APOBEC3G rescues cells from the deleterious effects of DNA damage.

Human apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3G (hA3G), a member of the APOBEC family, was described as an anti-HIV-1 restriction factor, deaminating reverse transcripts of the HIV-1 genome. Several types of cancer cells that express high levels of A3G, such as diffuse large B-cell lymphoma cells and glioblastomas, show enhanced cell survival after ionizing radiation and chemotherapy treatments. Previously, we showed that hA3G promotes (DNA) double-strand breaks repair in cultured cells and rescues transgenic mice from a lethal dose of ionizing radiation. Here, we show that A3G rescues cells from the detrimental effects of DNA damage induced by ultraviolet irradiation and by combined bromodeoxyuridine and ultraviolet treatments. The combined treatments stimulate the synthesis of cellular proteins, which are exclusively associated with A3G expression. These proteins participate mainly in nucleotide excision repair and homologous recombination DNA repair pathways. Our results implicate A3G inhibition as a potential strategy for increasing tumor cell sensitivity to genotoxic treatments.

NK cells prevent T cell lymphoma development in T cell receptor-transgenic mice.

Mice that express a single transgenic T cell receptor have a low incidence of T cell lymphoma development. We investigated whether this tumor development is restricted by surveillance mechanisms that are exerted by IL-15-dependent cells. Lymphoma incidence was increased to between 30 and 60% when TCR transgenes were expressed in IL-15-deficient mice. Mice in which NK cells had been depleted genetically or with neutralizing antibodies allowed lymphoma growth while the absence of CD8 T cells was without consequence. Half of the emerged T cell lymphomas carried Notch1 mutations. The distinct phenotype of the lymphomas involved expression of PD1, CD30, CD24, the stress receptor ligand Mult1 and MHC class I down-regulation. NK cells were able to directly lyse lymphoma cells, and neutralizations of Mult1 and class I expression prevented NK cell degranulation. Together these data support an involvement of NK cells in tumor surveillance of nascent T cell lymphomas.

Vírus Linfotrópico Humano (HTLV)

O vírus linfotrópico de células T humanas tipo 1 (HTLV-1- “Human T lymphotropic vírus type 1”) foi o primeiro retrovírus humano descrito. O vírus foi inicialmente associado com a leucemia de células T do adulto (ATL) no Japão em 1977, sendo depois encontrado em diversas partes do mundo. Posteriormente, foi associado às doenças neurológicas Paraparesia Espástica Tropical (TSP) e Mielopatia Associada ao HTLV (HAM), que hoje é conhecida como HAM/TSP.

Spirulina lipopolysaccharides inhibit tumor growth in a Toll-like receptor 4-dependent manner by altering the cytokine milieu from interleukin-17/interleukin-23 to interferon-γ.

Th17 cells and the cytokine they produce, interleukin (IL)-17, play an important role in tumor progression in humans and in mice. IL-6 and IL-23 are critical cytokines for the differentiation and propagation of Th17 cells, respectively. Bacterial lipopolysaccharides (LPS) are known to stimulate immune cells to produce such inflammatory cytokines. Contrary to Escherichia coli (E. coli) LPS, LPS from Spirulina has low toxicity and barely induces in vivo production of IL-6 and IL-23 in mice. We examined the antitumor effects of Spirulina LPS compared to E. coli LPS in an MH134 hepatoma model. Administration of Spirulina LPS suppressed tumor growth in C3H/HeN mice, but not in Toll-like receptor 4 (TLR4)-mutant C3H/HeJ mice, by reducing serum levels of IL-17 and IL-23, while increasing interferon (IFN)-γ levels. The antitumor activity and IFN-γ production were mediated by T cells. Moreover, in vitro experiments showed that Spirulina LPS impaired the antigen-presenting function that supports the generation of IL-17-producing cells in a toll-like receptor (TLR)4-dependent manner. Of note, injection of anti-IL-17 antibody in tumor-bearing C3H/HeN mice in the absence of Spirulina LPS markedly suppressed tumor growth and augmented IFN-γ responses. Thus, our results support the notion that IFN-γ and IL-17/IL-23 mutually regulate Th17 and Th1 responses in tumor-bearing hosts, and Spirulina LPS modulates the balance of the IFN-γ-IL-17/IL-23 axis towards IFN-γ production, which leads to tumor inhibition. Furthermore, Spirulina LPS effectively inhibited the spontaneous development of mammary tumors. This study has important implications for the exploitation of TLR-based immunomodulators for cancer immunotherapy.

