A tunable dual-promoter integrator for targeting of cancer cells

Precise discrimination between similar cellular states is essential for autonomous decision-making scenarios, such as in vivo targeting of diseased cells. Discrimination could be achieved by delivering an effector gene expressed under a highly active context-specific promoter. Yet, a single-promoter approach has linear response and offers limited control of specificity and efficacy. Here, we constructed a dual-promoter integrator, which expresses an effector gene only when the combined activity of two internal input promoters is high. A tunable response provides flexibility in choosing promoter inputs and effector gene output. Experiments using one premalignant and four cancer cell lines, over a wide range of promoter activities, revealed a digital-like response of input amplification following a sharp activation threshold. The response function is cell dependent with its overall magnitude increasing with degree of malignancy. The tunable digital-like response provides robustness, acts to remove input noise minimizing false-positive identification of cell states, and improves targeting precision and efficacy. Molecular Systems Biology 6: 444; published online 21 December 2010; doi:10.1038/msb.2010.99