Beside the digestion of the extracellular matrix during tumor invasion and 
metastasis, more recently, new functions for matrix metalloproteinases (MMPs) 
have been proposed. We studied the expression and function of these enzymes in 
pituitary cells. We observed the activities of MMP-2 and MMP-9 together with 
expression of membrane-type MMP and tissue inhibitor of metalloproteinase-1 in 
all types of human pituitary adenomas. We found surprisingly high levels of MMP 
activity and low levels of tissue inhibitor of metalloproteinases, indicating a 
high level of extracellular matrix-degrading activity in pituitary adenomas. To 
examine the function of metalloproteinase activity in pituitary cells we used 
the synthetic MMP inhibitor batimastat. These studies demonstrate that MMPs 
secreted by pituitary cells can release growth factors anchored to the 
extracellular matrix that, in turn, control pituitary cell proliferation and 
hormone secretion. These results define a new additional mechanism for the 
control of pituitary hormone secretion and indicate new potential therapeutic 
targets for pituitary adenomas.