[Show abstract][Hide abstract] ABSTRACT: Objectives The aim of the study was to evaluate the efficacy of different dosages of estetrol (E4) combined with one of two progestins in suppressing the pituitary–ovarian axis and ovulation in healthy premenopausal women. Methods This was an open, parallel, phase II, dose-finding, pilot study performed in healthy women aged 18 to 35 years with a documented ovulatory cycle before treatment. For three consecutive cycles in a 24/4-day regimen, participants received 5 mg or 10 mg E4/3 mg drospirenone (DRSP); 5 mg, 10 mg or 20 mg E4/150 μg levonorgestrel; or 20 μg ethinylestradiol (EE)/3 mg DRSP as comparator. Pituitary–ovarian axis activity and the occurrence of ovulation were evaluated by monitoring follicular size, serum levels of follicle-stimulating hormone, luteinising hormone, estradiol and progesterone during treatment cycles 1 and 3. Endometrial thickness was evaluated throughout the trial, and the return of ovulation was evaluated after the last intake of medication. Results A total of 109 women were included in the trial. No ovulation occurred in any treatment group. Ovarian activity inhibition seemed proportional to the E4 dosage: the highest suppression was observed in the 20 mg E4 group and was very similar to that observed with EE/DRSP. Endometrial thickness was suppressed to the same extent in all groups. Post-treatment ovulation occurred in all participants between 17 and 21 days after the last active treatment. The study combinations were well tolerated and safe. Conclusions Combined with a progestin, E4 adequately suppresses ovarian activity, particularly when given at a dosage above 10 mg/day.
Full-text · Article · Aug 2015 · The European Journal of Contraception and Reproductive Health Care
[Show abstract][Hide abstract] ABSTRACT: Objectives Estetrol (E4) is a natural estrogen produced by the human fetal liver. In combination with drospirenone (DRSP) or levonorgestrel (LNG), E4 blocks ovulation and has less effect on haemostatic biomarkers in comparison with ethinylestradiol (EE) combined with DRSP. This study evaluates the impact of several doses of E4/DRSP and E4/LNG on safety parameters such as liver function, lipid metabolism, bone markers and growth endocrine parameters. Methods This was a dose-finding, single-centre, controlled study performed in healthy women aged 18 to 35 years with a documented pretreatment ovulatory cycle. Participants received 5 mg or 10 mg E4/3 mg DRSP; 5 mg, 10 mg or 20 mg E4/150 μg LNG; or 20 μg EE/3 mg DRSP as a comparator for three consecutive cycles in a 24/4-day regimen. Changes from baseline to end of treatment in liver parameters, lipid metabolism, bone markers and growth endocrinology were evaluated. Results A total of 109 women were included in the study. Carrier proteins were minimally affected in the E4/DRSP and E4/LNG groups, in comparison with the EE/DRSP group, where a significant increase in sex hormone-binding globulin was observed. Similarly, minor effects on lipoproteins were observed in the E4 groups, and the effects on triglycerides elicited by the E4 groups were significantly lower than those in the EE/DRSP group. No imbalances in bone markers were observed in any groups. No alterations in insulin-like growth factor were observed in the E4 groups. Conclusions E4-containing combinations have a limited effect on liver function, lipid metabolism, and bone and growth endocrine parameters.
No preview · Article · Jul 2015 · The European Journal of Contraception and Reproductive Health Care
[Show abstract][Hide abstract] ABSTRACT: Human papillomavirus (HPV) infection, particularly type 16, is causally associated with cancer of the uterine cervix which mainly develops at the squamocolumnar (SC) junction. The progression of cervical HPV infections into (pre)neoplastic lesions suggests that viral antigens are not adequately recognized by the innate immunity or presented to the adaptive immune system. Members of the defensin family have been recently found to inhibit viral and bacterial pathogens, to stimulate the migration of immune cells and to play a role in anticancer responses. In the present study, we focused on the poorly characterized human alpha-defensin 5 (HD-5) and its possible role in these processes. We showed that HD-5 was able to prevent HPV virion entry into cervical keratinocytes and to influence the adaptive immunity. Indeed, this peptide specifically induced the chemoattraction and the proliferation of both activated T lymphocytes and immature dendritic cells in a CCR2/CCR6-dependent manner and stimulated the infiltration of these professional antigen-presenting cells in a (pre)neoplastic epithelium transplanted in vivo in immunodeficient mice. No chemotactic effect was observed with plasmacytoid dendritic cells, macrophages or natural killer cells. Proliferative and angiogenic effects of HD-5 were also assessed in vitro and in vivo. However there was a striking regional disparity in expression of HD-5, being prominent in ectocervical, vaginal and vulvar neoplasia while absent or nearly so in the cervical SC junction. Taken together, these results suggest one possible explanation for why the SC junction is uniquely vulnerable to both high risk HPV infection - via reduced HD-5 expression and viral entry - and progression of neoplasia, via altered cell mediated immune responses and altered microenvironment.
