Science Supplement: Bacteria kill cancer?
Release date: 2017-02-13
We all know that cancer is very embarrassing. They are good at pretending to be able to escape the detection of the immune system and thus proliferate and spread in human tissues and organs. In order to activate the immune system to attack cancer cells, scientists have come up with many ways. Now, they have another move: use bacteria to fight cancer!
This is the result of a recent research team from South Korea’s National University of Science and Technology published in the Science publication Science Translational Medicine. They modified a gastroenteritis-causing pathogen that allowed it to express a key protein that stimulates the immune system against tumor tissue and confirmed in mice that the bacteria did indeed cause tumor atrophy, and in the first time Stop cancer metastasis.
Bacterial anticancer therapy
The internal environment of the tumor is hypoxic, and there is necrosis prevention. It is the place where most anaerobic bacteria are happy to station, such as Salmonella, Clostridium, and Listeria. So if these bacteria have the ability to fight cancer, then they can "locally", killing cancer cells directly and mobilizing immune cells to further attack cancer.
Although most bacteria are based on the above principles, the treatment is not easy. The first priority is safety, because the bacteria themselves are harmful to the body, and patients need to be injected with antibiotics while receiving treatment. Second, even if the effect is optimal, the probability of tumor recurrence is high.
Some scientists liken the cancer-resistant bacteria to a "black box". Although they can clearly understand the tumor, they do not know the specific molecular mechanism. To date, only one anti-cancer therapy based on this principle has been approved by the FDA for the treatment of bladder cancer, and the rest are under investigation.
Transforming harmless bacteria and inhibiting cancer proliferation and spread
Salmonella is a common foodborne pathogen and the chief culprit in most food poisoning.
In 2006, scientists at the National University of South Korea tried to develop a vaccine that targets Vibrio vulnificus. When they used Vibrio vulnificus as the research material, they found that the flagellar part responsible for swimming expressed a protein, FlaB, which strongly activated the immune response. Therefore, the researchers turned to a harmless Salmonella typhimurium and genetically engineered it to express the FlaB protein.
Biologists Jung-Joon Min and Joon Haeng Rhee led the team to test the modified Salmonella to assess their impact on cancer.
They injected the modified Salmonella into mice by using a sterile mouse transplanted with human colon cancer tissue (the liver, lung, and spleen tissues do not contain bacteria). Three days later, the researchers found that the colon tumor tissues of these 20 mice were covered with Salmonella. After 120 days, 11 of the mice had no tumor tissue detected and remained healthy during the experimental period. The control mice (injected Salmonella did not undergo genetic modification, did not express the FlaB protein) eventually died of cancer.
Subsequently, the researchers injected metastatic colon cancer tissue into mice and divided them into three groups: one group (8 mice) injected with Salmonella secreting FlaB protein; the other group (6 mice) injected without Modified Salmonella; the last group (7 mice) did not receive any bacterial treatment. After 27 days, dozens of metastases occurred in untreated and cancer-treated mice. However, 8 mice injected with modified Salmonella showed only up to 4 secondary tumors, and even some mice did not metastasize.
Studies have shown that the FlaB protein inhibits the spread of cancer, and it activates the downstream molecule, TLR5, which is responsible for escalating the immune response. Next, the researchers will continue to refine the technology, and within a few years, Min and Rhee plan to conduct clinical trials to verify the safety and efficacy of this particular bacterial anticancer.
Source: Bio-Exploration
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