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The recombinant retrovirus, MoFe2-MuLV (MoFe2), was constructed by replacing the U3 region of Moloney murine leukemia virus (M-MuLV) with homologous sequences from the FeLV-945 LTR. NIH/Swiss mice neonatally inoculated with MoFe2 developed T-cell lymphomas of immature thymocyte surface phenotype. MoFe2 integrated infrequently (0 to 9%) near common insertion sites (CISs) previously identified for either parent virus. Using three different strategies, CISs in MoFe2-induced tumors were identified at six loci, none of which had been previously reported as CISs in tumors induced by either parent virus in wild-type animals. Two of the newly identified CISs had not previously been implicated in lymphoma in any retrovirus model. One of these, designated 3-19, encodes the p101 regulatory subunit of phosphoinositide-3-kinase-gamma. The other, designated Rw1, is predicted to encode a protein that functions in the immune response to virus infection. Thus, substitution of FeLV-945 U3 sequences into the M-MuLV long terminal repeat (LTR) did not alter the target tissue for M-MuLV transformation but significantly altered the pattern of CIS utilization in the induction of T-cell lymphoma. These observations support a growing body of evidence that the distinctive sequence and/or structure of the retroviral LTR determines its pattern of insertional activation. The findings also demonstrate the oligoclonal nature of retrovirus-induced lymphomas by demonstrating proviral insertions at CISs in subdominant populations in the tumor mass. Finally, the findings demonstrate the utility of novel recombinant retroviruses such as MoFe2 to contribute new genes potentially relevant to the induction of lymphoid malignancy. [ABSTRACT FROM AUTHOR]

δ-Tocopherol (δ-T), the least prevalent tocopherol in our diet, was described to have a more potent anticancer activity in solid tumors compared to the other tocopherols. δ-T induces tumor cell death through peroxisome proliferator-activated receptor γ (PPAR-γ) induction, cyclin-D1 inhibition, and modulation of redox balance. Nevertheless, the role of δ-T in preventing or treating hematologic malignancies has not been studied. In this study, we screened the efficacy of δ-T against six cell lines representing a wide spectrum of hematologic malignancies: Jurkat (acute T-cell leukemia), K-562 (chronic myeloid leukemia), KG-1 [acute myeloid leukemia (AML)], THP-1 (acute monocytic leukemia), TOM-1 (acute lymphoblastic leukemia), and UMCL01-101 (AIDS-associated diffuse large B-cell lymphoma). Interestingly, the AML cell line KG-1 was the only one to be significantly affected at concentrations of δ-T as low as 20 µM. The antileukemic activity of δ-T in AML was verified in a set of primary cells collected from patients newly diagnosed with AML. Apoptotic induction and cell cycle arrest explained the efficacy of δ-T against KG-1 cells. The mechanism of cell growth inhibition of δ-T was through downregulation of cyclin-D1 and a set of homeobox proteins (HOXA9, PBX1, and Cdx2) that have a well-documented role in the pathobiology of AML. [ABSTRACT FROM AUTHOR]

Targeting components of the B-cell receptor (BCR) pathway have dramatically improved clinical outcomes in a variety of B-cell malignancies. Despite the well-documented pathogenic role of BCR precursor (pre-BCR) pathway in B-cell acute lymphoblastic leukemia (B-ALL), there is limited available data of therapies that aim to disrupt this pathway. To investigate the role of protein kinase Cβ (PKCβ), a crucial mediator of BCR and pre-BCR signaling, in B-ALL survival, we studied the activity of the PKCβ selective inhibitor enzastaurin (ENZ) in seven B-ALL cell lines. Treatment with ENZ resulted in a dose- and time-dependent growth inhibition in all cell lines with a relatively higher efficacy in pro-B ALL with translocation t(4;11)(q21;q23). The mechanism of growth inhibition was by apoptotic induction and cell cycle arrest. A rapid reduction in phosphorylation of AKT and its downstream target glycogen synthase kinase 3β (GSK3β) were observed at 30 min after treatment and remaining for 48 h. The reduction in GSK3β phosphorylation was associated with a paradoxical accumulation of β-catenin, which was due to a transient loss of β-catenin phosphorylation at ser33-37. In addition, accumulation of β-catenin was associated with downregulation of c-Myc, upregulatiuon of c-Jun, and a subsequent protective effect on the tumor suppressor p73. Data in this paper were presented in part at 2012 American Society of Hematology Annual Meeting, abstract 1350. [ABSTRACT FROM AUTHOR]

