To confirm the effectivity of Bifidobacterium infantis–mediated herpes simplex virus thymidine kinase/ganciclovir suicide gene system on the treatment of renal cell carcinoma in nude mice and further explore the mechanisms.

A B infantis thymidine kinase (B infantis-TK) suicide gene system was constructed in our previous study. Tumor-bearing nude mice were randomized into 4 groups and injected with normal saline, B infantis, B infantis/pGEX-1λT, and B infantis-TK, respectively, via tail vein, followed by intraperitoneal injection of ganciclovir. The treatment effects were evaluated by the terminal deoxynucleotidyl transferase–mediated deoxynucleotide triphosphate nick end labeling assay, quantitative reverse transcriptase polymerase chain reaction, and Western blotting. Side effects were also recorded.

Compared with the other 3 treatments, the treatment with B infantis-TK resulted in a significant effective antitumor activity and stronger apoptotic response. Western blot analysis showed that the expression levels of Rel A and Bcl-xL were significantly lower, whereas those of caspase 3 and Bax were significantly higher in tumor tissues resected from group B infantis-TK, which were consistent with the quantitative reverse transcriptase-polymerase chain reaction results.

The B infantis-TK/ganciclovir therapy system exhibits an effective antitumor activity by promoting tumor cell apoptosis through both the intrinsic and the extrinsic apoptotic pathways.