Nanoparticle-Mediated In Situ Molecular Reprogramming of Immune Checkpoint Interactions for Cancer Immunotherapy.

Immune checkpoint blockade involves targeting immune regulatory molecules with antibodies. Preclinically, complex multiantibody regimes of both inhibitory and stimulatory targets are a promising candidate for the next generation of immunotherapy. However, in this setting, the antibody platform may be limited due to excessive toxicity caused by off target effects as a result of systemic administration. RNA can be used as an alternate to antibodies as it can both downregulate immunosuppressive checkpoints (siRNA) or induce expression of immunostimulatory checkpoints (mRNA). In this study, we demonstrate that the combination of both siRNA and mRNA in a single formulation can simultaneously knockdown and induce expression of immune checkpoint targets, thereby reprogramming the tumor microenvironment from immunosuppressive to immunostimulatory phenotype. To achieve this, RNA constructs were synthesized and formulated into stable nucleic acid lipid nanoparticles (SNALPs); the SNALPs produced were 140-150 nm in size with >80% loading efficiency. SNALPs could transfect macrophages and B16F10 cells in vitro resulting in 75% knockdown of inhibitory checkpoint (PDL1) expression and simultaneously express high levels of stimulatory checkpoint (OX40L) with minimal toxicity. Intratumoral treatment with the proposed formulation resulted in statistically reduced tumor growth, a greater density of CD4+ and CD8+ infiltrates in the tumor, and immune activation within tumor-draining lymph nodes. These data suggest that a single RNA-based formulation can successfully reprogram multiple immune checkpoint interactions on a cellular level. Such a candidate may be able to replace future immune checkpoint therapeutic regimes composed of both stimulatory- and inhibitory-receptor-targeting antibodies.

A natural protein based platform for the delivery of Temozolomide acid to glioma cells.

Glioblastoma is one of the most difficult to treat cancers with poor prognosis and survival of around one year from diagnosis. Effective treatments are desperately needed. This work aims to prepare temozolomide acid (TMZA) loaded albumin nanoparticles, for the first time, to target glioblastoma (GL261) and brain cancer stem cells (BL6). TMZA was loaded into human serum albumin nanoparticles (HSA NPs) using the desolvation method. A response surface 3-level factorial design was used to study the effect of different formulation parameters on the drug loading and particle size of NPs. The optimum conditions were found to be: 4 mg TMZA with 0.05% sodium cholate. This yielded NPs with particle size and drug loading of 111.7 nm and 5.5% respectively. The selected formula was found to have good shelf life and serum stability but with a relatively fast drug release pattern. The optimized NPs showed excellent cellular uptake with âˆ¼ 50 and 100% of cells were positive for NP uptake after 24 h incubation with both GL261 and BL6 glioblastoma cell lines, respectively. The selected formula showed high cytotoxicity with Ì´ 20% cell viability at 1 mM TMZA after 72 h incubation time. Finally, the fluorescently labelled NPs showed co-localization with the bioluminescent syngeneic BL6 intra-cranial tumour mouse model after intravenous administration.

Selection of Fluorescent, Bioluminescent, and Radioactive Tracers to Accurately Reflect Extracellular Vesicle Biodistribution in Vivo.

The ability to track extracellular vesicles (EVs) in vivo without influencing their biodistribution is a key requirement for their successful development as drug delivery vehicles and therapeutic agents. Here, we evaluated the effect of five different optical and nuclear tracers on the in vivo biodistribution of EVs. Expi293F EVs were labeled using either a noncovalent fluorescent dye DiR, or covalent modification with 111indium-DTPA, or bioengineered with fluorescent (mCherry) or bioluminescent (Firefly and NanoLuc luciferase) proteins fused to the EV marker, CD63. To focus specifically on the effect of the tracer, we compared EVs derived from the same cell source and administered systemically by the same route and at equal dose into tumor-bearing BALB/c mice. 111Indium and DiR were the most sensitive tracers for in vivo imaging of EVs, providing the most accurate quantification of vesicle biodistribution by ex vivo imaging of organs and analysis of tissue lysates. Specifically, NanoLuc fused to CD63 altered EV distribution, resulting in high accumulation in the lungs, demonstrating that genetic modification of EVs for tracking purposes may compromise their physiological biodistribution. Blood kinetic analysis revealed that EVs are rapidly cleared from the circulation with a half-life below 10 min. Our study demonstrates that radioactivity is the most accurate EV tracking approach for a complete quantitative biodistribution study including pharmacokinetic profiling. In conclusion, we provide a comprehensive comparison of fluorescent, bioluminescent, and radioactivity approaches, including dual labeling of EVs, to enable accurate spatiotemporal resolution of EV trafficking in mice, an essential step in developing EV therapeutics.

Exosome-mediated RNAi of PAK4 prolongs survival of pancreatic cancer mouse model after loco-regional treatment.

With a dismal survival rate, pancreatic cancer (PC) remains one of the most aggressive and devastating malignancies, predominantly due to the absence of a valid biomarker for diagnosis and limited therapeutic options for advanced diseases. Exosomes (Exo) as cell-derived vesicles, are widely used as natural nanocarriers for drug delivery. P21-activated kinase 4 (PAK4) is oncogenic when overexpressed, promoting cell survival, migration and anchorage-independent growth. Herein we validated PAK4 as a therapeutic target in an in vivo PC tumour mouse model using Exo-mediated RNAi following intra-tumoural administration. PC derived Exo were firstly isolated by ultracentrifugation on sucrose cushion and characterised for their surface marker expression, size, number, purity and morphology. SiRNA was encapsulated into Exo via electroporation and dual uptake of Exo and siRNA was investigated by flow cytometry and confocal microscopy. In vitro siPAK4 silencing in PC cells following uptake was assessed by flow cytometry, western blotting, and in vitro scratch assay. In vivo efficacy (tumour growth delay and mouse survival) of siPAK4 was evaluated in PC bearing NSG mouse model. Ex vivo tumours were examined using Haematoxylin and eosin (H&E) staining and immunohistochemistry. Results showed high quality PC-derived PANC-1 Exo were obtained. SiRNA was incorporated in Exo with 16.5% encapsulation efficiency. In vitro imaging confirmed Exo and siRNA co-localisation in cells. PAK4 knockdown was successful with 30 nM Exo-siPAK4 at 24 h post incubation in vitro. Intra-tumoural administration of Exo-siPAK4 (0.03 mg/kg siPAK4 and 6.1 × 1011 Exo, each dose, two doses) reduced PC tumour growth in vivo and enhanced mice survival (p < 0.001), with minimal toxicity observed compared to polyethylenimine (PEI) used as a commercial transfection reagent. H&E staining of tumours showed significant tissue apoptosis in siPAK4 treated groups. PAK4 knockdown prolongs survival of PC-bearing mice suggesting its potential as a new therapeutic target for PC. PANC-1 Exo demonstrated comparable efficacy but safer profile than PEI as in vivo RNAi transfection reagent.