The present invention provides a pharmaceutical composition containing albumin-binding arginine deiminase (AAD) fusion protein for treating cancer or other arginine-dependent diseases. The AAD fusion protein can be purified from both soluble and insoluble fractions of crude proteins, binds to human serum albumin (HSA) or animal serum albumin and has its high activity with longer half life for efficient depletion of arginine in cancer cells. The specific activities of wild-type ADI and AAD fusion protein in the present invention are about 20 and about 19 U/mg (at physiological pH 7.4), respectively. The composition can be used alone or in combination with at least one chemotherapeutic agent to give a synergistic effect on cancer treatment and/or inhibiting metastasis. The AAD fusion protein can also be used as a component for detection and quantitative analysis of arginine in a testing kit for various samples including blood, food and analytical samples.
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1. A method of treating a cancer or inhibiting arginine-dependent tumor growth in a subject comprising administering an albumin-binding arginine deiminase fusion protein to the patient weekly or biweekly to reduce the availability of circulating arginine, wherein said albumin-binding arginine deiminase fusion protein comprises a first portion comprising one or two albumin-binding domain(s) fused to a second portion comprising arginine deiminase to form the albumin-binding arginine deiminase fusion protein, and one or more linker molecules; the first portion being positioned far from active site of the second portion by said linker molecule such that the albumin-binding arginine deiminase fusion protein retains the activity of arginine deiminase and binds serum albumin with neither function of one portion of the fusion protein being interfered with by the other portion of the fusion protein, wherein said albumin-binding arginine deiminase fusion protein comprises a sequence selected from seq id NO: 36, 37, 38, 39, 40 or 41, and wherein said cancer consists essentially of is selected from the group consisting of pancreatic cancer, leukemia, melanoma, head and neck cancer, colorectal cancer, lung cancer, breast cancer, liver cancer, nasopharyngeal cancer, esophageal cancer, prostate cancer, stomach cancer, cervical cancer and brain cancer.
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The present application
In one embodiment, the AAD fusion protein of the present invention has a specific activity of about 19 U/mg at pH 7.4 and 37° C., which is comparable to the activity of wild-type ADI. There are many advantages of using the AAD fusion protein of the present invention over wild-type ADI as enzyme of the testing kit, such as (1) simple production method, (2) longer shelf-life and (3) higher solubility. For wild-type ADI, it is usually insoluble and difficult for purification. For our AAD fusion protein, it can be prepared both soluble and insoluble forms.
The term “cancer stem cell” refers to the biologically distinct cell within the neoplastic clone that is capable of initiating and sustaining tumor growth in vivo (i.e. the cancer-initiating cell).
Arginine is a semi-essential amino acid for humans and other mammals. It can be synthesized from citrulline via a two step process catalyzed by urea cycle enzymes argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL). Arginine can be metabolized to ornithine by the enzyme arginase, and ornithine can be converted to citrulline by ornithine carbamoyltransferase (OTC) in the mitochondria. The citrulline can be utilized to synthesize arginine again. Normal cells do not typically require an exogenous supply of arginine for growth because of the abundant catalytic activity of ASS and ASL. In contrast, many types of cancers do not express ASS and are therefore auxotrophic for arginine. Their growth is solely dependent on arginine from circulation. Therefore, targeting circulating arginine by using arginine-degrading enzymes is a feasible strategy to inhibit ASS-negative tumor growth.
Arginine can be degraded by arginine deiminase (ADI). ADI converts arginine to citrulline and ammonia, the metabolites of the urea cycle. Unfortunately, ADI can only be found in prokaryotes e.g. Mycoplasma sp. There are many problems associated with the isolation and purification of arginine deiminase from prokaryotes. ADI isolated from Pseudomonas putida failed to exhibit efficacy in vivo because of its low enzymatic activity in neutral pH. ADI produced from Escherichia coli is enzymatically inactive and subsequently requires multiple denaturation and renaturation process which raised the subsequent cost of production. The plasma half-life of the native form of ADI is short (˜4 hours) upon injection into human circulation [Ensor et al., Cancer Res. 62:5443-5450 (2002); Izzo et al., J. Clin. Oncol. 22:1815-1822 (2004)]. These shortcomings can be partially remedied by pegylation. Among various forms of pegylated ADI, ADI bound with PEG (molecular weight 20,000) via succinimidyl succinate (ADI-PEG 20) has been found to be an efficacious formulation. However, the activity of ADI after pegylation is greatly decreased (by ˜50%) [Ensor et al., Cancer Res. 62:5443-5450 (2002); Wang et al., Bioconjug. Chem. 17:1447-1459 (2006)]. Also, the succinimidyl succinate PEG linker can easily be hydrolyzed and detached from the protein, causing immunogenic problems after a short period of use in the body. Therefore, there is a need for improved cancer-treatment compositions, particularly, improved cancer-treatment compositions with enhanced activity.
