LOH where a putative tumor suppressor gene may reside, deletional mapping was performed using 33 microsatellite markers spanning chromosome 1 in 30 patients with CML BC (21 myeloid and 9 lymphoid). DNA was extracted from slides of bone marrow smears or from bone marrow mononuclear cells. In each patient, DNA from chronic phase was analyzed alongside DNA from either their BC or accelerated phase. Allelic loss on 1p was observed in 14 of the 30 individuals (47%): 10 of the 21 myeloid and 4 of the 9 lymphoid BC cases. Serial cytogenetic information was available in 10 cases with LOH on 1p; interestingly, deletions in this region were not detected. Two samples showed LOH at all informative loci on 1p, whereas the other 12 samples showed LOH on at least one but not all loci on 1p. The common region of LOH resided proximal to D1S508 and distal to D1S507 (1p36). Our results suggest that a tumor suppressor gene that frequently plays an important role in the evolution to BC resides on 1p36 in CML.

Binding of human alpha-thrombin to platelet GpIb: energetics and functional effects

Thrombin interaction with platelet glycocalicin (GC), the 140 kDa extracytoplasmic fragment of the membrane glycoprotein Ib, was investigated by using a solid-phase assay. Thrombin bound to GC-coated polystyrene wells was detected by measuring the hydrolysis of a chromogenic substrate. The monoclonal antibody LJ-Ib10, which specifically binds to the thrombin-binding site of GC, could displace thrombin from immobilized GC, whereas the monoclonal antibody LJ-Ib1, which interacts with the von Willebrand factor-binding domain of GC, did not affect thrombin binding to GC. Competitive inhibition of thrombin binding to immobilized GC was also observed using GC in solution or ligands that bind to the thrombin heparin-binding site, such as heparin and prothrombin fragment 2. Furthermore functional experiments demonstrated that GC binding to thrombin competes with heparin for thrombin inactivation by the antithrombin III-heparin complex as well. Thrombin-GC interaction was also studied as a function of temperature over the range 4-37 degreesC. A large negative heat capacity change (DeltaCp), of -4.14+/-0.8 kJ.mol-1.K-1, was demonstrated to dominate the thermodynamics of thrombin-GC complex-formation. Finally it was demonstrated that GC binding to thrombin can allosterically decrease the enzyme affinity for hirudin via a simultaneous decrease in association rate and increase in the dissociation velocity of the enzyme-inhibitor adduct. Together these observations indicate the GC binding to the heparin-binding domain of thrombin is largely driven by a hydrophobic effect and that such interaction can protect the enzyme from inhibition by the heparin-anti-thrombin III complex.

Analysis of p18INK4C in adult T-cell leukaemia and non-Hodgkin's lymphoma

p18INK4C, a cyclin-dependent kinase inhibitor, is a homologue of p15INK4B and p16INK4A which are frequently altered in a variety of malignancies. We searched for structural alterations of the p18INK4C gene in 44 adult T-cell leukaemias (ATLs), 101 non-Hodgkin's lymphomas (NHLs), two polyclonal B-cell proliferations, seven ATL cell lines and seven leukaemia/lymphoma cell lines, by Southern blot and polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analyses. No genomic alterations of the p18INK4C gene were found in any of the samples. By RT-PCR, p18INK4C was not expressed in three of five ATL cell lines, whereas it was expressed in all the non-ATL leukaemia/lymphoma cell lines. Tax did not inhibit the expression of p18INK4C in tax-expressing Jurkat cells.

A novel, myeloid transcription factor, C/EBP epsilon, is upregulated during granulocytic, but not monocytic, differentiation

