Expanding the therapeutic window of bacteria for cancer therapy

Abstract

Engineered bacteria enable self-amplifying therapeutic delivery and immune activation, yet these same features drive systemic toxicity and off-target growth. Here, we create a "tumorobe" that overcomes these limitations by integrating reduced immunogenicity, tumour-restricted growth, and enhanced payload release. Specifically, we identify lipopolysaccharide modifications that reduce immunogenicity while preserving fitness, restrict growth to tumours using a hypoxia-lactate "AND" gate, and enhance extracellular payload release via lipoprotein deletion. This strain expands the maximum tolerated dose in a route-dependent manner by up to 1,000-fold. Across multiple murine models, including colorectal cancer and glioblastoma, the strain drives robust antitumour efficacy as both a standalone therapeutic and an immunotherapeutic delivery platform, achieving durable complete responses in up to 75% of colorectal tumours when armed with a cytokine payload. Together, these results establish a broadly applicable platform for safe and effective bacterial cancer therapy.