Clinically relevant orthotopic pancreatic cancer models for adoptive T cell transfer therapy.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive tumor. Prognosis is poor and survival is low in patients diagnosed with this disease, with a survival rate of ~12% at 5 years. Immunotherapy, including adoptive T cell transfer therapy, has not impacted the outcomes in patients with PDAC, due in part to the hostile tumor microenvironment (TME) which limits T cell trafficking and persistence. We posit that murine models serve as useful tools to study the fate of T cell therapy. Currently, genetically engineered mouse models (GEMMs) for PDAC are considered a "gold-standard" as they recapitulate many aspects of human disease. However, these models have limitations, including marked tumor variability across individual mice and the cost of colony maintenance. METHODS: Using flow cytometry and immunohistochemistry, we characterized the immunological features and trafficking patterns of adoptively transferred T cells in orthotopic PDAC (C57BL/6) models using two mouse cell lines, KPC-Luc and MT-5, isolated from C57BL/6 KPC-GEMM (KrasLSL-G12D/+p53-/- and KrasLSL-G12D/+p53LSL-R172H/+, respectively). RESULTS: The MT-5 orthotopic model best recapitulates the cellular and stromal features of the TME in the PDAC GEMM. In contrast, far more host immune cells infiltrate the KPC-Luc tumors, which have less stroma, although CD4+ and CD8+ T cells were similarly detected in the MT-5 tumors compared with KPC-GEMM in mice. Interestingly, we found that chimeric antigen receptor (CAR) T cells redirected to recognize mesothelin on these tumors that signal via CD3ζ and 41BB (Meso-41BBζ-CAR T cells) infiltrated the tumors of mice bearing stroma-devoid KPC-Luc orthotopic tumors, but not MT-5 tumors. CONCLUSIONS: Our data establish for the first time a reproducible and realistic clinical system useful for modeling stroma-rich and stroma-devoid PDAC tumors. These models shall serve an indepth study of how to overcome barriers that limit antitumor activity of adoptively transferred T cells.

Progressively Enhancing Stemness of Adoptively Transferred T Cells with PI3Kδ Blockade Improves Metabolism and Antitumor Immunity.

Generating stem-like memory T cells (TSCM) is a potential strategy to improve adoptive immunotherapy. Elucidating optimal ways to modulate signaling pathways that enrich TSCM properties could identify approaches to achieve this goal. We discovered herein that blocking the PI3Kδ pathway pharmaceutically to varying degrees can generate T cells with increasingly heightened stemness properties, based on the progressive enrichment of the transcription factors Tcf1 and Lef1. T cells with enhanced stemness features exhibited metabolic plasticity, marked by improved mitochondrial function and glucose uptake after tumor recognition. Conversely, T cells with low or medium stemness were less metabolically dynamic, vulnerable to antigen-induced cell death, and expressed more inhibitory checkpoint receptors. Only T-cell receptor-specific or chimeric antigen receptor (CAR)-specific T cells with high stemness persisted in vivo and mounted protective immunity to tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor-infiltrating lymphocytes and CAR T cells with elevated stemness properties, in turn bolstering their capacity to regress human solid tumors. The stemness level of T cells in vitro was important, ultimately impacting their efficacy in mice bearing three distinct solid tumors. Lef1 and Tcf1 sustained antitumor protection by donor high CD8+ TSCM or CD4+ Th17SCM, as deletion of either one compromised the therapeutic efficacy. Collectively, these findings highlight the importance of strategic modulation of PI3Kδ signaling in T cells to induce stemness and lasting protective responses to solid tumors. SIGNIFICANCE: Elevating T-cell stemness by progressively blocking PI3Kδ signaling during ex vivo manufacturing of adoptive cell therapies alters metabolic and functional properties to enhance antitumor immunity dependent on Tcf1 and Lef1.

FcγRIIB expressed on CD8+ T cells limits responsiveness to PD-1 checkpoint inhibition in cancer.

