Abstract LB148: Gamma delta T cells engineered with a chimeric PD-1 receptor effectively control PD-L1 positive tumors in vitro and in vivo with minimal toxicities

Introduction. Despite the overwhelming success of anti-CD19 CAR T cell therapies in recent years, it is still impossible to date to replicate comparable results in patients with solid tumors. Such obstacle is due to many factors, but the three most relevant ones are: a) the complex and immune-suppressive tumor microenvironment, b) the lack of optimal tumor targets that are not also expressed on normal cells and c) the use of autologous, patient-derived cells, which are frequently sub-optimal due to chemotherapy. Here we investigated a novel strategy to overcome these three barriers by using unconventional, MHC-independent gamma delta T cells and a chimeric PD-1 protein that was previously validated in murine conventional alpha-beta T cells. We tested the hypothesis that our strategy could specifically target cancer cells without a CAR for a specific tumor-associated antigen by turning PD-1 immune suppression into T-cell activation and using donor-derived, “off-the-shelf” effector cells. Experimental procedures. We built a chimeric PD-1 receptor consisting of the extracellular portion of PD-1 fused to the intracellular domains of DAP10 and CD3z. Gamma delta T cells from healthy donors were expanded ex vivo and stably transduced with a gamma-retrovirus-derived viral vector carrying the chimeric construct. Cells were tested for killing efficiency, cytokines secretion, and memory differentiation in vitro. We then evaluated the in vivo efficacy and tolerability in murine xenografts. Results. chPD1-gdT cells selectively killed PDL-1+ tumor cells, with minimal on-target/off-tumor toxicities and without off-target toxicities. Cells were well tolerated in mice, without damage to normal PD-L1+ cells. Upon contact with PD-L1+ cancers, chPD1-gdT cells, but not untransduced gdT cells, expressed markers of memory phenotype and secreted inflammatory cytokines. In vivo, chPD1-gdT cells, but not untransduced gdT cells, cleared PD-L1+ tumors without significant elevation of CRS-related cytokines nor off-tumor toxicities. Conclusions. chPD1-gdT cells are potent and safe in vitro and in vivo and will be assessed in a Phase I/II clinical trial.

Citation Format: Amorette Barber, Xiaohong Wang, Anupama Gopisetty, Leonardo Mirandola, Maurizio Chiriva-Internati. Gamma delta T cells engineered with a chimeric PD-1 receptor effectively control PD-L1 positive tumors in vitro and in vivo with minimal toxicities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB148.

T-cells expressing a chimeric-PD1-Dap10-CD3zeta receptor reduce tumour burden in multiple murine syngeneic models of solid cancer

Adoptive transfer of T-cells is a promising therapy for many cancers. To enhance tumour recognition by T-cells, chimeric antigen receptors (CARs) consisting of signalling domains fused to receptors that recognize tumour-associated antigens can be expressed in T-cells. While CAR T-cells have shown clinical success for treating haematopoietic malignancies, using CAR T-cells to treat solid tumours remains a challenge. We developed a chimeric PD1 (chPD1) receptor that recognizes the ligands for the PD1 receptor that are expressed on many types of solid cancer. To determine if this novel CAR could target a wide variety of tumour types, the anti-tumour efficacy of chPD1 T-cells against syngeneic murine models of melanoma, renal, pancreatic, liver, colon, breast, prostate and bladder cancer was measured. Of the 14 cell lines tested, all expressed PD1 ligands on their cell surface, making them potential targets for chPD1 T-cells. ChPD1 T-cells lysed the tumour cells and secreted pro-inflammatory cytokines [interferon (IFN)γ, tumour necrosis factor (TNF)α, interleukin (IL)-2, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-17 and IL-21], but did not secrete the anti-inflammatory cytokine IL-10. Furthermore, T-cells expressing chPD1 receptors reduced an established tumour burden and led to long-term tumour-free survival in all types of solid tumours tested. ChPD1 T-cells did not survive longer than 14 days in vivo; however, treatment with chPD1 T-cells induced protective host anti-tumour memory responses in tumour-bearing mice. Therefore, adoptive transfer of chPD1 T-cells could be a novel therapeutic strategy to treat multiple types of solid cancer.

Inclusion of Dap10 or 4-1BB costimulation domains in the chPD1 receptor enhances anti-tumor efficacy of T cells in murine models of lymphoma and melanoma

Chimeric antigen receptors (CAR) utilize costimulatory domains to enhance anti-tumor efficacy. However, it is unclear which costimulatory domain is preferable. Therefore, the intracellular domains of CD28, Dap10, 41BB, GITR, ICOS, or OX40 were compared in a murine chimeric PD1 (chPD1) receptor that targets tumor-associated PD1 ligands. Upon antigen restimulation, T cells expressing chPD1-CD28 receptors had reduced lytic capacity. While most of the chPD1 T cell receptors secreted pro-inflammatory (IFNγ, TNFα, IL-2, GM-CSF, IL-17, and IL-21) and anti-inflammatory cytokines (IL-10), chPD1-Dap10 did not secrete IL-10. Furthermore, chPD1-Dap10 and -41BB receptors induced a memory precursor phenotype, had enhanced persistence in vivo, and superior therapeutic efficacy in murine models of T cell lymphoma and melanoma compared to chPD1-CD28 or chPD1-GITR expressing T cells. Therefore, each costimulatory domain induces differential effects in CAR-expressing T cells and inclusion of Dap10 or 4-1BB costimulatory domains may induce a preferential cytokine profile and differentiation for cancer therapy.

