Bacterial delivery of phosphatase antagonists to metastatic breast cancer

Summary At this timethere is no cure for metastatic breast cancerThe prognosis for these patients is poorWith current standard of care treatmentsthe median survival time is three yearsWe propose to develop a novel bacterial drug delivery therapy into an effective and low toxicity therapeutic for breast cancer metastasesthat targets protein phosphatasePPAberrant phosphorylation in cell signaling is a hallmark of cancerPPis one of the major cellular phosphatases and gains its specificity via its interaction with overbinding partnersTargeting phosphatases is difficultdue to the difficulty of interrupting protein protein interactions and the lack of a binding pocket for small moleculesNIPPis a potent and specific nuclear inhibitor of PPA two fold increase of NIPPblocks PPfrom forming other holo enzymes and inhibits tumor proliferationSystemic delivery of this protein drug would induce severe side effectsdue to the essential role of PPThe specific tropism of Salmonella to breast cancer metastasesin ratios oftocompared to healthy tissue can produce and deliver protein drugs with high specificity to cancer cells and with minimal side effectsThe proof of concept for this study has been established by demonstrating thata bacterial lysis system can deliver proteins specifically into the cytoplasm of cancer cells andbacterial delivery of NIPPinduces cell death in breast cancer cellsIn this proposalwe want to determine the safety and efficacy of bacterially delivered NIPPEBTin mice and develop a bacterial delivery strain that is genetically stable and resistant to mutational loss of functionIn Aimwe will test the efficacy of EBTin liverlung and bone metastases in CDhumanized miceIn Aimwe will determine the maximum tolerated doseMTDof EBTand study acute toxicity in a dose escalation studyWe will measure the biodistribution of this therapy in mice with and without tumors to determine off target bacterial accumulation and protein deliveryIn Aimwe will develop a bacterial delivery strain with a constant lysis rateThe leakage of the lysin E genewhen unexpressedresults in bacterial stress and acquired resistance to lysisA directional promoter switch will be integrated that eliminates leakage in the OFF state and fully activates the lysin E gene in the ON stateThis genetic circuit prevents sublethal levels of lysine E in bacteriaThe robustness of this system will be tested in culture and in subcutaneous tumors in miceThe successful outcome of this proposal is the first step in the development of EBTas a new therapy for metastatic breast cancerFurther development of this therapy will be pursued in a Phase II SBIR to obtain the necessary data for an IND applicationThis research will establish a platform technology to directly deliver polypeptides into cells at critical points in signaling pathways and will be effective in a wide array of cancers Narrative The experimental plan describes the generation of a bacterial therapy targeting Protein Phosphatasein metastatic breast cancerThe research plan has three main componentsmeasuring the efficacy of the bacterially delivered NIPPin liverlung and bone metastasisdetermining the safety profile and the maximum tolerated dose of this therapy and creating a stable bacterial delivery strain that can be used in clinical trials