WO2006005361A1

WO2006005361A1 - Peptides liable to bind to the tie2 receptor, nucleic acids encoding them, and their uses

Info

Publication number: WO2006005361A1
Application number: PCT/EP2004/007722
Authority: WO
Inventors: Roselyne-Lucile Tournaire-Binetruy; Jaques Pouyssegur
Original assignee: Centre National De La Recherche Scientifique
Priority date: 2004-07-13
Filing date: 2004-07-13
Publication date: 2006-01-19

Abstract

The present invention relates to the use of a 7-mer peptide library for the screening of peptides liable to bind to the Tie2 receptor, said peptides having agonist or antagonist properties with respect to the Tie2 receptor.

Description

PEPTIDES LIABLE TO BIND TO THE TIE2 RECEPTOR, NUCLEIC ACIDS ENCODING THEM, AND THEIR USES

The present invention relates to peptides liable to bind to the Tie2 receptor, to nucleic acids encoding them, and to the uses of said peptides.

Angiogenesis, the formation of new blood vessels sprouting from pre-existing vasculature, is required for embryonic development, for several female reproductive functions, and for wound healing and other repair processes. Angiogenesis also occurs in several diseases, and its importance in solid tumor growth and metastasis has been demonstrated in multiple studies (reviewed in Carmeliet, 2003). The generation of new capillaries and their remodeling involve a multistep process, which includes the destabilization of established vessels, endothelial cell migration and proliferation, and the formation of new vascular tubes, which are stabilized by mesenchymal components. Blocking any one of these steps would inhibit the formation of new vessels, and therefore affect tumor growth and generation of metastases. Indeed, fibroblast growth factor 2 (FGF-2), an angiogenic factor, has profound effects on endothelial cells, but also on many other cell types on which its receptors are expressed. Until recently, the most studied growth factor proved to be specific and critical for blood vessel formation was vascular endothelial growth factor (VEGF). The angiopoietins/Tie2 receptor pathway has been recently identified as another endothelial cell-specific proangiogenic system, which plays a critical part in promoting vascular homeostasis and vessel maturation, as well as vascular destabilization and remodeling (Sato et al, 1995). The Tie2 tyrosine kinase receptor is expressed specifically on endothelial cells (Dumont et al, 1992 ; Suri et al, 1996). The interruption of Tie2 signaling with soluble, dominant-negative receptors can significantly inhibit tumor growth in mice (Lin et al, 1997 ; Siesmeister et al., 1999). For instance, an Angl-antisense RNA approach reduces tumor growth and tumor angiogenesis (Schim et al, 2001). Recently, a nuclease- resistant RNA aptamer that binds Ang2, has been reported to inhibit both Ang2 signaling and FGF-2 angiogenesis (White et al, 2003). Angl acts as an agonist of Tie2 (Davis et al, 1996), whereas Ang2 appears to be a context-dependent antagonist/agonist (Maisonpierre et al, 1997 ; Mochizuki et al, 2002). Targeted disruption of Angl and Tie2-coding genes and overexpression of Ang2 results in embryonic death with similar vascular defects (Dumont et al, 1994 ; Sato et al, 1995 ; Suri et al, 1996 ; Maisonpierre et al, 1997 ). Angl is involved in normal interactions between endothelial cells and their underlying supporting pericytes, as well as in the maintenance of vascular stability. In vitro studies have demonstrated that Angl induces endothelial cell migration (Witzenbichler et al, 1998), sprouting and formation of tubule-like vascular structures (Papapetropoulos et al, 1999). Furthermore, it protects endothelial cells from - apoptosis (Papapetropoulos et al, 2000). The recent Ang2 gene knockout mouse model has

-_v demonstrated that Ang2 is required for subsequent angiogenic remodeling and seems to act as a Tie2 agonist in the lymphatic system (Gale et al, 2002).

Wu et al. (2004) describe a 22-residue long peptide derived from Ang2 which binds to

Tie2. However, no information is presented on the properties of this peptide as an agonist or antagonist of the Tie2 receptor. In particular, the impact of this peptide on angiogenesis is not assessed. Besides, the fact that this peptide derives from Ang2 makes it difficult to characterize its agonist or antagonist properties with respect to Tie2, since Ang2 seems to possess both properties depending on the context. Furthermore, the administration of such a peptide to a patient could lead to the production of antibodies directed against the peptide, but also against Ang2, from which it derives. Those auto-antibodies could have a major negative effect on said patient's health, since they would impair the normal balance between pro- angiogenic factors and anti-angiogenic factors.

Thus, an object of the invention is to provide new peptides which bind to Tie2, the antagonist or agonist properties of which with respect to the Tie2 receptor are well characterized, the sequences of said peptides presenting essentially no homology with the sequences of the natural ligands of Tie2.

Another object of the invention is to provide the nucleic acid sequences encoding said peptides.

Still another object of the invention is to provide pharmaceutical compositions comprising said peptides.

The Tie2 receptor is an endothelial-specific receptor tyrosine kinase, it is in particular described by Jones et al. (2001) and Sato et al. (2001).

By "7-mer peptide library" is meant a collection of 7 residues long peptides, and in particular a collection wherein all the 7 residues long peptides are present {i.e. the 7²⁰ possible peptides). The binding of a peptide belonging to a phage Ml 3 peptide library to the Tie2 receptor can be detected for instance by ELISA as follows:

96-well microtiter plates are coated with the extracellular domain of the Tie2 receptor linked to the immunoglobulin domain Fc or with Fc alone at 4 μg/ml and. incubated overnight at 4°C. ^* Wells are blocked with 0.5% bovine serum albumin. Phage particles (10¹² particles/ml) are added to each well and incubated 1 h at room temperature. Wells are washed 15 times with 0.1% Tween 20 in PBS and the amount of bound phage is detected with peroxidase- conjugated anti-M13 phage antibody. To quantify only the binding to Tie2, the signal measured on an Fc-coated surface is subtracted. Non-displaying Ml 3 phage particles can be used as negative controls.

Agonist or antagonist properties of peptides with respect to the Tie2 receptor can be detected by evaluating the MAP kinase (MAPK), or the Tie receptor, phosphorylation status of cells contacted with said peptides.

