Abstracts
2000 Digestive Disease Week

# 2397 Telomerase Activity of Malignant Cells Correlates with Dukes’ Stage In Colorectal Cancer.
Aqeel Ghori, Bernhard Usselmann, Steve Ferryman, Ian Fraser, Alan Morris, Coventry, United Kingdom

Introduction: The ribonucleoprotein telomerase, which is responsible for elongating chromosomal telomeres, has been proposed as a potential prognostic or diagnostic marker for malignancy. Whether telomerase activity of clinical specimens correlates with other clinico-pathological variables, however, remains controversial. In colorectal cancer there is evidence that telomerase activity is higher in advanced cancers, although this has not been demonstrated in all studies. We therefore designed experiments to assay telomerase activity in isolated malignant cells of primary colorectal cancers. This allowed us to correct for the contribution of other cellular components of a cancer and for the presence of telomerase inhibitors in telomerase assays. We were then able to correlate telomerase activity of separated malignant cells with pathological stage of the disease. Methods: Thirty colorectal cancer and 20 corresponding normal mucosa specimens were obtained following surgical resection. Tissues were mechanically disaggregated and digested overnight with collagenase, DNase and hyaluronidase. Debris was removed by filtration and density gradient centrifugation (Lymphoprep). The epithelial cell population was separated using Ber-EP4 pan-epithelial antibody and Magnetic Activated Cell Sorting. Recovered cells of half the cancers were H&E stained to determine purity. Telomerase activity was quantified by the Telomeric Repeat Amplification Protocol (TRAPezeTM, Intergen Company) and telomerase activity expressed as Total Product Generated (TPG). Results: Epithelial cells of three of 20 normal mucosa specimens were telomerase positive with weak activity. In the cancer group the vast majority (99%) of the epithelial cells recovered were malignant by cytological critera. These cells were telomerase positive in all the cancers, with a wide range of telomerase activity values (0.19-308 TPGs). Telomerase activity correlated with Dukes’ stage (r=0.52, p=0.004, Spearman’s rank). Conclusions: Pathological stage correlates with telomerase activity of the malignant cell population of the primary tumour in colorectal cancer. This suggests that telomerase activity may increase during the progression of a cancer, possibly through the selection of telomerase rich clones. This has implications for the design or use of anti-telomerase agents as potential adjuvant therapy, suggesting that these agents have increased efficacy in advanced stage malignancy.