Enhanced In Vivo Tumor Detection by Active Tumor Cell Targeting Using Multiple Tumor Receptor-Binding Peptides Presented on Genetically Engineered Human Ferritin Nanoparticles.

Human ferritin heavy-chain nanoparticle (hFTH) is genetically engineered to present tumor receptor-binding peptides (affibody and/or RGD-derived cyclic peptides, named 4CRGD here) on its surface. The affibody and 4CRGD specifically and strongly binds to human epidermal growth factor receptor I (EGFR) and human integrin αvß3, respectively, which are overexpressed on various tumor cells. Through in vitro culture of EGFR-overexpressing adenocarcinoma (MDA-MB-468) and integrin-overexpressing glioblastoma cells (U87MG), it is clarified that specific interactions between receptors on tumor cells and receptor-binding peptides on engineered hFTH is critical in active tumor cell targeting. After labeling with the near-infrared fluorescence dye (Cy5.5) and intravenouse injection into MDA-MB-468 or U87MG tumor-bearing mice, the recombinant hFTHs presenting either peptide or both of affibody and 4CRGD are successfully delivered to and retained in the tumor for a prolonged period of time. In particular, the recombinant hFTH presenting both affibody and 4CRGD notably enhances in vivo detection of U87MG tumors that express heterogeneous receptors, integrin and EGFR, compared to the other recombinant hFTHs presenting either affibody or 4CRGD only. Like affibody and 4CRGD used in this study, other multiple tumor receptor-binding peptides can be also genetically introduced to the hFTH surface for actively targeting of in vivo tumors with heterogenous receptors.

Engineered Human Ferritin Nanoparticles for Direct Delivery of Tumor Antigens to Lymph Node and Cancer Immunotherapy.

Efficient delivery of tumor-specific antigens (TSAs) to lymph nodes (LNs) is essential to eliciting robust immune response for cancer immunotherapy but still remains unsolved. Herein, we evaluated the direct LN-targeting performance of four different protein nanoparticles with different size, shape, and origin [Escherichia coli DNA binding protein (DPS), Thermoplasma acidophilum proteasome (PTS), hepatitis B virus capsid (HBVC), and human ferritin heavy chain (hFTN)] in live mice, using an optical fluorescence imaging system. Based on the imaging results, hFTN that shows rapid LN targeting and prolonged retention in LNs was chosen as a carrier of the model TSA [red fluorescence protein (RFP)], and the flexible surface architecture of hFTN was engineered to densely present RFPs on the hFTN surface through genetic modification of subunit protein of hFTN. The RFP-modified hFTN rapidly targeted LNs, sufficiently exposed RFPs to LN immune cells during prolonged period of retention in LNs, induced strong RFP-specific cytotoxic CD8+ T cell response, and notably inhibited RFP-expressing melanoma tumor growth in live mice. This suggests that the strategy using protein nanoparticles as both TSA-carrying scaffold and anti-cancer vaccine holds promise for clinically effective immunotherapy of cancer.

Engineered protein nanoparticles for in vivo tumor detection.

Two different protein nanoparticles that are totally different in shape and surface structure, i.e. Escherichia coli DNA-binding protein (eDPS) (spherical, 10 nm) and Thermoplasma acidophilum proteasome (tPTS) (cylindrical, 12 × 15 nm) were engineered for in vivo optical tumor detection: arginine-glycine-aspartic acid (RGD) peptide (CDCRGDCFC) was genetically inserted to the surface of each protein nanoparticle, and also near-infrared fluorescence dye was chemically linked to the surface lysine residues. The specific affinity of RGD for integrin (αvß3) facilitated the uptake of RGD-presenting protein nanoparticles by integrin-expressing tumor cells, and also the protein nanoparticles neither adversely affected cell viability nor induced cell damage. After intravenously injected to tumor-bearing mice, all the protein nanoparticles successfully reached tumor with negligible renal clearance, and then the surface RGD peptides caused more prolonged retention of protein nanoparticles in tumor and accordingly higher fluorescence intensity of tumor image. In particular, the fluorescence of tumor image was more intensive with tPTS than eDPS, which is due presumably to longer in vivo half-life and circulation of tPTS that originates from thermophilic and acidophilic bacterium. Although eDPS and tPTS were used as proof-of-concept in this study, it seems that other protein nanoparticles with different size, shape, and surface structure can be applied to effective in vivo tumor detection.

Non-invasive optical imaging of cathepsin B with activatable fluorogenic nanoprobes in various metastatic models.

An increasing number of treatments of metastases rely on diagnostics and imaging these days. The facts that the activity of cathepsin B (CB) is markedly linked to the metastatic process and that CB is found highly expressed in the pericellular regions in this process make CB an attractive target for diagnosing metastases. We have developed a CB-sensitive nanoprobe (CB-CNP) consisting of self-quenched CB-sensitive fluorogenic peptide probes conjugated onto the surface of tumor-targeting glycol chitosan nanoparticles (CNPs). The freshly prepared CB-CNP formed a spherical nanoparticle structure (280 nm in diameter) and the fluorescence intensity of CB-CNP was strongly quenched in physiological condition. However, self-quenched CB-CNP boosted strong fluorescence signals in the presence of CB, not of cathepsin l or cathepsin d, due to the CB-specific cleavage of self-quenched peptide probes. Importantly, the intravenously injected CB-CNP demonstrated the potential to discriminate metastases in vivo in three metastatic mouse models, including 4T1-luc2 liver metastases, RFP-B16F10 lung metastases and HT1080 peritoneal metastases. Indeed, Western blot analysis confirmed that the CB expression of metastases had increased compared to normal organ in these metastatic mouse models. CB-CNPs may be useful for depicting metastases through non-invasive CB molecular imaging.