Antitumor bioactivity of porphyran extracted from Pyropia yezoensis Chonsoo2 on human cancer cell lines

BACKGROUND Pyropia yezoensis , rich in porphyran, is a medicine-edible red alga. In the present study, the physicochemical characteristics, conformational states and antitumor activities of a novel porphyran extracted from the high-yield algal strain Pyropia yezoensis Chonsoo2 and its two degraded derivatives by gamma irradiation were investigated. RESULTS Pyropia yezoensis porphyran is a water-soluble, triple-helical sulfated hetero-galactopyranose, named PYP. PYP was degraded by gamma irradiation at 20 kGy and 50 kGy, giving two low molecular weight derivatives comprising PYP-20 and PYP-50, respectively. PYP with a higher molecular weight has a solution conformation different from PYP-20 and PYP-50. Three porphyrans had no toxicity in normal human liver cells (HL-7702) and showed antitumor effects on Hep3B, HeLa and MDA-MB-231. They had better antitumor against HeLa cells, exhibiting a similar inhibition ratio compared to 5-fluorouracil, with PYP especially exhibiting a higher inhibition ratio than 5-fluorouracil. With respect to HeLa cells, the different antitumor activities might be related to porphyran molecular weight and solution conformation. Furthermore, the HeLa cell cycle was blocked in the G2/M phase after PYP treatment, leading to cell proliferation inhibition. The induction of cell cycle arrest was related to the changes in the expression of p21, p53, Cyclin B1 and cyclin-dependent kinase 1. CONCLUSION Pyropia yezoensis porphyran, as applied to medicine and functional food, could potentially be used as a non-toxic natural adjuvant in cancer therapy. © 2019 Society of Chemical Industry