Colorectal cancer prevention through dietary and lifestyle modifications.

Several studies indicate that Western dietary and lifestyle factors are responsible for the high incidence of colorectal cancer in industrialized countries. Diets rich in red and processed meat, refined starches, sugar, and saturated and trans-fatty acids but poor in fruits, vegetables, fiber, omega-3 fatty acids and whole grains are closely associated with an increased risk of colorectal cancer. Other main features of the western lifestyle, such as excess body mass and sedentary behaviours, are also strongly associated with higher risk of developing this cancer. Modifications of the western diet, notably increasing consumption of foods from plant origin and reducing that of red meat intake, and maintenance of physical activity and appropriate body mass could substantially reduce colorectal cancer incidence and mortality.

Inhibition of membrane-type 1 matrix metalloproteinase tyrosine phosphorylation blocks tumor progression in mice.

We recently reported that membrane-type 1 matrix metalloproteinase (MT1-MMP) is phosphorylated on its unique cytoplasmic tyrosine residue but the contribution of this event to tumor progression remains unclear. In this work, we show that the non phosphorylizable cell-permeable peptide antennapedia-coupled cytoplasmic MMP-14 (ACM-14), consisting of the mutated (Y573F) cytoplasmic domain of MT1-MMP coupled to antennapedia, inhibits tyrosine phosphorylation of the enzyme and markedly reduces tumor cell proliferation within 3D type I collagen matrices. Interestingly, administration of ACM-14 to mice markedly delays tumor progression and increases survival, these antitumor actions being associated with the induction of extensive tumor necrosis. Overall, these findings suggest that inhibition of MT1-MMP tyrosine phosphorylation may represent an attractive strategy for the development of novel anticancer drugs.

Tissue factor mediates the HGF/Met-induced anti-apoptotic pathway in DAOY medulloblastoma cells.

The classical treatment scheme for medulloblastoma (MB) is based on a tri-therapy approach consisting of surgical tumor resection, craniospinal axis radiation and chemotherapy. With current treatments relying mainly on non-specific cytotoxic therapy, a better understanding of the mechanisms underlying resistance to these treatments is important in order to improve their effectiveness. In this study, we report that stimulation of DAOY with HGF resulted in the protection of these cells against etoposide-induced apoptosis, this anti-apoptotic effect being correlated with an increase in the expression of tissue factor (TF), the initiator of the extrinsic pathway of coagulation. HGF-mediated protection from apoptosis was abolished by a c-Met inhibitor as well as by siRNA-mediated reduction of TF levels, implying a central role of Met-dependent induction of TF expression in this process. Accordingly, stimulation of DAOY with FVIIa, the physiological ligand of TF, also resulted in a significant protection from etoposide-mediated cytotoxicity. Overall, our results suggest the participation of the haemostatic system to drug resistance in MB and may thus provide novel therapeutic approaches for the treatment of these tumors.

Emerging concepts in the regulation of membrane-type 1 matrix metalloproteinase activity.

Pericellular proteolysis mediated by membrane-type 1 matrix metalloproteinase (MT1-MMP) represents an essential component of the cellular machinery involved in the dissolution and penetration of ECM barriers by tumor cells. Although most studies on the proinvasive properties of MT1-MMP have focused on its unusually broad proteolytic activity towards several ECM components and cell surface receptors, recent evidence indicate that the cytoplasmic domain of the enzyme also actively participates in tumor cell invasion by regulating the cell surface localization of MT1-MMP as well as the activation of signal transduction cascades. The identification of the molecular events by which the intracellular domain of MT1-MMP links proteolysis of the surrounding matrix by the enzyme to modification of cell function may thus provide important new information on the mechanisms by which this enzyme controls the invasive behavior of neoplastic cells in vivo.

Identification of membrane-type 1 matrix metalloproteinase tyrosine phosphorylation in association with neuroblastoma progression.

