Selection of DNA Aptamers against Epithelial Cell Adhesion Molecule for Cancer Cell Imaging and Circulating Tumor Cell Capture

Abstract

Epithelial cell adhesion molecule (EpCAM) is overexpressed in most solid cancers and is an ideal antigen for clinical applications in cancer diagnosis, prognosis, imaging, and therapy. Currently, most of the EpCAM-based diagnostic, prognostic, and therapeutic strategies rely on the anti-EpCAM antibody. However, the use of EpCAM antibody is restricted due to its large size and instability. In this study, we have successfully identified DNA aptamers that selectively bind human recombinant EpCAM protein. The aptamers can specifically recognize a number of live human cancer cells derived from breast, colorectal, and gastric cancers that express EpCAM but not bind to EpCAM-negative cells. Among the aptamer sequences identified, a hairpin-structured sequence SYL3 was optimized in length, resulting in aptamer sequence SYL3C. The Kd values of the SYL3C aptamer against breast cancer cell line MDA-MB-231 and gastric cancer cell line Kato III were found to be 38 ± 9 and 67 ± 8 nM, respectively, which are better than that of the full-length SYL3 aptamer. Flow cytometry analysis results indicated that the SYL3C aptamer was able to recognize target cancer cells from mixed cells in cell media. When used to capture cancer cells, up to 63% cancer cell capture efficiency was achieved with about 80% purity. With the advantages of small size, easy synthesis, good stability, high binding affinity, and selectivity, the DNA aptamers reported here against cancer biomarker EpCAM will facilitate the development of novel targeted cancer therapy, cancer cell imaging, and circulating tumor cell detection.

Ligand-based targeted therapy: a novel strategy for hepatocellular carcinoma

“…199 For instance, a DNA-based EpCAM aptamer was utilized by Pilapong et al as a targeting moiety to develop a theranostic nanoprobe (called as EpCAM-MNPs) for HCC treatment and MRI. 200 In vitro study indicated that the DOXloaded EpCAM-MNPs had higher specificity in drug delivery for HBV-associated HCC cells and better intracellular uptake compared with free DOX.…”

Screening and Characterization of a Novel RNA Aptamer That Specifically Binds to Human Prostatic Acid Phosphatase and Human Prostate Cancer Cells

“…Aptamers can be easily conjugated to therapeutic molecules, such as drugs, carriers, toxins, and siRNAs Meng et al, 2012;Subramanian et al, 2012;Zhang et al, 2011). Moreover, aptamers can be conjugated with imaging probes for molecular imaging applications Song et al, 2013;Talbot et al, 2011;Zhang et al, 2012).…”

PSMA, EpCAM, VEGF, and GRPR as imaging targets in locally recurrent prostate cancer after radiotherapy.

“…However, due to its background staining, more careful selection of the protocol may be required for optimal targeting. Only a few studies consider VEGF and EpCAM-based diagnostics for targeted cancer imaging [73][74][75], but based on the results reported in this study, both antigens can be used for the detection of locally recurrent prostate cancer.…”