[Roles of serine proteases and matrix metalloproteinases in tumor invasion and angiogenesis]

Abstract

The remodelling of extracellular matrix and angiogenesis represent two essential processes for tumor growth and metastatic dissemination. These phenomena imply many interactions between tumor cells and host cells via action of various proteases including metalloproteinases (MMPs) whose activity is controlled by TIMPs and serine proteases (tissue type Plasminogen Activator (tPA), urokinase type Plasminogen Activator (uPA) and plasmin) inhibited in particular by PAI-1 (Plasminogen Activator Inhibitor- 1). Evolution of tumors depends on the joint action of these enzymes, as well as precise balance between these proteases and their physiological inhibitors. Proteases regulate the fate and activity of many proteins by controlling appropriate intra- or extracellular localization; shedding from cell surfaces ; activation or inactivation of proteases and other enzymes, cytokines, hormones or growth factors and exposure of cryptic neoproteins. Hence, proteases initiate, modulate and terminate a wide range of important cellular functions by processing bioactive molecules an thereby control essential biological processes, such as DNA replication, cell-cycle progression, cell proliferation, differentiation and migration, morphogenesis and tissue remodelling, neuronal outgrowth, haemostasis, wound healing, immunity, angiogenesis and apoptosis. Work completed has for objective to elucidate the specific part played by serine proteases and MMPS produced by the host cells in the processes of tumor growth and angiogenesis. By using an original model of transplantation of malignant murine keratinocytes (PDVA cell line) into deficient mice (-/-) and wild type mice (+/+), we showed the essential proteolytic role of PAI-1 produced by host cells in the tumor progression and angiogenesis. This mechanism of PAI-1 action was confirmed by using the model in vitro aorta rings. By using deficient mice for one or two MMPs combined (MMP-2, MMP-3, MMP-9, MMP-11, MMP-2&9, MMP3&9), we demonstrated that only the combined deficiency of MMP-2 and -9 showed an absence of tumor invasion and angiogenesis. These data suggest the existence of compensatory mechanisms of a MMP by another MMP or another proteolytic way. These phenomena of redundancy are to be known and detailed to elaborate in a near future, the development of specific inhibitors of MMPS.