A strain of salmonella that has been stored at room temperature for 50 years is able to recognize cancer cells that the immune system cannot detect. This discovery bodes well for patient-specific treatments to increase the effectiveness of immunotherapy.
Immunotherapy is a revolution in cancer treatment. It involves getting the immune system to fight back against cancer cells. However, some cancer cells can “hide,” which allows them to thrive in the body while destroying it.
Researchers at the University of Missouri have found a new way to help the immune system fight cancer more effectively. The results of their research were published in the journal Oncotarget.
The limits of immunotherapy
“Under normal circumstances, the body’s immune cells are constantly on patrol to identify and destroy foreign bodies in the body,” says Yves Chabu, assistant professor in the Department of Biological Sciences at the University of Missouri. Normal cells send out a molecular signal that says “don’t eat me,” which is recognized by immune cells and prevents the destruction of normal tissue. However, some cancers have also developed the ability to mimic normal cells and produce the “don’t eat me” signal. As a result, the immune system does not recognize cancerous tumors as defective tissue and leaves them alone, which is bad news for the patient.
Prescription immunotherapy drugs are designed to block the signal emitted by cancer cells. Without this signal, they are theoretically seen by the immune system and then destroyed by the body. However, due to its aggressiveness against the body, immunotherapy is not a perfect procedure, especially for prostate cancer.
A Salmonella that can detect tumors
To counteract the technique used by cancer cells, the researchers found a cure in a strain of bacteria that is more than 50 years old. They reused a strain of Salmonella that had been stored at room temperature for more than half a century. The genetic modification allowed this nontoxic bacterium, called CRC2631, to target cancer tumors. By bringing it into contact with prostate cancer cells from mice in vivo, the research team observed that CRC2631 indicated the location of the cancer cells, making it easier for the immune system to attack it.
“Cancers differ from individual to individual, even if they affect the same tissue,” says Yves Chabu. These differences help determine whether a particular therapy will effectively treat cancer and help the patient. The bacterium itself is genetically flexible, so it can be genetically modified to overcome a patient’s specific therapeutic limitations. Since CRC2631 preferentially colonizes tumor cells, the effect is primarily localized to the tumor. The use of CRC2631 to develop and apply patient-specific therapies suggests the potential of precision medicine, i.e., the ability to tailor a treatment to a specific patient.
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