From a unique cell to metastasis is a long way to go: clues to stromelysin-3 participation

Stromelysin-3 (ST3) overexpression is associated with poor patient clinical outcome in numerous carcinomas. The ST3 is expressed by peritumoral fibroblast-like cells. Review of the literature shows that ST3 is an active partner of cancer cells along the whole natural cancer history, and is essential for optimal tumor development as it reduces death of cancer cells invading adjacent connective tissues at the primary tumor site. Paradoxically, ST3 lowers metastasis development in vivo in mice. However, this beneficial effect does not counterbalance the deleterious anti-apoptotic function of ST3.

Ghrelin/motilin-related peptide is a potent prokinetic to reverse gastric postoperative ileus in rat

A novel peptide called ghrelin or motilin-related-peptide (MTLRP) was found in the stomach of various mammals. We studied its effect on the motor function of the rat gastrointestinal tract. In normal, conscious unoperated animals, ghrelin/MTLRP (5 or 20 microg/kg iv) significantly accelerated the gastric emptying of a methylcellulose liquid solution (gastric residue after 15 min: 57 +/- 7, 42 +/- 11, 17 +/- 4, and 9 +/- 3% of the ingested meal with doses of 0, 1, 5, and 20 microg/kg iv, respectively) Transit of the methylcellulose liquid solution was also accelerated by ghrelin/MTLRP in the small intestine but not in the colon. Des-[Gln(14)]ghrelin, also found in the mammalian stomach, was as potent as ghrelin in emptying the stomach (gastric residue after 15 min: 12 +/- 3% at a dose of 20 microg/kg iv). In rats in which postoperative gastrointestinal ileus had been experimentally induced, ghrelin/MTLRP (20 microg/kg iv) reversed the delayed gastric evacuation (gastric residue after 15 min: 28 +/- 7% of the ingested meal vs. 82 +/- 9% with saline). In comparison, the gastric ileus was not modified by high doses of motilin (77 +/- 7%) or erythromycin (82 +/- 6%) and was only partially improved by calcitonin gene-related peptide (CGRP) 8-37 antagonist (59 +/- 7%). Ghrelin/MTLRP, therefore, accelerates the gastric emptying and small intestinal transit of a liquid meal and is a strong prokinetic agent capable of reversing the postoperative gastric ileus in rat.

Adipocyte hypertrophy in stromelysin-3 deficient mice with nutritionally induced obesity

Several matrix metalloproteinases (MMPs), including the stromelysins MMP-3 and MMP-11, are expressed in adipose tissue. To investigate a potential role of MMP-11 (stromelysin-3) in adipose tissue development, five-week-old male wild-type mice (MMP-11+/+) or mice with deficiency of MMP-11 (MMP-11-/-) were fed a high fat diet (HFD, 42% fat) for 15 weeks. Haematologic parameters, including white and red blood cells, platelets, haemoglobin and haematocrit, and metabolic parameters including glucose, triglycerides and total cholesterol were not different for both genotypes. At the time of sacrifice, the body weight of the MMP-11-/- mice was higher than that of the MMP-11+/+ mice (36+/-1.4 g versus 29+/-0.9 g, p = 0.0002). The weight of the isolated subcutaneous (SC) and gonadal (GON) fat deposits was also higher in MMP-11-/- mice (620+/-150 mg versus 280+/-28 mg for SC fat, and 970+/-180 mg versus 430+/-62 mg, p < 0.05, for GON fat). Adipocytes in MMP-11-/- adipose tissue were hypertrophic as compared to MMP-11+/+ adipocytes (volume of 57+/-12 x 10(3) microm3 versus 31+/-2.4 x 10(3) microm3 for SC fat, and 100+/-18 x 10(3) microm3 versus 57+/-7.6 x 10(3) microm3 for GON fat; both p < 0.06). In nutritionally induced obesity models in mice a potential role of the fibrinolytic system was suggested in adipocyte hypertrophy. The hypertrophy observed in this model is, however, not related to changes in fibrinolytic parameters, as suggested by our finding that levels of t-PA, u-PA and PAI-1 antigen as well as t-PA and u-PA activity were not different in SC or GON adipose tissue extracts of both genotypes. As the main biological function of MMP-11 remains unknown, it is not clear whether the adipocyte hypertrophy in MMP-11-/- adipose tissue is directly related to the deficiency or to other pathways affected by MMP-11.

Identification of cDNA encoding motilin related peptide/ghrelin precursor from dog fundus

A novel protein expressed by entero-endocrine cells of the mouse stomach was named prepromotilin Related Peptide (ppMTLRP) since it shares sequence similarities with the prepromotilin (Tomasetto et al.). The mouse ppMTLRP was found identical to the rat precursor of ghrelin (ppghrelin), an endogenous ligand specific for the Growth Hormone Secretagogue receptor identified from rat stomach (Kojima et al.). In the present study the cDNA encoding the dog counterpart of ppMTLRP/Ghrelin has been isolated and sequenced. The dog ppMTLRP/Ghrelin cDNA showed scores of respectively 80% and 75% homology with its human and mouse counterparts. By translation of the dog ppMTLRP/Ghrelin cDNA sequences, two ORFs could be deduced encoding either a 117 amino acid ppMTLRP/Ghrelin or the deleted Gln14 ppMTLRP/Ghrelin, as it was also known in mouse, rat and man. The dog ppMTLRP/Ghrelin shared 91% similarity and 78% identity, and 89% similarity and 78% identity with the human and mouse ppMTLRP/Ghrelin proteins respectively. The best score of homology was found in the MTLRP/Ghrelin sequence itself. Indeed the dog MTLRP/Ghrelin peptide shared 100% similarity and 93% identity, and 96% identity and similarity, with the human and mouse MTLRP/Ghrelin. Using Northern blot analysis to study dog ppMTLRP/Ghrelin gene expression on dog adult gut tissues, maximal expression level was found in the stomach fundus and corpus, and no expression could be detected in the stomach antrum nor in the duodenum, jejunum, ileum, colon or liver. In conclusion, we have identified ppMTLRP/Ghrelin from dog, and found that it is highly conserved with man, mouse or rat. The expression pattern along the gastro-intestinal tract is similar to the expression pattern previously described in mouse.

