Effect of Thrombospondin-1 on Apoptosis of Human Megakaryocytic Leukemia Cells

Background: Thrombospondin 1 (TSP-1) is an extracellular matrix protein that interacts with a wide array of ligands including cell receptors, growth factors, cytokines, and proteases to regulate various physiological and pathological processes. TSP-1 induces apoptosis of endothelial and cancer cells via its receptor CD36. This study was to investigate the effect of TSP-1 on apoptosis of human megakaryocytic leukemia cell line Meg-01 and its possible mechanism.

Methods: The expression of CD36 antigen in Meg-01 cells was detected by flow cytometry and immunocytochemistry. Meg-01 cells were cultured for 48 hours with TSP-1 and CD36 antibody FA6-152 at different concentrations, to investigate the effect of TSP-1 on the growth of megakaryocytes. The early apoptosis and the activity of the apoptotic protease caspase-3 were detected by flow cytometry. Bone marrow cells of mice were cultured for CFU-MK and stained with acetylcholine to detect the differentiation of megakaryocytes.

Results: CD36 antigen was detected on the surface of Meg-01 cells by flow cytometry and immunocytochemistry. TSP-1 (5 μg/mL) inhibited the proliferation of Meg-01 cells, but not M-07e cells (CD36 ^-). After the addition of CD36 antibody FA6-152 (5, 10 and 25 μg/mL), the inhibitory effect of TSP-1 was significantly reduced. TSP-1 (2.5, 5 and 7.5 μg/mL) exerted a pro-apoptotic effect by increasing the expression of Annexin V (P<0.01) and caspase-3 activation (P<0.01). Addition of FA6-152 (25 μg/mL) can significantly reduce the apoptosis induced by TSP-1 in Meg-01 cells. In addition, TSP-1 (5, 10 and 25 μg/mL) repress the formation of CFU-MK in mouse bone marrow cells, while β-TG did not. This repression was relieved efficiently by FA6-152 (25 μg/mL).

Conclusion: TSP-1 could inhibit the proliferation of Megakaryocyte cell line Meg-01 cells, and induce it`s apoptosis. TSP-1 may induce apoptosis of Meg-01 cells via CD36 or caspase-3, which provides a potential new drug choice for clinical treatment of megakaryocytic leukemia.