Some Viruses that Cause Cancer Suppress the Immune System with Help from Common Bacteria
Published:30 Sep.2022 Source:University of Chicago
Gut bacteria have a profound impact on health by aiding digestion, providing nutrients and metabolites, and working with the immune system to fend off pathogens. Some gut bacteria, however, have been implicated in progression of cancers of the gut and associated organs.
A new study by researchers from the University of Chicago shows that some commensal bacteria promote the development of leukemia caused by the murine leukemia virus (MuLV) by suppressing the animal's adaptive anti-tumor immune response. When both the virus and commensal bacteria are present in mice, three genes known as negative immune regulators are expressed more, or upregulated, which in turn tamps down the immune response that would otherwise kill the tumor cells. Two of these three negative immune regulators are also known to be indicators of poor prognosis for humans with some forms of cancer.
The team performed a series of experiments with immunodeficient mice that were specially engineered, so they lacked the adaptive immune system. In the germ-free setting, these mice developed tumors when exposed to the virus with the same frequency as immunosufficient SPF mice with intact immune systems. So, the anti-tumor immune response was being counteracted by microorganisms, which were subsequently identified as commensal bacteria.