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

Harnessing atomic force microscopy-based single-cell analysis to advance physical oncology

Single-cell analysis is an emerging and promising frontier in the field of life sciences, which is expected to facilitate the exploration of fundamental laws of physiological and pathological processes. Single-cell analysis allows experimental access to cell-to-cell heterogeneity to reveal the distinctive behaviors of individual cells, offering novel opportunities to dissect the complexity of severe human diseases such as cancers. Among the single-cell analysis tools, atomic force microscopy (AFM) is a powerful and versatile one which is able to nondestructively image the fine topographies and quantitatively measure multiple mechanical properties of single living cancer cells in their native states under aqueous conditions with unprecedented spatiotemporal resolution. Over the past few decades, AFM has been widely utilized to detect the structural and mechanical behaviors of individual cancer cells during the process of tumor formation, invasion, and metastasis, yielding numerous unique insights into tumor pathogenesis from the biomechanical perspective and contributing much to the field of cancer mechanobiology. Here, the achievements of AFM-based analysis of single cancer cells to advance physical oncology are comprehensively summarized, and challenges and future perspectives are also discussed. RESEARCH HIGHLIGHTS: Achievements of AFM in characterizing the structural and mechanical behaviors of single cancer cells are summarized, and future directions are discussed. AFM is not only capable of visualizing cellular fine structures, but can also measure multiple cellular mechanical properties as well as cell-generated mechanical forces. There is still plenty of room for harnessing AFM-based single-cell analysis to advance physical oncology.

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.