Piperlongumine Induces Reactive Oxygen Species (ROS)-dependent Downregulation of Specificity Protein Transcription Factors

Piperlongumine is a natural product found in the plant species Piper longum and this compound exhibits potent anticancer activity in multiple tumor types and has been characterized as an inducer of reactive oxygen species (ROS).  Treatment of Panc1 and L3.6pL pancreatic, A549 lung, 786-O kidney, and SKBR3 breast cancer cell lines with 5-15 μM piperlongumine inhibited cell proliferation and induced apoptosis and ROS, and these responses were attenuated after cotreatment with the antioxidant glutathione.  Piperlongumine also downregulated expression of Sp1, Sp3, Sp4 and several pro-oncogenic Sp-regulated genes including cyclin D1, survivin, cMyc, epidermal growth factor receptor (EGFR) and hepatocyte growth factor receptor (cMet), and these responses were also attenuated after cotreatment with glutathione.  Mechanistic studies in Panc1 cells showed that piperlongumine-induced ROS decreased expression of cMyc via an epigenetic pathway and this resulted in downregulation of cMyc-regulated microRNAs (miRs)-27a, miR-20a and miR-17 and induction of the transcriptional repressors ZBTB10 and ZBTB4.  These repressors target GC-rich Sp binding sites to decrease transactivation.  This pathway observed for piperlongumine in Panc1 cells has previously been observed for other ROS-inducing anticancer agents and shows that an important underlying mechanism of action of piperlongumine is due to downregulation of Sp1, Sp3, Sp4 and pro-oncogenic Sp-regulated genes.

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