These viruses can promote lung metastasis of breast cancer

Respiratory viruses, such as influenza or SARS-CoV-2, can activate dormant breast cancer cells that have spread to the lungs, paving the way for new metastatic tumors, according to a study in mice that sheds light on the association between infectious diseases and metastasis.

The details are published in the journal Nature , in a paper led by scientists from the United States, the United Kingdom and the Netherlands, who also collected human observational data to corroborate their findings.

"Our findings indicate that people with a history of cancer may benefit from taking precautions against respiratory viruses, such as getting vaccinated when possible," said Julio Aguirre-Ghiso, co-director of the study.

Breast cancer is the most commonly diagnosed cancer in women. After an initial remission, cancer cells can remain dormant for years before metastasis (to the lungs or other organs) causes a relapse.

Viral respiratory infections, such as SARS-CoV-2, are associated with inflammation, which can trigger processes that could influence metastasis, explains a note in the journal.

The potential increase in cancer mortality rates reported in some studies during the first two years of the pandemic led James DeGregori and his team at the University of Colorado Cancer Center in the United States to study the effects of influenza virus and SARS-CoV-2 infections on breast cancer outcomes in mouse models.

To do this, the researchers exposed the animals to these two viruses. In both cases, the respiratory infections triggered the awakening of dormant, disseminated cancer cells in the lungs. which led to a massive expansion of metastatic cells within a few days of infection and the appearance of metastatic lesions within two weeks.

"Dormant cancer cells are like the embers left behind in an abandoned campfire, and respiratory viruses are like a strong wind rekindling the flames," DeGregori summarized in a statement from the University of Colorado Anschutz Medical Campus.

Molecular analysis revealed that the awakening of dormant, disseminated cancer cells is driven by interleukin-6 (IL-6), a protein that immune cells release in response to infection or injury.

"The identification of IL-6 as a key mediator in awakening these cells from their dormant state suggests that the use of IL-6 inhibitors or other targeted immunotherapies could prevent or reduce the resurgence of metastasis following a viral infection," according to Aguirre-Ghiso.

Following these findings, the team analyzed two large databases and found support for their hypothesis that respiratory infections in cancer patients in remission are linked to cancer metastasis.

They analyzed data from the UK Biobank (4,837 participants, all cancer types) and the US database Flatiron Health (almost 37,000 breast cancer patients).

The team observed an association between SARS-CoV-2 infection and the risk of death in the biobank group; patients who tested positive for SARS-CoV-2 compared to those who tested negative showed a twofold increase in cancer-related deaths.

In the Flatiron group, SARS-CoV-2 infection was associated with a more than 40% increased risk of metastatic disease to the lungs.

Taken together, the findings reveal how respiratory virus infections can increase the risk of cancer relapse and highlight the need for strategies to address the increased risk of metastatic progression associated with respiratory viruses, the authors conclude.

*Stay up to date with the news, join our WhatsApp channel

Also read: Remaining holidays and long weekends in 2025 with extra pay for work

OF