Transcription regulation and protein subcellular localization of the truncated basic hair keratin hHb1-DeltaN in human breast cancer cells

An aberrant truncated hHb1 hair keratin transcript, named hHb1-DeltaN, was previously identified in breast carcinomas. No normal tissue tested so far, including hairy skin, expressed hHb1-DeltaN, indicating that hHb1-DeltaN is related to carcinogenesis. In the present study, we investigated the mechanism by which such truncated transcript was generated in breast cancer cell lines. We found that hHb1-DeltaN transcription is initiated at an unusual cryptic promoter within the fourth intron of the hHb1 gene and is dependent on two proximal Sp1 binding sites for its baseline activity. Moreover, hHb1-DeltaN transcription is increased in response to DNA demethylation by the 5-aza-2'-deoxycytidine drug. This induction is dependent on protein neosynthesis, indicating that an additional factor is required. In addition, we showed that the hHb1-DeltaN transcript is translated in vivo as a truncated hHb1 protein that is missing the 270 amino-terminal residues. The hHb1-DeltaN protein exhibits a filament pattern throughout the cytoplasm and partially co-localizes with cytokeratin filaments, indicating its participation in the cytoskeleton network. hHb1-DeltaN might alter the adhesive properties of cancer cells.

Alcohol-related problems and fitness to drive

This paper analyses the alcohol consumption patterns in Spanish drivers, the incidence of alcohol-related problems and attempts to ascertain whether, in the end, drivers with alcohol-related problems are considered fit or unfit to drive. In accordance with Spanish and European Union legislation, driving licences cannot be issued or renewed to people suffering from alcohol-related problems. A medical, psychological and eyesight evaluation was performed to test the driving fitness of 8043 drivers attending 25 Medical Driving Test Centres on a national scale. Among other things, information was collected on the patterns of alcohol consumption, the AUDIT and CAGE tests, the incidence of alcohol-related problems (DSM-IV criteria for abuse, dependence and alcohol-induced disorder), as well as an evaluation of their fitness to drive. In all, 60.3% of drivers drink alcohol on a regular basis; 7.3% of drivers scored > or = 8 points in the AUDIT test, and 2% met criteria for DSM-IV alcohol abuse, dependence or induced disorder. Drivers with alcohol-related problems have been involved in traffic accidents (23.2%) and have infringed driving regulations (18.7%) more frequently (P < 0.0001) than those without alcohol-related problems. Of those with alcohol-related problems, 72.2% were considered fit to drive. The study reveals that alcohol consumption is common among drivers, that a significant number of drivers have alcohol-related problems, and that three in four of the latter were considered fit to drive.

Crystal structure of the stromelysin-3 (MMP-11) catalytic domain complexed with a phosphinic inhibitor mimicking the transition-state

Stromelysin-3 (ST3) is a matrix metalloproteinase (MMP-11) whose proteolytic activity plays an important role in tumorigenicity enhancement. In breast cancer, ST3 is a bad prognosis marker: its expression is associated with a poor clinical outcome. This enzyme therefore represents an attractive therapeutic target. The topology of matrix metalloproteinases (MMPs) is remarkably well conserved, making the design of highly specific inhibitors difficult. The major difference between MMPs lies in the S(1)' subsite, a well-defined hydrophobic pocket of variable depth. The present crystal structure, the first 3D-structure of the ST3 catalytic domain in interaction with a phosphinic inhibitor mimicking a (d, l) peptide, clearly demonstrates that its S(1)' pocket corresponds to a tunnel running through the enzyme. This open channel is filled by the inhibitor P(1)' group which adopts a constrained conformation to fit this pocket, together with two water molecules interacting with the ST3-specific residue Gln215. These observations provide clues for the design of more specific inhibitors and show how ST3 can accommodate a phosphinic inhibitor mimicking a (d, l) peptide. The presence of a water molecule interacting with one oxygen atom of the inhibitor phosphinyl group and the proline residue of the Met-turn suggests how the intermediate formed during proteolysis may be stabilized. Furthermore, the hydrogen bond distance observed between the methyl of the phosphinic group and the carbonyl group of Ala182 mimics the interaction between this carbonyl group and the amide group of the cleaved peptidic bond. Our crystal structure provides a good model to study the MMPs mechanism of proteolysis.

Mouse Trefoil factor genes: genomic organization, sequences and methylation analyses

The mammalian Trefoil Factors (TFFs), TFF1/pS2, TFF2/SP and TFF3/ITF, are expressed and secreted throughout the gastrointestinal tract with a specific and complementary pattern. These proteins exhibit common functions in the protection and repair process of the gastrointestinal epithelial barrier. Here, we report the clustered organization of the three mouse TFF genes in a 40 kb DNA segment, in a head to tail orientation in the following order: TFF1, TFF2, and TFF3. Computer comparison of the mouse TFF promoter sequences to their human counterparts revealed conserved boxes in both mouse and human genes. Promoter methylation analyses showed that, in tissues where these genes are normally expressed, the proximal promoters of TFF1 and TFF2 are specifically not methylated and that of TFF3 is partially demethylated. In contrast, in organs that do not express TFFs, the promoters of the three genes are methylated. These findings strongly argue for the involvement of epigenetic mechanisms in the regulation of TFF expression in normal and pathological conditions.

High cancer cell death in syngeneic tumors developed in host mice deficient for the stromelysin-3 matrix metalloproteinase

Matrix metalloproteinases (MMPs) are extracellular enzymes. Some of them are known to be involved in tumor development and/or progression. Several cellular functions have been proposed for MMPs during malignant processes. Notably, they may be involved in tissue-remodeling processes through their ability to digest matrix components or to participate in tumor neoangiogenesis and, subsequently, in cancer cell proliferation. One of these MMPs, stromelysin-3 (ST3/MMP11), although devoid of enzymatic activity against the matrix components, is associated with human tumor progression and poor patient clinical outcome. Using several in vivo experimental models, it has been demonstrated that ST3 expression by the fibroblastic cells surrounding malignant epithelial cells promotes tumorigenesis in a paracrine manner. The present study was devoted to the identification of the cellular function underlying this ST3-induced tumor promotion using a syngeneic tumorigenesis model in mice. Our results show that ST3 exhibits a new and unexpected role for a MMP, because ST3-increased tumorigenesis does not result from increased neoangiogenesis or cancer cell proliferation but from decreased cancer cell death through apoptosis and necrosis. Thus, during malignancy, the cellular function of ST3 is to favor cancer cell survival in the stromal environment.

