CD8+ T cells maintain killing of MHC-I-negative tumor cells through the NKG2D-NKG2DL axis.

The accepted paradigm for both cellular and anti-tumor immunity relies upon tumor cell killing by CD8+ T cells recognizing cognate antigens presented in the context of target cell major histocompatibility complex (MHC) class I (MHC-I) molecules. Likewise, a classically described mechanism of tumor immune escape is tumor MHC-I downregulation. Here, we report that CD8+ T cells maintain the capacity to kill tumor cells that are entirely devoid of MHC-I expression. This capacity proves to be dependent instead on interactions between T cell natural killer group 2D (NKG2D) and tumor NKG2D ligands (NKG2DLs), the latter of which are highly expressed on MHC-loss variants. Necessarily, tumor cell killing in these instances is antigen independent, although prior T cell antigen-specific activation is required and can be furnished by myeloid cells or even neighboring MHC-replete tumor cells. In this manner, adaptive priming can beget innate killing. These mechanisms are active in vivo in mice as well as in vitro in human tumor systems and are obviated by NKG2D knockout or blockade. These studies challenge the long-advanced notion that downregulation of MHC-I is a viable means of tumor immune escape and instead identify the NKG2D-NKG2DL axis as a therapeutic target for enhancing T cell-dependent anti-tumor immunity against MHC-loss variants.

4-1BB Agonism Averts TIL Exhaustion and Licenses PD-1 Blockade in Glioblastoma and Other Intracranial Cancers.

PURPOSE: The success of checkpoint blockade against glioblastoma (GBM) has been disappointing. Anti-PD-1 strategies may be hampered by severe T-cell exhaustion. We sought to develop a strategy that might license new efficacy for checkpoint blockade in GBM. EXPERIMENTAL DESIGN: We characterized 4-1BB expression in tumor-infiltrating lymphocytes (TIL) from human GBM. We implanted murine tumor models including glioma (CT2A), melanoma (B16), breast (E0771), and lung carcinomas intracranially and subcutaneously, characterized 4-1BB expression, and tested checkpoint blockade strategies in vivo. RESULTS: Our data reveal that 4-1BB is frequently present on nonexhausted CD8+ TILs in human and murine GBM. In murine gliomas, 4-1BB agonism and PD-1 blockade demonstrate a synergistic survival benefit in a CD8+ T-cell-dependent manner. The combination decreases TIL exhaustion and improves TIL functionality. This strategy proves most successful against intracranial CT2A gliomas. Efficacy in all instances correlates with the levels of 4-1BB expression on CD8+ TILs, rather than with histology or with intracranial versus subcutaneous tumor location. Proffering 4-1BB expression to T cells licenses combination 4-1BB agonism and PD-1 blockade in models where TIL 4-1BB levels had previously been low and the treatment ineffective. CONCLUSIONS: Although poor T-cell activation and severe T-cell exhaustion appear to be limiting factors for checkpoint blockade in GBM, 4-1BB agonism obviates these limitations and produces long-term survival when combined with anti-PD-1 therapy. Furthermore, this combination therapy is limited by TIL 4-1BB expression, but not by the intracranial compartment, and therefore may be particularly well-suited to GBM.

Targeting PD-L1 Initiates Effective Antitumor Immunity in a Murine Model of Cushing Disease.

PURPOSE: Although pituitary adenoma is classified as benign, Cushing disease is associated with significant morbidity due to the numerous sequelae of elevated cortisol levels. Successful therapy for Cushing disease remains elusive due to high rates of treatment-refractory recurrence. The frequent emergence of lymphocytic hypophysitis following checkpoint blockade for other cancers, as well as the expression of PD-L1 on pituitary adenomas, suggest a role for immunotherapy. EXPERIMENTAL DESIGN: This study confirms PD-L1 expression on functioning pituitary adenomas and is the first to evaluate the efficacy of checkpoint blockade (anti-PD-L1) therapy in a preclinical model of Cushing disease. RESULTS: Herein, treatment with anti-PD-L1 was successful in reducing adrenocorticotropic hormone plasma levels, decreasing tumor growth, and increasing survival in our model. Furthermore, tumor-infiltrating T cells demonstrated a pattern of checkpoint expression similar to other checkpoint blockade-susceptible tumors. CONCLUSIONS: This suggests that immunotherapy, particularly blockade of the PD1/PD-L1 axis, may be a novel therapeutic option for refractory Cushing disease. Clinical investigation is encouraged.

T-cell Dysfunction in Glioblastoma: Applying a New Framework.

A functional, replete T-cell repertoire is an integral component to adequate immune surveillance and to the initiation and maintenance of productive antitumor immune responses. Glioblastoma (GBM), however, is particularly adept at sabotaging antitumor immunity, eliciting severe T-cell dysfunction that is both qualitative and quantitative. Understanding and countering such dysfunction are among the keys to harnessing the otherwise stark potential of anticancer immune-based therapies. Although T-cell dysfunction in GBM has been long described, newer immunologic frameworks now exist for reclassifying T-cell deficits in a manner that better permits their study and reversal. Herein, we divide and discuss the various T-cell deficits elicited by GBM within the context of the five relevant categories: senescence, tolerance, anergy, exhaustion, and ignorance. Categorization is appropriately made according to the molecular bases of dysfunction. Likewise, we review the mechanisms by which GBM elicits each mode of T-cell dysfunction and discuss the emerging immunotherapeutic strategies designed to overcome them. Clin Cancer Res; 24(16); 3792-802. ©2018 AACR.

Transcriptome analysis of human diabetic kidney disease.

OBJECTIVE: Diabetic kidney disease (DKD) is the single leading cause of kidney failure in the U.S., for which a cure has not yet been found. The aim of our study was to provide an unbiased catalog of gene-expression changes in human diabetic kidney biopsy samples. RESEARCH DESIGN AND METHODS: Affymetrix expression arrays were used to identify differentially regulated transcripts in 44 microdissected human kidney samples. DKD samples were significant for their racial diversity and decreased glomerular filtration rate (~25-35 mL/min). Stringent statistical analysis, using the Benjamini-Hochberg corrected two-tailed t test, was used to identify differentially expressed transcripts in control and diseased glomeruli and tubuli. Two different web-based algorithms were used to define differentially regulated pathways. RESULTS: We identified 1,700 differentially expressed probesets in DKD glomeruli and 1,831 in diabetic tubuli, and 330 probesets were commonly differentially expressed in both compartments. Pathway analysis highlighted the regulation of Ras homolog gene family member A, Cdc42, integrin, integrin-linked kinase, and vascular endothelial growth factor signaling in DKD glomeruli. The tubulointerstitial compartment showed strong enrichment for inflammation-related pathways. The canonical complement signaling pathway was determined to be statistically differentially regulated in both DKD glomeruli and tubuli and was associated with increased glomerulosclerosis even in a different set of DKD samples. CONCLUSIONS: Our studies have cataloged gene-expression regulation and identified multiple novel genes and pathways that may play a role in the pathogenesis of DKD or could serve as biomarkers.