Combination strategies to enhance the potency of monocyte-derived dendritic cell-based cancer vaccines

Dendritic cells (DCs) are potent inducers of adaptive immunity and their clinical use in cancer vaccine formulations remains an area of active translational and clinical investigation. Although cancer vaccines applied as monotherapies have had a modest history of clinical success, there is great enthusiasm for novel therapeutic strategies combining DC-based cancer vaccines with agents that 'normalize' immune function in the tumor microenvironment (TME). Broadly, these combination vaccines are designed to antagonize/remove immunosuppressive networks within the TME that serve to limit the antitumor action of vaccine-induced T cells and/or to condition the TME to facilitate the recruitment and optimal function and durability of vaccine-induced T cells. Such combination regimens are expected to dramatically enhance the clinical potency of DC-based cancer vaccine platforms.

Synergistic antitumor responses by combined GITR activation and sunitinib in metastatic renal cell carcinoma

Sunitinib, a multitargeted tyrosine kinase inhibitor, is the frontline therapy for renal and gastrointestinal cancers. In view of its well-documented proapoptotic and immunoadjuvant properties, we speculate that combination of Sunitinib and immunotherapy would provide a synergistic antitumor effect. Here, we report that a remarkably synergistic antitumor responses elicited by the combined treatment of Sunitinib and an agonistic antibody against glucocorticoid-induced TNFR related protein (GITR) in a model of metastatic renal cell carcinoma. Sunitinib significantly increased the infiltration, activation, and proliferation and/or cytotoxicity of CD8(+) T cells and NK cells in liver metastatic foci when combined with the anti (α)-GITR agonist, which was associated with treatment-induced prominent upregulation of Th1-biased immune genes in the livers from mice receiving combined therapy versus single treatment. Sunitinib/α-GITR treatment also markedly promoted the maturation, activation and cytokine production of liver-resident macrophages and DCs compared with that achieved by α-GITR or Sunitinib treatment alone in mice. Cell depletion experiments demonstrated that CD8(+) T cells, NK cells and macrophage infiltrating liver metastatic foci all contribute to the antitumor effect induced by combined treatment. Furthermore, mechanistic investigation revealed that Sunitinib treatment reprograms tumor-associated macrophages toward classically activated or "M1" polarization upon GITR stimulation and consequently mounts an antitumor CD8(+) T and NK cell response via inhibiting STAT3 activity. Thus, our findings provide a proof of concept that Sunitinib can synergize with α-GITR treatment to remodel the tumor immune microenvironment to trigger regressions of an established metastatic cancer.

Trial Watch: Therapeutic vaccines in metastatic renal cell carcinoma

Despite the renaissance of cancer immunotherapy, no novel immunotherapy has been approved for the treatment of renal cell cancer (RCC) since the availability of recombinant cytokines (interleukin-2, interferon-α). All vaccine trials have failed to meet their endpoints although they have highlighted potential predictive biomarkers (e.g., pre-existing immune response, hematological parameters, tumor burden). Recent advances in immunomodulatory therapies have prompted the study of combination treatments targeting the tumor immunosuppressive microenvironment consisting of regulatory T-cells (Treg), myeloid suppressor cells, and cytokines. Approaches under investigation are use of inhibitors to curb the overexpression of immune checkpoint ligands by tumor cells (e.g., anti-CTLA-4, anti-PD-1/PD-L1) and exploiting the immunomodulatory effects of anti-angiogenic agents that are the current standard of metastatic RCC care. Phase III trials are focusing on the possible synergy between therapeutic vaccines (e.g., IMA-901 and AGS-003) and anti-angiogenic agents.

Immunotherapeutic strategies for the treatment of renal cell carcinoma: where are we now?

Immunotherapy with cytokines was the first effective treatment in metastatic renal cell carcinoma (mRCC). Long-term responders and complete remissions were observed, but efficacy in the overall population was limited with the consequence that targeted agents replaced cytokines. The discovery of tumor associated antigens as direct targets paved the way from theses rather unspecific to specific immunotherapeutic strategies, which are discussed in this review. Autologous or dendritic cell (DC) based tumor vaccination with vitespen or AGS-003, adoptive T-cell transfer and synthetic peptide vaccination with IMA901 are new and promising approaches. Besides that the more passive strategies of antibody dependent cytotoxicity with the VEGF antibody bevacizumab or the carbonic anhydrase IX antibody girentuximab are discussed. Immunomodulation by cyclophosphamide, tyrosine kinase inhibitors or nivolumab, which targets the PD-1 axis, further promote T-cell activation and combinatory strategies with these agents are outlined.

Targeted therapy in renal cell carcinoma: moving from molecular agents to specific immunotherapy

Non-specific immunotherapy has been for a long time a standard treatment option for patients with metastatic renal cell carcinoma but was redeemed by specific targeted molecular therapies, namely the VEGF and mTOR inhibitors. After moving treatment for mRCC to specific molecular agents with a well-defined mode of action, immunotherapy still needs this further development to increase its accuracy. Nowadays, an evolution from a rather non-specific cytokine treatment to sophisticated targeted approaches in specific immunotherapy led to a re-launch of immunotherapy in clinical studies. Recent steps in the development of immunotherapy strategies are discussed in this review with a special focus on peptide vaccination which aims at a tumor targeting by specific T lymphocytes. In addition, different combinatory strategies with immunomodulating agents like cyclophosphamide or sunitinib are outlined, and the effects of immune checkpoint modulators as anti-CTLA-4 or PD-1 antibodies are discussed.

Immunological heterogeneity of the RCC microenvironment: do targeted therapies influence immune response?

The introduction of targeted agents has substantially improved treatment of metastatic clear-cell renal cell carcinoma (RCC). However, complete responses are rare and therapy is not curative. Moreover, information on the latest generation of potent and selective vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKI) suggests that a plateau has been reached in terms of efficacy. Recent data reveal that targeted agents are involved in modulating immune responses in RCC. In addition, current research adds to our understanding of how RCC escapes an effective anti-tumor response with the potential to modulate these processes by drug development. This review provides specific insight into targeted therapy induced changes in the immunological microenvironment of RCC, summarizes the available evidence, and discusses potential therapeutic implications.