Long term effect of curcumin in restoration of tumour suppressor p53 and phase-II antioxidant enzymes via activation of Nrf2 signalling and modulation of inflammation in prevention of cancer.

Inhibition of carcinogenesis may be a consequence of attenuation of oxidative stress via activation of antioxidant defence system, restoration and stabilization of tumour suppressor proteins along with modulation of inflammatory mediators. Previously we have delineated significant role of curcumin during its long term effect in regulation of glycolytic pathway and angiogenesis, which in turn results in prevention of cancer via modulation of stress activated genes. Present study was designed to investigate long term effect of curcumin in regulation of Nrf2 mediated phase-II antioxidant enzymes, tumour suppressor p53 and inflammation under oxidative tumour microenvironment in liver of T-cell lymphoma bearing mice. Inhibition of Nrf2 signalling observed during lymphoma progression, resulted in down regulation of phase II antioxidant enzymes, p53 as well as activation of inflammatory signals. Curcumin potentiated significant increase in Nrf2 activation. It restored activity of phase-II antioxidant enzymes like GST, GR, NQO1, and tumour suppressor p53 level. In addition, curcumin modulated inflammation via upregulation of TGF-ß and reciprocal regulation of iNOS and COX2. The study suggests that during long term effect, curcumin leads to prevention of cancer by inducing phase-II antioxidant enzymes via activation of Nrf2 signalling, restoration of tumour suppressor p53 and modulation of inflammatory mediators like iNOS and COX2 in liver of lymphoma bearing mice.

Tumor growth retardation and chemosensitizing action of fatty acid synthase inhibitor orlistat on T cell lymphoma: implication of reconstituted tumor microenvironment and multidrug resistance phenotype.

BACKGROUND: Orlistat, a fatty acid synthase (FASN) inhibitor, has been demonstrated to inhibit tumor cell survival. However, the mechanism(s) of its tumor growth retarding action against malignancies of hematological origin remains unclear. It is also not understood if the antitumor action of orlistat implicates modulated susceptibility of tumor cell to anticancer drugs. Therefore, the present investigation focuses to study the antitumor and chemosensitizing action of orlistat in a murine host bearing a progressively growing T cell lymphoma. METHODS: Tumor-bearing mice were administered with vehicle alone or containing orlistat followed by administration of PBS with or without cisplatin. Tumor progression and survival of tumor-bearing host were monitored along with analysis of tumor cell survival and apoptosis. Tumor ascitic fluid was examined for pH, NO and cytokines. Expression of genes and proteins was investigated by RT-PCR and western blot respectively. ROS was analyzed by DCFDA staining and FASN activity by spectrophotometry. RESULTS: Orlistat administration to tumor-bearing mice resulted in tumor growth retardation, prolonged life span, declined tumor cell survival and chemosensitization to cisplatin. It was accompanied by increased osmotic fragility, modulated acidosis, expression of ROS, NO, cytokines, MCT-1 and VH(+) ATPase, Bcl2, Caspase-3, P53, inhibited FASN activity and declined expression of MDR and MRP-1 proteins. CONCLUSION: Orlistat manifests antitumor and chemosensitizing action implicating modulated regulation of cell survival, reconstituted-tumor microenvironment and altered MDR phenotype. GENERAL SIGNIFICANCE: These observations indicate that orlistat could be utilized as an adjunct regimen for improving antitumor efficacy of cisplatin.

Imatinib disrupts lymphoma angiogenesis by targeting vascular pericytes.

Pericytes and vascular smooth muscle cells (VSMCs), which are recruited to developing blood vessels by platelet-derived growth factor BB, support endothelial cell survival and vascular stability. Here, we report that imatinib, a tyrosine kinase inhibitor of platelet-derived growth factor receptor ß (PDGFRß), impaired growth of lymphoma in both human xenograft and murine allograft models. Lymphoma cells themselves neither expressed PDGFRß nor were growth inhibited by imatinib. Tumor growth inhibition was associated with decreased microvascular density and increased vascular leakage. In vivo, imatinib induced apoptosis of tumor-associated PDGFRß(+) pericytes and loss of perivascular integrity. In vitro, imatinib inhibited PDGFRß(+) VSMC proliferation and PDGF-BB signaling, whereas small interfering RNA knockdown of PDGFRß in pericytes protected them against imatinib-mediated growth inhibition. Fluorescence-activated cell sorter analysis of tumor tissue revealed depletion of pericytes, endothelial cells, and their progenitors following imatinib treatment. Compared with imatinib, treatment with an anti-PDGFRß monoclonal antibody partially inhibited lymphoma growth. Last, microarray analysis (Gene Expression Omnibus database accession number GSE30752) of PDGFRß(+) VSMCs following imatinib treatment showed down-regulation of genes implicated in vascular cell proliferation, survival, and assembly, including those representing multiple pathways downstream of PDGFRß. Taken together, these data indicate that PDGFRß(+) pericytes may represent a novel, nonendothelial, antiangiogenic target for lymphoma therapy.

