Inhibitory effect of phycocyanin from Spirulina platensis on the growth of human leukemia K562 cells.

Abstract

The effect of phycocyanin from Spirulinaplatensis on the growth of human chronic myelogenousleukemia-blast crisis K562 cells was studied bysemi-solid agar assay and cell viability measurement. Phycocyanin significantly inhibited the growth of K562cells in a dose-dependent manner. The IC50 value ofthe phycocyanin was 72.5 mg L-1. After the K562cells were cultured with phycocyanin for 6 days, flowcytometric assays showed that more K562 cells wereblocked to progress through S-phase and arrested at G1phase. DNA fragmentation assay indicated that therewas no ladder of DNA fragments of approximately 200-bpmultiples, indicating that apoptosis had not occurred. Western blot analysis showed that Bcl-2 protein wasexpressed, but its level remained unchanged, whereasthe expression level of c-myc increased. Thesefindings suggest that phycocyanin may be able toinhibit the growth of K562 cells by pathways otherthan apoptosis, and that changed a expression patternof the c-myc protein may be involved in such inhibition.