mpf - 4 is a naturally - occurring protein composed of 54 amino acid residues and has a molecular weight of about 7 kilodaltons as determined by sds page . mpf - 4 is 100 % homologous with the 54 c - terminal residues of pf - 4 and is thus believed to be a processed form of pf - 4 . the amino acid sequence of mpf - 4 is set forth in seq . id . no : 1 . cpf - 4 is a naturally - occurring protein composed of a 16 amino acid chain ( seq . id . no : 2 ) and the 54 amino acid chain of mpf - 4 ( seq . id . no : 1 ). cpf - 4 has a molecular weight of about 7 . 8 to 8 . 0 kilodaltons as determined by sds page . the two protein chains of cpf - 4 are disulfide bonded between cys - 20 of seq . id . no : 1 and cys - 10 of seq . id . no : 2 . another disulfide bond bridges cys - 36 of seq . id . no : 1 to cys - 12 of seq . id . no : 2 . the ordinarily skilled artisan will understand that some conservative amino acid substitutions can be made to these sequences without adversely affecting the invention . conservative amino acid substitutions include interchanges between gly and ala , asp and glu , asn and gln , phe and tyr , and lys and arg . like the parent protein , both mpf - 4 and cpf - 4 bind heparin and inhibit endothelial cell growth making them attractive candidates for therapeutic use in treating angiogenic and cell proliferative diseases . the heparin binding domain is believed to be lys - 45 through lys - 50 of seq id no : 1 . given the sequence information herein disclosed and the state of the art in solid phase protein synthesis , essentially pure mpf - 4 and cpf - 4 can be obtained via chemical synthesis . the principles of solid phase chemical synthesis of polypeptides are well known in the art and may be found in general texts in the area such as dugas , h . and penney , c ., bioorganic chemistry ( 1981 ) springer - verlag , new york , pgs . 54 - 92 . for example , peptides or proteins such as mpf - 4 may be synthesized by solid - phase methodology utilizing an applied biosystems 430a peptide synthesizer ( applied biosystems , inc ., 850 lincoln center drive , foster city , calif . 94404 ) and synthesis cycles supplied by applied biosystems . boc amino acids and other reagents are commercially available from applied biosystems and other chemical supply houses . sequential boc chemistry using double couple protocols are applied to the starting p - methyl benzhydryl amine resins for the production of c - terminal carboxamides . for the production of c - terminal acids , the corresponding pam resin is used . asparagine , glutamine , and arginine are coupled using preformed hydroxy benzotriazole esters . the following side chain protecting groups may be used : boc deprotection may be accomplished with trifluoroacetic acid in methylene chloride . following completion of the synthesis the peptides may be deprotected and cleaved from the resin with anhydrous hydrogen fluoride ( hf ) containing 10 % meta - cresol . cleavage of the side chain protecting group ( s ) and of the peptide from the resin is carried out at zero degrees centigrade or below , preferably - 20 ° c . for thirty minutes followed by thirty minutes at 0 ° c . after removal of the hf , the peptide / resin is washed with ether , and the peptide extracted with glacial acetic acid and lyophilized . likewise , the state of the art in molecular biology provides the ordinarily skilled artisan another means by which essentially pure mpf - 4 and cpf - 4 can be obtained . although both molecules may be produced by solid phase peptide synthesis , isolation from spent culture medium , or recombinant methods , recombinant methods are preferred if a high yield is desired . the basic steps in the recombinant production of either mpf - 4 of cpf - 4 include : a ) isolation of a natural dna sequence encoding mpf - 4 or through the construction of a synthetic or semi - synthetic dna coding sequence , b ) placing the coding sequence into an expression vector in a manner suitable for expressing proteins either alone or as a fusion proteins , c ) transforming an appropriate eukaryotic or prokaryotic host cell with the expression vector , d ) culturing the transformed host cell under conditions that will permit expression of mpf - 4 or cpf - 4 , and e ) recovering and purifying the recombinantly produced proteins and ( if necessary ) refolding the protein to its native conformation . as previously stated , the coding sequences for the two proteins may be wholly synthetic or the result of modification to the larger , native pf - 4 - encoding dna . a dna sequence that encodes native pf - 4 is described in u . s . pat . no . 