No preview · Article · Dec 2014 · The Journal of Pathology
[Show abstract][Hide abstract] ABSTRACT: Introduction and hypothesis:
The pathophysiology of pelvic organ prolapse (POP) is incompletely understood. The purpose of this study is to describe the current knowledge about histology of the vaginal wall and its possible involvement in the pathogenesis of pelvic organ prolapse.
Eligible studies were selected through a MEDLINE search covering January 1986 to December 2012. The research was limited to English-language publications.
Investigations of changes in the vaginal tissue that occur in women with genital prolapse are currently still limited and produced contrary results. The heterogeneity of the patients and the control groups in terms of age, parity and hormonal status, of the localization of biopsies and the histological methods as well as the lack of validation of the quantification procedures do not allow clear and definitive conclusions to be drawn.
This review shows that current knowledge of the histological changes observed in women with POP are inconclusive and relatively limited. More studies are needed in this specific field to better understand the mechanisms that lead to POP.
No preview · Article · May 2013 · International Urogynecology Journal
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To evaluate the antilymphangiogenic potential of multi-target tyrosine kinase inhibitor sunitinib in corneal neovascularization (NV).
Inflammatory corneal NV was induced by thermal cauterization applied in the central cornea of mice, to which sunitinib malate was daily administered by gavage or not. At days 6, 11, or 17 post cauterization, lymphatic and blood vessels, as well as inflammatory cells were immunostained and quantified in whole-mounted corneas. RT-PCRs were performed to evidence VEGF-A, VEGF-C, VEGF-D, placental growth factor (PlGF), and soluble vascular endothelial growth factor receptor (VEGFR)-1 and -2 (sVEGFR-1, sVEGFR-2) expressions. Macrophages were isolated from mice peritoneal cavity following thioglycollate injection to produce conditioned medium. The effects of sunitinib were evaluated in vitro in the aortic and lymphatic ring assays in the presence or not of macrophage conditioned medium.
Sunitinib treatment drastically reduced pathologic corneal lymphangiogenesis and angiogenesis. Reduced F4/80+ cell infiltration was evidenced in sunitinib-treated mice and was associated to decreased VEGF-A (by 50%, P < 0.01) and VEGF-C (by 35%, P < 0.01) expressions, while VEGF-D and sVEGFR-2 expressions were not affected. In vitro, sunitinib dose-dependently inhibited aortic ring outgrowth, but failed to affect lymphangiogenesis in the lymphatic ring assay. However, macrophage conditioned medium-enhanced angiogenesis and lymphangiogenesis were both strongly counteracted by sunitinib treatment. Mechanistically, sunitinib blocked VEGFR-2 phosphorylation induced by VEGF-A released by macrophages.
Sunitinib exerts antihemangiogenic and antilymphangiogenic effects in vivo by reducing F4/80+ cell recruitment and interacting with their released factors.
[Show abstract][Hide abstract] ABSTRACT: Lymphatic dysfunctions are associated with several human diseases, including lymphedema and metastatic spread of cancer. Although it is well recognized that lymphatic capillaries attach directly to interstitial matrix mainly composed of fibrillar type I collagen, the interactions occurring between lymphatics and their surrounding matrix have been overlooked. In this study, we demonstrate how matrix metalloproteinase (MMP)-2 drives lymphatic morphogenesis through Mmp2-gene ablation in mice, mmp2 knockdown in zebrafish and in 3D-culture systems, and through MMP2 inhibition. In all models used in vivo (3 murine models and thoracic duct development in zebrafish) and in vitro (lymphatic ring and spheroid assays), MMP2 blockage or down-regulation leads to reduced lymphangiogenesis or altered vessel branching. Our data show that lymphatic endothelial cell (LEC) migration through collagen fibers is affected by physical matrix constraints (matrix composition, density, and cross-linking). Transmission electron microscopy and confocal reflection microscopy using DQ-collagen highlight the contribution of MMP2 to mesenchymal-like migration of LECs associated with collagen fiber remodeling. Our findings provide new mechanistic insight into how LECs negotiate an interstitial type I collagen barrier and reveal an unexpected MMP2-driven collagenolytic pathway for lymphatic vessel formation and morphogenesis.
