Improving immunotherapy for colorectal cancer using dendritic cells combined with anti-programmed death-ligand in vitro

The role of autophagy in colorectal cancer: Impact on pathogenesis and implications in therapy

Colorectal cancer (CRC) is considered as a global major cause of cancer death. Surgical resection is the main line of treatment; however, chemo-, radiotherapy and other adjuvant agents are crucial to achieve good outcomes. The tumor microenvironment (TME) is a well-recognized key player in CRC progression, yet the processes linking the cancer cells to its TME are not fully delineated. Autophagy is one of such processes, with a controversial role in the pathogenesis of CRC, with its intricate links to many pathological factors and processes. Autophagy may apparently play conflicting roles in carcinogenesis, but the precise mechanisms determining the overall direction of the process seem to depend on the context. Additionally, it has been established that autophagy has a remarkable effect on the endothelial cells in the TME, the key substrate for angiogenesis that supports tumor metastasis. Favorable response to immunotherapy occurs only in a specific subpopulation of CRC patients, namely the microsatellite instability-high (MSI-H). In view of such limitations of immunotherapy in CRC, modulation of autophagy represents a potential adjuvant strategy to enhance the effect of those relatively safe agents on wider CRC molecular subtypes. In this review, we discussed the molecular control of autophagy in CRC and how autophagy affects different processes and mechanisms that shape the TME. We explored how autophagy contributes to CRC initiation and progression, and how it interacts with tumor immunity, hypoxia, and oxidative stress. The crosstalk between autophagy and the TME in CRC was extensively dissected. Finally, we reported the clinical efforts and challenges in combining autophagy modulators with various cancer-targeted agents to improve CRC patients’ survival and restrain cancer growth.

The Role of Tumor Microenvironment and Immune Response in Colorectal Cancer Development and Prognosis

Colorectal cancer (CRC) is one of the most common cancers worldwide. The patient’s prognosis largely depends on the tumor stage at diagnosis. The pathological TNM Classification of Malignant Tumors (pTNM) staging of surgically resected cancers represents the main prognostic factor and guidance for decision-making in CRC patients. However, this approach alone is insufficient as a prognostic predictor because clinical outcomes in patients at the same histological tumor stage can still differ. Recently, significant progress in the treatment of CRC has been made due to improvements in both chemotherapy and surgical management. Immunotherapy-based approaches are one of the most rapidly developing areas of tumor therapy. This review summarizes the current knowledge about the tumor microenvironment (TME), immune response and its interactions with CRC development, immunotherapy and prognosis.

Advances in Human Dendritic Cell-Based Immunotherapy Against Gastrointestinal Cancer

Dendritic cells (DCs), the strongest antigen-presenting cells, are a focus for orchestrating the immune system in the fight against cancer. Basic scientific investigations elucidating the cellular biology of the DCs have resulted in new strategies in this fight, including cancer vaccinology, combination therapy, and adoptive cellular therapy. Although immunotherapy is currently becoming an unprecedented bench-to-bedside success, the overall response rate to the current immunotherapy in patients with gastrointestinal (GI) cancers is pretty low. Here, we have carried out a literature search of the studies of DCs in the treatment of GI cancer patients. We provide the advances in DC-based immunotherapy and highlight the clinical trials that indicate the therapeutic efficacies and toxicities related with each vaccine. Moreover, we also offer the yet-to-be-addressed questions about DC-based immunotherapy. This study focuses predominantly on the data derived from human studies to help understand the involvement of DCs in patients with GI cancers.

Effective pressure and treatment duration of high hydrostatic pressure to prepare melanoma vaccines

Current therapeutic methods for melanoma have numerous limitations, and thus the improvement of such treatment methods are essential. One possible option is the vaccination of autologous inactivated tumor cells. The primary indispensable principles of a cell-based melanoma vaccine include: i) Entire inactivation of melanoma cells; ii) retaining the immunogenicity of melanoma cells; and iii) adherence to laws and ethical guidelines. However, traditional methods for the production of the vaccine, such as ultrasonic, chemotherapeutics and freeze-thawing, have some juridical or therapeutic constraints. Therefore, the present study used high hydrostatic pressure (HHP) to inactivate malignant cells, and treated B16-F10 tumor cells with different pressures (≥50 MPa) and different durations (≥1 min). It was identified that tumor cells in vitro lost their proliferative ability, but retained their immunogenicity following treatment. Furthermore, the vaccination of the melanoma cells significantly suppressed their oncogenesis. Collectively, the present results suggest that HHP treatment may be an economically viable and effective measure to develop a melanoma vaccine, when pressure was ≥200 MPa and the treatment duration was ≥30 min.

