Preclinical In Vitro and In Vivo Models for Adoptive Cell Therapy of Cancer.

ABSTRACT: Adoptive cellular therapies are making major strides in the treatment of cancer, both for hematologic and solid tumors. These cellular products include chimeric antigen receptor T cells and T-cell receptor-modified T cells, tumor-infiltrating lymphocytes, marrow-infiltrating T cells, natural killer cells as well as macrophage-based therapeutics. Advancement in genomics, computational biology, immunology, and cell therapy manufacturing has facilitated advancement of adoptive T cell therapies into the clinic, whereas clinical efficacy has driven Food and Drug Administration approvals. The growth of adoptive cellular therapy has, in turn, led to innovation in the preclinical models available, from ex vivo cell-based models to in vivo xenograft models of treatment. This review focuses on the development and application of in vitro models and in vivo models (cell line xenograft, humanized mice, and patient-derived xenograft models) that directly evaluate these human cellular products.

Functional Genomic Identification of Predictors of Sensitivity and Mechanisms of Resistance to Multivalent Second-Generation TRAIL-R2 Agonists.

Multivalent second-generation TRAIL-R2 agonists are currently in late preclinical development and early clinical trials. Herein, we use a representative second-generation agent, MEDI3039, to address two major clinical challenges facing these agents: lack of predictive biomarkers to enable patient selection and emergence of resistance. Genome-wide CRISPR knockout screens were notable for the lack of resistance mechanisms beyond the canonical TRAIL-R2 pathway (caspase-8, FADD, BID) as well as p53 and BAX in TP53 wild-type models, whereas a CRISPR activatory screen identified cell death inhibitors MCL-1 and BCL-XL as mechanisms to suppress MEDI3039-induced cell death. High-throughput drug screening failed to identify genomic alterations associated with response to MEDI3039; however, transcriptomics analysis revealed striking association between MEDI3039 sensitivity and expression of core components of the extrinsic apoptotic pathway, most notably its main apoptotic effector caspase-8 in solid tumor cell lines. Further analyses of colorectal cell lines and patient-derived xenografts identified caspase-8 expression ratio to its endogenous regulator FLIP(L) as predictive of sensitivity to MEDI3039 in several major solid tumor types and a further subset indicated by caspase-8:MCL-1 ratio. Subsequent MEDI3039 combination screening of TRAIL-R2, caspase-8, FADD, and BID knockout models with 60 compounds with varying mechanisms of action identified two inhibitor of apoptosis proteins (IAP) that exhibited strong synergy with MEDI3039 that could reverse resistance only in BID-deleted models. In summary, we identify the ratios of caspase-8:FLIP(L) and caspase-8:MCL-1 as potential predictive biomarkers for second-generation TRAIL-R2 agonists and loss of key effectors such as FADD and caspase-8 as likely drivers of clinical resistance in solid tumors.

Establishment of Humanized Mice from Peripheral Blood Mononuclear Cells or Cord Blood CD34+ Hematopoietic Stem Cells for Immune-Oncology Studies Evaluating New Therapeutic Agents.

The clinical success of immune checkpoint modulators and the development of next-generation immune-oncology (IO) agents underscore the need for robust preclinical models to evaluate novel IO therapeutics. Human immune system (HIS) mouse models enable in vivo studies in the context of the HIS via a human tumor. The immunodeficient mouse strains NOG (Prkdcscid Il2rgtm1Sug ) and triple-transgenic NOG-EXL [Prkdcscid Il2rgtm1Sug Tg (SV40/HTLV-IL3, CSF2)], which expresses human IL-3 and GM-CSF, allow for human CD34+ hematopoietic stem cell (huCD34+ HSC) engraftment and multilineage immune cell development by 12 to 16 weeks post-transplant and facilitate studies of immunomodulatory agents. A more rapid model of human immune engraftment utilizes peripheral blood mononuclear cells (PBMCs) transplanted into immunodeficient murine hosts, permitting T-cell engraftment within 2 to 3 weeks without outgrowth of other human immune cells. The PBMC-HIS model can be limited due to onset of xenogeneic graft-versus-host disease (xGVHD) within 3 to 5 weeks post-implantation. Host deficiency in MHC class I, as occurs in beta-2 microglobulin knockout in either NOG or NSG mice, results in resistance to xGVHD, which permits a longer therapeutic window. In this article, detailed processes for generating humanized mice by transplantation of HSCs from cord blood-derived huCD34+ HSCs or PBMCs into immunodeficient mouse strains to respectively generate HSC-HIS and PBMC-HIS mouse models are provided. In addition, the co-engraftment and growth kinetics of patient-derived and cell line-derived xenograft tumors in humanized mice and recovery of tumor-infiltrating lymphocytes from growing tumors to evaluate immune cell subsets by flow cytometry are described. © 2020 The Authors. Basic Protocol 1: Establishment of patient-derived xenograft tumors in CD34+ hematopoietic stem cell-humanized mice Basic Protocol 2: Establishment of patient-derived xenograft tumors in peripheral blood mononuclear cell-humanized mice Support Protocol 1: Flow cytometry assessment of humanization in mice Support Protocol 2: Flow cytometry assessment of tumor-infiltrating lymphocytes in tumor-bearing humanized mouse models.

