Project Summary Currently, most nanotechnology cancer therapies focus on the treatment of primary tumors, but it is important to leverage the potential of nanomedicine to combat cancer spread at each stage of the metastatic process. Lung metastasis is a highly aggressive, complex, and heterogeneous disease. There is no effective treatment for metastatic lung tumors and chemotherapy is the only option to prolong patients’ clinical prognosis. Alternative strategies, including targeted therapy and immunotherapy have been proposed, but they failed to successfully treat metastatic lesions. There is an urgent need to accelerate progress toward curing lung metastases and reduce patients’ mortality. Our goal is to develop a new therapeutic approach that carries more drugs to the metastatic lung tumors and retains on-site to release a broad-spectrum antitumor medication. In this project, we propose to use peptide-based nanofiber (pNFP6) with preferential lung-targeting properties to overcome the barrier of selective drug delivery to metastases. The pNFP6 is innovative as multiple nanofibers can rearrange into a large interfibril network to prolong the local retention and offer a long-term treatment. The nanofiber technology will be combined with ionizing radiation therapy to enhance the drug post-delivery antitumor efficacy. Our central hypothesis is that the combinatorial therapy will cooperatively and synergistically inhibit the disease progression leading to an effective treatment of lung metastases. For proof-of-principle studies, we will use pNFP6 to carry and deliver doxorobucin (Dox), a standard cytotoxic agent and radiosensitizer. The nanofibers will favor the drug accumulation and retention on-site while radiotherapy will promote the overall anticancer effect through direct tumor cell killing and radiation-mediated immunogenicity. The spatiotemporal-controlled drug release will be essential to ensure the therapeutic success. To establish the potential of this antimetastatic multiplexed approach, two specific aims will be pursued: (1) evaluate the local drug release and its impact on the therapeutic efficacy; and (2) define the therapeutic and survival benefit of Dox-pNFP6 when combined with radiation therapy. To achieve Aim 1, we will synthesize a panel of Dox-loaded pNFP6 analogues using different cleavable linkers sensitive to tumor microenvironment stimuli to release the drug. We will study the in vivo drug delivery, release, and tumoral uptake using Light Sheet Fluorescence Microscopy and MALDI-imaging. and identify the optimal release mechanisms in response to metastatic lung tumors. To complete Aim 2, we will assess the therapeutic efficacy (tumor inhibition and survival benefit) and toxicity profile of Dox-pNFP6 combined with radiation therapy in several animal models bearing metastatic lung tumors. The treatment outcomes will be compared to free Dox and Doxil, the FDA-approved liposomal formulation of Dox. We will also investigate the mo...