Immune profiling of human tumors identifies CD73 as a combinatorial target in glioblastoma

Abstract

Immune checkpoint therapy (ICT) with anti-CTLA-4 and anti-PD-1/PD-L1 has revolutionized the treatment of many solid tumors. However, the clinical efficacy of ICT is limited to a subset of patients with specific tumor types 1,2. Multiple clinical trials with combinatorial immune checkpoint strategies are ongoing, however, the mechanistic rationale for tumor specific targeting of immune checkpoints remains elusive. To garner insight into tumor specific immunomodulatory targets, we analyzed tumors (N=94) representing 5 different cancer types, including those that respond relatively well to ICT and those that do not, such as glioblastoma (GBM), prostate cancer (PCa) and colorectal cancer (CRC). Through mass cytometry and single cell RNA-sequencing, we identified a unique population of CD73 hi macrophages in GBM that persists after anti-PD-1 treatment. To test if targeting CD73 would be important for a successful combination strategy in GBM, we performed reverse translational studies using CD73 −/− mice. We found that the absence of CD73 improved survival in a murine model of GBM treated with anti-CTLA-4 and anti-PD-1. Our data identified CD73 as a specific immunotherapeutic target to improve anti-tumor immune responses to ICT in GBM, and demonstrate that comprehensive human and reverse translational studies can be used for rational design of combinatorial immune checkpoint strategies.

Single-Cell Approaches to Profile the Response to Immune Checkpoint Inhibitors

“…In general, in the majority of these tumors, immune cells were mostly T cells, whereas myeloid cells, B cells and NK cells were found at lower frequencies (108)(109)(110)(111). Only GMB had higher levels of CD68+ myeloid cells if compared to T cells (88).…”

“…However, as already described, mRNA and protein do not always correlate, meaning that the information on protein expression delivered by high-parameter flow-cytometry is also central. However, to date, a few studies reported the combination of scRNA-seq and CyTOF to profile the tumor immune microenvironment (88,89).…”

“…Single cell profiles not only revealed that human tumors comprise subpopulations of genetically different diverse malignant cells, but also that a profusion of different cell types from the surrounding tissues and the immune system, each with a precise role in pathogenicity, is present within the TME (106,107). The immune components of the tumor microenvironment in different kind of malignancies, including non-small cell lung cancer (NSCLC), clear cell RCC (ccRCC), breast cancer (BC), HCC, glioblastoma multiforme (GMB), microsatellite instability-stable CRC have been recently annotated and finely characterized (88,(108)(109)(110)(111). In general, in the majority of these tumors, immune cells were mostly T cells, whereas myeloid cells, B cells and NK cells were found at lower frequencies (108)(109)(110)(111).…”

“…Through mass cytometry and scRNA-seq, in GMB a unique subset of macrophages expressing high levels of CD73 able to persist after anti-PD-1 therapy was observed (88). Notably, a number of reports have shown that CD73 can induce immunosuppression in GMB (157,158).…”

Defining the transcriptional landscape of infiltrating immune cells in human and mouse bladder cancer

“…Identifiable species differences included higher LAG3 levels in human mouse T-NK cells. Interestingly, the immune suppression molecule Nt5e-NT5E (CD73) [16,17] was expressed higher in mouse than human NK-T cells and higher in human than mouse B cells. Other genes that were differentially expressed between species were identified in pDC cells, mast cells and neutrophils (Fig.…”