Adoptive transfer of murine T cells expressing a chimeric-PD1-Dap10 receptor as an immunotherapy for lymphoma

Adoptive transfer of T cells is a promising cancer therapy and expression of chimeric antigen receptors can enhance tumour recognition and T-cell effector functions. The programmed death protein 1 (PD1) receptor is a prospective target for a chimeric antigen receptor because PD1 ligands are expressed on many cancer types, including lymphoma. Therefore, we developed a murine chimeric PD1 receptor (chPD1) consisting of the PD1 extracellular domain fused to the cytoplasmic domain of CD3ζ. Additionally, chimeric antigen receptor therapies use various co-stimulatory domains to enhance efficacy. Hence, the inclusion of a Dap10 or CD28 co-stimulatory domain in the chPD1 receptor was compared to determine which domain induced optimal anti-tumour immunity in a mouse model of lymphoma. The chPD1 T cells secreted pro-inflammatory cytokines and lysed RMA lymphoma cells. Adoptive transfer of chPD1 T cells significantly reduced established tumours and led to tumour-free survival in lymphoma-bearing mice. When comparing chPD1 receptors containing a Dap10 or CD28 domain, both receptors induced secretion of pro-inflammatory cytokines; however, chPD1-CD28 T cells also secreted anti-inflammatory cytokines whereas chPD1-Dap10 T cells did not. Additionally, chPD1-Dap10 induced a central memory T-cell phenotype compared with chPD1-CD28, which induced an effector memory phenotype. The chPD1-Dap10 T cells also had enhanced in vivo persistence and anti-tumour efficacy compared with chPD1-CD28 T cells. Therefore, adoptive transfer of chPD1 T cells could be a novel therapy for lymphoma and inclusion of the Dap10 co-stimulatory domain in chimeric antigen receptors may induce a preferential cytokine profile and T-cell differentiation phenotype for anti-tumour therapies.

Cardiotrophin-1 decreases intestinal sugar uptake in mice and in Caco-2 cells

AIM

Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT-1 treatment on intestinal sugar absorption in different experimental models.

METHODS

rCT-1 effects on α-Methyl-D-glucoside uptake were assessed in everted intestinal rings from wild-type and CT-1(-/-) mice and in Caco-2 cells. rCT-1 actions on SGLT-1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot.

RESULTS

In vivo administration (0.2 mg kg(-1) ) of rCT-1 caused a significant decrease on α-Methyl-D-glucoside uptake in everted intestinal rings from wild-type and CT-1(-/-) mice after short-term and long-term treatments. Similarly, in vitro treatment (1-50 ng mL(-1) ) with rCT-1 reduced α-Methyl-D-glucoside uptake in everted intestinal rings. In Caco-2 cells, rCT-1 treatment (20 ng mL(-1) , 1 and 24 h) lowered apical uptake of α-Methyl-D-glucoside in parallel with a decrease on SGLT-1 protein expression. rCT-1 promoted the phosphorylation of STAT-3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre-treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT-1 on α-Methyl-D-glucoside uptake. AICAR also prevented the inhibition of SGLT-1 observed in rCT-1-treated cells.

CONCLUSIONS

CT-1 inhibits intestinal sugar absorption by the reduction of SGLT-1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti-obesity properties of CT-1.

Abstract A05: NKG2D and CD28 receptors differentially activate mTOR to alter murine effector CD8+ T cell differentiation

Memory CD8+ T cells are an essential component of anti-tumor and anti-viral immunity. Activation of the mammalian/mechanistic target of rapamycin (mTOR) pathway has been implicated in regulating the differentiation of effector and memory T cells. However, the mechanisms that control mTOR activity during immunity to tumors and infections are not well known. Activation of costimulatory receptors, including CD28 and NKG2D, activate PI3K and subsequently may activate the mTOR pathway in CD8+ T cells. Therefore this study compared the activation of the mTOR signaling pathway after costimulation through CD28 or NKG2D receptors in murine effector CD8+ T cells. Compared to CD28 costimulation, activation through CD3 and NKG2D receptors had weaker activation of mTORc1 as shown by decreased phosphorylation of mTORc1 targets S6K1, ribosomal protein S6, and 4EBP-1. NKG2D costimulation also showed increased gene expression of TSC2, a negative regulator of mTORc1, whereas CD28 costimulation increased gene expression of Rheb, an activator of mTORc1, and HIF-1α and VEGFα, pro-angiogenic factors downstream of mTORc1. Strong mTORc1 activation in CD28-costimulated cells also increased expression of transcription factors that support effector cell differentiation, namely T-bet, and BLIMP1, whereas low levels of mTORc1 activation allowed for the expression of Eomes and BCL6 during NKG2D stimulation, and increased expression of central memory markers CD62L and CD127. These data show that compared to CD28, costimulation through the NKG2D receptor leads to the differential activation of the mTOR signaling pathway and potentially supports memory CD8+ T cell differentiation.

