Cyclooxygenase-2: A Role in Cancer Stem Cell Survival and Repopulation of Cancer Cells during Therapy

Figure 2

Schematic representation of apoptosis-mediated tumour cell repopulation. In tumours damaged by cytotoxic therapies apoptotic cells activate caspase-3 and caspase-7 through either intrinsic pathways, involving Apaf and caspase-9 activation, or extrinsic pathways, involving caspase-8 activation. Activated caspase-3 and caspase-7 activate calcium-independent phospholipase A2 (iPLA₂), which increases the synthesis and release of arachidonic acid. Arachidonic acid is then converted into PGH₂ by COX-1 and COX-2, which is subsequently converted into PGE₂ by the enzyme PGE₂ synthase. PGE₂ stimulated cancer stem cell proliferation and tumour repopulation (figure was adapted from [39] with the permission of Professor Li).