Inhibitory Effects of Diacylglyceride Phospholipids on DNA Polymerase and Topoisomerase Activities, and Human Cancer Cell Growth

Chisato      Ishimaru; Toshifumi      Takeuchi; Fumio      Sugawara; Hiromi      Yoshida; Yoshiyuki      Mizushina

Abstract

This paper describes the inhibitory activities of diacylglyceride phospholipids, such as phosphatidylcholine (lecithin), phosphatidylethanolamine (cephalin), phosphatidylserine, phosphatidylglycerol, bisphosphatidylglycerol (cardiolipin), phosphatidylinositol, and phosphatidic acid (phosphatidate) (compounds 1–7, respectively) against DNA polymerase (pol), DNA topoisomerase (topo), and human cancer cell growth. Among the compounds tested, compounds 3–7 were revealed to be potent inhibitors of animal pols: compound 4 was the strongest inhibitor, with IC50 values for different pols of 1.7 – 15 μM. Compounds 4–7 also inhibited the activity of human topo II: compound 7 was the strongest inhibitor, with an IC50 value of 20 μM. The glycerophospholipids had no effect on the activities of plant (cauliflower) pol α, prokaryotic pols, or other DNA metabolic enzymes, such as calf primase of pol α, T7 RNA polymerase, T4 polynucleotide kinase, and bovine deoxyribonuclease I. These results suggest that compounds 4–7 are selective inhibitors of animal pols and human topos. Compounds 4 and 7 also suppressed the growth of a human colon carcinoma cell line that lacked p53 (HCT116 p53-/-); their LD50 values were 63.6 and 51.1 μM, respectively, suggesting that cell growth inhibition by these compounds leads to the inhibition of pols and/or topos. From these findings, diacylglyceride phospholipids, which are present in various foods, might be effective nutrients for promoting human anti-cancer health promotion.

Keywords: Diacylglyceride phospholipids, Phosphatidylglycerol, Phosphatidic acid (Phosphatidate), Enzyme inhibitor, DNA polymerase, DNA topoisomerase, Cancer cell growth suppression