Human C/EBP epsilon is a newly cloned CCAAT/enhancer-binding transcription factor. Initial studies indicated it may be an important regulator of human myelopoiesis. To elucidate the range of expression of C/EBP epsilon, we used reverse transcription-polymerase chain reaction (RT-PCR) analysis and examined its expression in 28 hematopoietic and 14 nonhematopoietic cell lines, 16 fresh myeloid leukemia samples, and normal human hematopoietic stem cells and their mature progeny. Prominent expression of C/EBP epsilon mRNA occurred in the late myeloblastic and promyelocytic cell lines (NB4, HL60, GFD8), the myelomonoblastic cell lines (U937 and THP-1), the early myeloblast cell lines (ML1, KCL22, MDS92), and the T-cell lymphoblastic leukemia cell lines CEM and HSB-2. For the acute promyelocytic leukemia cell line NB4, C/EBP epsilon was the only C/EBP family member that was easily detected by RT-PCR. No C/EBP epsilon mRNA was found in erythroid, megakaryocyte, basophil, B lymphoid, or nonhematopoietic cell lines. Most acute myeloid leukemia samples (11 of 12) from patients expressed C/EBP epsilon. Northern blot and RT-PCR analyses showed that C/EBP epsilon mRNA decreased when the HL60 and KG-1 myeloblast cell lines were induced to differentiate toward macrophages. Similarly, Western blot analysis showed that expression of C/EBP epsilon protein was either unchanged or decreased slightly as the promyelocytic cell line NB4 differentiated down the macrophage-like pathway after treatment with a potent vitamin D3 analog (KH1060). In contrast, C/EBP epsilon protein levels increased dramatically as NB4 cells were induced to differentiate down the granulocytic pathway after exposure to 9-cis retinoic acid. Furthermore, very early, normal hematopoietic stem cells (CD34+/CD38-), purified from humans had very weak expression of C/EBP epsilon mRNA, but levels increased as these cells differentiated towards granulocytes. Likewise, purified granulocytes appeared to express higher levels of C/EBP epsilon mRNA than purified macrophages. Addition of phosphothiolated antisense, but not sense oligonucleotides to C/EBP epsilon, decreased clonal growth of HL-60 and NB4 cells by about 50% compared with control cultures. Taken together, our results indicate that expression of C/EBP epsilon is restricted to hematopoietic tissues, especially myeloid cells as they differentiate towards granulocytes and inhibition of its expression in HL-60 and NB4 myeloblasts and promyelocytes decreased their proliferative capacity. Therefore, this transcriptional factor may play an important role in the process of normal myeloid development.

Allelotype analysis in the evolution of chronic myelocytic leukemia

To elucidate the genetic events that may play important roles in the progression of chronic myelocytic leukemia (CML), we performed allelotype analysis in 30 patients with CML as the disease transformed to accelerated phase or blast crisis (21 myeloid and 9 lymphoid cases). DNAs were extracted from slides of bone marrow smears or from freshly isolated bone marrow mononuclear cells. The DNAs from the same individuals in both chronic phase and either blast crisis or accelerated phase were analyzed at 82 microsatellite markers, which mapped to each of the autosomal arms except the short arms of the acrocentric chromosomes. Loss of heterozygosity (LOH) on at least one locus was observed in 21 of the 30 cases (70%) as the disease progressed. Frequent allelic loss of > or = 20% of the informative cases was observed on chromosome arms 1p (35%), 7p (21%), 19p (20%), and 20q (29%). Allelic losses were also analyzed according to phenotypes. LOH of > or = 20% was detected on 1p (29%), 18p (20%), and 20q (27%) in myeloid blast crisis, and on 1p (50%), 4p (25%), 7p (43%), 9p (29%), 18q (25%), 19p (43%), and 20q (33%) in lymphoid blast crisis. Serial cytogenetic information was available for most of our cases with LOH on these arms, and only one case had loss of both chromosomes 9 and 20. Fractional allelic loss, calculated for each sample as the total number of chromosomal arms lost/total number of arms with information, showed a median value of 0.06 and a mean of 0.098 (range 0 to 0.60). These results suggest that tumor suppressor genes especially on 1p, 7p, 19p, and 20q probably have an important role in the progression to blast crisis of CML.

Integrity of the 1,25-dihydroxyvitamin D3 receptor in bone, lung, and other cancers

Differentiation and proliferation can be regulated in diverse cell types by 1,25-dihydroxyvitamin D3. These effects derive from modulation of gene expression mediated by the interaction of 1,25-dihydroxyvitamin D3 with the vitamin D receptor (VDR). The VDR is one of the nuclear hormone receptors. Because these transcription factors play a key role in growth control, some nuclear hormone receptors, such as the retinoic acid receptor alpha, can be disrupted in cancer. With these alterations in mind, we looked for alterations of the VDR gene in a variety of cancers, including 68 osteosarcomas, 23 other sarcomas, 34 non-small cell lung cancers, and 44 cell lines representing many tumor types. Gross integrity of the VDR gene was examined on Southern blots probed with the coding region of the VDR cDNA. The presence of point mutations targeting VDR exons 2-7 was assessed by polymerase chain reaction-single-strand conformation polymorphism analysis and direct DNA sequencing. Two alterations were detected; direct DNA sequencing of these samples revealed one silent mutation in codon 79 and a base change in intron 3. These results suggest that mutations and rearrangement of the VDR do not play a role in the cancers studied.

