PTGS2 and cancer: How CA slows the growth of cancer cells in vitro and in vivo is not fully understood, but it doesnot affect the viability of primary human mammary epithelial cells(HMECs) in culture.26 Also, it does notcause systemic toxicity in animals.26 Thus,chemocoxib A provides a proof-of-concept for in vivo targeting of chemotherapeutic agents to COX-2 and represents thefirst cytotoxic COX-2 inhibitor validated for targeted tumor growthinhibition in vivo.