On aging, red blood cells lose protein CD47. Finally, immune cells no longer skip and destroy the old cells to make room for new ones. Mutations in cancer cells can cause the CD47 gene to be involved. The immune system then sees these cells as harmless, allowing them to grow into dangerous tumors.
In recent years, scientists have developed antibodies that can bind CD47 proteins to cancer cells. Then immune cells learn to recognize cancer cells as dangerous and aggressive, but standard antibodies are large molecules that can not be inserted into a large tumor. And since they need to inject into the bloodstream, these antibodies end up all over the body, causing side effects.
Dr. Nicholas Arpais, an immunologist from Columbia University in New York and a synthetic biologist, Dr. Tal Danino, wondered if they could use bacteria and turn the immune system into cancer cells but from the tumor rather than outside. Ordinary bacteria will accept tumors in the body and they will be their hideouts from the immune system. In 2016, Dr. Danino helped build bacteria that can create drugs to fight the tumors once they get in.
Bacteria can not produce normal antibodies to CD47, but Dr. Dugan and his colleagues have recently developed a small version of the molecule called nanoparticles. They are not only small enough but are much more powerful than conventional antibodies. Researchers inserted the gene into bacteria and turned them into nanotechnological plants. And their five million injected into tumors in mice. They were programmed to "commit" mass suicide.
After being closed and multiplied, 90 bacteria were destroyed and thus nanoparticles were discarded. They were glued to CD47 and tumor cells and thus removed their protection. The dead bacteria cut the tumor and drew the attention of the immune system that attacks the cancer cells. In the circumscribed tumor, surviving bacteria began to multiply. When their population grows, the majority is again committing suicide, and so it fired another contingent of nanotechnologies and fragments. A double attack can remove the tumors in which it is injected.
When Dr. Dugan and his colleagues developed CD47 nanoparticles, they realized transport to cancer cells was critical to its effectiveness, but they never thought anyone would hide it in a microscopic Trojan horse.
"I love when something like that happens, that's a great little machine," said Dr. Dugan.
This approach has the potential to reduce the side effects of cancer treatment. Instead of swallowing the body of mice with drugs, the bacteria are targeting tumors. Thanks to their miniaturization, the leakage of nanoparticles from cancer cells quickly clears the body. Once the bacteria killed a tumor, other tumors in mice also declined. It is possible for bacteria to help the immune system and to learn to recognize other cancer cells.
Can people against cancer as well as mice?
In previous studies, scientists have shown that bacteria that swallow mice can reach the liver and from there to attack tumors. This is a very important finding because the liver is most often categorized as cancer. If such reprogrammed bacteria help the immune system cells to recognize a tumor in the liver, they can attack cancer in other parts of the body.
However, Dr. Dugan warns that such programmed bacteria in humans should not be as strong as in mice.
– In principle, we have the same system, but only to a greater extent. This means that things are not transmitted so effectively from one part of the person to another – he says.
A new study shows how advanced synthetic biology has advanced in recent years, says Tim Lou, a biologist and co-founder of Sinlodzik, who also reprogrammed bacteria to fight cancer.
– These things are not seen as crazy things about the game. They can potentially find their way to the patients, "he concludes.