Background

Cancer is a global scourge; it strikes without regard to age, race, gender, ethnicity, and socioeconomic class. Fortunately, such treatment options as radiation therapy and chemotherapy have dramatically improved patient outcomes, prolonging life in most patients and offering a cure to others. While radiotherapy has achieved sub-millimeter1 precision in targeting solid tumor cancers, chemotherapy is administered systemically, resulting in off-target effects in healthy dividing cells, often with considerable disruption to quality of life. Loss of white blood cell progenitors leads to a broken immune system. Death of cells lining the digestive tract causes vomiting and diarrhea. Damage to cells of the hair follicle brings baldness and the immense toll on one’s body image.

Interesting Cancer graphs

SilenshR is a synthetic biology solution that leverages the innate capacity of bacteria to colonize the hypoxic and immune-privileged cores of tumors, conferring specificity to a systemic therapeutic approach. Once the SilenshR E. coli reach a cell density of 2*10¹¹ colony forming units (cfu) per milliliter within the tumor, genetic circuits are activated allowing SilenshR recombinants to invade cancer cells and release a short hairpin RNA (shRNA) targeting an expressed oncogene thereby halting the unchecked cellular proliferation of cancer. By circumventing the need for systemic delivery of chemotherapy and the inevitable off-target cytotoxicity, SilenshR keeps the immune system intact, spares the digestive epithelial lining from damage and relieves anxiety surrounding hair loss.

In this project, we optimize and expand the applications of this mechanism. We will use quorum sensing as an additional safeguard to make sure that this mechanism only attacks cancer cells. With quorum sensing, this mechanism will only be activated when a certain bacterial cell density is reached. This density is only possible in very anaerobic environments, which is characteristic of tumors. Challenges to this include the natural anaerobic environment in the gut and whether the bacteria will proliferate in a healthy gut as well. To resolve this, we are working to put the quorum sensing circuit under the control of a nitric oxide promoter. Since nitric-oxide rich environments are only characteristic of areas of inflammation and are highly characteristic of cancer, having the quorum sensing circuit under the control of a nitric-oxide promoter that is only activated in nitric-oxide rich environments would prevent the bacteria from invading healthy gut cells even when quorum is reached. A synthetic alternative to this mechanism that would be simpler to test in the laboratory is to control the quorum circuit with a tet (tetracycline) on system where a tet repressor represses the expression of the invasion circuit when tetracycline and/or doxycycline is not present. When doxycycline/tetracycline is synthetically introduced to the environment, the tet repressor is repressed by the rtTA (reverse tetracycline-controlled transactivator), and transcription of the invasion circuit occurs. The doxycycline/tetracycline can only be introduced to cancer sites.

We are targeting cervical cancer and prostate cancer. We will determine the effectiveness of this mechanism in each of these cancers using proof-of-concept experiments by inhibiting eGFP. We will then target oncogenes in these cancers.