Title: Design and Application of Cationic Nanocarriers to Inhibit Chemotherapy-Induced Breast Cancer Metastasis and Inflammation
Description: Chemotherapy persists as one of the mainstays of breast cancer treatment, particularly for triple-negative breast cancer which currently has no targeted treatment methods. While chemotherapy is beneficial for killing the malignant tumor cells, it leads to the release of damage-associated molecular patterns into the tumor microenvironment. Damage-associated molecular patterns are a contributing factor to cancer-related inflammation which can potentiate metastatic spread through several mechanisms such as the development of tumor microenvironments at metastastic sites. These damage-associated molecular patterns include nucleic acids, nucleic acid-associated lipids and vesicles, cytokines, and proteins such as high mobility group protein B1. Polyamidoamine (PAMAM) is a biodegradable, water-soluble dendrimer polymer with the ability to possess different charges and sizes depending on its terminal branches and degree of branching (i.e. generation number), respectively. Amine-terminated PAMAM-NH2 is positively charged and can bind to circulating DNA and RNA.

Since most DAMP molecules are negatively charged, I hypothesized that a polycation such as PAMAM-NH2 would be an efficient nanomaterial to remove pathogenic NA DAMPs generated by chemotherapy. Building on this dendrimer, we synthesized modified cationic PAMAM-generation 3 derivatives with an aim to balance toxicity with NA-binding affinity and capacity to encapsulate chemodrugs. Our results found that these soluble and nanoparticle PAMAM materials can bind to both cell-free DNA and RNA released as a result of treating triple-negative breast cancer cells with chemotherapy drugs such as doxorubicin and paclitaxel. These PAMAM-G3 materials are termed as nucleic acid binding polymers and nucleic-acid binding polymeric nanoparticles.My thesis dissertation explores the anti-metastatic effects of nucleic-acid binding polymeric nanoparticles delivering the chemotherapy drug paclitaxel using in-vitro and in-vivo models. Two murine metastatic breast cancer models served as the basis for assessing the effects of conventional paclitaxel delivery compared to paclitaxel delivery from within PAMAM nucleic-acid binding polymeric nanoparticles with respect to primary tumor growth, extent of lung metastasis, and the systemic inflammatory response reflected in murine serum.

Compared to treatment with unencapsulated paclitaxel, delivery of paclitaxel within the PAMAM nucleic-acid binding polymeric nanoparticles resulted in significantly decreased serum cell-free DNA levels, decreased inflammatory cytokines, and a lower degree of lung metastasis in the mice. The decrease in the degree of lung metastasis in mice receiving paclitaxel within the PAMAM nanoparticles was confirmed by assessing the photon flux signal of 4T1-luciferase breast cancer cells invading the murine lungs in both in-vivo and ex-vivo imaging and by using a machine learning method to quantify the degree of metastasis in H&E- stained sections of the lungs. The ability to mitigate the phenomenon of chemotherapy-induced cancer metastasis while effectively delivering the chemotherapy to the tumor microenvironment could help improve the outcomes of patients being treated with chemotherapy. This work developed a therapeutic cationic PAMAM nanocarrier-based strategy to inhibit paclitaxel-induced metastasis by scavenging cell-free nucleic acids and mitigating cell-free nucleic acid-induced inflammation.