ADI isolated from P. putida failed to exhibit efficacy in vivo because it had little enzyme activity at a neutral pH and was rapidly cleared from the circulation of experimental animals. ADI derived from Mycoplasma arginini is described, for example, by Takaku et al, Int. J. Cancer, 51:244-249 (1992), and U.S. Pat. No. 5,474,928. However, a problem associated with the therapeutic use of such a heterologous protein is its antigenicity. The chemical modification of ADI from Mycoplasma arginini, via a cyanuric chloride linking group, with polyethylene glycol (PEG) was described by Takaku et al., Jpn. J. Cancer Res., 84:1195-1200 (1993). However, the modified protein was toxic when metabolized due to the release of cyanide from the cyanuric chloride linking group. In contrast, even for the ADI-PEG20, the PEG linker can easily be hydrolyzed and detached from the protein, causing immunogenic problems after a short period of use in the body. Therefore, there is a need for compositions which degrade non-essential amino acids and which do not have the problems associated with the prior art.
In many types of cancer including melanoma, pancreatic, colon, leukemia, breast, prostate, renal cell carcinoma and liver cancers, cancer cells are auxotrophic for arginine since they lack of expression of argininosuccinate synthetase (ASS), making them excellent targets for arginine depletion therapy. In this invention, albumin-binding arginine deiminase (AAD) fusion proteins have high activity with long half-lives for efficient depletion of arginine in cancer cells.
The size of the monomer for ADI is on the order of 45 kDa and it exists as dimer (on the order of 90 kDa) [Das et al., Structure. 12:657-667 (2004)]. A design for construction of an AAD fusion protein is shown in
The design and amino acid sequence for (A) native Mycoplasma arginini ADI protein (SEQ ID NO: 23), (B) different AAD fusion proteins originated from the Mycoplasma arginini ADI (SEQ ID NO: 36-40) and (C) AAD fusion protein originated from the Bacillus cereus ADI (SEQ ID NO: 41) are shown in
On the other hand, a novel AAD fusion protein is also created by the use of intein-fusion proteins and expressed protein ligation (
Importantly, AAD fusion proteins can be produced and purified in a convenient manner. For example, an AAD fusion protein is successfully expressed and purified from E. coli both in soluble fraction and insoluble fraction, and this result is shown in
The pharmaceutical composition of the present invention contains AAD fusion protein with high activity for depleting arginine in tumor cells for cancer treatment. The specific activity of the purified AAD fusion protein is found to be similar to that of the wild-type ADI. The inhibitory effect of the AAD fusion protein on a panel of human cancer cell lines is therefore examined using MTT assay. Different cancer cells are seeded in 96-well plates and allowed to grow for 24 h for acclimatization. The cells are then incubated with 0-10 μg/ml of AAD for 72 hours. IC50 is the half maximal inhibitory concentration, that is, it represents the concentration of AAD fusion protein that is required for 50% inhibition of a cancer cell line. The IC50 is a measure of the effectiveness of a drug. The IC50 of AAD fusion protein (amino acid sequence is shown in SEQ ID NO: 40,
TABLE 1
Cancer cell line
IC50 of AAD
(argininosuccinate synthetase-negative, ASS−ve)
(μg/ml)
A375 (human melanoma)
0.104
SK-mel-28 (human melanoma)
1.92
PancI (human pancreatic cancer)
0.043
Mia-paca-2 (human pancreatic cancer)
0.010
Sk-hep1 (human liver cancer)
>10
C-33A (human cervical cancer)
0.058
HCT116 (human colorectal cancer)
0.211
MDA-MB-231 (human breast cancer)
0.173
22Rv1 (human prostate cancer)
0.235
Jurkat (human leukemia)
0.379
For the albumin binding study, the present invention has demonstrated successfully that the engineered AAD fusion protein can bind to human serum albumin (HSA) or other animal serum albumin similar to HSA.
No commercial products show high efficacy when compared to the AAD fusion protein-containing pharmaceutical composition prepared in this invention. For uses in cancer treatment, the AAD fusion protein-containing pharmaceutical composition of the present invention serves as an anticancer agent to deplete the arginine in tumor tissues. AAD fusion protein is a good candidate to be used in combination with other molecular targeting or cytotoxic agents.
