pubmed.ncbi.nlm.nih.gov

Characterizing deformability and surface friction of cancer cells - PubMed

  • ️Tue Jan 01 2013

Characterizing deformability and surface friction of cancer cells

Sangwon Byun et al. Proc Natl Acad Sci U S A. 2013.

Abstract

Metastasis requires the penetration of cancer cells through tight spaces, which is mediated by the physical properties of the cells as well as their interactions with the confined environment. Various microfluidic approaches have been devised to mimic traversal in vitro by measuring the time required for cells to pass through a constriction. Although a cell's passage time is expected to depend on its deformability, measurements from existing approaches are confounded by a cell's size and its frictional properties with the channel wall. Here, we introduce a device that enables the precise measurement of (i) the size of a single cell, given by its buoyant mass, (ii) the velocity of the cell entering a constricted microchannel (entry velocity), and (iii) the velocity of the cell as it transits through the constriction (transit velocity). Changing the deformability of the cell by perturbing its cytoskeleton primarily alters the entry velocity, whereas changing the surface friction by immobilizing positive charges on the constriction's walls primarily alters the transit velocity, indicating that these parameters can give insight into the factors affecting the passage of each cell. When accounting for cell buoyant mass, we find that cells possessing higher metastatic potential exhibit faster entry velocities than cells with lower metastatic potential. We additionally find that some cell types with higher metastatic potential exhibit greater than expected changes in transit velocities, suggesting that not only the increased deformability but reduced friction may be a factor in enabling invasive cancer cells to efficiently squeeze through tight spaces.

Keywords: biophysics; biosensors; cell mechanics; cell stiffness; suspended microchannel resonator.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.

Schematic diagram of the instrument and data extracted from the measurement. (A) Suspended microchannel resonator (SMR) with a constriction (6 µm wide, 15 µm deep, and 50 µm long) located at the apex. A cell passing through an embedded microfluidic channel is deformed as it flows into the constriction. Numbers 1–5 indicate different positions within the microchannel to demonstrate the trajectory of a cell flowing inside the channel. (B) The resonant frequency response of the SMR as the cell passes through the microfluidic channel. The numbers 1–5 correspond to the position of the cell in the cantilever, as marked in A. The height of the peak corresponds to the buoyant mass of the cell (1 → 2). The cell slows down as it deforms to enter the constriction (entry), and then speeds up as it travels through the constriction (transit). The passage time corresponds to the sum of the entry and transit times (3 → 4). (C) Power law dependence of passage time versus buoyant mass for the H1975 cell line (n = 967). Measurements were acquired with a PEG-coated channel surface and using a pressure drop of 1.8 psi.

Fig. 2.
Fig. 2.

Trajectories observed in the SMR can be predicted with high accuracy from a power law viscosity model, similar to Tsai et al. (28). (A) Prediction of entry times into the constriction for H1975 cells (test set, n = 343). Cells are modeled from a training set (n = 388) as having a shear rate-dependent viscosity μ = μ0(γ)−b, where a single best-fit model is chosen for all of the cells. The black line shows equality between predicted and observed entry times, the black dots represent individual cells, and the red dashed line is the best fit line for the test set. Predicted entry times and observed entry times demonstrate a high correlation of r = 0.76 in log space. (B) Prediction of the detailed trajectory through the constriction using the power law viscosity model, shown for a typical cell with its own best-fit model. The blue line represents the observed trajectory of the cell through the constriction, the dotted red line represents the model prediction, and the solid red line shows the model prediction when an initial projection is incorporated into the model.

Fig. 3.
Fig. 3.

Power law relationship between passage time and cell buoyant mass is demonstrated by measurements of various cell lines, including (A) mouse embryonic fibroblast (MEF) (n = 511), (B) H1650 (n = 639), (C) TMet (blue, n = 512), L1210 (red, n = 1401), (D) TMet-Nkx2-1 (blue, n = 1065), TMet (red, n = 1028), (E) TnonMet (blue, n = 252), TMet (red, same dataset as in C), (F) HCC827 (blue, n = 278), and H1975 (red, n = 307). Measurements were made in a PEG-coated channel under a constant pressure drop of 0.9 psi. The gray dots shown as a background correspond to the collection of all measured cell lines. Notably, as shown in C, adherent mouse lung cancer cells in suspension require a longer time to pass through the constriction than mouse blood cells of similar buoyant mass. Three pairs of cancer cell lines having different known metastatic potentials are compared in D–F. In each pair, the cell line with the higher metastatic potential (red dots) exhibits shorter passage times than those with the lower metastatic potential (blue dots). The difference in passage time was statistically significant for all three pairs in D–F (

Fig. S4

).

Fig. 4.
Fig. 4.

