Bifidobacterium longum as a delivery system for cancer gene therapy: Selective localization and growth in hypoxic tumors

A fundamental obstacle in gene therapy for cancer is the specific delivery of an anticancer gene product to a solid tumor, and yet no systemic deliver y system that specifically targets solid tumors currently exists. A strain of domestic bacteria, Bifidobacterium longum, which is nonpathogenic and an aerobic, selectively localized and proliferated in several types of. mouse solid tumors after systemic application. In this report, we further describ e a novel approach to cancer gene therapy in which genetically engineered B ifidobacterium is used as a tumor-specific vector. Similarly to wild-type B . longum, genetically engineered B. longum could be detected in tumor tissu e only and was not found in a large survey of normal mouse tissues after in travenous injection. This finding strongly suggests that obligate anaerobic bacteria such as Bifidobacterium can be used as highly specific gene deliv ery vectors for cancer gene therapy.