Identification of CGA as a novel estrogen receptor-responsive gene in breast cancer: an outstanding candidate marker to predict the response to endocrine therapy

The estrogen receptor (ER) status of breast tumors is used to identify patients who may respond to endocrine agents such as tamoxifen. However, ER status alone is not perfectly predictive, and there is a pressing need for more reliable markers of endocrine responsiveness. Here, we identified the well-known CGA gene (coding for the alpha subunit of glycoprotein hormones) as a new ERalpha-responsive gene in human breast cancer cells. We used a real-time quantitative reverse transcription-PCR assay to quantify CGA mRNA copy numbers in a large series of breast tumors. CGA overexpression (> 10 SD above the mean for normal breast tissues) was observed in 44 of 131 (33.6%) breast tumor RNAs, ranging from 20 to 16,500 times the level in normal breast tissues; the highest levels of CGA gene expression were close to those observed in placenta. Significant links were observed between CGA gene overexpression and Scarff-Bloom-Richardson histopathological grade I+II (P = 0.015), and progesterone (P = 0.0009) and estrogen (P < 10(-7)) receptor positivity, which suggested that CGA is a marker of low tumor aggressiveness. We observed CGA mRNA overexpression in 44 of 90 (48.9%) ERalpha-positive tumors and in none of the 41 ERalpha-negative tumors. Immunohistochemical studies demonstrated that human chorionic gonadotropin alpha protein was strictly limited to ERalpha-positive tumor cells. Overexpression of the CGA gene was not accompanied by overexpression of the CGB gene. Our results also suggest that CGA could be a more reliable marker than PS2 and PR for ERalpha functionality and, thus, for endocrine responsiveness. Moreover, the CGA marker has the added value of dichotomizing ERalpha-positive patients into two subgroups of similar size. Specific antibodies directed to secreted human chorionic gonadotropin alpha protein are commercially available, thus facilitating the future application of this marker to the clinical management of breast cancer.

The steroidogenic acute regulatory protein homolog MLN64, a late endosomal cholesterol-binding protein

MLN64 is a transmembrane protein that shares homology with the cholesterol binding domain (START domain) of the steroidogenic acute regulatory protein. The steroidogenic acute regulatory protein is located in the inner membrane of mitochondria, where it facilitates cholesterol import into the mitochondria. Crystallographic analysis showed that the START domain of MLN64 is a cholesterol-binding domain. The present work was undertaken to determine which step of the intracellular cholesterol pathway MLN64 participates in. Using immunocytofluorescence, MLN64 colocalizes with LBPA, a lipid found specifically in late endosomes. Electron microscopy indicates that MLN64 is restricted to the limiting membrane of late endosomes. Microinjection or endocytosis of specific antibodies shows that the START domain of MLN64 is cytoplasmic. Deletion and mutagenesis experiments demonstrate that the amino-terminal part of MLN64 is responsible for its addressing. Although this domain does not contain conventional dileucine- or tyrosine-based targeting signals, we show that a dileucine motif (Leu(66)-Leu(67)) and a tyrosine residue (Tyr(89)) are critical for the targeting or the proper folding of the molecule. Finally, MLN64 colocalizes with cholesterol and Niemann Pick C1 protein in late endosomes. However, complementation assays show that MLN64 is not involved in the Niemann Pick C2 disease which, results in cholesterol lysosomal accumulation. Together, our results show that MLN64 plays a role at the surface of the late endosomes, where it might shuttle cholesterol from the limiting membrane to cytoplasmic acceptor(s).

In vivo and in vitro effects of ghrelin/motilin-related peptide on growth hormone secretion in the rat

Ghrelin (Ghr), a 28 amino acid gastric peptide with an n-octanoylation on Ser 3, has recently been identified as an endogenous ligand of the growth hormone secretagogue (GHS) receptor. A cDNA was also isolated from a mouse stomach library encoding a protein named prepromotilin-related peptide (ppMTLRP) which shares sequence similarities with prepromotilin. Mouse and rat ppMTLRP sequences (rGhr) are identical and show 89% identity with human ghrelin (hGhr). By analogy with promotilin, cleavage of proMTLRP into an 18 amino acid endogenous processed peptide can be assumed on the basis of a conserved dibasic motif in position 9-10 of its sequence. In the present work, we compared the GH-releasing activity of rGhr28/MTLRP and of hGhr28/MTRLP with that of a shorter form of the peptide, hGhr18. A short peptide devoid of Ser-3 n-octanoylation hGhr18[-] was also tested. Addition of rGhr28, hGhr28 and hGhr18 stimulated GH release to the same extent from superfused pituitaries. The effect was dose dependent in a 10(-8) to 10(-6) M concentration range. In contrast, hGhr 18[-] was inactive. In freely moving animals, both rGhr28 and hGhr28 (10 microg, i.v.) stimulated GH release, whereas the same dose of hGhr18 or of hGhr18[-] was ineffective. After rGhr28, GH plasma levels increased as early as 5 min after injection and returned to basal values within 40-60 min. Expressed as percent stimulation, administration of rGhr28 was equally effective when injected during troughs or peaks of GH. Plasma concentrations of prolactin, adrenocorticotropin and leptin were not modified. Spontaneous GH secretory episodes were no longer observed within 3 h of rGhr28 treatment, but repeated administration of the secretagogue at 3- to 4-hour intervals resulted in a similar GH response. Activation of somatostatin (SRIH) release by ether stress did not blunt the GH response to rGhr28. This suggests that the secretagogue acts in part by inhibiting endogenous SRIH, as further substantiated by the ability of rGhr28 (10(-6) M), to decrease the amplitude of 25 mM K+-induced SRIH release from perifused hypothalami. In conclusion, (1) n-octanoylation of Ghrs and the shorter form hGhr18 is essential for the direct pituitary GH-releasing effect of this new family of endogenous GHSs; (2) only the longer forms are active in vivo and (3) inhibition of SRIH release appears involved in the mechanism of Ghr action.

C2PA, a new protein expressed during mouse spermatogenesis

C2PA is a novel protein that contains a C2 membrane binding domain, a PDZ protein/protein interaction domain, and an ATP/GTP binding domain. C2PA is expressed during embryogenesis from 8.5 days post-coitum (dpc) until birth. After birth, C2PA expression is mainly observed in the post-natal and adult testis. During spermatogenesis, C2PA transcripts are specifically observed in the spermatocytes, whereas spermatogonia and spermatids are negative. Taken together, these results suggest that C2PA might be involved in cell signaling pathways occurring during spermatogenesis.

Identification and characterization of a novel gastric peptide hormone: the motilin-related peptide

BACKGROUND & AIMS

This study looked for new proteins with expression restricted to the gastric epithelium that may provide insight to the differentiation and function of the gastric unit.

