Bifidobacterium longum as a delivery system for cancer gene therapy: selective localization and growth in hypoxic tumors.
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A fundamental obstacle in gene therapy for cancer is the specific delivery of an anticancer gene product to a solid tumor, and yet no systemic delivery system that specifically targets solid tumors currently exists. A strain of domestic bacteria, Bifidobacterium longum, which is nonpathogenic and anaerobic, selectively localized and proliferated in several types of mouse solid tumors after systemic application. In this report, we further describe a novel approach to cancer gene therapy in which genetically engineered Bifidobacterium is used as a tumor-specific vector. Similarly to wild-type B. longum, genetically engineered B. longum could be detected in tumor tissue only and was not found in a large survey of normal mouse tissues after intravenous injection. This finding strongly suggests that obligate anaerobic bacteria such as Bifidobacterium can be used as highly specific gene delivery vectors for cancer gene therapy. (+info)
Secondary lymphoid tissue chemokine mediates T cell-dependent antitumor responses in vivo.
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Secondary lymphoid tissue chemokine (SLC, also referred to as Exodus 2 or 6Ckine) is a recently identified high endothelial-derived CC chemokine. The ability of SLC to chemoattract both Th1 lymphocytes and dendritic cells formed the rationale to evaluate this chemokine in cancer immunotherapy. Intratumoral injection of recombinant SLC evidenced potent antitumor responses and led to complete tumor eradication in 40% of treated mice. SLC-mediated antitumor responses were lymphocyte dependent as evidenced by the fact that this therapy did not alter tumor growth in SCID mice. Studies performed in CD4 and CD8 knockout mice also revealed a requirement for both CD4 and CD8 lymphocyte subsets for SLC-mediated tumor regression. In immunocompetent mice, intratumoral SLC injection led to a significant increase in CD4 and CD8 T lymphocytes and dendritic cells, infiltrating both the tumor and the draining lymph nodes. These cell infiltrates were accompanied by the enhanced elaboration of Th1 cytokines and chemokines monokine induced by IFN-gamma and IFN-gamma-inducible protein 10 but a concomitant decrease in immunosuppressive cytokines at the tumor site. In response to irradiated autologous tumor, splenic and lymph node-derived cells from SLC-treated tumor-bearing mice secreted significantly more IFN-gamma, GM-CSF, and IL-12 and reduced levels of IL-10 than did diluent-treated tumor-bearing mice. After stimulation with irradiated autologous tumor, lymph node-derived lymphocytes from SLC-treated tumor-bearing mice demonstrated enhanced cytolytic capacity, suggesting the generation of systemic immune responses. These findings provide a strong rationale for further evaluation of SLC in tumor immunity and its use in cancer immunotherapy. (+info)
Antitumor and antimetastatic activity of ribozymes targeting the messenger RNA of vascular endothelial growth factor receptors.
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Chemically stabilized hammerhead ribozymes are nuclease-resistant, RNA-based oligonucleotides that selectively bind and cleave specific target RNAs. Due to their potential for specifically inhibiting gene expression, ribozymes are being investigated for therapeutic applications as well as for the elucidation of gene function. In particular, we have investigated ribozymes that target the mRNA of the vascular endothelial growth factor (VEGF) receptors because VEGF signaling is an important mediator of tumor angiogenesis and metastasis. Here we report pharmacodynamic studies testing anti-Flt-1 (VEGFR-1) and anti-KDR (VEGFR-2) ribozymes in animal models of solid tumor growth and metastasis. Ribozymes targeting either Flt-1 or KDR significantly inhibited primary tumor growth in a highly metastatic variant of Lewis lung carcinoma. However, only treatment with the anti-Flt-1 ribozyme resulted in a statistically significant and dose-dependent inhibition of lung metastasis in this model. The anti-Flt-1 ribozyme was then tested in a xenograft model of human metastatic colorectal cancer in which significant inhibition of liver metastasis was observed. Taken together, these data represent the first demonstration that synthetic ribozymes targeting VEGF receptor mRNA reduced the growth and metastasis of solid tumors in vivo. (+info)
A 12(S)-hydroxyeicosatetraenoic acid receptor interacts with steroid receptor coactivator-1.
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Lewis lung carcinoma cells contain specific high-affinity binding sites for the eicosanoid 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid [12(S)-HETE]. These binding sites have a cytosolic/nuclear localization and contain the heat shock proteins hsp70 and hsp90 as components of a high molecular weight cytosolic binding complex. The ligand binding subunit of this complex is a protein with an apparent molecular mass of approximately 50 kDa as judged by gel permeation chromatography. In this report, we present data showing that the 50-kDa 12(S)-HETE binding protein interacts as a homodimer with steroid receptor coactivator-1 (SRC-1) in the presence of 12(S)-HETE. Two putative interaction domains were mapped. One of these (amino acids 701-781) was within the nuclear receptor interaction domain in SRC-1 required for binding of various steroid and thyroid hormone receptors. It contains the most C-terminal of the three copies of LXXLL motif present in the nuclear receptor interaction domain. The second interaction domain was present in the N-terminal part of SRC-1 (amino acids 1-221). This region has two LXXLL motifs, one does not bind and the other binds only weakly to steroid and thyroid hormone receptors. Glutathione S-transferase (GST) pulldown experiments and far Western analyses demonstrated that the N-terminal region of SRC-1 (amino acids 1-212) alone does not bind the 50-kDa 12(S)-HETE binding protein, whereas GST/DeltaSRC-1(1-1138) ligand-dependently pulled down a protein of approximately 50 kDa in size. Our results suggest that the 50-kDa 12(S)-HETE binding protein is a receptor that may signal through interaction with a nuclear receptor coactivator protein. (+info)
Isolation of a 41-kDa protein with cell adhesion activity for animal tumor cells from the mushroom Hypsizigus marmoreus by affinity chromatography with type IV collagen immobilized on agarose.
