Over 90% of cancer deaths are due to metastases that have spread and not because of the primary tumor. Efforts to divert malignant cells from leaving the initial tumor and entering the bloodstream - only to grow in organs such as the liver and lungs, for example - have had limited success. Treatment becomes significantly more difficult when metastases recur and for many tumor patients, this means the cancer can no longer be ‘cured’.
Effectively preventing malignant tumors from metastasizing would not only significantly improve life expectancy for many patients, but also their quality of life.

The molecular principles of metastasis are very complex, taking place within circulating clusters of tumor cells - so-called CTCs (circulating tumor cells) – starting in the primary tumor and circulating to the patient's blood or lymphatic fluid until they settle in the body and begin metastasizing. The mechanical properties in tumor cells are different as opposed to blood cells. While blood cells are adapted to a high shear of fluid, the same does not apply to CTCs.

The liquid shearing process can be described as follows: A certain amount of force is needed to move two plates that have a liquid film in between them and overcome the friction between the layers of liquid moving against each other. The magnitude of this force is proportional to the viscosity and the speed. This kind a relative movement of different layers of liquid against each other is called a (liquid) shear. If a solid object, such as a cell, is in this liquid, forces acting in opposite directions at the opposite ends of the object and result in potentially destroying the object.

A pump featuring a mechanically-coupled throttle
A team at the Institute of Biomedical Mechatronics has published a paper in the scientific journal "Scientific Reports" introducing an idea to use these different biophysical properties to mechanically attack tumor cells in the critical intermediate phase, meaning when they are in the bloodstream. Together with co-author Dipl. Ing. Kurt Priesner, civil engineer and owner of Griesmühle, JKU researchers have built a "tumor cell shredder" and have applied for a patent. Prof. Baumgartner, head of the Institute of Biomedical Mechatronics, remarked: "Blood can be safely sheared using a miniaturized pump with a mechanically coupled rotating throttle and any CTCs present will be damaged or destroyed. When operated and regulated correctly, the pump/throttle unit will not impair natural blood flow." Tests conducted with the support of Prof. Nicola Aceto (head of the Metastasis Department at the Institute of Oncology at the University of Basel) were successful in that tumor cell clusters were destroyed while blood cells remained intact.

Prof. Clemens Schmitt, professor at the JKU Faculty of Medicine and head of the Department of Haematology and Internal Oncology at the Kepler University Hospital, is impressed by the approach: "Preventing tumors from spreading by metastasis would be an enormous breakthrough in the field of clinical oncology. Prof. Baumgartner and his team have conducted successful experiments showing that cancer cells are more vulnerable to mechanical shear forces than normal, healthy blood cells. The researchers have used this idea to develop a special device, similar to blood washing treatments, to apply shearing forces to the blood, thus inhibiting the cancer cells' ability to metastasize." According to Prof. Schmitt, this particular innovative approach is fascinating because it focuses on a completely new aspect of tumor cells: their special biophysical properties. "Although the current findings are still in its infancy stage and there is a way to go until the approach can be applied to patients, a new path has been forged, paving the way for new, consistent follow-up studies."

An invention with enormous potential
While the device developed at JKU is a demonstrator rather than a mature prototype, it shows that the principle works, meaning CTCs can be destroyed. If these devices become available, there are two potential applications. One would be for external extracorporeal use to remove CTCs in the blood using a device similar to a dialysis machine. This variation could be used after major tumor operations in particular. The second application would be as a permanent implant in the body for patients who have inoperable tumors, thus preventing metastasis.

Prof. Baumgartner emphasized that a great deal of research and a high level of funding is required in order to develop a device to be used for clinical applications and added: "The process must be optimized in order to test limits and energy efficiency, develop bearings, drives, and improve the fluid mechanics in order to be able to operate the device efficiently and safely." In addition, tests have to be carried out on different tumor cells and also guarantee haemocompatibility, meaning the materials used must be “compatible” when coming into contact with the patient’s blood. Clinical studies and approval for medical device can only be carried out after this.   

Even though there is a long road ahead until the device can be used to treat patients, the research team strongly believes in the "tumor cell shredder’s" potential: "The device could give patients who have a poor prognosis more time and a better quality of life."