Circulating Type-1 Anti-Tumor CD4(+) T Cells are Preferentially Pro-Apoptotic in Cancer Patients.

Cancer patients frequently exhibit a deficiency in Type-1 (but not Type-2 or regulatory) CD4(+) T cell responses against tumor-associated antigens (TAA), which may limit protection against disease progression or responsiveness to immunotherapy in these individuals. Since such deficiency was acutely evident in patients with active disease (AD), where chronic stimulation of anti-tumor CD4(+) T cells would be expected and activation-induced cell death may be prevalent, we employed MHC Class II-peptide tetramers to characterize the frequency and apoptotic status of TAA- vs. influenza (FluM1) virus-specific CD4(+) T cells in the peripheral blood of HLA-DR*0401(+) patients with melanoma or renal cell carcinoma. We observed that Flu-specific CD4(+) T cells ranged from 0.17 to 3.89%, while up to approximately 1% of CD4(+) T cells reacted against individual TAA epitopes derived from the EphA2 or MAGE-6 proteins. The frequencies of EphA2 and MAGE-6-specific CD4(+) T cells in patients were significantly correlated with AD and gender of the patient (i.e., females > males), while frequencies of Flu-specific CD4(+) T cells were distributed within a normal range in all patients. Notably, patient CD4(+) T cells reactive with MHC class II-TAA (but not MHC class II-Flu) tetramers were significantly enriched for a pro-apoptotic (Annexin-V(+)) phenotype, particularly amongst the Th1 (T-bet(+)) subset. These results suggest that the preferential sensitivity of TAA (but not viral)-specific CD4(+) Th1 cells to apoptosis in melanoma patients with AD will need to be overcome for optimal clinical benefit of immunotherapeutic approaches to be realized.

A novel probe for the non-invasive detection of tumor-associated inflammation.

A novel dual-mode contrast agent was formulated through the addition of an optical near infrared (NIR) probe to a perfluorocarbon (PFC)-based 19F magnetic resonance imaging (MRI) agent, which labels inflammatory cells in situ. A single PFC-NIR imaging agent enables both a qualitative, rapid optical monitoring of an inflammatory state and a quantitative, detailed and tissue-depth independent magnetic resonance imaging (MRI). The feasibility of in vivo optical imaging of the inflammatory response was demonstrated in a subcutaneous murine breast carcinoma model. Ex vivo optical imaging was used to quantify the PFC-NIR signal in the tumor and organs, and results correlated well with quantitative 19F NMR analyses of intact tissues. 19F MRI was employed to construct a three-dimensional image of the cellular microenvironment at the tumor site. Flow cytometry of isolated tumor cells was used to identify the cellular localization of the PFC-NIR probe within the tumor microenvironment. Contrast is achieved through the labeling of host cells involved in the immune response, but not tumor cells. The major cellular reservoir of the imaging agent were tumor-infiltrating CD11b+ F4/80low Gr-1low cells, a cell subset sharing immunophenotypic features with myeloid-derived suppressor cells (MDSCs). These cells are recruited to sites of inflammation and are implicated in immune evasion and tumor progression. This PFC-NIR contrast agent coupled to non-invasive, quantitative imaging techniques could serve as a valuable tool for evaluating novel anticancer agents.

