CANCER
Cancer is NOT just one type of cell. It is a matrix, like a city, housing different populations of cells. These populations include: cancer cells, cancer stem cells, many types of immune cells in a support network of fibrous soft tissue. The non-cancer cells together with the fibrous material create a protective bubble.
The protective bubble is know as the tumor microenvironment (TME) and the materials and cells in it are collectively called stroma. The stroma builds up a stiff, low oxygen environment, where blood vessels get leaky and immune cells sent to fight the cancer get trapped. The tumor microenvironment promotes the cancer growth and protects it from treatments including chemotherapy and radiotherapy.
Stroma
Stroma is like a wall and a moat around a castle and is vital to shield the cancer. Hard-to-treat cancers, like pancreatic cancer, generally have higher levels of stroma.
Many of the proteins involved in building stroma are normal wound healing proteins that get to work, for example when you cut yourself. They promote secretion of chemicals that promote healing but also cancer growth and development.
The stroma traps and immobilises immune cells sent to fight the cancer. It may also facilitate the ability of cancer cells to communicate with and control immune and stroma cells in the vicinity.
The immune and other stromal cells under the control of the cancer no longer eliminate the diseased cells. In this way immune cells sent to fight the cancer instead become supportive of the cancer, for example M2 macrophages, and cancer associated fibroblasts (CAF) are pro-cancer.
It has been well known for a number of years that stroma plays a role in cancer but, until now, there have been limited options for dealing with the complicated multi-component mechanisms involved in its development.
Picture Credit: National Cancer Institute
