Evading the many obstacles that guard against runaway cell division is still not enough for cancer to develop. A malfunctioning cell must also skirt a number of safety mechanisms designed to prevent cells from growing where they are not supposed to in the body.
Normal cells adhere to each other and to a fibrous meshwork called an extracellular matrix. This matrix exists throughout all tissues and provides the structural support on which cells grow and form organs and other complex tissues. While a normal cell will often die if it cannot adhere to an extracellular matrix, cancer cells survive without this matrix.
About 90 percent of cancer deaths are caused by tumor metastasis Ė or when cancer cells break free and spread to other parts of the body. Yet, we donít have an exact understanding of the mechanism that causes that. So, how do tumor cells detach from the elements that normally hold tissues in place, and how do they reattach themselves someplace new? Cells in our body are tethered to a structural support system called the extracellular matrix, which also helps regulate cell behavior. On the surface of cells, proteins called integrins form the anchors that hold the cells in place; when cancer cells metastasize, these anchors let go. MIT researchers led by Sangeeta Bhatia compared the adhesion properties of four types of cancer cells: primary lung tumors that later metastasized, primary lung tumors that did not metastasize, metastatic tumors that migrated from the lungs to nearby lymph nodes, and metastatic tumors that traveled to more distant locations such as the liver.