Abstract SY20-02: Theranostic nanoparticles for targeted therapy of pancreatic and triple-negative breast cancers
Authors: Yang Lily 
Published: June 2012

The major challenges in clinical oncology are the selective delivery of large amounts of therapeutic agents into tumor cells, accurate evaluation of the drug delivery, and timely assessment of the therapeutic response. Theranostic nanoparticles with the abilities to target tumors, carry therapeutic agents, and produce contrasts or signals for tumor imaging offer an exciting means to address these challenges and have a great promise for effective cancer treatment. We have developed a multifunctional theranostic magnetic iron oxide nanoparticle (IONP) platform that utilizes receptor-targeted IONPs to carry single or multiple therapeutic agents for drug delivery and optical and magnetic resonance imaging (MRI) for monitoring the delivery and response. To overcome physical and intrinsic barriers that reduce efficiency of drug delivery and confer drug resistance in human cancers, our theranostic IONPs are targeted to urokinase plasminogen activator receptor (uPAR), thereby taking advantage of high levels of uPAR expression in tumor cells, angiogenic endothelial cells, and active tumor stromal cells. These IONPs allow the drug to overcome the physical barrier in stroma-rich tumors, such as pancreatic cancer and triple-negative breast cancer (TNBC), by serving as carrier vehicles for passage through the tumor endothelial cell layer and stromal fibroblasts, thereby increasing the efficiency of delivery into tumors but not into normal tissues. Moreover, these uPAR-targeted IONPs can destroy tumor blood vessels, producing an antiangiogenesis effect that enhances treatment efficacy. To make the IONPs suitable for repeat administrations, a recombinant amino terminal fragment (ATF) of the receptor binding domain of uPA, a high affinity natural ligand for uPAR, was produced in a bacterial expression system to minimize the immune response. ATF peptides were conjugated to amphiphilic polymer-coated IONPs to produce the receptor-targeted MRI contrast nanoparticles. The ATF can also be labeled with a new near-infrared dye (NIR-830) developed by our group prior conjugation to generate uPAR-targeted IONPs with dual optical and MR imaging modalities. Based on the surface functionalization of the IONPs and chemical properties of drug molecules, we developed approaches for encapsulating hydrophobic drugs or conjugating hydrophilic drugs to the IONPs, resulting in theranostic IONPs which carry chemotherapy drugs, such as doxorubicin (ATF-IONP-Dox) and gemcitabine (ATF-IONP-Gem). After delivery into tumor cells, the drug molecules can be released efficiently from the nanoparticles using pH-sensitive and/or lysosomal enzyme-sensitive drug release mechanisms. Targeted delivery, intracellular drug release, and the cytotoxic effect have been demonstrated in breast and pancreatic cancer cell lines as well as in an endothelial cell line.

The efficacy of ATF-theranostic IONPs and the ability of MRI to monitor drug delivery and response were examined in orthotopic animal tumor models, including a triple-negative mouse mammary tumor model, a basal type human breast ductal carcinoma in situ xenograft model, and a human pancreatic cancer xenograft model. We found that systemic administration of ATF-IONP-Dox significantly inhibited the growth of orthotopic breast and pancreatic tumors in these animal models. Additionally, preoperative treatment of primary tumors with ATF-IONP-Dox significantly decreased the growth of primary tumors and further inhibited local recurrence and lung metastasis in 4T1 mouse mammary tumor model. Using our established MRI methods, the efficiency of intratumoral drug delivery and changes in tumor sizes and tissue contrasts can be detected by T1- and T2-weighted MRI using a clinical field strength MRI scanner in the tumor models. Histological analysis showed that the uPAR-targeted theranostic IONPs are selectively accumulated in primary breast tumor, and primary and peritoneal metastatic pancreatic tumor lesions. Theranostic IONP-mediated doxorubicin delivery reduced systemic toxicity since pathological changes in the liver and heart tissues and serological abnormalities were detected in mice treated with free doxorubicin at a dose of 10 mg/Kg of body weight but not in mice after treatment with an equivalent dose of ATF-IONP-Dox.

The effect of ATF-IONP-Gem on the growth of orthotopic human pancreatic cancer was also examined in an orthotopic human pancreatic cancer xenograft model. ATF-IONP-Gem showed significant tumor growth inhibition in the tumor-bearing mice that received systemic delivery of ATF-IONP-Gem containing 2 mg/kg of body weight of gemcitabine. However, there was no significant tumor growth inhibition in the mice that received an equivalent dose of free gemcitabine or nontargeted IONP-Gem. The presence of IONP-drug in the tumor lesion can be detected as bright signals using an ultra-short TE MRI scan method. At present, we are developing uPAR-targeted IONPs carrying multiple therapeutic agents in a single IONP to further enhance the efficacy of the treatment.

Our theranostic IONPs have the potential to significantly impact cancer treatment in neoadjuvant therapy of TNBC or locally advanced pancreatic cancer. Preoperative neoadjuvant chemotherapy is usually administered to patients with TNBC to reduce the size of the primary tumor and to treat locally advanced tumors and micrometastatic lesions in order to lower the incidence of local and distant recurrence. The unique differential response to chemotherapy within the TNBC patient population makes it crucial to assess early tumor responses to the therapy and to ensure the most effective chemotherapies while avoiding unnecessary toxicity. About 40% of pancreatic cancer patients are diagnosed with unresectable locally advanced disease at presentation because their tumors have directly invaded into adjacent normal structures and blood vessels. It is feasible to treat these patients with the targeted theranostic IONPs to reduce the burden of the primary tumor and peritoneal metastatic lesions so that the patients can be candidates for potentially curative surgical resection. Additionally, NIR optical signal produced from the dual imaging theranostic IONPs allows optical image-guided surgery to detect and completely remove residual tumors that are resistant to drug treatment. In summary, uPAR-targeted theranostic IONPs developed by our research team have great potentials for the development of an integrated treatment-imaging protocol for pancreatic cancer and TNBC. Such a protocol can significantly improve the survival rate of cancer patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr SY20-02. doi:10.1158/1538-7445.AM2011-SY20-02