Primary tumors of the central nervous system (CNS) are notoriously difficult to control, due in large measure to their highly invasive behavior. The ability of cells to migrate through tissue depends, in part, on the composition of the tissue's extracellular matrix. Understanding the molecular composition of the extracellular environment of brain tumors may, therefore, be one approach to developing methods to prevent tumor invasion. Over the last several years, the investigators have characterized some of the components of the extracellular matrix in brain and have shown that the composition of the matrix changes over the course of development. A return to an immature matrix composition during tumor growth could support the high mitotic rate of tumor cells, facilitate the motility of these cells, and foster angiogenesis. They recently identified the gene for a new extracellular matrix protein, BEHAB (Brain Enriched HyAluronan-Binding). BEHAB is expressed at high levels in the developing brain and also in primary CNS tumors. Several observations suggest that BEHAB may play a role in cell motility and have led to the hypothesis they propose to test here: that the expression of BEHAB is an important element in the invasive ability of brain tumor cells.
The first aim of this project is to determine the cellular source of BEHAB expression in brain tumor. The expression of BEHAB in cells from surgical samples of human brain tumor will be studied using in situ hybridization with methods that permit localization of BEHAB at the single cell level. In addition, brain tumors induced in rodents by ethylnitrosourea (ENU) will also be examined for BEHAB expression. The second specific aim of this project is to test whether BEHAB facilitates the invasion of tumor cells through the extracellular matrix. They will use an established in vitro invasion system to determine if single cells expressing BEHAB are more invasive than cells that do not express BEHAB. Both cells engineered to express BEHAB and those endogenously expressing the gene will be tested in this system. Because the matrix used in the in vitro invasion assay may not accurately reflect the composition of the mature brain, they will also study the ability of single cells expressing BEHAB to invade the mature brain parenchyma in the intact animal. In addition, the in vitro invasion system will be used to determine if an artificial matrix containing BEHAB enhances cell migration. If the experiments proposed here indicate that BEHAB has a role in tumor invasion, the long term goal will be to determine if functional reduction or elimination of BEHAB could slow the progression of primary brain tumor.
