Our Soft Matter Physics group focuses on a quantitative understanding of biological cell phenotype and function from a complex, emerging materials perspective encompassing all length scales from molecules to tissues, which places our group in a pioneering and leading position in the novel area Physics of Cancer.
As illustrated in our article "Emergent complexity of the cytoskeleton: from single filaments to tissues" , which is among the most read papers in Advances in Physics (IF 20.833) every year, the emphasis of the Soft Matter Physics group is on the material properties of biological cells as key determinants of their character and functions, including tumor progression. This requires an integral approach that spans the length scales from molecules to tissues. For this research the group is uniquely positioned by its ability to concurrently purify cytoskeletal proteins and have access to clinical tissue samples.
Changes in cell mechanics such as increased contractility are essential for metastatic invasiveness. Surprisingly, contractility of actin bundles cannot only be induced by molecular motors, but also by molecular crowding within the cytoplasm . Based on an extension of thermal fluctuation spectroscopy, first direct measurements of the bending modulus of cell membranes revealed that the stiffness of membranes of mamma and cervix carcinoma decreases by an order of magnitude, which enhances cell motility [3, 4]. Novel thermorheological studies of the time-temperature superposition principle permit us to separate active and passive mechanical processes within cells [5, 6].
We have explained the down regulation of keratin that is characteristic
to the epithelial-mesenchymal transition (EMT), which induces cancer metastasis.
In carcinomas the loss of keratin softens cancer cells and thus increases
their invasiveness . Tumor biology attributes the escape of cancer cells
from tumors to loss of cell-cell adhesion, i.e. the decrease of surface
tension at the tumor margin. Our comprehensive study revealed that adhesion
is not the main factor holding cancer cells back . Cancer cell assemblies
even do not behave allways as Newtonian fluids, which is a prerequisite
for differential adhesion, and are in a jammed solid-like state . The
resulting hypothesis that the EMT is an unjamming transition has found
broad, positive attention .