Anticancer nanocage platforms for combined immunotherapy designed to harness immune checkpoints and deliver anticancer drugs.

The interaction of programmed cell death 1 ligand 1 (PD-L1) with its receptor, programmed cell death 1 (PD-1), inhibits T cell responses. Monoclonal antibodies that block this interaction have been shown effective as immunotherapy. However, only a subset of cancers exhibits a durable response to PD-1/PD-L1 blockade. Moreover, antibody-based immune checkpoint blockade is costly and is occasionally accompanied by systemic side effects. To overcome these limitations of antibody-based immune checkpoint blockade, an immune checkpoint-blocking ferritin nanocage displaying 24 PD-L1 binding peptides (PD-L1pep1) on its surface was designed and constructed. These ferritin nanocages displaying PD-L1pep1 (PpNF) specifically bind to PD-L1 expressed on cancer cells or to purified PD-L1 with a ~30 nM binding affinity. The addition of PpNF to co-cultures of T cells and cancer cells inhibited PD-1/PD-L1 interactions and restored T cell activities. In a mouse model of syngeneic colon cancer, PpNF specifically targeted tumors and showed antitumor activity. Moreover, PpNF nanocages encapsulating the chemotherapeutic drug doxorubicin had more potent antitumor activity than a monoclonal antibody against PD-L1. These results demonstrate that ferritin nanocages displaying surface PD-L1pep1 can be efficiently applied for immunotherapy, especially when encapsulating small chemotherapeutic drugs. These nanocages may have promise as an immunotherapeutic nanomedicine against various solid tumors.

Designed ferritin nanocages displaying trimeric TRAIL and tumor-targeting peptides confer superior anti-tumor efficacy.

TRAIL is considered a promising target for cancer therapy because it mediates activation of the extrinsic apoptosis pathway in a tumor-specific manner by binding to and trimerizing its functional receptors, DR4 or DR5. Although recombinant human TRAIL has shown high potency and specificity for killing cancer cells in preclinical studies, it has failed in multiple clinical trials for several reasons, including a very short half-life mainly caused by instability of the monomeric form of TRAIL and rapid renal clearance of the off-targeted TRAIL. To overcome such obstacles, we developed a TRAIL-active trimer nanocage (TRAIL-ATNC) that presents the TRAIL ligand in its trimer-like conformation by connecting it to a triple helix sequence that links to the threefold axis of the ferritin nanocage. We also ligated the tumor-targeting peptide, IL4rP, to TRAIL-ATNC to enhance tumor targeting. The developed TRAIL-ATNCIL4rP showed enhanced agonistic activity compared with monomeric TRAIL. The in vivo serum half-life of TRAIL-ATNCIL4rP was ~ 16-times longer than that of native TRAIL. As a consequence of these properties, TRAIL-ATNCIL4rP exhibited efficacy as an anti-tumor agent in vivo against xenograft breast cancer as well as orthotopic pancreatic cancer models, highlighting the promise of this system for development as novel therapeutics against cancer.

The Protein Trio RPK1-CaM4-RbohF Mediates Transient Superoxide Production to Trigger Age-Dependent Cell Death in Arabidopsis.

Reactive oxygen species (ROS) are inevitable by-products of aerobic metabolic processes, causing non-specific oxidative damage and also acting as second messengers. Superoxide is a short-lived ROS that functions in various cellular responses, including aging and cell death. However, it is unclear as to how superoxide brings about age-dependent cell death and senescence. Here, we show that the accumulation and signaling of superoxide are mediated by three Arabidopsis proteins-RPK1, CaM4, and RbohF-which trigger subsequent cellular events leading to age-dependent cell death. We demonstrate that the NADPH oxidase RbohF is responsible for RPK1-mediated transient accumulation of superoxide, SIRK kinase induction, and cell death, all of which are positively regulated by CaM4. RPK1 physically interacts with and phosphorylates CaM4, which, in turn, interacts with RbohF. Overall, we demonstrate how the protein trio governs the superoxide accumulation and signaling at the cell surface to control senescence and cell death.