Amy Richmond

Sunitinib Reverses Type-1 Immune Suppression and Decreases T-Regulatory Cells in Renal Cell Carcinoma Patients

Purpose: Immune dysfunction is well documented in renal cell carcinoma (RCC) patients and likely contributes to tumor evasion. This dysfunction includes a shift from a type-1 to a type-2 T-cell cytokine response and enhanced T-regulatory (Treg) cell expression. Given the antitumor activity of select tyrosine kinase inhibitors such as sunitinib in metastatic RCC (mRCC) patients, it is relevant to assess their effect on the immune system. Experimental Design: Type-1 (IFNγ) and type-2 (interleukin-4) responses were assessed in T cells at baseline and day 28 of treatment with sunitinib (50 mg/d) by measuring intracellular cytokines after in vitro stimulation with anti-CD3/anti-CD28 antibodies. Results: After one cycle of treatment, there was a significant increase in the percentage of IFNγ-producing T cells (CD3+, P < 0.001; CD3+CD4+, P = 0.001), a reduction in interleukin-4 production (CD3+ cells, P = 0.05), and a diminished type-2 bias (P = 0.005). The increase in type-1 response may be partly related to modulation of Treg cells. The increased percentage of Treg cells noted in mRCC patients over healthy donors (P = 0.001) was reduced after treatment, although not reaching statistical significance. There was, however, an inverse correlation between the increase in type-1 response after two cycles of treatment and a decrease in the percentage of Treg cells (r = −0.64, P = 0.01). In vitro studies suggest that the effects of sunitinib on Treg cells are indirect. Conclusions: The demonstration that sunitinib improved type-1 T-cell cytokine response in mRCC patients while reducing Treg function provides a basis for the rational combination of sunitinib and immunotherapy in mRCC.

ATG16L1 and NOD2 Interact in an Autophagy-Dependent Antibacterial Pathway Implicated in Crohn's Disease Pathogenesis

BACKGROUND & AIMS The identification of numerous genes that confer susceptibility to Crohns disease (CD) indicates that this complex disease might arise from alterations in several genes with related functions. We examined the functional interaction between the CD risk genes ATG16L1 and NOD2 to identify an autophagy-dependent pathway that is altered by disease-associated variants. METHODS We assessed Nod2 signaling and autophagy activation in response to muramyl dipeptide (MDP) by immunoblot, confocal microscopy, flow cytometry, reporter gene, and gentamicin protection assays in human epithelial cell lines and primary human macrophages and dendritic cells from healthy individuals. The requirement of Nod2 and ATG16L1 expression and the effects of CD-associated variants in MDP-stimulated autophagy and Nod2-dependent signaling were assessed in cell lines manipulated by RNA interference, inhibitors, or ATG16L1 or NOD2 variants and in primary macrophages and dendritic cells from healthy genotyped donors. RESULTS MDP stimulation of epithelial cells, macrophages, and dendritic cells activated autophagy and nuclear factor κB and mitogen-activated protein kinase signaling; it also increased killing of Salmonella. These responses depended on ATG16L1 and Nod2 expression and were impaired by CD-associated NOD2 variants. Nod2-dependent signaling was not impaired in cells with the ATG16L1 T300A genotype, which is associated with CD. However, the ATG16L1 T300A variant blocked the increase in MDP-mediated killing of Salmonella only in epithelial cell lines and not primary macrophages or dendritic cells. CONCLUSIONS ATG16L1 and NOD2 are components of an autophagy-mediated antibacterial pathway that is altered in a cell- and function-specific manner by CD-associated mutations.

