PECAM1 and acute lymphoblastic leukemia: Anti-apoptotic effects of PECAM-1 have been previously reported for several types of cells under various conditions, including endothelial cells withdrawn from serum (41,44), hematopoietic cells withdrawn from GM-CSF (42) and an ALL cell line treated with UV irradiation or DNA-damaging chemotherapeutic agents VP16 and AraC (40,43).