[en] Classically, the 5' and 3' long terminal repeats (LTRs) are considered necessary but not sufficient for retroviral integration. Recently, we reported that inclusion of these and additional elements from Moloney murine leukemia virus (MoMLV) facilitated transgene integration, without retroviral integrase, when placed in an adenoviral context (AdLTR-luc vector) (Nat. Biotech. 18 (2000), 176; Biochem. Biophys. Res. Commun. 300 (2003), 115). To help understand this nonhomologous DNA recombination event, we constructed another vector, AdELP-luc, with 2.7 kb of MoMLV elements identically placed into an E1-deleted adenovirus type 5 backbone upstream of a luciferase cDNA reporter gene. Unlike AdLTR-luc, no MoMLV elements were placed downstream of the expression cassette. AdELP-luc readily infected epithelial cells in vitro. Southern hybridizations with DNA from cloned cells showed that disruption of the MoMLV sequences occurred. One cell clone, grown in vitro without any special selection medium for 9 months, exhibited stable vector integration and luciferase activity. Importantly, both Southern hybridization and FISH analyses showed that in addition to the MoMLV elements and expression cassette, substantial adenoviral sequence downstream of the luciferase cDNA was genomically integrated. These results suggest that the 2.7 kb of MoMLV sequence included in AdELP-luc have cis-acting functions and mediates an unusual integration event

[en] Human T-cell leukemia virus type 1 (HTLV-1) Tax-induced activation of nuclear factor-κB (NFκB) is thought to play a critical role in T-cell transformation and onset of adult T-cell leukemia. However, the molecular mechanism of the Tax-induced NFκB activation remains unknown. One of the mitogen-activated protein kinase kinase kinses (MAP3Ks) members, TAK1, plays a critical role in cytokine-induced activation of NFκB, which involves lysine 63-linked (K63) polyubiquitination of NEMO, a noncatalytic subunit of the IκB kinase complex. Here we show that Tax induces K63 polyubiquitination of NEMO. However, TAK1 is dispensable for Tax-induced NFκB activation, and deubiquitination of the K63 polyubiquitin chain failed to block Tax-induced NFκB activation. In addition, silencing of other MAP3Ks, including MEKK1, MEKK3, NIK, and TPL-2, did not affect Tax-induced NFκB activation. These results strongly suggest that unlike cytokine signaling, Tax-induced NFκB activation does not involve K63 polyubiquitination-mediated MAP3K activation

[en] In children, leukemia is the most common malignancy, and approximately 75% of leukemias are acute lymphoblastic leukemia (ALL). Central nervous system leukemia is found at diagnosis in fewer than 5% of children with ALL. Leukemic intracranial masses have been described with acute myeloid leukemia, but ALL presenting as a mass lesion is rare. We describe a unique case of an intracranial confirmed precursor B cell (pre-B) ALL mass in a 13-year-old girl that was diagnosed by brain CT, MRI and cerebral angiography, and confirmed by biopsy. This report details pertinent history and distinguishing imaging features of an intracranial ALL tumefaction. (orig.)

[en] The human T-cell leukemia virus type I (HTLV-I) Tax protein trans-activates viral transcription through three imperfect tandem repeats of a 21-bp sequence called Tax-responsive element (TxRE). Tax regulates transcription via direct interaction with some members of the activating transcription factor/CRE-binding protein (ATF/CREB) family including CREM, CREB, and CREB-2. By interacting with their ZIP domain, Tax stimulates the binding of these cellular factors to the CRE-like sequence present in the TxREs. Recent observations have shown that CCAAT/enhancer binding protein β (C/EBPβ) forms stable complexes on the CRE site in the presence of CREB-2. Given that C/EBPβ has also been found to interact with Tax, we analyzed the effects of C/EBPβ on viral Tax-dependent transcription. We show here that C/EBPβ represses viral transcription and that Tax is no more able to form a stable complex with CREB-2 on the TxRE site in the presence of C/EBPβ. We also analyzed the physical interactions between Tax and C/EBPβ and found that the central region of C/EBPβ, excluding its ZIP domain, is required for direct interaction with Tax. It is the first time that Tax is described to interact with a basic leucine-zipper (bZIP) factor without recognizing its ZIP domain. Although unexpected, this result explains why C/EBPβ would be unable to form a stable complex with Tax on the TxRE site and could then down-regulate viral transcription. Lastly, we found that C/EBPβ was able to inhibit Tax expression in vivo from an infectious HTLV-I molecular clone. In conclusion, we propose that during cell activation events, which stimulate the Tax synthesis, C/EBPβ may down-regulate the level of HTLV-I expression to escape the cytotoxic-T-lymphocyte response

[en] Leukemia is the most common malignancy in childhood. The prognosis for children with leukemia in recent decades has improved dramatically and is the result of systematic and well organized international research efforts and clinical trials. The success of treatment is now primarily dependent on the precise diagnosis of a advanced stratification of patients into risk groups. Article summarizes recent findings and current trends in diagnosis and treatment of childhood acute lymphoblastic leukemia. (author)

