Original Articles
Phakorn Tantirapan1 and Yaneen
Abstract
C-phycocyanin (c-PC) is a biliprotein found in edible blue-green algae. Its anti-cancer activity has been evidenced by many in vitro and in vivo studies. Here, the effects of c-PC on cytotoxicity and cell signaling through the apoptotic pathway were studied in a human erythromyeloid leukemia cell line (K562). Cell viability after incubation with various concentrations of c-PC was determined, and the signal transduction of the BCR-ABL fusion protein via the downstream targeting pathway, PI3K/AKT, was observed. Western blot analysis was performed to examine the levels of BCR-ABL, PI3K, AKT, and their phosphorylated derivatives in K562 cells during treatment with 100 µM cPC. The results showed that c-PC inhibits K562 cell growth in a dose-dependent manner with the half maximal inhibitory concentration (IC50) = 128.6 µM. We found that c-PC exhibits inhibitory effects on protein phosphorylation in K562 cells. Phosphorylated BCR-ABL and phosphorylated PI3K were decreased at 20 and 16 h of treatment, respectively, whereas neither the BCR-ABL nor the PI3K level was significantly changed. AKT and its phosphorylated form were decreased at 1 hr. These results indicated that anti-proliferative effects of c-PC are mediated by inactivation of BCR-ABL signaling and the downstream pathway PI3K/AKT.