Checkpoint inhibition using Fc-containing monoclonal antibodies has emerged as a powerful therapeutic approach to augment antitumor immunity. We recently showed that FcγRIIB, the only inhibitory IgG-Fc receptor, is expressed on a population of highly differentiated effector CD8+ T cells in the tumors of mice and humans, raising the possibility that CD8+ T cell responses may be directly modulated by checkpoint inhibitor binding to T cell-expressed FcγRIIB. Here, we show that despite exhibiting strong proliferative and cytokine responses at baseline, human FcγRIIBpos CD8+ T cells exhibited reduced responsiveness to both PD-1 and CTLA-4 checkpoint inhibition as compared with FcγRIIBneg CD8+ T cells in vitro. Moreover, frequencies of FcγRIIBpos CD8+ T cells were reduced after treatment of patients with melanoma with nivolumab in vivo. This reduced responsiveness was FcγRIIB dependent, because conditional genetic deletion of FcγRIIB on tumor-specific CD8+ T cells improved response to checkpoint blockade in B16 and LLC mouse models of cancer. The limited responsiveness of FcγRIIBpos CD8+ T cells was also dependent on an intact Fc region of the checkpoint inhibitor, in that treatment with Fc-devoid anti-PD-1 F(ab) fragments resulted in increased proliferation of FcγRIIBpos CD8+ T cells, without altering the response of FcγRIIBneg CD8+ T cells. Last, the addition of FcγRIIB blockade improved efficacy of PD-1 checkpoint inhibition in mouse models of melanoma, lung, and colon cancer. These results illuminate an FcγRIIB-mediated, cell-autonomous mechanism of CD8+ T cell suppression, which limits the efficacy of checkpoint inhibitors during antitumor immune responses in vivo.

Augmenting TCR signal strength and ICOS costimulation results in metabolically fit and therapeutically potent human CAR Th17 cells.

IL-17-producing antigen-specific human T cells elicit potent antitumor activity in mice. Yet, refinement of this approach is needed to position it for clinical use. While activation signal strength regulates IL-17 production by CD4+ T cells, the degree to which T cell antigen receptor (TCR) and costimulation signal strength influences Th17 immunity remains unknown. We discovered that decreasing TCR/costimulation signal strength by incremental reduction of αCD3/costimulation beads progressively altered Th17 phenotype. Moreover, Th17 cells stimulated with αCD3/inducible costimulator (ICOS) beads produced more IL-17A, IFNγ, IL-2, and IL-22 than those stimulated with αCD3/CD28 beads. Compared with Th17 cells stimulated with the standard, strong signal strength (three beads per T cell), Th17 cells propagated with 30-fold fewer αCD3/ICOS beads were less reliant on glucose and favored the central carbon pathway for bioenergetics, marked by abundant intracellular phosphoenolpyruvate (PEP). Importantly, Th17 cells stimulated with weak αCD3/ICOS beads and redirected with a chimeric antigen receptor that recognizes mesothelin were more effective at clearing human mesothelioma. Less effective CAR Th17 cells generated with high αCD3/ICOS beads were rescued by overexpressing phosphoenolpyruvate carboxykinase 1 (PCK1), a PEP regulator. Thus, Th17 therapy can be improved by using fewer activation beads during manufacturing, a finding that is cost effective and directly translatable to patients.

The degree of T cell stemness differentially impacts the potency of adoptive cancer immunotherapy in a Lef-1 and Tcf-1 dependent manner.