The AAD fusion protein in the present invention can also be used as a component in a testing kit for detection of arginine in different samples. AAD has a small Km value; it indicates the high affinity for the substrate (arginine). Therefore, the rate will approach the maximum reaction rate more quickly. The AAD fusion protein can be used to testing arginine level (1) in cancer patients, (2) in a food sample, and (3) in cell culture.
The following examples are provided by way of describing specific embodiments of this invention without intending to limit the scope of this invention in any way.
Several of the Examples below relate to methods of making an albumin-binding arginine deiminase fusion protein. Various techniques can be used including cloning and intein-mediated protein ligation. As used herein, the term “cloning” is broadly used and comprises constructing a fusion gene coding for the albumin-binding arginine deiminase fusion protein, inserting the fusion gene into a vector, inserting the vector into a host organism and expressing a protein that includes an albumin-binding arginine deiminase fusion protein. Numerous variants on this technique can be performed and still fall within the cloning contemplated by the present invention.
The gene coding for ABD is constructed by two rounds of PCR. In the first round, the PCR reaction mixture (total volume of 25 μl) contains the following materials:
1×iProof PCR buffer (Bio-Rad)
50 μM dNTP mixture
0.5 unit of iProof DNA Polymerase (Bio-Rad)
10 nM of each of the following oligos
ABD-F1 forward primer (SEQ ID NO: 01):
5′-CATGATGCGAATTCCTTAGCTGAAGCTAAAGTCTT
AGCTAACAGAGAACT-3′
ABD-R2 reverse primer (SEQ ID NO: 02):
5′-TAGTCACTTACTCCATATTTGTCAAGTTCTCTGTT
AGCTAAGACTTTAGC-3′
ABD-F3 forward primer (SEQ ID NO: 03):
5′-GAACTTGACAAATATGGAGTAAGTGACTATTACAA
GAACCTAATCAACAA-3′
ABD-R4 reverse primer (SEQ ID NO: 04):
5′-TACACCTTCAACAGTTTTGGCATTGTTGATTAGGT
TCTTGTAATAGTCAC-3′
ABD-F5 forward primer (SEQ ID NO: 05):
5′-GCCAAAACTGTTGAAGGTGTAAAAGCACTGATAGA
TGAAATTTTAGCTGC-3′
ABD-R6 reverse primer (SEQ ID NO: 06):
5′-AGCTACGATAAGCTTAAGGTAATGCAGCTAAAATT
TCATCTATCAGTG-3′
The following PCR program is used:
98° C. 30 s; 20 cycles of {98° C. 10 s, 50° C. 20 s, 72° C. 20 s}
In the second round of PCR, the PCR mixture (total volume of 50 μl) contains the following materials:
1×iProof PCR buffer (Bio-Rad);
50 μM dNTP mixture;
1 μl of PCR reactant as DNA template from the first round;
1 unit of iProof DNA Polymerase (Bio-Rad);
200 nM of each of the following oligos:
ABD-F7 forward primer (SEQ ID NO: 07):
5′-CATGATGCGAATTCCTTAGCTGAAGCTAAAGTCTT
AGCTAACAGAGAACT-3′
ABD-R8 reverse primer (SEQ ID NO: 08):
5′-AGCTACGATAAGCTTAAGGTAATGCAGCTAAAATT
TCATCTATCAGTG-3′
The following PCR program is used:
98° C. 30 s; 35 cycles of {98° C. 10 s, 60° C. 20 s, 72° C. 20 s}; 72° C. 5 min
A PCR product containing the DNA sequence of ABD (169 bp) is obtained and purified by Qiagen DNA Gel Extraction Kit for cloning purpose.
