Abstract:
The present disclosure relates to a diagnostic marker for breast cancer, having thioredoxin-1 as an active ingredient, and to a diagnostic kit for breast cancer using the same. The thioredoxin-1 is overexpressed in human breast cancer tissue so as to enable the early diagnosis of breast cancer or the early prediction prognosis of breast cancer, and therefore has a valuable use as a diagnostic marker for breast cancer. The present disclosure further relates to a method for the diagnosis of breast cancer comprising measuring serum thioredoxin 1 level. In addition, the method is useful in the early diagnosis of breast cancer thanks to its high diagnostic sensitivity and selectivity.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application is a continuation-in-part of PCT/KR2011/004729 filed Jun. 29, 2011 and continuation-in-part of U.S. patent application Ser. No. 13/257,277 filed Sep. 16, 2011, which is a 371 of PCT/KR2009/001944 filed Apr. 15, 2009, which in turn claims the benefit of priority from Korean Patent Application 10-2009-0022291 filed Mar. 16, 2009, the contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a diagnostic marker for breast cancer, comprising thioredoxin-1 as an active ingredient, and a diagnostic kit for breast cancer using the same. The present invention further relates to a method for the diagnosis of breast cancer by measuring thioredoxin 1 levels in tissues and blood. 
     BACKGROUND OF THE INVENTION 
     Breast cancer is a malignant tumor originating from breast tissue, most commonly from the epithelium lining milk ducts or the lobules that supply the ducts with milk. Breast cancer is reported to occur at a higher rate in women of advanced countries than do other cancers. 
     Various etiologic factors for breast cancer are now being mentioned, including female hormones, cancer history, family history, lack of having borne a child, dietary habit, etc., without no clear relationship with these has been proven thus far. 
     In South Korea, breast cancer ranks second after stomach cancer in frequency and fifth after breast cancer, liver cancer, uterine cancer and lung cancer in mortality for women. Breast cancer cases of women in South Korea have rapidly increased every year as have those of Western countries. Recently, breast cancer cases in South Korea are reported to have rapidly increased. A survey report of the Statistics Korea has it that breast cancer cases exceeded uterine cervical cancer cases in 1998 and accounted for 16.1% of women&#39;s cancer cases in 2001, ranking first before stomach cancer. In addition, the incident rate of breast cancer was 11.1% between 2001 and 2002, which was greater than that of other cancers. Now, the high incident rate of breast cancer is thought to be associated with various factors. Among them are a low birthrate, breastfeeding for a short period of time, early menarche, late menopause, the westernization of dietary habits, and the pollution of living environment. Further, glandular tissue of women who had been stimulated by female hormones at rapidly increased frequency at the time of their physiologically active change was increased in sensitivity and these individuals may be confronted with a greater likelihood of being struck by breast cancer. 
     The incidence of breast cancer and the mortality from breast cancer in Korea are expected to increase for a significant period of time in the future in consideration of the trend of because of the westernization of living. As they grow, breast cancer cells, like other cancer cells, generally infiltrate adjacent tissues or metastasize into the lymph nodes. In most breast cancer cases, the patients did not have many detectable symptoms or they did not examine their breasts by themselves. Therefore, it is very important to effectively diagnose early breast cancer to reduce mortality from breast cancer. 
     To decrease the mortality from breast cancer, early diagnosis is the most important thing. It is also important to do an adjuvant therapy that is suitable in light of the prognosis after the primary initial treatment. For the diagnosis of breast cancer, various methods are used in combination. So far, breast self-examination has accounted for 70% of breast cancer cases. However, it is impossible to discriminate malignant breast tumors from benign tumors by giving breast self-examination. A number of breast cancer screening tests have been employed including X-ray mammography, ultrasound, fine-needle aspiration cytology, and magnetic resonance imaging. Eventually, biopsy is employed to diagnose breast cancer. Mammographic screening for breast cancer uses X-rays to examine the breast. Mammography is effective at determining whether breast tumors are benign or malignant and can detect hidden tumors. This method is one of the most effective techniques by which early breast cancer can be diagnosed before the detection of a lump by breast self-examination. However, mammography is disadvantageous in that diagnostic accuracy is lowered for a breast in which the mammary gland is highly developed or which is a small and dense breast with highly fibrous tissue, like the breasts of young women. In addition, there is a dispute waging about that more frequent mammograms run the risk of significantly increasing breast cancer because of the radiation. As an alternative to mammography, ultrasonography is employed. Ultrasonography can effectively discriminate cystis from lumps, but is ineffective in telling malignant tumors from benign tumors. Ultrasonography can effectively discriminate cystis from lumps, but is ineffective in telling malignant tumors (cancer) from benign tumors (non-cancer). In practical clinics, the finding of abnormalities requires the use of fine-needle aspiration and magnetic resonance imaging for more accurate diagnosis. Even these methods, however, cannot guarantee that malignant tumors (cancer) can be distinguished from benign tumors (non-cancer) although they can reveal morphological differences between normal and abnormal tissues. Ultimately, a biopsy is employed to diagnose breast cancer decisively. 
