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Atomic force microscopy-based microrheology reveals significant differences in the viscoelastic response between malign and benign cell lines.

Rother J, Nöding H, Mey I, Janshoff A - Open Biol (2014)

Bottom Line: Mechanical phenotyping of cells by atomic force microscopy (AFM) was proposed as a novel tool in cancer cell research as cancer cells undergo massive structural changes, comprising remodelling of the cytoskeleton and changes of their adhesive properties.In this work, we focused on the mechanical properties of human breast cell lines with different metastatic potential by AFM-based microrheology experiments.Including also other cell lines from different organs shows that the loss tangent (G″/G') increases generally with the metastatic potential from MCF-10A representing benign cells to highly malignant MDA-MB-231 cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physical Chemistry, Tammannstrasse 6, 37077 Göttingen, Germany.

ABSTRACT
Mechanical phenotyping of cells by atomic force microscopy (AFM) was proposed as a novel tool in cancer cell research as cancer cells undergo massive structural changes, comprising remodelling of the cytoskeleton and changes of their adhesive properties. In this work, we focused on the mechanical properties of human breast cell lines with different metastatic potential by AFM-based microrheology experiments. Using this technique, we are not only able to quantify the mechanical properties of living cells in the context of malignancy, but we also obtain a descriptor, namely the loss tangent, which provides model-independent information about the metastatic potential of the cell line. Including also other cell lines from different organs shows that the loss tangent (G″/G') increases generally with the metastatic potential from MCF-10A representing benign cells to highly malignant MDA-MB-231 cells.

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Related in: MedlinePlus

Loss tangent η of all cell lines with different metastatic potential computed at an oscillation frequency of 100 Hz (two force maps, corresponding to 5–20 cells, depending on cell size).
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RSOB140046F6: Loss tangent η of all cell lines with different metastatic potential computed at an oscillation frequency of 100 Hz (two force maps, corresponding to 5–20 cells, depending on cell size).

Mentions: On the other hand, Zhang et al. [6] report on a stiffening of hepatocellular carcinoma cells compared with benign hepatocytes. These contradictory results mirror the difficulty of categorizing the malignancy of cancer cells according to their softness (i.e. Young's modulus). Nevertheless, the malignant transformation of benign cells into metastatic cancer cells results from a change in the protein expression pattern of the cell, which is accompanied by a reorganization of the cytoskeleton and a change in the adhesive properties of the cells [3,31]. Taking the histological origin of the cells into account, we can confirm the trend towards softer cancer cells compared with stiffer benign cells in our measurements. The benign epithelial cell lines NMuMG, MCF-10A and MDCKII, as well as the very stiff fibroblasts, show higher values for G′ compared with the corresponding malignant cancer cell lines from the same organ. However, A549 cells do not follow a potentially universal trend of low elastic modules observed for malignant cells. Problems of using the elastic modulus for the cancer cell detection have been discussed recently by Lekka & Laidler [32]. By contrast, the loss tangent η as a model-independent parameter (as it is solely described by the phase shift between excitation of the cantilever and its response) does not assume a particular geometry of indenter or cell. Thus, it is independent of the indentation depth and details of contact mechanics providing a quantitative measure of the overall rheological behaviour of the sample. Figure 6 shows the loss tangent η determined at an oscillation frequency of 100 Hz for all cell lines. The complete frequency dependence of the loss tangent is depicted in figure 4 for the three breast cell lines. Electronic supplementary material, figure S6 compares the benign cell line MCF-10A with the malign one MDA-MB-231 at the full frequency range, demonstrating that the non-tumorigenic cell line possesses a smaller loss tangent at all frequencies. At 100 Hz oscillation frequency, both epithelial cell lines (MDCKII and NMuMG cells) and the fibroblasts (NIH 3T3 cells) exhibit a loss tangent η of approximately 1.1 with a narrow distribution. All cancer cell lines have significantly higher median values of η, ranging from 1.3 in the case of A549 cell up to 2 and 3 in the case of MDA-MB231 cells and CaKi-1 cells, respectively. The effect is also accompanied by a broadening of the distribution. The elevated values of η can be interpreted as a more fluid-like behaviour of the malign cancer cells compared with the benign cell lines. We interpret this effect by the concomitant migratory behaviour of cancer cells. To form metastases, cancer cells have to detach from their primary tumour and invade the parenchyma and the vasculature [33]. During this process, the cancer cells have to undergo large deformations (i.e. during intra- and extravasation), while they are ‘squeezing’ themselves through endothelial cell layers. Hence, a more fluid-like behaviour of the cells facilitates this process, which is critical for the formation of metastasis in tissues far away from the primary tumour. While a large loss tangent identifies a more fluid-like behaviour it does not automatically mean that the stiffness of the cell is low. It just means that viscosity dominates over elasticity.Figure 6.