Feline leukemia virus (FeLV) is a naturally transmitted gammaretrovirus that infects domestic cats. FeLV-945, the predominant isolate associated with non-T-cell disease in a natural cohort, is a member of FeLV subgroup A but differs in sequence from the FeLV-A prototype, FeLV-A/61E, in the surface glycoprotein (SU) and long terminal repeat (LTR). Substitution of the FeLV-945 LTR into FeLV-A/61E resulted in pathogenesis indistinguishable from that of FeLV-A/61E, namely, thymic lymphoma of T-cell origin. In contrast, substitution of both FeLV-945 LTR and SU into FeLV-A/61E resulted in multicentric lymphoma of non-Tcell origin. These results implicated the FeLV-945 SU as a determinant of pathogenic spectrum. The present study was undertaken to test the hypothesis that FeLV-945 SU can act in the absence of other unique sequence elements of FeLV-945 to determine the disease spectrum. Substitution of FeLV-A/61E SU with that of FeLV-945 altered the clinical presentation and resulted in tumors that demonstrated expression of CD45R in the presence or absence of CD3. Despite the evident expression of CD45R, a typical B-cell marker, T-cell receptor beta (TCR) gene rearrangement indicated a T-cell origin. Tumor cells were detectable in bone marrow and blood at earlier times during the disease process, and the predominant SU genes from proviruses integrated in tumor DNA carried markers of genetic recombination. The findings demonstrate that FeLV-945 SU alters pathogenesis, although incompletely, in the absence of FeLV-945 LTR. Evidence demonstrates that FeLV-945 SU and LTR are required together to fully recapitulate the distinctive non-T-cell disease outcome seen in the natural cohort. [ABSTRACT FROM AUTHOR]

Background: Feline leukemia virus (FeLV)-945, a member of the FeLV-A subgroup, was previously isolated from a cohort of naturally infected cats. An unusual multicentric lymphoma of non-T-cell origin was observed in natural and experimental infection with FeLV-945. Previous studies implicated the FeLV-945 surface glycoprotein (SU) as a determinant of disease outcome by an as yet unknown mechanism. The present studies demonstrate that FeLV-945 SU confers distinctive properties of binding to the cell surface receptor. Results: Virions bearing the FeLV-945 Env protein were observed to bind the cell surface receptor with significantly increased efficiency, as was soluble FeLV-945 SU protein, as compared to the corresponding virions or soluble protein from a prototype FeLV-A isolate. SU proteins cloned from other cohort isolates exhibited increased binding efficiency comparable to or greater than FeLV-945 SU. Mutational analysis implicated a domain containing variable region B (VRB) to be the major determinant of increased receptor binding, and identified a single residue, valine 186, to be responsible for the effect. Conclusions: The FeLV-945 SU protein binds its cell surface receptor, feTHTR1, with significantly greater efficiency than does that of prototype FeLV-A (FeLV-A/61E) when present on the surface of virus particles or in soluble form, demonstrating a 2-fold difference in the relative dissociation constant. The results implicate a single residue, valine 186, as the major determinant of increased binding affinity. Computational modeling suggests a molecular mechanism by which residue 186 interacts with the receptor-binding domain through residue glutamine 110 to effect increased binding affinity. Through its increased receptor binding affinity, FeLV-945 SU might function in pathogenesis by increasing the rate of virus entry and spread in vivo, or by facilitating entry into a novel target cell with a low receptor density. [ABSTRACT FROM AUTHOR]