Generating stem memory T cells (T SCM ) is a key goal for improving cancer immunotherapy. Yet, the optimal way to modulate signaling pathways that enrich T SCM properties remains elusive. Here, we discovered that the degree to which the PI3Kδ pathway is blocked pharmaceutically can generate T cells with differential levels of stemness properties. This observation was based on the progressive enrichment of transcriptional factors of stemness (Tcf-1 and Lef-1). Additional investigation revealed that T cells with high stemness features had enhanced metabolic plasticity, marked by heightened mitochondrial function and glucose uptake. Conversely, T cells with low or medium features of stemness expressed more inhibitory checkpoint receptors (Tim-3, CD39) and were vulnerable to antigen-induced cell death. Only TCR-antigen specific T cells with high stemness persisted following adoptive transfer in vivo and mounted protective immunity to melanoma tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor infiltrating lymphocytes (TILs) and CAR T cells with heightened stemness properties, in turn bolstering their capacity to regress human mesothelioma tumors. We find that the level of stemness T cells possess in vitro differentially impacts their potency upon transfer in three tumor models. Mechanistically, both Lef-1 and Tcf-1 sustain anti-tumor protection by high T SCM , as deletion of either one compromised cellular therapy. Collectively, these findings highlight the therapeutic potential of carefully modulating PI3Kδ signaling in T cells to confer high stemness and mediate protective responses to solid tumors.

Distinct host preconditioning regimens differentially impact the antitumor potency of adoptively transferred Th17 cells.

Background: Mechanisms by which distinct methods of host preconditioning impact the efficacy of adoptively transferred antitumor T helper cells is unknown. Methods: CD4 + T cells with a transgenic TCR that recognize TRP-1 melanoma antigen were polarized to the T helper 17 (Th17) phenotype and then transferred into melanoma-bearing mice preconditioned with either total body irradiation or chemotherapy. Results: We found that preconditioning mice with a non-myeloablative dose of total body irradiation (TBI of 5 Gy) was more effective than using an equivalently dosed non-myeloablative chemotherapy (CTX at 200 mg/kg) at augmenting therapeutic activity of anti-tumor TRP-1 Th17 cells. Anti-tumor Th17 cells engrafted better following preconditioning with TBI and regressed large established melanoma in all animals. Conversely, only half of mice survived long-term when preconditioned with CTX and infused with anti-melanoma Th17 cells. IL-17 and IFN-g produced by the infused Th17 cells, were detected in animals given either TBI or CTX preconditioning. Interestingly, inflammatory cytokines (G-CSF, IL-6, MCP-1, IL-5, and KC) were significantly elevated in the serum of mice preconditioned with TBI versus CTX after Th17 therapy. Conclusions: Our results indicate, for the first time, that the antitumor response, persistence, and cytokine profiles resulting from Th17 therapy are impacted by the specific regimen of host preconditioning. This work is important for understanding mechanisms that promote long-lived responses by ACT, particularly as CD4 + based T cell therapies are now emerging in the clinic.

B cells imprint adoptively transferred CD8+ T cells with enhanced tumor immunity.

BACKGROUND: Adoptive T cell transfer (ACT) therapy improves outcomes in patients with advanced malignancies, yet many individuals relapse due to the infusion of T cells with poor function or persistence. Toll-like receptor (TLR) agonists can invigorate antitumor T cell responses when administered directly to patients, but these responses often coincide with toxicities. We posited that TLR agonists could be repurposed ex vivo to condition T cells with remarkable potency in vivo, circumventing TLR-related toxicity. METHODS: In this study we investigated how tumor-specific murine CD8+ T cells and human tumor infiltrating lymphocytes (TILs) are impacted when expanded ex vivo with the TLR9 agonist CpG. RESULTS: Herein we reveal a new way to reverse the tolerant state of adoptively transferred CD8+ T cells against tumors using TLR-activated B cells. We repurposed the TLR9 agonist, CpG, commonly used in the clinic, to bolster T cell-B cell interactions during expansion for ACT. T cells expanded ex vivo from a CpG-treated culture demonstrated potent antitumor efficacy and prolonged persistence in vivo. This antitumor efficacy was accomplished without in vivo administration of TLR agonists or other adjuvants of high-dose interleukin (IL)-2 or vaccination, which are classically required for effective ACT therapy. CpG-conditioned CD8+ T cells acquired a unique proteomic signature hallmarked by an IL-2RαhighICOShighCD39low phenotype and an altered metabolic profile, all reliant on B cells transiently present in the culture. Likewise, human TILs benefitted from expansion with CpG ex vivo, as they also possessed the IL-2RαhighICOShighCD39low phenotype. CpG fostered the expansion of potent CD8+ T cells with the signature phenotype and antitumor ability via empowering a direct B-T cell interaction. Isolated B cells also imparted T cells with the CpG-associated phenotype and improved tumor immunity without the aid of additional antigen-presenting cells or other immune cells in the culture. CONCLUSIONS: Our results demonstrate a novel way to use TLR agonists to improve immunotherapy and reveal a vital role for B cells in the generation of potent CD8+ T cell-based therapies. Our findings have immediate implications in the clinical treatment of advanced solid tumors.

