Detection of JCV DNA sequences in colon cancer cell lines by fluorescent in situ hybridization

Abstract

The inhibition of apoptosis is a crucial early step in the development of colorectal cancer (CRC), although the mechanisms are incompletely understood. In a variety of malignancies (e.g. pancreatic) there is an overexpression of the novel proto-oncogene, Akt (protein kinase B), an antiapoptotic serine-threonine kinase also implicated in Wnt signaling. Since the role of Akt in CRC has not been previously explored, we examined this by immunohistochemistry (lHC) in sporadic human adenomas and CRe. To investigate the microsatellite instability (MSI) pathway, tumors from patients with hereditary nonpolyposis colon cancer (HNPCC) were assessed. Finally, Akt was evaluated in experimental CRC using the azoxymethane (AOM)-rat model. METHODS: IHC was performed on paraffin-embedded samples with a monoclonal and polyclonal antibody for Aktl/2 using the Vectastain ABC kit. Human and animal colon tumors were selected from archived materials. Akt staining of sections was assessed by a pathologist using appropriate negative and positive controls. RESULTS and CONCLUSIONS: As demonstrated by the Table, Akt is overexpressed in approximately 22-42% of human and experimental CRe. The genetic mechanisms of tumor development (adenomatous polyposis coli mutation in sporadic CRC, f3-catenin mutations in AOM-tumors or MSI in HNPCC tumors) did not appear to significantly affect expression of this epigenetic protein. The observation that Akt overexpression occurs early in carcinogenesis (adenomas) emphasizes its biological significance. Our recent demonstration that Akt downregulation is important in nonsteroidal antiinflammatory drugs (NSAID) induction of apoptosis is supported by the observation that AOM-tumors from animals that had been treated with NSAIDS had a trend towards lower Akt expression than those on a control diet (60 versus 28 % although the numbers were small). This data suggests that Akt overexpression is important in the early dysregulation of apoptosis and Wnt signaling which characterizes CRC development. GASTROENTEROLOGY Vol. 118, No.4