Tissue inhibitors of metalloproteinases (TIMPs) are well known as inhibitors of matrix metalloproteinases (MMPs) such as interstitial collagenase, gelatinase A and B, and stromelysin 1, and have been suggested to play an important role in the regulation of MMPs. Although MMP inhibition is the primary action of the TIMPs, these inhibitors also have cell growth-stimulating activity that seems to be independent of their MMP inhibitory activity (1 –10 ). The purpose of this chapter is to introduce three methods for assaying the growth factor activity of TIMPs, that is, the direct counting of cell number, the measurement of DNA content for cell proliferation, and the [3 H]thymidine incorporation assay for cell mitogen activity.
