Radiation and inhibition of angiogenesis by canstatin synergize to induce HIF-1alpha-mediated tumor apoptotic switch.

Tumor radioresponsiveness depends on endothelial cell death, which leads in turn to tumor hypoxia. Radiation-induced hypoxia was recently shown to trigger tumor radioresistance by activating angiogenesis through hypoxia-inducible factor 1-regulated (HIF-1-regulated) cytokines. We show here that combining targeted radioiodide therapy with angiogenic inhibitors, such as canstatin, enhances direct tumor cell apoptosis, thereby overcoming radio-induced HIF-1-dependent tumor survival pathways in vitro and in vivo. We found that following dual therapy, HIF-1alpha increases the activity of the canstatin-induced alpha(v)beta(5) signaling tumor apoptotic pathway and concomitantly abrogates mitotic checkpoint and tetraploidy triggered by radiation. Apoptosis in conjunction with mitotic catastrophe leads to lethal tumor damage. We discovered that HIF-1 displays a radiosensitizing activity that is highly dependent on treatment modalities by regulating key apoptotic molecular pathways. Our findings therefore support a crucial role for angiogenesis inhibitors in shifting the fate of radiation-induced HIF-1alpha activity from hypoxia-induced tumor radioresistance to hypoxia-induced tumor apoptosis. This study provides a basis for developing new biology-based clinically relevant strategies to improve the efficacy of radiation oncology, using HIF-1 as an ally for cancer therapy.

Role of bone marrow-derived CC-chemokine receptor 5 in the development of atherosclerosis of low-density lipoprotein receptor knockout mice.

OBJECTIVE: CC chemokine receptor CCR5 is expressed by atheroma-associated cells and could mediate leukocyte attraction into developing lesions. We examined the role of bone marrow-derived CCR5 in the development of atherosclerotic lesions after 8, 12, or 35 weeks of high-fat diet. METHODS AND RESULTS: Low-density lipoprotein-receptor (LDLr)-deficient mice were lethally irradiated and transplanted with CCR5+/+ or CCR5-/- bone marrow. After 8 weeks of fat diet, CCR5 deficiency in leukocytes led to 30% decrease of macrophage accumulation within the fatty streak (P<0.05), with no change in lesion size. After 12 weeks of fat diet, CCR5 deficiency also resulted in 30% decrease of plaque-macrophage accumulation (P<0.005), associated with 16% reduction in lesion size in the aortic sinus (P=0.13), despite a significant increase in total cholesterol levels (P=0.03). Lesions with CCR5 deficiency showed 52% reduction in matrix metalloproteinase (MMP)-9 expression (P=0.02) and 2-fold increase in collagen accumulation (P<0.0001). These changes were associated with a significant increase of interleukin (IL)-10 mRNA expression in spleens of CCR5-/- mice compared with CCR5+/+ controls. In addition, we found enhanced IL-10 production by CCR5-deficient peritoneal macrophages and decreased tumor necrosis factor (TNF)-alpha production by CCR5-/- T cells in comparison with CCR5+/+ controls. CCR5-/- and CCR5+/+ reconstituted animals showed no differences in plaque size or composition after 35 weeks of high-fat diet despite the persistent absence of CCR5 in plaques of mice reconstituted with CCR5-/- bone marrow. CONCLUSIONS: Bone marrow-derived CCR5 favors the development of an inflammatory and collagen-poor plaque phenotype in association with decreased macrophage-derived IL-10 and enhanced T cell-derived TNF-alpha. These effects are not sustained in the very advanced stages of atherosclerosis.

Leukocyte-derived interleukin 10 is required for protection against atherosclerosis in low-density lipoprotein receptor knockout mice.

BACKGROUND: Atherosclerosis is an immunoinflammatory disease. Here we examined the role of leukocyte-derived interleukin 10 (IL-10) on advanced atherosclerosis development in low-density lipoprotein receptor knockout (LDLr-/-) mice. METHODS AND RESULTS: Bone marrow cells harvested from C57BL/6 IL-10-/- and IL-10+/+ mice were transplanted into irradiated male LDLr-/- mice. Four weeks after transplantation, mice were fed a high-fat cholate-free diet for 14 weeks. Despite no differences in weights, serum total, and HDL-cholesterol levels between the 2 groups, IL-10 deficiency in leukocytes induced a >2-fold increase in lesion development in the thoracic aorta compared with controls. We also found a significant 35% increase in aortic root lesion area of IL-10-/- mice compared with IL-10+/+ mice. Furthermore, IL-10 deficiency led to a marked increase in lymphocyte and macrophage accumulation associated with a significant reduction in collagen accumulation. Finally, transfer of IL-10-/- splenocytes to LDLr-/- mice resulted in a 3-fold increase in lesion size in the aortic sinus compared with mice transplanted with IL-10+/+ splenocytes. CONCLUSIONS: IL-10 expressed by leukocytes prevents exaggerated advanced atherosclerosis development and plays a critical role in modulation of cellular and collagen plaque composition, at least in part, through a modulation of the systemic immune response.

Chemokine receptor CCR1 disruption in bone marrow cells enhances atherosclerotic lesion development and inflammation in mice.

