Project Summary Triple-negative breast cancer (TNBC) has the highest patient death rate of all breast cancer subtypes. Several molecular targets have been identified for breast cancer treatment, but currently, there is no approved, broadly applicable targeted therapy for TNBC. Through 10 years of research, we found that elongation factor 2-kinase (EF2K) expression is a critical driver of TNBC tumorigenesis and progression. We also found that microRNA-22 (miR-22) expression is broadly repressed in TNBC patients, and is inversely correlated with EF2K expression. Further analysis revealed that miR-22 suppresses tumors by specifically binding to EF2K, which inhibits EF2K expression and reduces tumor growth in multiple TNBC models. Considering the clinical significance and potential therapeutic value of EF2K in TNBC, we have thus developed an AXL receptor-targeted AXL aptamer-coated SLNP-miR-22 nanoparticle system that can specifically deliver miR-22 to TNBC tumors in vivo (but does not lead to miR-22 accumulation in normal tissues). On the basis of this preliminary work, we hypothesize that EF2K is an effective therapeutic target in TNBC, and that targeting EF2K using our AXL-aptamer-SLNP-miR-22 nanotherapeutics can provide significant therapeutic efficacy in TNBC treatment. However, understandably, this therapeutic system is complex, and it has been difficult to further understand the underlying biological and physical processes that significantly impact treatment outcome, and to identify the optimal doses and dosing schedules for maximizing treatment efficacy. Therefore, in this project, we propose to overcome this challenge by integrating biological experiments with mathematical modeling based on the underlying biological and physical mechanisms that are involved in cancer invasion, drug penetration, and drug-cancer cell interactions in the EF2K-targeted miR-22 nanotherapeutics for TNBC treatment. Our hypothesis will be tested by achieving the following two specific aims: 1) experimental testing of the EF2K-targeted miR-22 nanotherapy (Aim 1), and 2) mathematical modeling (Aim 2). In Aim 1, we will focus on characterizing and determining the in vivo therapeutic efficacy of EF2K-targeted miR-22 mediated therapies in orthotopic mouse models. In Aim 2, we will focus on developing, testing, and validating a mathematical model of EF2K-targeted, miR-22 based nanotherapy, using a logically integrated statistical and multiscale mechanistic modeling approach. Experimental data from Aim 1 will be supplied to Aim 2 for developing and validating the mathematical model, and experiments in Aim 1 will be guided by discoveries obtained from computational investigations in Aim 2. Through this iteration-based feedback approach, the mathematical model will be used to predict and determine the effects of various parameters, including siRNA dose and dosing schedules, on tumor response to EF2K-targeted miR-22 mediated therapies (with or without chemotherapy), and to de...