The Caenorhabditis elegans homolog of the Evi1 proto-oncogene, egl-43, coordinates G1 cell cycle arrest with pro-invasive gene expression during anchor cell invasion

Cell invasion allows cells to migrate across compartment boundaries formed by basement membranes. Aberrant cell invasion is a first step during the formation of metastases by malignant cancer cells. Anchor cell (AC) invasion in C. elegans is an excellent in vivo model to study the regulation of cell invasion during development. Here, we have examined the function of egl-43, the homolog of the human Evi1 proto-oncogene (also called MECOM), in the invading AC. egl-43 plays a dual role in this process, firstly by imposing a G1 cell cycle arrest to prevent AC proliferation, and secondly, by activating pro-invasive gene expression. We have identified the AP-1 transcription factor fos-1 and the Notch homolog lin-12 as critical egl-43 targets. A positive feedback loop between fos-1 and egl-43 induces pro-invasive gene expression in the AC, while repression of lin-12 Notch expression by egl-43 ensures the G1 cell cycle arrest necessary for invasion. Reducing lin-12 levels in egl-43 depleted animals restored the G1 arrest, while hyperactivation of lin-12 signaling in the differentiated AC was sufficient to induce proliferation. Taken together, our data have identified egl-43 Evi1 as an important factor coordinating cell invasion with cell cycle arrest.