The tumor microenvironment (TME) consists of mediators surrounding a tumor, including diverse cell types, blood vessels, and other cellular components. Certain elements of the TME can benefit patients by making tumors more responsive to therapy or supporting a favorable immune response. However, the TME can also contribute to tumor growth and progression.
The complexity of the TME has driven extensive cancer research, improving our ability to visualize and interpret its components in individual patients. Researchers have also developed strategies to leverage beneficial aspects of the TME while minimizing harmful effects.
In honor of today’s Christmas holiday and Santa’s overnight visit, let’s see where some of the different parts of the TME fell on Santa’s ‘Naughty’ and ‘Nice’ lists.
When the Christmas stockings are hung by the chimney with care, they stay hot like we want to see TMEs!
A 'hot' TME contains many immune mediators that promote anti-tumor responses. These environments are rich in immune cells such as cytotoxic T cells, which destroy tumor cells. Dendritic cells, which identify foreign antigens and present them to T cells, are also present. Other supportive immune cells, including natural killer cells, M1 macrophages, and helper T cells, are often found in high numbers in a hot TME.
Cells are not the only factors influencing a hot TME. Cytokines, which are proteins that regulate and enhance immune responses, also play a key role. A TME rich in pro-inflammatory cytokines can activate the immune system, which is essential in combating cancer.
Tumors associated with a hot TME are also more likely to undergo mutations resulting in the expression of molecules called neoantigens. While an increase in mutations might sound like a bad thing, the presence of neoantigens actually helps the immune system identify tumor cells.
While Christmas is synonymous with snow, when it comes to the TME, we aren’t getting any joy from the cold ones!
A 'cold' TME is immunosuppressive, reducing both natural and therapy-induced immune responses. Tumors with a cold TME are unlikely to elicit effective anti-tumor immunity.
Immune cells that suppress anti-tumor responses, such as regulatory T cells and myeloid-derived suppressor cells, accumulate in cold tumors and prevent tumor cell identification and destruction.
Sources: Curr Biol, Front Immunol, Nat Rev Immunol
