An ultrastructural investigation of tumors undergoing regression mediated by immunotherapy

A Histone Deacetylase Inhibitor, Panobinostat, Enhances Chimeric Antigen Receptor T-cell Antitumor Effect Against Pancreatic Cancer

PURPOSE

In this article, we describe a combination chimeric antigen receptor (CAR) T-cell therapy that eradicated the majority of tumors in two immunocompetent murine pancreatic cancer models and a human pancreatic cancer xenograft model.

EXPERIMENTAL DESIGN

We used a dual-specific murine CAR T cell that expresses a CAR against the Her2 tumor antigen, and a T-cell receptor (TCR) specific for gp100. As gp100 is also known as pMEL, the dual-specific CAR T cells are thus denoted as CARaMEL cells. A vaccine containing live vaccinia virus coding a gp100 minigene (VV-gp100) was administered to the recipient mice to stimulate CARaMEL cells. The treatment also included the histone deacetylase inhibitor panobinostat (Pano).

RESULTS

The combination treatment enabled significant suppression of Her2⁺ pancreatic cancers leading to the eradication of the majority of the tumors. Besides inducing cancer cell apoptosis, Pano enhanced CAR T-cell gene accessibility and promoted CAR T-cell differentiation into central memory cells. To test the translational potential of this approach, we established a method to transduce human T cells with an anti-Her2 CAR and a gp100-TCR. The exposure of the human T cells to Pano promoted a T-cell central memory phenotype and the combination treatment of human CARaMEL cells and Pano eradicated human pancreatic cancer xenografts in mice.

CONCLUSIONS

We propose that patients with pancreatic cancer could be treated using a scheme that contains dual-specific CAR T cells, a vaccine that activates the dual-specific CAR T cells through their TCR, and the administration of Pano.

Understanding T cell phenotype for the design of effective chimeric antigen receptor T cell therapies

Rapid advances in immunotherapy have identified adoptive cell transfer as one of the most promising approaches for the treatment of cancers. Large numbers of cancer reactive T lymphocytes can be generated ex vivo from patient blood by genetic modification to express chimeric antigen receptors (CAR) specific for tumor-associated antigens. CAR T cells can respond strongly against cancer cells, and adoptive transferred CAR T cells can induce dramatic responses against certain types of cancers. The ability of T cells to respond against disease depends on their ability to localize to sites, persist and exert functions, often in an immunosuppressive microenvironment, and these abilities are reflected in their phenotypes. There is currently intense interest in generating CAR T cells possessing the ideal phenotypes to confer optimal antitumor activity. In this article, we review T cell phenotypes for trafficking, persistence and function, and discuss how culture conditions and genetic makeups can be manipulated to achieve the ideal phenotypes for antitumor activities.

Enhancing chimeric antigen receptor T-cell immunotherapy against cancer using a nanoemulsion-based vaccine targeting cross-presenting dendritic cells

Objectives

Adoptive transfer of chimeric antigen receptor (CAR)-modified T cells is a form of cancer immunotherapy that has achieved remarkable efficacy in patients with some haematological cancers. However, challenges remain in CAR T-cell treatment of solid tumours because of tumour-mediated immunosuppression.

Methods

We have demonstrated that CAR T-cell stimulation through T-cell receptors (TCRs) in vivo can generate durable responses against solid tumours in a variety of murine models. Since Clec9A-targeting tailored nanoemulsion (Clec9A-TNE) vaccine enhances antitumour immune responses through selective activation of Clec9A⁺ cross-presenting dendritic cells (DCs), we hypothesised that Clec9A-TNE could prime DCs for antigen presentation to CAR T cells through TCRs and thus improve CAR T-cell responses against solid tumours. To test this hypothesis, we used CAR T cells expressing transgenic TCRs specific for ovalbumin (OVA) peptides SIINFEKL (CAROTI) or OVA_323-339 (CAROTII).

Results

We demonstrated that the Clec9A-TNEs encapsulating full-length recombinant OVA protein (OVA-Clec9A-TNE) improved CAROT T-cell proliferation and inflammatory cytokine secretion in vitro. Combined treatment using the OVA-Clec9A-TNE and CAROT cells resulted in durable responses and some rejections of tumours in immunocompetent mice. Tumour regression was accompanied by enhanced CAROT cell proliferation and infiltration into the tumours.

Conclusion

Our study presents Clec9A-TNE as a prospective avenue to enhance CAR T-cell efficacy for solid cancers.

Dendritic Cell-Based Therapy Using LY6E Peptide with a Putative Role Against Colorectal Cancer

Introduction

Albeit early stage gastrointestinal (GI) carcinomas have a good prognosis if treated with surgery, diagnosis is often confirmed at a late stage and efficacious drugs are lacking. Recent progress in immune-based therapies has focused on dendritic cells (DCs), aiming to elicit tumor-specific responses by inducing immunological memory. Our previous microarray study indicated that a biomarker, termed lymphocyte antigen-6E (LY6E), is commonly overexpressed in two potentially lethal GI cancers: those of colon and stomach. In this study, we examined the antigenic potency of LY6E in stimulating DCs.

Methods

Following isolation, differentiation, and maturation of mononuclear cells, DCs were pulsed with LY6E peptide, a protein related to major histocompatibility complex (MHC) class I/II. Subsequently, DCs were co-cultured with mouse splenocytes to assess antigen-specific T-cell proliferation. Elucidated cytotoxic T-lymphocyte responses were assessed using subcutaneous colorectal murine tumor models.

Results

Our in vitro results suggest that DCs loaded with LY6E peptide antigen are capable of stimulating and inducing proliferation of murine T-cells. Furthermore, our in vivo results demonstrate that LY6E peptide has a substantial impact on provoking immune responses against induced colon cancer in mice.

Discussion

In conclusion, based on the overexpression of LY6E in colorectal, gastric, and pancreatic cancers, the role of this peptide should be further investigated with a goal of developing new therapies for these challenging diseases.

Genetic Redirection of T Cells for the Treatment of Pancreatic Cancer

Conventional treatments for pancreatic cancer are largely ineffective, and the prognosis for the vast majority of patients is poor. Clearly, new treatment options are desperately needed. Immunotherapy offers hope for the development of treatments for pancreatic cancer. A central requirement for the efficacy of this approach is the existence of cancer antigen-specific T cells, but these are often not present or difficult to isolate for most pancreatic tumors. Nevertheless, specific T cells can be generated using genetic modification to express chimeric antigen receptors (CAR), which can enable T cell responses against pancreatic tumor cells. CAR T cells can be produced ex vivo and expanded in vitro for infusion into patients. Remarkable responses have been documented using CAR T cells against several malignancies, including leukemias and lymphomas. Based on these successes, the extension of CAR T cell therapy for pancreatic cancer holds great promise. However, there are a number of challenges that limit the full potential of CAR T cell therapies for pancreatic cancer, including the highly immunosuppressive tumor microenvironment (TME). In this article, we will review the recent progress in using CAR T cells in pancreatic cancer preclinical and clinical settings, discuss hurdles for utilizing the full potential of CAR T cell therapy and propose research strategies and future perspectives. Research into the use of CAR T cell therapy in pancreatic cancer setting is rapidly gaining momentum and understanding strategies to overcome the current challenges in the pancreatic cancer setting will allow the development of effective CAR T cell therapies, either alone or in combination with other treatments to benefit pancreatic cancer patients.