Adoptive T cell therapy: An overview of obstacles and opportunities

Reprogramming lymphocytes for the treatment of melanoma: From biology to therapy

This decade has introduced drastic changes in melanoma therapy, predominantly due to the materialization of the long promise of immunotherapy. Cytotoxic T cells are the chief component of the immune system, which are targeted by different strategies aimed to increase their capacity against melanoma cells. To this end, reprogramming of T cells occurs by T cell centered manipulation, targeting the immunosuppressive tumor microenvironment or altering the whole patient. These are enabled by delivery of small molecules, functional monoclonal antibodies, different subunit vaccines, as well as living lymphocytes, native or genetically engineered. Current FDA-approved therapies are focused on direct T cell manipulation, such as immune checkpoint inhibitors blocking CTLA-4 and/or PD-1, which paves the way for an effective immunotherapy backbone available for combination with other modalities. Here we review the biology and clinical developments that enable melanoma immunotherapy today and in the future.

BRAF Targeting Sensitizes Resistant Melanoma to Cytotoxic T Cells

PURPOSE

BRAF and MEK inhibitors (BRAFi and MEKi) are actively used for the treatment of metastatic melanoma in patients with BRAF^V600E mutation in their tumors. However, the development of resistance to BRAFi and MEKi remains a difficult clinical challenge with limited therapeutic options available to these patients. In this study, we investigated the mechanism and potential therapeutic utility of combination BRAFi and adoptive T-cell therapy (ACT) in melanoma resistant to BRAFi.

EXPERIMENTAL DESIGN

Investigations were performed in vitro and in vivo with various human melanoma cell lines sensitive and resistant to BRAFi as well as patient-derived xenografts (PDX) derived from patients. In addition, samples were evaluated from patients on a clinical trial of BRAFi in combination with ACT.

RESULTS

Herein we report that in human melanoma cell lines, senstitive and resistant to BRAFi and in PDX from patients who progressed on BRAFi and MEKi therapy, BRAFi caused transient upregulation of mannose-6-phosphate receptor (M6PR). This sensitized tumor cells to CTLs via uptake of granzyme B, a main component of the cytotoxic activity of CTLs. Treatment of mice bearing resistant tumors with BRAFi enhanced the antitumor effect of patients' TILs. A pilot clinical trial of 16 patients with metastatic melanoma who were treated with the BRAFi vemurafenib followed by therapy with TILs demonstrated a significant increase of M6PR expression on tumors during vemurafenib treatment.

CONCLUSIONS

BRAF-targeted therapy sensitized resistant melanoma cells to CTLs, which opens new therapeutic opportunities for the treatment of patients with BRAF-resistant disease.See related commentary by Goff and Rosenberg, p. 2682.

Bio-Orthogonal T Cell Targeting Strategy for Robustly Enhancing Cytotoxicity against Tumor Cells

T cells can kill tumor cells by cell surface immunological recognition, but low affinity for tumor-associated antigens could lead to T cell off-target effects. Herein, a universal T cell targeting strategy based on bio-orthogonal chemistry and glycol-metabolic engineering is introduced to enhance recognition and cytotoxicity of T cells in tumor immunotherapy. Three kinds of bicycle [6.1.0] nonyne (BCN)-modified sugars are designed and synthesized, in which Ac₄ ManN-BCN shows efficient incorporation into wide tumor cells with a BCN motif on surface glycans. Meanwhile, activated T cells are treated with Ac₄ GalNAz to introduce azide (N₃ ) on the cell surface, initiating specific tumor targeting through a bio-orthogonal click reaction between N₃ and BCN. This artificial targeting strategy remarkably enhances recognition and migration of T cells to tumor cells, and increases the cytotoxicity 2 to 4 times for T cells against different kinds of tumor cells. Surprisingly, based on this strategy, the T cells even exhibit similar cytotoxicity with the chimeric antigen receptor T-cell against Raji cells in vitro at the effector: target cell ratios (E:T) of 1:1. Such a universal bio-orthogonal T cell-targeting strategy might further broaden applications of T cell therapy against tumors and provide a new strategy for T cell modification.

TCR repertoire intratumor heterogeneity of CD4+ and CD8+ T cells in centers and margins of localized lung adenocarcinomas

Intratumor heterogeneity (ITH) of T cell receptor (TCR) repertoire in different T-cell subsets and locations in lung adenocarcinomas was unclear. Here, we investigated percentages and TCR repertoire of freshly isolated CD4⁺ and CD8⁺ tumor infiltrating lymphocytes (TILs) in tumor centers and margins by flow cytometry on 80 tumor samples from 20 patients and high-throughput TCR sequencing on 27 and 25 samples of CD4⁺ and CD8⁺ TILs from seven patients. Our results demonstrated that amount and TCR repertoire diversity of CD4⁺ TILs were significantly higher than those of CD8⁺ TILs and moreover substantial ITH regarding amount and TCR repertoire of CD4⁺ and CD8⁺ TILs were observed. Additionally, ITH of CD4/CD8 T-cell ratio and CD8⁺ TIL repertoire across center regions was lower than that across margin regions. The amount and TCR repertoire ITH of CD4⁺ and CD8⁺ TILs and mean clonality of CD8⁺ TILs in tumor centers were associated with relapse. Our study provides insights into amount and TCR repertoire ITH of CD4⁺ and CD8⁺ TILs in tumor centers and margins as well as corresponding association with prognosis in lung adenocarcinoma patients, suggesting potential clinical significance of TCR repertoire.