Citation Format: Bryan McQueen, Kelsey Trace, Emily Whitman, Amorette Barber. NKG2D and CD28 receptors differentially activate mTOR to alter murine effector CD8+ T cell differentiation. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr A05.

Natural killer group 2D and CD28 receptors differentially activate mammalian/mechanistic target of rapamycin to alter murine effector CD8+ T-cell differentiation

Memory CD8+ T cells are an essential component of anti-tumour and anti-viral immunity. Activation of the mammalian/mechanistic target of rapamycin (mTOR) pathway has been implicated in regulating the differentiation of effector and memory T cells. However, the mechanisms that control mTOR activity during immunity to tumours and infections are not well known. Activation of co-stimulatory receptors, including CD28 and natural killer group 2D (NKG2D), activate phosphatidylinositol-3 kinase and subsequently may activate the mTOR pathway in CD8+ T cells. This study compared the activation of the mTOR signalling pathway after co-stimulation through CD28 or NKG2D receptors in murine effector CD8+ T cells. Compared with CD28 co-stimulation, activation through CD3 and NKG2D receptors had weaker activation of mTORc1, as shown by decreased phosphorylation of mTORc1 targets S6K1, ribosomal protein S6 and eukaryotic initiation factor 4E binding protein 1. NKG2D co-stimulation also showed increased gene expression of tuberous sclerosis protein 2, a negative regulator of mTORc1, whereas CD28 co-stimulation increased gene expression of Ras homologue enriched in brain, an activator of mTORc1, and hypoxia-inducible factor-1α and vascular endothelial growth factor-α, pro-angiogenic factors downstream of mTORc1. Strong mTORc1 activation in CD28-co-stimulated cells also increased expression of transcription factors that support effector cell differentiation, namely T-bet, B lymphocyte-induced maturation protein (BLIMP-1), interferon regulatory factor 4, and inhibitor of DNA binding 2, whereas low levels of mTORc1 activation allowed for the expression of Eomes, B-cell lymphoma 6 (BCL6), and inhibitor of DNA binding 3 during NKG2D stimulation, and increased expression of memory markers CD62 ligand and CD127. These data show that compared with CD28, co-stimulation through the NKG2D receptor leads to the differential activation of the mTOR signalling pathway and potentially supports memory CD8+ T-cell differentiation.

Collaboration of chimeric antigen receptor (CAR)-expressing T cells and host T cells for optimal elimination of established ovarian tumors

Conditioning strategies that deplete host lymphocytes have been shown to enhance clinical responses to some adoptive T-cell therapies. However, host T cells are capable of eliminating tumor cells upon the relief of immunosuppression, indicating that lymphodepletion prior to T-cell transfer may reduce optimal tumor protection elicited by cell treatments that are capable of shaping host immunity. In this study, we show that adoptively transferred T cells bearing a chimeric antigen receptor (CAR) harness endogenous T cells for optimal tumor elimination and the development of a tumor-specific memory T cell response. Mice bearing ID8 ovarian cancer cells were treated with T cells transduced with a NKG2D-based CAR. CAR-expressing T cells increased the number of host CD4⁺ and CD8⁺ T cells at the tumor site in a CXCR3-dependent manner and increased the number of antigen-specific host CD4⁺ T cells in the tumor and draining lymph nodes. In addition, the administration of CAR-expressing T cells increased antigen presentation to CD4⁺ T cells, and this increase was dependent on interferon γ and granulocyte-macrophage colony-stimulating factor produced by the former. Host CD4⁺ T cells were sufficient for optimal tumor protection mediated by NKG2D CAR-expressing T cells, but they were not necessary if CD4⁺ T cells were adoptively co-transferred. However, host CD4⁺ T cells were essential for the development of an antigen-specific memory T-cell response to tumor cells. Moreover, optimal tumor elimination as orchestrated by NKG2D CAR-expressing T cells was dependent on host CD8⁺ T cells. These results demonstrate that adoptively transferred T cells recruit and activate endogenous T-cell immunity to enhance the elimination of tumor cells and the development of tumor-specific memory responses.

NKG2D receptor activation of NF-κB enhances inflammatory cytokine production in murine effector CD8(+) T cells

To induce strong immune responses, naïve CD8(+) T cells require stimulation through the TCR and costimulatory receptors. However, the biological effect of activating costimulatory receptors on effector T cells is still unclear. One costimulatory receptor that is likely to be engaged at the target site is NKG2D. This activating receptor is expressed on human and murine CD8(+) T cells with its ligands expressed on the majority of tumor cells and during some infections. In order to determine how activation of costimulatory receptors alters effector CD8(+) T cell functions, this study compared the activation of the NF-κB signaling pathway by two costimulatory receptors, CD28 and NKG2D. Compared to CD28 costimulation, activation of murine effector CD8(+) T cells through CD3 and NKG2D receptors enhanced activation of NF-κB as shown by increased phosphorylation of IKKα, IκBα, and NF-κB and IκBα degradation. NKG2D costimulation also increased activation, nuclear translocation, and DNA binding of NF-κB p65/p50 dimers. Activation of the NF-κB pathway also lead to increased gene expression and secretion of pro-inflammatory cytokines, including IFNα and IFNγ, and decreased gene expression and secretion of anti-inflammatory cytokines, including IL-10 and CCL2. Altered NF-κB activation also increased expression of the effector molecules TNFα, lymphotoxins α and β, and Fas ligand, and increased tumor cell killing through FasL. These data show that compared to CD28 costimulation, activation through the NKG2D receptor leads to the differential activation of the NF-κB signaling pathway and potentially enhances the anti-tumor and anti-viral functions of effector CD8(+) T cells.

