453 MMP Inhibition and Downregulation by Bisphosphonates OLLI TERONEN, a,e,h PIA HEIKKILÄ, d YRJÖ T. KONTTINEN, c,e MINNA LAITINEN, g TUULA SALO, f ROELAND HANEMAAIJER, i ANNELI TERONEN, d PÄIVI MAISI, e AND TIMO SORSA b Department of Oral and Maxillofacial Surgery, a Periodontology, b and Anatomy, c Institute of Dentistry, d and Helsinki University Central Hospital, e University of Helsinki, Helsinki, Finland f Department of Oral Pathology, Institute of Dentistry, University of Oulu, Oulu, Finland g Institute of Medical Technology, Surgery, University of Tampere, Tampere, Finland e Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland i Gaubius Laboratory, TNO-PG, PO Box 2215, 2301 CE Leiden, the Netherlands ABSTRACT: Bisphosphonates are a group of drugs capable of inhibiting bone resorption, and are thus used for the treatment of bone diseases, such as Paget’s disease, osteoporosis, and for bone metastases of malignant tumors. Their primary cellular target is considered to be the osteoclast. The molecular mechanisms responsible for the downregulation of bone resorption by bispho- sphonates have remain unclear. We have discovered that various matrix met- alloproteinases (MMPs) are inhibited in vitro by several bisphosphonates. This novel finding may, in part, explain the efficacy of bisphosphonates in their cur- rent indications in humans. In enzyme activity tests using purified and recom- binant enzymes, we have observed the inhibition of MMP-1, -2, -3, -7, -8, -9, -12, -13, and -14 by clondronate, alendronate, pamidronate, zolendronate, nedrinate, and clodrinate. The IC 50 s range from 50 to 150 M. We have also shown that clodronate can downregulate the expression of MT1-MMP protein and mRNA in several cell lines. Additionally, several bisphosphonates de- crease the degree of invasion of malignant melanoma (C8161) and fibrosarco- ma (HT1080) cells through artificial basement membrane (Matrigel) in cell cultures at IC 50 s of 50–150 M and below. Having low toxicity and proven to be well tolerated after several years in human use, bisphosphonates have the potential to become one of the main MMP-inhibitors for MMP-related human soft and hard tissue–destructive diseases in the near future. It has been clear for some time that inhibition of MMPs by pharmacologic agents in certain pathologic conditions would be beneficial to downregulate the tissue- destructive course in certain inflammatory and malignant diseases. Therefore the de- velopment of new MMP inhibitors to drugs it is hoped will be useful in the future is of great interest. Although the therapeutic utility of a collagenase/MMP inhibitor had already been recognized briefly after the initial discovery of vertebrate-type col- h Address for correspondence: Dr. Olli Teronen, Department of Oral and Maxillofacial Surgery, Institute of Dentistry, P.O. Box 41, FIN-00014 University of Helsinki, Finland. Phone, (358)-9-191 27 257; fax, (358)-9-191 27 265; e-mail, olli.teronen@helsinki.fi