Oncogenic PIK3CA enhances collective migration of mammary epithelial cells through ERK wave propagation

Oncogenic mutations of the PIK3CA gene, which encodes the catalytic subunit of the phosphatidylinositol 3-kinase (PI3K) enhance cell migration via ERK (ERK1 and ERK2, also known as MAPK3 and MAPK1, respectively) activation. We analyzed the factors regulating collective cell migration (CCM) of genome-edited MCF10A cell lines carrying hotspot PIK3CA mutations E545K or H1047R. H1047R enhanced CCM and promoted the propagation of waves of ERK activity backwards from the wound edge, whereas E545K impaired both coordinated CCM and ERK activity wave formation. The distance traveled by ERK activity waves correlated with directional persistence of migrating cells. Inhibition of cell contractility stimulated ERK wave propagation and efficient CCM of E545K cells but impaired ERK waves and CCM in control cells. Impaired ERK wave propagation was consistently associated with non-linear cell-cell junctions and the loss of polarized distribution of actomyosin. Taken together, these analyses suggest that polarized actomyosin contractility and pulsatile ERK activation must be constrained in the territory of a phase diagram compatible with mechanotransduction of ERK waves across cell-cell junctions to achieve highly coordinated and efficient collective migration.