3d-analysis-of-multi-cellular-responses-to-chemoattractant-gradients

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and ...

Yale University

The root cause of cancer mortality and morbidity is the metastatic spread of the primary tumor, but underlying mechanisms remain elusive. Here we investigate biomechanical interactions that may accompany invasive spread of melanoma cells. We find that metastatic cells can exert considerable traction forces and modify local collagen organization within a 3D matrix. When this re-organization is mimicked using a nano-fabricated model of aligned extracellular matrix fibers, metastatic cells, including less invasive melanoma cells, were in turn induced to align, elongate and migrate, guided by the local ridge orientations. Strikingly, we found that this aligned migration of melanoma cells was accompanied by long-range regulation of cytoskeletal remodeling that show anisotropic stiffening in the direction of fiber orientation suggestive of a positive feedback between ECM fiber alignment and forces exerted by cancer cells. Taken together, our findings suggest that the invasive spread of cancer cells can be defined by complex interplay with the surrounding matrix, during which they both modify the matrix and use the matrix alignment as a persistent migration cue, leading to more extensive and rapid invasive spread.

Biomechanical interplay between anisotropic re-organization of cells and the surrounding matrix underlies transition to invasive cancer spread.

Epigenetic control of regulatory networks is only partially understood. Expression of Insulin-like growth factor-II (IGF2) is controlled by genomic imprinting, mediated by silencing of the maternal allele. Loss of imprinting of IGF2 (LOI) is linked to intestinal and colorectal cancers, causally in murine models and epidemiologically in humans. However, the molecular underpinnings of the LOI phenotype are not clear. Surprisingly, in LOI cells, we find a reversal of the relative activities of two canonical signaling pathways triggered by IGF2, causing further rebalancing between pro- and anti-apoptotic signaling. A predictive mathematical model shows that this network rebalancing quantitatively accounts for the effect of receptor tyrosine kinase inhibition in both WT and LOI cells. This mechanism also quantitatively explains both the stable LOI phenotype and the therapeutic window for selective killing of LOI cells, and thus prevention of epigenetically controlled cancers. These findings suggest a framework for understanding epigenetically modified cell signaling.

A Loss of Epigenetic Control Can Promote Cell Death through Reversing the Balance of Pathways in a Signaling Network.

Bacterial biofilms represent an important medical problem; however, the mechanisms of the onset of biofilm formation are poorly understood. Here, using new controlled methods allowing high-throughput and reproducible biofilm growth, we show that biofilm formation is linked to self-imposed mechanical stress. In growing uropathogenic Escherichia coli colonies, we report that mechanical stress can initially emerge from the physical stress accompanying colony confinement within micro-cavities or hydrogel environments reminiscent of the cytosol of host cells. Biofilm formation can then be enhanced by a nutrient access-modulated feedback loop, in which biofilm matrix deposition can be particularly high in areas of increased mechanical and biological stress, with the deposited matrix further enhancing the stress levels. This feedback regulation can lead to adaptive and diverse biofilm formation guided by the environmental stresses. Our results suggest previously unappreciated mechanisms of the onset and progression of biofilm growth.

Article	Year
Biomechanical interplay between anisotropic re-organization of cells and the surrounding matrix underlies transition to invasive cancer spread. Scientific reports\| PubMed ID: 30242256	2018
A Loss of Epigenetic Control Can Promote Cell Death through Reversing the Balance of Pathways in a Signaling Network. Molecular cell\| PubMed ID: 30244832	2018
Self-induced mechanical stress can trigger biofilm formation in uropathogenic Escherichia coli. Nature communications\| PubMed ID: 30291231	2018

Andre Levchenko

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