title: Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy.
abstract: The cell nucleus is the largest and stiffest organelle rendering it the limiting compartment during migration of invasive tumor cells through dense connective tissue. We here describe a combined atomic force microscopy (AFM)-confocal microscopy approach for measurement of bulk nuclear stiffness together with simultaneous visualization of the cantilever-nucleus contact and the fate of the cell. Using cantilevers functionalized with either tips or beads and spring constants ranging from 0.06-10 N m(-1), force-deformation curves were generated from nuclear positions of adherent HT1080 fibrosarcoma cell populations at unchallenged integrity, and a nuclear stiffness range of 0.2 to 2.5 kPa was identified depending on cantilever type and the use of extended fitting models. Chromatin-decondensating agent trichostatin A (TSA) induced nuclear softening of up to 50%, demonstrating the feasibility of our approach. Finally, using a stiff bead-functionalized cantilever pushing at maximal system-intrinsic force, the nucleus was deformed to 20% of its original height which after TSA treatment reduced further to 5% remaining height confirming chromatin organization as an important determinant of nuclear stiffness. Thus, combined AFM-confocal microscopy is a feasible approach to study nuclear compressibility to complement concepts of limiting nuclear deformation in cancer cell invasion and other biological processes.
authors.affiliation: Department of Cell Biology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands.
authors.forename: Marina
authors.initials: M
authors.lastname: Krause
authors.forename: Joost
authors.initials: J
authors.lastname: Te Riet
authors.forename: Katarina
authors.initials: K
authors.lastname: Wolf
mesh_terms: D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry / Q000187:drug effects / Q000473:pathology*; D004548:Elasticity / Q000187:drug effects; D004867:Equipment Design; D005354:Fibrosarcoma / Q000737:chemistry / Q000473:pathology*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods*
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C012589:trichostatin A