Cancer Cells Are Anchorage Independent

Individual Project Outline

Cancer Cell Proliferation is Anchorage-Independent

• Normal cells do not grow in culture if they are suspended in a liquid or semisolid medium. In order to proliferate they need to adhere to a solid surface.

• Cancer cells grow well in liquid, semisolid, and solid medium. Therefore they exhibit anchorage-independent growth.

• In the human body, normal cells anchor by binding to the extracellular matrix through cell surface proteins known as integrins. Integrins consist of 2 transmembrane polypeptides, the alpha and beta subunits. For each specific integrin the extracellular portions of the alpha and beta subunits interact to form the binding site for a particular ECM protein.

• Triggering apoptosis in the absence of proper anchorage is a safeguard of normal cells. Apoptosis in cancer cells is not triggered due to their inability to anchor to a cell surface.

Loss of Anchorage Dependence

Most normal animal cells do not grow well when they are suspended in fluid or a semisolid agar gel. If these cells make contact with a suitable surface, however, they attach, spread, and proliferate. This type of growth is called anchorage-dependent growth. Many cell lines derived from tumors and cells transformed by oncogenic agents are able to proliferate in suspension cultures or in a semisolid medium (methylcellulose or agarose) without attachment to a surface. This is called anchorage-independent growth. An advantage that has been derived from the ability of malignant cells to grow in soft agar (agarose) is the ability to grow cancer cells derived from human tumors to test their sensitivity to chemotherapeutic agents and to screen for potential new anticancer drugs.

Anchorage-independence correlates strongly with tumorogenicity and invasiveness

The ability of cells or a cell sample to grow on soft agar is understood to be an indication that cells that proliferate in that environment are anchorage independent. 0.3% agarose in...