Cell Surface Area and Membrane Folding in Glioblastoma Cell Lines Differing in PTEN and p53 Status

Abstract

Glioblastoma multiforme (GBM) is characterized by rapid growth, invasion and resistance to chemo−/radiotherapy. The complex cell surface morphology with abundant membrane folds, microvilli, filopodia and other membrane extensions is believed to contribute to the highly invasive behavior and therapy resistance of GBM cells. The present study addresses the mechanisms leading to the excessive cell membrane area in five GBM lines differing in mutational status for PTEN and p53. In addition to scanning electron microscopy (SEM), the membrane area and folding were quantified by dielectric measurements of membrane capacitance using the single-cell electrorotation (ROT) technique. The osmotic stability and volume regulation of GBM cells were analyzed by video microscopy. The expression of PTEN, p53, mTOR and several other marker proteins involved in cell growth and membrane synthesis were examined by Western blotting. The combined SEM, ROT and osmotic data provided independent lines of evidence for a large variability in membrane area and folding among tested GBM lines. Thus, DK-MG cells (wild type p53 and wild type PTEN) exhibited the lowest degree of membrane folding, probed by the area-specific capacitance C m = 1.9 µF/cm2. In contrast, cell lines carrying mutations in both p53 and PTEN (U373-MG and SNB19) showed the highest C m values of 3.7–4.0 µF/cm2, which corroborate well with their heavily villated cell surface revealed by SEM. Since PTEN and p53 are well-known inhibitors of mTOR, the increased membrane area/folding in mutant GBM lines may be related to the enhanced protein and lipid synthesis due to a deregulation of the mTOR-dependent downstream signaling pathway. Given that membrane folds and extensions are implicated in tumor cell motility and metastasis, the dielectric approach presented here provides a rapid and simple tool for screening the biophysical cell properties in studies on targeting chemo- or radiotherapeutically the migration and invasion of GBM and other tumor types.

Nanostructure of DNA repair foci revealed by superresolution microscopy

“…Although derived from the same tumor entity, the 2 glioblastoma multiforme (GBM) cell lines used in this study, DK-MG and SNB19, differ markedly in the mutational status of the most prominent tumor suppressors PTEN and p53 (40). Both genes are wild type in DK-MG cells, whereas in the SNB19 cell line, both genes are mutated.…”

Diamond, graphite, and graphene oxide nanoparticles decrease migration and invasiveness in glioblastoma cell lines by impairing extracellular adhesion

“…Glioblastoma cells have a complex actin cytoskeleton-related cell surface morphology with abundant membrane folds, microvilli, and filopodia, which play a role in its invasive phenotype. 3 Cell migration begins with polymerization of actin filaments and extending lamellipodia and filopodia protrusions of the cell membrane. 4 Protrusions are stabilized by focal adhesions and actin cytoskeleton in the form of stress fibers.…”

“…Diamond nanoparticles (ND), graphite nanoparticles (NG), and graphene oxide nanoplatelets (nGO) are carbon allotropes that, although similar in size, have different physical properties. ND has carbon atoms in sp 3 hybridization, whereas NG and nGO have carbon atoms in the sp 2 hexagonal pattern. However, nGO has a unique thickness to surface area ratio, which distinguishes this material from both ND and NG.…”

Highlighting the uniqueness in dielectrophoretic enrichment of circulating tumor cells

“…Memme et al. discussed the increased membrane area and folding in mutant glioblastoma multiforme (GBM) lines, suggesting that it may be related to enhanced protein and lipid synthesis due to a deregulation of the mTOR dependent downstream signalling pathway. It has been observed that the difference in crossover frequency between the blood cells and the CTCs relies on the morphology of the cellular membrane .…”

“…Memmel et al. demonstrated in glioblastoma cells that modulation of PTEN and p53 affected the cell size and membrane synthesis of cells via deregulation of the PI3K/AKT/mTOR pathway . However, the correlation of cell dielectric phenotype with molecular pathways that impact membrane morphology should be further studied.…”