Generation of an enriched pool of DNA aptamers for an HER2-overexpressing cell line selected by Cell SELEX

Overexpression of human epidermal growth factor receptor 2 (HER2) occurs in a largepercentage of breast cancers. Monoclonal antibodies targeting HER2 are vastly used for bothdiagnostic and therapeutic aims. However, identifying a new molecular probe against HER2with improved diagnostic and therapeutic features is of great importance. In this report, wehave applied the cell systematic evolution of ligands by exponential enrichment (SELEX)strategy for 16 selection rounds to generate an enriched pool of aptamers that specificallyrecognize the HER2 positive cell line. During the Cell SELEX procedure, a human HER2-overexpressing breast cancer cell line and a human HER2 negative breast cancer cell linewere used. Our results reveal that polymerase chain reaction (PCR) amplification of randomDNA libraries and the selected single-stranded DNA pool in different Cell SELEX rounds aredifferent from what we expect from PCR amplification of homologous DNA. Our results alsoconfirmed previous studies describing positive HER2 status of SK-BR3 and the absence ofthe HER2 expression in the MDA-MB468. We also developed a new method, Cell enzymelinkedassay, to monitor the enrichment of aptamers in a given round of Cell SELEX. Thismethod would also be useful in other experiments using live cell enzyme-linkedimmunosorbent assay on adherent cells.

Keywords:

Aptamer , Breast Cancer , Cell SELEX , Cell ELAA , HER2