In the first PCR, the PCR mixture (total volume of 50 μl) contains the following materials:
1×iProof PCR buffer (Bio-Rad);
50 μM dNTP mixture;
25 ng of Mycoplasma arginini genomic DNA;
1 unit of iProof DNA Polymerase (Bio-Rad);
200 nM of each of the following oligos:
ADINde-F forward primer (SEQ ID NO: 09):
5′-ATCGATCGATGTCTGTATTTGACAGTAAATTTAAAG
G-3′
ADIhis-R reverse primer (SEQ ID NO: 10):
5′-AGCTAAGGAATTCGCATCATGATGGTGATGGTGGTGG
CTACCCCACTTAAC-3′
The following PCR program is used:
98° C. 1 min; 35 cycles of {98° C. 10 s, 50° C. 20 s, 72° C. 40 s}; 72° C. 5 min
A PCR product of 1280 bp long is obtained and purified by Qiagen DNA Gel Extraction Kit. After that, the second PCR is performed. The PCR mixture (total volume of 50 μl) contains the following materials:
1×iProof PCR buffer (Bio-Rad);
50 μM dNTP mixture;
10 ng of the 1280 bp PCR product;
10 ng of the 169 bp PCR product;
1 unit of iProof DNA Polymerase (Bio-Rad);
200 nM of each of the following oligos:
ADINde-F forward primer (SEQ ID NO: 11):
5′-ATCGATCGATGTCTGTATTTGACAGTAAATTTAAAG
G-3′
ABD-R10 reverse primer (SEQ ID NO: 12):
5′-AGCTACGATAAGCTTAAGGTAATGCAGCTAAAATTT
CATCTATCAGTG-3′
The following PCR program is used:
98° C. 1 min; 35 cycles of {98° C. 10 s, 50° C. 20 s, 72° C. 45 s}; 72° C. 5 min
A PCR product of 1428 bp is obtained and purified by Qiagen DNA Gel Extraction Kit. Then it is digested with restriction enzymes NdeI and HindIII, and ligated to plasmid pREST A (Invitrogen) that is predigested with the same enzymes. The ligation product is then transformed into E. coli BL21 (DE3) cells. The sequence of the constructed fusion gene is confirmed by DNA sequencing.
The construction of His-ABD-PolyN-ADI (SEQ ID NO: 40, in
Primers involved in construction of His-ABD-PolyN-ADI:
hisABDNde-F forward primer (SEQ ID NO: 13):
5′-GGAGATATACATATGCATCATCACCATCACCATGATGAAG
CCGTGGATG-3′
ABDnn-R1 reverse primer (SEQ ID NO: 14):
5′-TTGTTATTATTGTTGTTACTACCCGAAGGTAATGCAGCTA
AAATTTCATC-3′
ABDn-R2 reverse primer (SEQ ID NO: 15):
5′-AGAACCGCCGCTACCATTGTTATTATTGTTGTTACTACCC
GA-3′
ADln-F forward primer (SEQ ID NO: 16):
5′-AATAATAACAATGGTAGCGGCGGTTCTGTATTTGACAGTA
AATTTAAAGG-3′
ADIBam-R reverse primer (SEQ ID NO: 17):
5′-TAGATCAATGGATCCTTACCACTTAACATCTTTACGTGAT
AAAG-3′
In the first round of PCR, 50 μl of reaction volume containing the known concentration of components are prepared in two PCR tubes. In each of the tubes, dNTP, iProof buffer (BIO-RAD), iProof DNA polymerase (BIO-RAD), primers and DNA template are mixed and added up to 50 μl by ddH2O. The DNA template used in the reaction is a pET3a vector containing the gene of ADI from Mycoplasma arginini with a removal of an internal NdeI site mutation without altering the protein sequence of the ADI gene.
The two reaction tubes contain the primer mixtures of (A) 10 pmol hisABDNde-F (SEQ ID NO: 13), 0.5 pmol ABDnn-R1 (SEQ ID NO: 14) and 10 pmol ABDn-R2 (SEQ ID NO: 15); and (B) 10 pmol ADIn-F (SEQ ID NO: 16) and 10 pmol ADIBam-R (SEQ ID NO: 17), respectively.
The PCR program is set according to the recommended steps in the manual with an annealing and extension temperature (time) at 50° C. (20 s) and 72° C. (40 s), respectively. The two products generated by PCR with the size of 237 bp and 1278 bp. The products are extracted and applied as template for the next round of PCR.
In the second overlapping step, the reaction mixture is prepared in a similar way to the first round except the template used was the mixture of 1 pmol of the 237 bp PCR product and 1 pmol of the 1278 bp PCR product from the first round PCR. Primers used are changed to 10 pmol hisABDNde-F (SEQ ID NO: 13) and 10 pmol ADIBam-R (SEQ ID NO: 17).
The annealing and extension temperature (time) are 50° C. (20 s) and 72° C. (60 s), respectively. A PCR product with the size of 1484 bp is generated from the reaction. The PCR product is purified and digested with NdeI and BamHI and then ligated into the pre-digested pET3a plasmid. The ligated product is then transformed into E. coli BL21 (DE3) for the production of recombinant protein.
