The zinc finger protein OZF (ZNF146) is overexpressed in colorectal cancer

Overexpression of the OZF gene has previously been demonstrated in the majority of pancreatic cancers. However, because the stages of tumour progression in this disease are poorly defined, no conclusion could be drawn concerning the relationship between OZF overexpression and the course of tumour progression. In contrast, initiation and progression steps are well defined in colorectal cancer. Most colon cancers are believed to arise from polypoid adenomas as a result of the gradual accumulation of genetic alterations, allowing the study of genetic events in the early stages of neoplasia. Accordingly, we wanted to assess the frequency of OZF overexpression in this tumour type and the relationship between overexpression and disease stage. Twenty-five colon carcinoma specimens from different sites and at various stages were analysed by immunoblotting using a highly specific mouse monoclonal antibody. Each sample was compared with adjacent normal colonic mucosa. Complementary immunohistochemical analysis was also carried out on a commercially available tissue array to identify cells expressing OZF. Of the 25 tumours analysed by immunoblotting, 20 expressed higher levels of OZF protein than their adjacent normal mucosa. Immunohistochemistry revealed OZF expression in tumour cells of 56/59 carcinomas and occasionally in infiltrating lymphocytes but at lower levels. Little or no staining was observed in cells taken from normal or inflammatory colon specimens. In both immunoblot and immunohistochemistry experiments, no correlation was found between OZF expression and clinical parameters such as TNM classification, stage, localization and age. Immunostaining was observed in low-grade adenomas, indicating that OZF expression occurs very early in the course of tumour progression. OZF expression, infrequent or absent in normal colonic mucosa, is present in more than 80% of colorectal cancers. Dysregulation of the OZF gene is an early event that may be implicated in the genesis of colonic carcinoma and may therefore provide a potential therapeutic target.