PTGS2 and leukemia: There are many diverse mechanisms by which these compounds could affect leukemias, such as inhibiting or blockage of signal transduction pathways inhibiting key enzymes, e.g., cyclooxygenase-2 activity, a rate-limiting enzyme for the synthesis of prostaglandins that are involved in the proliferation and differentiation of leukemia cells and ROS production, and lipoxygenase, which metabolizes arachidonic acid to hydroxyl eicosatetraenoic acids and leucotrienes, which suppress apoptosis and stimulate cell division of tumor.