Genetically modified bacteria induce durable tumor regression &systemic antitumor immunity

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Scientists have used genetically reprogrammed bacteria to destroy tumors in mice. The innovative method one day may lead to cancer therapies that treat the disease more precisely, without the side effects of conventional drugs.

The researchers already are scrambling to develop a commercial treatment, but success in mice does not guarantee that this strategy will work in people. Still, the new study, published on Wednesday in the journal Nature Medicine, is a harbinger of things to come, said Dr. Michael Dougan, an immunologist at Massachusetts General Hospital in Boston.

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Bacteria cannot make normal antibodies for CD47. But recently, Dr. Dougan and his colleagues developed a tiny version of the molecule called a nanobody.

Not only are nanobodies small enough for bacteria to produce, they’re also much more potent than conventional antibodies.

The researchers inserted the nanobody gene into the bacteria, turning them into nanobody factories. Then the team injected five million of the altered microbes into mouse tumors.

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The bacteria were also programmed to commit mass suicide. After they established themselves and multiplied, 90 percent of the bacteria ripped themselves apart, spilling out nanobodies. The nanobodies attached to CD47 proteins on the cancer cells, robbing them of their camouflage.

In addition, fragments of the dead bacteria leaked out of the tumor. These bits of debris drew the attention of immune cells, which attacked the uncloaked cancer cells.

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