NKG2D CAR T-cell therapy inhibits the growth of NKG2D ligand heterogeneous tumors

Tumor heterogeneity presents a substantial barrier to increasing clinical responses mediated by targeted therapies. Broadening the immune response elicited by treatments that target a single antigen is necessary for the elimination of tumor variants that fail to express the targeted antigen. In this study, it is shown that adoptive transfer of T cells bearing a chimeric antigen receptor (CAR) inhibited the growth of target-expressing and -deficient tumor cells within ovarian and lymphoma tumors. Mice bearing the ID8 ovarian or RMA lymphoma tumors were treated with T cells transduced with a NKG2D-based CAR (chNKG2D). NKG2D CAR T-cell therapy protected mice from heterogeneous RMA tumors. Moreover, adoptive transfer of chNKG2D T cells mediated tumor protection against highly heterogeneous ovarian tumors in which 50, 20 or only 7% of tumor cells expressed significant amounts of NKG2D ligands. CAR T cells did not mediate an in vivo response against tumor cells that did not express sufficient amounts of NKG2D ligands, and the number of ligand-expressing tumor cells correlated with therapeutic efficacy. In addition, tumor-free surviving mice were protected against a tumor re-challenge with NKG2D ligand-negative ovarian tumor cells. These data indicate that NKG2D CAR T-cell treatment can be an effective therapy against heterogeneous tumors and induce tumor-specific immunity against ligand-deficient tumor cells.

Chimeric antigen receptor T cells shape myeloid cell function within the tumor microenvironment through IFN-γ and GM-CSF

The infiltration of suppressive myeloid cells into the tumor microenvironment restrains anti-tumor immunity. However, cytokines may alter the function of myeloid lineage cells to support tumor rejection, regulating the balance between pro- and anti-tumor immunity. In this study, it is shown that effector cytokines secreted by adoptively transferred T cells expressing a chimeric Ag receptor (CAR) shape the function of myeloid cells to promote endogenous immunity and tumor destruction. Mice bearing the ovarian ID8 tumor were treated with T cells transduced with a chimeric NKG2D receptor. GM-CSF secreted by the adoptively transferred T cells recruited peripheral F4/80(lo)Ly-6C(+) myeloid cells to the tumor microenvironment in a CCR2-dependent fashion. T cell IFN-γ and GM-CSF activated local, tumor-associated macrophages, decreased expression of regulatory factors, increased IL-12p40 production, and augmented Ag processing and presentation by host macrophages to Ag-specific T cells. In addition, T cell-derived IFN-γ, but not GM-CSF, induced the production of NO by F4/80(hi) macrophages and enhanced their lysis of tumor cells. The ability of CAR T cell therapy to eliminate tumor was moderately impaired when inducible NO synthase was inhibited and greatly impaired in the absence of peritoneal macrophages after depletion with clodronate encapsulated liposomes. This study demonstrates that the activation of host macrophages by CAR T cell-derived cytokines transformed the tumor microenvironment from immunosuppressive to immunostimulatory and contributed to inhibition of ovarian tumor growth.

Chimeric antigen receptor (CAR) T cell cytokines shape myeloid cell function within the tumor microenvironment and activate host lymphocytes for tumor elimination. (165.4)

The infiltration of suppressive myeloid cells into the tumor microenvironment restrains anti-tumor immunity. However, T cell effector cytokines can shape the function of the myeloid lineage to support tumor rejection, regulating the balance between pro- and anti-tumor immunity. In this study, it is shown that effector cytokines secreted by adoptively transferred T cells expressing a chimeric antigen receptor (CAR) shape the function of myeloid cells to promote endogenous immunity and tumor destruction. C57BL/6 mice bearing the ID8 ovarian tumor were treated with effector T cells transduced to express a chimeric NKG2D receptor. GM-CSF produced by the adoptively transferred T cells recruited peripheral F4/80loLy-6C+ cells to the tumor site in a CCR2-dependent fashion. T cell IFN-γ and GM-CSF activated tumor-associated macrophages, increased IL-12p40 production, and augmented antigen presentation by host macrophages to antigen-specific host T cells. In addition, host F4/80+ cells secreted the chemokines CXCL9 and CXCL10 and host T cells were recruited to the tumor site in a CXCR3-dependent manner. Endogenous CD8+ T cells, but not CD4+ T cells, were required for complete tumor elimination. However, host CD4+ T cells were critical for the development of a tumor-specific memory T cell response. These studies show that host macrophages activated by CAR-bearing T cell-derived cytokines inhibited ovarian tumor growth by directly lysing tumor cells and promoting host T cell immunity.