METHODS

A novel complementary DNA was isolated and sequenced, and its expression was examined in mouse tissues at both messenger RNA and protein levels. Subcellular localization was studied using immunoelectron microscopy. The posttraductional processing of the protein was analyzed in vitro by protein microsequencing and in vivo by Western blotting.

RESULTS

We identified a novel protein that is mainly expressed by the secretory granules of the stomach enteroendocrine cells. This protein has sequence similarity with prepromotilin, the precursor of the motilin hormone and the motilin-associated peptide. As for the prepromotilin, a posttraductional maturation leads to a secreted peptide that is further cleaved at a dibasic site and gives rise to the motilin-related peptide (MTLRP) and MTLRP-associated peptide.

CONCLUSIONS

We have identified and characterized a novel gene encoding the preproMTLRP protein. MTLRP presents similarity to motilin and is specifically expressed by enteroendocrine cells of the stomach and therefore represents a novel hormone.

Demonstration in vivo that stromelysin-3 functions through its proteolytic activity

Stromelysin-3 (ST3), a matrix metalloproteinase (MMP) expressed in aggressive carcinomas, has been shown to promote tumor development in different in vivo experimental models. However, the inability of its mature form to degrade extracellular matrix components casts doubt on whether ST3 functions in vivo as a protease. In this study, we evaluated whether the ST3 tumor-promoting effect could be ascribed to its proteolytic activity and whether this putative protease could be targeted with MMP inhibitors. Catalytically inactive mutant cDNA of human (h) ST3 or mouse (m) ST3 were generated and transfected into MCF7 cells. When injected into nude mice in the presence of matrigel, the mutant-bearing cells did not exhibit the enhanced tumorigenicity elicited by MCF7 cells transfected with wild-type ST3 cDNA. In a second approach, TIMP2 overproduction in MCF7 cells expressing hST3 was induced by retroviral infection. The co-expression of ST3 and TIMP2 failed to enhance the tumorigenicity of MCF7 cells. Notably, matrigel depleted of low-molecular-weight proteins and growth factors failed to promote the tumorigenicity of ST3-expressing MCF7 cells. These findings provide the first in vivo evidence that ST3 is indeed a protease that can modulate cancer progression by remodeling extracellular matrix and probably by inducing it to release the necessary microenvironmental factors. Thus, ST3 represents an interesting target for specific MMP inhibition.

pS2/TFF1 interacts directly with the VWFC cysteine-rich domains of mucins

BACKGROUND & AIMS

Trefoil factors (TFFs) are secreted gastrointestinal proteins that have been shown to protect and promote healing of the gastrointestinal tract. Moreover, pS2/TFF1 is essential for normal differentiation of the gastric mucosa because deficient mice develop antropyloric adenomas. To date, it is unclear how TFFs mediate their functions.

METHODS

Using the yeast 2-hybrid system, we attempted to identify murine TFF1 interacting proteins by screening a stomach and duodenum complementary DNA (cDNA) expression library.

RESULTS

Four positive clones were isolated. Sequence and expression studies showed that they corresponded to the murine counterpart of human cDNA sequences encoding carboxy-terminal fragments of mMuc2 (489 residues) and mMuc5AC (427, 430, and 894 residues) mucin proteins. Mutagenesis experiments showed that TFF1 interacts with the 2 mucins through binding with their VWFC1 and VWFC2 (von Willebrand factor C) cysteine-rich domains.

CONCLUSIONS

These results show that the gastrointestinal protective effect of TFF1, and presumably of the other TFFs, is caused at least partially by their participation, via mucin binding, in the correct organization of the mucous layer that protects the apical side of the mucosa from deleterious luminal agents.

Accelerated neointima formation after vascular injury in mice with stromelysin-3 (MMP-11) gene inactivation

The hypothesis that stromelysin-3 (MMP-11), a unique member of the matrix metalloproteinase (MMP) family, plays a role in neointima formation was tested with the use of a vascular injury model in wild-type (MMP-11(+/+)) and MMP-11-deficient (MMP-11(-/-)) mice. Neointima formation 2 to 3 weeks after electric injury of the femoral artery was significantly enhanced in MMP-11(-/-) as compared with MMP-11(+/+) mice, in both mice of a pure 129SV genetic background (0.014 versus 0.0010 mm(2) at 2 weeks, P<0.001) and those of a 50/50 mixed 129SV/BL6 background (0.030 versus 0.013 mm(2) at 3 weeks, P<0.05). The medial areas were comparable, resulting in intima/media ratios that were significantly increased in MMP-11(-/-) as compared with MMP-11(+/+) arteries, in mice of both the 129SV (1. 0 versus 0.18, P<0.001) and mixed (1.5 versus 0.70, P<0.05) backgrounds. Nuclear cell counts in cross-sectional areas of the intima of the injured region were higher in arteries from MMP-11(-/-) mice than in those from MMP-11(+/+) mice (210 versus 48, P<0.001, in pure 129SV mice and 290 versus 150, P<0.01, in mice of the mixed genetic background). Immunocytochemical analysis revealed that alpha-actin-positive and CD45-positive cells were more abundant in intimal sections of MMP-11(-/-) mice. Degradation of the internal elastic lamina was more extensive in arteries of MMP-11(-/-) mice than in those of MMP-11(+/+) mice (39% versus 6.8% at 3 weeks, P<0. 005). The mechanisms by which MMP-11 could impair elastin degradation and cellular migration in this model remain, however, unknown.

Presence of high levels of MT1-MMP protein in fibroblastic cells of human invasive carcinomas

Matrix metalloproteinase 2 (MMP2) activity is associated with the aggressiveness of human cancers. Therefore, the mechanisms regulating its activation are of great interest for a better understanding of malignant invasive processes. MT1-MMP, a membrane-bound MMP, is involved in the conversion of the latent form of MMP2 to the active one. In the present study, we have raised 3 monoclonal antibodies (Mabs) directed against 3 different epitopes of human MT1-MMP, which we used to investigate the expression and cellular localization of MT1-MMP protein in human carcinomas. MT1-MMP protein was present in all invasive carcinomas tested, and it was almost exclusively located to the stromal cells and not to cancer cells as previously reported, suggesting that MMP2 activation might be a peri-fibroblastic event.