[Show abstract][Hide abstract] ABSTRACT: This chapter contains sections titled: IntroductionThe different steps of angio- and lymphangiogenesisCulturing isolated (lymphatic and blood) endothelial cellsLymphatic and blood endothelial cell discriminationIn vitro dedifferentiationSuitability of LEC monoculturesThe ‘ring assays’Concluding remarksAcknowledgementsReferences
[Show abstract][Hide abstract] ABSTRACT: The 16-kDa angiostatic N-terminal fragment of human prolactin (16K hPRL) has been reported to be a new potent anticancer compound. This protein has already proven its efficiency in several mouse tumor models in which it prevented tumor-induced angiogenesis and delayed tumor growth. In addition to angiogenesis, tumors also stimulate the formation of lymphatic vessels, which contribute to tumor cell dissemination and metastasis. However, the role of 16K hPRL in tumor-induced lymphangiogenesis has never been investigated. We establish in vitro that 16K hPRL induces apoptosis and inhibits proliferation, migration, and tube formation of human dermal lymphatic microvascular endothelial cells. In addition, in a B16F10 melanoma mouse model, we found a decreased number of lymphatic vessels in the primary tumor and in the sentinel lymph nodes after 16K hPRL treatment. This decrease is accompanied by a significant diminished expression of lymphangiogenic markers in primary tumors and sentinel lymph nodes as determined by quantitative RT-PCR. These results suggest, for the first time, that 16K hPRL is a lymphangiostatic as well as an angiostatic agent with antitumor properties.
[Show abstract][Hide abstract] ABSTRACT: Abnormal lymphatic vessel formation (lymphangiogenesis) is associated with different pathologies such as cancer, lymphedema, psoriasis and graft rejection. Lymphatic vasculature displays distinctive features than blood vasculature, and mechanisms underlying the formation of new lymphatic vessels during physiological and pathological processes are still poorly documented. Most studies on lymphatic vessel formation are focused on organism development rather than lymphangiogenic events occurring in adults. We have here studied lymphatic vessel formation in two in vivo models of pathological lymphangiogenesis (corneal assay and lymphangioma). These data have been confronted to those generated in the recently set up in vitro model of lymphatic ring assay. Ultrastructural analyses through Transmission Electron Microscopy (TEM) were performed to investigate tube morphogenesis, an important differentiating process observed during endothelial cell organization into capillary structures.
In both in vivo models (lymphangiogenic corneal assay and lymphangioma), migrating lymphatic endothelial cells extended long processes exploring the neighboring environment and organized into cord-like structures. Signs of intense extracellular matrix remodeling were observed extracellularly and inside cytoplasmic vacuoles. The formation of intercellular spaces between endothelial cells led to tube formation. Proliferating lymphatic endothelial cells were detected both at the tips of sprouting capillaries and inside extending sprouts. The different steps of lymphangiogenesis observed in vivo are fully recapitulated in vitro, in the lymphatic ring assay and include: (1) endothelial cell alignment in cord like structure, (2) intracellular vacuole formation and (3) matrix degradation.
In this study, we are providing evidence for lymphatic vessel formation through tunneling relying on extensive matrix remodeling, migration and alignment of sprouting endothelial cells into tubular structures. In addition, our data emphasize the suitability of the lymphatic ring assay to unravel mechanisms underlying lymphangiogenesis.
[Show abstract][Hide abstract] ABSTRACT: Angiogenesis, extracellular matrix remodeling and cell migration are associated with cancer progression and involve at least, the plasminogen activating system and its main physiological inhibitor, the plasminogen activator inhibitor-1 (PAI-1). Considering the recognized importance of PAI-1 in the regulation of tumor angiogenesis and invasion in murine models of skin tumor transplantation, we explored the functional significance of PAI-1 during early stages of neoplastic progression in the transgenic mouse model of multistage epithelial carcinogenesis (K14-HPV16 mice). We have studied the effect of genetic deletion of PAI-1 on inflammation, angiogenesis, lymphangiogenesis and tumor progression. In this model, PAI-1 deficiency neither impaired keratinocyte hyperproliferation or tumor development nor affected the infiltration of inflammatory cells and development of angiogenic or lymphangiogenic vasculature. We are reporting evidence for concomitant lymphangiogenic and angiogenic switches independent to PAI-1 status. Taken together, these data indicate that PAI-1 is not rate limiting for neoplastic progression and vascularization during premalignant progression, or that there is a functional redundancy between PAI-1 and other tumor regulators, masking the effect of PAI-1 deficiency in this long-term model of multistage epithelial carcinogenesis.
