Tumor-seeking salmonella treats brain tumors

Biomedical engineers at Duke University have recruited an unlikely ally in the fight against the deadliest form of brain cancer—a strain of salmonella that usually causes food poisoning. 

Clinicians sorely need new treatment approaches for glioblastoma, the most aggressive form of brain cancer. The blood-brain barrier—a protective sheath separating brain tissue from its blood vessels—makes it difficult to attack the disease with drugs.

It's also difficult to completely remove through surgery, as even tiny remnants inevitably spawn new tumors. Even with the best care currently available, median survival time is a dire 15 months, and only 10 percent of patients survive five years once diagnosed.

The Duke team decided to pursue an aggressive treatment option to match its opponent, turning to the bacterium Salmonella typhimurium. With a few genetic tweaks, the engineers turned the bacterium into a cancer-seeking missile that produces self-destruct orders deep within tumors.

Tests in rat models with extreme cases of the disease showed a remarkable 20 percent survival rate over 100 days—roughly equivalent to 10 human years—with the tumors going into complete remission.

"Since glioblastoma is so aggressive and difficult to treat, any change in the median survival rate is a big deal," said Jonathan Lyon, a PhD student. "And since few survive a glioblastoma diagnosis indefinitely, a 20 percent effective cure rate is phenomenal and very encouraging."