CD45+ cells from human bladder cancer specimens

Background

NK cells are important innate defenders against tumours and have unique abilities to recognize and eliminate cancer cells. Responses to targeted antibody therapeutics are typically limited in bladder tumours, and the functional and immunosuppressive phenotypes of NK cells in this disease are largely unknown.

Methods

Single cell RNA sequencing (scRNAseq) and high-dimensional flow cytometry were used to investigate the phenotype of intratumoural NK cells compared to circulating in patients with bladder cancer.

Findings

NK cells residing within bladder tumours had reduced expression of FcγRIIIa/CD16, the critical receptor for NK-cell-mediated ADCC, on both a transcriptional and protein level. Transcriptional signatures of TGF-β-signalling, a pleiotropic cytokine with known immunosuppressive effects on NK cells, were upregulated in tumour NK cells compared to the blood. In concert, a high TGF-β signature expression also correlated with worse survival and CD16 downregulation. We directly validated this TGF-β mediated CD16 downregulation on NK cells in vitro and it was accompanied by a transition to ILC1-like NK cells. We also uncovered a high proportion of tumour infiltrating-Treg cells, and in vivo studies show that NK cells delivered in the presence of accompanying immune cells have a greater reduction of CD16 compared to NK cells delivered alone.

Interpretation

Thus, this study highlights how TGF-β rich bladder cancers could inhibit NK cell ADCC by downregulating CD16, whereby Treg cells could be a major limiter of NK cell effector functions in these tumours.