CD90 is not constitutively expressed in functional innate lymphoid cells

Huge progress has been made in understanding the biology of innate lymphoid cells (ILC) by adopting several well-known concepts in T cell biology. As such, flow cytometry gating strategies and markers, such as CD90, have been applied to indentify ILC. Here, we report that most non-NK intestinal ILC have a high expression of CD90 as expected, but surprisingly a sub-population of cells exhibit low or even no expression of this marker. CD90-negative and CD90-low CD127⁺ ILC were present amongst all ILC subsets in the gut. The frequency of CD90-negative and CD90-low CD127⁺ ILC was dependent on stimulatory cues in vitro and enhanced by dysbiosis in vivo. CD90-negative and CD90-low CD127⁺ ILC were a potential source of IL-13, IFNγ and IL-17A at steady state and upon dysbiosis- and dextran sulphate sodium-elicited colitis. Hence, this study reveals that, contrary to expectations, CD90 is not constitutively expressed by functional ILC in the gut.

Organoids capture tissue-specific innate lymphoid cell development in mice and humans

Organoid-based models of murine and human innate lymphoid cell precursor (ILCP) maturation are presented. First, murine intestinal and pulmonary organoids are harnessed to demonstrate that the epithelial niche is sufficient to drive tissue-specific maturation of all innate lymphoid cell (ILC) groups in parallel, without requiring subset-specific cytokine supplementation. Then, more complex human induced pluripotent stem cell (hiPSC)-based gut and lung organoid models are used to demonstrate that human epithelial cells recapitulate maturation of ILC from a stringent systemic human ILCP population, but only when the organoid-associated stromal cells are depleted. These systems offer versatile and reductionist models to dissect the impact of environmental and mucosal niche cues on ILC maturation. In the future, these could provide insight into how ILC activity and development might become dysregulated in chronic inflammatory diseases.

TGF-β1 potentiates Vγ9Vδ2 T cell adoptive immunotherapy of cancer

Despite its role in cancer surveillance, adoptive immunotherapy using γδ T cells has achieved limited efficacy. To enhance trafficking to bone marrow, circulating Vγ9Vδ2 T cells are expanded in serum-free medium containing TGF-β1 and IL-2 (γδ[T2] cells) or medium containing IL-2 alone (γδ[2] cells, as the control). Unexpectedly, the yield and viability of γδ[T2] cells are also increased by TGF-β1, when compared to γδ[2] controls. γδ[T2] cells are less differentiated and yet display increased cytolytic activity, cytokine release, and antitumor activity in several leukemic and solid tumor models. Efficacy is further enhanced by cancer cell sensitization using aminobisphosphonates or Ara-C. A number of contributory effects of TGF-β are described, including prostaglandin E2 receptor downmodulation, TGF-β insensitivity, and upregulated integrin activity. Biological relevance is supported by the identification of a favorable γδ[T2] signature in acute myeloid leukemia (AML). Given their enhanced therapeutic activity and compatibility with allogeneic use, γδ[T2] cells warrant evaluation in cancer immunotherapy.

Sustained Post-Developmental T-Bet Expression Is Critical for the Maintenance of Type One Innate Lymphoid Cells In Vivo

Innate lymphoid cells (ILC) play a significant role in the intestinal immune response and T-bet+ CD127+ group 1 cells (ILC1) have been linked to the pathogenesis of human inflammatory bowel disease (IBD). However, the functional importance of ILC1 in the context of an intact adaptive immune response has been controversial. In this report we demonstrate that induced depletion of T-bet using a Rosa26-Cre-ERT2 model resulted in the loss of intestinal ILC1, pointing to a post-developmental requirement of T-bet expression for these cells. In contrast, neither colonic lamina propria (cLP) ILC2 nor cLP ILC3 abundance were altered upon induced deletion of T-bet. Mechanistically, we report that STAT1 or STAT4 are not required for intestinal ILC1 development and maintenance. Mice with induced deletion of T-bet and subsequent loss of ILC1 were protected from the induction of severe colitis in vivo. Hence, this study provides support for the clinical development of an IBD treatment based on ILC1 depletion via targeting T-bet or its downstream transcriptional targets.