Full-text · Article · Jan 2011 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to explore the function of plasminogen activator inhibitor-1 (PAI-1) during pathological lymphangiogenesis. PAI-1, the main physiological inhibitor of plasminogen activators is involved in pathological angiogenesis at least by controlling extracellular proteolysis and by regulating endothelial cell survival and migration. Protease system's role in lymphangiogenesis is unknown yet. Thus, based on its important pro-angiogenic effect, we hypothesized that PAI-1 may regulate lymphangiogenesis associated at least with metastatic dissemination of cancer cells. To address this issue, we studied the impact of PAI-1 deficiency in various murine models of tumoral lymphangiogenesis. Wild-type PAI-1 proficient mice were used as controls. We provide for the first time evidence that PAI-1 is dispensable for tumoral lymphangiogenesis associated with breast cancers either induced by mammary carcinoma cell injection or spontaneously appearing in transgenic mice expressing the polyomavirus middle T antigen (PymT) under the control of a mouse mammary tumor virus long-terminal repeat promoter (MMTV-LTR). We also investigated inflammation-related lymphatic vessel recruitment by using two inflammatory models. PAI-1 deficiency did neither affect the development of lymphangioma nor burn-induced corneal lymphangiogenesis. These novel data suggest that vascular remodelling associated with lymphangiogenesis and angiogenesis involve different molecular determinants. PAI-1 does not appear as a potential therapeutic target to counteract pathological lymphangiogenesis.
[Show abstract][Hide abstract] ABSTRACT: ADAMTS (a disintegrin and metalloproteinase domain with thrombospondin motifs) constitute a family of endopeptidases related to matrix metalloproteinases. These proteases have been largely implicated in tissue remodeling and angiogenesis associated with physiological and pathological processes. To elucidate the in vivo functions of ADAMTS-12, we have generated a knockout mouse strain (Adamts12(-/-)) in which Adamts12 gene was deleted. The mutant mice had normal gestations and no apparent defects in growth, life span and fertility. By applying three different in vivo models of angiogenesis (malignant keratinocyte transplantation, Matrigel plug and aortic ring assays) to Adamts12(-/-) mice, we provide evidence for a protective effect of this host enzyme toward angiogenesis and cancer progression. In the absence of Adamts-12, both the angiogenic response and tumor invasion into host tissue were increased. Complementing results were obtained by using medium conditioned by cells overexpressing human ADAMTS-12, which inhibited vessel outgrowth in the aortic ring assay. This angioinhibitory effect of ADAMTS-12 was independent of its enzymatic activity as a mutated inactive form of the enzyme was similarly efficient in inhibiting endothelial cell sprouting in the aortic ring assay than the wild-type form. Altogether, our results show that ADAMTS-12 displays antiangiogenic properties and protect the host toward tumor progression.
[Show abstract][Hide abstract] ABSTRACT: Plasminogen activator inhibitor-1 (PAI-1) paradoxically enhances tumor progression and angiogenesis; however, the mechanism supporting this role is not known. Here we provide evidence that PAI-1 is essential to protect endothelial cells (ECs) from FasL-mediated apoptosis. In the absence of host-derived PAI-1, human neuroblastoma cells implanted in PAI-1-deficient mice form smaller and poorly vascularized tumors containing an increased number of apoptotic ECs. We observed that knockdown of PAI-1 in ECs enhances cell-associated plasmin activity and increases spontaneous apoptosis in vitro. We further demonstrate that plasmin cleaves FasL at Arg144-Lys145, releasing a soluble proapoptotic FasL fragment from the surface of ECs. The data provide a mechanism explaining the proangiogenic activity of PAI-1.
