Distribution and expression of the ERM family members, ezrin, radixin, moesin and EHM2 in human colon cancer and the clinical relevance

Introduction: The Ezrin-Moesin-Radixin (ERM) family is a protein family that are cytoskeletal linker proteins and acts as an anchorage protein for cell surface molecules and regulates cell adhesion in epithelial cells. This study investigated the expression pattern of the ERM family and its associated member, EHM2, in human colon tissues (both normal and tumour) at the protein and messenger levels and explored the clinical and prognostic values of the family. Methods: Fresh frozen normal colon and colon cancer tissues were used. The distribution of ezrin protein in the tissues was investigated using immunofluorescence (IFC). Transcript levels of ezrin, moesin, radixin and EHM2 were determined using quantitative polymerase chain reaction (PCR) analysis. Levels of expression were analysed against tumour staging and clinical outcome of the patients. Results: In normal tissues, ezrin stained strongly in the region of intercellular adhesions and wasabsent in the apical region of the colonic epithelial cells. There was little cytoplasmic staining in normal cells. However, in tumour tissues, colon cancer cells showed a shift in the pattern of staining in which ezrin stained strongly in the cytoplasmic area of cancer cells, whereas the inter-cellular staining was either absent or weak. Using quantitative analysis, it was found that there was a marked increase in the levels of ezrin, moesin and radixin in tumour tissues compared with normal tissues However, in advanced disease, both Dukes C and Dukes B tumours had significantly higher levels of ezrin transcript compared with Dukes A tumours (P=0.0047 and P=0.0004, respectively). High levels of ezrin expression were also significantly associated with disease free and overall survival of the patients (P=0.006 and P=0.011, respectively). Conclusions: In normal epithelial cells, ezrin is confined to the cell-cell junction area and confers cellcell adhesion. In colon cancer cells, ezrin is redistributed to the cytoplasmic region, which may weaken the adhesion between cells and increase invasive potential. Together with an increase in mRNA expression in late stage tumours, it is concluded that the loss of ezrin at the inter-cellular region and the rise in the cytoplasmic levels of ezrin in colon cancer cells is linked to the aggressiveness of colon cancer cells and the clinical outcome of the patients.