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A type IV collagen-binding protein of 41 kDa was isolated from the mushroom Hypsizigus marmoreus and the protein was designated as HM41. The Western blotting analysis with anti-HM41 antibodies demonstrated that HM41 was unrelated to HM23, which had been shown to have an affinity for type IV collagen. The microsequence analysis of the membrane-blotted peptides generated by fragmentation with cyanogen bromide showed no homologous proteins reported. HM41 had cell adhesion-promoting activity for murine Lewis lung carcinoma LL2 cells and human fibrosarcoma HT1080 cells. These results indicate that HM41 is a hitherto undescribed fungus protein that can interact both with animal extracellular matrix protein type IV collagen and with animal tumor cells. (+info)
Cyclooxygenase-2 (COX-2; Ptgs2) acts as a tumor promoter in rodent models for colorectal cancer, but its precise role in carcinogenesis remains unclear. We evaluated the contribution of host-derived COX-1 and COX-2 in tumor growth using both genetic and pharmacological approaches. Lewis lung carcinoma (LLC) cells grow rapidly as solid tumors when implanted in C57BL/6 mice. We found that tumor growth was markedly attenuated in COX-2(-/-), but not COX-1(-/-) or wild-type mice. Treatment of wild-type C57BL/6 mice bearing LLC tumors with a selective COX-2 inhibitor also reduced tumor growth. A decrease in vascular density was observed in tumors grown in COX-2(-/-) mice when compared with those in wild-type mice. Because COX-2 is expressed in stromal fibroblasts of human and rodent colorectal carcinomas, we evaluated COX-2(-/-) mouse fibroblasts and found a 94% reduction in their ability to produce the proangiogenic factor, VEGF. Additionally, treatment of wild-type mouse fibroblasts with a selective COX-2 inhibitor reduced VEGF production by 92%. (+info)
Therapeutic efficacy of the suicide gene driven by the promoter of vascular endothelial growth factor gene against hypoxic tumor cells.
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We examined whether herpes simplex virus thymidine kinase (HSV-TK) gene expression driven by the promoter of the vascular endothelial growth factor (VEGF) gene that is activated by hypoxia is effective in killing highly metastatic Lewis lung carcinoma A11 cells under hypoxic conditions. We isolated the promoter region encompassing the hypoxia response element (HRE) of the mouse VEGF gene. To assess the hypoxia responsiveness of the VEGF promoter, A11 cells were transiently transfected with luciferase reporter plasmids. Exposure of the transfectants to hypoxia resulted in a 2-3-fold induction of luciferase activity. Deletion of the HRE site abolished VEGF promoter activity under both normoxic and hypoxic conditions. We constructed a retroviral vector harboring the HSV-TK or green fluorescence protein (GFP) gene under the control of the VEGF promoter. A11 cells transfected with vector harboring the VEGF promoter fused to the HSV-TK gene [A11(HRE/TK) cells] were more sensitive to ganciclovir than cells transfected with the control vector harboring the VEGF promoter alone, and the sensitivity of the A11(HRE/TK) cells was increased by exposure to hypoxia followed by reoxygenation. Culturing A11 cells transfected with vector harboring the VEGF promoter fused to the GFP gene under hypoxic conditions resulted in an increase in the expression of GFP. Monitoring GFP expression and vascularity in the A11 transfectant tumors revealed up-regulation of GFP expression in poorly vascularized regions. Administration of ganciclovir to mice bearing s.c. tumors formed by A11(HRE/TK) cells resulted in regression of the tumors. These results suggest a possible application of the suicide gene driven by the VEGF promoter to cancer gene therapy that efficiently targets hypoxic tumor cells. (+info)
Porphyrin analogues as novel antagonists of fibroblast growth factor and vascular endothelial growth factor receptor binding that inhibit endothelial cell proliferation, tumor progression, and metastasis.
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Fibroblast growth factors (FGFs) and vascular endothelial growth factor (VEGF) play a pivotal role in the multistep pathway of tumor progression, metastasis, and angiogenesis. We have identified a porphyrin analogue, 5,10,15,20-tetrakis(methyl-4-pyridyl)-21H,23H-porphine-tetra -p-tosylate salt (TMPP), as a potent inhibitor of FGF2 and VEGF receptor binding and activation. TMPP demonstrated potent inhibition of binding of soluble FGF receptor 1 (FGFR1) to FGF2 immobilized on heparin at submicromolar concentrations. TMPP inhibits binding of radiolabeled FGF2 to FGFR in a cell-free system as well as to cells genetically engineered to express FGFR1. Furthermore, TMPP also inhibits the binding of VEGF to its tyrosine kinase receptor in a dose-dependent manner. In an in vitro angiogenic assay measuring the extent of endothelial cell growth, tube formation, and sprouting, TMPP dramatically reduced the extent of the FGF2-induced endothelial cell outgrowth and differentiation. In a Lewis lung carcinoma model, mice receiving TMPP showed a marked inhibition of both primary tumor progression and lung metastases development, with nearly total inhibition of the metastatic phenotype upon alternate daily injections of TMPP at 25 microg/g of body mass. Finally, novel meso-pyridylium-substituted, nonsymmetric porphyrins, as well as a novel corrole-based derivative, with >50-fold increase in activity in vitro, had a significantly improved efficacy in blocking tumor progression and metastasis in vivo. (+info)