Detection of hTERT mRNA in gastrointestinal tract cancer specimens.

Human telomerase consisting of telomerase RNA template (hTR) and telomerase reverse transcriptase (hTERT) provides a mechanism for synthesis of telomere repeats that prolongs life span of cells. Telomerase activity is present in germ-line and malignant tumor cells but not in most normal human somatic cells. This study determined hTERT mRNA level in tissue samples from patients with gastrointestinal tract (GI) cancers. Tissue samples were obtained from 22 GI cancer patients, 3 gastrointestinal stomal tumors (GIST) and 25 corresponding non-cancerous tissues. hTERT expression was determined by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) using Taqman probe, hTERT mRNA was detected in 12 of 22 cancerous tissue samples. Six of 8 tissue samples obtained from patients with hepatocellular carcinoma and cholangiocarcinoma were positive for hTERT. However, hTERT mRNA was not detected in GIST and non-cancerous tissues. These results suggest that hTERT may be an effective target for cancer therapies to treat many type of GI cancers including cholangiocarcinoma and hepatocellular carcinoma.

Altered expression of thioredoxin reductase-1 in dysplastic bile ducts and cholangiocarcinoma in a hamster model

Thioredoxin reductase 1 (TrxR) is a homodimeric selenoenzyme catalyzing thioredoxin (Trx) in an NADPHdependent manner. With regard to carcinogenesis, these redox proteins have been implicated in cell proliferation, transformation and anti-apoptosis. In the present study, using a hamster cholangiocarcinoma (ChC) model, we evaluated the immunohistochemical expression pattern of TrxR in precancerous lesions and ChCs as well as in normal bile ducts. The goal of this study was to determine the potential role and importance of TrxR in cholangiocarcinogenesis. For the ChC model, we obtained liver tissue specimens with dysplastic bile ducts prior to the development of ChC 8 weeks after initiation of the experiment and ChC samples at 27 weeks. The immunohistochemical analysis showed diffuse cytoplasmic overexpression of TrxR in the dysplastic bile duct epithelial cells as well as in cholangiocarcinoma; this was comparable to the negative or weakly positive in normal and type 1 hyperplastic bile ducts. However, TrxR appeared to be considerably down-regulated in the ChCs when compared to the higher expression observed in the dysplastic bile ducts. Therefore, these results suggest that TrxR overexpression followed by down-regulation might be an important event in cholangiocarcinogenesis, especially at early stages including the cellular transformation of candidate bile ducts. Further studies are however required to determine whether TrxR may be a potential target molecule for chemoprevention against cholangiocarcinogenesis. In addition, the molecular mechanism as well as the importance of the loss of TrxR in the development of cholangiocarcinoma, following dysplastic transformation of bile duct cells, also remains to be clarified.