Glioblastomas Induce T-Lymphocyte Death by Two Distinct Pathways Involving Gangliosides and CD70

Here we report that glioblastoma multiforme (GBM) mediates immunosuppression by promoting T-cell death via tumor-associated CD70 and gangliosides that act through receptor-dependent and receptor-independent pathways, respectively. GBM lines cocultured with T cells induced lymphocyte death. The GBM lines were characterized for their expression of CD70, Fas ligand (FasL), and tumor necrosis factor-alpha (TNF-alpha), and the possible participation of those molecules in T-cell killing was assessed by doing GBM/T cell cocultures in the presence of anti-CD70 antibodies, Fas fusion proteins, or anti-TNF-alpha antibodies. CD70 but not TNF-alpha or FasL is responsible for initiating T-cell death via the receptor-dependent pathway. Of the four GBM cell lines that induced T-cell death, three highly expressed CD70. Two nonapoptogenic GBM lines (CCF3 and U138), on the other hand, had only minimally detectable CD70 expression. Blocking experiments with the anti-CD70 antibody confirmed that elevated CD70 levels were involved in the apoptogenicity of the three GBM lines expressing that molecule. Gangliosides were found to participate in the induction of T-cell apoptosis, because the glucosylceramide synthase inhibitor (PPPP) significantly reduced the abilities of all four apoptogenic lines to kill the lymphocytes. High-performance liquid chromatography (HPLC) and mass spectroscopy revealed that GM2, GM2-like gangliosides, and GD1a were synthesized in abundance by all four apoptogenic GBM lines but not by the two GBMs lacking activity. Furthermore, gangliosides isolated from GBM lines as well as HPLC fractions containing GM2 and GD1a were directly apoptogenic for T cells. Our results indicate that CD70 and gangliosides are both products synthesized by GBMs that may be key mediators of T-cell apoptosis and likely contribute to the T-cell dysfunction observed within the tumor microenvironment.

GM2 Expression in Renal Cell Carcinoma: Potential Role in Tumor-Induced T-Cell Dysfunction

Multiple mechanisms have been proposed to account for immune escape by tumors. Although gangliosides have long been known to suppress T-cell immunity, few studies have examined the effect of human tumor-derived gangliosides on immune responses. Here, we show that gangliosides isolated from renal cell carcinoma (RCC) cell lines and clear cell tumor tissue can induce apoptosis in peripheral blood T cells. The RCC tissue-derived gangliosides also suppressed IFN-gamma and, in many cases, interleukin-4 production by CD4+ T cells at concentrations (1 ng/mL-100 pg/mL) well below those that induce any detectable T-cell death (4-20 microg/mL). Additional findings show that GM2 expressed by RCC plays a significant role in promoting T-cell dysfunction. This is supported by the demonstration that all RCC cell lines examined (n = 5) expressed GM2 as did the majority of tumors (15 of 18) derived from patients with clear cell RCC. Furthermore, an antibody specific for GM2 (DMF10.167.4) partially blocked (50-60%) T-cell apoptosis induced by coculturing lymphocytes with RCC cell lines or with RCC tissue-derived gangliosides. DMF10.167.4 also partially blocked the suppression of IFN-gamma production induced by RCC tissue-derived gangliosides, suggesting that GM2 plays a role in down-regulating cytokine production by CD4+ T cells.

Effect of Renal Cell Carcinomas on the Development of Type 1 T-Cell Responses

Purpose: We reported that in renal cell carcinoma patients with active disease, T-cell reactions to the tumor-associated antigens MAGE-6 and EphA2 are highly skewed toward TH2-type cytokine responses [interleukin (IL) 5]. Herein, we determined whether tumor-derived products, including gangliosides isolated from renal cell carcinoma patients, participate in the down-regulation of type 1 T-cell responses. Experimental Design: T cells from healthy volunteers or renal cell carcinoma patients were cultured in the presence and absence of supernatants derived from renal cell carcinoma explants or with gangliosides isolated from those tumor supernatants. T cells were stimulated or not with either autologous dendritic cells pulsed with superantigen (Staphylococcus enterotoxin B) or with phorbol 12-myristate 13-acetate and ionomycin and then were assessed for type 1 or type 2 responses (cytokine production and gene expression) and apoptosis. Results: Tumor supernatants efficiently inhibited the TH1-type responses [interferon (IFN) γ] of T cells stimulated with either S. enterotoxin B or phorbol 12-myristate 13-acetate and ionomycin but had no inhibitory effect on activated T-cell production of type 2 cytokines (IL-4, IL-5, and IL-10). Likewise, IFN-γ mRNA and protein production were inhibited when T cells were cocultured with either renal cell carcinoma supernatant-derived gangliosides or a commercial source of purified GD1a. It was also determined that gangliosides impair type 1 responses by inducing apoptosis of activated T cells. Conclusions: We propose that renal cell carcinoma-derived tumor products such as gangliosides can induce a type 2 bias in antitumor immunity by initiating apoptosis in the IFN-γ-producing type 1 effector cells. This represents a relevant mechanism by which renal cell carcinoma can inhibit protective antitumor immunity.