Photochemical Treatment of Drosophila APCs Can Eliminate Associated Viruses and Maintain the APC Function for Generating Antigen-Specific CTLs Ex Vivo

Drosophila cells transfected with MHC class I and a number of costimulation molecules including B7.1, ICAM, LFA-3, and CD70 are potent antigen-presenting cells (APCs) for the generation of antigen-specific cytotoxic T cells (CTLs) in vitro. Using Drosophila APCs, CTLs specific for melanoma antigens have been generated in vitro and adoptively transferred to melanoma patients. However, the recent discovery that Drosophila cells can carry insect viruses raises the potential risk of Drosophila APCs transmitting xenogenic viruses to patient CTLs. In this study, we have investigated photoreactive methods to inactivate insect viruses in APC. A clinical grade psoralen compound, 8-MOP (UVADEX) in combination with UVA treatment (5 joules/cm²) can be used to inactivate Drosophila cell viruses. UVADEX treatment is sufficient to inactivate insect viruses but does not affect the expression of MHC class I molecules and costimulation molecules on Drosophila APCs. In fact, UVADEX treatment prevents Drosophila APC growth while maintaining APC function. Furthermore, UVADEX-treated Drosophila APCs maintain or have enhanced APC function as determined by enhanced T cell activation, proliferation, and CTL generation. Thus, the use of UVADEX-treated Drosophila APCs may provide a valuable tool for immunotherapy to generate tumor antigen-specific CTLs.

Stereotactic Adoptive Transfer of Cytotoxic Immune Cells in Murine Models of Orthotopic Human Glioblastoma Multiforme Xenografts

Glioblastoma multiforme (GBM), the most frequent and aggressive primary brain cancer in adults, is generally associated with a poor prognosis, and scarce efficient therapies have been proposed over the last decade. Among the promising candidates for designing novel therapeutic strategies, cellular immunotherapies have been targeted to eliminate highly invasive and chemo-radioresistant tumor cells, likely involved in a rapid and fatal relapse of this cancer. Thus, administration(s) of allogeneic GBM-reactive immune cell effectors, such as human Vϒ9Vδ2 T lymphocytes, in the vicinity of the tumor would represents a unique opportunity to deliver efficient and highly concentrated therapeutic agents directly into the site of brain malignancies. Here, we present a protocol for the preparation and the stereotaxic administration of allogeneic human lymphocytes in immunodeficient mice carrying orthotopic human primary brain tumors. This study provides a preclinical proof-of-concept for both the feasibility and the antitumor efficacy of these cellular immunotherapies that rely on stereotactic injections of allogeneic human lymphocytes within intrabrain tumor beds.

Cholesterol negatively regulates IL-9-producing CD8+ T cell differentiation and antitumor activity

CD8⁺ T cells can be polarized into IL-9-secreting (Tc9) cells. We previously showed that adoptive therapy using tumor-specific Tc9 cells generated stronger antitumor responses in mouse melanoma than classical Tc1 cells. To understand why Tc9 cells exert stronger antitumor responses, we used gene profiling to compare Tc9 and Tc1 cells. Tc9 cells expressed different levels of cholesterol synthesis and efflux genes and possessed significantly lower cholesterol content than Tc1 cells. Unique to Tc9, but not other CD8⁺ or CD4⁺ T cell subsets, manipulating cholesterol content in polarizing Tc9 cells significantly affected IL-9 expression and Tc9 differentiation and antitumor response in vivo. Mechanistic studies showed that IL-9 was indispensable for Tc9 cell persistence and antitumor effects, and cholesterol or its derivatives inhibited IL-9 expression by activating liver X receptors (LXRs), leading to LXR Sumoylation and reduced p65 binding to Il9 promoter. Our study identifies cholesterol as a critical regulator of Tc9 cell differentiation and function.

Continuous production process of retroviral vector for adoptive T- cell therapy

Adoptive T-Cell therapy is being considered as a promising method for cancer treatment. In this approach, patient's T cells are isolated, modified, expanded, and administered back to the patient. Modifications may include adding specific T cell receptors (TCR) or chimeric antigen receptors (CAR) to the isolated cells by using retroviral vectors. PG13 cells, derivatives of NIH3T3 mouse fibroblasts, are being used to stably produce retroviral vectors that transduce the T cells. PG13 cells are anchorage-dependent cells that grow in roller bottles or cell factories and lately also in fixed bed bioreactors to produce the needed viral vector. To scale up viral vector production, PG13 cells were propagated on microcarriers in a stirred tank bioreactor utilizing an alternating tangential flow perfusion system. Microcarriers are 10 µm - 0.5 mm beads that support the attachment of cells and are suspended in the bioreactor that provides controlled growth conditions. As a result, growth parameters, such as dissolved oxygen concentration, pH, and nutrients are monitored and continuously controlled. There were no detrimental effects on the specific viral vector titer or on the efficacy of the vector in transducing the T cells of several patients. Viral vector titer increased throughout the 11 days perfusion period, a total of 4.8 × 10¹¹ transducing units (TU) were obtained with an average titer of 4.4 × 10⁷ TU/mL and average specific productivity of 10.3 (TU) per cell, suggesting that this method can be an efficient way to produce large quantities of active vector suitable for clinical use.

