the phage display procedures in the present invention are based on screening of 7 amino acid residues in length , which can selectively binds to α chain of il - 6r from a phage peptide library purchased from new england biolabs ( beverly , mass ., usa ). screening of the 7 - mer peptide phage library of random amino acid sequences containing 2 × 10 9 phage clones was carried out with cell culture dishes coated with il - 6rα ( purchased from r & amp ; d systems , minneapolis , minn .) in the invention . the abovementioned phage clones were sequentially added to the il - 6rα coated cell culture dishes for il - 6rα absorption . plate - bound phage clones were washed with glycine buffer ( ph 2 . 2 ) and neutralized with tris buffer ( ph 9 . 1 ) to remove the unbound phage clones . after 3 rounds of selection , about 10 . 3 % ( 31 of 300 ) of the phage clones analyzed exhibited il - 6α - binding ability ( data not shown ). these 31 il - 6rα - binding clones were isolated and analyzed the sequences . seven dna sequences were shown to be translated into different peptides and were listed in table 1 as seq id no : 1 , seq id no : 2 , seq id no : 3 , seq id no : 4 , seq id no : 5 , seq id no : 6 , and seq id no : 7 . to further confirm the il - 6rα binding ability of these seven different peptides , individual phage clones inserted with dna encoding these seven peptides respectively ( hereafter labeled as phage clone s1 , s2 , s3 , s4 , s5 , s6 and s7 ) were added into cell culture dishes precoated with il - 6rα ( 10 11 pfu / ml ). the results revealed that phage s5 , phage s6 and phage s7 significantly inhibited the binding of il - 6 to il - 6rα , while phage s1 , phage s2 , phage s3 and phage s4 did not . the binding affinity of phage s7 to different cell lines was determined by the in vitro binding assay . phage s7 showed higher binding affinity than phage s1 did in all membrane - type il - 6rα - expressing cell lines . in addition , results of immunofluorescence staining revealed that phage s7 did bind the plasma membrane of c33a cervical cancer cells ( data not shown ). all the results showed that phage s7 specifically binds to il - 6rα and blocks the interaction between il - 6 and il - 6r □. on the other hand , peptides encoded by the inserted dna in phage s7 ( labeled as ‘ peptide s7 ’ hereafter ) were produced by the known peptide synthesis method . the in vitro competition assay of peptide s7 in the present invention revealed that peptide s7 could antagonize the binding of il - 6 to il - 6rα in different cell lines . it has been reported that il - 6 acts as an antiapoptotic factor via up - regulation of mcl - 1 protein through the pi3k / akt and mapk signaling pathways to reach the goal of antiapoptosis in a variety of human malignancies . the peptide s7 of the present invention inhibited il - 6 - induced activation ( phosphorylation ) of akt kinase and mapk kinase . that &# 39 ; s to say peptide s7 blocked il - 6 - mediated pi3k / akt and mapk signaling pathways . furthermore , peptide s7 inhibited il - 6 - induced up - regulation of mcl - 1 protein in order to inhibit the antiapoptotic effects mediated by il - 6 . chemotherapy - induced apoptosis of cancer cells will be enhanced due to loss of il - 6 - mediated antiapoptosis and therefore the therapeutic effect of chemotherapy is increased . in addition , because il - 6 is known to induce the expression of vascular endothelial growth factor - a ( vegf - a ) and angiogenesis in cervical cancer , peptide s7 of the present invention is able to block il - 6 - induced expressions of vegf - a protein and mrna . the examples of cancer cells includes cervical carcinoma , multiple myeloma , kaposi &# 39 ; s sarcoma , prostate cancer and basal cell carcinoma ( bcc ), but not limited to these . on the other hand , angiogenesis assays were carried out to further confirm that peptide s7 of the present invention greatly attenuated il - 6 - induced human umbilical vein endothelial cells ( huvecs ) proliferation and capillary - like tubule formation . it is apparent that peptide s7 of the present invention is able to block il - 6 - induced angiogenesis . people who skilled in the art will easily understand through reading the abovementioned description of this specification , the oligopeptides according to the present invention may be produced by incorporating a dna sequence encoding the desired oligopeptide into expression vectors and expressing the peptides of the present invention via the expression vectors from the known technology . in addition , people who skilled in the art can also learn from this specification that the oligopeptides or the phage clones expressing the peptide of the present invention can be combined with a pharmaceutical acceptable carrier to produce a medical composition to inhibit the il - 6 - mediated tumor growth . in addition , based on the in vivo experiment , the peptide s7 of the present invention further significantly suppresses il - 6 - induced tumor growth . therefore the peptide s7 of the present invention has a fairly good antitumor effect in controlling il - 6 - induced tumor growth . the binding affinities to il - 6rα of the 7 independent peptide sequences of the ir - 6rα - binding clones selected from phage display peptide library ( table 1 ) were confirmed . the phage clones with the inserted dna encoding these 7 different peptide sequences ( phage s1 ˜ s7 ) were added into il - 6rα coated 96 - well cell culture plates ( 10 12 pfu / ml ) and incubated with il - 6rα for 1 hour . il - 6 protein ( 50 ng / ml , 100 μl ) was added to the wells and incubated at room temperature for 2 hours . the plates were thoroughly washed with 0 . 