Bleomycin is an antineoplastic drug that has recently been employed to treat haemangiomas, the most common vascular
tumors of infancy, with very good results. To better understand the mechanism of bleomycin in accelerating
haemangioma regression, we have investigated the effects of the drug on vascular tumor inducing endothelial cells
(sEnd.2 cells). Cell growth studies were undertaken using crystal violet staining, while morphological studies were
undertaken employing transmission electron microscopy. The cells were analyzed for possible apoptosis employing flow
cytometry. The expression of Bcl-2 and p53 were investigated using Western blot analysis. In addition, the production
of vascular endothelial growth factor was measured using ELISA. Results showed that bleomycin inhibited the growth
of these endothelial cells, even in the presence of vascular endothelial growth factor, a proangiogenic growth factor.
Further, there was increased endothelial cell apoptosis, as evidenced by morphological analysis, increased acridine
orange staining of cell nuclei and annexin V staining. Apoptosis was associated with an increase in the expression of
p53 and a decrease in the expression of the antiapoptotic protein Bcl-2.