Cell News 3/2013
26
physics in the context of mitochondrial division. In particular,
she showed that when bax oligomerizes the membrane tension
is higher. In addition, cholesterol can also stiffen the membrane
as well as negative charged proteins in the membrane. Then Ulf
Anderegg took over to report on the importance of tumor-stro-
ma interactions on cancer. The matrix component hyaluronan
appears to have an important role in tumor growth and in meta-
stasis; in particular, it could serve in the extracellular matrix as
a path for improved cell migration and diffusion of nutrients as
well as a binding site for macrophages.
After the break, Arnoud Sonnenberg presented data on the con-
nection between alpha3 beta1 integrins and CD151 (a tetraspa-
nin). He showed that alpha3 k.o. cells have less keratin 14 and
they migrate faster and formed less tumors in a tumorigenesis
model. In addition, CD151 k.o. cells also induced less tumors in
a tumorigenesis model, but they can support tumor formation
both dependent and independent of alpha3 beta1 integrins. Luke
Casserau, a collaborator of Valerie Weaver who unfortunately
was unable to attend, presented the role of LOX (Lysyl Oxidase)
in reducing the number of circulating cancer cells but not the
amount of tumor vascularization. In particular, he pointed out
that HIF1alpha can be activated by tissue stiffness and subse-
quently increased tension leads to increased slug, snail and zeb1
expression, which are able to switch cells from an epithelial mode
(less motile mode) to a mesenchymal mode of cell invasion. Then,
Rudi Merkel talked about cyclic stress using silicone straining
chambers inducing stress fiber reorientation anti-parallel to the
external stress. In addition, he found that p130Cas is a putative
mechanosensor in focal adhesions but that it has no effect on
the reorientation of cells upon external cyclic stress. Mithila Bu-
rute presented how cells grow on substrates of restricted sizes
(smaller than the normal cell adhesion area) and how two cells
keep their cell-cell junctions. This talk was followed by Kristin
Mills, who spoke about how the mechanics of the tumor micro-
environment affect the tumor shape as well as internal pressure.
A lunch break followed that gave much room to discuss remai-
ning points with the speakers or poster presenters in a familiar
and nice atmosphere. The next session started with Bettina Wei-
gelin, who replaced Peter Friedl, and she discussed the comple-
xity of the tumor microenvironment. She presented in very much
detail the application of multiphoton excitation in a skin-fold
model, where labeled cancer cells migrate into blood vessels in
600 μm depths. Additionally, she nicely imaged the cytotoxic T
lymphocytes killing cancer cells, hopefully the ones that will me-
tastasize. The last talk of the day was given by Harald Herrmann,
who presented that a complex system of nuclear transmembrane
envelope proteins together with nuclear lamins are involved in
the chromatin organization and how the formation of co-fila-
ments affect tension. After session closure the transport to the
boat trip for the speakers was organized.
Here, the impressions of Dennis Discher from the boat trip and
dinner in Leipzig:
“The boat trip and dinner provided a relaxing
outdoor/indoor atmosphere for collegial, cross-continental dis-
cussions about science, politics, the environment, and more. It
was an excellent chance to sit close to other researchers, mix and
exchange notes across various levels, from full professors to juni-
or group leaders, all of whom work to varying extents in the bio-
physics of cancer. It's clearly a small but supportive community,
which made for a pleasurable evening!”
26th September (Thursday)
Even after a long evening, we started early in the morning with
the talk of Ben Fabry about the impact of the mechanical pro-
perties of the extracellular matrix on cancer cell migration in 3D
and contractile force generation. Then, Ulrich Schwarz presented
the cell adhesion to and migration on flat substrates as well as
force generation at focal contacts. He reported on transverse
arcs of stress fibers that are not connected to focal adhesions.
The last talk of this morning session was given by Buzz Baum,
who highlighted the effect of being well-rounded for mitosis,
which needs an initial contraction of the cell. Moreover, he
showed that HeLa cells die, when compressed indicating that
the actin cortex is important to round up.
After the break, Jörg W. Bartsch spoke about the importance of
ADAM proteases (sheddases) on cancer progression. In particular,
he mentioned that ADAM-8 forms a complex with beta1 inte-
grins, which seems to be important for cell motility and metas-
tatic progression of cancer disease. After him, Robert H. Austin
explored game theory and its impact on cancer in a really unusu-
al way. Xavier Trepat took over and stated that leader cells drag
cell sheets forward in tissues. When the tension is increased in a
monolayer to a certain limit, the cells die. Additionally, he talked
about wound healing forces directed towards and away from the
wound ring and its calcium dependence. Adrian Hallou presented
how his model on sheet migration works, simply by modulating
line tension, motile forces und persistence time. Benjamin Ban-
Figure 2:
Prof. Rudolf Leube lecturing on keratin dynamics.
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