Prostate cancer cells overexpress a well-characterized surface antigen, prostate-specific membrane antigen (PSMA) (Tasch et al., 2001). An RNA selection was conducted against the extracellular component of PSMA called sPSM (Lupold et al., 2002). After six rounds of SELEX, two aptamers were identified. The two aptamers named xPSM-9 and xPSM-10 inhibited xPSM with a Kj of 2.1 and 11.9 nmol/L respectively. Aptamer xPSM-10 was truncated (xPSM-10-3) and fluor-escently end-labeled to evaluate its ability to bind PSMA-expressing cancer cells. Using PSMA-positive LNCaP and a PSMA-negative PC-3 prostate cancer cell line, xPSM-10-3 bound to LNCaP cells but not PC-3, showing specificity for PSMA and its potential in therapeutic development for this target.
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