T-cell receptor diversity prevents T-cell lymphoma development.

Mature T-cell lymphomas (MTCLs) have an extremely poor prognosis and are much less frequent than immature T-cell leukemias. This suggests that malignant outgrowth of mature T lymphocytes is well controlled. Indeed, in a previous study we found that mature T cells are resistant to transformation with known T-cell oncogenes. Here, however, we observed that T-cell receptor (TCR) mono-/oligoclonal mature T cells from TCR transgenic (tg) mice (OT-I, P14) expressing the oncogenes NPM/ALK or ΔTrkA readily developed MTCLs in T-cell-deficient recipients. Analysis of cell surface markers largely ruled out that TCR tg lymphomas were derived from T-cell precursors. Furthermore, cotransplanted non-modified TCR polyclonal T cells suppressed malignant outgrowth of oncogene expressing TCR tg T lymphocytes. A dominant role of an anti-leukemic immune response or Tregs in the control of MTCLs seems unlikely as naïve T cells derived from oncogene expressing stem cells, which should be tolerant to leukemic antigens, as well as purified CD4 and CD8 were resistant to transformation. However, our results are in line with a model in which homeostatic mechanisms that stabilize the diversity of the normal T-cell repertoire, for example, clonal competition, also control the outgrowth of potentially malignant T-cell clones. This study introduces a new innate mechanism of lymphoma control.

Alcohol intake and the incidence of non-hodgkin lymphoid neoplasms in the cancer prevention study II nutrition cohort.

Although several studies have shown a lower risk of non-Hodgkin lymphoma (NHL) in alcohol drinkers compared with nondrinkers, the dose-response relation and potential differences between former and current drinking and across beverage types and subtypes are unclear. The authors examined associations of alcohol intake with risk of NHL and NHL subtypes in the Cancer Prevention Study II Nutrition Cohort, a prospective study of US men and women aged 50-74 years. Between 1992 and 2007, there were 1,991 incident NHL cases among 143,124 participants. Multivariable-adjusted relative risks and 95% confidence intervals were computed using Cox proportional hazards regression. Compared with nondrinkers, the relative risk of NHL associated with former drinking was 0.90 (95% confidence interval (CI): 0.75, 1.10); the relative risks associated with current intakes of <1, 1-2, and >2 drinks/day were 0.93 (95% CI: 0.83, 1.03), 0.91 (95% CI: 0.78, 1.06), and 0.78 (95% CI: 0.65, 0.93), respectively. Associations did not differ by sex (P-interaction = 0.45) or beverage type (P-difference = 0.22). Alcohol intake was more strongly associated with B-cell lymphoma (P-trend = 0.005) than with T-cell lymphoma (P-trend = 0.76), and associations were similar among B-cell lymphoma subtypes. In this prospective study, current heavy alcohol intake was associated with a reduced risk of NHL. Associations did not differ by beverage type and were slightly stronger for B-cell tumors than for T-cell tumors.

Alginate encapsulated cells secreting Fas-ligand reduce lymphoma carcinogenicity.

Fas ligand (CD95L/APO-1) is considered as a potent anti-tumor agent due to its mediated cell death properties. We have designed a polymeric microencapsulation system, which encapsulates soluble FasL secreting cells. The encapsulated cells continuously release soluble FasL (sFasL) at the tumor site, while the device protects the encapsulated cells from the host immune system. The potential and efficacy of this system are demonstrated in vitro and in vivo for tumor inhibition. Polymeric microcapsules composed of Alginate Poly-l-lysine were optimized to encapsulate L5 secreting sFasL cells. The expression and anti-tumor activities of the sFasL were confirmed in vitro and tumor inhibition was studied in vivo in SCID mice bearing subcutaneous lymphoma tumors. In vitro, sFasL secreted by the encapsulated L5-sFasL cells was biologically active, inhibited proliferation and induced apoptotic cell death in Fas sensitive tumor cells. Mice injected with encapsulated L5-sFasL cells on the day of tumor injection or 10 days after tumor injection showed significant reduction in tumor volume, of 87% and 95%, respectively. Our findings show that encapsulated cells expressing sFasL can be used as a local device and efficiently suppress malignant Fas sensitive tumors with no side effects.