Is Kaposi's sarcoma--associated herpesvirus ubiquitous in urogenital and prostate tissues?

Controversy exists as to whether Kaposi's sarcoma-associated herpesvirus (KSHV) is more widespread than originally reported. Recently, Monini et al reported that KSHV is ubiquitous in urogenital and prostate tissues and sperm of healthy Italian adults using nested polymerase chain reaction (PCR). We have examined for the presence of KSHV in 10 normal prostates from Italian men and 10 from men from the United States, as well as 32 prostatic, 30 vulvar, 24 ovarian, 20 cervical, and 30 testicular cancer specimens from patients from the United States. None of the patients had a history of human immunodeficiency virus infection. The samples were tested by nested PCR. The sensitivity of this assay was determined by a dilution study performed by diluting KSHV DNA from the KS-1 cells (a primary effusion lymphoma cell line which is estimated to have 16 copies of KSHV per cell) in DNA from a K562 myeloid cell line. The nested PCR that we used can detect 2.4 copies of KSHV sequences on a background of K562 DNA. All the samples were negative for KSHV sequences. Therefore, we cannot confirm the finding that KSHV sequences are ubiquitous in urogenital and prostate tissues. Furthermore, because our samples were from both the United States and Italy, the discrepancy between results is unlikely to be explained by either ethnic or environmental factors. False-positive results easily occur using nested primer PCR because of contamination. Our data argue that KSHV is not widely disseminated in urogenital tissues from nonimmunosuppressed individuals.

Characterization of a second human cyclin A that is highly expressed in testis and in several leukemic cell lines

In this study, we isolated and characterized a human cyclin A-like gene that we named cyclin A1. Cyclin A1 has 48% identity with human cyclin A and is more related to the recently cloned murine cyclin A1 (84% identity). The human cyclin A1 is specifically expressed in testis and brain among all of the normal tissues that we studied by Northern blot analysis; in addition, it is expressed in several myeloid leukemia cell lines, including ML-1, U937, NB4, KG-1, and THP1. A sensitive reverse transcription-PCR-Southern blot method also detected low-level expression of this gene in many other hematopoietic and nonhematopoietic cell lines. The expression of cyclin A1 mRNA is differentiation- and cell cycle-regulated in the ML-1 cells. We raised polyclonal antibodies against a glutathione S-transferase-cyclin A1 fusion protein produced in Escherichia coli. In immunoblot analyses, the antibodies recognized the Mr 65,000 cyclin A1 protein in ML-1 cells. The anti-cyclin A1 also immunoprecipitated the Mr 65,000 cyclin A1, along with the Mr 33,000 cyclin-dependent kinase (CDK) 2 and other proteins at Mr 39,000, 42,000, 45,000, 95,000, and 110,000. In an in vitro kinase assay, the CDK2-cyclin A1 complex precipitated by anti-cyclin A1 showed kinase activities against histone H1. In a yeast two-hybrid assay, cyclin A1 can bind to CDK2 but not to CDC2, CDK4, and CDK5. We mapped the human cyclin A1 gene to chromosome 13q12.3-q13, approximately 1000 kb from the sequence-tagged site marker WI-3374.

Alterations of the cyclin-dependent kinase inhibitor p19 (INK4D) is rare in hematopoietic malignancies

Cyclin-dependent kinase inhibitors (CDKIs) can be classified into two groups based on the structure of the proteins. One group includes the p21 (CIP1, WAF1, CAP20), p27 (Kip1), and p57 (Kip2) CDKIs, which contain a homologous amino-terminal cyclin-dependent kinase (cdk) inhibitory domain. The p16 (INK4A), p15 (INK4B), and p18 (INK4C) CDKIs, which have an ankyrin repeat motifs, belong to the other group. The p16 and p15 CDKI genes are very frequently altered in a variety of cancers including hematopoietic malignancies. The p19 (INK4D) gene is a newly cloned CDKI which belongs to the latter group. To determine if p19 genetic alterations play a role in hematopoietic malignancies, we examined DNA from 45 childhood newly diagnosed acute lymphocytic leukemias (ALLs), 30 acute myeloblastic leukemias (AMLs), 10 chronic myelocytic leukemias (CMLs), 45 adult T cell leukemias (ATLs), 70 non-Hodgkin's lymphomas (NHLs), and 20 multiple myelomas (MM) as well as 14 ALL, 20 AML, two ATL, and five lymphoma cell lines. Using Southern blot analysis, one homozygous deletion of the p19 gene was detected in a human immunodeficiency virus (HIV)-related Burkitt-like lymphoma sample. No point mutations in any of the samples were found by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. Our investigation suggests that alterations of p19 do not play an important role in the development of most hematopoietic malignancies.