Neoadjuvant presurgical PD-1 inhibition in oral cavity squamous cell carcinoma.

Oral cavity squamous cell carcinoma (OCSCC) is a prevalent surgically treated subset of head and neck cancer with frequent recurrence and poor survival. Immunotherapy has demonstrated efficacy in recurrent/metastatic head and neck cancer. However, whether antitumor responses could be fostered by neoadjuvant presurgical immunotherapy remains unclear. Using a Simon's two-stage design, we present results of a single-arm phase-II trial where 12 patients with stage II-IVA OCSCC received 3 to 4 biweekly doses of 3 mg/kg nivolumab followed by definitive surgical resection with curative intent. Presurgical nivolumab therapy in this cohort shows an overall response rate of 33% (n = 4 patients; 95% CI: 12%-53%). With a median follow up of 2.23 years, 10 out of 12 treated patients remain alive. Neoadjuvant nivolumab is safe, well-tolerated, and is not associated with delays in definitive surgical treatment in this study. This work demonstrates feasibility and safety for incorporation of nivolumab in the neoadjuvant setting for OCSCC (ClinicalTrials.gov: NCT03021993).

Modeling ex vivo tumor-infiltrating lymphocyte expansion from established solid malignancies.

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) elicits the regression of metastatic malignancies, yet a low proportion of patients achieve complete durable responses. The high incidence of relapse in these patients highlights the need to better understand mechanisms of tumor escape from T cell control. While melanoma has provided the foundation for developing TIL therapy, much less is known about TIL efficacy and relapse in other malignancies. We sought to investigate TIL characteristics in mouse tumors which have not been studied in this setting. Here, we expanded murine TIL ex vivo in IL-2 from fragments of multiple tumor models, including oral cavity cancer models of varying immunogenicity. Additionally, TIL was expanded from pmel-1 mice bearing B16F10 melanoma, yielding an enriched population of tumor-infiltrating TCR transgenic T cells. Murine TIL are similar to human TIL in that they express high levels of inhibitory receptors (PD-1, Tim-3, etc.) and can be expanded ex vivo in IL-2 extensively. Of clinical relevance, we draw parallels between murine and human oral cavity cancer TIL, evaluating relationships between inhibitory receptor expression and function. This platform can be used by labs even in the absence of clinical specimens or clean cell facilities and will be important to more broadly understand TIL phenotypes across many different malignancies.

Fundamentals of T Cell Metabolism and Strategies to Enhance Cancer Immunotherapy.

Emerging reports show that metabolic pathways can be targeted to enhance T cell-mediated immunity to tumors. Yet, tumors consume key metabolites in the host to survive, thus robbing T cells of these nutrients to function and thrive. T cells are often deprived of basic building blocks for energy in the tumor, including glucose and amino acids needed to proliferate or produce cytotoxic molecules against tumors. Immunosuppressive molecules in the host further compromise the lytic capacity of T cells. Moreover, checkpoint receptors inhibit T cell responses by impairing their bioenergetic potential within tumors. In this review, we discuss the fundamental metabolic pathways involved in T cell activation, differentiation and response against tumors. We then address ways to target metabolic pathways to improve the next generation of immunotherapies for cancer patients.

Identification of human CD4+ T cell populations with distinct antitumor activity.

