The trace element selenium is discussed as a chemopreventive agent in colorectal carcinogenesis. Selenocysteine-containing proteins, so-called selenoproteins, represent potential molecular targets for nutritive selenium supplementation. Due to their antioxidative potential, the selenoproteins gastrointestinal glutathione peroxidase (GI-GPx) and selenoprotein P (SePP) are considered to provide protection against reactive oxygen species (ROS), thereby reducing DNA damage and preventing development of colon cancer. GI-GPx and SePP are abundantly expressed in normal colon mucosa. Recently, we demonstrated both reduced SePP expression and increased GI-GPx expression in colorectal adenomas. In this study, we investigated the expression of SePP and GI-GPx in colorectal cancers compared with corresponding normal mucosa. Further, the occurrence of genetic alterations within the SePP and GI-GPx genes was analyzed. We observed a significant reduction or loss of SePP mRNA expression in colon cancers, whereas GI-GPx mRNA and protein expression varied between different tumor samples. In addition, we identified novel polymorphisms within the SePP and GI-GPx genes with so far unknown relevance for protein function. Our results argue against a general decrease of selenoprotein expression in colorectal carcinogenesis but imply specific differential regulation of expression of individual selenoproteins.

(Gut 1997; 40: 481-484)

Neuroendocrine tumour metastases might show characteristics which are similar to hemangiomas. In patients with liver cirrhosis and severe fatty liver disease the identification of NET with CEUS as a malignant lesion is more difficult. The sensitivity of CEUS in identifying malignancy based on the lack of portalvenous enhancement is higher for metastases of other origin.

Reactivation of chronic hepatitis B in patients receiving cytotoxic treatment for non-Hodgkin's lymphoma is well documented. We report a case of a patient with chronic hepatitis B who was treated by chemotherapy because of non-Hodgkin's lymphoma. After the second cycle of chemotherapy she developed a severe flare-up of hepatitis B. Liver biopsy revealed highly active hepatitis and confluent necroses. Within 3 weeks, the patient recovered spontaneously. Prophylactic treatment with lamivudine (Epivir,Glaxo-Wellcome, 150 mg b.i.d.) led to a decrease of HBV-DNA below the detection limit. Further chemotherapy was administered and autologous stem cell transplantation was successfully performed without another reactivation of hepatitis B. Antiviral treatment was stopped 16 weeks after stem cell retransfusion. So far, no further flare-up of hepatitis B has occurred and the patient's lymphoma has not relapsed. Thus, the case described here indicates a possible role of lamivudine in preventing hepatitis B flare-up during antineoplastic chemotherapy. We suggest that lamivudine be considered for prophylaxis against fulminant hepatitis in patients with chronic HBV infection undergoing high-dose antineoplastic therapy.

Four selenocysteine-containing proteins (gastrointestinal glutathione peroxidase, plasma glutathione peroxidase, selenoprotein P, and thioredoxin reductase-alpha) are expressed in the colonic mucosa. Because of their antioxidant functions, a protective role in colon carcinogenesis is discussed. The aim of this study was to elucidate an involvement of gastrointestinal selenoproteins during the adenoma-carcinoma sequence. Matched pairs of biopsies of colorectal adenomas and adjacent normal mucosa from 11 patients were analyzed for mRNA expression, protein expression, or enzyme activity of selenoproteins by Northern blot, Western blot, or enzymatic tests. All adenomas revealed a marked reduction of selenoprotein P and a variable increase of gastrointestinal glutathione peroxidase mRNA compared with adjacent tissue. Thioredoxin reductase-alpha and plasma glutathione peroxidase mRNA expression were not altered in adenomas. The Northern blot results were confirmed by Western blot analysis or enzyme activity measurement, respectively. We conclude that gastrointestinal glutathione peroxidase and selenoprotein P play a complementary role in the antioxidative cell defense along the adenoma-carcinoma sequence. It remains to be shown whether upregulation of gastrointestinal glutathione peroxidase in adenomas represents a compensatory mechanism to reduce susceptibility for oxidative damage resulting from the loss of selenoprotein P.