sentences:  Consequently, these three cyclopentenone-PGs and the two epoxyisoprostanes are suggested to be models for the development of novel anti-inflammatory and anti-cancer drugs.The cyclopenentone prostaglandins are structurally and functionally related to a subset of isoprostanes viz., two cyclopentenone isoprostanes, 5,6-epoxyisoprostane E2 and 5,6-epoxisoprostane A2.In cells, COX-1 and COX-2 metabolize arachidonic acid to PGH2 which is then converted to PGE2 by any one of three isozymes, PTGES, PTGES2, and PTGES3 or, alternatively, to PGD2 by either of two enzymes, a glutathione-independent synthase termed lipocalin-type Prostaglandin D2 synthase (PTGDS or L-PGDS) and a glutathione-dependent hematopoietic-type H-PGDS or PTGDS2; the COX's also metabolizes dihomo-gamma-linolenic acid to PGH1 which is metabolized by one of the three PTGES isomzymes to PGE1 (see eicosanoid#Prostanoid pathways).