¹9F MRI tracer preserves in vitro and in vivo properties of hematopoietic stem cells.

Hematopoietic stem cells (HSCs) have numerous therapeutic applications including immune reconstitution, enzyme replacement, regenerative medicine, and immunomodulation. The trafficking and persistence of these cells after administration is a fundamental question for future therapeutic applications of HSCs. Here, we describe the safe and efficacious labeling of human CD34(+) HSCs with a novel, self-delivering perfluorocarbon ¹9F magnetic resonance imaging (MRI) tracer, which has recently been authorized for use in a clinical trial to track therapeutic cells. While various imaging contrast agents have been used to track cellular therapeutics, the impact of this MRI tracer on HSC function has not previously been studied. Both human CD34(+) and murine bone marrow (BM) HSCs were effectively labeled with the MRI tracer, with only a slight reduction in viability, relative to mock-labeled cells. In a pilot study, ¹9F MRI enabled the rapid evaluation of HSC delivery/retention following administration into a rat thigh muscle, revealing the dispersal of HSCs after injection, but not after surgical implantation. To investigate effects on cell functionality, labeled and unlabeled human HSCs were tested in in vitro colony forming unit (CFU) assays, which resulted in equal numbers of total CFU as well as individual CFU types, indicating that labeling did not alter multipotency. Cobblestone assay forming cell precursor frequency was also unaffected, providing additional evidence that stem cell function was preserved after labeling. In vivo tests of multipotency and reconstitution studies in mice with murine BM containing labeled HSCs resulted in normal development of CFU in the spleen, compared to unlabeled cells, and reconstitution of both lymphoid and myeloid compartments. The lack of interference in these complex biological processes provides strong evidence that the function and therapeutic potential of the HSCs are likely maintained after labeling. These data support the safety and efficacy of the MRI tracer for clinical tracking of human stem cells.

Visualizing arthritic inflammation and therapeutic response by fluorine-19 magnetic resonance imaging (19F MRI).

BACKGROUND: Non-invasive imaging of inflammation to measure the progression of autoimmune diseases, such as rheumatoid arthritis (RA), and to monitor responses to therapy is critically needed. V-Sense, a perfluorocarbon (PFC) contrast agent that preferentially labels inflammatory cells, which are then recruited out of systemic circulation to sites of inflammation, enables detection by 19F MRI. With no 19F background in the host, detection is highly-specific and can act as a proxy biomarker of the degree of inflammation present. METHODS: Collagen-induced arthritis in rats, a model with many similarities to human RA, was used to study the ability of the PFC contrast agent to reveal the accumulation of inflammation over time using 19F MRI. Disease progression in the rat hind limbs was monitored by caliper measurements and 19F MRI on days 15, 22 and 29, including the height of clinically symptomatic disease. Naïve rats served as controls. The capacity of the PFC contrast agent and 19F MRI to assess the effectiveness of therapy was studied in a cohort of rats administered oral prednisolone on days 14 to 28. RESULTS: Quantification of 19F signal measured by MRI in affected limbs was linearly correlated with disease severity. In animals with progressive disease, increases in 19F signal reflected the ongoing recruitment of inflammatory cells to the site, while no increase in 19F signal was observed in animals receiving treatment which resulted in clinical resolution of disease. CONCLUSION: These results indicate that 19F MRI may be used to quantitatively and qualitatively evaluate longitudinal responses to a therapeutic regimen, while additionally revealing the recruitment of monocytic cells involved in the inflammatory process to the anatomical site. This study may support the use of 19F MRI to clinically quantify and monitor the severity of inflammation, and to assess the effectiveness of treatments in RA and other diseases with an inflammatory component.

Intralesional delivery of dendritic cells engineered to express T-bet promotes protective type 1 immunity and the normalization of the tumor microenvironment.