A peptide is said to have agonist properties with respect to the Tie2 receptor if it is liable to promote the phosphorylation of p42/p44 MAPK, or of the Tie2 receptor, in cells expressing Tie2.

A peptide is said to have antagonist properties with respect to the Tie2 receptor if it is liable to inhibit the phosphorylation of p42/p44 MAPK, or of the Tie2 receptor, induced by Angl in cells expressing Tie2. Such agonist or antagonist properties can inj particular be evaluated as follows:

HUVECs (Human Umbilical Vein Endothelial Cells) are serum-starved for 16 h, trypsinized, and replated. After 6 h, cells are incubated for 1 h with a peptide to be evaluated, and optionally stimulated for 10 mn with Angl (300 ng/ml). Cells are then lysed in Laemmli buffer. Proteins are separated on a SDS-PAGE (7.5%), and electrόphoretically transferred onto polyvinylidone difluoride membrane. Membranes are probed with an anti-phospho ρ42/p44 MAPK monoclonal antibody or an anti-p42 MAP Kinase antibody. The immunoreactive bands are visualised with ECL system, and the relative quantities of phosphorylated p42/p44 MAPK (determination of an agonist) and unphosphorylated p42/p44 MAPK (determination of an antagonist) are evaluated. Peptides having agonist properties with respect to the Tie2 receptor are useful in particular to promote neovascularisation or vessel growth, in vitro or in vivo. Therapeutic applications include healing promotion, tissue reconstruction, ovarian induction, or reperfusion of ischemic areas. Peptides having antagonist properties with respect to the Tie2 receptor are useful in particular for the inhibition of angiogenesis, more particularly for the inhibition of endothelial growth and/or proliferation. Therapeutic applications include tumor treatment, age related macular degeneration, diabetic retinopathy, rheumatoid arthritis, allograft or xenograft rejection, acrocyanosis, or sclerodermia.

According to a particular embodiment, the present invention relates to the above defined use of a 7-mer peptide library, for screening peptides liable:

- to inhibit the binding of angiopoetins to the Tie2 receptor,

- to favour the binding of angiopoetins to the Tie2 receptor, or - to mimic the binding of angiopoetins to the Tie2 receptor.

Angiopoietins are proteins which share similar structural features and bind to the Tie2 receptor, such as Angl and Ang2 for example.

The capacity of peptides to inhibit or to favour the binding of angiopoietins to the Tie2 receptor can be evaluated through competitive binding experiments. Such experiments can be carried out by using surface plasmon resonance, a method well known to the man skilled in the art, as described in Example 2.

The capacity of peptides to mimic the binding of angiopoietins to the Tie2 receptor can be evaluated by comparing the MAPK phosphorylation status of Tie2 expressing cells contacted with the peptides, with that of Tie2 expressing cells contacted with angiopoietins. In particular, the MAPK phosphorylation status of Tie2 expressing cells can be determined as described above.

Alternatively, the capacity of peptides to mimic the binding of angiopoietins to the Tie2 receptor can be evaluated by comparing the Tie2 receptor phosphorylation status of Tie2 expressing cells contacted with the peptides, with that of Tie2 expressing cells contacted with angiopoietins.

According to another particular, the present invention relates to the above defined use of a 7-mer peptide library, for screening peptides liable:

- to inhibit the binding of Angl to the Tie2 receptor,

- to favour the binding of Angl to the Tie2 receptor, or - to mimic the binding of Angl to the Tie2 receptor.

According to still another particular, the present invention relates to the above defined use of a 7-mer peptide library, for screening peptides liable:

- to inhibit the binding of Ang2 to the Tie2 receptor,

- to favour the binding of Ang2 to the Tie2 receptor, or - to mimic the binding of Ang2 to the Tie2 receptor.

In a preferred embodiment, the invention relates to the above defined use of a 7-mer peptide library, for screening peptides liable to inhibit both the binding of Angl and Ang2 to the Tie2 receptor. ' The present invention also relates to a process for screening a 7-mer peptide liable to

-„ inhibit the binding of angiopoetins to the Tie2 receptor, comprising:

- a step of contacting 7-mer peptides with the extracellular domain of the Tie2 receptor and recovering the peptides which bind thereto,

- selecting among the peptides recovered at the preceding step, the peptides which inhibit the binding of Ang 1 and/or of Ang2 to the Tie2 receptor.

In a preferred embodiment of the invention, the above defined process for screening a 7-mer peptide liable to inhibit the binding of angiopoetins to the Tie2 receptor comprises an additional step of selecting among the peptides selected at the preceding stage, the peptides which inhibit - Angl and/or Ang2 induced signal transduction, and/or

- endothelial cell migration.

Angl and/or Ang2 induced signal transduction can be assessed by measuring the quantity of phosphorylated p42/p44 MAP kinases in cells carrying Tie2 receptors activated by Angl and/or Ang2 (Kim et al, 2002 ; Harfouche et ah, 2003). Endothelial cell migration can be assessed by counting the number of migrating endothelial cells, such as human umbilical vein endothelial cells, as described in Witzenbichler etf α/., 1998.

The present invention also relates to a peptide liable to bind to the Tie2 receptor, said peptide having agonist or antagonist properties with respect to the Tie2 receptor, the sequence of said peptide presenting less than about 20% sequence identity with the amino acid sequences of Angl and Ang2.

The sequence identity between the peptides of the invention and Angl or Ang2 can be performed by using alignment algorithms or softwares well kown to the man skilled in the art, such as the MULTALIGN software (Chimera, U.S.A.).

According to a preferred embodiment of the above defined peptide liable to bind to the Tie2 receptor, the sequence of said peptide presents essentially no sequence identity with the amino acid sequences of Angl and Ang2. By "essentially no sequence identity" is meant that no significant alignment between the sequences of the peptides according to the invention and the sequences of Angl or Ang2 can be performed, i.e. only 3 contiguous amino acids for Ang2 and 2 contiguous amino acids for Angl can be aligned at maximum. According to another preferred embodiment of the above defined peptide liable to bind to the Tie2 receptor, said peptide has a length of about 5 to 15^' amino acids, in particular of about 7 amino acids.