Vesicular stomatitis virus oncolytic treatment interferes with tumor-associated dendritic cell functions and abrogates tumor antigen presentation.

Oncolytic virotherapy is a promising biological approach to cancer treatment that contributes to tumor eradication via immune- and non-immune-mediated mechanisms. One of the remaining challenges for these experimental therapies is the necessity to develop a durable adaptive immune response against the tumor. Vesicular stomatitis virus (VSV) is a prototypical oncolytic virus (OV) that exemplifies the multiple mechanisms of oncolysis, including direct cell lysis, cellular hypoxia resulting from the shutdown of tumor vasculature, and inflammatory cytokine release. Despite these properties, the generation of sustained antitumor immunity is observed only when VSV is engineered to express a tumor antigen directly. In the present study, we sought to increase the number of tumor-associated dendritic cells (DC) in vivo and tumor antigen presentation by combining VSV treatment with recombinant Fms-like tyrosine kinase 3 ligand (rFlt3L), a growth factor promoting the differentiation and proliferation of DC. The combination of VSV oncolysis and rFLt3L improved animal survival in two different tumor models, i.e., VSV-resistant B16 melanoma and VSV-sensitive E.G7 T lymphoma; however, increased survival was independent of the adaptive CD8 T cell response. Tumor-associated DC were actively infected by VSV in vivo, which reduced their viability and prevented their migration to the draining lymph nodes to prime a tumor-specific CD8 T cell response. These results demonstrate that VSV interferes with tumor DC functions and blocks tumor antigen presentation.

The role of microRNA-150 as a tumor suppressor in malignant lymphoma.

MicroRNA (miRNA; miR) is a class of small regulatory RNA molecules, the aberrant expression of which can lead to the development of cancer. We recently reported that overexpression of miR-21 and/or miR-155 leads to activation of the phosphoinositide 3-kinase (PI3K)-AKT pathway in malignant lymphomas expressing CD3(-)CD56(+) natural killer (NK) cell antigen. Through expression analysis, we show in this study that in both NK/T-cell lymphoma lines and samples of primary lymphoma, levels of miR-150 expression are significantly lower than in normal NK cells. To examine its role in lymphomagenesis, we transduced miR-150 into NK/T-cell lymphoma cells, which increased the incidence of apoptosis and reduced cell proliferation. Moreover, the miR-150 transductants appeared senescent and showed lower telomerase activity, resulting in shortened telomeric DNA. We also found that miR-150 directly downregulated expression of DKC1 and AKT2, reduced levels of phosphorylated AKT(ser473/4) and increased levels of tumor suppressors such as Bim and p53. Collectively, these results suggest that miR-150 functions as a tumor suppressor, and that its aberrant downregulation induces continuous activation of the PI3K-AKT pathway, leading to telomerase activation and immortalization of cancer cells. These findings provide new insight into the pathogenesis of malignant lymphoma.

Methyl gallate exhibits potent antitumor activities by inhibiting tumor infiltration of CD4+CD25+ regulatory T cells.

CD4(+)CD25(+) regulatory T (Treg) cells play crucial roles in the host response to tumors. Increasing evidence supports the existence of elevated numbers of Treg cells in solid tumors and hematologic malignancies. In this study, the effects of methyl gallate on Treg cells were examined. Methyl gallate inhibited Treg cell-suppressive effects on effector CD4(+) T cells and Treg migration toward tumor environment. The expression of Treg surface markers including CTLA-4, CCR4, CXCR4, and glucocorticoid-induced TNFR was significantly suppressed upon methyl gallate treatment. Furthermore, forkhead box P3 (Foxp3) expression was also significantly decreased by methyl gallate, suggesting that the suppressive effects of methyl gallate on Treg were medicated by decrease of Treg-specific transcription factor Foxp3. In tumor-bearing hosts, methyl gallate treatment substantially reduced tumor growth and prolonged the survival rate. In contrast, nu/nu mice did not show decreased tumor progression in response to methyl gallate. In addition, in tumor-bearing Treg-depleted mice, tumor growth and the survival rates were not changed by methyl gallate treatment, strongly suggesting that the main therapeutic target of methyl gallate in tumor suppression was related to modulation of the CD4(+)CD25(+) Treg cell functions. In the spleen of tumor-bearing mice, methyl gallate treatment induced a significant decrease in the CD4(+)CD25(+)Foxp3(high) Treg cell population. Especially, the number of tumor-infiltrating CD25(+)Foxp3(high) Treg cells was significantly lower in methyl gallate-treated mice. These results suggest that methyl gallate can be used to reverse immune suppression and as a potentially useful adjunct for enhancing the efficacy of immune-based cancer therapy.

