What role do MMPs play during the metastatic cascade?

a. They stimulate the growth of tumor cells, by stimulating M phase progression.
b. They recruit blood vessels to tumors, thereby stimulating the multiplication of multiple phenotypes.
c. They bind to specific mineral ions and then digest extracellular matrix proteins, thereby allowing tumor cells to migrate towards blood vessels.
d. They are matrix proton pumps that enhance H+ pumping, thereby allowing for faster ATP synthesis and faster cell growth.