T-bet (Tbx21), a T-box transcription factor, has been previously identified as a master regulator of type 1 T cell polarization. We have also recently shown that the genetic engineering of human dendritic cells (DCs) to express human T-bet cDNA yields type 1-polarizing APCs in vitro (1). In the present study, murine CD11c(+) DCs were transduced with a recombinant adenovirus encoding full-length murine T-bets (DC.mTbets) and analyzed for their immunomodulatory functions in vitro and in vivo. Within the range of markers analyzed, DC.mTbets exhibited a control DC phenotype and were indistinguishable from control DCs in their ability to promote allogenic T cell proliferation in MLR in vitro. However, DC.mTbets were superior to control DCs in promoting Th1 and Tc1 responses in vitro via a mechanism requiring DC-T cell interaction or the close proximity of these two cell types and that can only partially be explained by the action of DC-elaborated IL-12p70. When injected into day 7 s.c. CMS4 sarcoma lesions growing in syngenic BALB/c mice, DC.mTbets dramatically slowed tumor progression (versus control DCs) and extended overall survival via a mechanism dependent on both CD4(+) and CD8(+) T cells and, to a lesser extent, asialoGM1(+) NK cells. DC.mTbet-based therapy also promoted superior tumor-specific Tc1 responses in the spleens and tumor-draining lymph nodes of treated animals, and within the tumor microenvironment it inhibited the accumulation of CD11b(+)Gr1(+) myeloid-derived suppressor cells and normalized CD31(+) vascular structures. These findings support the potential translational utility of DC.Tbets as a therapeutic modality in the cancer setting.

DC expressing transgene Foxp3 are regulatory APC.

Tolerogenic DC and suppressive Foxp3(+) Treg play important roles in preventing autoimmunity and allograft rejection. We report that (adenovirus mediated) ectopic expression of Foxp3 in human DC (i.e. DC.Foxp3) yields an APC that severely limits T-cell proliferation and type-1 immune responses from the naïve, but not memory, pool of responder T cells in vitro. In marked contrast, the frequencies of type-2 and Treg responses were dramatically increased after stimulation of naïve T cells with DC.Foxp3 versus control DC. DC.Foxp3-induced CD4(+)CD25(+) Treg cells potently suppressed the proliferation of, and IFN-gamma production from, CD4(+) and CD8(+) responder T cells. Notably, the immunosuppressive biology of DC.Foxp3 was effectively normalized by addition of 1-methyl-tryptophan or neutralizing anti-TGF-beta1 Ab during the period of T-cell priming. These data suggest the potential utility of regulatory DC.Foxp3 and/or DC.Foxp3-induced CD4(+)CD25(+) Treg as translational agents for the amelioration or prevention of pathology in the setting of allograft transplantation and/or autoimmunity.

Ectopic T-bet expression licenses dendritic cells for IL-12-independent priming of type 1 T cells in vitro.

T-bet (TBX21) is a transcription factor required for the optimal development of type 1 immune responses. Although initially characterized for its intrinsic role in T cell functional polarization, endogenous T-bet may also be critical to the licensing of type 1-biasing APCs. Here, we investigated whether human dendritic cells (DC) genetically engineered to express high levels of T-bet (i.e., DC.Tbet) promote superior type 1 T cell responses in vitro. We observed that DC.Tbet were selective activators of type 1 effector T cells developed from the naive pool of responder cells, whereas DC.Tbet and control DC promoted type 1 responses equitably from the memory pool of responder cells. Naive T cells primed by (staphylococcal enterotoxin B or tumor-associated protein-loaded) DC.Tbet exhibited an enhancement in type 1- and a concomitant reduction in Th2- and regulatory T cell-associated phenotype/function. Surprisingly, DC.Tbets were impaired in their production of IL-12 family member cytokines (IL-12p70, IL-23, and IL-27) when compared with control DC, and the capacity of DC.Tbet to preferentially prime type 1 T cell responses was only minimally inhibited by cytokine (IL-12p70, IL-23, IFN-gamma) neutralization or receptor (IL-12Rbeta2, IL-27R) blockade during T cell priming. The results of transwell assays suggested the DC.Tbet-mediated effects are predominantly the result of direct DC-T cell contact or their close proximity, thereby implicating a novel, IL-12-independent mechanism by which DC.Tbets promote improved type 1 functional polarization from naive T cell responders. Given their superior type 1 polarizing capacity, DC.Tbet may be suitable for use in vaccines designed to prevent/treat cancer or infectious disease.

Heat shock protein 90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin enhances EphA2+ tumor cell recognition by specific CD8+ T cells.