ILC1 drive intestinal epithelial and matrix remodelling

Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we develop gut organoid cocultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate that murine and human ILC1 secrete transforming growth factor β1, driving expansion of CD44v6+ epithelial crypts. ILC1 additionally express MMP9 and drive gene signatures indicative of extracellular matrix remodelling. We therefore encapsulated human epithelial-mesenchymal intestinal organoids in MMP-sensitive, synthetic hydrogels designed to form efficient networks at low polymer concentrations. Harnessing this defined system, we demonstrate that ILC1 drive matrix softening and stiffening, which we suggest occurs through balanced matrix degradation and deposition. Our platform enabled us to elucidate previously undescribed interactions between ILC1 and their microenvironment, which suggest that they may exacerbate fibrosis and tumour growth when enriched in inflamed patient tissues.

CAR T-Cells Targeting the Integrin αvβ6 and Co-Expressing the Chemokine Receptor CXCR2 Demonstrate Enhanced Homing and Efficacy against Several Solid Malignancies

Despite the unprecedented clinical success of chimeric antigen receptors (CAR) T-cells against haematological malignancy, solid tumors impose a far greater challenge to success. Largely, this stems from an inadequate capacity of CAR T-cells that can traffic and maintain function within a hostile microenvironment. To enhance tumor-directed T-cell trafficking, we have engineered CAR T-cells to acquire heightened responsiveness to interleukin (IL)-8. Circulating IL-8 levels correlate with disease burden and prognosis in multiple solid tumors in which it exerts diverse pathological functions including angiogenesis, support of cancer stem cell survival, and recruitment of immunosuppressive myeloid cells. To harness tumor-derived IL-8 for therapeutic benefit, we have co-expressed either of its cognate receptors (CXCR1 or CXCR2) in CAR T-cells that target the tumor-associated αvβ6 integrin. We demonstrate here that CXCR2-expressing CAR T-cells migrate more efficiently towards IL-8 and towards tumor conditioned media that contains this cytokine. As a result, these CAR T-cells elicit superior anti-tumor activity against established αvβ6-expressing ovarian or pancreatic tumor xenografts, with a more favorable toxicity profile. These data support the further engineering of CAR T-cells to acquire responsiveness to cancer-derived chemokines in order to improve their therapeutic activity against solid tumors.

CAR T-cell immunotherapy of MET-expressing malignant mesothelioma

Mesothelioma is an incurable cancer for which effective therapies are required. Aberrant MET expression is prevalent in mesothelioma, although targeting using small molecule-based therapeutics has proven disappointing. Chimeric antigen receptors (CARs) couple the HLA-independent binding of a cell surface target to the delivery of a tailored T-cell activating signal. Here, we evaluated the anti-tumor activity of MET re-targeted CAR T-cells against mesothelioma. Using immunohistochemistry, MET was detected in 67% of malignant pleural mesotheliomas, most frequently of epithelioid or biphasic subtype. The presence of MET did not influence patient survival. Candidate MET-specific CARs were engineered in which a CD28+CD3ζ endodomain was fused to one of 3 peptides derived from the N and K1 domains of hepatocyte growth factor (HGF), which represents the minimum MET binding element present in this growth factor. Using an NIH3T3-based artificial antigen-presenting cell system, we found that all 3 candidate CARs demonstrated high specificity for MET. By contrast, these CARs did not mediate T-cell activation upon engagement of other HGF binding partners, namely CD44v6 or heparan sulfate proteoglycans, including Syndecan-1. NK1-targeted CARs demonstrated broadly similar in vitro potency, indicated by destruction of MET-expressing mesothelioma cell lines, accompanied by cytokine release. In vivo anti-tumor activity was demonstrated following intraperitoneal delivery to mice with an established mesothelioma xenograft. Progressive tumor regression occurred without weight loss or other clinical indicators of toxicity. These data confirm the frequent expression of MET in malignant pleural mesothelioma and demonstrate that this can be targeted effectively and safely using a CAR T-cell immunotherapeutic strategy.