     To supplement such breast screening methods, attempts have been made to use blood tumor marker levels to diagnose breast cancer. Although studied for their values as diagnosis or prognosis factors, the application of conventional tumor markers is accompanied by limitations, and there are no officially recommended breast cancer markers. 
     Thioredoxin (Trx) was discovered as a coenzyme that donates a hydrogen ion to ribonucleotide reductase, an enzyme essential for DNA synthesis in  Escherichia coli . Characterized by the active site -Cys-Gly-Pro-Cys- (SEQ ID NO: 5) in which the two vicinal cysteine residues interchangeably exist between the oxidized form of a disulfide bond (S—S) and the reduced form of a dithiol (—SH—SH), Trx functions as an intracellular oxidoreduction controller. Thioredoxin (Trx) is a 12 kDa oxidoreductase thatis kept in the reduced state by thioredoxin reductase in a NADPH-dependent reaction. There are two kinds of mammal thioredoxins: thioredoxin 1 (Trx1) and thioredoxin 2 (Trx2). Thioredoxins act as electron donors to peroxidases so that, for example, toxic hydrogen peroxide can be eliminated. Also, thioredoxins provide electrons for ribonucleotide reductase. Thioredoxins plays a role in binding transcription elements to DNA in bacteria while they have an influence on the activity of NF-kB (nuclear transcription factor kB) in eukaryotes. Therefore, thioredoxins are associated with cell death and tumor cells, and play an important role in regulating the growth of tumor cells. Serving as a general disulfide oxidoreductase, thioredoxin facilitates the reduction of other proteins by a redox mechanism based on reversible reduction of a disulfide to two cysteine thiol groups, thereby recovering the normal function of the proteins. In mammalian cells, thioredoxin 1 and 2 are also involved in the regulation of nitric oxide levels and thus in cell death. Therefore, the enzymes are potentially important in conjunction with the onset of many diseases including inflammatory diseases, heart failure, cancer, etc. Immunohistochemical analysis with anti-thioredoxin antibodies revealed the expression of thioredoxins in cancer cells in various tissues such as the liver, colon, pancreas, and the uterine cervix, indicating the implication of thioredoxins in oncogenesis. 
     There has been a need for a diagnostic marker and a method for breast cancer that allows the accurate diagnosis of early breast cancer and allows the prognosis of breast cancer to be made. Almost few studies have been done on the use of thioredoxin 1 as a diagnostic marker for breast cancer. 
     SUMMARY OF THE INVENTION 
     The present invention provides a diagnostic marker for breast cancer, comprising thioredoxin 1 as an active ingredient, and a diagnostic kit for breast cancer, using the same. The present invention also provides a method for diagnosing breast cancer comprising determining the thioredoxin 1 level in tissues and in blood. In addition, the method of the present invention is useful in the early diagnosis of breast cancer due to its high diagnostic sensitivity and selectivity. In one embodiment of the present invention, the blood is serum. Because blood, which is relatively easy to sample, is employed as a specimen, the method for diagnosing breast cancer comprising the thioredoxin 1 level in blood in accordance with the present invention is very simple and does not impose a load on patients compared to conventional methods that are directed to a biopsy. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a graph showing expression profiles of thioredoxin 1 transcript in 48 different human normal tissues selected from individuals of different ethnicity as measured by 96-well HMRT qPCR assay. 
         FIG. 2  is a graph showing mRNA levels of thioredoxin 1 and 2 in eight solid cancers (breast, colon, kidney, liver, lung, ovary, prostate, and thyroid) as measured by CSRT 96-I arrays. 
         FIG. 3  is of graphs showing mRNA levels of thioredoxin 1 and 2 in breast cancer (A) and levels of induction fold obtained therefrom (B). 
         FIG. 4  shows the induction fold of mRNA expression of thioredoxin 1 in human breast cancer as a scatter dot plot (A), the correlation between the mRNA expression of thioredoxin 1 and the progression of cancer as a box-and-whisker plot (B), and the induction fold of mRNA expression of thioredoxin in subdivided cancer (stage I, IIA, IIB, IIIA, IIIB, IIIC and IV) as a plot (C). 
         FIG. 5  shows the expression level of thioredoxin 1 in human breast cancerous tissues as measured by Western blot assay. 
         FIG. 6  shows the expression levels of thioredoxin 1 in four normal tissues and four cancerous tissues from different individuals, as measured by Western blotting assay. 
