PTGS2 and cancer: Chemotherapeutics including DOX can upregulate cyclooxygenase-2 (COX-2), a key enzyme for the biosynthesis of prostaglandin E2 (PGE2), and promote the release of PGE2, which provokes the quiescent CSCs to proliferate and also activates dedifferentiation of bulk tumor cells to CSC-like cells leading to enhanced cancer stemness.