Targeting of Aberrant αvβ6 Integrin Expression in Solid Tumors Using Chimeric Antigen Receptor-Engineered T Cells

Expression of the αvβ6 integrin is upregulated in several solid tumors. In contrast, physiologic expression of this epithelial-specific integrin is restricted to development and epithelial re-modeling. Here, we describe, for the first time, the development of a chimeric antigen receptor (CAR) that couples the recognition of this integrin to the delivery of potent therapeutic activity in a diverse repertoire of solid tumor models. Highly selective targeting αvβ6 was achieved using a foot and mouth disease virus-derived A20 peptide, coupled to a fused CD28⁺CD3 endodomain. To achieve selective expansion of CAR T cells ex vivo, an IL-4-responsive fusion gene (4αβ) was co-expressed, which delivers a selective mitogenic signal to engineered T cells only. In vivo efficacy was demonstrated in mice with established ovarian, breast, and pancreatic tumor xenografts, all of which express αvβ6 at intermediate to high levels. SCID beige mice were used for these studies because they are susceptible to cytokine release syndrome, unlike more immune-compromised strains. Nonetheless, although the CAR also engages mouse αvβ6, mild and reversible toxicity was only observed when supra-therapeutic doses of CAR T cells were administered parenterally. These data support the clinical evaluation of αvβ6 re-targeted CAR T cell immunotherapy in solid tumors that express this integrin.

Abstract B129: Chimeric antigen receptor T-cells targeting the αvβ6 integrin demonstrate potent antitumor activity in multiple solid tumors

Chimeric antigen receptors (CARs) are bespoke fusion molecules that couple the binding of a tumor-associated cell surface target to the delivery of a tailored T-cell activating signal. CAR T-cells targeting CD19 have demonstrated unprecedented efficacy in the treatment of patients with refractory B-cell malignancy although solid tumors present several additional hurdles to the development of CAR T-cell immunotherapy. One such hurdle is identifying suitable target antigens to maximise tumor targeting and minimise toxicity to healthy tissue. A highly promising candidate is the epithelial-specific integrin, αvβ6. Here, we demonstrate that CAR T-cells targeting αvβ6 have potent anti-tumor activity across a wide range of solid malignancies in pre-clinical models.

The αvβ6 integrin is over-expressed in solid tumors derived from pancreas, head and neck, skin, uterine cervix, lung, colon, breast and fallopian tube/ovary and is generally associated with worsened prognosis. It exerts several pro-tumorigenic activities including activation of TGF-β1, epithelial to mesenchymal transition, cellular migration and matrix metalloproteinase activity. By contrast, αvβ6 is minimally expressed in normal tissue and expression is largely restricted to wound healing.

We have evaluated two peptide-targeting moieties to direct specificity of an αvβ6-specific CD28+CD3ζ-based second generation CAR (A20-28z). We show that a 20mer peptide derived from viral protein 1 of foot and mouth disease virus achieves highly effective targeting. This 20mer peptide (termed A20) contains two αvβ6-binding motifs (RGD and DLXXL) and binds with >1000-fold more specificity to this integrin than other family members such as αvβ3, αvβ5 and α5β1. To evaluate anti-tumor activity we compared A20-28z with two control CAR constructs. An αvβ6 non-binding peptide was generated in which the RGDL motif within A20FMDV2 was substituted with AAAA (termed C20) and a non-signaling CAR constructed whereby A20 was fused to a truncated CD28 endodomain (termed A20-Tr).

A20-28z T-cells destroy and undergo activation by a range of pancreatic, breast and ovarian tumor cell lines in-vitro. By contrast, cells that express low but detectable levels of this integrin are ignored. To expand CAR T-cells preferentially during ex-vivo culture, an IL-4-responsive fusion gene (4βα) was co-expressed which delivers a potent and selective mitogenic signal only to the genetically modified T-cells. In-vivo efficacy of αvβ6 re-targeted human CAR T-cells was demonstrated in SCID Beige mice bearing established Panc04.03 pancreatic and SKOV-3 ovarian tumor xenografts, that express high and intermediate levels of αvβ6 respectively. Ovarian tumor response was significant, but was ultimately limited by transient in-vivo CAR T-cell expansion followed by progressive loss thereafter. In contrast, pancreatic tumours with high αvβ6 expression demonstrated significant tumor regression in response to A20-28z T-cells and exhibited durable responses.

Although the CAR targeting moiety engages murine αvβ6, minimal toxicity was observed in these mouse models, which can fully recapitulate lethal cytokine release syndrome in response to human CAR T-cells. Taken together, these data provide strong support for the clinical evaluation of αvβ6 re-targeted CAR T-cell immunotherapy in solid tumors that express this integrin.

Citation Format: Lynsey May Whilding, Ana C. Parente-Pereira, Tomasz Zabinski, David M. Davies, Roseanna Petrovic, Shelia Violette, Sadaf Ghaem-Maghami, Sabari Vallath, John Marshall, John Maher. Chimeric antigen receptor T-cells targeting the αvβ6 integrin demonstrate potent antitumor activity in multiple solid tumors. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B129.

