DNA Aptamers for the Malignant Transformation Marker CD24.

Cluster of differentiation 24 (CD24) is a cell surface glycoprotein, which is largely present on hematopoietic cells and many types of solid tumor cells. CD24 is known to be involved in a wide range of downstream signaling pathways and neural development, yet the underlying mechanisms are poorly understood. Moreover, its production correlates with poor cancer prognosis, and targeting of CD24 with different antibodies has been shown to inhibit disease progression. Nucleic acid aptamers are oligonucleotides that are selected from random DNA or RNA libraries for high affinity and specific binding to a certain target. Thus, they can be used as an alternative to antibodies. To gain an insight on CD24 role and its interaction partners, we performed several SELEX (systematic evolution of ligands by exponential enrichment) experiments to select CD24-specfiic DNA aptamers. We found that the cell-SELEX approach was the most useful and that using HT-29 cell line presenting CD24 along with CD24 knockdown HT-29 cells has selected six aptamers. For the selected aptamers, we determined dissociation constants in the nanomolar range (18-709 nM) using flow cytometry. These aptamers can be applied as diagnostic tools to track cancer progression and bear a potential for therapeutic use for inhibiting signaling pathways that promote the metastatic process.