XWH - TITLE : PRINCIPAL INVESTIGATOR : CONTRACTING ORGANIZATION : REPORT DATE : TYPE OF REPORT : Annual PREPARED

Oncogenic activation of the ETS Related Gene (ERG) in humans was originally identified insubsets of Ewing sarcomas, myeloid leukemias and, recently, in the majority of prostatecancers. Expression of human ERG protein and consequently its functions in normal anddisease states needs to be better understood in light of its suggested role in cell differentiationand proliferation. Here, we analyzed temporal and spatial expression of the Erg (mouseprotein) by immunohistochemical analysis during mouse embryonic and adult organogenesisusing a highly specific ERG monoclonal antibody (ERG MAb). This study establishes wide-spread immunolocalization of Erg protein in endothelial cells and restricted expression inprecartilage and hematopoietic tissues. Intriguingly, Erg is not expressed in any epithelial tissueincluding prostate epithelium, or in infiltrating lymphocytes that are occasionally seen in theprostate environment, a common site of tumors with ERG rearrangements and unscheduledERG expression. These findings will further aid in investigations of Erg functions in normal anddisease conditions.