Abstract B124: Immunotherapy of acute myeloid leukemia using Vg9Vd2 T-cells

Disease remission is successfully induced in the majority of patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS), but is generally not sustained without stem cell transplantation. Adoptive immunotherapy offers an attractive option to consolidate AML remission. Here, we hypothesized that ex-vivo expanded Vg9Vd2 T-cells will mediate a therapeutically beneficial graft versus leukemia (GvL) effect in this disease.

Peripheral blood mononuclear cells from healthy donors and from patients with AML were activated in-vitro using zoledronic acid and a cytokine cocktail, containing IL-2. As a result, we observed an average 200-fold expansion of Vg9Vd2 T-cells from AML patients, over 15 days. Such expansion was only observed in patients without circulating AML blasts. Expanded patient-derived Vg9Vd2 T-cells exhibited a less differentiated phenotype than cells from healthy donors, indicated by higher expression of CD62L, CCR7 and CD27. A four hour Annexin V cytotoxicity assay using KG-1 and U937 leukemic cells showed that these Vg9Vd2 T-cells were cytotoxic and produced nanogram amounts of interferon-g; (IFN-g).

In a parallel approach, we investigated feasibility of developing a universal allogeneic Vg9Vd2 T-cell therapy. Feasibility of this approach has been demonstrated in a small trial in which haploidentical donor-derived Vg9Vd2 T-cells were safely infused and achieved an efficacy signal in patients with advanced haematological diseases. We have recently developed a novel method to expand Vg9Vd2 T-cells from healthy donors ex-vivo (“Method 2 (M2)” cells – patent protected), which improves their expansion over 2 weeks to 1700 fold. Cytotoxicity data shows that M2 cells destroy luciferase-expressing U937 and KG-1 target cells at 2-3 fold enhanced efficiency, accompanied by 2-3.5-fold increased IFN-g; release when compared to cells expanded using conventional approaches. Furthermore, M2 cells can achieve serial killing of AML cell lines through up to 4 cycles of re-stimulation. Treatment of SCID-Beige mice with an established U937 leukemic burden is also more effective using M2 expanded Vg9Vd2 T-cells, particularly when combined with zoledronic acid. Together these data highlight the promise of Vg9Vd2 T-cell immunotherapy of AML.

Citation Format: Ana C. Parente-Pereira, Lynsey M. Whilding, Pramila Krishnamurthy, Richard Beatson, Tomasz Zabinski, Linda Barber, Farzin Farzaneh, Ghulam Mufti, John Maher. Immunotherapy of acute myeloid leukemia using Vg9Vd2 T-cells. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B124.

Adoptive Immunotherapy of Epithelial Ovarian Cancer with Vγ9Vδ2 T Cells, Potentiated by Liposomal Alendronic Acid

Adoptive immunotherapy using γδ T cells harnesses their natural role in tumor immunosurveillance. The efficacy of this approach is enhanced by aminobisphosphonates such as zoledronic acid and alendronic acid, both of which promote the accumulation of stimulatory phosphoantigens in target cells. However, the inefficient and nonselective uptake of these agents by tumor cells compromises the effective clinical exploitation of this principle. To overcome this, we have encapsulated aminobisphosphonates within liposomes. Expanded Vγ9Vδ2 T cells from patients and healthy donors displayed similar phenotype and destroyed autologous and immortalized ovarian tumor cells, following earlier pulsing with either free or liposome-encapsulated aminobisphosphonates. However, liposomal zoledronic acid proved highly toxic to SCID Beige mice. By contrast, the maximum tolerated dose of liposomal alendronic acid was 150-fold higher, rendering it much more suited to in vivo use. When injected into the peritoneal cavity, free and liposomal alendronic acid were both highly effective as sensitizing agents, enabling infused γδ T cells to promote the regression of established ovarian tumors by over one order of magnitude. Importantly however, liposomal alendronic acid proved markedly superior compared with free drug following i.v. delivery, exploiting the “enhanced permeability and retention effect” to render advanced tumors susceptible to γδ T cell–mediated shrinkage. Although folate targeting of liposomes enhanced the sensitization of folate receptor–α+ ovarian tumor cells in vitro, this did not confer further therapeutic advantage in vivo. These findings support the development of an immunotherapeutic approach for ovarian and other tumors in which adoptively infused γδ T cells are targeted using liposomal alendronic acid.