Consistent with the in vitro findings, decreased PP2A phosphatase activity and disruption of the PP2A heterotrimeric complex were also observed in both primary transgene-positive TG(+) mouse hemangioma endothelial cells (TG(+) HEC cells) and human proliferating phase hemangioma endothelial (human HEC-P) cells, but not in transgene-negative TG(−) mouse normal vascular endothelial cells (TG(−) NEC cells) and human involuting phase hemangioma endothelial (human HEC-I) cells. The gene discussed is PTPA; the disease is hemangioma.