The construction of His-ABD-PolyN-bcADI (SEQ ID NO: 41, in
Primers involved in construction of His-ABD-PolyN-bcADI:
hisABDNde-F2 forward primer (SEQ ID NO: 18):
5′-GGAGATATACATATGCATCATCACCATCACCATGATGAAGC
CGTGGATG-3′
bcABDnn-R1 reverse primer (SEQ ID NO: 19):
5′-TTGTTATTATTGTTGTTACTACCCGAAGGTAATGCAGCTAA
AATTTCATC-3′
bcABDn-R2 reverse primer (SEQ ID NO: 20):
5′-TTTACCGCCGCTACCATTGTTATTATTGTTGTTACTACCCG
A-3′
bcADln-F forward primer (SEQ ID NO: 21):
5′-AATAATAACAATGGTAGCGGCGGTAAACATCCGATACATGT
TACTTCAGA-3′
bcADIBam-R reverse primer (SEQ ID NO: 22):
5′-TAGATCAATGGATCCCTAAATATCTTTACGAACAATTGGCA
TAC-3′
In the first round of PCR, 50 μl of reaction volume containing the known concentration of components are prepared in two PCR tubes. In each of the tubes, dNTP, iProof buffer (BIO-RAD), iProof DNA polymerase (BIO-RAD), primers and DNA template are mixed and added up to 50 μl by ddH2O. The DNA template used in the reaction is a pET3a vector containing the gene of ADI from Bacillius cereus with a removal of an internal NdeI site mutation without altering the protein sequence of the ADI gene.
The two reaction tubes contain the primer mixtures of (A) 10 pmol hisABDNde-F2 (SEQ ID NO: 18), 0.5 pmol bcABDnn-R1 (SEQ ID NO: 19) and 10 pmol bcABDn-R2 (SEQ ID NO: 20); and (B) 10 pmol bcADIn-F (SEQ ID NO: 21) and 10 pmol bcADIBam-R (SEQ ID NO: 22), respectively. The PCR program is set according to the recommended steps in the manual with an annealing and extension temperature (time) at 50° C. (20 s) and 72° C. (40 s), respectively. The two products are generated by PCR with the size of 237 bp and 1250 bp. The products are extracted and applied as template for the next round of PCR.
In the second overlapping step, the reaction mixture is prepared in a similar way to the first round except the template used is the mixture of 1 pmol of the 237 bp PCR product and 1 pmol of the 1250 bp PCR product from the first round PCR. Primers used are changed to 10 pmol hisABDNde-F2 (SEQ ID NO: 18) and 10 pmol bcADIBam-R (SEQ ID NO: 22).
The annealing and extension temperature (time) are 50° C. (20 s) and 72° C. (60 s), respectively. A PCR product with the size of 1512 bp is generated from the reaction. The PCR product is purified and digested with NdeI and BamHI and then ligated into the pre-digested pET3a plasmid. The ligated product is then transformed into E. coli BL21 (DE3) for the production of recombinant protein.
(3a) Expression of the AAD Fusion Protein by Shake-Flask Method
For preparing the seed culture, the strain E. coli BL21 (DE3) carrying the plasmid encoding the AAD fusion protein (
(3b) Expression of the AAD Fusion Protein by Fermentation Method
For the seed culture, the aliquot of bacteria stock is inoculated into 50 ml of seeding medium (containing 1.5 g of yeast extract and 0.25 g of NaCl) with ampicillin and grown at 30° C. for 16 hr with continuous shaking at 250 rpm. The seed culture is then added to 1.25 L of medium (pH 7.4, containing yeast extract, tryptone, Na2HPO4, KH2PO4, (NH4)2SO4, glycerol, glucose, MgSO4.7H2O, Thiamine-HCl and CaCl2) supplement with trace element in the BIOSTAT fermentor system and grown at 28° C. Until the OD600 of the culture reaches ˜20, IPTG is added to a final concentration of 0.2 mM. The culture is further incubated for 16 hr. During incubation, 500 ml of feeding medium (pH 7.4, containing yeast extract, tryptone, NH4Cl, (NH4)2SO4, glycerol and MgSO4.7H2O) supplement with trace element were applied at 0.5 ml/min. Aeration is regulated in order to maintain 20% of air saturation by varying the speed of stirring from 500 rpm to 2000 rpm. The bacteria are harvested by centrifugation. The cells are lysed by sonication or high pressure homogenizer.