Clinical and Immunologic Effects of Subcutaneously Administered Interleukin-12 and Interferon Alfa-2b: Phase I Trial of Patients With Metastatic Renal Cell Carcinoma or Malignant Melanoma

PURPOSE Interleukin-12 (IL-12) and interferon alfa-2b (IFN-alpha-2b) are pleiotropic cytokines with activity in renal cell carcinoma (RCC) and malignant melanoma (MM) as single agents. Preclinical studies suggest concurrent administration may have synergistic antitumor effects. We conducted a phase I trial of concurrent subcutaneous (SC) administration of IL-12 and IFN-alpha-2b in patients with metastatic RCC or MM to determine toxicity, maximum-tolerated dose, preliminary efficacy, and effects on chemokine/cytokine gene expression in peripheral blood mononuclear cells (PBMCs). PATIENTS AND METHODS Cohorts of three to six patients were treated with escalating doses of IL-12 (dose I, 100 ng/kg; dose II, 300 ng/kg; dose III, 500 ng/kg; dose IV, 500 ng/kg SC) given twice weekly and IFN-alpha-2b (dose I, 1.0 MU/m(2); dose II, 1.0 MU/m(2); dose III, 1.0 MU/m(2); dose IV, 3.0 MU/m(2) SC) three times weekly in 4-week cycles. Effects on gene expression were assessed by reverse transcriptase polymerase chain reaction. RESULTS Twenty-six patients (19 with RCC, seven with MM) were accrued at dose levels I (n = 3), II (n = 3), III (n = 13), and IV (n = 7). Dose-limiting toxicity included grades 3 and 4 hepatotoxicity and neutropenia/leukopenia. Patients received a median of three cycles of treatment. Two patients with RCC and one patient with MM had partial responses. Median survival was 13.8 months. Reverse transcriptase polymerase chain reaction on PBMCs revealed induction of IP-10, Mig, B7.1 (CD80), interleukin-5, and interferon gamma in selected patients. CONCLUSION Concurrent SC administration of IL-12 and IFN-alpha-2b is possible at the dose levels utilized. Recommended doses for phase II trials are 500 ng/kg IL-12 and 1.0 MU/m(2) IFN-alpha-2b. Consistent induction of IP-10 and Mig, as well as variable induction of B7.1, interleukin-5, and interferon gamma expression was noted in PBMCs.

Elevated Levels of Select Gangliosides in T Cells from Renal Cell Carcinoma Patients Is Associated with T Cell Dysfunction

Increased expression of gangliosides by different tumor types including renal cell carcinoma (RCC) is thought to contribute to the immune suppression observed in cancer patients. In this study, we report an increase in apoptotic T cells from RCC patients compared with T cells from normal donors that coincided with the detection of T cells staining positive for GM2 and that the apoptosis was predominantly observed in the GM2+ but not the GM2− T cell population. Ganglioside shedding from tumor rather than endogenous production accounts for GM2+ T cells since there was no detectable level of mRNA for GM2 synthase in RCC patient T cells and in T cells from normal healthy donors after incubation with either purified GM2 or supernatant from RCC cell lines despite their staining positive for GM2. Moreover, reactive oxygen species as well as activated caspase 3, 8, and 9 were predominantly elevated in GM2+ but not GM2− T cells. Similarly, increased staining for GD2 and GD3 but not GD1a was detected with patient T cells with elevated levels of apoptosis in the GD2+ and GD3+ cells. These findings suggest that GM2, GD2, and GD3 play a significant role in immune dysfunction observed in RCC patient T cells.