BACKGROUND: Neuroblastoma is a pediatric tumor of neural crest cells that is clinically characterized by its variable evolution, from spontaneous regression to malignancy. Despite many advances in neuroblastoma research, 60% of neuroblastoma, which are essentially metastatic cases, are associated with poor clinical outcome due to the lack of effectiveness of current therapeutic strategies. Membrane-type 1 matrix metalloproteinase (MT1-MMP, MMP-14), an enzyme involved in several steps in tumor progression, has previously been shown to be associated with poor clinical outcome for neuroblastoma. Based on our recent demonstration that MT1-MMP phosphorylation is involved in the growth of fibrosarcoma tumors, we examined the potential role of phosphorylated MT1-MMP in neuroblastoma progression. METHODS: Tyrosine phosphorylated MT1-MMP was immunostained on tissue microarray samples from 55 patients with neuroblastoma detected by mass screening (known to be predominantly associated with favourable outcome), and from 234 patients with standard diagnosed neuroblastoma. In addition, the effects of a non phosphorylable version of MT1-MMP on neuroblastoma cell migration and proliferation were investigated within three-dimensional collagen matrices. RESULTS: Although there is no correlation between the extent of tyrosine phosphorylation of MT1-MMP (pMT1-MMP) and MYCN amplification or clinical stage, we observed greater phosphorylation of pMT1-MMP in standard neuroblastoma, while it is less evident in neuroblastoma from mass screening samples (P = 0.0006) or in neuroblastoma samples from patients younger than one year (P = 0.0002). In vitro experiments showed that overexpression of a non-phosphorylable version of MT1-MMP reduced MT1-MMP-mediated neuroblastoma cell migration and proliferation within a three-dimensional type I collagen matrix, suggesting a role for the phosphorylated enzyme in the invasive properties of neuroblastoma cells. CONCLUSION: Overall, these results suggest that tyrosine phosphorylated MT1-MMP plays an important role in neuroblastoma progression and that its expression is preferentially observed in tumor specimens from neuroblastoma patients showing poor clinical outcome.

On the nature of the intrinsic connectivity of the cat motor cortex: evidence for a recurrent neural network topology.

The details and functional significance of the intrinsic horizontal connections between neurons in the motor cortex (MCx) remain to be clarified. To further elucidate the nature of this intracortical connectivity pattern, experiments were done on the MCx of three cats. The anterograde tracer biocytin was ejected iontophoretically in layers II, III, and V. Some 30-50 neurons within a radius of approximately 250 microm were thus stained. The functional output of the motor cortical point at which biocytin was injected, and of the surrounding points, was identified by microstimulation and electromyographic recordings. The axonal arborizations of the stained neurons were traced under camera lucida. The axon collaterals were extensive, reaching distances of

c-Met activation in medulloblastoma induces tissue factor expression and activity: effects on cell migration.

Met, the receptor for hepatocyte growth factor (HGF), is a receptor tyrosine kinase that has recently emerged as an important contributor to human neoplasia. In physiological and pathological conditions, Met triggers various cellular functions related to cell proliferation, cell migration and the inhibition of apoptosis, and also regulates a genetic program leading to coagulation. Since medulloblastomas (MBs) express high levels of tissue factor (TF), the main initiator of blood coagulation, we therefore examined the link between Met and TF expression in these pediatric tumors. We observed that stimulation of the MB cell line DAOY with HGF led to a marked increase of TF expression and procoagulant activity, in agreement with analysis of clinical MB tumor specimens, in which tumors expressing high levels of Met also showed high levels of TF. The HGF-dependent increase in TF expression and activity required Src family kinases and led to the translocation of TF to actin-rich structures at the cell periphery, suggesting a role of the protein in cell migration. Accordingly, addition of physiological concentrations of the TF activator factor VIIa (FVII) to HGF-stimulated DAOY cells promoted a marked increase in the migratory potential of these cells. Overall, these results suggest that HGF-induced activation of the Met receptor results in TF expression by MB cells and that this event probably contribute to tumor proliferation by enabling the formation of a provisional fibrin matrix. In addition, TF-mediated non-hemostatic functions, such as migration toward FVIIa, may also play a central role in MB aggressiveness.

The stem cell marker CD133 (prominin-1) is phosphorylated on cytoplasmic tyrosine-828 and tyrosine-852 by Src and Fyn tyrosine kinases.

