Physical interaction of the bHLH LYL1 protein and NF-kappaB1 p105.
(1/921)
The LYL1 gene was first identified upon the molecular characterization of the t(7;9)(q35;p13) translocation associated with some human T-cell acute leukemias (T-ALLs). In adult tissues, LYL1 expression is restricted to hematopoietic cells with the notable exclusion of the T cell lineage. LYL1 encodes a basic helix-loop-helix (bHLH) protein highly related to TAL-1, whose activation is also associated with a high proportion of human T-ALLs. A yeast two-hybrid system was used to identify proteins that specifically interact with LYL1 and might mediate its activities. We found that p105, the precursor of NF-kappaB1 p50, was the major LYL1-interacting protein in this system. The association between LYL1 and p105 was confirmed both in vitro and in vivo in mammalian cells. Biochemical studies indicated that the interaction was mediated by the bHLH motif of LYL1 and the ankyrin-like motifs of p105. Ectopic expression of LYL1 in a human T cell line caused a significant decrease in NF-kappaB-dependent transcription, associated with a reduced level of NF-kappaB1 proteins. (+info)
Similarities and differences in 111In- and 90Y-labeled 1B4M-DTPA antiTac monoclonal antibody distribution.
(2/921)
Monoclonal antibodies (MoAb) labeled with 90Y are being used for radioimmunotherapy. Because 90Y is a beta emitter, quantitative information from imaging is suboptimal. With the concept of a "matched pair" of isotopes, 111In is used as a surrogate markerfor90Y. We evaluated the differences in biodistribution between 111In- and 90Y-labeled murine antiTac MoAb directed against the IL-2Ralpha receptor. METHODS: The antiTac was conjugated to the 2-(4-isothiocyanatobenzyl)-6-methyl-diethylenetriamine pentaacetic acid (1B4M-DTPA, also known as MX-DTPA). Nine patients with adult T-cell leukemia were treated. Patients received approximately 185 MBq (5 mCi) 111In-labeled antiTac for imaging and 185-555 MBq (5-15 mCi) 90Y-labeled antiTac for therapy. The immunoreactivity of 111In-labeled antiTac was 90%+/-6%, whereas for 90Y-labeled antiTac, it was 74%+/-12%. RESULTS: The differences in blood and plasma kinetics of the two isotopes were small. The area undemeath the blood radioactivity curve was 1.91 percentage+/-0.58 percentage injected dose (%ID) x h/mL for 111In and 1.86%+/-0.64 %ID x h/mL for 90Y. Urinary excretion of 90Y was significantly greater than that of 111In in the first 24 h (P = 0.001), but later, the excretion of 111In was significantly greater (P = 0.001 to P = 0.04). Core biopsies of bone marrow showed a mean of 0.0029+/-0.0012 %ID/g for 111In, whereas the 90Y concentration was 0.0049+/-0.0021 %ID/g. Analyses of activity bound to circulating cells showed concentrations of 500-30,000 molecules of antiTac per cell. When cell-bound activity was corrected for immunoreactive fraction, the ratio of 111In to 90Y in circulating cells was 1.11+/-0.17. Three biopsies of tumor-involved skin showed ratios of 111In to 90Y of 0.7, 0.9 and 1.1. CONCLUSION: This study shows that differences typically ranging from 10% to 15% exist in the biodistribution between 111In- and 90Y-labeled antiTac. Thus, it appears that 111In can be used as a surrogate marker for 90Y when labeling antiTac with the 1 B4M chelate, although underestimates of the bone marrow radiation dose should be anticipated. (+info)
Spectral karyotype analysis of T-cell acute leukemia.
(3/921)
Analysis of 15 cases of T-cell acute lymphoblastic leukemia with spectral karyotyping (SKY), which can identify all chromosomes simultaneously, clarified the chromosome rearrangements in 3 cases and confirmed them in 11 others; no abnormal cells were identified in 1 case, which had only 10% abnormal cells. Five of the latter cases had a normal karyotype. Thus, the use of SKY substantially improves the precision of karyotype analysis of malignant cells, which in turn leads to a more accurate assessment of the genotypic abnormalities in those cells. (+info)
Fatal disseminated Trichoderma longibrachiatum infection in an adult bone marrow transplant patient: species identification and review of the literature.