Leptin regulates sugar and amino acids transport in the human intestinal cell line Caco-2

AIM

Studies in rodents have shown that leptin controls sugars and glutamine entry in the enterocytes by regulating membrane transporters. Here, we have examined the effect of leptin on sugar and amino acids absorption in the human model of intestinal cells Caco-2 and investigated the transporters involved.

METHODS

Substrate uptake experiments were performed in Caco-2 cells, grown on plates, in the presence and the absence of leptin, and the expression of the different transporters in brush border membrane vesicles was analysed by Western blot.

RESULTS

Leptin inhibited 0.1 mm α-methyl-D-glucoside uptake after 5 or 30 min treatment and decreased SGLT1 protein abundance in the apical membrane. Uptake of 20 μm glutamine and 0.1 mm phenylalanine was also inhibited by leptin, indicating sensitivity to the hormone of the Na(+) -dependent neutral amino acid transporters ASCT2 and B(0) AT1. This inhibition was accompanied by a reduction in the transporters expression at the brush border membrane. Leptin also inhibited 1 mm proline and β-alanine uptake in Na(+) medium at pH 6, conditions for optimal activity of the H(+) -dependent neutral amino acid transporter PAT1. In this case, abundance of PAT1 in the brush border membrane after leptin treatment was not modified. Interestingly, leptin inhibitory effect on β-alanine uptake was reversed by the PKA inhibitor H-89 suggesting involvement of PKA pathway in leptin's regulation of PAT1 activity.

CONCLUSION

These data show in human intestinal cells that leptin can rapidly control the activity of physiologically relevant transporters for rich-energy molecules, that is, D-glucose (SGLT1) and amino acids (ASCT2, B(0) AT1 and PAT1).

Treatment of multiple myeloma with adoptively transferred chimeric NKG2D receptor-expressing T cells

Multiple myeloma causes approximately 10% of all hematologic malignancies. We have previously shown that human T cells expressing chimeric NKG2D receptors (chNKG2D) consisting of NKG2D fused to the CD3ζ cytoplasmic domain secrete proinflammatory cytokines and kill human myeloma cells. In this study, we show chNKG2D T cells are effective in a murine model of multiple myeloma. Mice with established 5T33MM-green fluorescent protein tumors were treated with one or two infusions of chNKG2D T cells. Compared with mice treated with T cells expressing wild type (wt)NKG2D receptors, a single dose of chNKG2D T cells increased survival, with half of the chNKG2D T-cell-treated mice surviving long term. Two infusions of chNKG2D T cells led to tumor-free survival in all mice. ChNKG2D T cells were located at sites of tumor growth, including the bone marrow and spleen after intravenous injection. There was an increase in activated host T cells and NK cells at tumor sites and in serum interferon-γ after chNKG2D T-cell injection. Surviving mice were able to resist a rechallenge with 5T33MM cells but not RMA lymphoma cells, indicating that the mice developed a protective, specific memory response. These data demonstrate that chNKG2D T cells may be an effective adoptive cellular therapy for multiple myeloma.

Chimeric NKG2D expressing T cells eliminate immunosuppression and activate immunity within the ovarian tumor microenvironment

Adoptive transfer of T cells expressing chimeric NKG2D (chNKG2D) receptors, a fusion of NKG2D and CD3zeta, can lead to long-term, tumor-free survival in a murine model of ovarian cancer. To determine the mechanisms of chNKG2D T cell antitumor efficacy, we analyzed how chNKG2D T cells altered the tumor microenvironment, including the tumor-infiltrating leukocyte populations. chNKG2D T cell treatment of mice bearing ID8 tumor cells increased the number and activation of NK cells and increased the activation of host CD8+ T cells within the tumor. Foxp3+ regulatory T cells at the tumor site decreased more than 300-fold after chNKG2D T cell treatment. Tumor-associated regulatory T cells expressed cell surface NKG2D ligands and were killed by chNKG2D T cells in a perforin-dependent manner. chNKG2D T cells also altered the function of myeloid cells at the tumor site, changing these cells from being immunosuppressive to enhancing T cell responses. Cells isolated from the tumor produced elevated amounts of IFN-gamma, NO, and other proinflammatory cytokines after chNKG2D T cell treatment. ChNKG2D T cells required perforin, IFN-gamma, and GM-CSF to induce a full response at the tumor site. In addition, transfer of chNKG2D T cells into mice bearing tumors that were established for 5 weeks led to long-term survival of the mice. Thus, chNKG2D T cells altered the ovarian tumor microenvironment to eliminate immunosuppressive cells and induce infiltration and activation of antitumor immune cells and production of inflammatory cytokines. This induction of an immune response likely contributes to chNKG2D T cells' ability to eliminate established tumors.

Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity

The success of clinically relevant immunotherapies requires reversing tumor-induced immunosuppression. Here we demonstrated that linear polyethylenimine-based (PEI-based) nanoparticles encapsulating siRNA were preferentially and avidly engulfed by regulatory DCs expressing CD11c and programmed cell death 1-ligand 1 (PD-L1) at ovarian cancer locations in mice. PEI-siRNA uptake transformed these DCs from immunosuppressive cells to efficient antigen-presenting cells that activated tumor-reactive lymphocytes and exerted direct tumoricidal activity, both in vivo and in situ. PEI triggered robust and selective TLR5 activation in vitro and elicited the production of hallmark TLR5-inducible cytokines in WT mice, but not in Tlr5-/- littermates. Thus, PEI is a TLR5 agonist that, to our knowledge, was not previously recognized. In addition, PEI-complexed nontargeting siRNA oligonucleotides stimulated TLR3 and TLR7. The nonspecific activation of multiple TLRs (specifically, TLR5 and TLR7) reversed the tolerogenic phenotype of human and mouse ovarian tumor-associated DCs. In ovarian carcinoma-bearing mice, this induced T cell-mediated tumor regression and prolonged survival in a manner dependent upon myeloid differentiation primary response gene 88 (MyD88; i.e., independent of TLR3). Furthermore, gene-specific siRNA-PEI nanocomplexes that silenced immunosuppressive molecules on mouse tumor-associated DCs elicited discernibly superior antitumor immunity and enhanced therapeutic effects compared with nontargeting siRNA-PEI nanocomplexes. Our results demonstrate that the intrinsic TLR5 and TLR7 stimulation of siRNA-PEI nanoparticles synergizes with the gene-specific silencing activity of siRNA to transform tumor-infiltrating regulatory DCs into DCs capable of promoting therapeutic antitumor immunity.

Lipoic acid prevents body weight gain induced by a high fat diet in rats: effects on intestinal sugar transport

Several studies have suggested that oxidative stress might cause and aggravate the inflammatory state associated with obesity and could be the link between excessive weight gain and its related disorders such as insulin resistance and cardiovascular diseases. Thus, antioxidant treatment has been proposed as a therapy to prevent and manage obesity and associated complications. Therefore, the aim of the present study was to investigate the effects of supplementation of a standard or high fat diet with the antioxidant lipoic acid (LA) during 56 days, on body weight gain, adiposity, feed efficiency and intestinal sugar absorption, in male Wistar rats. LA supplementation induced a lower body weight gain and adipose tissue size in both control or high fat fed rats accompanied by a reduction in food intake. The group fed on a high fat diet and treated with LA (OLIP group) showed a lower body weight gain than its corresponding Pair-Fed (PF) group (P < 0.05), which received the same amount of food than LA-treated animals but with no LA. In fact, LA induced a reduction on feed efficiency and also significantly decreased intestinal alpha-methylglucoside (alpha-MG) absorption both in lean and obese rats. These results suggest that the beneficial effects of dietary supplementation with LA on body weight gain are mediated, at least in part, by the reduction observed in food intake and feed efficiency. Furthemore, the inhibitory action of LA on intestinal sugar transport could explain in part the lower feed efficiency observed in LA-treated animals and therefore, highlighting the beneficial effects of LA on obesity.

Chimeric NKG2D T cells require both T cell- and host-derived cytokine secretion and perforin expression to increase tumor antigen presentation and systemic immunity

Treatment of mice bearing established ovarian tumors with T cells expressing chimeric NKG2D receptors (chNKG2D) develop protective host immune responses to tumor Ags. In this study, the mechanisms that chNKG2D T cells require to induce host immunity against ovarian tumors and which of the host immune cells are involved in tumor elimination were determined. Treatment with chNKG2D T cells led to a sustained, increased IFN-gamma production by host NK, CD4(+), and CD8(+) T cells in the spleen and at the tumor site and this continued for many weeks after T cell injection. Tumor Ag presentation was enhanced in chNKG2D T cell-treated mice, and there were greater numbers of tumor-specific T cells at the tumor site and in draining lymph nodes after treatment with chNKG2D T cells. The increase in host cell cytokine secretion and Ag presentation was dependent on chNKG2D T cell-derived perforin, IFN-gamma, and GM-CSF. Host immune mechanisms were involved in tumor elimination because inhibition of tumor growth was limited in mice that lacked perforin, IFN-gamma, NK cells, or T and B cells (Rag1(-/-)). There was no role for host-derived GM-CSF or CD1-dependent NKT cells, because mice deficient in these were able to clear tumors as well as treated wild-type B6 mice. In summary, chNKG2D T cells required both cytotoxicity and cytokine secretion as well as the participation of host immune cells for development of a host antitumor immune response and complete efficacy.

Chimeric NKG2D receptor-expressing T cells as an immunotherapy for multiple myeloma

OBJECTIVE

Most myeloma tumor cells from patients express NKG2D ligands. We have reported the development of a chimeric NKG2D receptor (chNKG2D), which consists of the NKG2D receptor fused to the CD3zeta chain. T cells expressing this receptor kill and produce cytokines in response to NKG2D-ligand+ tumor cells. Therefore, we investigated whether human chNKG2D T cells respond against human myeloma cells.

MATERIALS AND METHODS

ChNKG2D T cells were generated from healthy donors and myeloma patients. The effector phase of chNKG2D T cells was analyzed by cell-surface marker expression and human myeloma cell lines were tested for expression of NKG2D ligands. Lysis of myeloma cell lines and cytokine secretion by chNKG2D T cells was determined. ChNKG2D T cells grown in serum-free media, or cyropreserved, were assessed for effector cell functions.

