Higher Expression of Cytochrome-c and Caspase-3 in the Primary Acute Lymphoblastic Leukemic Cells with Negative Expression of VEGF and Its Receptors Than with Positive Expressed Cells under VP16 Induction.

Flow cytometry and immunofluorescent staining were employed to examine the apoptosis signals, cytochrome-c and Caspase-3, in the primary leukemia cells with or without expression of VEGF and its receptors and normal healthy donor’s lymphocytes. We found that primary leukemic cells and normal lymphocytes didn’t secrete Cyt-c from mitochondria and no caspase-3 activation without the treatment of VP16. Instead, after incubation with VP16 (30mg/L) for 8 hours, normal lymphocytes and most of de novo leukemia cells secreted Cyt-c into cytosol from mitochondria and had the activation of caspase-3 in the cellular plasma. However, primary leukemia blasts with higher expression of VEGF and its receptors revealed lower secretion of Cyt-C and down-regulated activation of Caspase-3. Results showed that Cyt-c secretion and Caspase-3 activation were prone to occur in the VEGF negatively expressed blasts than positively expressed cells. This indicates that lower secretion of Cyt-c from mitochondria and inactivation of Caspase-3 are two of the pivotal mechanisms of anti-apoptosis for refractory leukemia clone with highly expressed VEGF and its receptors.