5 , 086 , 164 and may be used as starting material in the recombinant production of mpf - 4 or precursor proteins by altering the native sequence to achieve the desired results . synthetic genes , the in vitro or in vivo transcription and translation of which will result in the production of either mpf - 4 or cpf - 4 , may be constructed by techniques well known in the art . owing to the natural degeneracy of the genetic code , the skilled artisan will recognize that a sizable yet definite number of dna sequences may be constructed which encode either mpf - 4 or cpf - 4 . the methodology of synthetic gene construction is well known in the art . see brown , et al . ( 1979 ) methods in enzymology , academic press , n . y ., vol . 68 , pgs . 109 - 151 . dna sequences that encode either mpf - 4 or cpf - 4 may be designed based on the amino acid sequences herein disclosed and the published pf - 4 dna sequence . once designed , the sequence itself may be generated using conventional dna synthesizing apparatus such as the applied biosystems model 380a or 380b dna synthesizers ( applied biosystems , inc ., 850 lincoln center drive , foster city , calif . 94404 ). to effect the expression of either mpf - 4 or cpf - 4 , one inserts the engineered synthetic dna sequence in any one of many appropriate recombinant dna expression vectors through the use of appropriate restriction endonucleases . see generally maniatis et al . ( 1989 ) molecular cloning ; a laboratory manual , cold springs harbor laboratory press , n . y ., vol . 1 - 3 . restriction endonuclease cleavage sites are engineered into either end of the mpf - 4 - encoding dna to facilitate isolation from and integration into known amplification and expression vectors . the particular endonucleases employed will be dictated by the restriction endonuclease cleavage pattern of the parent expression vector to be employed . the choice of restriction sites are chosen so as to properly orient the coding sequence with control sequences to achieve proper in - frame reading and expression of the protein of interest . the coding sequence must be positioned so as to be in proper reading frame with the promoter and ribosome binding site of the expression vector , both of which are functional in the host cell in which the protein is to be expressed . so as to achieve efficient transcription of the synthetic gene , said gene must be operably associated with a promoter - operator region . therefore , the promoter - operator region of the synthetic gene is placed in the same sequential orientation with respect to the atg start codon of the synthetic gene . a variety of expression vectors useful for transforming prokaryotic and eukaryotic cells are well known in the art . see the promega biological research products catalogue ( 1992 ) ( promega corp ., 2800 woods hollow road , madison , wis ., 53711 - 5399 ); and the stratagene cloning systems catalogue ( 1992 ) ( stratagene corp ., 11011 north torrey pines road , la jolla , calif ., 92037 ). also , u . s . pat . no . 4 , 710 , 473 describes circular dna plasmid transformation vectors useful for expression of exogenous genes in e . coli at high levels . these plasmids are useful as transformation vectors in recombinant dna procedures and ( a ) confer on the plasmid the capacity for autonomous replication in a host cell ; ( b ) control autonomous plasmid replication in relation to the temperature at which host cell cultures are maintained ; ( d ) direct synthesis of a protein prod . indicative of plasmid maintenance in a host cell population ; ( e ) provide in series restriction endonuclease recognition sites unique to the plasmid ; and these circular dna plasmids are useful as vectors in recombinant dna procedures for securing high levels of expression of exogenous genes . having constructed an expression vector , the