CD133 (prominin-1) is a transmembrane glycoprotein expressed at the surface of normal and cancer stem cells, progenitor cells, rod photoreceptor cells, and a variety of epithelial cells. Although CD133 is widely used as a marker of various somatic and putative cancer stem cells, its contribution to fundamental properties of stem cells such as self-renewal and differentiation remains unknown. CD133 contains a short C-terminal cytoplasmic domain with five tyrosine residues, including a consensus tyrosine phosphorylation site that has not yet been investigated. In this study, we show that CD133 is phosphorylated in human medulloblastoma D283 and Daoy cells, in a Src family kinase-dependent manner. The cytoplasmic domain of CD133 is tyrosine phosphorylated in Daoy cells overexpressing Src and Fyn tyrosine kinases, as well as in vitro using recombinant proteins. Deletion of the C-terminal cytoplasmic domain of CD133 considerably reduced its phosphorylation by Src. To identify the tyrosine phosphorylation sites in CD133, we used matrix-assisted laser desorption/ionization quadrupole time-of-flight (MALDI Q-TOF) and liquid chromatography tandem mass spectrometry (LC-MS/MS). Analysis of tyrosine-phosphorylated CD133 by mass spectrometry and site-directed mutagenesis identified tyrosine-828 and the nonconsensus tyrosine-852 as the major tyrosine phosphorylation sites both in vitro and in intact cells. Identification of CD133 as a substrate for Src-family tyrosine kinases suggests that the cytoplasmic domain of CD133 might play an important role in the regulation of its functions.

The flavonols quercetin, kaempferol, and myricetin inhibit hepatocyte growth factor-induced medulloblastoma cell migration.

Medulloblastoma, the most common malignant brain tumor in children, is a highly metastatic disease, with up to 30% of children having evidence of disseminated disease at presentation. Recently, the hepatocyte growth factor (HGF) and its receptor, the tyrosine kinase Met, have emerged as key components of human medulloblastoma growth and metastasis, suggesting that inhibition of this pathway may represent an attractive target for the prevention and treatment of this disease. Using immunoblotting procedures, we observed that the dietary-derived flavonols quercetin, kaempferol, and myricetin inhibited HGF/Met signaling in a medulloblastoma cell line (DAOY), preventing the formation of actin-rich membrane ruffles and resulting in the inhibition of Met-induced cell migration in Boyden chambers. Furthermore, quercetin and kaempferol also strongly diminished HGF-mediated Akt activation. Interestingly, the inhibitory effects of quercetin on the tyrosine kinase receptor Met [half-maximal inhibitory effect (IC(50)) of 12 micromol/L] or on the Met-induced activation of Akt (IC(50) of 2.5 micromol/L) occurred at concentrations achievable through dietary approaches. These results highlight quercetin, kaempferol, and myricetin as dietary-derived inhibitors of Met activity and suggest that this inhibitory effect may contribute to the chemopreventive properties of these molecules.

Impaired tyrosine phosphorylation of membrane type 1-matrix metalloproteinase reduces tumor cell proliferation in three-dimensional matrices and abrogates tumor growth in mice.

Pericellular proteolysis of the extracellular matrix by membrane type 1-matrix metalloproteinase (MT1-MMP) confers tumor cells with the ability to proliferate within three-dimensional (3D) matrices and sustains tumor growth in mice. In this study, we show that in addition to its matrix-degrading activity, phosphorylation of MT1-MMP on its unique tyrosine residue located within its cytoplasmic sequence (Tyr573) may also participate to these processes. Fibrosarcoma cells expressing a proteolytically active but non-phosphorylable mutant of MT1-MMP showed a markedly reduced proliferation rate when embedded within 3D type I collagen matrices, this antiproliferative effect being correlated with arrest in the G(0)/G(1) phase of the cell cycle. Impaired tyrosine phosphorylation of MT1-MMP also inhibits anchorage-independent growth of HT-1080 cells in soft agar as well as their invasion of collagen barriers, two prominent attributes of tumor cells, suggesting a broad inhibitory effect of the MT1-MMP mutant on tumorigenesis. Accordingly, whereas HT-1080 cells formed well-vascularized tumors containing tyrosine-phosphorylated MT1-MMP, tumor growth was completely abolished by expression of the non-phosphorylable MT1-MMP mutant. These findings thus indicate a close co-operation between the matrix-degrading activity of MT1-MMP and tyrosine phosphorylation of its intracellular domain for tumor cell invasion and proliferation and suggest that the targeting of the intracellular signaling pathways leading to tyrosine phosphorylation of MT1-MMP may represent an unexpected alternative strategy for the inhibition of this enzyme.

Delphinidin, a dietary anthocyanidin, inhibits platelet-derived growth factor ligand/receptor (PDGF/PDGFR) signaling.

