Triple negative (TN) breast cancers are defined by a lack of expression of estrogen, progesterone, and her-2/neu receptors. It is widely recognized that TN breast cancers have a poorer prognosis than other subtypes of breast caner. Given the lack of effective targeted therapies for TN breast cancer patients, understanding of the mechanisms of growth and invasion of these tumors will provide insight into developing novel approaches to lower the mortality from TN breast cancer.

We utilized three TN breast cancer cell lines (HCC38, HCC1806, HCC1937) as model systems to characterize mechanisms of growth, migration, and invasion. FACS analyses demonstrated that these TN cell lines showed a phenotype of CD44+CD24-/lowepithelial specific antigen (ESA)+. An inhibitory antibody against exon v10 of CD44 significantly inhibited three-dimensional (3D) growth of tumor cells. Importantly, this antibody also inhibited alpha2beta1/alpha3beta1 integrins-mediated migration and invasion into matrigel. These results suggest that CD44 harboring exon 10 facilitates progression and metastasis of TN breast cancer cells in vivo by enhancing growth, migration, and invasion. We also demonstrated that this exon interacts with a cell surface tyrosine kinase,

EphA2. Thus, we hypothesize that CD44 would form a molecular complex with EphA2 through exon v10 on TN breast cancer cells that plays a key role in facilitating invasion and metastasis.

In order to develop novel reagents to inhibit TN breast cancer invasion and metastasis, we have utilized SELEX (systematic evolution of ligands by exponential enrichment) to isolate DNA aptamers that specifically recognize exon v10 of CD44. DNA aptamers are functional molecules with the appropriate sequence and structure to form a complex with a target molecule. Typically, dissociation constants for these aptamer-target complexes are in the high pico-molar to low nano-molar range, which is comparable to antibodies. Given the fact of the ease of chemical synthesis and modifications of oligonucleotides, DNA aptamers that recognize cancer cells will be easier to develop and have a great impact for the next generation of strategies for cancer detection, diagnosis, and therapy. We describe the development of “function-blocking” DNA aptamers specific for exon v10 of CD44 that inhibits TN breast cancer invasion and metastasis.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD02-08.