next step is to place the vector into a suitable cell and thereby construct a recombinant host cell useful in the expression of the gene of interest . techniques for transforming cells with recombinant dna vectors are well known in the art and may be found in such general references as maniatis , et al . supra . host cells made be constructed from either eukaryotic or prokaryotic cells . eukaryotic host cells are capable of carrying out post - translational glycosylations on expressed proteins and some are capable of secreting the desired protein into the culture medium . prokaryotic host cells generally produce the protein at higher rates , are easier to culture but are not capable of glycosylating the final protein . proteins which are expressed in high - level bacterial expression systems characteristically aggregate in granules or inclusion bodies which contain high levels of the overexpressed protein . such protein aggregates typically must be solubilized , denatured and refolded using techniques well known in the art . see kreuger , et al . ( 1990 ) in protein folding , gierasch and king , eds ., pgs 136 - 142 , american association for the advancement of science publication no . 89 - 18s , washington , d . c . ; and u . s . pat . no . 4 , 923 , 967 . mpf - 4 and cpf - 4 can also be isolated from the spent culture medium of mitogen - stimulated pbl preparations or any cell line that produces them . in the case of human pbls , the pbls are isolated from the buffy coat of whole blood using any number of methods well known in the art . an example of one of the many published methods for preparing human pbls is singh et al ., purification and biochemical properties of a human monocyte derived growth factor , proc . natl . acad . sci . 85 : 6374 - 6378 , 1985 . once isolated , the pbl preparation is thoroughly washed in a balanced salt solution to remove any non - cellular material . the pbl preparation is then seeded into a defined , serum - free growth medium containing a mitogen . the ordinarily skilled artisan will be readily aware of a wide variety of published and commercially available growth media suitable for culturing pbl preparations . similarly , a number of mitogens capable of stimulating pbl activity are well known in the art . by way of illustration and not limitation , the following are examples of mitogens consistent with the subject invention : lipopolysaccharide ( lps ), phytohemoagglutinin ( pha ), concanavalin a ( cona ), zymozan , and certain antibodies directed at mitogenic determinants . the pbl preparation is then cultured under appropriate conditions for a period of time to allow the formation of mpf - 4 and cpf - 4 , usually one to several days depending on initial seeding density . spent growth medium is then collected and separated from the cells either by filtration , centrifugation or some other method . regardless of the means used to produce mpf - 4 or cpf - 4 , purification will be required . a great variety of protein purification techniques are well known in the art , many of which are suitable and readily apparent to the ordinarily skilled artisan in light of the novel teachings here disclosed . a basic text describing state of the art protein purification techniques is janson and ryden , protein purification , vch publishers inc ., new york 1989 . one particularly useful purification method was discovered and consists of first loading the spent culture medium onto a reversed phase purification column . such columns are well known in the art and may be purchased from numerous vendors including pharmacia , biorad , and amicon . upon interacting with the column , the protein of interest is eluted using an increasing linear gradient of an organic solvent in trifluoroacetic ( tfa ). the preferred organic solvent is acetonitrile , and the fractions containing mpf - 4 and cpf - 4 are found in the 30 - 50 % acetonitrile portion of the gradient . the more preferred portion of the gradient is the 33 - 39 % region . the eluted proteins are then contacted with a heparin affinity resin . the ordinarily skilled artisan will readily realize that this step is best achieved in a column chromatography mode . heparin affinity columns are commercially available from some of the same vendors mentioned above . in this step , the molecules of interest , both mpf - 4 or cpf - 4 , bind to the heparin column and are eluted using an increasing linear salt gradient . the preferred salt is nacl , and the portion of the gradient that is preferably collected is the 0 . 