Optogenetic stimulation of Lbc GEF-mediated Rho activity dynamics promotes cell invasion.

Cancer cell invasion relies on dynamic cell shape changes, which originate from protrusive and contractile intracellular forces. Previous studies revealed that contractile forces are controlled by positive-feedback amplification of the contraction regulator Rho by Lbc GEFs. These GEFs were previously linked to tumor progression; however, the underlying mechanisms are poorly understood. Here, we generated a mouse melanoma model in which cytosolic levels of the Lbc GEF GEF-H1 are controlled by light. Using this model, we found that increased GEF-H1 levels strongly stimulate cell contraction dynamics. Interestingly, increased contraction dynamics rapidly induced expansion of tumor spheroids via a focal adhesion kinase-dependent mechanism. Furthermore, long-term stimulation led to the escape of individual cells from spheroids. These findings reveal new insights into the oncogenic roles of Lbc GEFs and how they might promote tumor cell invasion. We propose a mechanism in which increased cell contraction dynamics result in asymmetric pulling forces at the tumor border, promoting the detachment and escape of individual cells.