Drug-repositioning screening identified piperlongumine as a direct STAT3 inhibitor with potent activity against breast cancer

Abstract

Signal transducer and activator of transcription (STAT) 3 regulates many cardinal features of cancer including cancer cell growth, apoptosis resistance, DNA damage response, metastasis, immune escape, tumor angiogenesis, the Warburg effect, and oncogene addiction and has been validated as a drug target for cancer therapy. Several strategies have been employed to identify agents that target Stat3 in breast cancer but none has yet entered into clinical use. We used a high-throughput fluorescence microscopy search strategy to identify compounds in a drug-repositioning library (Prestwick library) that block ligand-induced nuclear translocation of Stat3 and identified piperlongumine (PL), a natural product isolated from the fruit of the pepper Piper longum. Piperlongumine inhibited Stat3 nuclear translocation, inhibited ligand-induced and constitutive Stat3 phosphorylation, and modulated expression of multiple Stat3-regulated genes. Surface plasmon resonance assay revealed that piperlongumine directly inhibited binding of Stat3 to its phosphotyrosyl (pY) peptide ligand. Phosphoprotein antibody array analysis revealed that PL does not modulate kinases known to activate Stat3 such as JAKs, Src kinase family members, or RTKs. PL inhibited anchorage-independent and anchorage-dependent growth of multiple breast cancer cell lines having increased pStat3 or total Stat3, and induced apoptosis. PL also inhibited mammosphere formation by tumor cells from patient derived xenografts (PDX). PL’s anti-tumorigenic function was causally linked to its Stat3-inhibitory effect. PL was non-toxic in mice up to a dose of 30 mg/Kg/day for 14 days and caused regression of breast cancer cell line xenografts in nude mice. Thus, PL represents a promising new agent for rapid entry into the clinic for use in treating breast cancer, as well as other cancers in which Stat3 plays a role.

Dealing Naturally with Stumbling Blocks on Highways and Byways of TRAIL Induced Signaling

“…Emerging evidence also suggests that Piperlongumine treated breast cancer cells did not show nuclear accumulation of phosphorylated STATs. Moreover, ligand induced and constitutively activated STATs were also significantly inhibited in Piperlongumine treated breast cancer cells (Bharadwaj et al, 2014).…”

Chikusetsusaponin IVa Butyl Ester (CS-IVa-Be), a Novel IL6R Antagonist, Inhibits IL6/STAT3 Signaling Pathway and Induces Cancer Cell Apoptosis

“…Many kinds of natural compounds have been reported to abolish IL6/STAT3 signaling through different mechanisms (31) such as targeting IL6Ra (32) or GP130 (33), directly inhibiting JAKs (34), inducing PTPase expression (35), inhibiting STAT3 translocation (36), and blocking JAK-STAT3 interaction (37). The natural antagonist of IL6R is rarely reported except for the ERBF, which is isolated from bufadienolide and sensitizes breast cancer cells to TRAIL-induced apoptosis via inhibition of STAT3/Mcl-1 pathway (38).…”

Piperlongumine Suppresses Growth and Sensitizes Pancreatic Tumors to Gemcitabine in a Xenograft Mouse Model by Modulating the NF-kappa B Pathway

“…injection); and (iv) piperlongumine and gemcitabine, following the same schedule of individual drugs. The doses of piperlongumine and gemcitabine selected for this experiment were based on preliminary experiments and previous studies (26,34,42). The mice were closely monitored for 24 days, then euthanized, and the tumors were removed.…”

“…This alkaloid was also found to sensitize tumors to chemotherapeutic agents such as cisplatin and paclitaxel (26,27). Piperlongumine inhibits the growth of tumor cells with no apparent toxicity in nonmalignant human cells (32)(33)(34). The antitumor effect of piperlongumine may be associated with its ability to target the cellular stress response through direct inhibition of Glutathione S-transferase pi 1 (GSTP1; ref.…”

“…The antitumor effect of piperlongumine may be associated with its ability to target the cellular stress response through direct inhibition of Glutathione S-transferase pi 1 (GSTP1; ref. 33), activate ERK signaling (31,35), target p38 signaling (36), suppress STAT3 phosphorylation (34), generate reactive oxygen species (ROS; Figure 1. Piperlongumine suppresses the proliferation and potentiates the apoptotic effects of gemcitabine in pancreatic cancer cells in vitro.…”