The scientists found a way to exploit a special germs taste for oxygen-starved environments and direct them to target pockets of dead and dying cells within large tumors. These advanced tumors generally have areas of poor blood circulation and thus little oxygen. The lack of oxygen renders them relatively resistant to conventional chemotherapy and radiation but open to bacteria that can grow without oxygen.
The idea is to selectively attack these tumors from inside with the bacteria and from the outside with chemotherapy, says Bert Vogelstein, M.D., Clayton Professor of Oncology and Investigator, Howard Hughes Medical Institute.
The scientists systematically screened numerous bacterial species to find one that would thrive in an oxygen-poor environment and, at the same time, destroy surrounding tumor cells. They settled on one spore-forming bacterial species, called Clostridium novyi (C.novyi). C.novyi is normally found in soil and dust and contains a toxin that can cause lethal side effects in animals. They genetically modified the bacteria to remove the toxin gene to make them harmless to normal animals. Then, they injected spores of these bacteria and conventional chemotherapeutic agents into mice with large tumors composed of transplanted human colon cancer cells.
The results achieved with this strategy, called COBALT for combination bacteriolytic therapy were dramatic. More than half of the tumors treated, including very large tumors, were completely destroyed within 24 hours. The tumors decomposed and turned into blackened scars, while the surrounding healthy tissues remained intact. The tumor scars then gradually disappeared over the next two wee
Contact: Vanessa Wasta
Johns Hopkins Medical Institutions