Cuscuta campestris induces apoptosis by increasing reactive oxygen species generation in human leukemic cells

Cuscuta campestris or common dodder is a holoparasitic plant that has been valorized for treatment of liver injury and cancer prevention in traditional medicine. Recently, extract of C. campestris had shown moderate antimicrobial properties and cytotoxic effects. In this study, we examined the level of cellular oxidants, cytotoxicity, apoptosis and differentiation induced by hydroalcoholic extract of C. campestris (CCE) (12.5-200 µg/ml), as well as arsenic trioxide (As₂O₃, 50 µM), in human leukemic (HL60 and NB4) and normal polymorph nuclear cells after 72 hr treatment.

Resazurin assay was used to determine cell viability following treatment with C. campestris. Intracellular reactive oxygen species (ROS) and apoptotic cells were measured by fluorimetry using carboxy 2', 7'-dichlorofluorescein diacetate and propidium iodide (PI), as staining reagents, respectively. The differentiation of leukemic cells was evaluated by Giemsa staining and nitro blue tetrazolium (NBT) reduction.

C. campestris inhibited cell viability with IC₅₀ values of 23.9 µg/ml for HL60 and 60.3 µg/ml for NB4 cells after 72 hr treatment. ROS formation was also concentration-dependently increased following treatment with C. campestris. In addition, the number of apoptotic cells significantly increased to 88.4% and 62.3% in CCE (200 µg/ml)-treated HL60 and NB4 cells, respectively, which was higher than that of As₂O₃ (50 µM)-treated leukemic cells (p<0.001). Nonetheless, C. campestris did not induce differentiation of leukemic cells towards granulocytic pattern.

The present study demonstrated that C. campestris induced apoptosis through ROS production without having differential effect on leukemic cells, in concentration- and time-dependent manners. Understanding of precise signaling pathway by which C. campestris induce apoptosis, needs further research.