Study Reveals Common Viruses Can Reactivate Dormant Breast Cancer

Understanding the Link Between Viral Infections and Breast Cancer Relapse

Breast cancer survivors who have been in remission for years or even decades must remain vigilant about their health, as new research suggests that common viruses could pose a significant risk. Emerging evidence indicates that certain respiratory infections might reactivate dormant breast cancer cells, leading to a higher likelihood of cancer recurrence.

According to molecular geneticist James DeGregori from the University of Colorado, dormant cancer cells can be likened to embers in an abandoned campfire. Just as a strong wind can reignite those embers, respiratory viruses may awaken these dormant cells, increasing the risk of cancer returning.

This concern gained attention following the COVID-19 pandemic, when researchers observed an unusual increase in cancer cases among patients who had previously been in remission. DeGregori and his team conducted studies using human population data and mouse models to explore this phenomenon further.

Increased Risk of Cancer-Related Death

The findings were alarming. Patients in the UK Biobank who tested positive for SARS-CoV-2 showed a twofold increase in cancer-related deaths. Roel Vermeulen, an epidemiologist from Utrecht University in Sweden, noted that such a significant effect is rare in cancer epidemiology.

In addition, a study analyzing nearly 37,000 breast cancer patients in the United States revealed that a prior SARS-CoV-2 infection was associated with a greater than 40 percent increased risk of metastatic breast cancer in the lungs. These results highlight the potential dangers of viral infections for cancer survivors.

Mouse Studies Show Virus-Induced Cancer Spread

Research on mice further supports these findings. Influenza and SARS-CoV-2 infections caused dormant breast cancer cells to proliferate rapidly. Within two weeks, there was a massive expansion of carcinoma cells into metastatic lesions by more than 100-fold. The authors, led by molecular geneticist Shi Chia from the University of Colorado, emphasize that while caution is needed due to species differences, the findings underscore the substantial metastatic risk posed by these viruses to cancer survivors.

Viruses and Their Role in Cancer Development

For many years, scientists have suspected that certain viruses, like the Epstein-Barr Virus (EBV), may contribute to the development of specific cancers. The human papillomavirus (HPV) is already known to cause cervical cancer, and the HPV vaccine has been instrumental in preventing this disease.

Since 1936, researchers have searched for a virus that triggers breast cancer in a similar manner, primarily through studies in mice and human populations. High-risk viruses have been detected in human breast cancer samples, with EBV being five times more prevalent in breast cancer tissue than in normal tissue.

Despite these findings, research on the mechanisms linking viruses to cancer in human cells remains limited. The exact process by which viruses lead to cancer spread is still not fully understood.

Immune System Response and Cancer Activation

The immune system's response to viral infections may play a critical role in activating dormant cancer cells. Inflammation caused by respiratory viruses like the flu and COVID-19 can trigger the reactivation of these cells.

In experiments with mice, the influenza A virus only reawakened dormant cancer cells in the lung if it caused an increase in inflammatory cytokines, such as IL-6. The same pattern was observed with the coronavirus.

These findings suggest that the immune system’s reaction to viruses creates an environment conducive to cancer proliferation. DeGregori explains that for cancer survivors with dormant cells, a respiratory infection could significantly increase the risk of death from cancer recurrence.

Protecting Cancer Survivors

If these findings are confirmed, it will be essential to protect the millions of breast cancer survivors who may face an increased risk of relapse after contracting a viral infection. Further research is needed to determine whether vaccination against influenza or COVID-19 can help reduce this risk.

The study, published in Nature, highlights the importance of ongoing research into the relationship between viral infections and cancer recurrence. As our understanding of this complex interaction deepens, it may lead to new strategies for preventing cancer relapse in survivors.