Metabolic engineering of probiotic Escherichia coli for cytolytic therapy of tumors
Chung‐Jen Chiang, Po-Han Huang
Abstract
Abstract Bacterial cancer therapy was developed using probiotic Escherichia coli Nissle 1917 (EcN) for medical intervention of colorectal cancer. EcN was armed with HlyE, a small cytotoxic protein, under the control of the araBAD promoter (P BAD ). The intrinsic limitation of P BAD for the gene expression is known to be negated by glucose and afflicted with all-or-nothing induction in host bacteria. This issue was addressed by metabolic engineering of EcN to uncouple the glucose-mediated control circuit and the L-arabinose transport-induction loop and to block L-arabinose catabolism. As a result, the reprogrammed strain (designated EcNe) enabled efficient expression of HlyE in a temporal control manner. The HlyE production was insensitive to glucose and reached a saturated level in response to L-arabinose at 30–50 μM. Moreover, the administrated EcNe exhibited tumor-specific colonization with the tumor-to-organ ratio of 10 6 :1. Equipped with HlyE, EcNe significantly caused tumor regression in mice xenografted with human colorectal cancer cells. Overall, this study proposes a new strategy for the bacteria-mediated delivery of therapeutic proteins to tumors.