1 - 2 . 0m portion . the more highly preferred portion of the gradient to collect is the 0 . 7 - 2 . 0m portion . the final step is to run the 0 . 7 - 2 . 0m eluate on a second reversed phase column and eluting with a linear acetonitrile gradient in tfa . the preferred gradient is 25 - 75 % acetonitrile and 27 - 67 % is more preferred . the column output is monitored for absorbance at 220 nm . the peak protein fractions are assayed for cellular antiproliferative activity ( bioactivity ). the earlier eluting peak showing bioactivity is cpf - 4 and the later eluting bioactive peak is mpf - 4 . the following examples are useful for guidance in the purification process and for understanding the invention . these examples are for illustrative purposes only and are not meant to limit the invention in any way . pooled buffy coats , prepared from healthy donor blood , was purchased from interstate blood bank . a pbl cell preparation was isolated from the pooled buffy coats by using histopaque ™ ( sigma chemical co . ; st . louis , mo . 63178 ) gradient centrifugation at 4 ° c . the pbl preparation was washed in hank &# 39 ; s balanced salt solution ( gibco ; grand island , n . y .) and plated at a density of 3 × 10 6 cells / ml ( total volume 4 l ) in serum - free , minimal essential medium ( gibco ; grand island , n . y .) supplemented with 2 mm l - glutamine , non - essential amino acids , 0 . 8 mm d - glucose , 100 u / ml penicillin , 100 ug / ml streptomycin and 20 μg per ml lipopolysaccharide ( sigma chemical co . ; st . louis , mo . 63178 ). the pbl preparation was incubated for 30 hours at 37 ° c . in 5 % co 2 , 95 % air . the spent culture medium was harvested and the pbls were removed by filtration through 0 . 2 μm filter . four liters of cell - free spent culture medium were acidified by adding 0 . 1 % ( v / v ) tfa acid and then loaded directly onto a reverse phase c4 - rp - 304 ™ ( 250 × 21 . 5 mm ) semi - preparative column ( biorad , richmond , calif . 94804 ) at a flow rate of approximately 15 ml / min . the column was eluted with a linear gradient of 0 to 50 % acetonitrile in 0 . 1 % tfa over 40 min . and then for 10 minutes at 50 % acetonitrile , 0 . 1 % tfa . the flow rate was 15 ml / min . approximately 50 , 15 ml fractions were collected . the elution profile was monitored at 220 nm . and fractions that eluted with 33 %- 39 % acetonitrile were collected and pooled ( c4 - pool ). the c4 - pool was further fractionated by heparin affinity chromatography on a econo - pac ™ 5 ml heparin - sepharose cartridge ( biorad , richmond , calif . 94804 ). the bound proteins were eluted by a linear gradient of 0 to 2 . 0m nacl in phosphate buffer saline ( pbs ) at a flow rate of 2 . 0 ml / min . the proteins that eluted from the column were pooled into three fractions : ( 1 ) non - heparin binding ( flow through ), ( 2 ) low - affinity heparin binding ( 0 to 0 . 7m nacl ), and ( 3 ) high - affinity heparin binding ( 0 . 7m to 2 . 0m nacl ) fractions . the high affinity heparin binding fraction ( 3 ) ( 0 . 7m to 2 . 0m nacl ) was applied to a vydac ™ 0 . 46 × 10 cm c - 4 hplc column ( the marshall co . ; worthington , ohio 43085 ), previously equilibrated with 27 % acetonitrile , 0 . 1 % tfa . the column was eluted with a linear gradient of 27 % acetonitrile to 67 % acetonitrile in 0 . 1 % tfa , over a 40 min period . absorbance was monitored at 220 nm and peak protein fractions were collected manually . the peak fractions were then assayed for bioactivity according to example 5 . two peaks demonstrated the ability to inhibit cell proliferation . upon routine amino acid sequencing , the earlier - eluting , bioactive peak was found to be cpf - 4 , and the later - eluting , bioactive peak was found to be mpf - 4 . primary retinal capillary endothelial cell cultures were prepared in substantial accordance with the procedure described in buzney et al ., retinal vascular endothelial cells and pericytes : differential growth characteristics in vitro , invest . ophthalmol . visual sci . 