Engineered gene networks enable non-genetic drug resistance and enhanced cellular robustness

Drug resistance complicates the treatment of cancer and infectious diseases, and often arises from the elevated expression of a gene that neutralises or reduces drug activity. To investigate this and other expression-based mechanisms of drug resistance, the authors engineered a set of gene regulatory networks in the eukaryotic model organism Saccharomyces cerevisiae to control a homologue of the cancer-related human multidrug resistance gene MDR1. Using this system, they explored experimentally how different gene regulatory network features, also called genetic network motifs, contribute to gene expression dynamics and cellular fitness. They observed that coherent feedforward and positive feedback motifs enable rapid and self-sustained activation of gene expression, and enhance cell survival in the presence of a cytotoxic drug. These observations underscore that genetic network motifs can be critical for drug resistance and that genetic network engineering can be used to enhance cellular tolerance to cytotoxins or other environmental stresses.