RESULTS

Myeloma cell lines expressed NKG2D ligands. ChNKG2D T cells from healthy donors and myeloma patients lysed myeloma cells, and secreted proinflammatory cytokines when cultured with myeloma cells or patient bone marrow, but not with peripheral blood mononuclear cells or normal bone marrow. Lysis of myeloma cells was dependent on chNKG2D T-cell expression of NKG2D and perforin. Additionally, chNKG2D T cells upregulated CD45RO, did not express CD57, and maintained expression of CD27, CD62L, and CCR7, indicating that the T cells were at an early effector stage. Finally, we showed that chNKG2D T cells generated with serum-free media, or when cryopreserved, maintained effector functions.

CONCLUSION

ChNKG2D T cells respond to human myeloma cells and can be generated using clinically applicable cell culture techniques.

Immunotherapy with chimeric NKG2D receptors leads to long-term tumor-free survival and development of host antitumor immunity in murine ovarian cancer

Ovarian cancer is one of the leading causes of cancer death in women and the development of novel therapies is needed to complement the standard treatment options such as chemotherapy and radiation. In this study, we show that treatment with T cells expressing a chimeric NKG2D receptor (chNKG2D) was able to lead to long-term, tumor-free survival in mice bearing established ovarian tumors. Tumor-free mice were able to reject a rechallenge with ovarian tumor cells 225 days after original tumor injection. In addition, chNKG2D T cell treatment induced specific host immune responses to ovarian tumor cells, including the development of both CD8+ and CD4+ T cell tumor-specific memory responses. The chNKG2D T cells reduced the ovarian tumor burden using both cytotoxic and cytokine-dependent pathways. Specifically, chNKG2D T cell expression of perforin, GM-CSF, and IFN-gamma were essential for complete antitumor efficacy.

Chimeric NKG2D modified T cells inhibit systemic T-cell lymphoma growth in a manner involving multiple cytokines and cytotoxic pathways

In this study, the efficacy and mechanisms of chimeric NKG2D receptor (chNKG2D)-modified T cells in eliminating NKG2D ligand-positive RMA/Rae1 lymphoma cells were evaluated. Intravenous injection of RMA/Rae1 cells led to significant tumor formation in spleens and lymph nodes within 2 weeks. Adoptive transfer of chNKG2D-modified T cells after tumor injection significantly reduced tumor burdens in both spleens and lymph nodes, and prolonged the survival of tumor-bearing mice. Multiple treatments with chNKG2D T cells resulted in long-term tumor-free survival. Moreover, these long-term survivors were resistant to rechallenge with RMA tumor cells (NKG2D ligand-negative), and their spleen and lymph node cells produced IFN-gamma in response to RMA but not to other tumors in vitro, indicating immunity against RMA tumor antigens. ChNKG2D T cell-derived IFN-gamma and granulocyte-macrophage colony-stimulating factor, but not perforin (Pfp), tumor necrosis factor-related apoptosis-inducing ligand, or Fas ligand (FasL) alone were critical for in vivo efficacy. T cells deficient in both Pfp and FasL did not kill NKG2D ligand-positive RMA cells in vitro. Adoptive transfer of Pfp(-/-)FasL(-/-) chNKG2D T cells had reduced in vivo efficacy, indicating that chNKG2D T cells used both mechanisms to attack RMA/Rae1 cells. Taken together, these results indicate that chNKG2D T-cell-mediated therapeutic effects are mediated by both cytokine-dependent and cytotoxic mechanisms in vivo.

Luminal leptin inhibits intestinal sugar absorption in vivo

AIM

We have previously demonstrated that leptin inhibits galactose absorption in rat intestinal everted rings and that leptin receptors are present in the apical membrane of the enterocytes. This adipocyte-derived hormone is also secreted by gastric mucosal cells and is able to reach the intestinal lumen. The goal of the present study was to prove whether luminal leptin acts on intestinal sugar absorption in vivo both at low (basal state) and high sugar concentration (post-prandial state).

METHODS

In vivo intestinal sugar absorption in rat was measured with recirculating and single-pass perfusion systems. Sugar disappearance in the perfusate was measured by radioactivity and biochemical methods. Luminal leptin effect on intestinal absorption mediated by sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2) as well as intestinal permeability (mannitol absorption) was determined.

RESULTS

Luminal leptin inhibited intestinal sugar absorption at low galactose concentrations, which indicates that leptin regulates SGLT1 activity in vivo. The inhibition was reversed in the absence of hormone in the intestinal lumen, suggesting that it was produced by post-translational regulation processes. At high luminal glucose concentrations, leptin also inhibited the phloretin-insensitive component of sugar absorption mediated by SGLT1. There was no significant effect on the apical GLUT2 component of absorption. Leptin did not modify in vivo intestinal permeability determined with (14)C-mannitol.

CONCLUSION

These observations support the view that gastric leptin exerts a regulatory role on intestinal sugar absorption in the postprandial state by modifying the active component of absorption.

