A virus that causes breast tumours in mice has been linked to gut bacteria, which allows the virus to evade immune responses that would otherwise recognise and destroy infected cells. Tumors emerge as a result of the microorganisms aiding in the viral replication.
In addition to assisting with digestion and delivering nutrients and metabolites, gut bacteria also collaborate with the immune system to fight pathogens, all of which have a significant impact on health. Nevertheless, certain gut bacteria have been connected to the growth of organ and digestive system malignancies. A recent study by scientists at the University of Chicago demonstrates that certain commensal bacteria encourage the growth of leukaemia brought on by the murine leukaemia virus by inhibiting the animal's adaptive anti-tumor immune response.
Three genes, referred to be negative immune regulators, are expressed more or upregulated in mice when commensal bacteria and a virus are present. Furthermore, the immune response that might ordinarily eliminate the tumour cells is suppressed. It is also recognised that two of these three adverse immune regulators are signs of a bad prognosis in people with certain types of cancer.
Using unique mice with a compromised immune system that were deficient in the adaptive immune system, the team ran a number of investigations on these animals. Similar to immunosufficient SPF mice with healthy immune systems, these mice developed tumours when exposed to the virus in the germ-free environment. Microorganisms, later identified as commensal bacteria, were therefore preventing the anti-tumor immune response from working.
The scientists later found that three genes called unfavourable immune regulators were present in sick mice and that commensal bacteria were responsible for activating these genes. These genes in this case suppressed an immune response that was intended to assault cancer cells, which is contrary to their regular purpose, which is to shut down the immune system once it has dealt with a virus. Two of the three enhanced negative immune regulators—Serpinb9b and Rnf128—are well-known to be indicators of a poor prognosis in people with some spontaneous cancers.
Furthermore, not that all commensal bacteria were tumor-promoting, so Golovkina and research team are still investigating how this immune-dampening capacity only manifests itself when bacteria and viruses are present.More research work is needed.