         FIG. 7  shows the expression levels of thioredoxin 1 in paired sets of breast tissue (paired normal and primary cancer from the same individual; paired primary and metastatic cancer from the same individual) and paired sets of other cancerous tissues (lung and colon), as measured by Western blotting assay. 
         FIG. 8  shows serum thioredoxin 1 levels in normal control and breast cancer patient groups, as measured by ELISA. 
         FIG. 9  shows serum thioredoxin 1 levels in the breast cancer group and other cancer groups (kidney cancer, lung cancer and colorectal cancer), as measured by ELISA. 
         FIG. 10  shows the comparison of serum thioredoxin level between the breast cancer group and the lung cancer group.  FIG. 10A  shows the comparison of serum thioredoxin 1 level in blood samples of normal (N(F/M)) and breast cancer patients (BC) groups.  FIG. 10B  shows the comparison of serum thioredoxin 1 level in the blood samples of normal (N(F/M)) and lung cancer patients (LC) groups.  FIG. 10C  shows the comparison of serum thioredoxin 1 level in blood samples of lung cancer patients (LC) and breast cancer patients (BC) groups. 
         FIG. 11  shows serum levels of thioredoxin 1 and the antioxidant proteins TXNDC1 and Grx3 in the breast cancer group. 
         FIG. 12  shows changes of serum thioredoxin 1 level with the progress of breast cancer and lung cancer. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The present invention provides a diagnostic marker for breast cancer, comprising thioredoxin 1 as an active ingredient. Also, the present invention provides a diagnostic kit for breast cancer, comprising an antibody against thioredoxin 1. Furthermore, the present invention provides a method for detecting thioredoxin 1 in breast tissues using an antibody to thioredoxin 1. 
     In one embodiment, the present invention provides a method for diagnosing breast cancer, comprising the thioredoxin level in tissues or in blood. 
     In another embodiment of the present invention, the expression levels of thioredoxin 1 in human normal tissue and cancerous tissue were examined. Thioredoxin 1 was found to be expressed at the lowest level in normal breast tissue among 48 different normal human tissues, and at a higher level in breast cancer tissue than in other cancerous tissue, as measured by qRT-PCR and Western blotting. In addition, the more progressed the cancer is, the higher the induction fold of mRNA expression of thioredoxin 1. Thus, the induction fold of mRNA expression of thioredoxin 1 becomes high in stage II˜IV breast cancer, particularly stage IV breast cancer, that is, metastatic breast cancer. Further, the induction fold of mRNA expression of thioredoxin 1 is closely associated with the malignancy of cancer as it increases with the progression of cancer. Therefore, the induction fold of mRNA expression of Thoredoxin 1 is associated with subdivision of cancer stages. Found to be overexpressed in human breast cancer tissues, as described above, thioredoxin 1 allows the diagnosis and prognosis of breast cancer and thus is useful as a diagnostic marker for breast cancer. 
     As elucidated in the Example section below, breast cancer patients were found to have significantly higher serum thioredoxin 1 levels than normal persons, as measured by ELISA. In addition, comparison between breast cancer and other cancers showed that significantly high thioredoxin 1 levels were detected in blood taken from breast cancer patients, compared to patients with other cancers. Moreover, the serum thioredoxin level exhibited a proportional correlation with the progress of breast cancer. 
     In one embodiment, the present invention provides a method wherein thioredoxin 1 levels in blood samples were measured to detect breast cancer. Because of employing blood as a specimen, it is relatively easy to sample. Therefore, the method for diagnosing breast cancer comprising the thioredoxin level in blood in accordance with the present invention is very simple and does not impose a load on the patients compared to conventional methods which are directed to a biopsy. In addition, the method of the present invention is useful in the early diagnosis of breast cancer thanks to its high diagnostic sensitivity and selectivity. 
     In another embodiment, the present invention provides a diagnostic kit for breast cancer, comprising an antibody against thioredoxin 1 which can be readily prepared using the markers of the present invention. 
     The diagnostic kit for breast cancer of the present invention may comprise an antibody specifically binding to thioredoxin 1, a secondary antibody conjugate with a label that can react with a substrate to cause a chromatic change, a substrate solution which develops a color upon reaction with the label, a washing buffer and a reaction stop buffer. 
     The label conjugated to the secondary antibody is preferably a coloring agent which can bring about a color change as it reacts with its substrate. Representative among them are HRP (horseradish peroxidase), alkaline phosphatase, colloid gold, fluorescein such as FITC (poly L-lysine-fluorescein isothiocyanate) and RITC (rhodamine-B-isothiocyanate), and dye. 
     As for the substrate solution, it is dependent on the label. Examples include TMB (3,3′,5,5′-tetramethyl bezidine), ABTS [2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)], and OPD (o-phenylenediamine). The coloring substrate is preferably provided in the form of a solution in buffer (0.1M NaOAc, pH 55). 