(4/921)
Trichoderma longibrachiatum was recovered from stool surveillance cultures and a perirectal ulcer biopsy specimen from a 29-year-old male who had received an allogeneic bone marrow transplant for acute lymphoblastic leukemia. The amphotericin B (2.0 microgram/ml) and itraconazole (1.0 microgram/ml) MICs for the organism were elevated. Therapy with these agents was unsuccessful, and the patient died on day 58 posttransplantation. At autopsy, histologic sections from the lungs, liver, brain, and intestinal wall showed infiltration by branching septate hyphae. Cultures were positive for Trichoderma longibrachiatum. While Trichoderma species have been recognized to be pathogenic in profoundly immunosuppressed hosts with increasing frequency, this is the first report of probable acquisition through the gastrointestinal tract. Salient features regarding the identification of molds in the Trichoderma longibrachiatum species aggregate are presented. (+info)
Subcellular distribution and redistribution of Bcl-2 family proteins in human leukemia cells undergoing apoptosis.
(5/921)
It has been suggested that the ratio of Bcl-2 family proapoptotic proteins to antiapoptotic proteins determines the sensitivity of leukemic cells to apoptosis. However, it is believed that Bcl-2 family proteins exert their function on apoptosis only when they target to the mitochondrial outer membrane. The vinblastine-resistant T-lymphoblastic leukemic cell line CEM/VLB100 has increased sensitivity to tumor necrosis factor-alpha (TNF-alpha)-induced cytochrome c release, mitochondrial respiratory inhibition, and consequently apoptosis, compared with parental CEM cells. However, there was no difference between the two cell lines in the expression of Bcl-2 family proteins Bcl-2, Bcl-XL, Bcl-XS, Bad, and Bax at the whole cell level, as analyzed by Western blotting. Bcl-2 mainly located to mitochondria and light membrane as a membrane-bound protein, whereas Bcl-XL was located in both mitochondria and cytosol. Similar levels of both Bcl-2 and Bcl-XL were present in the resting mitochondria of the two cell lines. Although the proapoptotic proteins Bcl-XS, Bad, and Bax were mainly located in the cytosol, CEM/VLB100 mitochondria expressed higher levels of these proapoptotic proteins. Subcellular redistribution of the Bcl-2 family proteins was detected in a cell-free system by both Western blotting and flow cytometry after exposure to TNF-alpha. The levels of Bcl-2 family proteins were not altered at the whole cell level by TNF-alpha. However, after exposure to TNF-alpha, Bax, Bad, and Bcl-XS translocated from the cytosol to the mitochondria of both cell lines. An increase in Bcl-2 levels was observed in CEM mitochondria, which showed resistance to TNF-alpha-induced cytochrome c release. By contrast, decreased mitochondrial Bcl-2 was observed in CEM/VLB100 cells, which released cytochrome c from the mitochondria and underwent apoptosis as detected by fluorescence microscopy. We conclude that mitochondrial levels of Bcl-2 family proteins may determine the sensitivity of leukemic cells to apoptosis and that, furthermore, these levels may change rapidly after exposure of cells to toxic stimuli. (+info)
Constitutive activation of NF-kappaB in primary adult T-cell leukemia cells.
