Prostaglandin A1 (PGA1, a prostaglandin characterized by a cyclopentenone structure) has a fundamental structure common to punaglandin and clavulone, the antitumor eicosanoids discovered in marine organisms such as corals. It is well established that PGA1, which exert potent antiviral activity in several DNA and RNA virus models, induce heat shock protein (hsp)70 syntheses through cycloheximide sensitive activation of heat shock transcription factor. Antitumor prostaglandins are actively incorporated through cell membrane and control gene expression. P53 (protein 53, is a transcription factor that regulates the cell cycle and functions as a tumor suppressor) independent expression of p21 (also known as cyclin-dependent kinase inhibitor 1A or CDKN1A, is a human gene on chromosome 6 (location 6p21.2), that encodes a cyclin-dependent kinase) and gadd 45 (growth arrest and DNA-damage-inducible, alpha 45, a major breast cancer (BRCA1) target is the DNA damage-responsive gene GADD45) activation of peroxisome proliferative activated receptor gamma (PPARgamma) are involved in antitumor mechanism of these prostaglandins. At the low concentration, these prostaglandins exhibit physiological or pathological activity such as osteoblast calcification, promotion of colon cancer cell proliferation. One of the mechanisms of anti-cancer activity of prostaglandins, has been believed to be that these prostaglandins might have p53 like effect in cells lacking p53. (PMID: 7988663, 11104898)Prostaglandins are eicosanoids. The eicosanoids consist of the prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and lipoxins (LXs). The PGs and TXs are collectively identified as prostanoids. Prostaglandins were originally shown to be synthesized in the prostate gland, thromboxanes from platelets (thrombocytes), and leukotrienes from leukocytes, hence the derivation of their names. All mammalian cells except erythrocytes synthesize eicosanoids. These molecules are extremely potent, able to cause profound physiological effects at very dilute concentrations. All eicosanoids function locally at the site of synthesis, through receptor-mediated G-protein linked signalling pathways.