Harnessing dendritic cells for tumor antigen presentation

Icaritin inhibits PD-L1 expression by Targeting Protein IκB Kinase α

Icaritin, a small molecule currently being investigated in phase III clinical trials in China (NCT03236636 and NCT03236649) for treatment of advanced hepatocellular carcinoma (HCC), is a prenylflavonoid derivative obtained from the Epimedium genus. Previously, it was found that Icaritin decreased the expression of PD-L1, but its direct molecular targets and the underlying mechanisms have not been identified. In this study, we report the identification of IKK-α as the protein target of Icaritin by biotin-based affinity binding assay. The further mutagenesis assay has provided evidence that C46 and C178 in IKK-α were essential amino acids for Icaritin binding to IKK-α, revealing the binding sites of Icaritin to IKK-α for the first time. Functionally, Icaritin inhibited the NF-κB signalling pathway by blocking IKK complex formation, which led to decreased nuclear translocation of NF-κB p65, and subsequent downregulation of PD-L1 expression in a dose-dependent manner. More importantly, PD-L1-positive patients exhibited longer overall survival upon Icaritin therapy. Finally, Icaritin in combination with checkpoints antibodies, such as α-PD-1, has demonstrated much better efficacy than any single therapy in animal models. This is the first report that anticancer effects of Icaritin are mediated, at least in part, by impairing functions of IKK-α.

Activated B lymphocytes and tumor cell lysate as an effective cellular cancer vaccine

Cancer vaccines that utilize patient antigen-presenting cells to fight their own tumors have shown exciting promise in many preclinical studies, but have proven quite challenging to translate to clinical feasibility. Dendritic cells have typically been the cell of choice for such vaccine platforms, due to their ability to endocytose antigens nonspecifically, and their expression of multiple surface molecules that enhance antigen presentation. However, dendritic cells are present in low numbers in human peripheral blood and must be matured in culture before use in vaccines. Mature B lymphocytes, in contrast, are relatively abundant in peripheral blood, and can be quickly activated and expanded in overnight cultures. We devised an optimal stimulation cocktail that engages the B cell antigen receptor, CD40, TLR4 and TLR7, to activate B cells to present antigens from lysates of the recipient's tumor cells, precluding the need for known tumor antigens. This B cell vaccine (Bvac) improved overall survival from B16F1 melanoma challenge, as well as reduced tumor size and increased time to tumor appearance. Bvac upregulated B cell antigen presentation molecules, stimulated activation of both CD4⁺ and CD8⁺ T cells, and induced T cell migration. Bvac provides an alternative cellular vaccine strategy that has considerable practical advantages for translation to clinical settings.

My journey from tyrosine phosphorylation inhibitors to targeted immune therapy as strategies to combat cancer

Since the 1980s there has been a drive toward personalized targeted therapy for cancer. "Targeted cancer therapy" originally focused on inhibiting essential tumor survival factors, primarily protein tyrosine kinases. The complexity and rapid mutability of tumors, however, enable them to develop resistance to tyrosine kinase inhibitors (TKIs), even when these are multitargeted or applied in combination. This has led to the development of targeted cancer immunotherapy, to enhance immune surveillance against the tumor. In this paper, we provide a personal view of the development of targeted therapy, from TKIs to targeted immunotherapy.

Strategies to Genetically Modulate Dendritic Cells to Potentiate Anti-Tumor Responses in Hematologic Malignancies

Dendritic cell (DC) vaccination has been investigated as a potential strategy to target hematologic malignancies, while generating sustained immunological responses to control potential future relapse. Nonetheless, few clinical trials have shown robust long-term efficacy. It has been suggested that a combination of surmountable shortcomings, such as selection of utilized DC subsets, DC loading and maturation strategies, as well as tumor-induced immunosuppression may be targeted to maximize anti-tumor responses of DC vaccines. Generation of DC from CD34+ hematopoietic stem and progenitor cells (HSPCs) may provide potential in patients undergoing allogeneic HSPC transplantations for hematologic malignancies. CD34+ HSPC from the graft can be genetically modified to optimize antigen presentation and to provide sufficient T cell stimulatory signals. We here describe beneficial (gene)-modifications that can be implemented in various processes in T cell activation by DC, among which major histocompatibility complex (MHC) class I and MHC class II presentation, DC maturation and migration, cross-presentation, co-stimulation, and immunosuppression to improve anti-tumor responses.

