Iron oxide nanoparticles inhibit tumor progression and suppress lung metastases in mouse models of breast cancer [RNA-seq]
Systemic exposure to starch-coated iron oxide nanoparticles (IONPs) can stimulate antitumor T cell responses, even when little IONP is retained within the tumor. Here, we demonstrate in mouse models of metastatic breast cancer that IONPs can alter the host immune landscape leading to systemic immune-mediated disease suppression. We report that a single intravenous injection of IONPs can inhibit primary tumor growth, suppress metastases, and extend survival. Gene expression analysis revealed activation of Toll-like receptor (TLR) pathways involving signaling via Toll/Interleukin-1 Receptor domain-containing adaptor-inducing IFN-ß (TRIF), a TLR pathway adaptor protein. Requisite participation of TRIF in suppressing tumor progression was demonstrated with histopathologic evidence of upregulated IFN-regulatory factor 3 (IRF3), a downstream protein, and confirmed in a TRIF knockout syngeneic mouse model of metastatic breast cancer. Neither starch-coated polystyrene nanoparticles lacking iron, nor iron-containing dextran-coated parenteral iron replacement agent induced significant antitumor effects suggesting a dependence on the type of IONP formulation. Analysis of multiple independent clinical databases support a hypothesis that upregulation of TLR3 and IRF3 correlates with increased overall survival among breast cancer patients. Taken together, these data support a compelling rationale to re-examine IONP formulations as harboring anti-cancer immune (nano)adjuvant properties to generate therapeutic benefit without requiring uptake by cancer cells. Overall design: HuHER2 transgenic mice that developed palpable primary mammary tumors were assigned randomly into one of two groups (n = 3/group) to receive either PBS or BP (5 mg Fe/mouse). Mice were sacrificed 7 days after treatment and tumors, lungs, livers, spleens, lymph nodes, and bone marrows were collected. All nanoparticle-containing organs collected from BP treated mice were divided into two equal sections except for lungs (no detectable nanoparticle accumulation). One section was processed for RNA isolation from whole organ. The other tissue/organ section was further processed for magnetic sorting. These were digested to provide single cells as described before28,38 and nanoparticle associated cells were separated magnetically to obtain the nanoparticle-associated fraction (BP-NA). RNA was isolated from BP-NA cells from each organ and tumor and used for sequencing. For Nanostring analysis, HuHER2 transgenic tumor bearing mice were treated with PBS or BP (5 mg Fe) on the day of tumor detection (n = 12/group). Three mice from each group were sacrificed on day 1, 3, 7, or 31 and primary tumors collected for RNA isolation and gene expression analysis by Nanostring using the pan-immune cell marker panel.