Several chemokines or chemokine receptors are involved in atherogenesis. CCR1 is expressed by macrophages and lymphocytes, two major cell types involved in the progression of atherosclerosis, and binds to lesion-expressed ligands. We examined the direct role of the blood-borne chemokine receptor CCR1 in atherosclerosis by transplanting bone marrow cells from either CCR1+/+ or CCR1-/- mice into low-density lipoprotein-receptor (LDLr)-deficient mice. After exposure to an atherogenic diet for 8 weeks, no differences in fatty streak size or composition were detected between the 2 groups. After 12 weeks of atherogenic diet, however, an unexpected 70% increase in atherosclerotic lesion size in the thoracic aorta was detected in the CCR1-/- mice, accompanied by a 37% increase in the aortic sinus lesion area. CCR1-/- mice showed enhanced basal and concanavalin A-stimulated IFN-gamma production by spleen T cells and enhanced plaque inflammation. In conclusion, blood-borne CCR1 alters the immuno-inflammatory response in atherosclerosis and prevents excessive plaque growth and inflammation.

IL-2 production by dendritic cells is not critical for the activation of cognate and innate effectors in draining lymph nodes.

Dendritic cells (DC) are unique antigen-presenting cells capable of triggering NK cell effector functions and priming naive T cells in vivo. Microbial stimulation induces early IL-2 production by mouse DC. Previous reports demonstrated that IL-2 is enriched at the site of DC/T cell interaction and promotes allogeneic T cell proliferation. However, the direct role of DC-derived IL-2 in the differentiation of cytotoxic T lymphocytes and in NK cell triggering in vivo has not been investigated. Lipopolysaccharide (LPS) stimulation of mouse bone marrow-derived DC results in early IL-2 production unless IL-4 is introduced in DC cultures. Here we show that IL-2 produced by LPS-activated DC is dispensable for cognate T cell responses since IL-2 loss of function DC elicit OVA-specific Tc1 effector and memory lymphocytes in draining lymph nodes in a setting where ex vivo cultured DC do not transfer antigens to host DC. Moreover, adoptively transferred IL-2 loss of function DC maintain their capacity to trigger NK cell proliferation/recruitment in lymph nodes. Therefore, immediate inducible IL-2 production by DC following microbial infection might play a regulatory role at ports of entry rather than in secondary lymphoid organs.

Specific abrogation of transforming growth factor-beta signaling in T cells alters atherosclerotic lesion size and composition in mice.

A large body of evidence supports a role for proinflammatory mediators in atherosclerotic disease progression and instability. However, only few endogenous mechanisms have been suggested that could alter disease progression. One such mechanism is thought to be mediated by transforming growth factor beta (TGF-beta). Transgenic mice that express a dominant-negative TGF-beta receptor type II under a T-cell-specific promoter were generated. Bone marrow transplantation from transgenic mice into irradiated low density lipoprotein receptor knock-out (LDLr KO) mice, subsequently fed an atherogenic diet, resulted in T-cell-specific blockade of TGF-beta signaling in the recipient mice and increased differentiation of T cells toward both T helper 1 (Th1) and Th2 phenotypes. These mice showed a significant decrease in atherosclerotic lesion size in the aortic sinus compared with mice receiving transplants with the wild-type bone marrow. Atherosclerotic plaques of mice receiving transplants with the transgenic bone marrow showed increased T-cell infiltration and expression of major histocompatability complex (MHC) class II, along with a decrease in smooth muscle cell and collagen content, a plaque phenotype that is potentially vulnerable to rupture. These results identify for the first time an important role for specific and selective T-cell-TGF-beta signaling in atherosclerosis.

Pharmacokinetic advantage of intra-arterial hepatic oxaliplatin administration: comparative results with cisplatin using a rabbit VX2 tumor model.

The aim of this study was to compare intra-arterial hepatic administration (IAH) versus i.v. administration of oxaliplatin and cisplatin in a VX2 tumor model in rabbits. VX2 tumors were implanted in the livers of White New Zealand female rabbits and 2 weeks later they received either cisplatin (4 mg/kg) or oxaliplatin (6 mg/kg) administered by IAH or i.v. Platinum pharmacokinetic parameters were measured by atomic absorption spectrometry at baseline, 2, 5 10, 20, 40 and 60 min, and then at 2, 4, 6 and 24 h after drug administration. Animals were sacrificed 24 h after drug administration to measure platinum concentrations in various tissues. After IAH oxaliplatin administration, we observed a significant decrease for total and filterable platinum in the Cmax compared with i.v. administration (12.4 versus 18.2 microg/l; p=0.02 and 11.2 versus 17.3 microg/l; p=0.02, respectively). Significant differences in various tissue concentrations were reported when comparing IAH and i.v. administration of oxaliplatin with IAH administration offering an advantage over i.v. administration. No differences in pharmacokinetic parameters or platinum tissue accumulation were apparent between the IAH and i.v. administration with cisplatin. We conclude that there is a significant pharmacokinetic advantage to using oxaliplatin for locoregional IAH chemotherapy compared with i.v. administration.