Abstract 3826: Awakened dormant cancer cells undergo highly mesenchymal to quasi-mesenchymal transition and acquire stemness

The awakening of dormant disseminated cancer cells is likely responsible for the clinical relapses of patients whose primary tumors have been successfully cured months and even years earlier. In the present study, we demonstrate that dormant breast cancer cells lodged in the lungs reside in a highly mesenchymal, non-proliferative phenotypic state. The awakening of these cells is not triggered by a cancer cell-autonomous process. Instead, inflammation of the surrounding tissue microenvironment causes them to shift from a highly mesenchymal to a quasi-mesenchymal phenotypic state in which they acquire stemness and proliferative ability. Once awakened, these cells can stably reside in this quasi-mesenchymal state and maintain their stemness, doing so without ongoing heterotypic signaling from the lung microenvironment. EGFR ligands released by the cells of the injured tissue microenvironment, including notably M2 type macrophages, promote dormant cancer cells to move toward this quasi-mesenchymal state, a transition that is critical for the awakening process. An understanding of the mechanisms of metastatic awakening may lead in the future to treatment strategies designed to prevent such awakening and resulting metastatic relapse.