RSV Blocks Breast Cancer Lung Spread in Mouse Study
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- Cecilia Johansson at Imperial College London led experiments in which 23 mice infected intranasally with RSV showed 65-70% fewer breast cancer tumor nodules in their lungs after 28 days compared with 16 saline-treated control mice.
- Type I interferons — infection-fighting proteins that help stop viruses replicating in lung cells — were identified as the mechanism, and direct intranasal delivery of two interferon doses was "slightly more" effective than the virus itself at blocking cancer cell seeding.
- The virus blocked entry but not growth — tumor nodules that did form in RSV-infected mice were similar in size to those in controls, indicating the effect targets cancer cells establishing new tumors rather than ones already established.
- Galectin-9, a protein produced in response to interferons, was singled out as particularly effective at preventing tumor cell seeding, and Johansson hopes it could be mimicked as a drug to prevent breast cancer and other tumors from spreading to the lungs.
- David Withers at Oxford University, who was not involved in the research, called the findings "exciting" and said manipulating tissue to shield patients from metastatic spread "has potential for enormous clinical benefit."
- A contrasting finding from another recent study found that swine flu and COVID-19 viruses may actually activate the growth of cancer cells that had been lying dormant after spreading to the lungs — complicating the broader picture of how respiratory viruses interact with metastasis.
- Clinical translation faces hurdles — Johansson cautioned that intranasally delivering type I interferons could trigger damaging airway inflammation, and the team is now planning further studies, with human trials more distant on the horizon.
Why it matters: Most cancer deaths occur when tumors metastasize, and the lungs are among the most common destinations — making any mechanism that blocks cancer cell seeding there clinically significant. If type I interferons or galectin-9 can be harnessed into a drug, it could add a new defensive layer against metastatic breast cancer and potentially other tumors. But the contrasting finding that flu and COVID-19 may wake dormant cancer cells shows viral-immune effects on metastasis cut both ways.