Infrequent alterations of the RAR alpha gene in acute myelogenous leukemias, retinoic acid-resistant acute promyelocytic leukemias, myelodysplastic syndromes, and cell lines

Retinoids are important regulators of cell growth and differentiation in vitro and in vivo and they exert their biologic activities by binding to nuclear retinoic acid receptors (RARs; alpha, beta, and gamma) and retinoid X receptors (RXRs; alpha, beta, and gamma). All-trans retinoic acid (RA) induces complete remission in patients with acute promyelocytic leukemia (APL) presumably by binding directly to RAR alpha of APL cells. Leukemic blasts from APL patients initially responsive to RA can become resistant to the agent. HL-60 myeloblasts cultured with RA have developed mutations of the ligand-binding region of RAR alpha and have become resistant to RA. Furthermore, insertion of an RAR alpha with an alteration in the ligand-binding region into normal murine bone marrow cells can result in growth factor-dependent immortalization of the early hematopoietic cells. To determine if alterations of the ligand binding domain of RAR alpha might be involved in several malignant hematologic disorders, the mutational status of this region (exons 7, 8, and 9) was examined in 118 samples that included a variety of cell lines and fresh cells from patients with myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML), including 20 APL patients, 5 of whom were resistant to RA and 1 who was refractory to RA at diagnosis, using polymerase chain reaction-single-strand conformational polymorphism (PCR-SSCP) analysis and DNA sequencing. In addition, 7 of the 20 APLs were studied for alterations of the other coding exons of the gene (exons 2 through 6). No mutations of RAR alpha were detected. Although the sensitivity of PCR-SSCP analysis is less than 100%, these findings suggest that alterations of RAR alpha gene are rare and therefore other mechanisms must be involved in the onset of resistance to retinoids and in the lack of differentiation in disorders of the myeloid lineage.

Effect of sodium on the energetics of thrombin-thrombomodulin interaction and its relevance for protein C hydrolysis

Measurements of the apparent affinity constant for thrombomodulin (TM) binding to human alpha-thrombin as a function of both NA+ and temperature at constant ionic strength (0.15 M) showed that TM affinity increases in the presence of Na+ and vice versa. Moreover, this experimental strategy allowed us to accurately split the free energy of sodium binding into its entropic and enthalpic components for both the TM-free and TM-bound enzyme. Namely, at 25 degrees C, the value of delta G of sodium binding was found equal to -2.4 kcal/mol in the absence of TM and -3.6 kcal/mol for the thrombin-TM complex. The enthalpic contribution to the free energy of sodium binding is equal to -27 kcal/mol and -21 kcal/mol in the TM-free and TM-bound thrombin forms, respectively. Finally, the entropy change for sodium binding was also affected by TM, being equal to -83 cal/(mol deg) and -58 cal/(mol deg) in TM-free and TM-bound thrombin species, respectively. Moreover, the thermodynamic parameters for TM binding to Na+-free thrombin species were solved. TM binding is characterized by an enthalpy and entropy change equal to -10 kcal/mol and 2 cal/(mol deg), respectively, for Na+-free thrombin. It is well known that Na+ binding to thrombin causes conformational transitions and functional activation of the enzyme molecule. The finding that binding of thrombomodulin enhances thrombin affinity for sodium and vice versa raises the question as to whether the change of Na+ ligation induced by TM binding could contribute to the change in thrombin specificity for the hydrolysis of Protein C. Therefore, the effect of sodium binding to thrombin on the hydrolysis of human Protein C was extensively investigated. At both 25 and 37 degrees C the value of kcat/Km for Protein C hydrolysis by thrombin in the absence of TM was found to be enhanced by Na+ over a concentration ranging from 0 to 150 mM. Application of thermodynamic principles demonstrated that the Na+-thrombomodulin linkage contributes, under physiological conditions of sodium activity and temperature, to reduce significantly the transition-state stabilization free energy for Protein C hydrolysis.

