Mechanism Study Of Apoptosis Induced By Microcystis Phycocyanin-mediated Photodynamic Therapy In Liver Cancer

Phycocyanin (PC) is the major light harvesting biliprotein from Spirulina platensis etc. It is composed of two subunits—αandβsubunit, and normally exist with (αβ)3 hexamer and (αβ) 6 hexamer at room temperature. It is a water soluble, non-toxic fluorescent protein pigment with potent anti-inflammatory, anti-oxidant and even anticancer properties.Phycocyanin-mediated photodynamic therapy (PDT) was mostly used to anti-cancer study. And photosensitizer phycocyanin was usually purified from Spirulina platensis etc. This study was to explore the possibility of which phycocyanin eliminated microcystin was obtained from Microcystis (MC-PC), and to investigate possible mechanism associated with the apoptosis induced by Microcystis phycocyanin-mediated PDT (MC-PC-PDT) in HepG2 liver cancer cells. The result manifested MC-PC-PDT could inhibit HepG2 proliferation effectively at the concentration not less than 25μg/mL and cause HepG2 cells apoptosis visibly. In addition, the treatment could result in ROS accumulation which was increased greatly under the condition of 200μg/mL MC-PC for 16 h. MC-PC at 200μg/mL had the most obvious effect on mitochondrial transmembrane potential (△Ψm) collapse. Cell cycle G2/M arrest was observed after the same treatment. Blocking ROS accumulation with ROS scavengers partially suppressed△Ψm loss and cell cycle G2/M arrest, indicating that ROS accumulation play a crucial role in apoptosis induced by MC-PC-PDT. Facilitating ROS generation and finally leading to mitochondria damage, meanwhile arresting G2/M phase may be the apoptosis mechanism of MC-PC-PDT.