grifolin and Nasopharyngeal-Neoplasms

The death toll associated with cancer worldwide is constantly on the increase. Efforts to combat and treat the different forms of this disease is also evolving. Nasopharyngeal carcinoma (NPC) is a lethal form of cancer, which is prevalent in Southern China, that is normally treated by using radiotherapy. Here, we will review products obtained from natural sources that have potential cytotoxic and apoptotic properties against NPC. These include grifolin, dihydroartemisinin, luteolin, honokiol, indole-3-carbinol, caffeic acid phenethyl ester, 6-O-angeloylenolin, cucurbitacin E, genistein, helenalin, celastrol, coronarin D, quercetin, trans-cinnamaldehyde, 5'-epimer episilvestrol, silvestrol, arnicolide D, brevilin A, and baicalin hydrate. Ethyl acetate extracts of Wedelia chinensis and aqueous extracts of Ajuga bracteosa are also included although the bioactive compounds involved have yet to be identified. The known mechanism of action of these products is discussed. It is anticipated that one or more of these substances may provide the general population with alternative and cost-effective ways to combat this fatal disease.

Topics: Apoptosis Regulatory Proteins; Biological Products; Cell Cycle Checkpoints; Herpesvirus 4, Human; Humans; Nasopharyngeal Neoplasms; Reactive Oxygen Species; Signal Transduction; Terpenes; Virus Activation

Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been shown to inhibit the growth of some cancer cell lines in vitro by induction of apoptosis in previous studies of our group. However, the mechanisms of action are not completely understood. An apoptosis-related gene expression profiling analysis provided a clue that death-associated protein kinase 1 (dapk1) gene was upregulated at least twofold in response to grifolin treatment in nasopharyngeal carcinoma cell CNE1. Here, we further investigated the role of DAPK1 in apoptotic effect induced by grifolin. We observed that protein as well as mRNA level of DAPK1 was induced by grifolin in a dose-dependent manner in nasopharyngeal carcinoma cell CNE1. We found that grifolin increased both Ser392 and Ser20 phosphorylation levels of transcription factor p53 protein, which could promote its transcriptional activity. Moreover, induced by grifolin, the recruitment of p53 to dapk1 gene promoter was confirmed to enhance markedly using EMSA and ChIP assays analysis. The involvement of DAPK1 in grifolin-induced apoptosis was supported by the studies that introducing siRNA targeting DAPK1 to CNE1 cells remarkably interfered grifolin-caused apoptotic effect as well as the activation of caspase-3. Grifolin induced upregulation of DAPK1 via p53 was also observed in tumour cells derived from human breast cancer and human colon cancer. The findings suggest that upregulation of DAPK1 via p53-DAPK1 pathway is an important mechanism of grifolin contributing to its ability to induce apoptotic effect. Since growing evidence found a significant loss of DAPK1 expression in a large variety of tumour types, grifolin may represent a promising candidate in the intervention of cancer via targeting DAPK1.

Topics: Antineoplastic Agents; Apoptosis; Apoptosis Regulatory Proteins; Biological Products; Blotting, Western; Breast Neoplasms; Calcium-Calmodulin-Dependent Protein Kinases; Carcinoma; Cell Line, Tumor; Colonic Neoplasms; Death-Associated Protein Kinases; Female; Humans; Nasopharyngeal Carcinoma; Nasopharyngeal Neoplasms; Phosphorylation; Terpenes; Tumor Suppressor Protein p53; Up-Regulation

Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been shown to induce G1 phase cell-cycle arrest in tumor cells in previous studies of our group. However, the mechanisms of action are not completely understood. Our group further demonstrated that grifolin upregulates death-associated protein kinase 1 (DAPK1) in nasopharyngeal carcinoma cells (NPCs). Here, we found that grifolin induced dephosphorylation of DAPK1 (Ser308) to activate DAPK1 and subsequent phosphorylation of its potential downstream effector p21 (Thr145) in nasopharyngeal carcinoma cell CNE1. Inhibition of DAPK1 by introducing siRNA targeting DAPK1 reversed the grifolin- induced phosphorylation of p21. Furthermore, we confirmed that grifolin increased the half-life of p21 and promoted its stability. Flow cytometry analysis demonstrated that DAPK1 was involved in grifolin-induced G1 phase arrest in CNE1 cells. The similar effects induced by grifolin and mechanism beneath were identified in another nasopharyngeal carcinoma cell HONE1. In addition, we observed that grifolin promoted the protein-protein interaction of DAPK1 and ERK1/2 to prevent ERK1/2 nucleolus translocation. Our findings indicate that DAPK1 plays a crucial role in the induction of cell-cycle arrest at G1 phase by grifolin. Grifolin might represent a promising candidate in the prevention and intervention of cancer by targeting DAPK1 signaling to induce cell cycle G1 phase arrest.

Topics: Active Transport, Cell Nucleus; Antineoplastic Agents; Apoptosis Regulatory Proteins; Biological Products; Calcium-Calmodulin-Dependent Protein Kinases; Cell Line, Tumor; Cell Nucleolus; Cyclin-Dependent Kinase Inhibitor p21; Death-Associated Protein Kinases; G1 Phase Cell Cycle Checkpoints; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nasopharyngeal Neoplasms; Phosphorylation; Protein Stability; Terpenes