Effects of novel retinoid X receptor-selective ligands on myeloid leukemia differentiation and proliferation in vitro

The biologic effects of retinoids such as all-trans-retinoic acid (ATRA) and 9-cis-retinoic acid on proliferation and differentiation of hematopoietic cells are mediated by binding and activating two distinct families of transcription factors: the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). The RARs require heterodimerization with RXRs; in addition, RXRs can form homodimers, which can bind to DNA response elements that are either distinct or the same as those bound by the RAR/RXR heterodimers. Therefore, the two retinoid pathways provide sequences that are specific for effective DNA binding and activation of target genes. We have developed several series of novel synthetic retinoids that selectively interact with RXR/RXR homodimers and RAR/RXR heterodimers. We show here that SR11236 and SR11246, which are RXR-selective analogs, had little ability to inhibit clonal growth and induce differentiation of leukemic cells (HL-60 cells and fresh acute myeloid leukemia cells). However, SR11249, SR11256, and LGD1069, which activated both RXR/RXR homodimers and RAR/RXR heterodimers, could inhibit clonal growth and induce differentiation of HL-60 cells as well as leukemic cells from patients, including those with acute promyelocytic leukemia (APL). This is similar to results observed with RAR/RXR-specific ligands. Interestingly, the combination of ATRA and either SR11249, SR11256, or LGD1069 showed synergistic effects in inducing differentiation of HL-60 cells. A retinoid (SR11238) with strong anti-AP-1 activity that did not activate the RARs and RXRs for gene transcription from the response element TREpal was inactive in our assay systems, suggesting that the antiproliferative effects of retinoids on leukemic cells is not mediated by inhibiting the AP-1 pathway. We conclude that the RAR/RXR pathway is more important than RXR/RXR pathway for differentiation and proliferation of acute myeloid leukemic cells, and certain retinoids or combination of retinoids with both RAR and RXR specificities may synergistically enhance the differentiation activity of ATRA, which may be relevant in several clinical situations.

Deletions of the cyclin-dependent kinase inhibitor genes p16INK4A and p15INK4B in non-Hodgkin's lymphomas

The tumor suppressor genes p16INK4A and p15INK4B map to the 9p21 chromosomal locus and are either homozygously deleted or mutated in a wide range of human cancer cell lines and tumors. Although chromosome 9 abnormalities have been described in non-Hodgkin's lymphomas (NHLs), to date, the mutational status of these genes has not been determined for these malignancies. A total of five cell lines and 75 NHLs were examined for homozygous deletions or point mutations in the coding regions of both the p15 and p16 genes using Southern blot and/or polymerase chain reaction-single-strand conformation polymorphism analyses. Homozygous deletions of either the p16 gene or both the p15 and p16 genes were observed in one diffuse large B-cell lymphoma cell line and two uncultured lymphomas consisting of one large B-cell and one mixed T-cell lymphoma. In contrast, point mutations were not detected in either the cell lines or lymphomas. These results indicate that the rate of alterations in the p15 and p16 genes is low for lymphomas, but loss of p16 and/or p15 may be involved in the development of some lymphomas.

Molecular analysis of the cyclin-dependent kinase inhibitor gene p27/Kip1 in human malignancies

Cyclin and cyclin-dependent kinase (CDK) complexes play important roles in controlling the cell cycle. The CDK inhibitors (CDKIs) inhibit the kinase activities of the complexes and block transitions of the cell cycle. Recently several CDKI genes have been cloned, and evidence suggests that at least a couple of these may be tumor suppressor genes. In this study, the partial structure of a CDKI gene, p27/Kip1, was determined. In addition, a large number of human cancers (432 cases) and cancer cell lines (20 lines) were analyzed for alterations of the p27/Kip1 gene by Southern blot analysis and PCR/single-strand conformation polymorphism. The coding region of the p27/Kip1 gene consists of at least two exons and an intron of about 600 bp. In 140 tumors of various tissues and 18 transformed cell lines, no deletions or rearrangements of the gene were detected by Southern blot analysis using a part of the coding sequence as a probe. One polymorphism and one silent mutation were detected by PCR/single-strand conformation polymoprhism. The polymorphism was a nucleotide substitution of guanine for thymine (GTC-->GGC) at codon 109, resulting in an amino acid substitution of glycine for valine (Val-->Gly). In summary, no abnormalities of the p27/Kip1 gene were detected in human malignancies. Now, two groups of CDKIs are classified based on the structure of the proteins. One group includes the p15, p16, and p18 CDKIs, which have ankyrin repeat motifs. The p15 and p16 CDKI genes are very frequently mutated in a variety of cancers. The p27/Kip1 and p21 CDKIs belong to the other group. We reported previously that abnormalities of the p21 gene were very rare. The latter group of the CDKIs, including p27/Kip1 and p21, are rarely mutated in human malignancies.