Antigenically Modified Human Pluripotent Stem Cells Generate Antigen-Presenting Dendritic Cells

Human pluripotent stem cells (hPSCs) provide a promising platform to produce dendritic cell (DC) vaccine. To streamline the production process, we investigated a unique antigen-loading strategy that suits this novel platform. Specifically, we stably modified hPSCs using tumour antigen genes in the form of a full-length tumour antigen gene or an artificial tumour antigen epitope-coding minigene. Such antigenically modified hPSCs were able to differentiate into tumour antigen-presenting DCs. Without conventional antigen-loading, DCs derived from the minigene-modified hPSCs were ready to prime a tumour antigen-specific T cell response and further expand these specific T cells in restimulation processes. These expanded tumour antigen-specific T cells were potent effectors with central memory or effector memory phenotype. Thus, we demonstrated that immunocompetent tumour antigen-loaded DCs can be directly generated from antigenically modified hPSCs. Using such strategy, we can completely eliminate the conventional antigen-loading step and significantly simplify the production of DC vaccine from hPSCs.

Dendritic Cell Therapy in an Allogeneic-Hematopoietic Cell Transplantation Setting: An Effective Strategy toward Better Disease Control?

Hematopoietic cell transplantation (HCT) is a last treatment resort and only potentially curative treatment option for several hematological malignancies resistant to chemotherapy. The induction of profound immune regulation after allogeneic HCT is imperative to prevent graft-versus-host reactions and, at the same time, allow protective immune responses against pathogens and against tumor cells. Dendritic cells (DCs) are highly specialized antigen-presenting cells that are essential in regulating this balance and are of major interest as a tool to modulate immune responses in the complex and challenging phase of immune reconstitution early after allo-HCT. This review focuses on the use of DC vaccination to prevent cancer relapses early after allo-HCT. It describes the role of host and donor-DCs, various vaccination strategies, different DC subsets, antigen loading, DC maturation/activation, and injection sites and dose. At last, clinical trials using DC vaccination post-allo-HCT and the future perspectives of DC vaccination in combination with other cancer immunotherapies are discussed.

Various ways to improve whole cancer cell vaccines

Immunotherapy based on whole cancer cell vaccines is regarded as a promising avenue for cancer treatment. However, limited efficacy in the first human clinical trials calls for more optimized whole cancer cell vaccines and better patient selection. It is suggested that whole cancer cell vaccines consist preferably of immunogenically killed autologous cancer stem cells associated with dendritic cells. Adjuvants should stimulate both immune effector cells and memory cells, which could be achieved through their correct dosage and timing of administration. There are indications that whole cancer cell vaccination is less effective in patients who are immunocompromised, who have specific genetic defects in their immune or cancer cells, as well as in patients in an advanced cancer stage. However, such patients form the bulk of enrolled patients in clinical trials, prohibiting an objective evaluation of the true potential of whole cancer cell immunotherapy. Each key point will be discussed.

Dendritic cells and their role in tumor immunosurveillance

Dendritic cells (DCs) comprise a heterogeneous population of cells that play a key role in initiating, directing and regulating adaptive immune responses, including those critically involved in tumor immunosurveillance. As a riposte to the central role of DCs in the generation of antitumor immune responses, tumors have developed various mechanisms which impair the immunostimulatory functions of DCs or even instruct them to actively contribute to tumor growth and progression. In the first part of this review we discuss general aspects of DC biology, including their origin, subtypes, immature and mature states, and functional plasticity which ensures a delicate balance between active immune response and immune tolerance. In the second part of the review we discuss the complex interactions between DCs and the tumor microenvironment, and point out the challenges faced by DCs during the recognition of tumor Ags. We also discuss the role of DCs in tumor angiogenesis and vasculogenesis.