Comparison of the viscoelastic properties of normal hepatocytes and hepatocellular carcinoma cells under cytoskeletal perturbation

The viscoelastic properties of both hepatocytes and hepatocellular carcinom a (HCC) cells were measured by means of a micropipette aspiration technique . Experimental results were analyzed with a three-element standard linear s olid model, in which an elastic element, K-1, is in parallel with a Maxwell element composed of another elastic element, K-2, in series with a viscous element, mu. Further, we investigated the relevance of viscoelastic proper ties of these two types of cells to the cytoskeleton structures by treating cells with three cytoskeletal perturbing agents, namely cytochalasin D (CD ), colchicine (Col) and vinblastine (VBL). The results showed that the elas tic coefficients, but not viscous coefficient of HCC cells (K-1=103.6 +/- 1 2.6 N m(-2), K-2=42.5 +/- 10.4 N m(-2), mu =4.5 +/-1.9 Pa s, n=30), were si gnificantly higher than the corresponding values for hepatocytes (K-1=87.5 +/- 12.1 N m(-2), K-2=33.3 +/- 10.3 N m(-2), mu =5.9 +/-3.0 Pa s, n=24). Up on treatment with CD, the viscoelastic coefficients of both hepatocytes and HCC cells decreased uniformly, with magnitudes for the decrease in elastic coefficients of HCC cells (K-1: 68.7 to 81.7 N m(-2), 66.3 to 78.9%; K-2: 34.5 to 37.1 N m(-2), 81.2 to 87.3%) larger than those for normal hepatocyt es (K-1: 42.6 to 49.8 N m(-2), 48.7 to 56.9%; K-2: 17.2 to 20.4 N m(-2), 51 .7 to 61.3%). There was a smaller decrease in the viscous coefficient of HC C cells (2.0 to 3.4 Pa s, 44.4 to 75.6%) than that for hepatocytes (3.0 to 3.9 Pa s, 50.8 to 66.1%). Upon treatment with Col and VBL, the elastic coef ficients of hepatocytes generally increased or tended to increase while tho se of HCC cells decreased. The differences in either the pattern or the mag nitude of the effect of cytoskeletal perturbing agent on the viscoelastic p roperties between HCC cells and hepatocytes might possibly reflect differen ces in the state of the cytoskeleton structure and function, or in the cell s' sensitivity to perturbing agent treatment between these two types of cel ls. Changes in the viscoelastic properties of cancer cells might well affec t tumor cell invasion and metastasis as well as interactions between tumor cells and their micro-mechanical environments.