How naturally arising human CD4+ T helper subsets affect cancer immunotherapy is unclear. We reported that human CD4+CD26high T cells elicit potent immunity against solid tumors. As CD26high T cells are often categorized as TH17 cells for their IL-17 production and high CD26 expression, we posited these populations would have similar molecular properties. Here, we reveal that CD26high T cells are epigenetically and transcriptionally distinct from TH17 cells. Of clinical importance, CD26high and TH17 cells engineered with a chimeric antigen receptor (CAR) regressed large human tumors to a greater extent than enriched TH1 or TH2 cells. Only human CD26high T cells mediated curative responses, even when redirected with a suboptimal CAR and without aid by CD8+ CAR T cells. CD26high T cells cosecreted effector cytokines, produced cytotoxic molecules, and persisted long term. Collectively, our work underscores the promise of CD4+ T cell populations to improve durability of solid tumor therapies.

IL6 Fuels Durable Memory for Th17 Cell-Mediated Responses to Tumors.

The accessibility of adoptive T-cell transfer therapies (ACT) is hindered by the cost and time required for product development. Here we describe a streamlined ACT protocol using Th17 cells expanded only 4 days ex vivo. While shortening expansion compromised cell yield, this method licensed Th17 cells to eradicate large tumors to a greater extent than cells expanded longer term. Day 4 Th17 cells engrafted, induced release of multiple cytokines including IL6, IL17, MCP-1, and GM-CSF in the tumor-bearing host, and persisted as memory cells. IL6 was a critical component for efficacy of these therapies via its promotion of long-term immunity and resistance to tumor relapse. Mechanistically, IL6 diminished engraftment of FoxP3+ donor T cells, corresponding with robust tumor infiltration by donor effector over regulatory cells for the Day 4 Th17 cell product relative to cell products expanded longer durations ex vivo. Collectively, this work describes a method to rapidly generate therapeutic T-cell products for ACT and implicates IL6 in promoting durable immunity of Th17 cells against large, established solid tumors. SIGNIFICANCE: An abbreviated, 4-day ex vivo expansion method licenses Th17 cells to confer long-lived immunity against solid malignancies via induction of systemic IL6 in the host.See related commentary by Fiering and Ho, p. 3795.

Ex vivo blockade of PI3K gamma or delta signaling enhances the antitumor potency of adoptively transferred CD8+ T cells.

Adoptive T cell transfer therapy induces objective responses in patients with advanced malignancies. Despite these results, some individuals do not respond due to the generation of terminally differentiated T cells during the expansion protocol. As the gamma and delta catalytic subunits in the PI3K pathway are abundant in leukocytes and involved in cell activation, we posited that blocking both subunits ex vivo with the inhibitor IPI-145 would prevent their differentiation, thereby increasing antitumor activity in vivo. However, IPI-145 treatment generated a product with reduced antitumor activity. Instead, T cells inhibited of PI3Kγ (IPI-549) or PI3Kδ (CAL-101 or TGR-1202) alone were more potent in vivo. While T cells coinhibited of PI3Kγ and PI3Kδ were less differentiated, they were functionally impaired, indicated by reduced production of effector cytokines after antigenic re-encounter and decreased persistence in vivo. Human CAR T cells expanded with either a PI3Kγ or PI3Kδ inhibitor possessed a central memory phenotype compared to vehicle cohorts. We also found that PI3Kδ-inhibited CARs lysed human tumors in vitro more effectively than PI3Kγ-expanded or traditionally expanded CAR T cells. Our data imply that sole blockade of PI3Kγ or PI3Kδ generates T cells with remarkable antitumor properties, a discovery that has substantial clinical implications.

Fueling Cancer Immunotherapy With Common Gamma Chain Cytokines.

