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

Novel immunotherapy in metastatic renal cell carcinoma

Despite the rapid development of therapeutic modalities for metastatic renal cell carcinoma (mRCC) over the past decade to include a number of targeted antiangiogenic therapies and traditional immunotherapy, such as high-dose interleukin-2 and interferon-α, mRCC continues to be associated with poor prognosis. Currently, several novel immunotherapy agents, such as cancer vaccines, adoptive cell therapy, and checkpoint inhibitors, such as programmed cell death-1 (PD-1 present on T cells), one of its ligands (PD-L1 present on antigen-presenting cells and tumor cells), and cytotoxic T-lymphocyte-associated protein-4 pathways, are being studied in mRCC and are showing promise as important steps in the management of this disease. This review summarizes the current landscape of standard and emerging immune therapeutics and other modalities for mRCC.

Immunotherapeutic strategies for the treatment of renal cell carcinoma: Where will we go?

INTRODUCTION

Historically, renal cell carcinoma (RCC) is considered a chemotherapy-resistant tumor. The cornerstone of systemic therapy included mammalian target of rapamycin (mTOR) inhibitors, endothelial growth factor receptor (VEGFR) and tyrosine kinase inhibitors (TKIs). Currently, a new era is enteres with promising immunotherapeutic treatments, which are becoming commercially available. Areas covered: We provide a comprehensive review using PubMed and ClinicalTrials.gov about the following immunotherapies in RCC: i) vaccine therapy, ii) adoptive T Cell Transfer and CAR T cells, iii) nonspecific immunotherapy - IL-2 (new formulations), iv) Checkpoint inhibitors, v) other checkpoint-molecules. We will also discuss their mechanism of action and toxicity, the importance of developing new patient selection algorithms (immunoprofiling, guidelines updates) and new biomarkers such as PD-1 expression. Expert commentary: Immunotherapy shows promise, and the current tools used in clinical practice, including guidelines, staging-classification and algorithms should be revised and adapted to the new immunotherapeutic drugs. Although immunotherapy in RCC show promising results, more research is needed in parallel to discover biomarkers that enable the prediction of a treatment response and therefore lead to better patient selection.

Human anti-CAIX antibodies mediate immune cell inhibition of renal cell carcinoma in vitro and in a humanized mouse model in vivo

Background

Carbonic anhydrase (CA) IX is a surface-expressed protein that is upregulated by the hypoxia inducible factor (HIF) and represents a prototypic tumor-associated antigen that is overexpressed on renal cell carcinoma (RCC). Therapeutic approaches targeting CAIX have focused on the development of CAIX inhibitors and specific immunotherapies including monoclonal antibodies (mAbs). However, current in vivo mouse models used to characterize the anti-tumor properties of fully human anti-CAIX mAbs have significant limitations since the role of human effector cells in tumor cell killing in vivo is not directly evaluated.

Methods

The role of human anti-CAIX mAbs on CAIX⁺ RCC tumor cell killing by immunocytes or complement was tested in vitro by antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP) as well as on CAIX⁺ RCC cellular motility, wound healing, migration and proliferation. The in vivo therapeutic activity mediated by anti-CAIX mAbs was determined by using a novel orthotopic RCC xenograft humanized animal model and analyzed by histology and FACS staining.

Results

Our studies demonstrate the capacity of human anti-CAIX mAbs that inhibit CA enzymatic activity to result in immune-mediated killing of RCC, including nature killer (NK) cell-mediated ADCC, CDC, and macrophage-mediated ADCP. The killing activity correlated positively with the level of CAIX expression on RCC tumor cell lines. In addition, Fc engineering of anti-CAIX mAbs was shown to enhance the ADCC activity against RCC. We also demonstrate that these anti-CAIX mAbs inhibit migration of RCC cells in vitro. Finally, through the implementation of a novel orthotopic RCC model utilizing allogeneic human peripheral blood mononuclear cells in NOD/SCID/IL2Rγ^−/− mice, we show that anti-CAIX mAbs are capable of mediating human immune response in vivo including tumor infiltration of NK cells and activation of T cells, resulting in inhibition of CAIX⁺ tumor growth.

Conclusions

Our findings demonstrate that these novel human anti-CAIX mAbs have therapeutic potential in the unmet medical need of targeted killing of HIF-driven CAIX⁺RCC. The orthotopic tumor xenografted humanized mouse provides an improved model to evaluate the in vivo anti-tumor capabilities of fully human mAbs for RCC therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0384-3) contains supplementary material, which is available to authorized users.

Checkpoint modulation--A new way to direct the immune system against renal cell carcinoma

The introduction of targeted therapies like the tyrosine kinase (TKI) and mammalian target of rapamycin (mTOR) inhibitors has improved patients' survival in general. Nevertheless the prognosis remains limited. Therapies with a new mode of action are urgently warranted, especially those who would provoke long-term responders or long-lasting complete remissions as observed with unspecific immunotherapy with the cytokines interleukin-2 and interferon-α. In the recent years a deeper understanding of the underlying immunology of T cell activation led to the development of checkpoint inhibitors, which are mainly monocloncal antibodies and which enhances the presence of the co-stimulatory signals needed for T cell activation or priming. This review discusses the clinical data and ongoing studies available for the inhibition of the PD-1 (CD279) and CTLA-4 (CD152) axis in mRCC. In addition, potential future immunological targets are discussed. This approach of T-cell activation or re-activation by immunological checkpoint inhibition holds the inherent promise to directly affect the tumor cell and thereby to potentially cure a subset of patients with mRCC.

Regression of established renal cell carcinoma in nude mice using lentivirus-transduced human T cells expressing a human anti-CAIX chimeric antigen receptor

Carbonic anhydrase IX (CAIX) is a tumor-associated antigen and marker of hypoxia that is overexpressed on > 90% of clear-cell type renal cell carcinoma (RCC) but not on neighboring normal kidney tissue. Here, we report on the construction of two chimeric antigen receptors (CARs) that utilize a carbonic anhydrase (CA) domain mapped, human single chain antibody (scFv G36) as a targeting moiety but differ in their capacity to provide costimulatory signaling for optimal T cell proliferation and tumor cell killing. The resulting anti-CAIX CARs were expressed on human primary T cells via lentivirus transduction. CAR-transduced T cells (CART cells) expressing second-generation G36-CD28-TCRζ exhibited more potent in vitro antitumor effects on CAIX(+) RCC cells than first-generation G36-CD8-TCRζ including cytotoxicity, cytokine secretion, proliferation, and clonal expansion. Adoptive G36-CD28-TCRζ CART cell therapy combined with high-dose interleukin (IL)-2 injection also lead to superior regression of established RCC in nude mice with evidence of tumor cell apoptosis and tissue necrosis. These results suggest that the fully human G36-CD28-TCRζ CARs should provide substantial improvements over first-generation mouse anti-CAIX CARs in clinical use through reduced human anti-mouse antibody responses against the targeting scFv and administration of lower doses of T cells during CART cell therapy of CAIX(+) RCC.