According to a particularly preferred embodiment of the above defined peptide liable to bind to the Tie2 receptor, said peptide is selected from the group consisting of T4 (NLLMAAS, SEQ ID NO: 2),

T6 (KLWVIPK, SEQ ID NO: 4),

T7 (HHHRHSF, SEQ ID NO: 6) and

T8 (HPWLTRH, SEQ ID NO: 8), or a peptide derived from T4, T6, T7 or T8 by substitution, deletion or insertion of one or several amino acids, provided that said derived peptide is liable to bind to the Tie2 receptor. hi a most preferred embodiment of the above defined peptide liable to bind to the Tie2 receptor, said peptide corresponds to T4, or a peptide derived from T4 by substitution, deletion or insertion of one or several amino acids, provided that said derived peptide is liable to bind to the Tie2 receptor, to inhibit the binding of both Angl and Ang2 to the Tie2 receptor, and to inhibit the signal transduction and the migration of endothelial cells mediated by the Tie2 receptor.

T4 inhibits the binding of both Angl and Ang2 to the Tie2 receptor and inhibits the signal transduction and the migration of endothelial cells mediated by the Tie2 receptor.

Furthermore T4 is a potent inhibitor of angiogenesis in vivo. \ Advantageously, T4 is a 7-residue long peptide, which makes it a desirable peptidic drug, since small peptides are usually more stable in biological media than larger peptides.

Furthermore, small peptides can be obtained with a high yield and a high purity by chemical synthesis.

The invention also encompasses modifications which can be brought to peptides to render them more active and/or more resistant to degradation. Such modifications are well known to the man skilled in the art and comprise, in particular, the use of one or more D- amino-acids for the synthesis of the peptides, or alternatively the synthesis of the corresponding retro-inverso or cyclic peptides. Such modifications enhance the resistance of the peptides to degradation and thus greatly improve their activity. Furthermore, modifications such as the addition of a gallic acid moiety at the N-terminus of the peptides can also be used to boost the activity of said peptides (Appeldoorn et al., 2003).

The present invention also relates to a nucleic acid coding for T4, T6, T7 or T8, and in particular a nucleic acid of sequence ^: AATCTGCTTATGGCGGCGTCT (SEQ E) NO: 1), _; AAGCTGTGGGTGATTCCTAAG (SEQ ID NOI S), CATCATCATAGGCATT^'CGTTT (SEQ E) NO: 5), or CATCCTTGGCTTACTCGTCAT (SEQ E) NO: 7).

The invention also relates to a recombinant vector comprising a nucleic acid as defined above, in particular a recombinant vector selected from a bacterial expression vector, a yeast expression vector, a mammalian expression vector or a viral expression vector.

Such a vector is particularly useful to direct a biological production of the peptide by bacterial, yeast or mammalian cells. Alternatively, the peptide can be chemically synthesised. Chemical synthesis is advantageous since it limits potential biological contamination of the peptides as compared to biological methods of production. Besides, chemical synthesis avoids the cumbersome purification steps which are required in biological production methods. The peptides according to the invention are particularly well fitted for chemical synthesis since they are short (7 amino acids long), which ensures high production yields and a high purity.

The invention also relates to prokaryotic or eukaryotic cells transformed with a nucleic acid as defined above and/or a recombinant vector as defined above.

Such cells can be used to produce the peptides of the invention. In the case of mammalian cells, in particular human cells, they could be grafted or administered to a host to produce peptides according the invention in vivo.

The present invention also relates to a pharmaceutical composition comprising as active substance at least one peptide as defined above, in particular T4, in association with a pharmaceutically acceptable carrier.

In a preferred embodiment, the above defined pharmaceutical composition is suitable for the administration of a unit dose of about 1 to 100 mg/kg/day, in particular of about 10 mg/kg/day of the peptide according to claim 11 or 12. The present invention also relates to the use of a peptide as defined above, for the manufacture of a medicament useful for

- the treatment of pathologies requiring the inhibition of endothelial proliferation, such as tumors, in particular angiomas or angiosarcomas, age related macular degeneration, diabetic retinopathy, or rheumatoid arthritis, and/or - the treatment of pathologies requiring the inhibition of endothelial activation, such as allograft or xenograft rejection, acrocyanosis, sclerodermia, in particular psoriasis, or

- promoting healing, in particular wound healing, tissue reconstruction, in particular for muscle and skin grafts in plastic surgery, ovarian induction, reperfusion of ischemic areas in - case of arteritis of the lower limbs or of myocardial infarction, and/or -„ - preparing transplant grafts before implantation.

According to a preferred embodiment of the above defined use, the invention relates to the use of T4, for the manufacture of a medicament useful for

- the treatment of pathologies requiring the inhibition of endothelial proliferation, such as tumors, in particular angiomas or angiosarcomas, age related macular degeneration, diabetic retinopathy, or rheumatoid arthritis, and/or

- the treatment of pathologies requiring the inhibition of endothelial activation, such as allograft or xenograft rejection, acrocyanosis, sclerodermia, in particular psoriasis.

In another aspect, the invention also relates to the use of the above defined peptides to target vasculature tissues or cells.

In one particular embodiment, peptides as defined above are coupled to markers, such as fluorescent or radioactive markers, to be used for the detection of vasculature tissues or cells in imaging methods.

In another particular embodiment, peptides as defined above are coupled to cytolytic compounds, such as compounds selected from granzymes, toxins, radioactive isotopes, or TNF, so as to selectively target and destroy vasculature cells, in particular vasculature cells of tumor vessels.

DESCRIPTION OF THE FIGURES

Figure 1

Figure 1 represents the binding of selected phage-displayed peptides (Tl-Tl 1, horizontal axis) to Tie2. The binding of clones was analysed by ELISA (Absorbance at 490 nm, vertical axis), and was compared to that of wild type Ml 3 phage particles as control (wt phage). Results are representative of three independent assays. The star (*) represents PO.05 versus control.

Figure 2A and Figure 2B Figure 2 A represents the percentage of Tie2-Fc bound Ang2 as measured by ELISA (vertical axis, % of control) in the presence of the Tl, T4, T6, T7, T8 and TlO peptides (horizontal axis). As a positive control, Tie2s was tested in the same conditions.

