Genetically engineered Bifidobacterium longum for tumor‐targeting enzyme‐prodrug therapy of autochthonous mammary tumors in rats

Abstract

A fundamental obstacle in systemic therapy for cancer patients is the specific targeting of therapy directly to solid tumors. A strain of the domestic bacterium Bifidobacterium longum, which is non-pathogenic and anaerobic, showed selective localization to and proliferation within solid tumors after systemic application. Here, we propose a novel approach to cancer gene therapy in which anaerobic and non-pathogenic bacteria of the genus B. longum are used to achieve tumor-specific gene delivery and enzymeprodrug therapy. We constructed a plasmid, pBLES100-S-eCD, which included eCD. Transfected B. longum produced CD in hypoxic tumors and achieved tumor site-specific conversion of 5-FC to 5-FU. Furthermore, we demonstrated antitumor efficacy in rat bearing autochthonous mammary tumors injected with the transfected B. longum directly or intravenously. This method was confirmed to be effective for enzyme-prodrug therapy not only by intratumoral injection but also by systemic administration. To estimate the toxicity of this bacterial vector, the systemic immunogenicity was evaluated by ASA reaction and the anaphylactic activity of IgG was evaluated by PCA reaction in guinea pigs. In the ASA reaction, no anaphylaxis symptoms were observed in any immunized guinea pigs injected with transfected B. longum. In the PCA reaction, B. longum/S-eCD specific-PCA-induced antibody was not detected. Thus, we proposed that anaerobic bacteria of the genus B. longum were an attractive and safe tumor-targeting vector and transfected B. longum was a potential anticancer agent that could effectively and specifically treat solid tumors. (Cancer Sci 2006; 97: 649-657)

Escherichia coli Nissle 1917 Targets and Restrains Mouse B16 Melanoma and 4T1 Breast Tumors through Expression of Azurin Protein

“…In addition, E. coli Nissle 1917-as an E. coli strain-has a comparatively simple genetic basis and therefore can be modified into an effective drug-producing machine more easily than other bacteria. In bacteriolytic cancer therapy, most studies focus on the use of cytokines (18,36), prodrugs (6,24), or bacteria per se (4, 43) for inhibiting tumor growth or metastasis. Here, we used the bacteria to express a secretory antitumor protein for cancer therapy.…”

“…Previous studies clearly showed that some bacteria can target and proliferate in solid tumors, significantly inhibiting the growth of tumors (32,34). So far, bacteria such as Clostridium (1,4,8), Salmonella (3,19,21), Bifidobacterium (24,41) and Escherichia coli (6,27) have been clinically employed for the delivery of drugs, RNA (35,42), and immune factors (18,36). Also, these bacteria are often used in combination with traditional methods such as radiation (4) and chemotherapy (25) for cancer therapy.…”

Bacterial vectors for imaging and cancer gene therapy: a review

“…107 B. longum selectively produces CD in hypoxic mammary tumor tissues in rats, and converts 5-FC into 5-FU in vivo. [108][109][110] This system could be significantly improved by combination with MR imaging technology.…”

Gene therapy for cancer: bacteria-mediated anti-angiogenesis therapy

“…2,4 Both Clostridia and Bifidobacteria have been successfully used for 'enzyme-prodrug' therapy. 41 Owing to their obligate anaerobic nature, ability to form spores and ease of transformation, Clostridia are especially suited to AGT for tumors. 42,43 Further, their ability to colonize tumors in vivo can be enhanced by deletion of genes associated with basal oxygen tolerance, such as that encoding superoxide dismutase.…”