Zinc nanoparticles from oral supplements accumulate in renal tumours and stimulate antitumour immune responses.

A successful therapeutic outcome in the treatment of solid tumours requires efficient intratumoural drug accumulation and retention. Here we demonstrate that zinc gluconate in oral supplements assembles with plasma proteins to form ZnO nanoparticles that selectively accumulate into papillary Caki-2 renal tumours and promote the recruitment of dendritic cells and cytotoxic CD8 T cells to tumour tissues. Renal tumour targeting is mediated by the preferential binding of zinc ions to metallothionein-1X proteins, which are constitutively overexpressed in Caki-2 renal tumour cells. This binding event further upregulates intracellular metallothionein-1X expression to induce additional nanoparticle binding and retention. In both tumour animal models and human renal tumour samples, we show that ZnO nanoparticles actively cross the vascular wall to achieve high intratumoural accumulation. We further explore this feature of ZnO nanoparticles for the delivery of chemotherapeutics to mouse and rabbit cancer models. Our findings demonstrate that ZnO nanoparticles derived from supplements can serve as a multifunctional drug delivery and cancer immunotherapy platform.