Apoptosis inducement of bigelovin from Inula helianthus-aquatica on human Leukemia U937 cells

Inula helianthus-aquatica C. Y. Wu is a traditional medicinal plant used to treat some cancers in folk herbal medicine of Yunnan, China. Bigelovin, a sesquiterpene lactone isolated from this herb, potently inhibits the growth of a panel of eight cancer cell lines, especially in human monoblastic leukemia U937 cells with an IC₅₀ value of 0.47 μM. Characteristic morphological features of apoptosis were observed in U937 cells treated with bigelovin. Annexin V and nuclear DNA content distribution assays showed that the percentage of Annexin V positive cells increased to 8.86% (24 h) with 1 μM bigelovin treatment, and cells treated with bigelovin at this concentration apparently arrested at G₀/G₁ phase compared with the control. These data suggested that cytotoxic effect of bigelovin on U937 cells involves induction of apoptosis, and the cell cycle is arrested at G₀/G₁ phase. Copyright © 2008 John Wiley & Sons, Ltd.