Abstract C141: Screening of novel RNA aptamer(s) that selectively bind(s) to prostatic acid phosphatase.

Abstract

Abstract Prostate cancer is becoming one of the most popular non-skin cancers in Korea due to continued increase of western life styles. Since earlier detection of prostate cancer can lead to complete cure, a lot of studies have been done on prostate cancer markers such as prostate-specific antigen (PSA), prostate-specific membrane antigen (PSMA), prostate acid phosphatase (PAP) and prostate stem cell antigen (PSCA). Among these biomarkers, PAP is gaining renewed interest because of its potential merits in diagnosis and therapeutics. PAP, which was initially identified in 1935, is an abundant enzyme that is synthesized in prostate epithelial cells and has enzymatic activity in acidic conditions. PAP expression is androgen-independent and increases in proportion to prostate cancer progression. Indeed, PAP expression level has high correlation with cause-specific survival and its dephosphorylation activity is believed to play an important role in the incidence and development of prostate cancer. Here, we screened the in vitro transcribed RNA libraries to get aptamer(s) that can selectively bind to PAP. Aptamers are oligonucleic acid molecules that bind to a specific target through formation of tertiary structures. These chemical antibodies can bind their target molecules with a high affinity and specificity and have the advantage of being less immunogenic in vivo. For in vitro selection, the ectracellular domain of PAP were cloned from PC3 cells and subjected to 6 rounds of SELEX procedure. This resulted in enrichment of the RNA aptamers that bound to the PAP ectodomain with 3-fold higher affinity than the library control as evidenced by real-time RT-PCR and gel shift assay. Sequence analysis of the aptamers revealed three distinct groups (G1, G2, N) having variable sequences within the region comprising nucleotides 43 to 87. The Kd values of the best clones with the highest affinity were within 120nM. These clones could also bind to the PAP-positive cells such as PC3 and LNCaP cells. Interestingly, 2'-OH-modification of the aptamers led to loss of binding, implying that 2'-F modification may be essential in binding to PAP. Characterization of these aptamers is currently underway and initial minimization results suggest that the structure coming from the 50 nucleotides is essential for binding to PAP. With further optimization, these PAP RNA aptamers could find wide application in theragonosis of prostate cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C141.