Nanoparticle preconditioning for enhanced thermal therapies in cancer.

Abstract

Nanoparticles show tremendous promise in the safe and effective delivery of molecular adjuvants to enhance local cancer therapy. One important form of local cancer treatment that suffers from local recurrence and distant metastases is thermal therapy. A new concept involving the use of nanoparticle-delivered adjuvants to `precondition' (alter the vascular and immunological biology) tumors to enhance their susceptibility to thermal therapy has been developed in our lab. Previous work has demonstrated nanoparticle preconditioning of thermal therapies (heat and cold) by a single systemic injection of PEG-coated gold nanoparticles tagged with a vascular targeting agent (TNF-alpha). In addition, mechanistic studies have shown that 4 hour pre-treatment with native TNF-alpha induced vascular preconditioning including the up regulation of inflammation (NF-kappaB) and apoptotic (caspase) pathways accompanied by an intense recruitment of neutrophils. Based on these findings, we hypothesized that vascular preconditioning of nanoparticle-delivered TNF-alpha is mediated by tumor endothelial (NF-kappaB) activation leading to leukocyte recruitment and vascular hyperpermeability resulting in a dramatic reduction in tumor blood perfusion. In this work, we used an in vivo model system of cryosurgery of human prostate cancer (LNCaP Pro 5) grown in nude male mice. We show that 4 hour pre-treatment with our nanoparticle system leads to a dramatic reduction in tumor blood perfusion with a simultaneous increase in tumor vascular hyperpermeability. However, we do not see increased NF-kappaB activation in tumor endothelial cells or increased leukocyte recruitment over the same timeframe implicating a different mechanism of preconditioning for nanoparticle-delivered TNF-alpha compared to native TNF-alpha. In vivo leukocyte depletion and NF-kappaB inhibition experiments support these findings by demonstrating that the enhancement of cryosurgical injury is independent of leukocyte recruitment and NF-kappaB activation. We also demonstrate that nanoparticle preconditioning can be used to enhance high temperature thermal therapy in the LNCaP tumor model. Finally, nanoparticle preconditioning was tested in combination with radiofrequency ablation and cryosurgery in a translational model of rabbit kidney tumors. The current work builds on our understanding of the mechanisms of nanoparticle preconditioning for enhancement of thermal therapy which could lead to the identification of novel adjuvants to be used in combination with TNF-alpha for improved clinical outcomes.