508 In Vitro Selection of Molecular Recognition Elements for Molecular Targeting of Prostate Cancer

Abstract

Prostate cancer is the most-diagnosed non-skin cancer and the second leading cause of cancer-related deaths among males in the United States. Current therapeutic and detection methods are not specific for the disease. This often leads to a more aggressive recurrence after treatment and unnecessary biopsies due to false positives in detection. To address this problem, molecular recognition elements (MREs) that bind to a molecule on the surface of prostate cancer cells but not benign prostate cells have been isolated. MREs are obtained through the in vitro selection process, an iterative enrichment of a large pool of random biomolecules for those that bind to a target of interest but not closely related targets. Seven rounds of in vitro selection have been completed by panning and fluorescenceactivated cell sorting (FACS), enriching a yeast-displayed single-chain variable fragment (scFv) antibody library with an initial diversity of 10 molecules. In positive selections, yeast-displayed scFv molecules that bound to the LNCaP prostate cancer cell line were amplified and subjected to negative selections. In these, scFvs that bound to closely related targets were subtracted. From this process, two MREs have been identified. These MREs bind to the LNCaP cell line but not benign and other non-target cell lines. Future work will determine clinical relevance with binding to ex vivo prostatic tissue. Additionally, the cell surface molecule which the MREs bind to will be determined by liquid chromatography/mass spectrometry. This work will produce a prostate cancer cell-specific MRE useful in specific detection and therapeutic targeting of prostate cancer. We acknowledge support from the National Science Foundation (Cooperative Agreement 1003907) and the American Foundation for Pharmaceutical Education.