The softening of human bladder cancer cells happens at an early stage of the malignancy process

Abstract

SummaryVarious studies have demonstrated that alterations in the deformability of cancerous cells are strongly linked to the actin cytoskeleton. By using atomic force microscopy (AFM), it is possible to determine such changes in a quantitative way in order to distinguish cancerous from non-malignant cells. In the work presented here, the elastic properties of human bladder cells were determined by means of AFM. The measurements show that non-malignant bladder HCV29 cells are stiffer (higher Young’s modulus) than cancerous cells (HTB-9, HT1376, and T24 cell lines). However, independently of the histological grade of the studied bladder cancer cells, all cancerous cells possess a similar level of the deformability of about a few kilopascals, significantly lower than non-malignant cells. This underlines the diagnostic character of stiffness that can be used as a biomarker of bladder cancer. Similar stiffness levels, observed for cancerous cells, cannot be fully explained by the organization of the actin cytoskeleton since it is different in all malignant cells. Our results underline that it is neither the spatial organization of the actin filaments nor the presence of stress fibers, but the overall density and their 3D-organization in a probing volume play the dominant role in controlling the elastic response of the cancerous cell to an external force.

Cell stiffness determined by atomic force microscopy and its correlation with cell motility

“…Thus, due to the differences in microenvironments, cells derived from normal tissues and tumors are intrinsically different in their stiffness, which allows Young's modulus to be a reliable biomarker in the evaluation of metastasis and the motility of cells. In addition, the morphological observations support this opinion experimentally, showing that the cancerous cells usually have decreased stress fibers [25,29,33,67,68], increased cortical actin [25,33], and more lamellipodia [26,65], which benefit the invasion of cells by decreasing adhesion with the substrate and increasing the contraction forces for deformation and protrusion [27,64]. Taking into account that the nuclei are usually softer in cells with higher motility [58] and that the cortex actin network is much softer than the stress fibers [41], it is reasonable to detect a lower Young's modulus in metastatic carcinoma cells.…”

“…A close correlation between actin filaments and cell stiffness has been demonstrated by the use of disruptive pharmacological agents, such as cytochalasin D [28,29], latrunculin A [10], and latrunculin B [30,31]. The dissolution of the actin cytoskeleton led to a significant decrease in Young's modulus,…”

Time-resolved nanomechanics of a single cell under the depolymerization of the cytoskeleton

“…25,26 Several experiments have demonstrated the existence of viscous processes in the cytoskeleton remodeling and in the inner cell dynamics. [26][27][28] In fact, stiffness measurements performed on cancer cells of different pathological degrees 17,29,30 have given similar elastic (Young) moduli values. These findings could be related to the limitations of stiffness measurements to describe the mechanical state of a cell.…”

Local mechanical properties of bladder cancer cells measured by AFM as a signature of metastatic potential

“…Ramos et al [20] investigated the elastic properties of non-malignant and cancerous bladder cell lines using the AFM. They found that normal cells are stiffer than cancer cells.…”