CCR4 Blockade Depletes Regulatory T Cells and Prolongs Survival in a Canine Model of Bladder Cancer

Regulatory T cells in tumor microenvironment: new mechanisms, potential therapeutic strategies and future prospects

Regulatory T cells (Tregs) characterized by the expression of the master transcription factor forkhead box protein p3 (Foxp3) suppress anticancer immunity, thereby hindering protective immunosurveillance of tumours and hampering effective antitumour immune responses in tumour-bearing hosts, constitute a current research hotspot in the field. However, Tregs are also essential for the maintenance of the immune tolerance of the body and share many molecular signalling pathways with conventional T cells, including cytotoxic T cells, the primary mediators of tumour immunity. Hence, the inability to specifically target and neutralize Tregs in the tumour microenvironment without globally compromising self-tolerance poses a significant challenge. Here, we review recent advances in characterizing tumour-infiltrating Tregs with a focus on the functional roles of costimulatory and inhibitory receptors in Tregs, evaluate their potential as clinical targets, and systematically summarize their roles in potential treatment strategies. Also, we propose modalities to integrate our increasing knowledge on Tregs phenotype and function for the rational design of checkpoint inhibitor-based combination therapies. Finally, we propose possible treatment strategies that can be used to develop Treg-targeted therapies.

Suppression of CXCL-1 Could Restore Necroptotic Pathway in Chronic Lymphocytic Leukemia

Purpose

To clarify the role of different cytokines and selenite in the defective necroptotic pathway of chronic lymphocytic leukemia (CLL).

Patients and Methods

We randomly collected the peripheral blood samples of 11 untreated CLL patients and 10 healthy volunteers, and then separated B lymphocytes from peripheral blood. Then, real-time polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA) and Western Blot were performed to detect the expression of different cytokines, including CXC-motif chemokine ligand 1 (CXCL-1). Finally, we used flow cytometry to analyze the percentage of surviving cells to figure out whether CLL cells or normal B lymphocytes underwent necroptosis.

Results

1) The high expression of CXCL-1 was seen in CLL cells compared with normal B lymphocytes (p = 0.0001, adjusted p =0.0012); 2) The downregulation of CXCL-1 was shown in normal B lymphocytes after induction by TNF-α and z-VAD; 3) CLL cells could restore necroptosis induced by TNF-α and z-VAD after knockdown of CXCL-1; 4) The transcriptional and translational expression of LEF-1 were downregulated after the knockdown of CXCL-1 in CLL cells; 5. 3.2μM selenite could help CLL cells restore necroptosis (p = 0.0102) and inhibit the transcriptional and translational expression of CXCL-1.

Conclusion

CXCL-1 played an important role in the defective necroptosis of CLL cells and regulated the expression of LEF-1. Selenite could inhibit the expression of CXCL-1 and help CLL cells restore necroptosis together with TNF-α and z-VAD. Selenite might be the potential medication of CLL in the future.

Foxp3+ Regulatory T Cells Associated With CCL17/CCR4 Expression in Carcinomas of Dogs

Regulatory T cells (Tregs) can be targeted in cancer immunotherapy. A previous study has shown that the chemokine CCL17 and the receptor CCR4 play a role in Treg recruitment in canine urothelial carcinoma. Here, we describe the association of tumor-infiltrating Tregs with CCL17/CCR4 expression in dogs with other carcinomas. In this study, we investigated 23 dogs with mammary carcinoma, 14 dogs with oral squamous cell carcinoma, 16 dogs with pulmonary adenocarcinoma, and 8 healthy control dogs. Immunohistochemistry showed that Foxp3⁺ Tregs and CCR4⁺ cells were increased in the tumor tissues of mammary carcinoma, squamous cell carcinoma, and pulmonary adenocarcinoma, when compared with the healthy tissues. The number of CCR4⁺ cells was associated with that of Foxp3⁺ Tregs. Double immunofluorescence labeling confirmed that most tumor-infiltrating Foxp3⁺ Tregs expressed CCR4. In vitro, canine carcinoma cell lines expressed CCL17 mRNA. Quantitative RT-PCR (reverse transcriptase-polymerase chain reaction) showed that CCL17 mRNA expression in canine carcinomas was increased approximately 10- to 25-fold relative to that of healthy tissues. These results suggest that the CCL17/CCR4 axis may drive Treg recruitment in a variety of canine carcinomas. CCR4 blockade may be a potential therapeutic option for tumor eradication through Treg depletion.

