Bug Helps Chemo Home in on Cancer
Scientists have found a bacterium that can help target anti-cancer drugs to the heart of a tumour, reducing the damage done to healthy tissues and minimising side effects. Writing in this weeks edition of the journal Science, Bert Vogelstein and his team, from the US Howard Hughes medical Institute, describe how a relative of the bacterium that causes tetanus, called Clostridium novyi-NT (C. novyi-NT), can selectively release chemotherapy drugs inside cancers. The researchers used mice with a form of colon cancer. The animals were first injected with spores from the C. novyi-NT bugs, followed by a dose of the chemotherapy chemical doxorubicin which had been packaged into tiny fatty droplets called liposomes. This provoked complete tumour regression in 100% of the mice, and 65% of them were still alive 90 days later. By comparison, none of the animals left untreated, or animals given just the chemotherapy agent or the bacteria alone survived for more than 40 days. The team found that the C. novyi-NT bacteria, which are anaerobes (they cannot grow in oxygen), first homed in on the oxygen-poor centre of an animal's tumour. There the bugs released a fat-digesting factor, called liposomase, which broke-open the packages of the chemotherapy chemical once it was administered, producing very high levels of the cancer-killing drug just within the tumour. The researchers have now pinpointed the gene used by C. novyi-NT to make the liposomase, which means it will be possible to produce the agent artificially and use it to better target chemotherapy to cancers, allowing doctors to use lower doses and therefore cut down side-effects.