Phosphinic pseudo-tripeptides as potent inhibitors of matrix metalloproteinases: a structure-activity study

Several phosphinic pseudo-tripeptides of general formula R-XaaPsi(PO(2)-CH(2))Xaa'-Yaa'-NH(2) were synthesized and evaluated for their in vitro activities to inhibit stromelysin-3, gelatinases A and B, membrane type-1 matrix metalloproteinase, collagenases 1 and 2, and matrilysin. With the exception of collagenase-1 and matrilysin, phosphinic pseudo-tripeptides behave as highly potent inhibitors of matrix metalloproteinases, provided they contain in P(1)' position an unusual long aryl-alkyl substituent. Study of structure-activity relationships regarding the influence of the R and Xaa' substituents in this series may contribute to the design of inhibitors able to block only a few members of the matrix metalloproteinase family.

Purification of active matrix metalloproteinase catalytic domains and its use for screening of specific stromelysin-3 inhibitors

The matrix metalloproteinase (MMP) stromelysin-3 (ST3) has been shown to be involved in malignant tumor progression and therefore represents an attractive therapeutical target. In order to screen for ST3 synthetic inhibitors, we have produced and purified the catalytic domain of ST3, matrilysin, stromelysin-2, and membrane type-1 MMP from inclusion bodies in a bacterial system. Our strategy allowed the purification of MMPs directly in the active form, thereby avoiding in vitro activation. A total of 140,000 synthetic compounds from the Bristol-Myers Pharmaceutical Research Institute chemical deck were tested, using a substrate-based colorimetric enzymatic assay, in which ST3 activity was evaluated through its ability to cleave and inactivate alpha-1 proteinase inhibitor. One ST3 inhibitor belonging to the cephalosporin family of antibiotics was thereby identified.

Expression of human hair keratin basic 1 in pilomatrixoma. A study of 128 cases

Hard keratins are expressed in normal hair and nails, and are characterized by a higher cysteine content than cytokeratins. Previous studies have suggested a coexpression of hard keratins and cytokeratins in pilomatrixoma, a benign follicular tumour which could originate from the hair matrix. Human hair keratin basic 1 (hHb1) is a newly characterized hair keratin which is expressed specifically by cortical cells of the normal hair shaft. A preliminary study has suggested that hHb1 could be expressed in pilomatrixoma. In order to confirm this hypothesis, we have studied a series of 128 pilomatrixomas by in situ hybridization, using a 35S-labelled hHb1-specific probe. The anti-sense probe was used as a negative control. Among these pilomatrixomas, six were early cases, 60 were classified into the intermediate stage (either fully developed or early regressive cases) and 62 were late regressive tumours made of shadow cells only. Forty-seven tumours showed hHb1 expression (37%), all being intermediate stage pilomatrixomas. The areas positively stained by the probe were band-like structures made of transitional cells only, which were very close to cells showing tricholemmal keratinization features. Neither the basophilic matrix cells nor the shadow cells expressed hHb1. Our results suggest that pilomatrixomas can differentiate towards cortical cells during their maturation process, as this keratin is specifically expressed in the cortex of the normal hair shaft. These data are consistent with previous studies which showed the expression of a hard keratin group in transitional cells by immunohistochemistry. The histogenesis of basophilic cells of pilomatrixoma is controversial, but it is likely that transitional cells represent an equivalent of the hair cortex.

Expression of a truncated form of hHb1 hair keratin in human breast carcinomas

Human hHb1 belongs to the type II hard keratin family and is physiologically expressed in hair shafts. In the present study, using specific 3' and 5' probes for hHb1, we established that breast carcinomas ectopically express a hHb1 5'-truncated mRNA, and that this transcript is restricted to malignant epithelial cells. Furthermore, an in vitro study indicated that it could be translated. We concluded that, in breast carcinomas, expression of truncated hHb1 is related to epithelial cell transformation. Because the hHb1 gene maps to 12q11-q13, a chromosome region known to present several breakpoints in solid tumours, we propose that the hHb1 gene might represent a target for such alterations.

[Extracellular proteases of stromal origin: contribution to tumor progression and therapeutic perspectives]

For a long time, extracellular proteinases were thought to be expressed by the cancerous cells and only able to cleave extracellular matrix components, in order to promote tumor cell invasion. Recent works have now demonstrated that these proteinases are currently synthesized by stromal fibroblastic cells and that some of them may exhibit additive function(s). These findings lead to a new therapeutical concept leading to target the activity of stromal proteinases, and most notably of the matrix metalloproteinases.

Lasp-1, a novel type of actin-binding protein accumulating in cell membrane extensions

The Lasp-1 gene, which has been localized to the q12-q21 region of human chromosome 17, is amplified and overexpressed in human breast cancers. In addition to the previously reported LIM and SH3 domains of Lasp-1, we report here the identification of an actin-binding domain in the core of the protein. This domain is functional as we demonstrate that Lasp-1 binds actin in vivo and in vitro. In addition, confocal analysis of the Lasp-1 subcellular distribution shows that the protein is colocalized with actin at peripheral cell extensions in individual epithelial cancer cells and in transformed fibroblastic cells. Moreover, Lasp-1 is tyrosine phosphorylated in fibroblast cell lines transformed by a constitutively active form of c-Src (c-SrcY527F). Altogether, our results show that Lasp-1 defines a new type of actin-binding protein and suggest that the protein may play a role in a signaling pathway involved in the organization of the cytoskeleton.

The pS2/TFF1 trefoil factor, from basic research to clinical applications

pS2/TFF1 trefoil factor is normally expressed in the stomach, and is found ectopically in gastrointestinal inflammatory disorders and in various carcinomas. It is involved in stomach ontogenesis and in the maintenance of the integrity of the mucosa, and may represent a pharmacological tool for prevention and healing of gastrointestinal ulcerations. In breast cancer, it can be used to select patients suitable for hormone therapy. pS2/TFF1 is a pleiotropic factor involved in mucin polymerization, cell motility, cell proliferation and/or differentiation, and possibly in the nervous system.

