Our proposal “The role of matrix metalloproteinases in breast cancer progression” was selected for funding by the American Cancer Society (ACS) with a prestigious ACS Research Scholar Grant. Starting Spring 2019, this project will be funded for 4 years with $165,000 direct costs per year. This proposal will zoom in on one of the key regulators of the tumor microenvironment called matrix metalloproteinases (MMPs), which are secreted proteolytic enzymes that affect multiple aspects of cancer including extracellular matrix remodeling, inflammation, and metastasis. Here, we are dissecting the molecular mechanisms underlying the role of MMPs in the regulation of tumor progression using a combination of cutting-edge cellular and molecular biology and single cell genomics studies in primary human tumor samples as well as accurate mouse models for breast cancer. These studies may unravel new molecular mechanisms through which the microenvironment promotes cancer progression and metastasis and may ultimately form the rationale to revisit MMPs as drug targets in breast cancer. We thank the ACS for their generous support!