Optical coherence mechano-microscopy for biomechanical characterization of 3D cancer models

Solid tumours are typically first diagnosed by palpation, revealing increased stiffness, while cancer cells are usually reported to be softer. The mechanical characteristics are not universal and depend on the cell type and the stage of development. Current techniques are usually point or 2D measurement techniques that lack depth penetration in 3D samples. We are developing optical coherence mechano-microscopy integrated with a confocal fluorescence microscope as a platform to investigate the mechanical phenotypes of 3D cancer models, mimicking the conditions in the native tumour microenvironment. This platform enables unique measurement of the 3D elasticity (i.e. Young's modulus) of metastatic and non-metastatic breast cancer cell spheroids embedded in GelMAl, presenting the extracellular matrix, co-registered with fluorescence images. Our findings show that cells at the centre of non-metastatic cancer cell spheroids are softer (5.8 kPa) than the cells at the periphery (12.7 kPa). In contrast, migrating cells at the periphery of the metastatic cancer cell spheroids are softer (5.7 kPa) than the less motile cells at the centre of these spheroids (8.0 kPa).