Most cancers are dependent on the growth of tumor blood vessels and inhibition of tumor angiogenesis may thus provide an efficient strategy to retard or block tumor growth. Recently, tumor vascular targeting has expanded to include not only endothelial cells (ECs) but also smooth muscle cells (SMCs), which contribute to a mature and functional vasculature. We have reported previously that delphinidin, a major biologically active constituent of berries, inhibits the vascular endothelial growth factor-induced phosphorylation of vascular endothelial growth factor receptor-2 and blocks angiogenesis in vitro and in vivo. In the present study, we show that delphinidin also inhibits activation of the platelet-derived growth factor (PDGF)-BB receptor-beta [platelet-derived growth factor receptor-beta (PDGFR-beta)] in SMC and that this inhibition may contribute to its antitumor effect. The inhibitory effect of delphinidin on PDGFR-beta was very rapid and led to the inhibition of PDGF-BB-induced activation of extracellular signal-regulated kinase (ERK)-1/2 signaling and of the chemotactic motility of SMC, as well as the differentiation and stabilization of EC and SMC into capillary-like tubular structures in a three-dimensional coculture system. Using an anthocyan-rich extract of berries, we show that berry extracts were able to suppress the synergistic induction of vessel formation by basic fibroblast growth factor-2 and PDGF-BB in the mouse Matrigel plug assay. Oral administration of the berry extract also significantly retarded tumor growth in a lung carcinoma xenograft model. Taken together, these results provide new insight into the molecular mechanisms underlying the antiangiogenic activity of delphinidin that will be helpful for the development of dietary-based chemopreventive strategies.

Tissue factor pathway inhibitor (TFPI) interferes with endothelial cell migration by inhibition of both the Erk pathway and focal adhesion proteins.

Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor that is mainly known for its inhibition of tissue factor-mediated coagulation. In addition to its anticoagulant properties, emerging data show that TFPI may also regulate endothelial cell functions via a non-haemostatic pathway. In this work we demonstrate that at concentrations within the physiological range, TFPI inhibits both endothelial cell migration and their differentiation into capillary-like structures in vitro. These effects were specific to endothelial cells since no inhibitory effect was observed on the migration of tumor (glioblastoma) cells. Inhibition of endothelial cell migration was correlated with a concomitant loss in cell adhesion, suggesting an alteration of focal adhesion complex integrity. Accordingly, we observed that TFPI inhibited the phosphorylation of focal adhesion kinase and paxillin, two key proteins involved in the scaffolding of these complexes, and that this effect was specific to endothelial cells. These results suggest that TFPI influences the angiogenic process via a non-haemostatic pathway, by downregulating the migratory mechanisms of endothelial cells.

Sphingosine-1-phosphate induces the association of membrane-type 1 matrix metalloproteinase with p130Cas in endothelial cells.

Membrane-type 1 matrix metalloproteinase (MT1-MMP) plays an important role in sphingosine-1-phosphate(S1P)-dependent migration of endothelial cells but the underlying mechanisms remain largely unknown. Herein, we show that S1P promotes the relocalization of MT1-MMP to peripheral actin-rich membrane ruffles that is coincident with its association with the adaptor protein p130Cas at the leading edge of migrating cells. Immunoprecipitation and confocal microscopy analyses suggest that this interaction required the tyrosine phosphorylation of p130Cas and also involves S1P-dependent phosphorylation of MT1-MMP within its cytoplasmic sequence. The interaction of MT1-MMP with p130Cas at the cell periphery suggests the existence of a close interplay between pericellular proteolysis and signaling pathways involved in EC migration.

The dietary flavones apigenin and luteolin impair smooth muscle cell migration and VEGF expression through inhibition of PDGFR-beta phosphorylation.

Platelet-derived growth factor (PDGF)-dependent recruitment of mural cells such as pericytes and smooth muscle cells plays a central role in the maturation and stabilization of newly formed vasculature during angiogenesis. In this work, we show that the dietary flavones apigenin and luteolin may interfere with this event through their inhibitory effect on PDGF-dependent phosphorylation of PDGF receptor beta (PDGFR-beta) in smooth muscle cells. Inhibition of PDGFR-beta activity by apigenin and luteolin occurred at low concentrations of the molecules and resulted in the inhibition of extracellular signal-regulated kinase and Akt phosphorylation triggered by PDGF, as well as in a marked reduction of the migratory and invasive properties of these cells. Apigenin and luteolin also strongly inhibit the PDGF-dependent increase in vascular endothelial growth factor (VEGF) mRNA levels and the secretion of VEGF by smooth muscle cells as well as vessel formation in the mouse Matrigel plug assay, suggesting that the inhibitory effects of both molecules on smooth muscle cell function result in impaired angiogenesis. Overall, these results identify apigenin and luteolin as dietary-derived inhibitors of PDGFR-beta activity and suggest that this inhibitory effect may contribute to the chemopreventive properties of these molecules.

