DNA Aptamers against Exon v10 of CD44 Inhibit Breast Cancer Cell Migration

Abstract

CD44 adhesion molecules are expressed in many breast cancer cells and have been demonstrated to play a key role in regulating malignant phenotypes such as growth, migration, and invasion. CD44 is an integral transmembrane protein encoded by a single 20-exon gene. The diversity of the biological functions of CD44 is the result of the various splicing variants of these exons. Previous studies suggest that exon v10 of CD44 plays a key role in promoting cancer invasion and metastasis, however, the molecular mechanisms are not clear. Given the fact that exon v10 is in the ectodomain of CD44, we hypothesized that CD44 forms a molecular complex with other cell surface molecules through exon v10 in order to promote migration of breast cancer cells. In order to test this hypothesis, we selected DNA aptamers that specifically bound to CD44 exon v10 using Systematic Evolution of Ligands by Exponential Enrichment (SELEX). We selected aptamers that inhibited migration of breast cancer cells. Co-immunoprecipitation studies demonstrated that EphA2 was co-precipitated with CD44. Pull-down studies demonstrated that recombinant CD44 exon v10 bound to EphA2 and more importantly aptamers that inhibited migration also prevented the binding of EphA2 to exon v10. These results suggest that CD44 forms a molecular complex with EphA2 on the breast cancer cell surface and this complex plays a key role in enhancing breast cancer migration. These results provide insight not only for characterizing mechanisms of breast cancer migration but also for developing target-specific therapy for breast cancers and possibly other cancer types expressing CD44 exon v10.

Expression and Function of CD44 in Epithelial Ovarian Carcinoma

“…Furthermore, isoform-specific antibodies have been reported, including those against CD44v6, where a radiolabeled CD44v6 monoclonal antibody showed selective tumor targeting and high tumor uptake in a nude mouse squamous cell carcinoma xenograft [ 87 ]. In addition to antibody-based targeting of CD44, other strategies have been employed using DNA aptamers targeting CD44v10 in breast cancer [ 88 ] and peptides mimicking CD44v6 for blocking the coreceptor function of CD44v6 for c-Met and VEGFR-2 in endothelial cells thereby impeding angiogenesis [ 89 ]. In an effort to develop new and effective treatment strategies for advanced-stage ovarian cancer patients, CD44 is also being explored as a therapeutic target.…”

Perspectives of CD44 targeting therapies

“…DNA aptamers were isolated based on their binding to exon v10 of CD44 by SELEX technology (Iida et al 2014). In breast cancer cells, CD44v10 proteins appear to form complexes with the surface protein EphA2, which accounts for the migratory ability of the cells (Iida et al 2014). This complex formation is impaired by the treatment of the breast cancer cells with the v10-specific aptamers, and consequently, the migration of the breast cancer cells is inhibited.…”

p63 inhibits CD44+/CD24‑ cell proliferation and chemoresistance in papillary thyroid carcinoma cells

“…A previous study reported that CD44v6 is an important indicator in PTC cell differentiation, and the expression of CD44v6 is significantly higher in malignant lesions compared with non-malignant lesions ( 7 ). CD44 + /CD24 − cells are more aggressive than CD44 − cells, not only in PTC, but also breast and ovarian cancer ( 8 – 10 ). However, the underlying mechanism that promotes CD44 + cells to exhibit a more malignant phenotype remains unknown.…”