The Nucleotide Synthesis Enzyme CAD Inhibits NOD2 Antibacterial Function in Human Intestinal Epithelial Cells

BACKGROUND & AIMS Polymorphisms that reduce the function of nucleotide-binding oligomerization domain (NOD)2, a bacterial sensor, have been associated with Crohns disease (CD). No proteins that regulate NOD2 activity have been identified as selective pharmacologic targets. We sought to discover regulators of NOD2 that might be pharmacologic targets for CD therapies. METHODS Carbamoyl phosphate synthetase/aspartate transcarbamylase/dihydroorotase (CAD) is an enzyme required for de novo pyrimidine nucleotide synthesis; it was identified as a NOD2-interacting protein by immunoprecipitation-coupled mass spectrometry. CAD expression was assessed in colon tissues from individuals with and without inflammatory bowel disease by immunohistochemistry. The interaction between CAD and NOD2 was assessed in human HCT116 intestinal epithelial cells by immunoprecipitation, immunoblot, reporter gene, and gentamicin protection assays. We also analyzed human cell lines that express variants of NOD2 and the effects of RNA interference, overexpression and CAD inhibitors. RESULTS CAD was identified as a NOD2-interacting protein expressed at increased levels in the intestinal epithelium of patients with CD compared with controls. Overexpression of CAD inhibited NOD2-dependent activation of nuclear factor κB and p38 mitogen-activated protein kinase, as well as intracellular killing of Salmonella. Reduction of CAD expression or administration of CAD inhibitors increased NOD2-dependent signaling and antibacterial functions of NOD2 variants that are and are not associated with CD. CONCLUSIONS The nucleotide synthesis enzyme CAD is a negative regulator of NOD2. The antibacterial function of NOD2 variants that have been associated with CD increased in response to pharmacologic inhibition of CAD. CAD is a potential therapeutic target for CD.

360 CAD, a Nucleotide Synthesis Enzyme, Inhibits NOD2 Anti-Bacterial Function in Human Intestinal Epithelial Cells

intense lymphangiogenesis is initially an appropriate and beneficial adaptation that ultimately becomes dysregulated due to the chronicity of inflammation, or is an abnormal response from the onset of IBD remains to be established. Methods: We addressed these issues In Vivo by systemic inhibition of the receptor VEGFR-3 or delivery of the lymphangiogenic factor VEGF-C in the dextran sulfate sodium (DSS) model of colitis by a blocking antibody or adenovirus transfer, respectively. Whole mount of proximal and distal colons were stained during acute and chronic colitis with antibodies against LYVE-1 and CD31 to measure area density and dimension of lymphatic vessels. Lymphatic drainagewas assessed by intramucosal injection of Evans blue dye. Moreover, In Vitro tubulogenesis was used to assess human intestinal lymphatic endothelial cells (HILEC) organization into capillary tubules using a Matrigel system. Results: Despite enhanced lymphangiogenesis, lymph flow was significantly reduced in DSS-induced colitis (p<0,001), particularly in the chronic stage. Systemic inhibition of VEGFR-3 blocked lymphangiogenesis, reducing both area density (from 35 ±0,8 to 14 ±0,3 vessels/mm2, p<0,01) and lymphatic vessel dimension (from 81 ±1,4 μm to 39 ±0,9 μm, p<0,01), while increasing inflammatory edema formation and inhibiting disease resolution, as assessed by weight loss, colitis activity index and histological score. In contrast, although lymphatic drainage was decreased in the chronic phase of colitis, it was enhanced by systemic delivery of the lymphangiogenic factor VEGF-C, which in turn significantly improved colitis both clinically and histologically. HILEC isolated from CD biopsies showed reduced capacity to undergo tubulogenesis In Vitro (30 ± 1,8 number of NL tubes vs 11 ± 0,5 number of CD tubes) and downregulation of VEGFR3 expression compared to healthy control tissues. Treatment with recombinant VEGFC induces tubulogenesis of CD HILEC while anti-VEGFR3 antibody inhibits tube formation of control HILEC, proving that VEGFR3 pathway is required for HILEC tubulogenesis and that reduced lymphatic function observed In Vivo is VEGFR3-dependent. Conclusion: Our findings demonstrate that stimulation of functional lymphangiogenesis via VEGFR-3 accelerates disease resolution and inhibits chronic inflammation. Correction of defective lymphatic function may therefore offer an entirely novel therapeutic strategy for IBD.