Role of nutrition in preventing cancer.

OBJECTIVE: To summarize the evidence linking dietary habits to the incidence of several types of cancer with special emphasis on the chemoprotective properties of foods that originate from plants. QUALITY OF EVIDENCE: A large body of epidemiologic, animal, and laboratory literature indicates that as many as 30% of all cancer cases are linked to poor dietary habits. The proportion reaches 70% for cancers of the gastrointestinal tract. MAIN MESSAGE: Studies have consistently linked abundant consumption of plant-based food to a substantial reduction in risk of developing various cancers. Laboratory studies show that this chemopreventive effect is related to the high levels of numerous phytochemicals in this food. These phytochemicals interfere with several cellular processes involved in the progression of cancer and also with inflammatory processes that foster development of cancer. CONCLUSION: Dietary factors play an important role in the high incidence of several types of cancer in Canada. Modification of dietary habits to include daily intake of plant-based food containing anticancer and anti-inflammatory phytochemicals thus represents a promising approach to preventing the development of cancer.

Membrane-type 1 matrix metalloproteinase stimulates cell migration through epidermal growth factor receptor transactivation.

Proteolysis of extracellular matrix proteins by membrane-type 1 matrix metalloproteinase (MT1-MMP) plays a pivotal role in tumor and endothelial cell migration. In addition to its proteolytic activity, several studies indicate that the proinvasive properties of MT1-MMP also involve its short cytoplasmic domain, but the specific mechanisms mediating this function have yet to be fully elucidated. Having previously shown that the serum factor sphingosine 1-phosphate stimulates MT1-MMP promigratory function through a process that involves its cytoplasmic domain, we now extend these findings to show that this cooperative interaction is permissive to cellular migration through MT1-MMP-dependent transactivation of the epidermal growth factor receptor (EGFR). In the presence of sphingosine 1-phosphate, MT1-MMP stimulates EGFR transactivation through a process that is dependent upon the cytoplasmic domain of the enzyme but not its catalytic activity. The MT1-MMP-induced EGFR transactivation also involves G(i) protein signaling and Src activities and leads to enhanced cellular migration through downstream extracellular signal-regulated kinase activation. The present study, thus, elucidates a novel role of MT1-MMP in signaling events mediating EGFR transactivation and provides the first evidence of a crucial role of this receptor activity in MT1-MMP promigratory function. Taken together, our results suggest that the inhibition of EGFR may represent a novel target to inhibit MT1-MMP-dependent processes associated with tumor cell invasion and angiogenesis.

VEGF increases the fibrinolytic activity of endothelial cells within fibrin matrices: involvement of VEGFR-2, tissue type plasminogen activator and matrix metalloproteinases.

Proteolysis of fibrin matrices by endothelial cells plays essential roles in the migratory and morphogenic differentiation processes underlying angiogenesis. Using an in vitro fibrinolysis model consisting of human umbilical vein endothelial cells (HUVECs) embedded in a three dimensional fibrin matrix, we show that VEGF, an angiogenic cytokine that plays a crucial role in the onset of angiogenesis, is a potent activator of HUVEC-mediated fibrinolysis. This VEGF-dependent fibrin degradation was completely abrogated by inhibitors of either the plasminogen activator/plasmin or matrix metalloproteinases (MMP) proteolytic systems, suggesting the involvement of both classes of proteases in fibrin degradation. Accordingly, VEGF-induced fibrinolysis correlated with an increase in the expression of tPA and of some MMPs, such as MT2-MMP and was completely blocked by a neutralizing antibody against tPA. Overall, these results indicate that efficient proteolysis of three dimensional fibrin matrices during VEGF-mediated angiogenesis involves a complex interplay between the MMP and plasmin-mediated proteolytic systems.