Adoptive T cell transfer therapy (ACT) using tumor infiltrating lymphocytes or lymphocytes redirected with antigen receptors (CAR or TCR) has revolutionized the field of cancer immunotherapy. Although CAR T cell therapy mediates robust responses in patients with hematological malignancies, this approach has been less effective for treating patients with solid tumors. Additionally, toxicities post T cell infusion highlight the need for safer ACT protocols. Current protocols traditionally expand T lymphocytes isolated from patient tumors or from peripheral blood to large magnitudes in the presence of high dose IL-2 prior to infusion. Unfortunately, this expansion protocol differentiates T cells to a full effector or terminal phenotype in vitro, consequently reducing their long-term survival and antitumor effectiveness in vivo. Post-infusion, T cells face further obstacles limiting their persistence and function within the suppressive tumor microenvironment. Therapeutic manipulation of T cells with common γ chain cytokines, which are critical growth factors for T cells, may be the key to bypass such immunological hurdles. Herein, we discuss the primary functions of the common γ chain cytokines impacting T cell survival and memory and then elaborate on how these distinct cytokines have been used to augment T cell-based cancer immunotherapy.

CAR T Cells in Solid Tumors: Blueprints for Building Effective Therapies.

Genetic redirection of T lymphocytes with chimeric antigen receptors (CARs) has soared from treating cancers preclinically to FDA approval for hematologic malignancies and commercial-grade production scale in under 30 years. To date, solid tumors are less susceptible to CAR therapies and instead have been treated more successfully with immune checkpoint blockade or tumor-infiltrating lymphocyte therapy. Here, we discuss the current challenges in treating solid tumors with CAR T cells, and the obstacles within the host and tumor microenvironment hindering their efficacy. We present a novel three-pronged approach for enhancing the efficacy of CAR T cells whereby a single infusion product can synergize the power of an optimal CAR construct, a highly potent T cell subset, and rejuvenate the endogenous immune response to conquer therapeutically-resistant solid tumors.

In Vitro Priming of Adoptively Transferred T Cells with a RORγ Agonist Confers Durable Memory and Stemness In Vivo.

Adoptive T-cell transfer therapy is an FDA- approved treatment for leukemia that relies on the ex vivo expansion and reinfusion of a patient's immune cells, which can be engineered with a chimeric antigen receptor (CAR) for more efficient tumor recognition. Type 17 T cells, controlled transcriptionally by RORγ, have been reported to mediate potent antitumor effects superior to those observed with conventionally expanded T cells. Here, we demonstrate that addition of a synthetic, small-molecule RORγ agonist during ex vivo expansion potentiates the antitumor activity of human Th17 and Tc17 cells redirected with a CAR. Likewise, ex vivo use of this agonist bolstered the antitumor properties of murine tumor-specific CD4+ and CD8+ T cells. Expansion in the presence of the RORγ agonist enhanced IL17A production without compromising IFNγ secretion in vitroIn vivo, cytokine neutralization studies revealed that IFNγ and IL17A were required to regress murine melanoma tumors. The enhanced antitumor effect of RORγ agonist treatment was associated with recovery of more donor T cells in the tumor and spleen; these cells produced elevated levels of cytokines months after infusion and expressed markers of long-lived stem and central memory cells such as Tcf7 and CD62L. Conversely, untreated cells mainly exhibited effector phenotypes in the tumor. Cured mice previously treated with agonist-primed T cells were protected from tumor rechallenge. Collectively, our work reveals that in vitro treatment with a RORγ agonist generates potent antitumor Type 17 effector cells that persist as long-lived memory cells in vivoSignificance: RORγ agonists can be used in vitro during T-cell expansion to enhance the efficacy of adoptive cell therapy (e.g., CAR-T) and to provide long-term protection against tumors.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/14/3888/F1.large.jpg Cancer Res; 78(14); 3888-98. ©2018 AACR.

N-acetyl cysteine protects anti-melanoma cytotoxic T cells from exhaustion induced by rapid expansion via the downmodulation of Foxo1 in an Akt-dependent manner.