[en] Chronic myeloid leukemia (CML) was the first cancer associated with the specific chromosomal aberration. Philadelphia chromosome due to translocation (9, 22) is present in 95% cases, fusion gene BCR/ABL is present in 100% cases at the time of diagnosis. Disease has its own characteristics detectable by physical examination, by the examination of blood count and differential and by cytomorhologic examination of bone marrow, however the diagnosis of CML is determined by cytogenetics and molecular genetics. If the diagnosis of Ph+ BCR/ABL positive CML is confirmed, the disease is treated by tyrosine kinase inhibitors (TKI). TKI don´t affect formation of leukemic gene BCR/ABL, but they can stop the action of this gene. The target therapy of tyrosine kinase inhibitors markedly improved the survival of patients with CML by inhibition the proliferation of leukemic clone on the clinically safety level of minimal disease, although probably this treatment cannot cure the CML. Cytogenetics and molecular genetics are very important at the monitoring of residual disease with sensitivity 10"-"6. (author)

[en] Adult or newborn C57BL/6J mice were immunized with isogenic Moloney strain MuLV-induced leukemia cells irradiated with 10,000 rads or treated with low concentrations of formalin. Groups of immunized and control mice were challenged with a range of doses of viable leukemia cells, and tumor deaths were recorded for 90 days after challenge. Then, the doses of challenge cells which produced 50% tumor deaths were calculated for immunized and control mice. The logarithm of their ratio quantified the degree of protection provided by immunization. For adult C57BL/6J mice, a single immunization with MuLV-induced leukemia cells was not effective; either cells plus Bacillus Calmette-Guerin or Corynebacterium parvum, or else two immunizations with irradiated leukemia cells were needed to produce statistically significant increases in the values of the doses of challenge cells which produced 50% tumor deaths. Cross-protection was obtained by immunization with other isogenic MuLV-induced leukemias, but not by immunization with isogenic carcinogen-induced tumors or with an isogenic spontaneous leukemia. For newborn mice, a single injection of irradiated leukemia cells provided 1.3 to 1.5 logs of protection, and admixture of B. Calmette-Guerin or C. parvum increased this protection to 2.4 to 2.7 logs. Since irradiated and frozen-thawed MuLV-induced leukemia cells contained viable MuLV, leukemia cells treated with 0.5 or 1.0% formalin were tested as an alternative. A single injection of formalin-treated isogenic leukemia cells admixed with C. parvum provided between 1.7 and 2.8 logs of protection. These results demonstrate that a single vaccination of newborn animals against a highly antigenic virally induced leukemia produces strong protection against a subsequent challenge with viable leukemia cells

[en] It was described a case of chronic lymphocytic leukemia in a 75 year old man, with pseudomyelomatosis osteolytic lesions in the skull, excluding other potential causes of osteolytic lesions in the clinical context of malignant lymphoproliferative neoplasm. The real frequency of osseous compromise in chronic lymphocytic leukemia is 10%. Lesions are defined as generalized osteoporosis and osteolysis with lacunar aspect, similar to myeloma lesions. Because histopathology in lymphoproliferative neoplasms may be similar, it might be difficult to diagnose chronic lymphocytic leukemia certainly, if the clinical manifestations are not considered. Differential diagnosis with other lymphoproliferative neoplasm is based basically in absolute lymphocytosis greater than 10 X 109/L, with lymphocytes with mature appearance

[en] While human T-cell leukemia virus type 1 (HTLV-1) is associated with the development of adult T-cell leukemia (ATL), HTLV-2 has not been reported to be associated with such malignant leukemias. HTLV-1 Tax1 oncoprotein transforms a rat fibroblast cell line (Rat-1) to form multiple large colonies in soft agar, and this activity is much greater than that of HTLV-2 Tax2. We have demonstrated here that the increased number of transformed colonies induced by Tax1 relative to Tax2 was mediated by a PDZ domain-binding motif (PBM) in Tax1, which is absent in Tax2. Tax1 PBM mediated the interaction of Tax1 with the discs large (Dlg) tumor suppressor containing PDZ domains, and the interaction correlated well with the transforming activities of Tax1 and the mutants. Through this interaction, Tax1 altered the subcellular localization of Dlg from the detergent-soluble to the detergent-insoluble fraction in a fibroblast cell line as well as in HTLV-1-infected T-cell lines. These results suggest that the interaction of Tax1 with PDZ domain protein(s) is critically involved in the transforming activity of Tax1, the activity of which may be a crucial factor in malignant transformation of HTLV-1-infected cells in vivo

[en] Retroviral integrases (IN) catalyze the integration of the reverse-transcribed viral DNA into the host genome, an essential process leading to virus replication. For Moloney murine leukemia virus (M-MuLV) IN, the limited solubility of the recombinant protein has restricted the development of biophysical and structural analyses. Herein, recombinant M-MuLV IN proteins, either full length or two nonoverlapping domain constructs, were purified under non-denaturing conditions from solubilized bacterial extracts by Ni²⁺-NTA resins. Additionally, WT IN was further purified by heparin chromatography. All of the purified proteins were shown to be active and stable. WT M-MuLV IN chromatographed with a peak corresponding with a dimer by gel filtration chromatography. In contrast, the single point mutant C209A IN migrated predominantly as a tetramer. For both proteins, fractions in equilibrium between dimers and tetramers were competent to assemble concerted two-end integrations and yielded a unique strand-transfer profile in the presence of a 28-mer U5 oligonucleotide substrate, indicative of a distinct conformation within the synaptic complex. This specific target-site selection was not observed with a shorter 20-mer U5 substrate. These studies provide the foundation for biophysical and structural analysis on M-MuLV IN and the mechanism of retroviral integration