Figure 2B represents the inhibition of Angl (black bars) or Ang2 (white bars) binding to Tie2-Fc (vertical axis, %) as measured by ELISA, in the presence of increasing concentrations of peptide T4 (horizontal axis, mM)..

Data represent the mean and standard deviations of triplicates. Similar results were obtained in three independent different experiments. The star (*) represents PO.05 versus control.

Figure 3A and Figure 3B Figures 3A-3B represent the results of competition assays between Angl (Figure 3A) or Ang2

(Figure 3B) and T4 or T7 for the binding to Tie2 as measured by the Biacore test. The vertical axes represent the association rate measured for each peptide concentration divided by that obtained in the absence of peptide (%), and the horizontal axes the concentration of T4 (bold lines) or T7 (thin lines) in mol/1 (M).

Figure 4A, Figure 4B and Figure 4C

Figures 4A-4C represent Western blots of HUVECs hydrolysates revealed by anti-p42 MAPK antibodies or anti-phosphorylated p42/p44 MAPK (pp42, pp44).

In Figure 4A HUVECs were stimulated with Angl with or without Tie2s. In Figure 4B HUVECs were stimulated with Angl in the absence (control) or presence of various concentrations of either peptide T4 (0 ; 0.125 ; 0.25 ; 0.5 and ImM) or T7 (1 mM).

The band at 45 represents a molecular weight control (in kD).

In Figure 4C HUVECs were stimulated with Angl or FGF-2 in the absence (control) or presence of peptide T4 (ImM). Similar results were obtained in two different experiments.

Figure 5A, Figure 5B

Figure 5A represents pictures of HUVECs cultures allowed to migrate in the presence or absence of Angl or VEGF, with or without peptide T4 (1 mM), an untreated control is also presented.

Figure 5B represents the migration score (migrated cells, vertical axis) for control HUVECs cultures, and Angl, Angl+T4, VEGF, or VEGF+T4 treated HUVECs (horizontal axis). Score means and standard errors were measured for three fields. Similar results were obtained in two different experiments. The star (*) represents scores for which PO.05 versus control. NS : Non Significant.

Figure 6A, Figure 6B, Figure 6C and Figure 6D

Figures 6a-6D represents a picture of the network of blood vessels formed in chick embryos treated by PBS (Figure 6A), the T7 peptide (Figure 6B), or the T4 peptide (Figures 6C-6D). Bars : lmm in upper and lower panels.

EXAMPLES

Materials

Human recombinant Angl, Ang2, biotinylated Ang2, Tie2-Fc, Tiel-Fc and TrkB-Fc - were purchased from R&D Systems, whereas recombinant human FGF-2 was produced in - Escherichia coli. VEGF₁₆₅ was obtained from Sigma. The Fc fragment of human IgG was from Jackson ImmunoResearch. Peptides were synthesized by Eurogentec.

Example 1: peptide selection hi order to select peptides binding Tie2, a random 7-mer M 13 phage-display library was screened for binding to Tie2-Fc. Biopanning was adapted from the Ph.D.-7 kit standard procedure (New England Biolabs) and described previously (Binetray-Tournaire et al, 2000). Tie2-Fc was used to coat microtiter plates at 10 μg/ml.

At the end of the selection, 48 clones were isolated and sequenced, showing that 11 different peptides were represented (Tl to Tl 1).

DNA sequences were determined by DNA and amino acid sequence analysis with a A310 sequencer using the ABI PRISM dye terminators (P.E. Biosystems). Alignment between the peptide sequence and the Angl or Ang2 primary sequence was determined using the MULTALIGN software. Each selected clone was assayed by ELISA for binding to Tie2-Fc. Briefly, the ELISA assays were carried out as follows: 96-well plates (Maxisorp, Nunc International) were coated with Tie2-Fc or Fc at 4 μg/ml and incubated overnight at 4°C. Wells were blocked with 0.5% bovine serum albumin. Phage particles (10¹² particles/ml) were added to each well and incubated 1 h at room temperature. Wells were washed 15 times with 0.1% Tween 20 in PBS and the amount of bound phage was detected with peroxidase-conjugated anti-M13 phage antibody (Amersham Pharmacia Biotech). hi order to quantify only the binding to Tie2, the signal measured on an Fc-coated surface was subtracted. Non-displaying Ml 3 phage particles were used as negative controls (Figure 1). All the tested clones gave a significant ELISA signal, demonstrating specific binding to Tie2. Clones T4, T6, T7 and T8 that gave the highest signal were chosen for further experiments.

Table I shows that only T7 and T8 share a sequence homology, with two identical residues: RH. Table I. Multiple alignment of selected clones.

Consensus motif No consensus motif

T7 HHHRHSF T4 NLLMAAS

T 8 HPWLTRH T6 KLWVIPK

Six synthetic peptides Tl, T4, T6, T7, T8 and TlO (Tl and TlO as negative controls) were then produced and their ability to compete with Ang2 for binding to Tie2 was tested by ELISA, using a fixed peptide concentration (500 μM). _s

For competition assays, biotinylated Ang2 or Angl (200 ng/ml) was added and incubated for 2 h at room temperature. Bound Ang2 was detected with HRP-conjugated streptavidin (Zymed) using 1,2-phenylenediamine dihydrochloride (OPD tablets, DAKO). Bound Angl was detected with anti-human Angl polyclonal antibody (Santa Cruz Biotechnology) followed by HRP-conjugated anti-goat IgG antibody (DAKO). Tie2s (Tie2- Fc ; 30 μg/ml), anti-Tie2 antibody (20 μg/ml ; R&D Systems) or peptides were co-incubated with Angl or Ang2.

It had been verified beforehand that recombinant Ang2 and Angl specifically bound to Tie2-Fc but not to TrkB-Fc, Tiel-Fc or Fc. Results show that only peptide T4 inhibited Ang2 binding (Figure 2A). The other peptides did not inhibit Ang2 or Angl binding to Tie2 even when the peptide concentration was increased to 2 mM. T4 abolished Ang2 and Angl binding to Tie2 in a dose dependent manner (Figure 2BV The other selected peptides, which are poor competitors, might bind Tie2 in regions distant from the Angl/Ang2 binding site. Another explanation may be that the phage peptide has a higher avidity than the free peptide. Indeed, each phage carries several copies of the minor coat protein pill-fused heptapeptide, and this may result in a multivalent binding of the phage to Tie2 coated receptors. Finally, the observations might also be due to the fact that, unlike synthetic peptides, phage-linked peptides can be conformationally constrained by the phage coat proteins.