     Preferably, phosphate buffer, NaCl and Tween 20 are contained in the washing solution. More preferable is a solution (PBST) containing 0.02M phosphate buffer, 0.13M NaCl, and 0.05% Tween 20. After the antibody is allowed to react with the antigen, the antigen-antibody complex is treated with the secondary antibody conjugate, followed by immobilization and then washing 3˜6 times with the washing solution. A sulfuric acid solution ma be used to stop the enzymatic reaction. 
     Hither expression levels of thioredoxin 1 are detected in stage II˜IV breast cancer tissues than in stage I breast cancer or normal breast tissues. 
     Examples of the immobilizer include a nitrocellulose membrane, a PVDF (polyvinylidene difluoride) membrane, a 96-well plate formed of polyvinyl resin or polystyrene resin, and a slide glass. 
     The antigen-antibody binding reaction may be assayed using a typical method such as ELISA, radioimmunoassay (RIA), sandwich assay, Western blotting, immunoprecipitation immunohistochemical staining, immunofluorescence assay, enzyme-substrate coloring assay, and antigen-antibody aggregation. 
     In accordance with one embodiment of the present invention, the diagnosis or prognosis of breast cancer can be readily predicted with high accuracy by detecting the breast cancer marker with an antigen-antibody reaction using an antibody specifically binding to thioredoxin 1. For example, a protein preparation containing thioredoxin 1 is separated on SDS-PAGE, and transferred and fixed onto an immobilizer which is then treated with an antibody against thioredoxin 1 to determine the expression level of thioredoxin 1. That is, when the expression level of thioredoxin 1 in the breast tissue of interest is measured, the breast tissue is diagnosed with cancer or predicted to become cancerous when the thioredoxin 1 expression level is higher than that of normal breast tissue. 
     INDUSTRIAL APPLICABILITY 
     As described hitherto, the method based on thioredoxin 1 level in accordance with the present invention is convenient in diagnosing breast cancer because thioredoxin 1 is a useful marker for the early diagnosis of breast cancer thanks to its high sensitivity and specificity. 
     EXAMPLE 
     A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as limiting the present invention. 
     Example 1 
     qRT-PCR Assay 
     For expression profiling of human target genes, qRT-PCR (Quantitative real-time Polymerase Chain Reaction) arrays were used to conduct the following reactions. 
     Human Major 48 tissues real-time (HMRT) qPCR arrays, Cancer Survey real-time (CSRT 96-I) qPCR arrays, and Human Breast Cancer real-time (BCRT I-V) qPCR arrays, all purchased from OriGene (OriGene Technologies, Inc, Rockville, Md., USA) were used. Simultaneous examination of the expression of target genes in 48 different tissues was performed using the HMRT array, which consisted of panels of first-strand cDNA from human tissues selected from individuals of different ethnicity. Expression levels of target genes in eight different cancers (breast, colon, kidney, liver, lung, ovary, prostate, and thyroid) were measured using the CSRT array consisting of 12 samples from each cancer type with cancer stages varying from I to IV. Expression of target genes in breast cancer was examined using four different sets of arrays (BCRT I-IV) for 192 test samples and using the CSRT 96-I array for 12 test samples. In the 204 samples, cancer grading was distributed as follows: 19 as stage 0 (normal); 37 as stage I; 76 as stage II; 60 as stage III; and 12 as stage IV. The cancer tissue types consisted of ductal (n=154), lobular (n=13), metastatic (n=12), and other histological types of cancer (n=25), including medullary, mucinous, tubular, recurrent, and papillary. More clinicopathological information for each patient is described in OriGene&#39;s product sheet. 
     PCR was performed in 96-well optical plates using iCycler (Bio-Rad Laboratories, Hercules, Calif., USA) with primers specific for Trx1, Trx2, β-actin, GAPDH (glyceraldehyde 3-phosphate dehydrogenase), and iQ SYBR Green Supermix (Bio-Rad). The resulting fluorescence proportional to the amount of amplified DNA was measured at the end of each elongation phase at 530 nm. A standard graph of C T  (the point at which the fluorescence crosses the threshold) values obtained from serially diluted target genes was constructed for all reactions to ensure that they were amplified and reported in proportion to the template. C T  values were converted to gene copy number of the template cDNA using the equation 2 ΔΔCT . The ΔC T  is the abundance of cDNAs for transcripts of each gene normalized to the β-actin and GAPDH at each time point. The ΔΔC T  is obtained by subtracting a calibrator value for each gene transcript being assayed. In parallel with each cDNA sample, standard curves were constructed to correlate C T  values using serial dilutions of the target gene. The property of the standard curve was evaluated from the slope and the correlation coefficient. Quantification was performed by comparing the fluorescence of a PCR product of unknown concentration with the fluorescence of several dilutions. Melting curve analysis was used for product validation. The primers for β-actin and GAPDH were purchased from Origene. Other primer sequences are summarized in Table 1. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Sequence of  
                   
