a member of the Thymelaeaceae family of Iranian medicinal plants. The presentation also covered signaling pathways involved in 3-HK-induced apoptosis and in the differentiation of the U937 human leukemic cell line.

Yazdanparast showed a series of slides that demonstrated the anti-proliferative activity of the plant. In one study, for example, the researchers induced breast tumors in rats, treated them with a daily dose of the crude extract, and found substantial tumor suppression. When they evaluated the biological activity of 3-HK versus that of the crude extract with a battery of cell lines, they found that the effects of the chemical and of the crude extract were similar (see Figure 5-1). Importantly, they found that the effect of 3-HK was irreversible and that it showed its effect on proliferating cells but not on resting cells. The latter finding led the researchers to investigate the signaling pathways that are influenced by 3-HK.

Yazdanparast showed a number of slides that illustrated the results of studies concerning the cause of the cell death and distinguishing between adherent cells and suspended cells. The U937 cell line reacted in two different ways to 3-HK: some of the cells went to apoptosis, and some of

FIGURE 5-1 Effects of 3-hydrogenkwadaphnin (3-HK) and crude extract from Dendrostellera lessertii on cell proliferation.

SOURCE: R. Yazdanparast, University of Tehran.