24 : 470 - 483 ( 1983 ) and separated from contaminating cells as described in voyta et al ., identification and isolation of endothelial cells based on their increased uptake of acetylated - low density lipoprotein , j . cell biol . 99 : 2034 - 2040 ( 1981 ). alternatively , bovine heart endothelial cells were obtained ( american type culture collection ; rockville , md . 20852 ) for use in the assay . irrespective of source , the endothelial cells were seeded into 24 well tissue culture plates at a cell density of 10 , 000 cells / well in dulbecco &# 39 ; s modified eagle medium ( gibco ; grand island , n . y .) supplemented with 5 % bovine serum albumin , 1 % penicillin - streptomycin , 1 % l - glutamine , and 20 ng / ml fibroblast growth factor . immediately after seeding the cells , various amounts of pf - 4 ( sigma chemical co . ; st . louis , mo . 63178 ), mpf - 4 , or cpf - 4 ( isolated as describe in the above examples ) were added to individual growth wells . mpf - 4 and cpf - 4 were tested at final concentrations ranging from 0 . 001 to 1 μg / ml . for comparison , native pf - 4 was tested over a range of 0 . 001 to 3 μg / ml , and supplemented medium alone served as the negative control . the endothelial cell cultures were allowed to grow for four days at 37 ° c ., 5 % co 2 in a humidified tissue culture incubator . the cultures were then harvested individually by trypsinization and counted using a zm - coulter counter ( coulter electronics . inc . ; opa locka , fla . 33054 ). the results were plotted in fig1 and each point on the graph represented the average of 4 data points ; ie one growth well per data point . the results showed that pf - 4 inhibited endothelial cell proliferation and had an ic 50 of approximately 800 - 1000 ng / ml ( approximately 130 nm ). these results correlated well with recent studies published on the antiproliferative activity of recombinant pf - 4 ( science , 247 : 77 - 79 ( 1990 )). the data also showed that under identical conditions , both mpf - 4 and cpf - 4 were more potent inhibitors of endothelial cell proliferation . mpf - 4 demonstrated an ic 50 of 30 - 50 ng / ml ( approximately 7 nm ), and cpf - 4 showed an ic 50 of approximately 150 ng / ml ( 20 nm ). the inhibitory concentration for mpf - 4 is close to the physiological range of pf - 4 found in human plasma ( id .). __________________________________________________________________________ # sequence listing - ( 1 ) general information :- ( iii ) number of sequences : 2 - ( 2 ) information for seq id no : 1 :- ( i ) sequence characteristics :# acids ( a ) length : 54 amino ( b ) type : amino acid ( c ) strandedness : single ( d ) topology : linear - ( ii ) molecule type : protein - ( xi ) sequence description : seq id no : 1 :- ser gln val arg pro arg his ile - # thr ser leu glu val ile lysala # 15 - gly pro his cys pro thr ala gln - # leu ile ala thr leu lys asngly # 30 - arg lys ile cys leu asp leu gln - # ala pro leu tyr lys lys ileile # 45 - lys lys leu leu glu ser 50 - ( 2 ) information for seq id no : 2 :- ( i ) sequence characteristics :# acids ( a ) length : 16 amino ( b ) type : amino acid ( c ) strandedness : single ( d ) topology : linear - ( ii ) molecule type : protein - ( xi ) sequence description : seq id no : 2 :- glu ala glu glu asp gly asp leu - # gln cys leu cys val lys thrthr # 15__________________________________________________________________________
the present invention is based of the discovery of two modified forms of human platelet factor - 4 , herein named mpf - 4 and cpf - 4 , which were isolated from serum free culture medium of lipopolysaccharide - stimulated peripheral blood leukocytes . amino acid sequence determination revealed that mpf - 4 shares homology with platelet factor - 4 beginning at n - terminal residue 17 . cpf - 4 consists of mpf - 4 disulfide bonded to the 16 n - terminal residues of platelet factor - 4 . both mpf - 4 and cpf - 4 are potent inhibitors of endothelial cell proliferation , approximately 10 - 100 fold more potent than native or recombinant platelet factor - 4 , making them useful in the treatment of angiogenic diseases .