Therapeutic outcomes for adoptive cell transfer (ACT) therapy are constrained by the quality of the infused T cells. The rapid expansion necessary to obtain large numbers of cells results in a more terminally differentiated phenotype with decreased durability and functionality. N-acetyl cysteine (NAC) protects against activation-induced cell death (AICD) and improves anti-tumor efficacy of Pmel-1 T cells in vivo. Here, we show that these benefits of NAC can be extended to engineered T cells and significantly increases T-cell survival within the tumor microenvironment. The addition of NAC to the expansion protocol of human TIL13838I TCR-transduced T cells that are under evaluation in a Phase I clinical trial, demonstrated that findings in murine cells extend to human cells. Expansion of TIL13838I TCR-transduced T cells in NAC also increased their ability to kill target cells in vitro. Interestingly, NAC did not affect memory subsets, but diminished up-regulation of senescence (CD57) and exhaustion (PD-1) markers and significantly decreased expression of the transcription factors EOMES and Foxo1. Pharmacological inhibition of the PI3K/Akt pathway ablates the decrease in Foxo1 induced by NAC treatment of activated T cells. This suggests a model in which NAC through PI3K/Akt activation suppresses Foxo1 expression, thereby impacting its transcriptional targets EOMES, PD-1, and granzyme B. Taken together, our results indicate that NAC exerts pleiotropic effects that impact the quality of TCR-transduced T cells and suggest that the addition of NAC to current clinical protocols should be considered.

Human CD26high T cells elicit tumor immunity against multiple malignancies via enhanced migration and persistence.

CD8+ T lymphocytes mediate potent immune responses against tumor, but the role of human CD4+ T cell subsets in cancer immunotherapy remains ill-defined. Herein, we exhibit that CD26 identifies three T helper subsets with distinct immunological properties in both healthy individuals and cancer patients. Although CD26neg T cells possess a regulatory phenotype, CD26int T cells are mainly naive and CD26high T cells appear terminally differentiated and exhausted. Paradoxically, CD26high T cells persist in and regress multiple solid tumors following adoptive cell transfer. Further analysis revealed that CD26high cells have a rich chemokine receptor profile (including CCR2 and CCR5), profound cytotoxicity (Granzyme B and CD107A), resistance to apoptosis (c-KIT and Bcl2), and enhanced stemness (ß-catenin and Lef1). These properties license CD26high T cells with a natural capacity to traffic to, regress and survive in solid tumors. Collectively, these findings identify CD4+ T cell subsets with properties critical for improving cancer immunotherapy.

PI3Kδ Inhibition Enhances the Antitumor Fitness of Adoptively Transferred CD8+ T Cells.

Phosphatidylinositol-3-kinase p110δ (PI3Kδ) inhibition by Idelalisib (CAL-101) in hematological malignancies directly induces apoptosis in cancer cells and disrupts immunological tolerance by depleting regulatory T cells. Yet, little is known about the direct impact of PI3Kδ blockade on effector T cells from CAL-101 therapy. Herein, we demonstrate a direct effect of p110δ inactivation via CAL-101 on murine and human CD8+ T cells that promotes a strong undifferentiated phenotype (elevated CD62L/CCR7, CD127, and Tcf7). These CAL-101 T cells also persisted longer after transfer into tumor bearing mice in both the murine syngeneic and human xenograft mouse models. The less differentiated phenotype and improved engraftment of CAL-101 T cells resulted in stronger antitumor immunity compared to traditionally expanded CD8+ T cells in both tumor models. Thus, this report describes a novel direct enhancement of CD8+ T cells by a p110δ inhibitor that leads to markedly improved tumor regression. This finding has significant implications to improve outcomes from next generation cancer immunotherapies.

The Basics of Artificial Antigen Presenting Cells in T Cell-Based Cancer Immunotherapies.

Adoptive T cell transfer (ACT) can mediate objective responses in patients with advanced malignancies. There have been major advances in this field, including the optimization of the ex vivo generation of tumor-reactive lymphocytes to ample numbers for effective ACT therapy via the use of natural and artificial antigen presenting cells (APCs). Herein we review the basic properties of APCs and how they have been manufactured through the years to augment vaccine and T cell-based cancer therapies. We then discuss how these novel APCs impact the function and memory properties of T cells. Finally, we propose new ways to synthesize aAPCs to augment the therapeutic effectiveness of antitumor T cells for ACT therapy.