Advanced stage nasopharyngeal carcinoma (NPC) has a poor prognosis. Triptonide ("TN") is a small molecule monomer extract from the ancient Chinese herb Tripterygium wilfordii Hook. We show that TN, at nanomolar concentrations, potently inhibited survival and proliferation of multiple established and primary human NPC cells. TN induced NPC cell cycle arrest and apoptosis activation. NPC cell migration and invasion were also inhibited by TN. Importantly, TN was non-cytotoxic to nasopharyngeal epithelial cells. TN treatment in NPC cells disrupted LncRNA THOR ("Lnc-THOR")-IGF2BP1 association, causing depletion of Lnc-THOR and downregulation of IGF2BP1 mRNA targets (Myc, IGF2 and Gli1). Lnc-THOR or IGF2BP1 knockout by CRISPR/Cas9 gene-editing methods mimicked and abolished TN's actions in NPC cells. Conversely, ectopic Lnc-THOR overexpression inhibited TN-induced cytotoxicity in NPC cells. Significantly, Lnc-THOR, IGF2BP1 and its mRNA targets are elevated in human NPC tissues and cells, but almost undetectable in nasopharyngeal epithelial tissues and cells. In vivo, intraperitoneal TN administration significantly inhibited subcutaneous NPC xenograft growth in mice. Similarly, Lnc-THOR-knockout HONE-1 xenografts grew significantly slower than control tumors. Thus, TN inhibits human NPC cell growth in vitro and in vivo via disrupting Lnc-THOR-IGF2BP1 signaling.
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