It is proposed that prostaglandin J3 (PGJ3) isomerises to prostaglandin δ12-PGJ3 (δ12-PGJ3) (Fitzpatrick et al. 1983, Shibata et al. 2002). EPA supplementation to mice resulted in enhanced endogenous production of δ12-PGJ3, which was found to possess chemoprotective activity against myleoid leukemia, ablating leukemia stem cells in mice (Hedge et al. 2011, Finch et al. 2015).