Beschreibung:
The migration and invasion of cancer cells through 3D confined extracellular matricesis coupled to cell mechanics and the mechanics of the extracellular matrix. Cellmechanics is mainly determined by both the mechanics of the largest organelle inthe cell, the nucleus, and the cytoskeletal architecture of the cell. Hence, cytoskeletaland nuclear mechanics are the major contributors to cell mechanics. Among otherfactors, steric hindrances of the extracellular matrix confinement are supposed to affectnuclear mechanics and thus also influence cell mechanics. Therefore, we propose thatthe percentage of invasive cells and their invasion depths into loose and dense 3Dextracellular matrices is regulated by both nuclear and cytoskeletal mechanics. In orderto investigate the effect of both nuclear and cytoskeletal mechanics on the overallcell mechanics, we firstly altered nuclear mechanics by the chromatin de-condensingreagent Trichostatin A (TSA) and secondly altered cytoskeletal mechanics by additionof actin polymerization inhibitor Latrunculin A and the myosin inhibitor Blebbistatin. Infact, we found that TSA-treated MDA-MB-231 human breast cancer cells increasedtheir invasion depth in dense 3D extracellular matrices, whereas the invasion depthsin loose matrices were decreased. Similarly, the invasion depths of TSA-treated MCF-7 human breast cancer cells in dense matrices were significantly increased comparedto loose matrices, where the invasion depths were decreased. These results are alsovalid in the presence of a matrix-metalloproteinase inhibitor GM6001. Using atomicforce microscopy (AFM), we found that the nuclear stiffnesses of both MDA-MB-231 and MCF-7 breast cancer cells were pronouncedly higher than their cytoskeletalstiffness, whereas the stiffness of the nucleus of human mammary epithelial cells wasdecreased compared to their cytoskeleton. TSA treatment reduced cytoskeletal andnuclear stiffness of MCF-7 cells, as expected. However, a softening of the nucleus byTSA treatment may induce a stiffening of the cytoskeleton of MDA-MB-231 cells andsubsequently an apparent stiffening of the nucleus. Inhibiting actin polymerization usingLatrunculin A revealed a softer nucleus of MDA-MB-231 cells under TSA treatment. Thisindicates that the actin-dependent cytoskeletal stiffness seems to be influenced by theTSA-induced nuclear stiffness changes. Finally, the combined treatment with TSA andLatrunculin A further justifies the hypothesis of apparent nuclear stiffening, indicating thatcytoskeletal mechanics seem to be regulated by nuclear mechanics.