Vx3-Functionalized Alumina Nanoparticles Assisted Enrichment of Ubiquitinated Proteins from Cancer Cells for Enhanced Cancer Immunotherapy

A simple and effective strategy was developed to enrich ubiquitinated proteins (UPs) from cancer cell lysate using the α-Al2O3 nanoparticles covalently linked with ubiquitin binding protein (Vx3) (denoted as α-Al2O3–Vx3) via a chemical linker. The functionalized α-Al2O3–Vx3 showed long-term stability and high efficiency for the enrichment of UPs from cancer cell lysates. Flow cytometry analysis results indicated dendritic cells (DCs) could more effectively phagocytize the covalently linked α-Al2O3–Vx3-UPs than the physical mixture of α-Al2O3 and Vx3-UPs (α-Al2O3/Vx3-UPs). Laser confocal microscopy images revealed that α-Al2O3–Vx3-UPs localized within the autophagosome of DCs, which then cross-presented α-Al2O3–Vx3-UPs to CD8+ T cells in an autophagosome-related cross-presentation pathway. Furthermore, α-Al2O3–Vx3-UPs enhanced more potent antitumor immune response and antitumor efficacy than α-Al2O3/cell lysate or α-Al2O3/Vx3-UPs. This work highlights the potential of using the Vx3 covalently linked α-Al2O3 as a simple and effective platform to enrich UPs from cancer cells for the development of highly efficient therapeutic cancer vaccines.