Combine Mitochondrial Gene Therapy and Synthetic Lethal Chemotherapy to Treat Triple-Negative Breast Cancer

Abstract Triple-negative breast cancers (TNBCs) are highly aggressive and standard cytotoxic chemotherapies (e.g. anthracycline-taxane) are the main treatment strategies in clinics. Our previous research and literature demonstrated that poly (ADP-Ribose) polymerase inhibitors (PARPi) as single agents or in combination with epidermal growth factor receptor inhibitor (EGFRi) induced a contextual synthetic lethality and reduced TNBC metastsis by inhibiting the repair of DNA damage. Our clinical trial showed that veliparib (PARPi)/lapatinib (EGFRi) achieved a 24% response rate in TNBC patients with wildtype BRCA1/2. Despite these achievements, TNBC cells often develop drug resistance to chemotherapies, have low patient response rate, and regrow after primary treatment. Novel strategies that can effectively treat TNBCs are urgently needed. Mitochondria are the powerhouse of cells and play a pivotal role in regulating cell functions, rendering them a promising oncological target. Destroying mitochondrial function, such as directly depolarizing the inner mitochondrial membrane (IMM) potential via synthesized heterologous genes, can bypass the repair of signaling transduction pathways, trigger a point-of-no-return cancer cell death, and subsequently prevent the development of drug resistance. We recently developed a mitochondrial luminoptogenetics (mLumiOpto) technology by synthesizing the heterologous light-gated channel rhodopsin in IMM and an engineered luciferase in cytoplasm, which induces IMM depolarization through opening mitochondrial channel rhodopsin with luciferase-luciferin emitted endogenous blue bioluminescence. Preliminary studies showed that mLumiOpto effectively depolarized mitochondria in TNBC cell lines representing multiple subtypes, resulted in persistent DNA damage, and significantly reduced tumor burden in three TNBC xenograft models. Applying our dual-targeted delivery vehicle, i.e. EGFR/CD276 monoclonal antibodies tagged exosome-associated adeno-associated virus (mAb-Exo-AAV), and cancer-specific promoter (cfos) in mLumiOpto achieved high TNBC specificity, functional expression, and minimal undesirable systemic toxicity. The objective of this project is to harness the combination of targeted mLumiOpto that is delivered with mAb-Exo-AAV and PARPi to eliminate TNBC cells in vivo. The hypothesis is that the combined mLumiOpto/PARPi integrates multiple anti-cancer mechanisms, i.e., IMM depolarization, DNA damage and inhibition of repair, and tumoral immunity. Specifically, large-scale dual-targeted mLumiOpto will be generated and characterized; treatment dosage and strategy will be optimized; and anti- cancer efficacy will be evaluated in TNBC primary xenograft model and distant metastatic model (Aim 1). Furthermore, the synergistic effects of mLumiOpto/PARPi will be assessed and the underlying mechanisms will be investigated in immunocompetent models (Aim 2). Finally, the metastasis reduction and heterogeneous TNBC treatment efficacy will be fully tested in metastatic and patient-derived xenograft (PDX) models, and toxicology will also be investigated (Aim 3). Successful completion of this project will provide a new strategy to treat TNBCs.