A Wholly Protein-based Self-assembly Nanoplatform for TNBC-specific Combination Therapy

Abstract Triple-negative breast cancer (TNBC) is a unique type of breast cancer that does not express or overexpress estrogen receptor (ER), progesterone receptor (PR), and HER2. During the past several decades, the standard care of TNBC remains the highly toxic chemotherapy with little progress in more effective treatments. To address the urgent unmet need to develop targeted therapies specific for TNBC, we developed a totally protein-based nanoplatform called ProNano that is composed of two recombinant proteins, including the first an elastin-like polypeptide (ELP) nanocore that displays multiple calmodulin-binding short peptides on the surface, and the second a recombinant calmodulin protein genetically fused with a highly stable and modular protein domain possessing either tumor homing or therapeutic features. The docking of the ELP nanocore with a TNBC- targeting module together with a functional module with therapeutic feature results in bifunctional ProNanos that can be used for tumor-homing delivery of therapeutic agents for the combination therapy for TNBC. Three specific aims will be pursued in this project. The first specific aim is to develop a ProNano platform that allows tunable targeting of TNBC cells based on their surface antigen expression profiles. The second specific aim is to develop a bifunctional ProNano platform that allows tumor-specific blockade of the aberrant Wnt signaling for the treatment of TNBC. The third specific aim is to develop a bifunctional ProNano platform that allows tumor- specific inhibition of the ENPP1-catalyzed hydrolysis of extracellular cGAMP for combination immunotherapy of TNBC. The bifunctional ProNano platforms developed in this project have several major advantages over conventional nanoplatforms, including all protein components each can be precisely and genetically engineered, oriented and self-assembled introduction of both tumor homing and/or therapeutic moieties at desired ratios without need of any chemical conjugation, and use of highly stable and easily expressed modular polypeptides with no or low immunogenicity. Although we focus on the targeted treatment for TNBC, the ProNano platforms developed in this project can be easily adapted to address other cancer types simply by changing the tumor targeting module.