Remotely controlled listerial bactodrones for cancer immunotherapy

PROJECT SUMMARY Attenuated and avirulent strains of Listeria monocytogenes (Lm), that are delivered via intravenous injections, accumulate and propagate in primary tumors and metastases while being quickly cleared from healthy tissues.

We intend to use these strains as remotely controlled, tumor-specific anticancer payload delivery vehicles, bactodrones.

In this project we will engineer Lm to synthesize and secrete cyclic dinucleotides (c-di-NMPs) as potent innate immune system stimulators inside tumor microenvironments. On-site accumulation of c-di-NMPs will induce production of type I interferon via the STING innate immunity pathway.

This will improve the capacity of Lm to induce immunogenic tumor cell death and lead to the release of tumor-associated antigens, which will facilitate recruitment of tumor-specific CD8 T cells. The sustained tumor-localized c-di-NMP production will keep T cells and other anticancer immune cells activated.

To assess feasibility and efficacy of delivering intratumoral c-di-NMP via genetically engineered Lm, we will pursue two aims. In aim 1, we will engineer Lm to secrete enzymes for c-di-NMP synthesis in immune and tumor cells. In aim 2, the engineered Lm will deliver plasmids encoding a c-di-NMP synthases, via a process known as bactofection.

Both approaches are expected to turn infected cells in the tumor microenvironment into c-di-NMP producing factories and ensure durable STING activation.

Importantly, Lm-mediated c-di-NMP delivery systems will be made inducible with a benign chemical inducer, which will enable temporal control of STING activation and limit toxicity associated with systemic c-di-NMP exposure.

Following optimization of the Lm bactodrones in vitro, and in breast cancer cell line, we will test efficacy of periodic bactodrone injections in a mouse metastatic breast cancer model.

We anticipate that Lm bactodrones will become efficient vehicles for tumor-localized, temporally controlled and inexpensive delivery of genetic payloads for various antitumor activities.