Development of ssDNA‐based aptamers specific to PSMA

Abstract

Prostate‐specific membrane antigen (PSMA) has been considered a valuable biomarker for specific imaging detection and selective targeted therapy of prostate cancer. Compared to antibodies, the aptamers, a new class of molecular probes, have more flexibility, less blood resistance and much less immunogenicity in vivo. However, the biostability of RNA‐based aptamers for PSMA is still a major concern for in vivo use. So we employed a unique SELEX approach by combination of both cell‐based selection and biomarker‐based enrichment to develop ssDNA aptamers specific to PSMA. The cultured PSMA‐positive prostate cancer cells LNCaP was used for cell‐SELEX. After 10 rounds of positive cell selection and 6 rounds of counter‐selection, the enriched ssDNA aptamers were labeled with Cy5 fluorescent reporter and their cell binding capacity was evaluated. Flow cytometry analysis revealed that 84% of LNCaP cells were highlighted by the enriched ssDNA aptamers at the concentration of 50nM, similar to that stained by anti‐PSMA antibodies. In control experiments, no binding of the enriched ssDNA aptamers to the PSMA‐negative cancer cells were observed under the same condition. Sequence analysis and sensitivity/specificity assays of the enriched aptamers are currently undergoing. The results will be presented at the meeting. Supported by NIH grants R01 CA151955.