1 % bsa ( bovine serum albumin )/ pbs ( phosphate - buffered saline ) buffer ( ph 8 . 5 ). finally , biotin - conjugated anti - il - 6 monoclonal antibody , horseradish peroxidase ( hrp )- conjugated streptavidin and tetramethyl benzidine ( tmb ) substrate solution were used to perform the known phage enzyme - linked immunosorbent assay ( elisa ) to determine the l - 6 protein bound to the cell plates . the absorbance at 450 nm was read with a reference wavelength of 650 nm ( a450 / 650 ) and got the result shown in fig1 . the results of fig1 revealed that phage s5 , phage s6 and phage s7 significantly inhibited the binding of il - 6 to il - 6rα , while phage s1 , phage s2 , phage s3 and phage s4 did not . phage s7 has the best inhibition effect among them . in vitro binding assay of phage clones to different cell lines c33a , hela , and siha ( cervical carcinoma ) cells , basal cell carcinoma ( bcc ) cells , and hek293 fibroblast cells ( all were obtained from invitrogen , carlsbad , calif .) were cultivated in dmem containing 10 % fetal bovine serum ( fbs ). human umbilical vein endothelial cells ( huvec ) were obtained by digesting human umbilical cords with 0 . 1 % collagenase ii , collected and cultivated in m199 medium supplemented with 10 % fbs . aforementioned cell lines were plated on 96 - well plates and cultured to 90 % of confluence for phage elisa analysis . after overnight cultivation , cells were fixed with 0 . 125 %, ice - cold glutaraldehyde at room temperature for 10 min and then washed with pbs . pbs containing 3 % bsa were used to block the plates by overnight incubation at 4 ° c . after blocking , phages s7 ( 5 × 10 12 pfu / ml ) were added into the plate and incubated for 2 hours at room temperature . wells were washed with tris - buffered saline ( tbs , ph 7 . 5 ) containing 0 . 1 % tween 20 . bound phages were detected by elisa using a horseradish peroxidase ( hrp )- conjugated anti - m13 monoclonal antibody ( mab ). and the result is shown in fig2 . as shown in fig2 , phage s7 showed higher binding affinity than phage s1 ( negative control ) in all membrane - type il - 6rα - expressing cell lines but not in il - 6rα negative huvec cells . oligopeptides encoded by the inserted dna in phages s7 and s1 ( labeled as ‘ peptide s7 ’ ( seq id no : 7 ) or ‘ peptide s1 ’ ( seq id no : 1 ) hereafter ) were produced by the known peptide synthesis method . the binding assay described in example 1 was carried out , but using peptide s7 or peptide s1 ( negative control ) instead of phage clones , and using cell lines instead of il - 6rα to perform competition assay and get the result shown in fig3 . fig3 shows that peptide s7 indeed antagonize the binding of il - 6 to il - 6rα in different cell lines . 80 % confluent c33a cells were starved for 24 hours and then treated with human il - 6 protein ( 50 ng / ml ) in the presence or absence of s1 peptide ( 50 μmol / l ) or s7 peptide ( 50 μmol / l ). cell lysates were obtained and subjected to sds - page separation and western blot analysis using various antibodies for immunoblotting , such as anti - phospho - erk1 / 2 , anti - phospho - akt , anti - erk1 / 2 , and anti - akt . the results are shown in fig4 a . fig4 a revealed that the phosphorylated akt and erk1 / 2 mapk levels were increased in il - 6 - treated c33a cervical cancer cells and this activation could be significantly inhibited by peptide s7 treatment but not peptide s1 treatment ( negative control ). those results indicate that the ras / mapk and pi3 - k / akt signaling pathways could be significantly inhibited by peptide s7 treatment . equal amounts of cell lysates ( 75 μg ) were resolved by sds - page , transferred to polyvinylidene difluoride membranes , and probed with specific anti - mcl - 1 antibodies as described above . β - actin served as the internal loading control to get the result shown in fig4 a . as shown in fig4 b , il - 6 - induced up - regulation of mcl - 1 protein is also antagonized by peptide s7 . c33a cervical cancer cells , rpmi 8226 multiple myeloma cells and basal cell carcinoma ( bcc ) cells , vectors ( negative control ) were cultivated respectively in dmem containing 10 % fbs , penicillin ( 100 units / ml ), and streptomycin ( 100 μg / ml ) as well as il - 6 protein . at 90 % confluence , culture medium was replaced with serum - free medium . il - 6 containing c33a cells were incubated with s 1 or s7 peptide for another 24 hours . conditioned medium ( cm ) was collected after centrifugation of cellular debris . the conditioned medium ( cm ) was concentrated using an amicon ultracentrifugation device ( millipore ). the concentrations of vegf - a in culture supernatants were determined with quantitative sandwich elisa assay according to the manufacturer &# 39 ; s instruction . briefly , cell supernatant ( 50 μl ) was incubated with 50 μl of assay diluents for 2 hours at room temperature in a 96 - well tissue culture plate coated with monoclonal antibodies against vegf - a . after five consecutive washes , a conjugate consisting of polyclonal vegf - a antibodies and hrp was added . the mixture was incubated for 2 hours at room temperature . following the subsequent addition of a color reagent , absorbance was read at 450 nm using a thermo - max microplate reader ( molecular devices co ., menlo park , calif .). the results are shown in fig5 . as shown in fig5 , elevated levels of vegf - a secretion due to il - 6 stimulation paralleled the increased expression of vegf - a protein ( data not shown ), indicating that a mature and functionally active vegf - a protein was simultaneously generated in il - 6 - treated cells . peptide s7 significantly decreased il - 6 - mediated vegf - a secretion in all three cell lines . the inhibition of peptide s7 in il - 6 - induced angiogenesis activity was analyzed with angiogenesis assays from cm collected as abovementioned , such as proliferation and capillary - like tubules formation by huvecs in vitro . huvecs were plated onto six - well dishes ( falcon , becton dickinson ) at a concentration of 2 . 5 × 10 5 cells per well in m199 medium supplemented with 10 % fbs . one day after seeding , huvecs were stimulated with cm from cells treated in various ways respectively , where the cm was mixed with m199 medium . twenty - four hours later , the viable cells were counted using a trypan blue exclusion method . for the trypan blue exclusion assay , cells were washed with pbs , trypsinized , and then resuspended in 1 ml pbs . trypan blue - stained cells were then counted using a modified neubauer hemocytometer under a phase - contrast light microscope . the data was analyzed by statistic methods and is shown in fig6 . as shown in fig6 , cm from il - 6 - overexpressed cells ( il - 6 - cm ) significantly increased the proliferation of huvecs , and il - 6 - cm induced huvecs proliferation seemed to be greatly attenuated by peptide s7 but not by peptide s1 . in vitro assessment using a growth factor - reduced basement membrane matrigel matrix was carried out to evaluate capillary tube - like formation . the matrigel was thawed at 4 ° c . and mixed to homogeneity . the bottom of 96 - well cell culture plates were coated with a thin layer of matrigel ( 40 μl ) and allow the matrigel to polymerize at 37 ° c . for 30 minutes . huvecs were resuspended in m199 medium containing 1 % serum to a density of 2 . 5 × 10 4 cells / 100 μl , mixed with 100 μl of m199 medium containing 1 % serum and 100 μl cm from either c33a / neo or c33a / il - 6 cells treated in various ways , and finally plated onto the matrigel - coated surface . six hours later , cells were fixed in 4 % paraformaldehyde and stained with 0 . 1 % crystal violet . three microscopic fields were selected at random and photographed , and the number of tube - like structures per field was determined to get the result shown in fig7 . fig7 showed that c33a / il - 6 - cm induced tube - like cell cord formation ( 5 . 1 fold of the control group ), which was almost completely inhibited by peptide s7 . on the other hand , matrigel plug assay was performed to analyze the inhibiting effect on il - 6 - induced angiogenesis of peptide s7 . matrigel ( 500 μl ) containing cm from cells treated in various ways was iv - injected into 4 - to 8 - week - old female balb / c nude mice at sites lateral to the abdominal midline . aforementioned cm was obtained either from vector control cells or from il - 6 overexpressed c33a cells in the presence or absence of peptide s7 . the matrigel plugs were recovered after 7 days of implementation , dissolved in pbs , and incubated at 4 ° c . overnight . hemoglobin levels were determined using drabkin &# 39 ; s solution ( sigma chemical ) according to the manufacturer &# 39 ; s instructions to get the result shown in fig8 . result of fig8 clearly showed that hemoglobin level was significantly elevated in plugs containing c33a / il - 6 - cm than in plugs containing c33a / neo - cm , and hemoglobin induction was almost completely inhibited by peptide s7 . therefore , all the results from the above angiogenesis experiments showed that peptide s7 of the invention effectively blocked il - 6 - induced expression of vegf - a and the angiogenesis . six - to 8 - week - old female severe combined immunodeficient ( scid ) mice were iv - injected with 1 × 10 6 c33a / neo or c33a / il - 6 cells . beginning 3 days later , s1 or s7 peptide ( 50 mg / kg , dissolved in pbs ) was injected i . p . every 2 days . tumor development was followed in measurements of length ( l ) and width ( w ). tumor volume was calculated with the formula of l 2 w | 2 to get the result shown in fig9 . fig9 showed that showed that administration of peptide s7 significantly reduced il - 6 - induced tumor growth , and peptide s7 inhibited tumor growth by 76 % at the end of the experiment . these results from the above experiments showed an excellent antitumor effect of peptide s7 in inhibition of il - 6 - induced tumor growth .
the present invention provides an antagonist peptide of interleukin - 6 , wherein the peptide comprises a amino acid sequence which is selected from the group consisting of seq id no : 5 , seq id no : 6 and seq id no : 7 . the peptide of the invention is able to specifically bind il - 6r and compete for the binding of il - 6 to il - 6r , to block il - 6 - induced signal transduction and therefore effectively inhibits il - 6 - mediated antiapotopsis and angiogenesis , and further inhibits il - 6 - mediated tumor growth .