Optimization of CAR-Bacteria for Oral Cancer

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ABSTRACT The goal of this project is to explore the feasibility of generating Chimeric Antigen Receptors (CARs) expressed by bacteria. Instead of using T cells, we propose to explore the idea and use of bacteria to mediate the targeted destruction of cancer cells. In addition, we explore the possibility that we could target CAR-bacteria to specific major histocompatibility complex (MHC)-neopeptide complexes (pMHC) on tumor cells. We call these engineered bacteria cells CAR-bacteria. Current CAR-expressing T cells provide durable responses but have three main limitations: specificity, toxicity, and feasibility. This study will address all three concerns. In this proposal, we target engineered bacterial lysis to head and neck or cervical cancer cells expressing HLA-A2-E7, a known pMHC on tumor cells infected by human papilloma virus (HPV). The targeting enables anti-tumor protein production only when a predefined population density of bacteria is reached. This method should dramatically reduce bacterial colony size and greatly lowers/prevents systemic toxicities. The approach has the potential to be a therapeutic in HPV-positive oral cancer as it could be administered and controlled as a bacterial mouthwash. This project combines two innovations leveraging a Synthetically-Evolved Nanobody (SEN) library proven capable of selectively binding MHC-peptide complexes and combining this specific cancer cell targeting with synchronized circuit lysis to create CAR-bacteria. Our proposed studies provide proof-of-concept that (1) CARs can be produced that recognize pMHC, (2) CAR-bacteria localization and colonization can be controlled by tumor expression of certain pMHC and (3) CAR-bacteria have therapeutic activity against tumor cells that express specific pMHC. We accomplish these proof-of-concept studies via the following two objectives: (1) Optimize binding and specificity of CAR-bacteria to HLA-A2-E7 and (2) Check efficacy of CAR-bacteria in an animal model of head and neck and cervical cancer.