(3c) Purification of the AAD Fusion Protein
The soluble portion is collected after centrifugation. The fusion protein (containing a His tag) is then purified by nickel affinity chromatography. TABLE 2 shows that cultivation temperature is an important factor in affecting the solubility of AAD fusion protein (amino acid sequence is shown in SEQ ID NO: 40,
For isolating the soluble fraction of AAD fusion protein, the cell pellet is resuspended in 25 ml of 10 mM sodium phosphate buffer, pH 7.4. The cells are lysed by sonication or high pressure homogenizer. The soluble portion is collected after centrifugation. The AAD fusion protein (contains a His tag or without His tag) is then purified by nickel affinity chromatography and/or ion-exchange columns.
For isolating the insoluble fraction of AAD fusion protein, the cell pellet is resuspended in 25 ml of 20 mM Tris-HCl, pH 7.4, 1% TRITON X-100. The cells are lysed by sonication. The insoluble portion (inclusion bodies) is collected by centrifugation. The protein is unfolded by resuspending in 10 ml of 20 mM Tris-HCl, pH 7.4, 6 M Guanidine HCl, and vortexed until it becomes soluble. The protein is refolded by adding the unfolded protein solution drop by drop into a fast stiffing solution of 100 ml of 20 mM Sodium phosphate buffer, pH 7.4. The insoluble materials are removed by centrifugation. Salting out of the protein is performed by adding solid ammonium sulphate powder into the supernatant to achieve 70% saturation. The insoluble portion is collected by centrifugation and it is resuspended in 10 ml of 20 mM sodium phosphate buffer. The AAD fusion protein (contains a His tag or without His tag) is then purified by nickel affinity chromatography and/or ion-exchange columns.
TABLE 2
AAD
1
2
3
Cultivation
30
20
37
temperature (° C.)
Yield (mg)/
~0.66
~12.0
~7.0
250 ml culture
solubility
50% soluble
90% soluble
90% inclusion
body
IC50 (μg/ml) on
0.10
0.68
0.23
A375 cells
“90% inclusion body” means 90% of the AAD fusion protein produced in the bacterial cells are not soluble.
The yield and the enzyme activity of AAD fusion protein from shake-flask method and fermentation method are shown in TABLE 3.
TABLE 3
Activity
AAD Yield (mg/L)
(U/mg)
Shake-flask method
~10
~9
Fermentation method
~42
~19
To determine the enzyme activity for wild-type ADI and AAD fusion protein in the present invention, the diacetyl monoxime (DAM)-thiosemicarbazide (TSC) assay for citrulline detection is used. The reaction is shown below.
L-Arginine
argininedeiminase(ADI)orAADfusion>L-Citrulline+Ammonia
This assay is run by adding sample to a color reagent, which is made by mixing acidic ferric chloride solution with DAM-TSC solution. Briefly, enzyme is incubated with 20 mM arginine, 10 mM sodium phosphate pH 7.4 for 5 min at 37° C. The reaction mixture is heated at 100° C. for 5 mM to develop the color and read at 540 nm (light path=1 cm). A standard curve is constructed using various concentrations of citrulline. One unit of the ADI native enzyme is the amount of enzyme activity that converts 1 μmol of arginine to 1 μmol of citrulline per minute at 37° C. under the assay conditions. The specific activities of wild-type ADI, pegylated ADI (Ensor et al., Cancer Res. 62:5443-5450, 2002) and AAD fusion protein in the present invention are about 20, 15 and 19 U/mg (at pH 7.4, physiological pH), respectively. The specific activities for wild-type ADI and AAD fusion protein at different pH values (in a range from pH 5.5 to 9.5) are also determined, and the optimum pH is at 6.5. Therefore, the results indicate that AAD fusion protein depletes arginine efficiently which is even better than pegylated ADI, as the fusion with albumin-binding protein does not affect enzyme activity of ADI.