                   
               
               
                 Primers for 
                   
                   
               
               
                 Real-Time PCR 
                   
                   
               
               
                 Amplification 
                 Direction 
                 Primer Sequence (5′-&gt;3′) 
               
               
                   
               
             
             
               
                 Human  
                 Forward 
                 ctgcttttcaggaagccttg 
               
               
                 thioredoxin 
                 Referse 
                 tgttggcatgcatttgactt 
               
               
                 1(Trx 1) 
                   
                   
               
               
                   
               
               
                 Human  
                 Forward 
                 agcccggacaatatacacca 
               
               
                 thioredoxin 
                 Reverse 
                 aatatccaccttggccatca 
               
               
                 2(Trx 2) 
               
               
                   
               
             
          
         
       
     
     1-1. Transcript Level of Thioredoxin 1 in 48 Different Normal Human Tissues 
     Transcript levels of thioredoxin 1 in 48 different human normal tissues selected from individuals of different ethnicities were determined using 96-well HMRT qPCR arrays, and the results are given in  FIG. 1 . 
     As can be seen in  FIG. 1 , thioredoxin 1 was expressed at the lowest level (0.24×10 −4  pg) in breast tissue among the 48 major human tissues. 
     1-2. Levels of mRNA of Thioredoxin 1 and 2 in Human Solid Cancerous Tissues 
     The expression profiles of thioredoxin 1 and 2 in eight solid cancers (breast, colon, kidney, liver, lung, ovary, prostate, and thyroid) were made using the CSRT 96-I array. 
     The results are given in  FIG. 2 . 
     As shown in  FIG. 2 , thioredoxin 1 was expressed at the highest level in breast cancer (6.47±1.22) among the eight solid cancers, whereas thioredoxin 2 was not preferentially expressed in breast cancer (2.72±0.28) (P=0.0067). 
     1-3. Levels of mRNA of Thioredoxin 1 and 2 in Human Breast Cancerous Tissues 
     To examine the expression profile of thioredoxin 1 in breast cancer, the mRNA levels of thioredoxin 1 and 2 in breast cancer were quantified using a 48-well BCRT II array. The induction fold was obtained from the mRNA concentrations of thioredoxin 1 and 2. 
     The mRNA concentrations (A) of thioredoxin 1 and 2 in breast cancer and the induction folds obtained therefrom are shown in  FIG. 3 . 
     As can be seen in  FIG. 3 , the mRNA levels of thioredoxin 1 were much higher than those of thioredoxin 2 in both normal breast and breast cancer tissues. Also, the higher-induction fold of thioredoxin in malignant tissue is depicted compared with thioredoxin 2. 
     1-4. Correlation Between Grade of Human Breast Cancer and Thioredoxin 1 
     To evaluate the correlation of thioredoxin with the progression of breast cancer, mRNA levels in 204 samples of normal and malignant breast tissues ranging from 0 to IV grade were assessed using five different sets of qRT-PCR arrays [Cancer Survey real-time (CSRT 96-I) qPCR array (n=9), and human breast cancer real-time (BCRT I-V) qPCR array I-V (n=1176)], the induction fold from normal (grade 0) to malignant (grade I, II, III, IV) was determined. 
     In  FIG. 4 , Induction fold data for mRNA expression of thioredoxin 1 in human breast cancer were displayed as a scatter dot plot (A), the correlation of mRNA expression of thioredoxin with cancer grade was represented as box-and-whisker plots (B), and data for the induction fold of mRNA expression of thioredoxin 1 in subdivided human breast cancer (stage I, IIA, IIB, IIIA, IIIB, IIIC, and IV) was plotted (C). 
     In breast cancer, as can be seen in  FIG. 4 , 2-fold overexpression of thioredoxin 1 occurred in 168 of 185 cases (90.8%). Mean±SEM induction fold was 5.64±0.33 for thioredoxin 1 (A). There was a significant correlation between the induction fold of thioredoxin 1 and increasing cancer grade. The higher the grade of cancer, the higher the induction fold of mRNA expression of thioredoxin 1. The induction fold was closely correlated with stage II˜IV breast cancer, especially stage IV cancer, that is, metastatic cancer (B). Further, induction fold was associated with subdivisions of cancer stages (P=0.0191) (C). 
     Example 2 
     Western Blotting Analysis 
     To examine the expression level of thioredoxin 1 in human breast cancer tissues with Western blotting analysis, the for owing experiment was conducted. 
     Total membrane and soluble proteins from clinically defined human cancer and normal tissues were obtained from Capital Biosciences (Gaithersburg, Md., USA). Proteins from different individuals and matched paired individuals (normal tissue and primary cancers; primary and metastatic cancers) were used for immunological analysis. The clinical and pathological traits of the cancers are summarized in Table 2, below. 
     The total membrane and soluble protein lysates (15 μg) from seven cancer tissue types (brain, breast, colon, kidney, liver, lung, and ovary) were loaded into reducing and non-reducing SDS-PAGE, followed by Western blot analysis using an Amersham ECL Western blotting system (GE Healthcare, Chalfont St. Giles, United Kingdom). Anti-thioredoxin 1, and anti-copper/zinc (Cu/Zn) superoxide dismutase (SOD) rabbit polyclonal antibodies that have cross-reactivity with the corresponding human protein were purchased from AbFrontier (Seoul, Korea). Samples were fractionated by electrophoresis on a 4% to 20% gradient SDS-PAGE (GenScript Corp., Piscataway, N.J., USA) and transferred onto PVDF (polyvinylidene difluoride) membranes (Millipore, Billerica, Mass., USA). The membranes were blocked and incubated at room temperature for 2 hours with an antibody (1:1000 by volume) in PBS containing 0.1% Tween 20. After washing many times, the membranes were incubated with horseradish peroxidise-conjugated polyclonal goat anti-rabbit IgG antibody (1:2000 by volume). Then, the membranes were washed in PBS, and the chemiluminescent substrate was added. The membranes were stained with Coomassie Blue R-250 for verification of the loading sample. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Sample 
                 Tissue 
                 Appearance 
                 Age/Gender 
                 Diagnosis 
               
