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.