FLT4 and neoplasm: Furthermore, while FLT4, KDR, UNC5A, and ADAM12 were detected in the L1T2 mouse xenografts in concert with human tumor results, we did not detect either endothelial cell marker (Prox-1 and CD34) in those grafts, which may indicate that the L1T2 cell line has lost its endothelial cell attributes in culture.