               
                   
               
             
             
               
                 BRN0 
                 Brain 
                 Normal 
                 26/M 
                 Normal 
               
               
                 BRC0 
                 Brain 
                 Tumor 
                 40/M 
                 Astrocytoma 
               
               
                 BEN0-4 
                 Breast 
                 Normal 
                 82/F. 45/F. 
                 Normal 
               
               
                   
                   
                   
                 56/F. 64/F. 
               
               
                   
                   
                   
                 76/F 
               
               
                 BEC0 
                 Breast 
                 Tumor 
                 47/F 
                 Medullary Carcinoma, Well 
               
               
                   
                   
                   
                   
                 Differentiated 
               
               
                 BEC1 
                 Breast 
                 Tumor 
                 40/F 
                 Invasive Lobular Carcinoma 
               
               
                 BEC2 
                 Breast 
                 Tumor 
                 42/F 
                 Adenocarcinoma, Moderately 
               
               
                   
                   
                   
                   
                 Differentiated 
               
               
                 BEC3 
                 Breast 
                 Tumor 
                 42/F 
                 Fibroadenoma 
               
               
                 BEC4 
                 Breast 
                 Tumor 
                 50/F 
                 Infiltrative Ductal Carcinoma 
               
               
                 CLN0 
                 Colon 
                 Normal 
                 60/F 
                 Normal 
               
               
                 CLC0 
                 Colon 
                 Tumor 
                 48/M 
                 Adenocarcinoma, Well 
               
               
                   
                   
                   
                   
                 Differentiated 
               
               
                 KDN0 
                 Kidney 
                 Normal 
                 83/F 
                 Normal 
               
               
                 KDC0 
                 Kidney 
                 Tumor 
                 43/F 
                 Granular Cell Carcinoma, 
               
               
                 LVN0 
                 Liver 
                 Normal 
                 30/M 
                 Normal 
               
               
                 LVC0 
                 Liver 
                 Tumor 
                 65/M 
                 Hepatic Cellular Carcinoma, 
               
               
                 LUN0-4 
                 Lung 
                 Normal 
                 24/F. 26M. 
                 Normal 
               
               
                   
                   
                   
                 66/M. 71/M. 
               
