WT1 expression as an independent marker of poor prognosis in colorectal cancers

WT1 has been proven to be a prognostic marker and molecular target in various human cancers. In this study, we aimed to investigate the prognostic role of WT1 in colorectal cancers (CRCs). Archival tissue samples from 157 CRC cases who underwent curative surgery in our institute from February 1999 to May 2004 were subjected to WT1 expression studies using an immunohistochemistry technique. Number of positive staining per 500 tumor cells and staining intensities were analyzed against overall survival. Of 157 CRCs, 83 were colonic and 74 were rectal cancers. The mean follow-up period was 116 (range 77-145) months. Five-year and seven-year OS rates were 60.9% and 52.8%, respectively. WT1 immunostaining was positive in 143 cases (91%). The median number of positive cells was 120 (range 0-420). Univariate analysis by Log-rank test showed that AJCC stage, tumor site (rectal cancer), number of positive cells > 120 and high staining intensity (score ++/+++) were significantly associated with poorer survival (p-value < 0.01). Five-year survival rates in cases with positive cells of <= 120 cells and > 120 cells were 72.2% and 49.4%, respectively. Five-year survival in cases with staining intensity of ++ or more was 45.3%, compared with 69% in cases with intensity of less than ++. Multivariate regression analysis demonstrated that the staining intensity, high tumor stage and rectal site were independent factors indicating poorer survival. Our findings indicate that WT1 expression is a marker of poor prognosis in CRCs, independent of AJCC staging.