Example 2: in vitro activity of the selected peptide

Based on the ELISA competition assay, peptide T4 was chosen for further studies. The inhibition by peptide T4 of the Angl/Ang2 binding to Tie2 was further characterized by surface plasmon resonance (Figure 3).

Competition assays were performed using a Biacore 2000 instrument. Staphylococcal protein A (Sigma) was covalently immobilized on the carboxymethylated dextran matrix of a

CM5 sensor chip (Biacore AB), using the Amine Coupling Kit as described by the manufacturer, to a level of 1100 RU (resonance units, IRU =lpg/mm²). This surface was then used to capture Tie2-Fc by its Fc moiety, to a level of 1200 RU. Mixtures of Angl (0.33 μg/ml) or Ang2 (1 μg/ml) with peptides T4 or T7 (0 to 1 mM) were then injected at a flow rate of 10 μl/min over the Tie2-Fc/protein A surface for 3 minutes. Negative controls, obtained by injecting the Ang/peptide mixtures directly onto the protein A surface, were substracted to determine the specific binding profiles of Angl orAng2 to Tie2 in the presence or absence of peptide. The angiopoietin concentration was chosen to obtain a linear association phase over a time lapse of more than 100s: the slopes of the different association profiles were measured, and plotted against the concentration of peptide to calculate the inhibition constants (Ki).

The Ki were respectively of 3.2 (±0.3)xl0^"4 M and 3.2(±0.8)xl0^"4 M. On the contrary, T7 was unable to compete with Ang2 or Angl for binding to Tie2 (Figure 3). The Ki of the selected peptides could be improved by chemical modifications or site-directed mutagenesis. For example, the affinity of P-selectin binding peptide was increased almost 800-fold via the introduction of a gallic acid moiety at the N-terminus (Appeldoorn et al., 2003).

Example 3: ex vivo activity of the selected peptide

Since Tie2 is an endothelial cell-restricted receptor, the Inventors tested if T4 could inhibit Angl signal transduction in human umbilical vein endothelial cells (HUVECs). Angl had been previously shown to activate the MAPK signaling cascade in HUVECs. The pharmacological inhibition of ERK activation with PD98059 suppressed Angl-induced migration (Kim et al., 2002), as well as the antiapoptotic properties of Angl (Harfouche et al,

2003). The phosphorylation of ERKl and ERK2 in response to Angl in HUVECs was first measured.

HUVECs were isolated from umbilical cord veins by collagenase perfusion and were cultivated on gelatinized-dishes in SFM medium (Invitrogen) supplemented with 20% fetal calf serum, 100 μg/ml of heparin, 20 ng/ml of FGF-2, 10 ng/ml of EGF (Sigma), 50 units/ml penicillin and 50 μg/ml streptomycin. Only cells from passages 2 to 5 were used for experiments.

HUVECs were serum-starved for 16 h, trypsinized, and replated. After 6 h, cells were stimulated for 10 min with Angl (300 ng/ml) or FGF-2 (100 ng/ml) with or without Tie2s (Tie2-Fc ; 30 μg/ml) or peptide preincubated 1 h prior to stimulation. Cells were lysed in Laemmli buffer. Proteins were separated on a SDS-PAGE (7,5%), and electrophoretically transferred onto polyvinylidone difluoride membrane (Immobilon-P). Membranes were probed with the anti-phospho p42/p44 MAPK monoclonal antibody (Sigma) or an anti-p42 MAP Kinase antibody (EB 14). The immunoreactive bands were visualised with ECL system (Amersham Pharmacia Biotech) .

Figure 4 A shows that Angl induced a strong p42/p44 phosphorylation. Angl binding to Tie2 expressed by endothelial cells was specifically responsible for this MAPK activation, as it was completely abolished by recombinant soluble Tie2 receptor. To determine the activity of peptide T4, HUVECs were stimulated with Angl in the presence or absence of a series of concentrations of T4 (Figure 4BV Results show that T4 completely inhibited the activation of MAPK induced by Angl, whereas peptide T7 at the same concentration had no inhibitory effect. T4 suppressed Angl-induced MAPK activity in a dose dependent manner with an IC50 between 150 or 200 μM. The peptide alone did not activate MAPK phosphorylation. The specificity of peptide T4 was then explored by evaluating its action on another receptor tyrosine kinase, FGF-R, which is expressed in HUVECs. While T4 inhibits the ERK activation by Angl, it had no effect on the MAP kinase activation in response to the FGF-R agonist FGF-2 (Figure 4C).

Previous in vitro experiments have shown that Angl has little effect on proliferation, but that it potently stimulates endothelial cell migration (Witzenbichler et ah, 1998). The effect of T4 on Angl-induced migration of HUVECs was then evaluated.

Endothelial cell migration assays were performed using a 24-well chemotaxis chamber

(Transwell, Costar), and performed as described (Witzenbichler et ah, 1998). Cell migration was stimulated with Angl (300 ng/ml) or VEGF (10 ng/ml). Angl induce a >3.5-fold increase in cell migration when compared with the control

(Figure 5 A, Figure 5BV This increase was totally inhibited in the presence of peptide T4. On the contrary, T4 did not abolish VEGF-induced migration, demonstrating its specificity towards the Ang/Tie2.