               
                   
                   
                   
                 76/F 
               
               
                 LUC0 
                 Lung 
                 Tumor 
                 72/M 
                 Squamous Cell Carcinoma 
               
               
                 LUC1 
                 Lung 
                 Tumor 
                 33/M 
                 Squamous Cell Carcinoma, 
               
               
                   
                   
                   
                   
                 Moderately Differentiated 
               
               
                 LUC2 
                 Lung 
                 Tumor 
                 51/F 
                 Adenocarcinoma, Moderately 
               
               
                   
                   
                   
                   
                 Differentiated 
               
               
                 LUC3 
                 Lung 
                 Tumor 
                 58/M 
                 Squamous Cell Carcinoma, 
               
               
                   
                   
                   
                   
                 Moderately Differenciated 
               
               
                 LUC4 
                 Lung 
                 Tumor 
                 61/M 
                 Adenocarcinoma 
               
               
                 OVN0-4 
                 Ovary 
                 Normal 
                 74/F. 37/F. 
                 Normal 
               
               
                   
                   
                   
                 62/F. 69/F. 
               
               
                   
                   
                   
                 N/A/F 
               
               
                 OVC0 
                 Ovary 
                 Tumor 
                 51/F 
                 Cystoadenocarcinoma 
               
               
                 OVC1 
                 Ovary 
                 Tumor 
                 42/F 
                 Granular Cell Carcinoma 
               
               
                 OVC2 
                 Ovary 
                 Tumor 
                 51/F 
                 Cystoadenoma 
               
               
                 OVC3 
                 Ovary 
                 Tumor 
                 57/F 
                 Leiomyosarcoma, Well 
               
               
                   
                   
                   
                   
                 Differentiated 
               
               
                 OVC4 
                 Ovary 
                 Tumor 
                 Adult/F 
                 Clear Cell Adenocarcinoma 
               
               
                 BE1N 
                 Breast 
                 Adjacent 
                 70/F, same 
                 Normal 
               
               
                   
                   
                 Normal 
                 patient 
               
               
                 BE1P 
                 Breast 
                 Primary Tumor 
                   
                 Invasive Ductal Carcinoma 
               
               
                 BE2P 
                 Breast 
                 Primary Tumor 
                 59/F, same 
                 Breast Carcinoma 
               
               
                 BE2M 
                 Breast 
                 Metastatic 
                 patient 
                 Breast Tumor Metastasized to 
               
               
                   
                   
                 Tumor 
                   
                 Lung 
               
               
                 CL1N 
                 Colon 
                 Adjacent 
                 62/F, same 
                 Normal 
               
               
                   
                   
                 Normal 
                 patient 
               
               
                 CL1P 
                 Colon 
                 Primary Tumor 
                   
                 Adenocarcinoma 
               
               
                 CL2P 
                 Colon 
                 Primary Tumor 
                 66/F, same 
                 Adenocarcinoma 
               
               
                 CL2M 
                 Colon 
                 Metastatic 
                 patient 
                 Colon Tumor Metastasized to 
               
               
                   
                   
                 Tumor 
                   
                 Lymph Node 
               
               
                 LU1N 
                 Lung 
                 Adjacent 
                 46/M, same 
                 Normal 
               
               
                   
                   
                 Normal 
                 patient 
               
               
                 LU1P 
                 Lung 
                 Primary Tumor 
                   
                 Squamous Cell Carcinoma 
               
               
                 LU2P 
                 Lung 
                 Primary Tumor 
                 75/M, same 
                 Squamous Cell Carcinoma 
               
               
                 LU2M 
                 Lung 
                 Metastatic 
                 patient 
                 Lung Tumor Metastasized to 
               
               
                   
                   
                 Tumor 
                   
                 Lymph Node 
               
               
                   
               
             
          
         
       
     