Atomic force microscopy-based microrheology reveals significant differences in the viscoelastic response between malign and benign cell lines.

Rother J, Nöding H, Mey I, Janshoff A - Open Biol (2014)

Loss tangent η of all cell lines with different metastatic potential computed at an oscillation frequency of 100 Hz (two force maps, corresponding to 5–20 cells, depending on cell size).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4042852&req=5

RSOB140046F6: Loss tangent η of all cell lines with different metastatic potential computed at an oscillation frequency of 100 Hz (two force maps, corresponding to 5–20 cells, depending on cell size).
Mentions: On the other hand, Zhang et al. [6] report on a stiffening of hepatocellular carcinoma cells compared with benign hepatocytes. These contradictory results mirror the difficulty of categorizing the malignancy of cancer cells according to their softness (i.e. Young's modulus). Nevertheless, the malignant transformation of benign cells into metastatic cancer cells results from a change in the protein expression pattern of the cell, which is accompanied by a reorganization of the cytoskeleton and a change in the adhesive properties of the cells [3,31]. Taking the histological origin of the cells into account, we can confirm the trend towards softer cancer cells compared with stiffer benign cells in our measurements. The benign epithelial cell lines NMuMG, MCF-10A and MDCKII, as well as the very stiff fibroblasts, show higher values for G′ compared with the corresponding malignant cancer cell lines from the same organ. However, A549 cells do not follow a potentially universal trend of low elastic modules observed for malignant cells. Problems of using the elastic modulus for the cancer cell detection have been discussed recently by Lekka & Laidler [32]. By contrast, the loss tangent η as a model-independent parameter (as it is solely described by the phase shift between excitation of the cantilever and its response) does not assume a particular geometry of indenter or cell. Thus, it is independent of the indentation depth and details of contact mechanics providing a quantitative measure of the overall rheological behaviour of the sample. Figure 6 shows the loss tangent η determined at an oscillation frequency of 100 Hz for all cell lines. The complete frequency dependence of the loss tangent is depicted in figure 4 for the three breast cell lines. Electronic supplementary material, figure S6 compares the benign cell line MCF-10A with the malign one MDA-MB-231 at the full frequency range, demonstrating that the non-tumorigenic cell line possesses a smaller loss tangent at all frequencies. At 100 Hz oscillation frequency, both epithelial cell lines (MDCKII and NMuMG cells) and the fibroblasts (NIH 3T3 cells) exhibit a loss tangent η of approximately 1.1 with a narrow distribution. All cancer cell lines have significantly higher median values of η, ranging from 1.3 in the case of A549 cell up to 2 and 3 in the case of MDA-MB231 cells and CaKi-1 cells, respectively. The effect is also accompanied by a broadening of the distribution. The elevated values of η can be interpreted as a more fluid-like behaviour of the malign cancer cells compared with the benign cell lines. We interpret this effect by the concomitant migratory behaviour of cancer cells. To form metastases, cancer cells have to detach from their primary tumour and invade the parenchyma and the vasculature [33]. During this process, the cancer cells have to undergo large deformations (i.e. during intra- and extravasation), while they are ‘squeezing’ themselves through endothelial cell layers. Hence, a more fluid-like behaviour of the cells facilitates this process, which is critical for the formation of metastasis in tissues far away from the primary tumour. While a large loss tangent identifies a more fluid-like behaviour it does not automatically mean that the stiffness of the cell is low. It just means that viscosity dominates over elasticity.Figure 6.

Bottom Line: Mechanical phenotyping of cells by atomic force microscopy (AFM) was proposed as a novel tool in cancer cell research as cancer cells undergo massive structural changes, comprising remodelling of the cytoskeleton and changes of their adhesive properties.In this work, we focused on the mechanical properties of human breast cell lines with different metastatic potential by AFM-based microrheology experiments.Including also other cell lines from different organs shows that the loss tangent (G″/G') increases generally with the metastatic potential from MCF-10A representing benign cells to highly malignant MDA-MB-231 cells.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physical Chemistry, Tammannstrasse 6, 37077 Göttingen, Germany.

ABSTRACT
Mechanical phenotyping of cells by atomic force microscopy (AFM) was proposed as a novel tool in cancer cell research as cancer cells undergo massive structural changes, comprising remodelling of the cytoskeleton and changes of their adhesive properties. In this work, we focused on the mechanical properties of human breast cell lines with different metastatic potential by AFM-based microrheology experiments. Using this technique, we are not only able to quantify the mechanical properties of living cells in the context of malignancy, but we also obtain a descriptor, namely the loss tangent, which provides model-independent information about the metastatic potential of the cell line. Including also other cell lines from different organs shows that the loss tangent (G″/G') increases generally with the metastatic potential from MCF-10A representing benign cells to highly malignant MDA-MB-231 cells.

Show MeSH
Related in: MedlinePlus