The Michaelis constant Km is the substrate concentration at which the reaction rate is at half-maximum, and is an inverse measure of the substrate's affinity for the enzyme. A small Km indicates high affinity for the substrate, and it means that the rate will approach the maximum reaction rate more quickly. For determination of the enzyme kinetics or Km value, the activity of wild-type ADI and AAD fusion protein are measured under different concentration of substrate arginine (2000 μM, 1000 μM, 500 μM, 250 μM, 125 μM, 62.5 μM) at pH 7.4. The measured Km values of the AAD fusion protein shown in
Culture medium DMEM is used to grow the human melanoma A375 & SK-mel-28 and pancreatic cancer Pancl & Mia-paca-2 cell lines. The EMEM medium is used to culture the human liver cancer SK-hep, cervical cancer C-33A and colorectal cancer HCT116 cell lines. The RPMI-1640 medium is used to culture the human breast cancer MDA-MB-231, prostate cancer 22Rv1 and leukemia Jurkat cell lines. Cancer cells (2-5×103) in 100 μl culture medium are seeded to the wells of 96-well plates and incubated for 24 hours. The culture medium is replaced with medium containing 0-10 μg/ml of AAD fusion protein. The plates are incubated for an additional 3 days at 37° C. in an atmosphere of 95% air/5% CO2. MTT assay is performed to estimate the number of viable cells in the culture according to manufacturer's instructions. The amount of enzyme needed to achieve 50% inhibition of cell growth is defined as IC50.
As shown in TABLE 1, the results indicate that AAD fusion protein depletes arginine efficiently and inhibits the growth of various types of human cancer cell lines in in vitro tissue culture studies. For example, human melanoma, human breast cancer, human colorectal cancer, human pancreatic cancer, human liver cancer, human prostate cancer, human leukemia and human cervical cancer, all have low values of IC50 (see TABLE 1), as these cancer types are all inhibited by AAD fusion protein readily. As determined from the in vitro_data, AAD fusion protein would inhibit all cancer types that are arginine-dependent, for example, the argininosuccinate synthetase-negative (ASS−ve) cancers.
Balb/c mice (5-7 weeks) are used in this study and they are allowed to acclimatize for a week before the experiment. Mice (n=3) are separated into four groups and injected with 0, 100, 500 or 1000 μg of AAD fusion protein (SEQ ID NO: 40,
As shown in
Nude balb/c mice (5-7 weeks) are used in this study and they are allowed to acclimatize for a week before the experiment. Mice are inoculated subcutaneously with 2×106 cancer cells in 100 μl of fresh culture medium. Ten days later, the mice are randomly separated into control and treatment group. Control group receives 100 μl PBS and treatment group receives 100 μl AAD fusion protein (amino acid sequence is shown in SEQ ID NO: 40,
Nude balb/c mice (4-6 weeks) are used and they are allowed to acclimatize for a week before the treatment. Mice are inoculated subcutaneously with 2×106 cancer cells in 100 μl PBS. Ten days later, the mice are randomly separated into control and treatment groups. Control group receives 100 μl PBS and treatment group receives 200 μg AAD fusion protein (amino acid sequence is shown in SEQ ID NO: 40,
At Day 5, Day 12 and Day 19, the plasma arginine level is significantly decreased respectively after the weekly administration of the AAD fusion protein. Comparing the plasma arginine levels between Day 0, Day 7 and Day 14, the levels at Day 7 and Day 14 are relatively lower than that at Day 0, revealing that weekly administration of AAD fusion protein can decrease the overall plasma arginine levels over the time course. The tumor size in the weekly treatment group is lower than that in control at the end of the time course, revealing that the weekly administration of AAD fusion protein can reduce the tumor size of the xenograft in the disease mouse model. The difference in the tumor size between control and weekly treatment group is about 20% at Day 30.
The reduction in plasma arginine level is more significant in the biweekly treatment group than that in the weekly treatment group. The biweekly administration of AAD fusion protein does not affect the body weight of the mice over a 35-day time course as compared to the control. In conclusion, biweekly administration of AAD fusion protein in 400 μg per week (16 mg/kg/week/mouse) is more effective in completely suppressing plasma arginine level than weekly administration. Using the conversion of animal doses to human equivalent doses (HED) based on body surface area mentioned in “Guidance for Industry and Reviewers—Estimating the safe starting dose in clinical trials for therapeutics in adult healthy volunteers (2002)”, human dose of the AAD fusion protein is about 1.3 mg/kg/week.
