Glioblastoma multiforme, the most malignant grade of glioma, represents up to 30% of all primary brain tumors in veterans. Although advances in surgical techniques have allowed removal of up to 99% of the visible tumor;the tumor always recurs due to aggressive tumor cell growth beyond the primary tumor focus or margin. The understanding of the molecular events that underly the dispersion of the cells of these tumors would have enormous clinical potential and impact on this universally fatal disease. Recently, using a state-of-the-art technologies, e.g. digital karyotyping, we mapped the genomic landscape of primary GBM tumors at a high resolution and identified the isolated loss of expression of the Adherens Junctional Associated Protein 1 (AJAP1) gene, located on chromosome 1p36.32, as a frequent molecular event in GBMs. Our goal in this proposal is to explore the clinical implications of the loss of expression of AJAP1 in a large set of GBM primary tumors, to gain insights into the mechanisms underlying its loss, to understand its role in tumor cell dispersion, and to explore the mechanisms by which it modulates tumor cell migratory activity. The rationale for these studies derive from the following observations: 1) AJAP1 is located in a hotspot region on chromosome 1p36.3 that is frequently lost in GBM, 2) AJAP1 encodes for a key transmembrane protein involved in formation of a protein complex that plays an important role in cell-cell and cell-extracellular matrix interactions, 3) in preliminary studies, we demonstrated loss of AJAP1 expression in up to 25% of primary GBM tumors, 4) using several GBM cell lines, we provided preliminary evidence that hypermethylation may be an important mechanism underlying the loss of AJAP1 expression in GBM cells, 5) we observed a significant correlation between AJAP1 loss and poor survival in GBM patients, and 6) our preliminary data showed that loss of AJAP1 expression increases tumor cell migration, and its reconstituion decreases tumor cell invasiveness. Based on these critical observations, we hypothesize that AJAP1 functions as a novel dispersion-associated cell membrane protein in GBM cells and that loss or downregulation of its expression increases the migratory potential of these tumor cells and contributes to the aggressive clinical behavior of GBM.
Specific aim #1 will characterize mechanisms of loss of AJAP1 expression in a large number of primary GBMs with linked clinical data.
Specific aim #2 will characterize the modulation of AJAP1 expression on the migratory activity of GBM cells in vitro and in vivo.
Specific aim #3 will characterize the molecular mechanism(s) underlying the effects of AJAP1 loss on tumor cell migration in GBM. We believe that the results of these studies will facilitate the development of molecular-based therapies that target mechanisms of tumor cell migration in GBM and could provide novel adjunctive therapeutic modalities to surgery.
Over the past decade, more than 150,000 veterans were diagnosed with a brain tumor. The most common primary brain tumor was GBM. GBM patients die within about 1 year, even with the most aggressive medical care known to mankind. Any therapeutic breakthrough will restore years of human life and decrease millions of dollars in healthcare expenditures. Molecular-based, gene pathway specific cancer therapies are becoming an increasing reality and will be necessary for curing GBM. We have identified a potential novel dispersion-related gene for GBM that plays a critical role in the high migratory and invasive nature of GBM tumor cells.