Chimeric NKG2D Receptor–Bearing T Cells as Immunotherapy for Ovarian Cancer

Despite advancements in the treatment of ovarian cancer, this disease continues to be a leading cause of cancer death in women. Adoptive transfer of tumor-reactive T cells is a promising antitumor therapy for many cancers. We designed a chimeric receptor linking NKG2D, a natural killer (NK) cell-activating receptor, to the CD3zeta chain of the T-cell receptor to target ovarian tumor cells. Engagement of chimeric NKG2D receptors (chNKG2D) with ligands for NKG2D, which are commonly expressed on tumor cells, leads to T-cell secretion of proinflammatory cytokines and tumor cytotoxicity. In this study, we show that >80% of primary human ovarian cancer samples expressed ligands for NKG2D on the cell surface. The tumor samples expressed MHC class I-related protein A, MICB, and UL-16 binding proteins 1 and 3. ChNKG2D-expressing T cells lysed ovarian cancer cell lines. We show that T cells from ovarian cancer patients that express chNKG2D secreted proinflammatory cytokines when cultured with autologous tumor cells. In addition, we show that chNKG2D T cells can be used therapeutically in a murine model of ovarian cancer. These data indicate that treatment with chNKG2D-expressing T cells is a potential immunotherapy for ovarian cancer.

Generation of antitumor responses by genetic modification of primary human T cells with a chimeric NKG2D receptor

To create more effective T cells against human tumors, we have designed a strategy to allow T cells to recognize tumor cells using natural killer (NK) cell receptors but retain the effector responses of T lymphocytes. NKG2D is an activating cell surface receptor expressed on NK cells and on some T-cell subsets. Its ligands are primarily expressed on tumor cells. We have shown that by linking mouse NKG2D to the CD3zeta chain, it was possible to generate a chimeric NKG2D (chNKG2D) receptor that allowed activation of murine T cells on engagement with NKG2D ligand-positive tumor cells leading to antitumor responses in mice. In this study, a human version of the chNKG2D receptor was expressed on primary human T cells, and antitumor responses were determined. Human peripheral blood mononuclear cell-derived T cells were retrovirally transduced with a human chNKG2D receptor gene. These chNKG2D-bearing human T cells responded to NKG2D ligand-positive tumor cells by producing T-helper 1 cytokines, proinflammatory chemokines, and significant cellular cytotoxicity. This response could be blocked by anti-NKG2D antibodies, and it was dependent on NKG2D ligand expression on the target cells but not on expression of MHC molecules. In addition, the activity of chNKG2D-bearing T cells remained unimpaired after exposure to a soluble NKG2D ligand, soluble MICA, at concentrations as high as 1.5 mug/mL. These data indicate the feasibility of using chNKG2D receptors in primary human T cells and suggest that this approach may be a promising means for cancer immunotherapy.

Na+ and pH dependence of proline and beta-alanine absorption in rat small intestine

AIMS

Early characterization of intestinal absorption of imino acids in mammals has demonstrated the existence of a Na+-dependent, Cl- -independent transport system in rat small intestine, which is the only carrier for beta-alanine. Based on the substrate selectivity, it was proposed that the Proton Amino Acid Transporter 1 (PAT1) could be the same as this imino acid carrier. The present study characterizes the pH and Na+ dependence of proline and beta-alanine uptake in rat small intestine.

METHODS

Intestinal uptake of radiolabelled l-proline or beta-alanine was measured in brush border membrane vesicles and everted intestinal rings, in the presence and absence of Na+ and at different pH values.

RESULTS

The existence of an inwardly directed H+ gradient in the absence of Na+ enhanced the initial entry of proline and beta-alanine in brush border membrane vesicles, that reached a transient overshoot with maximal value around 30 s. In the absence of pH gradient, no overshoot was shown. In entire tissue, there was an increase of proline and beta-alanine uptake at acidic pH that was higher in the presence of Na+ than in its absence. This ion dependence and pH effect of the amino acids uptake also increased with the incubation period. Substrate inhibition studies confirmed that intestinal proline absorption in rat occurs mainly by system B and PAT1-like transporter.

CONCLUSIONS

There is a Na+ -independent, H+ -dependent transporter of amino acids at the apical membrane of the rat enterocytes.

Human NK cell IFN-gamma production is regulated by endogenous TGF-beta

NK cells are an important component of innate immunity, and they can promote CTL and Th1 cell development and macrophage activation via cytokines. TGF-beta is believed to be an important immunoregulatory molecule, and for this reason several TGF-beta inhibitors are currently in clinical development. However, the modulation of specific innate immune responses by endogenous human TGF-beta remains unclear. In this study, we demonstrate that blocking the action of endogenous TGF-beta resulted in an increase in both the percentage of responding NK cells and the amount of IFN-gamma produced by human NK cells when stimulated by monokines and TLR agonists. Blocking endogenous TGF-beta resulted in significant NK cell IFN-gamma production under suboptimal stimulation conditions. Our findings also suggest that TGF-beta associated with other blood cells may be involved in limiting NK cell activation. Thus, inhibiting endogenous TGF-beta provides a means to shift NK cell activation and promote cellular immunity.