EphA2, a member of the receptor tyrosine kinase family, is commonly expressed by a broad range of cancer types, where its level of (over)expression correlates with poor clinical outcome. Because tumor cell expressed EphA2 is a nonmutated "self" protein, specific CD8(+) T cells are subject to self-tolerance mechanisms and typically exhibit only moderate-to-low functional avidity, rendering them marginally competent to recognize EphA2(+) tumor cells in vitro or in vivo. We have recently reported that the ability of specific CD8(+) T cells to recognize EphA2(+) tumor cells can be augmented after the cancer cells are pretreated with EphA2 agonists that promote proteasomal degradation and up-regulated expression of EphA2/class I complexes on the tumor cell membrane. In the current study, we show that treatment of EphA2(+) tumor cells with the irreversible heat shock protein 90 inhibitor, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), similarly enhances their recognition by EphA2-specific CD8(+) T-cell lines and clones in vitro via a mechanism that is dependent on proteasome and transporter-associated protein function as well as the retrotranslocation of EphA2 into the tumor cytoplasm. When 17-DMAG and agonist anti-EphA2 monoclonal antibodies are coapplied, T-cell recognition of tumor cells is further increased over that observed for either agent alone. These studies suggest that EphA2 represents a novel heat shock protein 90 client protein and that the treatment of cancer patients with 17-DMAG-based "pulse" therapy may improve the antitumor efficacy of CD8(+) T effector cells reactive against EphA2-derived epitopes.

Integrating costimulatory agonists to optimize immune-based cancer therapies.

While immunotherapy for cancer has become increasingly popular, clinical benefits for such approaches remain limited. This is likely due to tumor-associated immune suppression, particularly in the advanced-disease setting. Thus, a major goal of novel immunotherapeutic design has become the coordinate reversal of existing immune dysfunction and promotion of specific tumoricidal T-cell function. Costimulatory members of the TNF-receptor family are important regulators of T-cell-mediated immunity. Notably, agonist ligation of these receptors restores potent antitumor immunity in the tumor-bearing host. Current Phase I/II evaluation of TNF-receptor agonists as single-modality therapies will illuminate their safety, mechanism(s) of action, and best use in prospective combinational immunotherapy approaches capable of yielding superior benefits to cancer patients.

Enhancement in specific CD8+ T cell recognition of EphA2+ tumors in vitro and in vivo after treatment with ligand agonists.

The EphA2 receptor tyrosine kinase is an attractive therapeutic target that is commonly overexpressed on solid tumors, with the degree of overexpression associated with disease progression, metastatic potential, and poor prognosis. Agonistic mAbs or ligand (ephrinA1)-Fc fusion protein are capable of inducing EphA2 internalization and degradation, thereby (at least transiently) eliminating the influence of this oncoprotein. We and others have also shown that EphA2 contains multiple peptide epitopes that can be recognized by effector CD4(+) and CD8(+) T cells isolated from tumor-bearing patients. Herein, we show that "agonist" reagents that trigger the proteasome-dependent degradation of tumor cell EphA2 result in the improved presentation of peptides derived from (both the extracellular and intracellular domains of) EphA2 in MHC class I complexes expressed on the tumor cell membrane for at least 48 h, as manifested by increased recognition by EphA2-specific CD8(+) T cells in vitro. We also observed that while delivery of ephrinA1-Fc fusion protein or agonist mAb into EphA2(+) tumor lesions promotes EphA2 degradation in situ, this single administration of agent does not dramatically alter tumor progression in a humanized SCID model. However, when combined with the adoptive transfer of normally nontherapeutic (human) anti-EphA2 CD8(+) CTL, this dual-agent regimen results in complete tumor eradication. These results suggest that strategies targeting the conditional proteasome-mediated destruction of tumor cell EphA2 may enable EphA2-specific CD8(+) T cells (of modest functional avidity) to realize improved therapeutic potential.

CD8+ T-cell responses against hemoglobin-beta prevent solid tumor growth.

