Betulin as an antitumor agent tested in vitro on A431, HeLa and MCF7, and as an angiogenic inhibitor in vivo in the CAM assay

Abstract

Betulin, an important compound found in birch tree bark, can be converted to betulinic acid, an important pharmacological substance. Betulin has recently been reported as a cytotoxic agent for several tumor cell lines and as an apoptotic inductor. Angiogenesis is a key process involved in tumor metastasis and in developing tumor resistance to cytotoxic therapy. There are little data on betulin as an anti angiogenic agent. This preliminary study aimed to evaluate the cytotoxic effect of betulin on three cancer cell lines: HeLa (cervix adenocarcinoma), MCF7 (breast adenocarcinoma) and A431 (skin epidermoid carcinoma), and the apoptotic mechanism, as well as the implication in the capillary formation of the chicken embryo chorioallantoic membrane. The analysis consisted in the interpretation of the MTT assay and fluorescence double staining with Hoechst dye 33258 and propidium iodide, while the angiogenic effect was evaluated using morphological and immunohistochemical techniques. The antitumor activity is revealed by the double fluorescence staining, indicating that at higher concentrations, the cell membrane permeability is enhanced, while at lower concentrations there is evidence for nuclear fragmentation. In what concerns its effect on the process of blood vessel formation, betulin induced the reduction of newly formed capillaries, especially in the mesenchyme, possible through targeting the normal function of endothelial cells. In vitro results proved the superior specificity of betulin on cervical cancer cells, followed by skin cancer cells.