Background: We have previously shown that systemic infusion of insulin-like growth factor-1 (IGF-1) exerts anti-inflammatory and antioxidant effects and reduces atherosclerotic burden in apolipoprotein E (Apoe)-deficient mice. Monocytes/macrophages express high levels of IGF-1 receptor (IGF1R) and play a pivotal role in atherogenesis, but the potential effects of IGF-1 on their function are unknown.Methods and Results: To determine mechanisms whereby IGF-1 reduces atherosclerosis and to explore the potential involvement of monocytes/macrophages, we created monocyte/macrophage-specific IGF1R knockout (MΦ-IGF1R-KO) mice on an Apoe(-/-) background. We assessed atherosclerotic burden, plaque features of stability, and monocyte recruitment to atherosclerotic lesions. Phenotypic changes of IGF1R-deficient macrophages were investigated in culture. MΦ-IGF1R-KO significantly increased atherosclerotic lesion formation, as assessed by Oil Red O staining of en face aortas and aortic root cross-sections, and changed plaque composition to a less stable phenotype, characterized by increased macrophage and decreased α-smooth muscle actin-positive cell population, fibrous cap thinning, and decreased collagen content. Brachiocephalic artery lesions of MΦ-IGF1R-KO mice had histological features implying plaque vulnerability. Macrophages isolated from MΦ-IGF1R-KO mice showed enhanced proinflammatory responses on stimulation by interferon-γ and oxidized low-density lipoprotein and elevated antioxidant gene expression levels. Moreover, IGF1R-deficient macrophages had decreased expression of ABCA1 and ABCG1 and reduced lipid efflux.Conclusions: Our data indicate that macrophage IGF1R signaling suppresses macrophage and foam cell accumulation in lesions and reduces plaque vulnerability, providing a novel mechanism whereby IGF-1 exerts antiatherogenic effects. [ABSTRACT FROM AUTHOR]

The outcome of feline leukemia virus (FeLV) infection in nature is variable, including malignant, proliferative, and degenerative disorders. The determinants of disease outcome are not well understood but are thought to include viral, host, and environmental factors. In particular, genetic variations in the FeLV long terminal repeat (LTR) and SU gene have been linked to disease outcome. FeLV-945 was previously identified as a natural isolate predominant in non-T-cell neoplastic and nonneoplastic diseases in a geographic cohort. The FeLV-945 LTR was shown to contain unique repeat elements, including a 21-bp triplication downstream of the enhancer. The FeLV-945 SU gene was shown to encode mutational changes in functional domains of the protein. The present study details the outcomes of infection with recombinant FeLVs in which the LTR and envelope (env) gene of FeLV-945, or the LTR only, was substituted for homologous sequences in a horizontally transmissible prototype isolate, FeLV-A/61E. The results showed that the FeLV-945 LTR determined the kinetics of disease. Substitution of the FeLV-945 LTR into FeLV-A/61E resulted in a significantly more rapid disease onset but did not alter the tumorigenic spectrum. In contrast, substitution of both the FeLV-945 LTR and env gene changed the disease outcome entirely. Further, the impact of FeLV-945 env on the disease outcome was dependent on the route of inoculation. Since the TM genes of FeLV-945 and FeLV-A/61E are nearly identical but the SU genes differ significantly, FeLV-945 SU is implicated in the outcome. These findings identify the FeLV-945 LTR and SU gene as determinants of disease. [ABSTRACT FROM AUTHOR]

Feline leukemia virus (FeLV)-mediated lymphomagenesis in the domestic cat has been examined as a model of lymphoid malignancy in a naturally outbreeding population. The pathogenesis of two distinct, naturally occurring types of FeLV-induced tumors has been investigated: (1) a thymic lymphoma of T-cell origin, typical of FeLV-induced lymphoma, and (2) an extrathymic, extranodal lymphoma of non-B non-T-cell origin. The genetic features of these tumors are clearly distinguishable, and include determinants encoded both by the virus and the host. Virally encoded determinants of pathogenesis include the long terminal repeat (LTR) and the envelope SU protein. Cellular determinants include the involvement of a set of proto-oncogenes, and other factors characteristic of the specific cell type of origin of the tumor. Functional studies are aimed at evaluating the action and interaction of these genetic determinants in the pathogenesis of lymphoma in an animal model system. [ABSTRACT FROM AUTHOR]