The estrogen responsive element of the pS2 gene is recognized by a methylation sensitive DNA binding protein

The human pS2 gene is specifically expressed is a subclass of estrogen receptor containing human breast cancer cells. In the MCF7 cell line, its induction by estradiol is a primary transcriptional event. The exact location of its estrogen responsive element has been determined using a chimeric recombinant transfected into HeLa cells and a transient expression assay. In this study we found, using electrophoretic mobility shift experiments, that in HeLa cells the estrogen responsive element (ERE) of the pS2 gene is recognized by a methylation sensitive DNA binding protein (MSDBP) different from the estrogen receptor. Competition experiments have shown that the binding of this protein requires at least one CpG in the center of the palindromic sequence and that imperfect palindromic sequences are also recognized. Although the presence of CpG is necessary, CpG-rich oligonucleotides, containing consensus sequences for Sp1 or AP2, do not interfere with its binding to the pS2 oligonucleotide, indicating that the ERE sequence itself participates in the specificity of its binding. This protein binds the pS2 sequence with a relatively high affinity (apparent Kd = 10(-10) M) and its binding is strongly reduced by the methylation of the cytosines at CpG sites. UV cross-linking experiments and peptide mapping indicate that this protein has an apparent molecular weight of 46 kDa and is present in several cell lines, including non-human cell lines. Taken together, these data suggest that this protein might have a potential role in regulating gene activity or in chromatin structure of some genes possessing an ERE.

In vivo evidence that the stromelysin-3 metalloproteinase contributes in a paracrine manner to epithelial cell malignancy

Stromelysin-3 (ST3; Basset, P., J.P. Bellocq, C. Wolf, I. Stoll, P. Hutin, J.M. Limacher, O.L. Podhajcer, M.P. Chenard, M.C. Rio, P. Chambon. 1990. Nature. 348:699-704) is a matrix metalloproteinase (MMP) expressed in mesenchymal cells located close to epithelial cells, during physiological and pathological tissue remodeling processes. In human carcinomas, high ST3 levels are associated with a poor clinical outcome, suggesting that ST3 plays a role during malignant processes. In this study we report the ST3 gene inactivation by homologous recombination. Although ST3 null mice (ST3-/-) were fertile and did not exhibit obvious alterations in appearance and behavior, the lack of ST3 altered malignant processes. Thus, the suppression of ST3 results in a decreased 7, 12-dimethylbenzanthracene-induced tumorigenesis in ST3-/- mice. Moreover, ST3-/- fibroblasts have lost the capacity to promote implantation of MCF7 human malignant epithelial cells in nude mice (P < 0.008). Finally, we show that this ST3 paracrine function requires extracellular matrix (ECM)-associated growth factors. Altogether, these findings give evidence that ST3 promotes, in a paracrine manner, homing of malignant epithelial cells, a key process for both primary tumors and metastases. Therefore, ST3 represents an appropriate target for specific MMP inhibitor(s) in future therapeutical approaches directed against the stromal compartment of human carcinomas.

Tumor necrosis factor receptor associated factor 4 (TRAF4) expression pattern during mouse development

This is the first in situ hybridization analysis of expression of a tumor necrosis factor (TNF) receptor associated factor (TRAF) during development. TRAF4 is observed throughout mouse embryogenesis, most notably during ontogenesis of the central (CNS) and peripheral (PNS) nervous system, and of nervous tissues of sensory organs. TRAF4 is preferentially expressed by post-mitotic undifferentiated neurons. Interestingly, TRAF4 remains expressed in the adult hippocampus and olfactory bulb, known to contain multipotential cells responsible for neoneurogenesis.

Chromosomal assignment and expression pattern of the murine Lasp-1 gene

The human Lasp-1 (LIM and SH3 protein) gene was previously identified by differential screening of a breast cancer-derived metastatic lymph node cDNA library. It was located on the q12-q21 region of human chromosome 17 and was shown to be amplified and overexpressed in 12% of breast tumors. Lasp-1 defines a new LIM-protein subfamily, as it associates a C-terminal Src homology 3 (SH3) domain to a N-terminal LIM motif. In this study, the isolation and characterization of the cDNA encoding the mouse Lasp-1 protein are described, and it is shown to be highly conserved with its human counterpart. In addition to the LIM and SH3 domains, both human and mouse Lasp-1 contain an actin-binding domain. The mouse gene was mapped by in situ hybridization to the 11C-11D region of chromosome 11. Northern blot analysis shows that this gene is expressed from 7.5 to 17.5 days post-coitum of mouse embryogenesis and in almost all adult tissues.

MLN64 contains a domain with homology to the steroidogenic acute regulatory protein (StAR) that stimulates steroidogenesis

MLN64 is a protein that is highly expressed in certain breast carcinomas. The C terminus of MLN64 shares significant homology with the steroidogenic acute regulatory protein (StAR), which plays a key role in steroid hormone biosynthesis by enhancing the intramitochondrial translocation of cholesterol to the cholesterol side-chain cleavage enzyme. We tested the ability of MLN64 to stimulate steroidogenesis by using COS-1 cells cotransfected with plasmids expressing the human cholesterol side-chain cleavage enzyme system and wild-type and mutant MLN64 proteins. Wild-type MLN64 increased pregnenolone secretion in this system 2-fold. The steroidogenic activity of MLN64 was found to reside in the C terminus of the protein, because constructs from which the C-terminal StAR homology domain was deleted had no steroidogenic activity. In contrast, removal of N-terminal sequences increased MLN64's steroidogenesis-enhancing activity. MLN64 mRNA was found in many human tissues, including the placenta and brain, which synthesize steroid hormones but do not express StAR. Western blot analysis revealed the presence of lower molecular weight immunoreactive MLN64 species that contain the C-terminal sequences in human tissues. Homologs of both MLN64 and StAR were identified in Caenorhabditis elegans, indicating that the two proteins are ancient. Mutations that inactivate StAR were correlated with amino acid residues that are identical or similar among StAR and MLN64, indicating that conserved motifs are important for steroidogenic activity. We conclude that MLN64 stimulates steroidogenesis by virtue of its homology to StAR.

MLN64 exhibits homology with the steroidogenic acute regulatory protein (STAR) and is over-expressed in human breast carcinomas

The MLN64 gene, which is localized in q12-q21 of the human chromosome 17, encodes a novel protein containing 2 distinct domains. At the N-terminal, MLN64 exhibits a potential trans-membrane region, while at the C-terminal, it shares homology with the F26F4.4 protein of Coenorhabditis elegans and the steroidogenic acute regulatory (StAR) protein, a mitochondrial protein which is involved in steroid-hormone synthesis. By comparing the C-terminal part of these proteins, we defined a novel protein domain, which we termed SHD for "StAR Homology Domain". Of the 93 primary invasive breast carcinomas that were examined, 14 were found to over-express MLN64. These 14 tumors also expressed high c-erbB-2 transcript levels, which were not detected in the MLN64-negative tumors. MLN64 mRNA and protein were specifically detected in malignant cells of breast carcinomas. MLN64 protein was localized within bundle-like structures distributed throughout the cell cytoplasm and condensed in a perinuclear patch, suggesting an association with a specific cell compartment. When the N-terminal part of MLN64 was deleted, MLN64 was uniformly distributed in the cell cytoplasm, indicating that N-terminal part is involved in the specific cytoplasmic localization of MLN64. The homology between the C-terminal part of MLN64 and the functional StAR domain (SHD) suggests that MLN64 and StAR, although distributed in different cellular compartments, may both play a role in steroidogenesis. In this case, the high levels of MLN64 observed in some breast carcinomas could contribute to the progression of these tumors through increased intratumoral steroidogenesis.