Bone marrow-derived dendritic cells engineered using recombinant adenovirus to secrete high levels of IL-12p70 dramatically inhibited the growth of established CMS4 sarcomas in BALB/c mice after intratumoral administration. An analysis of splenic CD8(+) T cells in regressor mice revealed a strong, complex reactivity pattern against high-performance liquid chromatography (HPLC)-resolved peptides isolated by acid elution from single-cell suspensions of surgically resected CMS4 lesions. Mass spectrometry analyses defined two major overlapping peptide species that derive from the murine hemoglobin-beta (HBB) protein within the most stimulatory HPLC fractions. Although cultured CMS4 tumor cells failed to express HBB mRNA based on reverse transcription-PCR analyses, prophylactic vaccination of BALB/c mice with vaccines containing HBB peptides promoted specific CD8(+) T-cell responses that protected mice against a subsequent challenge with CMS4 or unrelated syngeneic (HBB(neg)) tumors of divergent histology (sarcoma, carcinomas of the breast or colon). In situ imaging suggested that vaccines limit or destabilize tumor-associated vascular structures, potentially by promoting immunity against HBB+ vascular pericytes. Importantly, there were no untoward effects of vaccination with the HBB peptide on peripheral RBC numbers, RBC hemoglobin content, or vascular structures in the brain or eye.

Interferon-alpha (IFN-alpha)-conditioned DC preferentially stimulate type-1 and limit Treg-type in vitro T-cell responses from RCC patients.

Dendritic cells (DCs) are potent antigen presenting cells and represent attractive candidates for use in novel immunotherapies for patients with renal cell carcinoma (RCC), a disease that has proven refractory to conventional treatment modalities, such as chemotherapy and radiotherapy. Given the perceived need to augment antitumor type-1 immunity (TC1 and Th1) as a therapeutic end point, and the known functional plasticity of DC populations that may display heterogeneous capacity to promote T-cell responses, we sought to identify a preferred DC preparation with this capacity. We compared 2 different preparations of monocyte-derived DC using interferon-alpha (IFN-alpha) (IFN-DC and alphaDC1) with classic DCs "matured" (mDCs) using interleukin-1beta/interleukin-6/tumor necrosis factor-alpha/prostaglandin E2, for their ability to promote autologous TC1 antitumor responses from RCC patients in vitro. IFN-alpha-conditioned DC promoted significantly higher numbers of RCC-specific CD8+ T cells exhibiting a cytotoxic phenotype after in vitro stimulation (IVS) than cytokine cocktail-mDCs. Furthermore, IVS using IFN-DCs was able to diminish regulatory-type T cells among CD4+ T-cell responder populations versus IVS using conventional mDC-based vaccines. These data emphasize an important role for IFN-alpha in modulating the immunologic functions of DCs toward a polarized DC1-type capable of coordinately promoting TH1-type and TC1-type T-cell mediated immunity and supports the translational development of patient-derived IFN-alpha-conditioned DC for use in novel immunotherapies for patients with RCC, and in whom, endogenous tumor-specific TC1 effector cells may be dysfunctional, anergic, or prone to undergo apoptosis.

Interleukin-12: biological properties and clinical application.

Interleukin-12 (IL-12) is a heterodimeric protein, first recovered from EBV-transformed B cell lines. It is a multifunctional cytokine, the properties of which bridge innate and adaptive immunity, acting as a key regulator of cell-mediated immune responses through the induction of T helper 1 differentiation. By promoting IFN-gamma production, proliferation, and cytolytic activity of natural killer and T cells, IL-12 induces cellular immunity. In addition, IL-12 induces an antiangiogenic program mediated by IFN-gamma-inducible genes and by lymphocyte-endothelial cell cross-talk. The immunomodulating and antiangiogenic functions of IL-12 have provided the rationale for exploiting this cytokine as an anticancer agent. In contrast with the significant antitumor and antimetastatic activity of IL-12, documented in several preclinical studies, clinical trials with IL-12, used as a single agent, or as a vaccine adjuvant, have shown limited efficacy in most instances. More effective application of this cytokine, and of newly identified IL-12 family members (IL-23 and IL-27), should be evaluated as therapeutic agents with considerable potential in cancer patients.

Preferential expression of very late antigen-4 on type 1 CTL cells plays a critical role in trafficking into central nervous system tumors.

