Antitumor function and mechanism of phycoerythrin from porphyra haitanensis

Abstract

The anti-tumor effect of R-Phycoerythrin (R- PE) from Porphyra haitanensis was studied using cell line HeLa as an in vitro model and Sarcoma-180 (S180) tumor-bearing mice as an in vivo model. The results showed that the combination treatment of R-PE and photodynamic therapy PDT) signifi cantly inhibited the growth of HeLa cells up to 81.5%,with a fair dose-effect relationship,but did not inhibit endothelial cells. The annexin v-fi tc/PI fl uorescence staining experiments demonstrated that at doses between 0~60μg/mL,apoptosis cells and later stage apoptosis cells or necrosis cells increased signifi cantly as the R-PE dosage increased. DNA electrophoresis showed that after R-PE+PDT treatment of HeLa cells for 24 hours,a light "smear" band between 100~400bp appeared to indicate the degradation of genomic DNA. The QRT-PCR results showed that R-PE+PDT treatment increased caspase-3 and caspase-10 gene expression and decreased the Bcl-2 gene expression level signifi cantly as the R-PE dose increased,i mplying that R-PE promoted HeLa cell a poptosis. Compared with untreated S180 tumor-bearing mice,R-PE injection signifi cantly inhibited the growth of S180 in tumor-bearing mice up to 41.3% at a dose of 300mg·kg-1. Simultaneously,the signifi cant increase of superoxide dismutase (SOD) activity in serum (p < 0.01) and the decrease of the malondialdehyde (MDA) level in liver suggests that R-PE improved the anti-oxidant ability of the S180 t umor-bearing mice,which may related to its antitumor effect. In addition,the R-PE caused a significant increase (p < 0.05) in the spleen index and thymus index,and a significant increase (p < 0.01) in lymphocyte proliferation,NK cell kill activity and the TNF-α level in the serum of S180 tumor-bearing mice. These results strongly suggest that the antitumor effect of R-PE from Porphyra haitanensis functioned by increa sing the immunity and antioxidant ability of S180 tumor-bearing mice,promoting apoptosis by increasing protease gene expression and TNF-α secretion.