Rolling in the clover: trefoil factor family (TFF)-domain peptides, cell migration and cancer

Trefoil factor family (TFF)-domain peptides 1-3 are mucin-associated molecules, largely found in epithelia of gastrointestinal tissues. Structurally similar, resistant to enzymatic degradation, they are up-regulated around areas of epithelial damage such as ulcers. Transgenic expression or exogenous peptide ameliorates or prevents gastric mucosal damage due to indomethacin and some are rapidly up-regulated after cryogenic burns. A role in promoting cell migration is strongly suggested. Knockout mice lacking TFF1 or TFF3 show significant pathology, with the former developing gastric tumours. A recent Conference Philippe Laudat agreed upon a new nomenclature for these peptides.

MLN64 exhibits homology with the steroidogenic acute regulatory protein (STAR) and is over-expressed in human breast carcinomas

The MLN64 gene, which is localized in q12-q21 of the human chromosome 17, encodes a novel protein containing 2 distinct domains. At the N-terminal, MLN64 exhibits a potential trans-membrane region, while at the C-terminal, it shares homology with the F26F4.4 protein of Coenorhabditis elegans and the steroidogenic acute regulatory (StAR) protein, a mitochondrial protein which is involved in steroid-hormone synthesis. By comparing the C-terminal part of these proteins, we defined a novel protein domain, which we termed SHD for "StAR Homology Domain". Of the 93 primary invasive breast carcinomas that were examined, 14 were found to over-express MLN64. These 14 tumors also expressed high c-erbB-2 transcript levels, which were not detected in the MLN64-negative tumors. MLN64 mRNA and protein were specifically detected in malignant cells of breast carcinomas. MLN64 protein was localized within bundle-like structures distributed throughout the cell cytoplasm and condensed in a perinuclear patch, suggesting an association with a specific cell compartment. When the N-terminal part of MLN64 was deleted, MLN64 was uniformly distributed in the cell cytoplasm, indicating that N-terminal part is involved in the specific cytoplasmic localization of MLN64. The homology between the C-terminal part of MLN64 and the functional StAR domain (SHD) suggests that MLN64 and StAR, although distributed in different cellular compartments, may both play a role in steroidogenesis. In this case, the high levels of MLN64 observed in some breast carcinomas could contribute to the progression of these tumors through increased intratumoral steroidogenesis.

Expression of matrix metalloproteinases during rat skin wound healing: evidence that membrane type-1 matrix metalloproteinase is a stromal activator of pro-gelatinase A

Skin wound healing depends on cell migration and extracellular matrix remodeling. Both processes, which are necessary for reepithelization and restoration of the underlying connective tissue, are believed to involve the action of extracellular proteinases. We screened cDNA libraries and we found that six matrix metalloproteinase genes were highly expressed during rat skin wound healing. They were namely those of stromelysin 1, stromelysin 3, collagenase 3, gelatinase A (GelA), gelatinase B, and membrane type-1 matrix metalloproteinase (MT1-MMP). The expression kinetics of these MMP genes, the tissue distribution of their transcripts, the results of cotransfection experiments in COS-1 cells, and zymographic analyses performed using microdissected rat wound tissues support the possibility that during cutaneous wound healing pro-GelA and pro-gelatinase B are activated by MT1-MMP and stromelysin 1, respectively. Since MT1-MMP has been demonstrated to be a membrane-associated protein (Sato, H., T. Takino, Y. Okada, J. Cao, A. Shinagawa, E. Yamamoto, and M. Seiki. 1994. Nature (Lond.). 370: 61-65), our finding that GelA and MT1-MMP transcripts were expressed in stromal cells exhibiting a similar tissue distribution suggests that MT1-MMP activates pro-GelA at the stromal cell surface. This possibility is further supported by our observation that the processing of pro-GelA to its mature form correlated to the detection of MT1-MMP in cell membranes of rat fibroblasts expressing the MT1-MMP and GelA genes. These observations, together with the detection of high levels of the mature GelA form in the granulation tissue but not in the regenerating epidermis, suggest that MT1-MMP and GelA contribute to the restoration of connective tissue during rat skin wound healing.

Expression pattern of human hair keratin basic 1 (hHb1) in hair follicle and pilomatricoma

Using in situ hybridization, human hair keratin basic 1 (hHb1) gene expression was investigated in human normal scalp. hHb1 transcripts were specifically detected in the cortical cells of hair shaft but neither in the outer and inner root sheaths, nor in the hair cuticle or the medulla. hHb1 expression was detected strongly in cortical cells located from the beginning of the keratogenous zone up to the isthmus. These data specify the localization of hHb1 expression. Furthermore, neoplasms with follicular differentiation, including trichoblastoma, trichoepithelioma, pilomatricoma, pilar carcinoma and basal-cell carcinoma, were analysed for hHb1 gene expression. One of the 4 pilomatricoma specimens examined exhibited a very high level of hHb1 transcripts. Interestingly, this labeling was specifically associated to a transitional cell layer en route to trichocytic differentiation, providing evidence that in pilomatricoma, epithelial germ cells can differentiate towards hair shaft keratinocytes before evolving in ghost cells.

[What is/are the function(s) of trefoil peptides?]

pS2, SP and ITF have been identified in the eighties. These peptides share a consensus proteic domain including 3 disulfide bridges leading to a 3 loop structure and subsequently to their name of trefoil peptides. While they are normally expressed in restricted parts of the gastrointestinal tract, ectopic expression is also observed during gastrointestinal ulcerations and in various carcinomas. To date, from numerous studies performed in vitro and in vivo, their functions in these pathologies begin to be elucidated.