Immunotherapy for Hepatocellular Carcinoma: Current Advances and Future Expectations

Primary liver cancer is a common kind of digestive cancers with high malignancy, causing 745,500 deaths each year. Hepatocellular carcinoma is the major pathological type of primary liver cancer. Traditional treatment methods for patients with hepatocellular carcinoma have shown poor efficacy in killing residual cancer cells for a long time. In recent years, tumor immunotherapy has emerged as a promising method owing to its safety and efficacy with respect to delaying the progression of advanced tumors and protecting postoperative patients against tumor relapse and metastasis. Immune tolerance and suppression in tumor microenvironments are the theoretical basis of immunotherapy. Adoptive cell therapy functions by stimulating and cultivating autologous lymphocytes ex vivo and then reinfusing them into the patient to kill cancer cells. Cancer vaccination is performed using antigenic substances to activate tumor-specific immune responses. Immune checkpoint inhibitors can reactivate tumor-specific T cells and develop an antitumor effect by suppressing checkpoint-mediated signaling. Oncolytic viruses may selectively replicate in tumor cells and cause lysis without harming normal tissues. Here, we briefly introduce the mechanism of immunosuppression in hepatocellular carcinoma and summarize the rationale of the four major immunotherapeutic approaches with their current advances.

Immunotherapy for Melanoma

While melanoma is less common than some other skin cancers, it is responsible for nearly 10,000 deaths in the USA each year alone. For many decades, very limited treatment options were available for patients with metastatic melanoma. However, recent breakthroughs have brought new hopes for patients and providers.While targeted therapy with BRAF and MEK inhibitors represents an important cornerstone in the treatment of metastatic melanoma, this chapter carefully reviews the past and current therapy options available, with a significant focus on immunotherapy-based approaches. In addition, we provide an overview of the results of recent advances in the adjuvant setting for patients with resected stage III and stage IV melanoma, as well as in patients with melanoma brain metastases. Finally, we provide a quick overview over the current research efforts in the field of immuno-oncology and melanoma.

Recent Successes and Future Directions in Immunotherapy of Cutaneous Melanoma

The global health burden associated with melanoma continues to increase while treatment options for metastatic melanoma are limited. Nevertheless, in the past decade, the field of cancer immunotherapy has witnessed remarkable advances for the treatment of a number of malignancies including metastatic melanoma. Although the earliest observations of an immunological antitumor response were made nearly a century ago, it was only in the past 30 years, that immunotherapy emerged as a viable therapeutic option, in particular for cutaneous melanoma. As such, melanoma remains the focus of various preclinical and clinical studies to understand the immunobiology of cancer and to test various tumor immunotherapies. Here, we review key recent developments in the field of immune-mediated therapy of melanoma. Our primary focus is on therapies that have received regulatory approval. Thus, a brief overview of the pathophysiology of melanoma is provided. The purported functions of various tumor-infiltrating immune cell subsets are described, in particular the recently described roles of intratumoral dendritic cells. The section on immunotherapies focuses on strategies that have proved to be the most clinically successful such as immune checkpoint blockade. Prospects for novel therapeutics and the potential for combinatorial approaches are delineated. Finally, we briefly discuss nanotechnology-based platforms which can in theory, activate multiple arms of immune system to fight cancer. The promising advances in the field of immunotherapy signal the dawn of a new era in cancer treatment and warrant further investigation to understand the opportunities and barriers for future progress.

Targeting immune checkpoints in breast cancer: an update of early results

The immune tumour microenvironment has been shown to play a crucial role in the development and progression of cancer. Expression of gene signatures, reflecting immune activation, and the presence of tumour-infiltrating lymphocytes were associated with favourable outcomes in HER2-positive and triple-negative breast cancer. Recently, immunotherapy with immune checkpoint blockade induced long-lasting responses and improved survival in hard-to-treat malignancies (ie, melanoma and non-small cell lung cancer) and are changing treatment paradigms in a variety of neoplastic diseases. Immune checkpoint blockade has been evaluated in breast cancer, particularly in the triple-negative subtype, with promising results observed in monotherapy or in combination with chemotherapy in the metastatic and neoadjuvant settings. However, identification of patients who are most likely to benefit from immune checkpoint blockade remains challenging, with many patients not responding to treatments and a significant financial cost. The combination of immune checkpoint blockade with conventional cancer treatments such as chemotherapy, radiotherapy, targeted therapies or with other immunotherapies is a promising strategy to potentiate its efficacy in breast cancer although further research is required to effectively identify who will respond to these immunotherapies. In this review we report the most recent results that emerged from trials testing immune checkpoint blockade and potential predictive biomarkers and emphasise the new strategies that are under clinical development in breast cancer.