Dendritic cells transduced with glioma-expressed antigen 2 recombinant adenovirus induces specific cytotoxic lymphocyte response and anti-tumor effect in mice

Introduction

Glioma is an aggressive common cancer with high mortality worldwide. Up to date, the effective medical therapeutical strategy is limited. Numerous previous studies have indicated that glioma-expressed antigen 2 (GLEA2) might be an attractive prognostic glioma biomarker.

Methods

In this experiment, dendritic cells (DCs) transduced with GLEA2 recombinant adenovirus were utilized to generate cytotoxic lymphocytes (CTLs) in vitro. Additionally, trimera mice were immunized with the transduced DCs to generate CTLs in vivo.

Results

The data demonstrated that GLEA2 transduced DCs could effectively generate specific CTL response against glioma without lysing autologous lymphocytes. Moreover, GLEA2 transduced DCs significantly attenuated the tumor growth and prolonged the life span of tumor bearing mice.

Conclusions

These findings suggested that DCs transduced with GLEA2 recombinant adenovirus could generate effective CTL mediated anti-tumor response, and might represent insight in glioma therapy.

Blockade of PD-L1 Enhances Cancer Immunotherapy by Regulating Dendritic Cell Maturation and Macrophage Polarization

The immuno-inhibitory checkpoint PD-L1, regulated by tumor cells and antigen-presenting cells (APCs), dampened the activation of T cells from the PD-1/PD-L1 axis. PD-L1-expressing APCs rather than tumor cells demonstrated the essential anti-tumor effects of anti-PD-L1 monotherapy in preclinical tumor models. Using the murine tumor model, we investigated whether anti-PD-L1 antibody increased the antigen-specific immune response and anti-tumor effects induced by the antigen-specific protein vaccine, as well as the possible mechanisms regarding activation of APCs. Anti-PD-L1 antibody combined with the PEK protein vaccine generated more potent E7-specific immunity (including the number and cytotoxic activity of E7-specific cytotoxic CD8⁺ T lymphocytes) and anti-tumor effects than protein vaccine alone. Anti-PD-L1 antibody enhanced the maturation of dendritic cells and the proportion of M1-like macrophages in tumor-draining lymph nodes and tumors in tumor-bearing mice treated with combinatorial therapy. PD-L1 blockade overturned the immunosuppressive status of the tumor microenvironment and then enhanced the E7 tumor-specific antigen-specific immunity and anti-tumor effects generated by an E7-specific protein vaccine through modulation of APCs in an E7-expressing small tumor model. Tumor-specific antigen (like HPV E7 antigen)-specific immunotherapy combined with APC-targeting modality by PD-L1 blockade has a high translational potential in E7-specific cancer therapy.

Conceptual Development of Immunotherapeutic Approaches to Gastrointestinal Cancer

Gastrointestinal (GI) cancer is one of the common causes of cancer-related death worldwide. Chemotherapy and/or immunotherapy are the current treatments, but some patients do not derive clinical benefits. Recently, studies from cancer molecular subtyping have revealed that tumor molecular biomarkers may predict the immunotherapeutic response of GI cancer patients. However, the therapeutic response of patients selected by the predictive biomarkers is suboptimal. The tumor immune-microenvironment apparently plays a key role in modulating these molecular-determinant predictive biomarkers. Therefore, an understanding of the development and recent advances in immunotherapeutic pharmacological intervention targeting tumor immune-microenvironments and their potential predictive biomarkers will be helpful to strengthen patient immunotherapeutic efficacy. The current review focuses on an understanding of how the host-microenvironment interactions and the predictive biomarkers can determine the efficacy of immune checkpoint inhibitors. The contribution of environmental pathogens and host immunity to GI cancer is summarized. A discussion regarding the clinical evidence of predictive biomarkers for clinical trial therapy design, current immunotherapeutic strategies, and the outcomes to GI cancer patients are highlighted. An understanding of the underlying mechanism can predict the immunotherapeutic efficacy and facilitate the future development of personalized therapeutic strategies targeting GI cancers.

The Interplay of Autophagy and Tumor Microenvironment in Colorectal Cancer-Ways of Enhancing Immunotherapy Action

Autophagy as a primary homeostatic and catabolic process is responsible for the degradation and recycling of proteins and cellular components. The mechanism of autophagy has a crucial role in several cellular functions and its dysregulation is associated with tumorigenesis, tumor–stroma interactions, and resistance to cancer therapy. A growing body of evidence suggests that autophagy is also a key regulator of the tumor microenvironment and cellular immune response in different types of cancer, including colorectal cancer (CRC). Furthermore, autophagy is responsible for initiating the immune response especially when it precedes cell death. However, the role of autophagy in CRC and the tumor microenvironment remains controversial. In this review, we identify the role of autophagy in tumor microenvironment regulation and the specific mechanism by which autophagy is implicated in immune responses during CRC tumorigenesis and the context of anticancer therapy.