wogonin and Nasopharyngeal-Neoplasms

Autophagy as well as apoptosis is an emerging target for cancer therapy. Wogonin, a flavonoid compound derived from the traditional Chinese medicine of Huang-Qin, has anticancer activity in many cancer cells including human nasopharyngeal carcinoma (NPC). However, the involvement of autophagy in the wogonin-induced apoptosis of NPC cells was still uninvestigated. In this study, we found wogonin-induced autophagy had interference on the process of apoptosis. Wogonin-induced autophagy formation evidenced by LC3 I/II cleavage, acridine orange (AO)-stained vacuoles and the autophagosome/autolysosome images of TEM analysis. Activation of autophagy with rapamycin resulted in increased wogonin-mediated autophagy via inhibition of mTOR/P70S6K pathway. The functional relevance of autophagy in the antitumor activity was investigated by annexin V-positive stained cells and PARP cleavage. Induction of autophagy by rapamycin ameliorated the wogonin-mediated apoptosis, whereas inhibition of autophagy by 3-methyladenine (3-MA) or bafilomycin A1 increased the apoptotic effect. Interestingly, this study also found, in addition the mTOR/P70S6K pathway, wogonin also inhibited Raf/ERK pathway, a variety of Akt pathways. Inactivation of PI(3) K/Akt by their inhibitors significantly induced apoptosis and markedly sensitized the NPC cells to wogonin-induced apoptosis. This anticancer effect of Akt was further confirmed by SH6, a specific inhibitor of Akt. Importantly, inactivation of its downstream molecule ERK by PD98059, a MEK inhibitor, also induced apoptosis. This study indicated wogonin-induced both autophagy and apoptosis through a variety of Akt pathways and suggested modulation of autophagy might provide profoundly the potential therapeutic effect.

Topics: Adenine; Apoptosis; Autophagy; Carcinoma; Cell Line, Tumor; Drugs, Chinese Herbal; Extracellular Signal-Regulated MAP Kinases; Flavanones; Flavonoids; Gene Expression Regulation, Neoplastic; Humans; Macrolides; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; raf Kinases; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; TOR Serine-Threonine Kinases

Wogonin, a plant flavonoid, has antitumor activity in various cancers. Dysregulation of GSK-3β has been implicated in tumorigenesis and cancer progression. In this study, we investigated the antitumor activity and the mechanistic action of wogonin in human nasopharyngeal carcinoma (NPC) cells.. The effects of wogonin on the cell survival and apoptosis in NPC cells were investigated by MTS assay, flow cytometry, and PARP cleavage assays. Pharmacological inhibitors (BIO, LiCl, and OA), or small interfering RNA (siRNA) were used to address the expression status of GSK-3β and the anticancer effect of ΔNp63 in NPC cells.. Wogonin was shown to induce dose-dependent cell apoptosis due to the induction of sub-G1-phase cells, PARP cleavage, and downregulation of ΔNp63, a survival factor in NPC cells. Strikingly, the apoptotic effect of wogonin involved GSK-3β inactivation via prominent inhibition of phosphorylation at Tyr216 and slightly increment of phosphorylation at Ser9, while there is no change in total GSK-3β proteins. Dysregulation of GSK-3β caused cell apoptosis was confirmed by pharmacological inhibitors (lithium chloroid, LiCl, and 6-bro-moindirubin-3-oxime, BIO). Administration of okadaic acid (OA, a protein phosphatase inhibitor) that significantly inactivated GSK-3β also induced ΔNp63 downregulation and apoptosis. Targeted silencing of ΔNp63 repressed the phosphorylation of GSK-3β at Tyr216 and sensitized NPC cells to wogonin-induced apoptosis. Furthermore, GSK-3β or PP2A inhibitors enhanced wogonin-induced apoptosis via activation of caspase 3/7.. These results indicate that GSK-3β, as well as ΔNp63, are novel targets for wogonin action and suggest that wogonin might provide a potential therapeutic option in NPC. Further in vitro and in vivo studies will help to clarify the therapeutic role of wogonin in NPC.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; Carcinoma; Cell Line, Tumor; Cell Survival; Dose-Response Relationship, Drug; Drug Delivery Systems; Flavanones; Flow Cytometry; Gene Expression Regulation, Neoplastic; Gene Silencing; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Humans; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Transcription Factors; Tumor Suppressor Proteins