Drug-induced changes in nanomechanics and ligand-receptor binding forces of mammalian cells as measured by AFM

Abstract

Investigating cell mechanics is of high interest because it includes several essential and fundamental cellular processes such as cell motion, deformation and interaction, as well as adhesion, division, shape maintenance and mechanical signals processing into biochemical ones. This type of studies can lead to a better understanding of mechanical properties of cells and cellular structures and their interactions with the environment can be also evaluated. Comparative studies on the mechanics of normal and malignant cells of the same type are of great importance as they can reveal new information about, and help understanding mechanisms of malignant transformation. In this work, we investigate the morphology and the elastic properties of live cultured, normal human mammalian epithelial cells (HMEC) and cancer breast epithelial cells (MCF7), using atomic force microscopy (AFM). We describe the different behavior of the two similar cell lines under curcumin treatment. The first changes in the HMEC cell morphology are observed after two hours long incubation with curcumin. A six-hour long treatment leaves the MCF7 cells morphology non-affected, but the microtubules of HMEC cells disassemble and form a ring-like organization circumscribing the nuclear area. The observed morphological changes were correlated to modifications in cell's mechanics via elasticity force-volume measurements. Curcumin treatment modified elasticity of the HMEC cells increasing the cell's average Young's modulus two- to three-fold, especially in the cytoplasmic area. Contrariwise, a slight decrease in the Young's modulus was noticed for the MCF7 cells, as they become softer due to the action of curcumin. This different response of the malignant and non-malignant cells under the same treatment might be of high importance in developing follow-up therapy against breast cancer. Moreover, an anticancer agent, the Cetuximab antibody that can interfere with Epidermal Growth Factor Receptor (EGFR) activity, was coupled to the AFM tip in order to evaluate the Cetuximab-EGFR binding forces on the surface of human epithelial carcinoma cells (A431) presenting an EGFR overexpression as in a large variety of tumors. The effect of mixed treatments, i.e. different therapeutic drugs in combination with the Cetuximab, was studied on the ligand-EGFR binding forces and on cell elasticity. Our results evidence the modification of the A431 cells' elasticity and of the binding forces between the EGFR receptor and the Cetuximab agent when the cells were treated with Cetuximab alone or in combination with other drugs, opening the way to the development of new approaches for epithelial carcinoma treatment.