Understanding the Cell Biology of Cancer and Metastasis

In the fight against cancer in humans and animals, cancer researchers are the first in a long line of practitioners to take aim at this plague and to ultimately find a cure. Cancer research itself encompasses many specialized areas of study; some researchers focus on potential carcinogens, while others may study gene mutations linked to cancer. Some researchers want to understand how a cancer cell breaks free from its original location and is able to migrate and relocate to other tissues within the body (metastasis). These researchers may conduct experiments to measure a variety of cellular behaviors including cell adhesion, cell migration, cell invasion, and cell transformation (colony formation).  

Cell adhesion is a complex process involved in embryogenesis, migration/invasion, tissue remodeling, and wound healing. Cells adhere to extracellular matrix components via adhesion receptors. Evidence suggests that alterations in adhesion properties play a crucial role in the development and progression of cancer.

Cell migration is a multi-step process that also plays a role in cancer as well as other diseases like atherosclerosis and arthritis. There are different types of cell migration: chemotaxis is the migration of cells toward or away from a chemoattractant; haptotaxis is the migration of cells toward or along a gradient of extracellular matrix; and transmigration is the migration of cells through vascular endothelium.

Cell invasion is closely related to cell migration, except that cells do more than just migrate. Invasive cells move through and degrade the extracellular matrix into neighboring tissues in a process that involves proteolysis. To metastasize, a cancer cell must be able to breach the basement membrane barriers; however, cell invasion through the basement membrane also may occur during normal processes like immune system responses. Most invasive cells are also migratory, but not all migratory cells are invasive.

The ability to form a colony in soft agar is an important property of many cancer cells. Neoplastic cell transformation occurs via a series of genetic and epigenetic alterations that yield a cell population that is capable of proliferating independently of both external and internal signals that normally restrain growth. Transformed cells show reduced requirements for extracellular growth promoting factors, are not restricted by cell-cell contact, and are often immortal. Anchorage-independent growth is one of the hallmarks of cell transformation, which means cancerous cells are able to grow and divide without adhering to the basement membrane.