A Role for Dogs in Advancing Cancer Immunotherapy Research

While rodent cancer models are essential for early proof-of-concept and mechanistic studies for immune therapies, these models have limitations with regards to predicting the ultimate effectiveness of new immunotherapies in humans. As a unique spontaneous, large animal model of cancer, the value of conducting studies in pet dogs with cancer has been increasingly recognized by the research community. This review will therefore summarize key aspects of the dog cancer immunotherapy model and the role that these studies may play in the overall immunotherapy drug research effort. We will focus on cancer types and settings in which the dog model is most likely to impact clinical immuno-oncology research and drug development. Immunological reagent availability is discussed, along with some unique opportunities and challenges associated with the dog immunotherapy model. Overall it is hoped that this review will increase awareness of the dog cancer immunotherapy model and stimulate additional collaborative studies to benefit both man and man's best friend.

Immunosurveillance and Immunoediting of Lung Cancer: Current Perspectives and Challenges

The immune system plays a dual role in tumor evolution-it can identify and control nascent tumor cells in a process called immunosurveillance and can promote tumor progression through immunosuppression via various mechanisms. Thus, bilateral host-protective and tumor-promoting actions of immunity are integrated as cancer immunoediting. In this decade, immune checkpoint inhibitors, specifically programmed cell death 1 (PD-1) pathway inhibitors, have changed the treatment paradigm of advanced non-small cell lung cancer (NSCLC). These agents are approved for the treatment of patients with NSCLC and demonstrate impressive clinical activity and durable responses in some patients. However, for many NSCLC patients, the efficacy of immune checkpoint inhibitors is limited. To optimize the full utility of the immune system for eradicating cancer, a broader understanding of cancer immunosurveillance and immunoediting is essential. In this review, we discuss the fundamental knowledge of the phenomena and provide an overview of the next-generation immunotherapies in the pipeline.

Cancer Immunotherapies Targeting Tumor-Associated Regulatory T Cells

Tumor-associated regulatory T cells (Tregs) are important effectors in the tumor microenvironment (TME), acting as accomplices in the promotion of tumor progression. Currently, the importance of removing the immunosuppressive activity in the TME has received its due attention, and Tregs have been focused on. The cytokine-receptor axes are among the essential signaling pathways in immunocytes, and tumor-associated Tregs are no exception. Therefore, manipulating cytokine-receptor pathways may be a promising effective strategy for treating various malignancies. Here, we summarize the classification, immunosuppressive mechanisms, existing immunotherapies, and potential biomarkers related to tumor-infiltrating Tregs to guide the development of effective cancer immunotherapies.

The multifaceted immune regulation of bladder cancer

Bladder cancer is an important public health concern owing to its prevalence, high recurrence risk and treatment failures. Maintaining the equilibrium between prompt and effective immunity and an excessive and protracted immune response is critical for successful immune defence. This delicate balance is ensured by intrinsic or extrinsic immunoregulatory mechanisms. Intrinsic control of immune cell activation is mediated by stimulatory and inhibitory receptors expressed on the effector cell itself, whereas extrinsic control is mediated via other immune cells by cell-cell contact and/or secretion of inhibitory factors. Tumours can exacerbate these immunosuppressive pathways, fostering a tolerant microenvironment. These mechanisms have previously been poorly described in urothelial carcinoma, but a growing body of evidence highlights the key role of immune regulation in bladder cancer. This process includes immune checkpoints (mostly programmed cell death 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1)), as well as regulatory T cells, myeloid-derived suppressor cells, tumour-associated macrophages and type 2 innate and adaptive lymphocytes. For each component, quantitative and qualitative alterations, clinical relevance and potential targeting strategies are currently being explored. An improved understanding of immune regulation pathways in bladder cancer development, recurrence and progression will help in the design of novel diagnostic and prognostic tools as well as treatments.