Temporal and molecular dynamics of human metastatic breast carcinoma cell adhesive interactions with human bone marrow endothelium analyzed by single-cell force spectroscopy

Breast adenocarcinoma cells adhere stronger to brain pericytes than to endothelial cells

Most of the malignancies detected within the brain parenchyma are of metastatic origin. As the brain lacks classical lymphatic circulation, the primary way for metastasis relies on hematogenous routes. Dissemination of metastatic cells to the brain implies attachment to the luminal surface of brain endothelial cells, transmigration through the vessel wall, and adhesion to the brain surface of the vasculature. During this process, tumor cells must interact with brain endothelial cells and later on with pericytes. Physical interaction between tumor cells and brain vascular cells might be crucial in the successful extravasation of metastatic cells through blood vessels and later in their survival within the brain environment. Therefore, we applied single-cell force spectroscopy to investigate the nanoscale adhesive properties of living breast adenocarcinoma cells to brain endothelial cells and pericytes. We found target cell type-dependent adhesion characteristics, i.e. increased adhesion of the tumor cells to pericytes in comparison to endothelial cells, which underlines the existence of metastatic potential-related nanomechanical differences relying partly on membrane tether dynamics. Varying adhesion strength of the tumor cells to different cell types of brain vessels presumably reflects the transitory adhesion to endothelial cells before extravasation and the long-lasting strong interaction with pericytes during survival and proliferation in the brain. Our results highlight the importance of specific mechanical interactions between tumor cells and host cells during metastasis formation.

Single-cell force spectroscopy of fluid flow-tuned cell adhesion for dissecting hemodynamics in tumor metastasis

Cell adhesion plays an important role in regulating the metastasis of cancer cells, and atomic force microscopy (AFM)-based single-cell force spectroscopy (SCFS) has become an important method to directly measure the adhesion forces of individual cells. Particularly, bodily fluid flow environments strongly affect the functions and behaviors of metastatic cells for successful dissemination. Nevertheless, the interactions between fluidic flow medium environment and cell adhesion remain poorly understood. In this work, AFM-based SCFS was exploited to examine the effects of fluidic flow environment on cellular adhesion. A fluidic cell culture medium device was used to simulate the fluidic flow environment experienced by cancer cells during metastasis, which was combined with AFM-based SCFS assay. A single living cancer cell was attached to the AFM tipless cantilever to prepare the single-cell probe for performing SCFS experiments on the mesothelial cells grown under the fluidic flow medium conditions, and the effects of experimental parameters (retraction speed, contact time, loading force) on the measured cellular adhesion forces were analyzed. Experimental results of SCFS assay show that cellular adhesion forces significantly decrease after growth in fluidic flow medium, whereas cellular adhesion forces increase after growth in static culture medium. Experiments performed with the use of spherical probes coated with cell adhesion-associated biomolecules also show the weakening of cell adhesion after growth in fluidic flow cell culture medium, which was subsequently confirmed by the confocal fluorescence microscopy experiments of cell adhesion molecules, vividly illustrating the remarkable effects of fluidic flow environment on cellular adhesion. The study provides a new approach to detect adhesion force dynamics involved in the interactions between cells and the fluidic flow environment at the single-cell level, which will facilitate dissecting the role of hemodynamics in tumor metastasis.

Changes in dynamics of tumor/endothelial cell adhesive interactions depending on endothelial cell growth state and elastic properties

Cancer cell adhesion to the endothelium is a crucial process in hematogenous metastasis, but how the integrity of the endothelial barrier and endothelial cell (EC) mechanical properties influence the adhesion between metastatic cancer cells and the endothelium remain unclear. In the present study, we have measured the adhesion between single cancer cells and two types of ECs at various growth states and their mechanical properties (elasticity) using atomic force microscopy single cell force spectroscopy. We demonstrated that the EC stiffness increased and adhesion with cancer cells decreased, as ECs grew from a single cell to a confluent state and developed cell-cell contacts, but this was reversed when confluent cells returned to a single state in a scratch assay. Our results suggest that the integrity of the endothelial barrier is an important factor in reducing the ability of the metastatic tumor cells to adhere to the vascular endothelium, extravasate and lodge in the vasculature of a distant organ where secondary metastatic tumors would develop.