Example 4: in vivo anti- angiogenic activity of the selected peptide

The inventors next tested anti-angiogenic activities of T4 in vivo. The chick chorioallantoic membrane (CAM) assay, which is usually employed as an in vivo model to both study physiological angiogenesis and test pro- and anti-angiogenic compounds (Kim et ah, 2003 ; Yan et ah, 2003), was chosen. CAM assays were performed as previously described (Le Noble et al, 1993). Briefly, fertile normal brown leghorn eggs were incubated for 2 days in a humidified atmosphere at 37°C. At day 2, a rectangular window was made in the egg shell, the window was covered with scotch tape to prevent dehydration and the eggs were reincubated until day 7. At day 7, a silastic ring was placed on the CAM to allow local drug application. 40μl of a 1OmM T4 or T7 peptide solution in PBS or PBS vehicle alone was applied in the ring. Eggs were resealed and reincubated for 24 ^' hours. In vivo pictures were taken using a Leica MZFLIII stereomicroscope equipped with a digital camera (CoolsnapCF, Photometries) and Metaview analysis software (Universal Imaging cooperation). The significance of differences between groups was performed using a two-tailed

Student's t-test. Values are represented as mean ± S.D. A P value of less than 0.05 was interpreted as statistically significant.

The CAM is relevant because Angl and Ang2 are expressed in the CAM during angiogenesis (Moyon et al, 2001) and chicken receptor binds both human Angl and Ang2 in a similar manner to human receptors (Jones et al., 1998). In addition, chicken Angl and Ang2 display a very high degree of homology to their human counterparts (Jones et al., 1998), suggesting that this assay constitutes a pertinent model to test T4 peptide. Because neither Angl nor Ang2 alone promote angiogenesis in vivo, we studied the effect of T4 peptide on angiogenesis without addition of exogenous factor. T4 peptide was applied at day 7 (n=8 ; Figure 6C-6D), a stage where a strong angiogenesis occurs in the CAM (Kim et al., 2003). In 7/8 CAMs, a striking reduction in vessel density was observed (Figure 6C). hi some cases, many zones remained completely avascular (Figure 6D). hi contrast, treatment of CAMs with the control T7 peptide (n= 5 ; Figure 6B), or PBS vehicle alone (n=3 ; Figure 6A), failed to induce any obvious change in vessel morphology. Soluble Tie-2 Fc receptor induces either a weak or no reduction in vessel density.

hi summary, the Inventors have shown that peptide T4 (NLLMAAS) inhibited, in a concentration-dependent manner, the binding of Angl and Ang2 to immobilized Tie2. It also specifically inhibited Angl -induced signal transduction and the migration of human endothelial cells. Moreover, the Inventors have demonstrated that this peptide can inhibit angiogenesis in vivo, in a well-characterized model of angiogenesis, the CAM assay. Although T4 may block both Angl and Ang2 binding to Tie2, the resulting effect is an inhibition of angiogenesis. A comparison of the primary sequence of human Angl with that of the peptide T4 only revealed an alignment of two residues (NL) with Angl at several positions, which is not significant. This may suggest that the binding site of Angl on Tie2 is discontinuous and that the selected peptide may contain residues distant in the Angl primary sequence, but in close proximity in the folded molecule.

Several studies have shown that interfering with the Tie2 pathway results in murine tumor regression (Lin et al., 1997 ; Siesmeister et al., 1999). In addition, it has been shown that the proportion of Tie2-positive vessels was significantly higher in breast cancer than in either healthy breast tissue or benign lesions (Stratmann et al., 1998, 2001). In highly angiogenic tumors such as glioblastomas, cell type-specific up-regulation of Tie2, Angl and Ang2 has been reported (Stratmann et al., 1998).

The Inventors thus report the first evidence of a short peptide (NLLMAAS)₅ unrelated to Angl or Ang2, which interacts with Tie2. This specific inhibitor of the Tie2 pathway is a good lead compound for the development of therapeutic agents against tumor angiogenesis. The small size of this peptide offers the possibility of designing structurally mimetic non- peptidic molecules via standard organic synthesis. This could result in the production of inexpensive drugs to be administered orally. Moreover, this bioactive peptide is useful to dissect the signal transduction mechanisms involving the Tie2 receptor in endothelial cells which express multiple receptors and provides a potent tool to inhibit angiogenesis in vivo.

REFERENCES

Appeldoorn, CC, Molenaar, TJ., Bonnefoy, A., van Leeuwen, S.H., Vandervoort, P.A., Hoylaerts, M.F. et al. (2003). Rational optimization of a short human P-selectin-binding peptide leads to nanomolar affinity antagonists. J Biol Chem. 278, 10201-10207.

Binetruy-Tournaire, R., Demangel, C, Malavaud, B., Vassy, R., Rouyre, S., Kraemer, M. et al. (2000) Identification of a peptide blocking vascular endothelial growth factor (VEGF)- mediated angiogenesis. EMBO J. 19, 1525-1533.

Carmeliet, P. (2003) Angiogenesis in health and disease. NatMed.9, 653-660.

Cwirla, S.E., Balasubrarnanian, P., Duffin, D.J., Wagstrom, C.R., Gates, CM., Singer, S.C et al. (1997) Peptide agonist of the thrombopoietin receptor as potent as the natural cytokine. Science 13, 1696-1699.

Davis, S., Aldrich T.H., Jones, P.F., Acheson, A., Compton D.L., Jain, V. et al. (1996) Isolation of angiopoietin-1 a ligand for the Tie-2 receptor, by secretion-trap expression cloning. Cell. 87, 1161-1169.

Dumont, D.J., Yamaguchi, T. P., Conlon, R.A., Rossant, J. and Breitman, MX. (1992) Tek, a novel tyrosine kinase gene located on mouse chromosome 4, is expressed in endothelial cells and their presumptive precursors. Oncogene. 7, 1471-1480. Dumont, DJ., Gradwohl, G., Fong, G.H., Puri, M.C., Gerstsenstein, M., Averbach, A. et al. (1994). Dominant-negative and targeted null mutations in the endothelial receptor tyrosine kinase, tek, reveal a critical role in vasculogenesis of the embryo. Genes and Dev. 8, 1897- 1909. Gale, N. W., Thurston, G., Hackett, S. F., Renard, R., Wang, Q., McClain, J. et al. (2002)

Angiopoietin-2 is required for postnatal angiogenesis and lymphatic patterning, and only the latter role is rescued by Angiopoietin-1. Dev. Cell 3, 411-423.

