A new view of cancer metastasis
arrive, they shift the amounts and types of immune cells in the lymph nodes.
In mice, for example, there were fewer cancer‐killing immune cells in lymph nodes that were invaded by melanoma than in lymph nodes that were cancer‐free, the researchers found.
There were also more immune cells called T‐regulatory cells( T‐regs) in lymph nodes that were invaded by melanoma cells.
And in tissue samples from people with head and neck cancer, there were more T‐regs in lymph nodes where cancer had invaded than in lymph nodes that were cancer‐free.
The main role of T‐regs is to protect healthy cells from attack by other immune cells that have gone off the rails. By doing so, T‐regs help prevent autoimmune diseases and chronic inflammation. But T‐regs can sometimes get mixed up, protecting unhealthy cells that should be eliminated, like cancer cells.
That’ s exactly what the researchers appeared to see in their mouse studies: In mice that were bred to lack T‐regs, melanoma tumors were less able to spread to the lungs.
The scientists then removed T‐regs from the lymph nodes of mice where melanoma had or hadn’ t invaded. They transferred the T‐ regs into other mice with melanoma that hadn’ t invaded the lymph nodes. Only the T‐regs from lymph nodes with cancer helped melanoma cells spread to the lungs, the researchers found.
Like other kinds of T cells, T‐regs have special receptors that let them“ recognize” the cells they protect. In mice with melanoma that invaded into lymph nodes, the researchers found T‐regs that recognized the cancer cells.
In the near future, the team plans to examine exactly how cancer cells in the lymph nodes coax T‐regs to protect them.
A new view of cancer metastasis
In the lymph nodes, immune cells learn what to attack( such as infected cells) and what to protect( such as healthy cells).
But this study suggests that, in lymph nodes invaded by cancer, immune cells learn to protect the cancer cells rather than attack them, Dr. Engleman said. This phenomenon is called immune tolerance.