We have previously shown preferential tumor-homing and therapeutic efficacy of adoptively transferred type 1 CTL (Tc1) when compared with type 2 CTL (Tc2) in mice bearing intracranial ovalbumin-transfected melanoma (M05). Further characterizing the expression of a panel of homing receptors on Tc1 and Tc2 cells, we found that very late antigen (VLA)-4 (a heterodimer of CD49d and CD29), but none of other receptors evaluated, was expressed at significantly higher levels on Tc1 cells than on Tc2 cells. Although CD49d (alpha(4) integrin) can form heterodimers with both beta(1) (CD29) and beta(7) integrins, alpha(4)beta(7) complexes were not expressed by either Tc1 or Tc2 cells, suggesting that CD49d is solely expressed in VLA-4 complexes. VLA-4 expression on Tc2 cells was down-regulated in an interleukin (IL)-4 dose-dependent manner but not by other type 2 cytokines, such as IL-10 and IL-13, suggesting that IL-4 uniquely down-regulates VLA-4 expression on these cells. In accordance with the differential expression of VLA-4 on Tc1 versus Tc2 cells, Tc1 cells alone were competent to adhere to plate-bound VCAM-1-Ig fusion protein. Finally, the efficient trafficking of Tc1 cells into intracranial M05 lesions in vivo was efficiently blocked by administration of monoclonal antibodies against CD49d or VCAM-1 or small interfering RNA-mediated silencing of CD49d on Tc1 cells. Collectively, these data support the critical role of VLA-4 in the effective intracranial tumor homing of adoptive-transferred, antigen-specific Tc1 cells and suggest that more effective vaccine and/or ex vivo T-cell activation regimens may be developed by promoting the generation of VLA-4(+) antitumor Tc1 cells.

Polarized type-1 dendritic cells (DC1) producing high levels of IL-12 family members rescue patient TH1-type antimelanoma CD4+ T cell responses in vitro.

Deficiencies in TH1-type immunity in patients with cancer may facilitate tumor progression and limit the effectiveness of current immunotherapy approaches. We hypothesized that Type-1 polarized dendritic cells (DC1) might be able to recondition patient antitumor CD4+ T cell responses toward the TH1-type in vitro. Although DC1 have been previously demonstrated to prime TH1 responses from naive CD4+ T cells, their impact on antigen-experienced TH responses remains unknown. We confirmed our own earlier observations that patient CD4+ T cell reactivity against melanoma-associated antigens (MAA) was weaker and less Type-1-polarized than their corresponding antiviral responses. Stimulation of patient CD4 T cells with peptide-pulsed DC1 (producing multiple IL-12 family member cytokines, including IL-12p70, IL-23, and IL-27) promoted robust TH1-type, epitope-specific T cell responses. Addition of exogenous IL-12 family member cytokines alone, or in combination, to nonpolarized DC was insufficient to equate to the benefits associated with DC1-based stimulation; however, IL-27 and IL-12p70 blockade neutralized the ability of DC1 cells to enhance TH1-type antitumor immunity in vitro. Notably, DC1-based stimulation seemed capable of "revitalizing" defective TH1-type responses within the CD45RO+ subset of antigen-experienced CD4+ T cells in melanoma patients. In addition to promoting elevated levels of IFN-gamma from responder CD4+ T cells, DC1-based stimulation also led to increased levels of IL-12Rbeta2 and t-bet expression by TH cells. These results suggest that preexisting CD4+ T cell immunity to cancer is not relegated to Type-1 insufficiency and may be corrected via the application of DC1-based vaccination protocols.

Improving immunotherapy by conditionally enhancing MHC class I presentation of tumor antigen-derived Peptide epitopes.

Tumors represent an altered self cell type that can be recognized by both the host humoral (B cells, antibodies) and cellular (T cells) adaptive immune systems. Because most known tumor-associated antigens (TAA) recognized by T cells represent overexpressed or aberrantly expressed proteins, which are not mutated and to which tolerance has been developed, the anti-TAA T-cell repertoire available to the cancer patient is of moderate-to-low avidity. Specific vaccinations typically amplify the absolute number of such T cells, but may have little consequence on improving their functional avidity, which may fall below a critical threshold required for effective recognition of tumor cells in situ. This review will discuss methods to improve low-avidity T-cell recognition of cancer cells by manipulating the tumor cells themselves to conditionally express higher levels of TAA-derived peptide epitopes presented in major histocompatibility (MHC) complexes. This may facilitate the design and performance of novel combinational therapies for the effective treatment of a broad range of cancer types.

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) gamma] 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-gamma 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-gamma-producing type 1 effector cells. This represents a relevant mechanism by which renal cell carcinoma can inhibit protective antitumor immunity.