Harfouche, R., Gratton, J.P., Yancopoulos, G.D., Noseda, M., Karsan, A. and Hussain, S.N. (2003) Angiopoietin-1 activates both anti- and proapoptotic mitogen-activated protein kinases. FASEB J. 17, 1523-1525.

Jones, P.F., McClain, J., Robinson, D.M., Sato, T.N. and Yancopoulos, G.D. (1998) Identification and characterisation of chicken cDNAs encoding the endothelial cell-specific receptor tyrosine kinase Tie2 and its ligands, the angiopoietins. Angiogenesis 2, 357-364.

Jones N, Iljin K, Dumont DJ, Alitalo K. (2001). Tie receptors: new modulators of angiogenic and lyrnphangiogenic responses. Nat Rev MoI Cell Biol.2, 257-67. Kim, L, Ryu, Y. S., Kwak, H. J., Ahn, S. Y., Oh, J. L., Yancopoulos, G. D. et al. (2002)

EphB ligand, ephrinB2, suppresses the VEGF- and angiopoietin 1 -induced Ras/mitogen- activated protein kinase pathway in venous endothelial cells. FASEB J. 16, 1126-1128.

Kim, J.S., Chang, J.H., Yu, H.K., Ahn, J.H., Yum, J.S., Lee, S.K., Jung, K.H., Park, D.H., Yoon, Y., Byun, S.M., Chung, S. I. (2003) Inhibition of angiogenesis and angiogenesis- dependent tumor growth by the cryptic kringle fragments of human apolipoprotein(a). J Biol Chem. 278, 29000-29008.

Le Noble, F. A., Schreurs, N.H, van Straaten, H. W, Slaaf, D. W, Smits, J.F. et al. (1993) Evidence for novel angiotensin II receptor involved in angiogenesis in chick embryo chorioallantoic membrane. Am. J. Physiol. 264, R460-R465.

Lin, P., Polverini, P., Dewhirst, M., Shan, S ., Roao, P.S and Peters K. G. (1997) Inhibition of angiogenesis using a soluble receptor establishes a role for Tie-2 in pathologic vascular growth. J. Clin. Invest. 100, 2072-2078.

Maisonpierre, P.C., Suri, C, Jones, P.F., Bartunkova, S., Wiegand, SJ., Radziejewski, C. et al. (1997) Angiopoietin-2, a natural antagonist for Tie-2 that disrupts in vivo angiogenesis. Science. 277, 55-60.

Mochizuki, Y., Nakamura, T., Kanetake, H., and Kanda, S. (2002) Angiopoietin 2 stimulates migration and tube-like structure formation of murine brain capillary endothelial cells through c-Fes and c-Fyn. J. Cell. Sci. 115, 175-183. Moyon, D., Pardanaud, L., Yuan, L., Breant, C. and Eichmann, A. (2001) Selective expression of angiopoietin 1 and 2 in mesenchymal cells surrounding veins and arteries of the avian embryo. Mech Dev. 106, 133-136.

Papapetropoulos, A., Garcia-Cardena, G., Dengler, TJ., Maisonpierre, P.C., Yancopoulos, G.D., and Sessa, W. C. (1999) Direct actions of angiopoietin- 1 on human endothelium: evidence for network stabilization, cell survival, and interaction with other angiogenic growth factors. J. Biol. Chem. 29, 213-223.

Papapetropoulos, A., Fulton, D., Mahboubi, K., KaIb, R.G., O'Connor, D. S., Li, F. et al. (2000) Angiopoietin- 1 inhibits endothelial cell apoptosis via the Akt/survivin pathway. J. Biol. Chem. 275, 9102-9105.

Sato, T.N., Tozawa, U., Deutsch, U., Wolburg-Bucholz, K., Fujiwara, Y., Gendron- Maguire, M. et al. (1995) Distinct roles of the receptor tyrosine kinase Tie- 1 and Tie-2 in blood vessel formation. Nature. 376, 70-74.

Loughna S, Sato TN. (2001). Angiopoietin and Tie signaling pathways in vascular development. Matrix Biol. 20, 319-25. Schim, W. S. N., Teh, M., Mack, P. O., and Ge, R. (2001) Inhibition of angiopoietin-1 expression in tumor cells by an antisense RNA approach inhibited xenograft tumor growth in immunodeficient mice. Int. J. Cancer 94, 6-15.

Siemeister, G., Schirner, M., Weindel, K., Reusch, P., Menrad, A., Marme, D. et al. (1999) Two independent mechanisms essential for tumor angiogenesis: inhibition of human melanoma xenograft growth by interfering with either the vascular endothelial growth factor receptor pathway or the Tie-2 pathway. Cancer Res. 59, 3185-3191.

Smith, G.P. (1985) Filamentous fusion phage: novel expression vectors that display cloned antigens on the virion surface. Science, 228, 1315-1317. Stratmann, A., Risau, W., and Plate, K. H. (1998) Cell type-specific expression of angiopoietin-1 and angiopoietin-2 suggests a role in glioblastoma angiogenesis. Am. J. Pathol. 5, 1459-1466.

Stratmann, A., Acker, T., Burger, A. M., Amann, K., Risau, W., and Plate, K. H. (2001) Differential inhibition of tumor angiogenesis by tie2 and vascular endothelial growth factor receρtor-2 dominant-negative receptor mutantsJnt. J Cancer 91, 273-282. Suri, C, Jones, P.F., Patan, S., Bartunkova, S., Maisonpierre, P.C., Davis, S. et al. (1996)

Requisite role of angiopoietin-1, a ligand for the TIE2 receptor, during embryonic angiogenesis. Cell. 87, 1171-1180.

White, R.R., Shan ,S., Rusconi, C.P., Shetty, G., Dewhirst, M.W., Kontos, CD. et al. (2003) Inhibition of rat corneal angiogenesis by a nuclease-resistant RNA aptamer specific for angiopoietin-2. Proc Natl Acad Sd USA. 100, 5028-5033.

Witzenbichler, B., Maisonpierre P.C., Jones, P., Yancopoulos, G.D. and Isners, J.M. (1998) Chemotactic properties of angiopoietin-1 and -2, ligands for the endothelial-specific receptor tyrosine kinase Tie2. J. Biol. Chem. 273, 18514-18521.

