High detection rate of circulating tumor cells in blood of patients with prostate cancer using telomerase activity.

Background: Circulating tumor cells (CTCs) cannot be readily detected with currently available methods in the majority of patients with prostate cancer. Telomerase activation, one of the major immortalization events, is found in most cases of prostate cancer. We attempted to develop a method using telomerase activity to isolate CTCs in patients with prostate cancer.
Patients and Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using Ficoll-Hypaque. Immunomagnetic beads coated with an epithelial cell-specific antigen antibody (BerEP4) were used to harvest epithelial cells from PBMCs. Telomerase activity was detected in harvested epithelial cells using the telomerase-PCR-enzyme-linked immunosorbent assay method.
Results: Blood samples from 107 patients with prostate cancer were studied. CTCs were detected in 19 of 24 (79%) patients with advanced prostate cancer. In contrast, CTCs were not detected in blood samples from 22 healthy male volunteers. CTCs were even identified in patients with an undetectable (<0.1 ng/ml) serum prostate-specific antigen (PSA). CTCs were detected in 55 of 70 (79%) patients with localized prostate cancer before radical prostatectomy (n = 30) or brachytherapy (n = 40). CTCs were also detected in 3 of 13 patients (23%) with an undetectable serum PSA measured at least 1 year after radical prostatectomy, which is consistent with the expected relapse rate in this setting.
Conclusion: CTCs can be detected using telomerase activity in a large majority and a wide variety of patients with prostate cancer, including those with localized disease.