Euphorbia tirucalli is a long-established treatment for a wide variety of cancers. However, the mechanism of its anticancer effect is yet to be elucidated. In the present study, we examined the anticancer effect of euphol, a tetracyclic triterpene alcohol isolated from the sap of Euphorbia tirucalli, in T47D human breast cancer cells. Following the treatment of cells with different doses of euphol for 24, 48 and 72 h, the cell proliferation, cell cycle, and mRNA and protein levels of cell cycle

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... regulatory molecules were analyzed, respectively. Treatment of the cells with euphol resulted in decreased cell viability, which was accompanied by an accumulation of cells in the G1 phase. Further studies demonstrated that euphol treatment downregulated cyclin D1 expression and the hypophosphorylation of Rb. Furthermore, this effect was correlated with the downregulation of cyclin-dependent kinase 2 (CDK2) expression and the upregulation of the CDK inhibitors p21 and p27. Reduced expression levels of cyclin A and B1 were also observed, corresponding to the decreased distribution of cells in the S and G2/M phases, respectively. These findings indicated that euphol is an active agent in Euphorbia tirucalli that exerts anticancer activity by arresting the cell cycle of cancer cells.