INTRODUCTIONColorectal cancer is the most common form of malignancy in Taiwan and the third leading cause of death from cancer, preceded only by lung and hepatic cancers. Colorectal cancer is typically treated by surgical intervention and/or chemotherapy and radiotherapy, if necessary. To date, 5-fluorouracil (5-FU) is the most commonly used anti-cancer chemotherapy drug. However, patients commonly experience resistance to the drug therefore limiting its efficiency. In this study, we measured the expression of rTSbeta in human colon cancer as a novel 5-FU resistance marker.

MATERIALS AND METHODSWe collected 172 colon cancer samples from 4 different hospitals (including 21 pairs of colon cancer biopsies and 151 pathologic slides of colon cancer). In vitro, we measured the cytotoxicity of 5-FU and 5-FU plus leucovorin in H630 and H630-1 colon cancer cell lines.

RESULTSThe results revealed that rTSbeta was expressed in 115 (66.9 %) pathology samples and that tumour expression was higher than in corresponding normal tissue. Survival rates of up to 5 years following treatment was significantly higher for patients without rTSbeta expression than for those with rTSbeta expression (P = 0.0023). In vitro, H630-1 (with rTSbeta overexpression) had significantly higher IC50 of 5-FU than did H630. IC50 of 5-FU decreased when leucovorin was added.

CONCLUSIONSResults indicate a close relationship between rTSbeta expression and resistance to the drug 5-FU in human colorectal cancer. These results provide further evidence for rTSbeta expression as a novel 5-FU resistance marker of colorectal cancer.

Biomarkers ; Cell Line, Tumor ; drug effects ; Colorectal Neoplasms ; drug therapy ; Cytological Techniques ; Drug Resistance, Neoplasm ; physiology ; Fluorouracil ; pharmacology ; therapeutic use ; Humans ; In Vitro Techniques ; Taiwan ; Thymidylate Synthase ; genetics ; metabolism

OBJECTIVETo investigate the inhibitory activities of norcantharidin (NCTD), a demethylated analogue of cantharidin, on Hep3B cells (a human hepatoma cell line) with deficiency of p53.

METHODSThe survival rate of the Hep3B cells after treating with NCTD was measured by MTT assay. Cell cycle of treated cells was analyzed by flow cytometry, and DNA fragmentation was observed by electrophoresis. The influence of inhibitors for various caspases and anti-death receptors antibodies on the NCTD-induced apoptosis in the cells was determined.

RESULTSNCTD treatment resulted in growth inhibition of Hep3B cells in a dose- and time-dependent manner. Cell cycle analysis of the cells after treatment with NCTD for 48 h shows that NCTD induced G(2)M phase arrest occurs at low concentration ([Symbol: see text] 25 μmol/L) but G(0)G(1) phase arrest at high concentration (50 μmol/L). The addition of both caspase-3 and caspase-10 inhibitors completely inhibited DNA fragmentation. Addition of anti-TRAIL/DR5 antibody significantly inhibited DNA fragmentation.

CONCLUSIONNCTD may inhibit the proliferation of Hep3B cells by arresting cell cycle at G(2)M or G(0)G(1) phase, and induce cells apoptosis via TRAIL/DR5 signal transduction through activation of caspase-3 and caspase-10 by a p53-independent pathway.

Antibodies, Neoplasm ; pharmacology ; Antibodies, Neutralizing ; pharmacology ; Apoptosis ; drug effects ; Bridged Bicyclo Compounds, Heterocyclic ; pharmacology ; Carcinoma, Hepatocellular ; enzymology ; pathology ; Caspase 10 ; metabolism ; Caspase 3 ; metabolism ; Caspase Inhibitors ; pharmacology ; Cell Cycle Checkpoints ; drug effects ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; DNA Fragmentation ; drug effects ; Humans ; Immunohistochemistry ; Liver Neoplasms ; enzymology ; pathology ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; metabolism ; Signal Transduction ; drug effects ; TNF-Related Apoptosis-Inducing Ligand ; metabolism ; Tumor Suppressor Protein p53 ; metabolism