The purpose of this collaborative project is to establish a molecular definition of the dormant state of a cancer cell. In doing this, we hope to understand how this dormancy is broken, ultimately leading to recurrence in a patient that was stably in remission. Once our understanding of this is more complete, it is hoped that we can devise strategies for secondary prevention. This funding year we have pursued an alternative strategy for the identification of dormant tumor cells and the characterization of their microenvironment Imaging mass cytometry or IMC. Over the past year, we have constructed two antibody panels, which can be read by IMC, one to identify and characterize the status of breast tumor cells and one to characterize immune infiltrates. We plan to apply this approach as an adjunct to STPT, LCM, and RNAseq. We have also aimed to identify candidate dormancy regulators and find ways to manipulate these for patient benefit. Additionally, we have identified asparagine bioavailability as a major regulator of EMT, which could be manipulated to influence response to therapy, affecting the potential pool of residualdormant disease, and its recognition by the innate and adaptive immune system.