More than 90% of cancer-related deaths (more than eight million deaths worldwide each year) are due to the development of tumor metastasis, a complex process with multiple steps in which cancer cells spread within the patient’s body. There is an emerging realization that the fearsome transmitters of this cancer dissemination are clusters of so-called circulating tumor cells (CTC) that detach from the primary tumor, disseminate and home themselves in distant tissues. During their travel together in the bloodstream, they are subjected to important mechanical forces, for example, while passing through small capillaries. Nevertheless, the current knowledge of how these cells are held together is extremely limited.
This project aims at unravelling the biophysical properties of CTCs clusters and its dynamic changes that enable clusters to pass through small capillaries. To better understand this, we offered to characterize the adhesion forces between cells and the viscoelastic properties of individual CTC and CTC clusters using an advanced technique called atomic force microscopy.
However, this technique involves immobilizing the cells on a surface to perform the measurements, which does not correspond to the physiological state of circulating cells. We therefore sought to develop a new technique for measuring the mechanical properties of cells directly in suspension. To do so, we combined acoustic force spectroscopy, an emerging technique using sounds waves to manipulate or levitate micro-objects, and reflection contract interference microscopy, an optical technique known since decades. We have demonstrated that this unique combination allows measuring the deformation of objects in suspension.
