One of the reasons cancer is so hard to treat effectively is because the body doesn’t recognize the cancer cells as dangerous. Because the rogue cells aren’t foreign, the body’s immune system doesn’t activate, and the cells are left to multiply.
New research, reported in Science Translational Medicine, may change that.
Researchers at the Chonnam National University in Hwasun Hospital in Jeonnam, Korea injected a modified strain of the food poisoning bug Salmonella into tumors. The strain was engineered to be much less potent than the strain that causes food poisoning, but it was powerful enough to still be recognized by the immune system as a foreign invader. The researchers then “weaponized” the bacteria by genetically modifying it to secrete a protein known as FlaB.
The results have been compelling. In one set of experiments, biologists Jung-Joon Min and Joon Haeng Rhee injected the Salmonella into 20 mice with human colon cancers. After several days, the mice had cleared the bacteria from their organs, but not from the cancerous tumors. After four months, the tumors were undetectable in more than half of the mice, and they remained healthy throughout the experiment. Control mice infected with bacteria that did not secrete FlaB died from the cancer.
In a second set of experiments, the scientists transplanted human colon cancer cells into three different sets of mice: eight treated with FlaB-secreting Salmonella, six treated with non-FlaB secreting Salmonella, and seven left untreated. After four weeks, the mice treated with non-FlaB secreting Salmonella and the mice left untreated had dozens of metastases. Those treated with the FlaB-secreting Salmonella, however, had just four secondary tumors total, and several showed no signs of metastasis.
Joon Haeng Rhee, one of the researchers on the experiments and a professor of microbiology at Chonnam, said: “We believe that this was a kind of groundbreaking trial to turn tumor-helping immune cells, Dr. Jekyll, into tumor-killing ones, Mr. Hyde.”
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