Cancer therapy employing the tumour suppressing bacterium Caulobacter crescentus

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We will exploit the flexible foreign protein display capabilities and the anti-tumor properties of the bacterium Caulobacter crescentus to develop a potent therapeutic cancer vaccine, hi mouse models we will examine the value of a) direct stimulation of immune system components by antibody-based targeting of cancer antigens in concert with other displayed immune stimulants and b) targeting tumors with Caulobacters displaying tumor-directed antibodies as well as cancer antigens and immune stimulants. Therapeutic cancer vaccine approaches offer significant advantages over chemotherapy, but finding the combination of antigen, delivery vehicle and adjuvanation to break anergy has proven difficult. Treatment using bacteria is a promising approach. One (BCG) is currently used for bladder cancer. Some bacteria exhibit anti-tumor properties but are pathogenic and propagate in the host and so are poorly suited for humans. This proposal offers an alternative. Caulobacter crescentus is a non-pathogen that does not replicate in mammals. It exhibits a crystalline protein surface (S) layer that is readily adapted to display large protein segments at high surface density. It also has strong anti-tumor properties. We will combine these observations to develop a therapeutic for cancer, requiring the microbial genetics efforts of a natural science lab to produce candidate therapeutics with the formulation expertise of a Pharmacy lab to evaluate efficacy and potency. Some specific Objectives: l)We will display single chain antibodies targeting receptors of dendritic cells (e.g., DEC-205) and simultaneously display cancer antigens (e.g., MUC1 and 5T4) and immune stimulants such as GM-CSF. This is done by expression of multiple modified S-layer protein genes. We can also use Protein G (IgG binding) display to "load" Caulobacters with targeting monoclonals. 2) We will also target vaccine formulations directly to tumors by use of antibodies to tumor markers, expecting to stimulate infiltrating immune cells. Several model systems will be tested including Lewis Lung Carcinoma and EMT-6 Murine Mammary tumor, the best results from prophylactic mode testing will also be evaluated in therapeutic mode.