[Show abstract][Hide abstract] ABSTRACT: An adequate balance between serine proteases and their plasminogen activator inhibitor-1 (PAI-1) is critical for pathological angiogenesis. PAI-1 deficiency in mice is associated with impaired choroidal neovascularization (CNV) and tumoral angiogenesis. In the present work, we demonstrate unexpected differences in the contribution of bone marrow (BM)-derived cells in these two processes regulated by PAI-1. PAI-1(-/-) mice grafted with BM-derived from wild-type mice were able to support laser-induced CNV formation but not skin carcinoma vascularization. Engraftment of irradiated wild-type mice with PAI-1(-/-) BM prevented CNV formation, demonstrating the crucial role of PAI-1 delivered by BM-derived cells. In contrast, the transient infiltration of tumor transplants by local PAI-1-producing host cells rather than by BM cells was sufficient to rescue tumor growth and angiogenesis in PAI-1-deficient mice. These data identify PAI-1 as a molecular determinant of a local permissive soil for tumor angiogenesis. Altogether, the present study demonstrates that different cellular mechanisms contribute to PAI-1-regulated tumoral and CNV. PAI-1 contributes to BM-dependent choroidal vascularization and to BM-independent tumor growth and angiogenesis.
Full-text · Article · Nov 2007 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: In addition to their direct antimicrobial activity, defensins might also influence adaptive immunity by attracting immature dendritic cells (DC). As these cells have been shown to be deficient in uterine cervix carcinogenesis, we evaluated the ability of alpha-defensin (HNP-2, human neutrophil defensin 2) and beta-defensin (HbetaD2, human beta defensin 2) to stimulate their migration in human papillomavirus (HPV)-associated (pre)cancers. We first observed, using RT-PCR and immunohistology, that HbetaD2 is absent in HPV-transformed keratinocytes and that it is weakly expressed in cervical (pre)neoplastic lesions in comparison with normal keratinocytes. We next demonstrated that defensins exert a chemotactic activity for DC in a Boyden Chamber assay and stimulate their infiltration in an in vitro-formed (pre)neoplastic epithelium (organotypic culture of HPV-transformed keratinocytes). To evaluate the ability of defensins also to recruit DC in vivo, we developed a model of immunodeficient mice grafted with organotypic cultures of HPV+ keratinocytes, which form an epithelium similar to a high-grade neoplastic lesion, with tumoral invasion and neovascularization. Intravenously injected human DC were able to infiltrate grafts of HPV+ keratinocytes after administration of HNP-2 in the transplantation chamber. Taken together, these results suggest that defensins could reverse a frequent immune alteration observed in cancer development.
Full-text · Article · Oct 2007 · The FASEB Journal
[Show abstract][Hide abstract] ABSTRACT: The matrix metalloproteinases (MMPs) play a key role in normal and pathological angiogenesis by mediating extracellular matrix degradation and/or controlling the biological activity of growth factors, chemokines, and/or cytokines. Specific functions of individual MMPs as anti- or proangiogenic mediators remain to be elucidated. In the present study, we assessed the impact of single or combined MMP deficiencies in in vivo and in vitro models of angiogenesis (malignant keratinocyte transplantation and the aortic ring assay, respectively). MMP-9 was predominantly expressed by neutrophils in tumor transplants, whereas MMP-2 and MMP-3 were stromal. Neither the single deficiency of MMP-2, MMP-3, or MMP-9, nor the combined absence of MMP-9 and MMP-3 did impair tumor invasion and vascularization in vivo. However, there was a striking cooperative effect in double MMP-2:MMP-9-deficient mice as demonstrated by the absence of tumor vascularization and invasion. In contrast, the combined lack of MMP-2 and MMP-9 did not impair the in vitro capillary outgrowth from aortic rings. These results point to the importance of a cross talk between several host cells for the in vivo tumor promoting and angiogenic effects of MMP-2 and MMP-9. Our data demonstrate for the first time in an experimental model that MMP-2 and MMP-9 cooperate in promoting the in vivo invasive and angiogenic phenotype of malignant keratinocytes.