CTL induction of tumoricidal nitric oxide production by intratumoral macrophages is critical for tumor elimination.

To characterize mechanisms of CTL inhibition within an ocular tumor microenvironment, tumor-specific CTLs were transferred into mice with tumors developing within the anterior chamber of the eye or skin. Ocular tumors were resistant to CTL transfer therapy whereas skin tumors were sensitive. CTLs infiltrated ocular tumors at higher CTL/tumor ratios than in skin tumors and demonstrated comparable ex vivo effector function to CTLs within skin tumors indicating that ocular tumor progression was not due to decreased CTL accumulation or inhibited CTL function within the eye. CD11b(+)Gr-1(+)F4/80(-) cells predominated within ocular tumors, whereas skin tumors were primarily infiltrated by CD11b(+)Gr-1(-)F4/80(+) macrophages (Ms), suggesting that myeloid derived suppressor cells may contribute to ocular tumor growth. However, CD11b(+) myeloid cells isolated from either tumor site suppressed CTL activity in vitro via NO production. Paradoxically, the regression of skin tumors by CTL transfer therapy required NO production by intratumoral Ms indicating that NO-producing intratumoral myeloid cells did not suppress the effector phase of CTL. Upon CTL transfer, tumoricidal concentrations of NO were only produced by skin tumor-associated Ms though ocular tumor-associated Ms demonstrated comparable expression of inducible NO synthase protein suggesting that NO synthase enzymatic activity was compromised within the eye. Correspondingly, in vitro-activated Ms limited tumor growth when co-injected with tumor cells in the skin but not in the eye. In conclusion, the decreased capacity of Ms to produce NO within the ocular microenvironment limits CTL tumoricidal activity allowing ocular tumors to progress.

Fish oil delays lymphoma progression in the TLL mouse.

The objective was to investigate the effects of omega-3 fatty acids, known for their anti-inflammatory effects, on time to lymphoma progression and survival in the TLL mouse, a strain genetically prone to developing aggressive T-cell lymphoma. Compared to mice fed a standard diet, TLL mice fed omega-3 (menhaden fish oil) experienced a significant delay in disease progression and were more likely to remain alive and symptom free during the first 8 months of the study. In contrast, omega-6 supplementation (corn oil) did not significantly affect lymphoma progression. Irrespective of diet, all mice eventually progressed, and 1-year survival was not different between the groups. Immunological analysis demonstrated a significantly altered B-cell compartment and fewer NK cells in healthy C57Black6 mice fed omega-3, compared to controls. In conclusion, a diet rich in omega-3 fatty acids delays lymphoma development in the TLL mouse possibly by mechanisms that include complex effects on immune function.

Expression of IFNγR2 mutated in a dileucine internalization motif reinstates IFNγ signaling and apoptosis in human T lymphocytes.

In T lymphocytes, the internalization of the R2 chain of the IFN-γ receptor (IFN-γR2) prevents the switching-on of pro-apoptotic and anti-proliferative genes induced by the IFN-γ/STAT1 pathway. In fibroblasts, a critical role of controlling the IFN-γR2 internalization is played by the LI(255-256) intracellular motif. Here we show that, in human malignant T cells, the expression of a mutated IFN-γR2 chain in which the LI(255-256) internalization motif is replaced by two alanines (LI(255-256)AA) induces cell surface accumulation of the receptor and reinstates the cell sensitivity to IFN-γ. In comparison with T cells that expressed wild-type IFN-γR2, cells that expressed the mutated receptor displayed, in response to IFN-γ a sustained activation of STAT1. The activation of this signaling pathway leads to higher induction of MHC class I and FasL expression and triggered apoptosis. Malignant ST4 cells transduced with either wild-type or mutated receptor were able to grow in SCID mice, but only the proliferation of T cells expressing the mutated receptor was inhibited by IFN-γ. Finally, lentiviral-mediated transduction of the mutated receptor in T lymphoblasts from healthy donors reinstated their IFN-γ-dependent apoptosis. As a whole, these data indicate that perturbation of IFN-γR2 internalization by mutating the LI(255-256) motif induces a timely coordinated activation of IFN-γ/STAT1 signaling pathways that leads to the apoptosis of T cells.