PTGS2 and leukemia: Moreover, to elucidate the possible molecular mechanisms by which actinomycetes inhibit leukemia growth, we will study COX-2 activity, a rate-limiting enzyme for the synthesis of prostaglandins that are involved in the proliferation and differentiation of several leukemia cells as well as the lipoxygenase activity, which is involved in stimulating cell division of tumor and ROS production in leukemia cells.