Pore Shape Defines Paths of Metastatic Cell Migration.

Invasion of dense tissues by cancer cells involves the interplay between the penetration resistance offered by interstitial pores and the deformability of cells. Metastatic cancer cells find optimal paths of minimal resistance through an adaptive path-finding process, which leads to successful dissemination. The physical limit of nuclear deformation is related to the minimal cross section of pores that can be successfully penetrated. However, this single biophysical parameter does not fully describe the architectural complexity of tissues featuring pores of variable area and shape. Here, employing laser nanolithography, we fabricate pore microenvironment models with well-controlled pore shapes, through which human breast cells (MCF10A) and their metastatic offspring (MCF10CA1a.cl1) could pervade. In these experimental settings, we demonstrate that the actual pore shape, and not only the cross section, is a major and independent determinant of cancer penetration efficiency. In complex architectures containing pores demanding large deformations from invading cells, tall and narrow rectangular openings facilitate cancer migration. In addition, we highlight the characteristic traits of the explorative behavior enabling metastatic cells to identify and select such pore shapes in a complex multishape pore environment, pinpointing paths of least resistance to invasion.

Micro-engineering and nano-engineering approaches to investigate tumour ecosystems.

The interactions among tumour cells, the tumour microenvironment (TME) and non-tumour tissues are of interest to many cancer researchers. Micro-engineering approaches and nanotechnologies are under extensive exploration for modelling these interactions and measuring them in situ and in vivo to investigate therapeutic vulnerabilities in cancer and extend a systemic view of tumour ecosystems. Here we highlight the greatest opportunities for improving the understanding of tumour ecosystems using microfluidic devices, bioprinting or organ-on-a-chip approaches. We also discuss the potential of nanosensors that can transmit information from within the TME or elsewhere in the body to address scientific and clinical questions about changes in chemical gradients, enzymatic activities, metabolic and immune profiles of the TME and circulating analytes. This Review aims to connect the cancer biology and engineering communities, presenting biomedical technologies that may expand the methodologies of the former, while inspiring the latter to develop approaches for interrogating cancer ecosystems.

Cell cycle-dependent force transmission in cancer cells.

The generation of traction forces and their transmission to the extracellular environment supports the disseminative migration of cells from a primary tumor. In cancer cells, the periodic variation of nuclear stiffness during the cell cycle provides a functional link between efficient translocation and proliferation. However, the mechanical framework completing this picture remains unexplored. Here, the Fucci2 reporter was expressed in various human epithelial cancer cells to resolve their cell cycle phase transition. The corresponding tractions were captured by a recently developed reference-free confocal traction-force microscopy platform. The combined approach was conducive to the analysis of phase-dependent force variation at the level of individual integrin contacts. Detected forces were invariably higher in the G1 and early S phases than in the ensuing late S/G2, and locally colocalized with high levels of paxillin phosphorylation. Perturbation of paxillin phosphorylation at focal adhesions, obtained through the biochemical inhibition of focal adhesion kinase (FAK) or the transfection of nonphosphorylatable or phosphomimetic paxillin mutants, significantly diminished the force transmitted to the substrate. These data demonstrate a reproducible modulation of force transmission during the cell cycle progression of cancer cells, instrumental to their invasion of dense environments. In addition, they delineate a model in which paxillin phosphorylation supports the mechanical maturation of adhesions relaying forces to the substrate.

A RAB35-p85/PI3K axis controls oscillatory apical protrusions required for efficient chemotactic migration.

How cells move chemotactically remains a major unmet challenge in cell biology. Emerging evidence indicates that for interpreting noisy, shallow gradients of soluble cues a system must behave as an excitable process. Here, through an RNAi-based, high-content screening approach, we identify RAB35 as necessary for the formation of growth factors (GFs)-induced waves of circular dorsal ruffles (CDRs), apically restricted actin-rich migratory protrusions. RAB35 is sufficient to induce recurrent and polarized CDRs that travel as propagating waves, thus behaving as an excitable system that can be biased to control cell steering. Consistently, RAB35 is essential for promoting directed chemotactic migration and chemoinvasion of various cells in response to gradients of motogenic GFs. Molecularly, RAB35 does so by directly regulating the activity of p85/PI3K polarity axis. We propose that RAB35 is a molecular determinant for the control of an excitable, oscillatory system that acts as a steering wheel for GF-mediated chemotaxis and chemoinvasion.

Author Correction: A RAB35-p85/PI3K axis controls oscillatory apical protrusions required for efficient chemotactic migration.

The originally published version of this Article contained an error in the name of the author Salvatore Corallino, which was incorrectly given as Corallino Salvatore. This has now been corrected in both the PDF and HTML versions of the Article.

A Nanoprinted Model of Interstitial Cancer Migration Reveals a Link between Cell Deformability and Proliferation.

Metastatic progression of tumors requires the coordinated dissemination of cancerous cells through interstitial tissues and their replication in distant body locations. Despite their importance in cancer treatment decisions, key factors, such as cell shape adaptation and the role it plays in dense tissue invasion by cancerous cells, are not well understood. Here, we employ a 3D electrohydrodynamic nanoprinting technology to generate vertical arrays of topographical pores that mimic interstitial tissue resistance to the mesenchymal migration of cancerous cells, in order to determine the effect of nuclear size, cell deformability, and cell-to-substrate adhesion on tissue invasion efficiency. The high spatial and temporal resolution of our analysis demonstrates that the ability of cells to deform depends on the cell cycle phase, peaks immediately after mitosis, and is key to the invasion process. Increased pore penetration efficiency by cells in early G1 phase also coincided with their lower nuclear volume and higher cell deformability, compared with the later cell cycle stages. Furthermore, artificial decondensation of chromatin induced an increase in cell and nuclear deformability and improved pore penetration efficiency of cells in G1. Together, these results underline that along the cell cycle cells have different abilities to dynamically remodel their actin cytoskeleton and induce nuclear shape changes, which determines their pore penetration efficiency. Thus, our results support a mechanism in which cell proliferation and pore penetration are functionally linked to favor the interstitial dissemination of metastatic cells.