Nude balb/c mice (4-6 weeks) are used and they are allowed to acclimatize for a week before the treatment. Mice are inoculated subcutaneously with 2×106 cancer cells in 100 μl of 1:1 PBS:Matrigel. Matrigel is used to augment the growth of tumors. Two weeks later, the mice are randomly separated into four groups of 4 animals in each group. Mice are intraperitoneally administered with PBS (control), AAD (5 U; twice a week), Gemcitabine, Gem (100 mg/kg; once a week) or AAD+Gem (a combination of both AAD and Gem) in 200 μl PBS. Tumor size is measured by caliper and tumor volume is calculated using formula: (length×width2)/2. Body weight is measured every week. After the mice are sacrificed by end of the time course, the tumors are excised and weighed. The tumor size in all treatment groups is significantly lower than that in control at the end of the time course, revealing that the administration of AAD fusion protein can reduce the tumor size of the xenograft in the disease mouse model (shown in
Nude balb/c mice (4-6 weeks) are used and they are allowed to acclimatize for a week before the treatment. Mice are inoculated subcutaneously with 3×106 cancer cells in 100 μl PBS. Two weeks later, the mice are randomly separated into four groups of 5 animals in each group. Mice are intraperitoneally administered with PBS (control), AAD (5 U; twice a week), Docetaxel, DTX (10 mg/kg; once a week) or AAD+DTX (a combination of both AAD and DTX) in 200 ul PBS. Tumor size is measured by caliper and tumor volume is calculated using formula: (length×width2)/2. Body weight is measured every week. After the mice are sacrificed by end of the time course, the tumors are excised and weighed.
In
Nude balb/c mice (4-6 weeks) are used and they are allowed to acclimatize for a week before the treatment. Mice are inoculated subcutaneously with 5×106 cancer cells in 100 μl of 1:1 PBS:Matrigel. Matrigel is used to augment the growth of tumors. Since the take rate of this cancer cell line is relatively low, when certain tumor xenograft reaches a suitable size, the tumor is excised and cut into various pieces (˜10 mm3), which are further transplanted to the back of another group of mice subcutaneously. Ten days later, the mice are randomly separated into two groups of 8 animals in each group. Mice are intraperitoneally administered with PBS (control) or AAD (5 U; twice a week) in 200 μl PBS. Tumor size is measured by caliper and tumor volume is calculated using the following formula: (length×width2)/2. Body weight is measured every week. At Day 28, the AAD fusion protein significantly inhibits the tumor growth when comparing to the control group (
AAD fusion protein of the present invention has a small Km, indicating the high affinity for the substrate (arginine). Therefore, the rate approaches the maximum reaction rate more quickly. To determine the concentration of arginine in a sample, AAD fusion protein in the present invention, the diacetyl monoxime (DAM)-thiosemicarbazide (TSC) assay for citrulline detection is used. The reaction is as follows: L-Arginine (of unknown concentration) is converted by AAD fusion protein to form L-Citrulline and Ammonia.
This assay is run by adding sample to a color reagent, which is made by mixing acidic ferric chloride solution with DAM-TSC solution. Briefly, arginine (in the sample, of unknown concentration) is incubated with 2-20 ng of the AAD fusion protein, and 10 mM sodium phosphate pH 7.4 for 5 mM at 37° C. The reaction mixture is heated at 100° C. for 5 mM to develop into pink color and read at 540 nm (light path=1 cm). A standard curve is constructed using various concentrations of citrulline. One unit of the AAD is the amount of enzyme activity that converts 1 μmol of arginine to 1 μmol of citrulline per minute at 37° C. under the assay conditions. This testing kit is very useful for the following applications:
For a cancer patient (human or animal), after treated with an arginine depleting drug, the arginine level (concentration) in blood should be very low or zero. A blood sample can be taken from the patient and then tested with this new testing kit based on the AAD fusion protein. After comparing to the standard curve (generated from standard solution plotted from known arginine concentration solutions), the exact arginine concentration of this blood sample of the patient can be measured. Therefore, this data helps monitor the progress of an arginine depletion treatment method. If the arginine level is too high (e.g. 200 micro-molar), more arginine depleting drug can be used on the patient to further keep the arginine at a lower or undetectable level so that the tumor can be inhibited by the systemic arginine depletion in the cancer patient.
For industrial or food manufacturing purposes, the arginine (amino acid) level of a particular food material or intermediate during the food processing step might need to be monitored and measured. This arginine testing kit by using the AAD fusion protein of the present invention can measure the exact arginine concentration of a food sample prepared in solution form in the laboratory. This testing kit can also be used in high throughput manner and applicable for industrial scale and mass production.
Nitric oxide (NO) is an important signaling molecule in cells and in the body. For many research projects on nitric oxide (NO) and cell culture studies, a lot of time a scientist would need to measure the amount or concentration of arginine (which is a substrate for making NO). This arginine testing kit by using the AAD fusion protein of the present invention can also be used for measuring the exact arginine concentration of any laboratory samples and/or analytical samples (e.g. for NO and cell culture studies).
Wong, Bing Lou, Kwok, Sui Yi, Leung, Yun Chung, Wai, Norman Fung Man
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