Two distinct integrin binding sites on MMP9 drive cancer invasion by mediating integrin membrane trafficking & stabilization

Matrix stiffening has been established to drive cancer progression through increased activity of matrix metalloproteases (MMPs) which degrade the matrix creating paths for migration. However, the non-proteolytic functions of MMPs in cancer invasion remain relatively less understood. Here we have probed the importance of proteolytic and non-proteolytic functions of MMP9, which exhibits robust stiffness dependent expression and secretion in highly invasive cancer cells. We show that while MMP9 sustains spreading and 2D migration non-proteolytically by stabilizing focal adhesions, MMP9 proteolytic activity is essential for 3D invasion. We then establish the function of two distinct integrin β1 (ITG β1) binding sites on MMP9, with the hemopexin domain mediating co-packaging and co-transport of ITG β1/MMP9 to the cell periphery, and the RGD domain stabilizing ITG β1 on the cell membrane prior to matrix degradation. Together, our results illustrate how MMP9 optimizes cancer invasion by spatiotemporally integrating matrix remodeling with adhesion formation.