Antitumor Activity of C-phycocyanin from Arthronema africanum (Cyanophyceae)

Pure C-phycocyanin (C-PC) was isolated from Arthronema africanum to evaluate its potential antitumor effects in vivo and in vitro. Experimental myeloid Graffi tumor in hamsters was used as a model. The cell proliferation assay showed that C-PC treatment, at concentration of 100 m g mL(-1) for 24 h, significantly inhibited the growth of Graffi tumor cells (51.4% viability). Agarose gel electrophoresis of the genomic DNA of treated cells displayed time- and concentration-dependent fragmentation pattern, typical for apoptosis. Apoptotic process was related to the increase in cellular manganese and copper/zinc superoxide dismutases and glutathione reductase activities, coupled with a low catalase activity. In vivo C-PC administration (5.0 mg kg(-1) body weight) suppressed the tumor transplantability and growth, while the mean survival time of the tumor-bearing hamsters was increased. The results revealed promising antitumor activities of A. africanum C-PC and suggested the potential of this natural biliprotein pigment for future pharmacological and medical applications. The study provided new data on the mechanism of the C-PC-induced apoptosis in which the imbalance of antioxidant enzymes that favoured hydrogen peroxide accumulation might play a leading role.