Sialic Acid as a Biomarker Studied in Breast Cancer Cell Lines In Vitro Using Fluorescent Molecularly Imprinted Polymers

Zahra El-Schich,Jenny L Persson,Sudhirkumar Shinde,Emil Johansson,Mikael Elofsson,Nishtman Dizeyi,Börje Sellergren,Anette Gjörloff Wingren,Remi Caraballo,Tommy Göransson,Yuecheng Zhang

doi:10.3390/app11073256

Abstract

Sialylations are post-translational modifications of proteins and lipids that play important roles in many cellular events, including cell-cell interactions, proliferation, and migration. Tumor cells express high levels of sialic acid (SA), which are often associated with the increased invasive potential in clinical tumors, correlating with poor prognosis. To overcome the lack of natural SA-receptors, such as antibodies and lectins with high enough specificity and sensitivity, we have used molecularly imprinted polymers (MIPs), or “plastic antibodies”, as nanoprobes. Because high expression of epithelial cell adhesion molecule (EpCAM) in primary tumors is often associated with proliferation and a more aggressive phenotype, the expression of EpCAM and CD44 was initially analyzed. The SA-MIPs were used for the detection of SA on the cell surface of breast cancer cells. Lectins that specifically bind to the a-2,3 SA and a-2,6 SA variants were used for analysis of SA expression, with both flow cytometry and confocal microscopy. Here we show a correlation of EpCAM and SA expression when using the SA-MIPs for detection of SA. We also demonstrate the binding pattern of the SA-MIPs on the breast cancer cell lines using confocal microscopy. Pre-incubation of the SA-MIPs with SA-derivatives as inhibitors could reduce the binding of the SA-MIPs to the tumor cells, indicating the specificity of the SA-MIPs. In conclusion, the SA-MIPs may be a new powerful tool in the diagnostic analysis of breast cancer cells.

Highlights

Breast cancer cannot be classified as one diseases, but is largely heterogeneous and the diagnosis and treatment in affected women with breast cancer can vary
We show that the sialic acid (SA)-molecularly imprinted polymers (MIPs) recognize breast cancer cells with low CD44 and high epithelial cell adhesion molecule (EpCAM) expression, indicating that SA-MIPs can be used as an additional tool for detecting EpCAM positive breast cancer cells
SA Staining With Lectins on Breast Cancer Cell Lines

Summary

Introduction

Breast cancer cannot be classified as one diseases, but is largely heterogeneous and the diagnosis and treatment in affected women with breast cancer can vary. Breast cancer is comprised of several subgroups according to previous classification: luminal A, luminal B, basal-like, human epidermal growth factor receptor 2 (HER2)-positive and normal subgroups [2,3]. Cancer cells use several mechanisms to bypass recognition by the immune cells, thereby escaping immune surveillance and progressing through metastases [4]. The circulating tumor cells (CTCs) released from primary tumors are considered to have the capability to initiate distant metastasis. Detection and isolation of CTCs using the Food and Drug Administration (FDA)-approved CellSearch platform is based on automated immunomagnetic sorting and on expression of the epithelial cell adhesion molecule (EpCAM) and cytokeratin [5]. The expression of EpCAM in primary tumors is often associated with proliferation and a more aggressive phenotype, if it is considered as high [6]. Alternative methods are definitely needed for the detection of CTCs that are able to recognize a broader spectrum of phenotypes

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