Nano-Motion Analysis for Rapid and Label Free Assessing of Cancer Cell Sensitivity to Chemotherapeutics

Background and Objectives: Optimization of chemotherapy is crucial for cancer patients. Timely and costly efficient treatments are emerging due to the increasing incidence of cancer worldwide. Here, we present a methodology of nano-motion analysis that could be developed to serve as a screening tool able to determine the best chemotherapy option for a particular patient within hours. Materials and Methods: Three different human cancer cell lines and their multidrug resistant (MDR) counterparts were analyzed with an atomic force microscope (AFM) using tipless cantilevers to adhere the cells and monitor their nano-motions. Results: The cells exposed to doxorubicin (DOX) differentially responded due to their sensitivity to this chemotherapeutic. The death of sensitive cells corresponding to the drop in signal variance occurred in less than 2 h after DOX application, while MDR cells continued to move, even showing an increase in signal variance. Conclusions: Nano-motion sensing can be developed as a screening tool that will allow simple, inexpensive and quick testing of different chemotherapeutics for each cancer patient. Further investigations on patient-derived tumor cells should confirm the method’s applicability.

A perspective view on the nanomotion detection of living organisms and its features

The insurgence of newly arising, rapidly developing health threats, such as drug-resistant bacteria and cancers, is one of the most urgent public-health issues of modern times. This menace calls for the development of sensitive and reliable diagnostic tools to monitor the response of single cells to chemical or pharmaceutical stimuli. Recently, it has been demonstrated that all living organisms oscillate at a nanometric scale and that these oscillations stop as soon as the organisms die. These nanometric scale oscillations can be detected by depositing living cells onto a micro-fabricated cantilever and by monitoring its displacements with an atomic force microscope-based electronics. Such devices, named nanomotion sensors, have been employed to determine the resistance profiles of life-threatening bacteria within minutes, to evaluate, among others, the effect of chemicals on yeast, neurons, and cancer cells. The data obtained so far demonstrate the advantages of nanomotion sensing devices in rapidly characterizing microorganism susceptibility to pharmaceutical agents. Here, we review the key aspects of this technique, presenting its major applications. and detailing its working protocols.

Differentiation of single lymphoma primary cells and normal B-cells based on their adhesion to mesenchymal stromal cells in optical tweezers

We have adapted a non-invasive method based on optical tweezers technology to differentiate between the normal B-cells and the B-cell non-Hodgkin lymphoma (B-NHL) cells derived from clinical samples. Our approach bases on the nascent adhesion between an individual B-cell and a mesenchymal stromal cell. In this study, a single B-cell was trapped and optically seeded on a mesenchymal stromal cell and kept in a direct contact with it until a stable connection between the cells was formed in time scale. This approach allowed us to avoid the introduction of any exogenous beads or chemicals into the experimental setup which would have affected the cell-to-cell adhesion. Here, we have provided new evidence that aberrant adhesive properties found in transformed B-cells are related to malignant neoplasia. We have demonstrated that the mean time required for establishing adhesive interactions between an individual normal B-cell and a mesenchymal stromal cell was 26.7 ± 16.6 s, while for lymphoma cell it was 208.8 ± 102.3 s, p < 0.001. The contact time for adhesion to occur ranged from 5 to 90 s and from 60 to 480 s for normal B-cells and lymphoma cells, respectively. This method for optically controlled cell-to-cell adhesion in time scale is beneficial to the successful differentiation of pathological cells from normal B-cells within the fine needle aspiration biopsy of a clinical sample. Additionally, variations in time-dependent adhesion among subtypes of B-NHL, established here by the optical trapping, confirm earlier results pertaining to cell heterogeneity.