Norcantharidin (NCTD), a chemically modified form of cantharidin, is a potential anticancer drug. This study investigated the effect of NCTD on anoikis in CT26 colorectal adenocarcinoma cells. NCTD treatment of CT26 cells showed a dose-dependent and time-dependent decrease in viability and cell proliferation. Growth inhibition was accompanied by cell cycle arrest in the S and G2/M phases. Mitogen-activated protein kinase expression, assayed by Western blot, was unchanged except for Jun-N-terminal kinase (JNK). At 24 h of treatment with 0-20 micromol/l NCTD, JNK expression increased at 24 h, but then decreased at 48 h; in contrast, the phosphorylated JNK levels markedly increased. JNK inhibitor (SP600125) in the culture effectively blocked NCTD-induced cytotoxicity and detachment of cells. CT26 cells treated with NCTD not only displayed inhibited cell adhesion and down-expression of integrin beta1, but also changed from being shuttle-shaped to round, the latter cells being more susceptible to anoikis-mediated apoptosis. Flow cytometric assay of the DNA content in NCTD-treated CT26 cells at 24 and 48 h showed a marked increase in the sub-G1 level, indicating that NCTD induced apoptosis. NCTD inhibited the viability of CT26 cancer cells preferentially over normal bone marrow and mononuclear cells. NCTD inhibits CT26 cancer cells by blocking proliferation and inducing anoikis-mediated apoptosis, a process that might be regulated by JNK activation.

Curcumin is a common food ingredient derived from the plant Curcuma longa and is a potent drug against tumorigenesis. Both insulin-like growth factor binding protein-5 (IGFBP-5) and CCAAT/enhancer-binding protein a (C/EBPa) are suppressors of head and neck carcinogenesis. We identified curcumin as an inducer of IGFBP-5 expression in multiple types of oral keratinocytes; furthermore, curcumin induces IGFBP-5 promoter activity in SAS oral cancer cells. Promoter deletion mapping identified a region (nt 271 to nt 259 relative to the transcription start site) as containing a C/EBPa-binding element that is indispensable for curcuminmediated IGFBP-5 upregulation. Chromatin immunoprecipitation assays revealed that in vivo binding of C/EBPa to this region was remarkably increased in the presence of curcumin. Curcumin increased nuclear C/EBPa expression and IGFBP-5 expression through p38 activation and this was abrogated by SB203580 treatment. Furthermore, MKK6 expression activated p38 and C/EBPa, increasing IGFBP-5 promoter activity and expression. Finally, curcumin-induced IGFBP-5 expression is associated with the suppression of xenograft tumorigenesis in mice due to oral cancer cells. We conclude that curcumin activates p38, which, in turn, activates the C/EBPa transactivator by interacting with binding elements in the IGFBP-5 promoter. The consequential upregulation of C/EBPa and IGFBP-5 by curcumin is crucial to the suppression of oral carcinogenesis.Insulin-like growth factors (IGFs) that bind IGF receptors (IGFRs) with high affinity play important roles in regulating cell phenotypes, including proliferation, differentiation, migration and apoptosis. Diferuloylmethane (Curcumin), found in significant amounts in the Indian spice turmeric, is a polyphenol derived from the plant Curcuma longa and is a common food ingredient across the world. 8,9 Accumulated evidence has indicated that this polyphenol can be used to both prevent and treat cancer. 10,11 Curcumin exhibits cancer chemopreventive effects in a range of animal models of chemical carcinogenesis, including those resulting in head and neck squamous cell carcinoma (HNSCC) and OSCC. 12,13 This compound also has anti-oxidative effects, anti-inflammatory effects, anti-

No abstract