Extracting entry and transit velocities from single cell measurement. (A) The resonant frequency response (positions 3–5 in Fig. 1B) is converted to the normalized position of the cell in the cantilever and plotted versus time. The length of the cantilever was normalized to 1 to represent the cell’s position, where 1 and 0 correspond to the tip and base, respectively. (B) Cell velocity is obtained by taking the time derivative of the normalized position. Entry and transit velocities are extracted at specific locations that correspond to the entrance and the inside of the constriction, respectively. (C) Entry (green) and transit (orange) velocities versus buoyant mass for the data set from Fig. 1C.

Fig. 5.
Fig. 5.

Changes in the entry and transit velocities of H1975 cells after perturbing either deformability or microchannel surface charge. (A) Entry velocity and (B) transit velocity versus buoyant mass for H1975 untreated (blue, n = 843) and treated with LatB (red, n = 907, 5 µg/mL for 30 min) measured in a PEG-coated channel. Treatment with LatB decreases the passage time of H1975 (

Fig. S5

) and induces a larger shift in entry velocity than transit velocity. (C) A ratio of velocities from the two conditions was calculated as in

Fig. S12

. Changing the deformability of the cell by perturbing its actin cytoskeleton induces a 3.8-fold increase in the entry velocity, and only a 1.5-fold increase in the transit velocity. (D) Entry velocity and (E) transit velocity versus buoyant mass for H1975 cells passing through a microchannel whose surface is coated with positively charged PLL (blue, n = 345) or neutral PEG (red, n = 649). PLL increases the passage time (

Fig. S5

) and results in a greater shift in transit velocity than entry velocity. (F) Changing the surface friction from PEG to PLL caused entry velocity to decrease 2.3-fold, and transit velocity to decrease 4.7-fold. Error bars represent 95% confidence intervals. All measurements were acquired using a pressure drop of 1.8 psi.

Fig. 6.
Fig. 6.

Three pairs of cancer cell lines having different metastatic potentials (TMet versus TMet-Nkx2-1, red; TMet versus TnonMet, green; and H1975 versus HCC827, blue) were compared by measuring the changes in entry velocity (VE) and transit velocity (VT) with a PEG-coated channel surface. (A) Ratio of VE and ratio of VT for three pairs of cancer cell lines. VE and VT ratios connected by a line represent one replicate. In contrast to TMet versus TMet-Nkx2-1, TMet versus TnonMet and H1975 versus HCC827 show that a significant change in transit velocity is associated with a change in entry velocity, suggesting that the role of friction is more significant in those pairs. TMet versus TMet-Nkx2-1, TMet versus TnonMet, and H1975 versus HCC827 were repeated from different cultures three, six, and three times, respectively. Error bars represent 95% confidence intervals. (B) For each measurement, the ratio of VE divided by the ratio of VT is shown, which confirms that the proportional change in VE relative to VT was significantly different among the three pairs (*P < 0.05, Mann–Whitney–Wilcoxon test). Measurements were acquired using a pressure drop of 0.9 psi for the mouse cell lines (TMet, TMet-Nkx2-1, TnonMet) and a higher drop of 1.8 psi for the human cell lines (H1975, HCC827) to account for their larger size.

Fig. 7.
Fig. 7.

Passage time versus buoyant mass measurements delineate H1650 cells from human blood cells. (A) Peaks detected from the blood cells spiked with H1650 cells, where each peak represents the transit of a cell through the SMR. (B) Passage time versus buoyant mass for H1650 and blood cells. Blood cells (green, n = 2832) traveled through the constriction several orders of magnitude faster than H1650 cells (blue, n = 404), suggesting that H1650 cells could be distinguished from blood cell populations by passage time. Indeed, the spiked sample (red, n = 10810) shows a subpopulation whose passage time and buoyant mass match that of the H1650 cells. Measurements were acquired with a PEG-coated channel surface and using a pressure drop of 1.5 psi.

Similar articles

Cited by

References

    1. Kalluri R, Weinberg RA. The basics of epithelial-mesenchymal transition. J Clin Invest. 2009;119(6):1420–1428. - PMC - PubMed
    1. Wirtz D, Konstantopoulos K, Searson PC. The physics of cancer: The role of physical interactions and mechanical forces in metastasis. Nat Rev Cancer. 2011;11(7):512–522. - PMC - PubMed
    1. Kumar S, Weaver VM. Mechanics, malignancy, and metastasis: The force journey of a tumor cell. Cancer Metastasis Rev. 2009;28(1–2):113–127. - PMC - PubMed
    1. Drury JL, Dembo M. Aspiration of human neutrophils: Effects of shear thinning and cortical dissipation. Biophys J. 2001;81(6):3166–3177. - PMC - PubMed
    1. Hochmuth RM. Micropipette aspiration of living cells. J Biomech. 2000;33(1):15–22. - PubMed

Publication types

MeSH terms

Substances