Full-text · Article · Mar 2005 · The FASEB Journal
[Show abstract][Hide abstract] ABSTRACT: Angiogenesis and tumor expansion are associated with extracellular matrix remodeling and involve various proteases such as the plasminogen (Plg)/plasminogen activator (PA) system. Recently, several experimental data have implicated the plasminogen activator inhibitor-1 (PAI-1) in tumor angiogenesis in murine systems. However, little is known about PAI-1 functions in human skin carcinoma progression. By generating immunodeficient mice (in Rag-1-/- or nude background) deleted for PAI-1 gene (PAI-1-/-), we have evaluated the impact of host PAI-1 deficiency on the tumorigenicity of two malignant human skin keratinocyte cell lines HaCaT II-4 and HaCaT A5-RT3 forming low-grade and high-grade carcinomas, respectively. When using the surface transplantation model, angiogenesis and tumor invasion of these two cell lines are strongly reduced in PAI-1-deficient mice as compared to the wild-type control animals. After subcutaneous injection in PAI-1-/- mice, the tumor incidence is reduced for HaCaT II-4 cells, but not for those formed by HaCaT A5-RT3 cells. These data indicate that PAI-1 produced by host cells is an important contributor to earlier stages of human skin carcinoma progression. It exerts its tumor-promoting effect in a tumor stage-dependent manner, but PAI-1 deficiency is not sufficient to prevent neoplastic growth of aggressive tumors of the human skin.
[Show abstract][Hide abstract] ABSTRACT: Because of the central role of dendritic cells and/or Langerhans cells(DC/LC) in the induction of cellular immune responses, pharmacological agents that modulate the recruitment of these cells might have a clinical interest. The present study was designed to evaluate the capacity of several pharmaceutical formulations to topically deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) on human papillomavirus (HPV)-associated genital (pre)neoplastic lesions. The formulations were evaluated for their bioactivity and for their potential to recruit DC in organotypic cultures of HPV-transformed keratinocytes. We found that a bioadhesive polycarbophil gel (Noveon) at pH 5.5 is able to maintain the bioactivity of GM-CSF at 4 or 37 degrees C for at least 7 days, whereas a decreased activity of GM-CSF was observed when the molecule is included in other polymer gels. GM-CSF incorporated in the polycarbophil gel was also a potent factor in enhancing the colonization of DC into organotypic cultures of HPV-transformed keratinocytes since the infiltration of DC in the in vitro-formed (pre)neoplastic epithelium was very low under basal conditions and dramatically increased in the presence of GM-CSF gel. We next demonstrated that GM-CSF incorporated in polycarbophil gel induces the recruitment of human DC in a human (pre)neoplastic epithelium grafted into NOD/SCID mice. The efficacy of GM-CSF in this formulation was equivalent to that observed with liquid GM-CSF. These results suggest that GM-CSF incorporated in polycarbophil gel could play an important role in the recruitment of DC/LC in mucosal surfaces and be useful as a new immunotherapeutic approach for genital HPV-associated (pre)neoplastic lesions.
Full-text · Article · Dec 2004 · Antimicrobial Agents and Chemotherapy
[Show abstract][Hide abstract] ABSTRACT: Plasminogen activator inhibitor type 1 (PAI-1) plays a key role in tumor progression and is believed to control proteolytic activity and cell migration during angiogenesis. We report here that host PAI-1, at physiological concentration, promotes in vivo tumor invasion and angiogenesis. In sharp contrast, inhibition of tumor vascularization was observed when PAI-1 was produced at supraphysiologic levels, either by host cells (transgenic mice overexpressing PAI-1) or by tumor cells (after transfection with murine PAI-1 cDNA). This study provides for the first time in vivo evidence for a dose-dependent effect of PAI-1 on tumor angiogenesis. Of great interest is the finding that PAI-1 produced by tumor cells, even at high concentration, did not overcome the absence of PAI-1 in the host, emphasizing the importance of the cellular source of PAI-1.
[Show abstract][Hide abstract] ABSTRACT: Cell surface proteolysis is an important mechanism for generating biologically active proteins that mediate a range of cellular functions and contribute to biological processes such as angiogenesis. Although most studies have focused on the plasminogen system and matrix metalloproteinases (MMPs), recently there has been an increase in the identification of membrane associated proteases, including serine proteases, ADAMs, and membrane-type MMPs (MT-MMPs). Normally, protease activity is tightly controlled by tissue inhibitors of MMPs (TIMPs) and plasminogen activator inhibitors (PAIs). The balance between active proteases and inhibitors is thought to determine the occurrence of proteolysis in vivo. High concentrations of proteolytic system components correlate with poor prognosis in many cancers. Paradoxically, high (not low) PAI-1 or TIMP concentrations predict poor survival in patients with various cancers. Recent observations indicate a much more complex role for protease inhibitors in tumour progression and angiogenesis than initially expected. As knowledge in the field of protease biology has improved, the unforeseen complexities of cell associated enzymes and their interaction with physiological inhibitors have emerged, often revealing unexpected mechanisms of action.