(6/921)
Human T-cell leukemia virus type I (HTLV-I) is an etiologic agent of adult T-cell leukemia (ATL). The viral protein Tax induces the activation and nuclear translocalization of transcription factor NF-kappaB, which is proposed to play a crucial role in the transformation of T cells by HTLV-I. However, the HTLV-I genes including Tax are not expressed significantly in primary leukemic cells from ATL patients. In this study, we examined the basis for NF-kappaB activation in freshly isolated leukemic cells from ATL patients. We found that leukemic cells from ATL patients, like HTLV-I-infected T-cell lines, display constitutive NF-kappaB DNA binding activity and increased degradation of IkappaBalpha (an inhibitor of NF-kappaB). Whereas the NF-kappaB binding activity in Tax-expressing T-cell lines consisted mostly of p50/c-Rel, fresh ATL samples contained p50/p50 and p50/p65 heterodimers. One T-cell line derived from ATL leukemic cells, TL-Om1, displayed constitutive NF-kappaB activity, as well as enhanced degradation of IkappaBalpha, despite the lack of detectable Tax expression. Interestingly, the NF-kappaB in TL-Om1 consists of p50/p50 and p50/p65 like that in fresh primary leukemic cells. Our results suggest that activation of NF-kappaB occurs through a Tax-independent mechanism in leukemic cells of ATL patients, possibly due to differential NF-kappaB subunit activation. (+info)
Fas gene mutation in the progression of adult T cell leukemia.
(7/921)
Fas antigen (Apo-1/CD95) is an apoptosis-signaling cell surface receptor belonging to the tumor necrosis factor receptor superfamily. Adult T cell leukemia (ATL) cells express Fas antigen and show apoptosis after treatment with an anti-Fas monoclonal antibody. We established the ATL cell line KOB, which showed resistance to Fas-mediated apoptosis, and found that KOB expressed two forms of Fas mRNA, the normal form and a truncated form. The truncated transcript lacked 20 base pairs at exon 9, resulting in a frame shift and the generation of a premature stop codon at amino acid 239. The same mutation was detected in primary ascitic cells and peripheral blood cells. The mutation was not detected in lymph node cells, however, although all of the primary ATL cells were of the same clonal origin. A retroviral-mediated gene transfer of the truncated Fas to Jurkat cells rendered the cells resistant to Fas-mediated apoptosis, suggesting a dominant negative interference mechanism. These results indicate that an ATL subclone acquires a Fas mutation in the lymph nodes, enabling the subclone to escape from apoptosis mediated by the Fas/Fas ligand system and proliferate in the body. Mutation of the Fas gene may be one of the mechanisms underlying the progression of ATL. (+info)
Use of alanosine as a methylthioadenosine phosphorylase-selective therapy for T-cell acute lymphoblastic leukemia in vitro.
(8/921)
Methylthioadenosine phosphorylase (MTAP) is an important enzyme for the salvage of adenine and methionine and is deficient in a variety of cancers including T-cell acute lymphocytic leukemia (T-ALL). Previously, we reported that the MTAP gene was deleted in over 30% of T-ALL patients at both diagnosis and relapse. We now report that MTAP-primary T-ALL cells are more sensitive to the toxicity of L-alanosine, an inhibitor of de novo AMP synthesis, than are MTAP+ primary T-ALL cells. As measured by [3H]thymidine incorporation, DNA synthesis in all seven MTAP-primary T-ALL cells was inhibited by L-alanosine with a mean IC50 of 4.8+/-5.3 ILM (range, 0.3-11.3 microM). On the other hand, the IC50 for 60% (12 of 20) of MTAP+ primary T-ALL was 19+/-18 microM (range, 1.7-67 microM; P = 0.02), whereas the remaining 40% (8 of 20) had an IC50 of >80 microM4. Furthermore, normal lymphocytes and MTAP+ primary T-ALL cells were rescued from L-alanosine toxicity by the MTAP substrate 5'-deoxyadenosine, but MTAP-T-ALL cells were not. These results indicate that normal cells, which are intrinsically MTAP+, would be protected from L.-alanosine toxicity, whereas MTAP-tumor cells would be killed. Thus, our results support the use of L-alanosine alone or in combination with a salvage agent as a MTAP-selective therapy and therefore lay the foundation for the initiation of clinical trials for the treatment of T-ALL and other MTAP-deficient malignancies with L-alanosine. (+info)