Telomerase activity in malignant and benign renal tumors

Objectives: An important characteristic of malignant cells is their unlimit ed replicative potential, their immortality. In conferring this immortality , the enzyme telomerase is believed to play a crucial role, The detection o f telomerase activity provides new knowledge regarding the biologic growth behavior of tumors and offers new diagnostic and therapeutic tools. Methods : In the present study the sensitive TRAP assay (telomeric repeat amplifica tion protocol) was used to examine 44 malignant renal tumors and 8 benign t umors of the kidney and 52 specimens of normal renal tissue for telomerase activity. Results: Telomerase activity was detected in 63% of tissue sample s obtained from histologically confirmed renal cell carcinomas. In cases of renal cell carcinoma restricted to the kidney, telomerase activity was det ected in 58%. In cases in which tumor growth has progressed beyond the limi ts of the organ, telomerase activity was found in 69%. This stage dependenc e, however, did not reach statistical significance. No correlation to tumor grading was observed. Telomerase activity was found less frequent in chrom ophobe renal cell carcinomas. Neither the 8 benign renal tumors (4 oncocyto mas and 4 angiomyolipomas) nor the specimens of normal kidney showed any ev idence of telomerase activity. Conclusions: The proportion of remarkable sl ow-growing renal cell carcinomas showing telomerase activity is less than i n other malignancies and may correlate with biologic growth behavior. Possi ble explanations include the presence of an alternative pathway, called ALT (alternative lengthening of telomeres) and an association with the loss or presence of the telomerase suppressor on the short arm of chromosome 3. Pr olonged follow-up will be of special interest to determine whether lack of telomerase activity predicts favorable outcome.