Oncogenic Ras/ERK signalling alters cell shape and mechanics to facilitate cell division under confinement


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Helen Matthews1,Sushila Ganguli1,Katarzyna Plak1,Anna Taubenberger2,Jochen Guck2,Buzz Baum1
1University College London,2TU Dresden

Abstract

Background

Tumours are stiffer than healthy tissue, due to high cell density and extra-cellular matrix deposition. Cancer cells, unlike normal cells, continue to divide in this mechanically-altered micro-environment. We asked how the genetic changes in cancer cells alter the cell division process to allow cells to respond to mechanical constraints.

Method

To study the effect of oncogene activation on cell division, we used an inducible system to activate RasV12 in normal epithelial cells. We imaged dividing cells using time-lapse microscopy and quantified mitotic cell shape. We also measured cell mechanics in interphase and mitosis using atomic force microscopy. We then challenged cells with and without RasV12 to divide in conditions of physical confinement under stiff hydrogels.

Results

We found that activation of RasV12, for as little as five hours, dramatically altered mitotic cell shape by increasing acto-myosin contractility, in a manner dependent on the downstream MEK/ERK signalling cascade. The same effect was observed following long term RasV12 activation.The Ras/ERK pathway also altered cell mechanical properties, so that Ras-activated cells were softer in interphase but stiffened more in mitosis. These mechanical changes allowed cells to exert more force to round up and divide when confined underneath stiff hydrogels. Conversely, inhibition of the Ras/ERK pathway prevented mitotic rounding in confinement, resulting in multiple mitotic defects including spindle fracturing and chromosome loss.

Conclusion

Activation of the oncogenic Ras/ERK signalling pathway promotes cell rounding and stiffening in mitosis, enabling cells to divide in confined conditions where normal cells fail. This could provide an advantage for cell division in mechanically stiff environments like tumours.