Involvement of DNA methylation in the control of the expression of an estrogen-induced breast-cancer-associated protein (pS2) in human breast cancers

pS2 gene has been used to investigate the relationship between alterations of DNA methylation patterns in human tumors and gene expression. The expression of pS2, which is transcriptionally controlled by estrogens in breast cancer cell lines, is restricted to estrogen-receptor-rich human breast tumors. We found that the CCGG site within the promoter/enhancer sequence of pS2 was hypomethylated in estrogen-receptor-rich breast tumors expressing this gene. The amount of DNA molecules unmethylated at this site was related to the amount of pS2 mRNA detected in the samples. The demethylation of this region, which contains the estrogen responsive element, was confirmed by genomic sequencing. Transient expression of functional human estrogen receptors stimulated the expression of the endogenous pS2 in HeLa cells, but failed, in BT-20 cells, to stimulate expression of this gene. Since the promoter/enhancer region of pS2 is unmethylated in HeLa cells and methylated in BT-20 cells, these data also support the hypothesis that DNA methylation might be involved in the control of pS2 expression.

Matrix metalloproteinases as stromal effectors of human carcinoma progression: therapeutic implications

The matrix metalloproteinases (MMPs) are extracellular zinc-enzymes implicated in a number of physiological and pathological tissue remodeling processes, including cancer progression. For a long time they have been thought to be produced by malignant cells and to specifically contribute to tumor invasion, through their ability to degrade extracellular matrix components. However, studies performed over the last few years have demonstrated that extracellular proteinases implicated in the progression of human carcinomas, including most MMPs, are in fact predominantly expressed by stromal and not by cancer cells. Furthermore, membrane receptors, activators and/or binding sites for some of these proteinases are also predominantly found to be associated with stromal cells. These findings, together with the observation that MMPs can cleave some molecules implicated in controlling growth factor activities, suggest that the role of MMPs during cancer progression is not limited to facilitating malignant cell invasion alone but is also likely to participate in other aspects of the malignant phenotype. MMPs should in fact be regarded as pan-regulators of tissue neoformation characteristic of malignant tumors, which includes both epithelial cell expansion and stroma formation. In this context, synthetic MMP inhibitors which are presently designed should lead to the development of a new generation of anticancer agents with additional beneficial properties compared to the existing cytotoxic agents used in the treatment of human malignancies.

Gastric mucosa abnormalities and tumorigenesis in mice lacking the pS2 trefoil protein

To determine the function of the pS2 trefoil protein, which is normally expressed in the gastric mucosa, the mouse pS2 (mpS2) gene was inactivated. The antral and pyloric gastric mucosa of mpS2-null mice was dysfunctional and exhibited severe hyperplasia and dysplasia. All homozygous mutant mice developed antropyloric adenoma, and 30 percent developed multifocal intraepithelial or intramucosal carcinomas. The small intestine was characterized by enlarged villi and an abnormal infiltrate of lymphoid cells. These results indicate that mpS2 is essential for normal differentiation of the antral and pyloric gastric mucosa and may function as a gastric-specific tumor suppressor gene.

Two distinct amplified regions at 17q11-q21 involved in human primary breast cancer

Chromosomal segment 17q11-q21 is a commonly amplified region in human breast carcinomas. Several lines of evidence suggest that ERBB2 is the gene responsible for the emergence of this amplicon, but four novel genes (called MLN 50, MLN 51, MLN 62, and MLN 64) in 17q11-q21 have recently been found to be amplified and overexpressed in breast cancer cell lines. We investigated 98 primary breast tumors for amplification of these five loci. Twenty-five tumors (25.5%) showed amplification of at least one of these markers, but most amplifications did not encompass all of the tested loci. The genes most frequently amplified were ERBB2 and MLN 64 (22 of 25 amplified cases). MLN 64 was always coamplified with ERBB2, and to a similar level. Amplification of these five genes always leads to overexpression of their mRNA; we observed no cases of overexpression without amplification in any of these genes. Our results suggest that: (a) an independent, amplified region defined by MLN 62 (also called CART1 or TRAF4) is located in 17q11-q12; (b) in addition to ERBB2, MLN 64 is a major target for the 17q12-q21 amplicon; and (c) these MLN genes could be of pathogenetic significance in breast cancer.

Stromelysin-3 expression promotes tumor take in nude mice

Stromelysin-3 (ST3) is a matrix metalloproteinase expressed in human carcinomas in ways suggesting that it may play a role in tumor progression. To test this possibility, we have performed gene transfer experiments using both anti-sense and sense ST3 expression vectors, and malignant cells either expressing (NIH 3T3 fibroblasts) or not (MCF7 epithelial cells) endogenous ST3. We have compared the ability of parental and transfected cells to cause subcutaneous tumor development in nude mice. 3T3 cells expressing anti-sense ST3 RNA showed reduced tumorigenicity, and MCF7 cells expressing mouse or human ST3 were associated with reduced tumor-free period leading to a significant increased tumor incidence(P<10(-4)). However, once established, the ST3 expressing tumors did not grow faster than those obtained with the parental MCF7 cell line. In addition, tumors obtained after sub-cutaneous injection of ST3-expressing or nonexpressing cells did not exhibit obvious histological differences, and careful examination did not reveal any local invasive tissue areas nor systemic metastases. These in vivo observations were in agreement with those obtained in vitro showing that ST3 expression did not modify proliferative nor invasive properties of transfected cells. Altogether, these results indicate that ST3 expression promotes tumor take in nude mice, presumably by favoring cancer cell survival in a tissue environment initially not permissive for tumor growth. These findings represent the first experimental evidence showing that ST3 can modulate cancer progression.

Stromelysin-3 in the biology of the normal and neoplastic mammary gland

Stromelysin-3 (ST3) is an extracellular proteinase predominantly expressed in fibroblasts. The particular structural features and in vitro functions of this molecule suggest it could be the first member of a new subgroup of the matrix metalloproteinase family. ST3 is transiently expressed during mammary gland post-weaning involution, embryonic implantation, various organogeneses, and during amphibian metamorphosis. Moreover, ST3 is expressed in a panel of human invasive carcinomas including breast, colon, and head and neck carcinomas. Almost all ST3-expressing tissues show intense extracellular matrix remodeling activities including the loss of basement membrane integrity. Thus, either directly, or indirectly in association with other proteinases, ST3 might be involved in tissue remodeling processes occurring in both physiological and pathological processes. In vitro and in vivo studies using malignant cells stably transfected in such a way as to modulate their ST3 expression levels indicate that ST3 modifies neither cell proliferation nor invasive properties, but rather favors tumor cell survival in host tissues. This hypothesis is consistent with clinical data showing that ST3 expression could be predictive of tumor progression leading to metastases.