Wu X, Zhao R, Li Z, Yao M, Wang H, Han J, Qu S, Chen X, Qian L, Sun Y, Xu Y, Gu J. (2004) A novel small peptide as a targeting ligand for receptor tyrosine kinase Tie2. B.B.R.C. 315, 1004-10.

Yan, X., Lin, Y., Yang, D., Shen, Y., Yuan, M., Zhang, Z. et al. (2003) A novel anti- CD146 monoclonal antibody, AA98, inhibits angiogenesis and tumor growth. Blood 102, 184-191.

Claims

REVENDICATIONS

1. The use of a 7-mer peptide library for the screening of peptides liable to bind to the Tie2 receptor, said peptides having agonist or antagonist properties with respect to the Tie2

S receptor.

2. The use of a 7-mer peptide library according to claim 1, for screening peptides liable:

- to inhibit the binding of angiopoetins to the Tie2 receptor,

- to favour the binding of angiopoetins to the Tie2 receptor, or 0 - to mimic the binding of angiopoetins to the Tie2 receptor.

3. The use of a 7-mer peptide library according to claim 1 or 2, for screening peptides liable:

- to inhibit the binding of Angl to the Tie2 receptor,

- to favour the binding of Angl to the Tie2 receptor, or 5 - to mimic the binding of Angl to the Tie2 receptor.

4. The use of a 7-mer peptide library according to claim 1 or 2, for screening peptides liable:

- to inhibit the binding of Ang2 to the Tie2 receptor,

- to favour the binding of Ang2 to the Tie2 receptor, or 0 - to mimic the binding of Ang2 to the Tie2 receptor.

5. The use of a 7-mer peptide library according to any of claims 1 to 4, for screening peptides liable to inhibit both the binding of Angl and Ang2 to the Tie2 receptor.

5 6. A process for screening a 7-mer peptide liable to inhibit the binding of angiopoetins to the Tie2 receptor, comprising:

- selecting among the peptides recovered at the preceding step, the peptides which inhibit the 0 binding of Angl and/or of Ang2 to the Tie2 receptor.

7. A process for screening a 7-mer peptide liable to inhibit the binding of angiopoetins to the Tie2 receptor according to claim 6, comprising an additional step of selecting among the peptides selected at the preceding stage, the peptides which inhibit - Angl and/or Ang2 induced signal transduction, and/or

- endothelial cell migration.

8. A peptide liable to bind to the Tie2 receptor, said peptide having agonist or antagonist properties with respect to the Tie2 receptor, the sequence of said peptide presenting less than about 20% sequence identity with the amino acid sequences of Angl and Ang2.

9. A peptide liable to bind to the Tie2 receptor according to claim 8, wherein the sequence of said peptide presents essentially no sequence identity with the amino acid sequences of Angl and Ang2.

10. A peptide liable to bind to the Tie2 receptor according to claim 8 or 9, wherein said peptide has a length of about 5 to 15 amino acids, in particular of about 7 amino acids.

11. A peptide liable to bind to the Tie2 receptor according to any of claims 8 to 10, said peptide being selected from the group consisting of

T4 (NLLMAAS, SEQ ID NO: 2),

T6 (KXWVIPK, SEQ ID NO: 4),

T7 (HHHRHSF, SEQ ID NO: 6) and T8 (HPWLTRH, SEQ ID NO: 8), or a peptide derived from T4, T6, T7 or T8 by substitution, deletion or insertion of one or several amino acids, provided that said derived peptide is liable to bind to the Tie2 receptor.

12. A peptide liable to bind to the Tie2 receptor according to any, of claims 8 to 11, said peptide corresponding to T4, or a peptide derived from T4 by substitution, deletion or insertion of one or several amino acids, provided that said derived peptide is liable to bind to the Tie2 receptor, to inhibit the binding of both Angl and Ang2 to the Tie2 receptor, and to inhibit the signal transduction and the migration of endothelial cells mediated by the Tie2 receptor.

13. A nucleic acid coding for T4, T6, T7 or T8, and in particular a nucleic acid of sequence AATCTGCTTATGGCGGCGTCT (SEQ ID NO: 1), AAGCTGTGGGTGATTCCTAAG (SEQ ID NO: 3), CATCATCATAGGCATTCGTTT (SEQ ID NO: 5), or CATCCTTGGCTTACTCGTCAT (SEQ 3D NO: 7).

14. A recombinant vector comprising a nucleic acid according to claim 13, in particular a recombinant vector selected from a bacterial expression vector, a yeast expression vector, a mammalian expression vector or a viral expression vector.

15. Prokaryotic or eukaryotic cells transformed with a nucleic acid according to claim 13 and/or a recombinant vector according to claim 14.

16. A pharmaceutical composition comprising as active substance at least one peptide according to claim 11 or 12, in particular T4, in association with a pharmaceutically acceptable carrier.

17. A pharmaceutical composition according to claim 16, suitable for the administration of a unit dose of about 1 to 100 mg/kg/day, in particular of about 10 mg/kg/day of the peptide according to claim 11 or 12.

18. The use of a peptide according to claim 11 or 12, for the manufacture of a medicament useful for - the treatment of pathologies requiring the inhibition of endothelial proliferation, such as tumors, in particular angiomas or angiosarcomas, age related macular degeneration, diabetic retinopathy, or rheumatoid arthritis, or

- the treatment of pathologies requiring the inhibition of endothelial activation, such as allograft or xenograft rejection, acrocyanosis, sclerodermia, in particular psoriasis, or - promoting healing, in particular wound healing, tissue reconstruction, in particular for muscle and skin grafts in plastic surgery, ovarian induction, reperfusion of ischemic areas in case of arteritis of the lower limbs or of myocardial infarction, or

- preparing transplant grafts before implantation.

19. The use according to claim 18, of T4, for the manufacture of a medicament useful for

- the treatment of pathologies requiring the inhibition of endothelial proliferation, such as tumors, in particular angiomas or angiosarcomas, age related macular degeneration, diabetic retinopathy, or rheumatoid arthritis, and/or - the treatment of pathologies requiring the inhibition of endothelial activation, such as allograft or xenograft rejection, acrocyanosis, sclerodermia, in particular psoriasis.