Figure 2. Engineered circuits for bacterial cancer therapy.

(A) Targeting to tumor cells can be achieved by expression of tumor-specific peptides on the bacterial outer membrane. (B) Tumor microenvironments can be sensed specifically by AND logic gates, which expresses an output such as a therapeutic only if all required inputs or markers of the tumor microenvironment are present. (C) In many cases lysis of bacteria must be induced to release therapeutics into the tumor; one relevant circuit is the synchronized lysis circuit which uses quorum sensing. (D) Therapeutics or other actions can be driven by inducing promoters through chemical inducers or radiation.