Modulation of p-glycoprotein function by caveolin-1 phosphorylation.

p-glycoprotein (p-gp) is an ATP-binding cassette transporter and its overexpression is responsible for the acquisition of the multidrug resistance phenotype in human tumors. p-gp is localized at the blood-brain barrier and is involved in brain cytoprotection. Our previous work used immunoprecipitation to show that caveolin-1 can interact with p-gp. In this study, we provide evidence that caveolin-1 regulates p-gp transport activity in a rat brain endothelial cell line (RBE4). Down-regulation of caveolin-1 by siRNA reduced the interaction between p-gp and caveolin-1, followed by a decrease in [3H]-Taxol and [3H]-Vinblastine accumulation in RBE4 cells. The latter result showed that down-regulation of caveolin-1 enhanced p-gp transport activity. RBE4 cells were also transfected with Sarcoma in order to modulate caveolin-1 phosphorylation. Overexpression of Sarcoma, a protein tyrosine kinase, stimulated caveolin-1 phosphorylation and increased both [3H]-Taxol and [3H]-Vinblastine accumulation as well as Hoechst 33342 accumulation. Transfection of caveolin-1 inhibits p-gp transport activity. Conversely, transfection of the mutant cavY14F decreased the p-gp/caveolin-1 interaction and reduced accumulation of the two p-gp substrates. Thus, our data show that caveolin-1 regulates p-gp function through the phosphorylation state of caveolin-1 in endothelial cells from the blood-brain barrier.

Src-dependent phosphorylation of membrane type I matrix metalloproteinase on cytoplasmic tyrosine 573: role in endothelial and tumor cell migration.

Membrane type 1 matrix metalloproteinase (MT1-MMP) is a transmembrane MMP that plays important roles in migratory processes underlying tumor invasion and angiogenesis. In addition to its matrix degrading activity, MT1-MMP also contains a short cytoplasmic domain whose involvement in cell locomotion seems important but remains poorly understood. In this study, we show that MT1-MMP is phosphorylated on the unique tyrosine residue located within this cytoplasmic sequence (Tyr(573)) and that this phosphorylation requires the kinase Src. Using phosphospecific antibodies recognizing MT1-MMP phosphorylated on Tyr(573), we observed that tyrosine phosphorylation of the enzyme is rapidly induced upon stimulation of tumor and endothelial cells with the platelet-derived chemoattractant sphingosine-1-phosphate, suggesting a role in migration triggered by this lysophospholipid. Accordingly, overexpression of a nonphosphorylable MT1-MMP mutant (Y573F) blocked sphingosine-1-phosphate-induced migration of Human umbilical vein endothelial cells and HT-1080 (human fibrosarcoma) cells and failed to stimulate migration of cells lacking the enzyme (bovine aortic endothelial cells). Altogether, these findings strongly suggest that the Src-dependent tyrosine phosphorylation of MT1-MMP plays a key role in cell migration and further emphasize the importance of the cytoplasmic domain of the enzyme in this process.

Anthocyanidins inhibit migration of glioblastoma cells: structure-activity relationship and involvement of the plasminolytic system.

Complete resection of malignant glioblastomas is usually impossible because of diffuse and widespread invasion of tumor cells, and complementary approaches need to be developed in order to improve the efficacy of current treatments. Consumption of fruits and berries has been associated with decreased risk of developing cancer and there is great interest in the use of molecules from dietary origin to improve anticancer therapies. In this work, we report that the aglycons of the most abundant anthocyanins in fruits, cyanidin (Cy), delphinidin (Dp), and petunidin (Pt), act as potent inhibitors of glioblastoma cell migration. Dp clearly exhibited the highest inhibitory potency, this effect being related to the ortho-dihydroxyphenyl structure on the B-ring and the presence of a free hydroxyl group at position 3. Dp decreases the expression of both urokinase-type plasminogen activator receptor (uPAR) and the low-density lipoprotein receptor-related protein (LRP), acting at the transcriptional levels. In addition, Dp upregulated urokinase-type plasminogen activator (uPA) and downregulated the plasminogen activator inhibitor-1 (PAI-1) but decreased, in a concentration-dependent manner, the uPA-dependent conversion of plasminogen to plasmin, indicating that the upregulation of uPA observed with these compounds was not associated with induction of the plasminolytic activity. Overall, these results demonstrate that Dp, Pt, and Cy affect plasminogen activation, thus leading to the inhibition of glioblastoma cell migration and therefore they may be helpful for the development of new strategies for cancer prevention and therapy.