Hyaluronic Acid Inhibitor 4-Methylumbelliferone Activates the Intrinsic Apoptosis Pathway in K562 Chronic Myelogenous Leukemia Cells

Background: As an inhibitor of hyaluronic acid (HA) synthesis, 4-methylumbelliferone (4-MU) has been shown to induce apoptosis of various types of cancer cells. However, the potential impact of 4-MU-induced apoptosis on leukemia cells via modulation of HA is not well-known. Materials and Methods: We examined apoptosis of chronic myelogenous leukemia (CML) cells after treatment with 4-MU using annexin V/propidium iodide (V/PI) analysis and poly (ADP-ribose) polymerase (PARP) cleavage. We further examined the mechanisms of 4-MU-induced apoptosis by measuring mitochondrial membrane potential and reactive oxygen species generation. Using real-time PCR, and western blot analysis we examined signaling pathways involved in apoptosis. Results: The current study demonstrated that treatment of CML cells with 4-MU led to induction of apoptosis through PARP cleavage and loss of mitochondria membrane potential. Mechanistically, 4-MU led to increased p53 mRNA expression, elevated cytoplasmic protein levels of cytochrome c and B-cell lymphoma-2-associated X (BAX) and reduced levels of B-cell lymphoma-2 (BCL2) expression. Addition of exogenous soluble HA was able to protect 4-MU-exposed cells from apoptosis. Conclusion: Our findings suggest that 4-MU induces apoptosis in CML cells by activating components associated with the intrinsic apoptosis pathway.