     The results are shown in  FIG. 5 . 
     As shown in  FIG. 5 , thioredoxin 1 was expressed at the highest level in human breast cancerous tissues. 
     2-1. Expression Levels of Thioredoxin 1 in Human Normal Tissues and Cancerous Tissues (Breast, Lung, Ovary) 
     The expression levels of thioredoxin 1 in four normal tissues and four cancerous tissues from different individuals were analyzed by Western blotting. 
     The results are given in  FIG. 6 . 
     As can be seen in  FIG. 6 , thioredoxin 1 was overexpressed in breast cancer. 
     2-2. Expression Levels of Thioredoxin 1 in Paired Sets of Breast Tissue and Paired Sets of Other Tissues (Lung and Colon) 
     The expression levels of thioredoxin 1 in the paired sets of breast tissue (paired normal and primary cancer from the same individual; paired primary and metastatic cancer from the same individual) and the paired sets of other tissues (lung and colon) were analyzed by Western blotting. Cu/Zn SOD is used as positive control. 
     The results are shown in  FIG. 7 . 
     As can be seen in  FIG. 7 , thioredoxin 1 was preferentially overexpressed in breast cancer tissues over the other tissues. 
     Example 3 
     Subjects 
     All sera of normal persons (control) and lung cancer patients were obtained from white Caucasians. To make them suitable for a biomarker study, all the sera were collected and treated according to the instructions of the FDA (Food and Drug Administration) and the NCI (National Cancer Institute). They were prepared from the blood collected after the approval of the IRB and the HIPAA. All the sera and the clinical information thereof were provided from Asterand (U.S.A.) and Bioserve (U.S.A.) as summarized in Tables 3 and 4, below. 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Age 
                 Type of BC 
                 Stage(S) 
                 S Group 
               
               
                   
                   
               
             
             
               
                   
                 65 
                 Infiltrating lobular 
                 T1cN0M0 
                 I 
               
               
                   
                 56 
                 Invasive lobular 
                 T1N0MX 
                 I 
               
               
                   
                 77 
                 Invasive lobular 
                 T1N0M0 
                 I 
               
               
                   
                 54 
                 Lobular 
                 T1bNXM0 
                 I 
               
               
                   
                 48 
                 Lobular 
                 T1bNXM0 
                 I 
               
               
                   
                 37 
                 Lobular 
                 T1cN0M0 
                 I 
               
               
                   
                 77 
                 Lobular 
                 T1cNXMX 
                 I 
               
               
                   
                 33 
                 Infiltrating lobular 
                 T1cN0M0 
                 I 
               
               
                   
                 49 
                 Lobular 
                 T1cN0M0 
                 I 
               
               
                   
                 63 
                 Infiltrating ductal 
                 T1bN0MX 
                 I 
               
               
                   
                 37 
                 Infiltrating ductal 
                 T1cN0M0 
                 I 
               
               
                   
                 55 
                 Infiltrating ductal 
                 T1N0M0 
                 I 
               
               
                   
                 75 
                 Infiltrating ductal 
                 T1NXM0 
                 I 
               
               
                   
                 57 
                 Infiltrating ductal 
                 T1bNXM0 
                 I 
               
               
                   
                 75 
                 Infiltrating ductal 
                 T1bN0MX 
                 I 
               
               
                   
                 47 
                 Infiltrating ductal 
                 T1cN0MX 
                 I 
               
               
                   
                 50 
                 Infiltrating ductal 
                 T1cN0MX 
                 I 
               
               
                   
                 35 
                 Infiltrating ductal 
                 T1cNXM0 
                 I 
               
               
                   
                 83 
                 Infiltrating ductal 
                 T1N0M0 
                 I 
               
               
                   
                 87 
                 Infiltrating ductal 
                 T1NXM0 
                 I 
               
               
                   
                 65 
                 Infiltrating lobular 
                 T1cN1M0 
                 IIA 
               
               
                   
                 42 
                 Invasive lobular 
                 T2NXMX 
                 IIA 
               
               
                   
                 36 
                 Lobular 
                 T2N1MX 
                 IIB 
               
               
                   
                 91 
                 Lobular 
                 T3N0MX 
                 IIB 
               
               
                   
                 79 
                 Lobular 
                 T2NXM0 
                 IIA 
               
               
                   
                 43 
                 Lobular 
                 T2NXM0 
                 IIA 
               
               
                   
                 34 
                 Lobular 
                 T1cN1M0 
                 IIA 
               
               
                   
                 73 
                 Lobular 
                 T1cN1M0 
                 IIA 
               
               
                   
                 28 
                 Lobular 
                 T2NXM0 
                 IIA 
               
               
                   
                 55 
                 Lobular 
                 T2NXM0 
                 IIA 
               
               
                   
                 54 
                 Lobular 
                 T1cN1M0 
                 IIA 
               
               
                   
                 28 
                 Lobular 
                 T1cN1M0 
                 IIA 
               
               
                   
                 65 
                 Infiltrating ductal 
                 T1cN1M0 
                 IIA 
               
               
                   
                 33 
                 Infiltrating ductal 
                 T2N0M0 
                 IIA 
               
               
                   
                 48 
                 Infiltrating ductal 
                 T2N0MX 
                 IIA 
               
               
                   
                 58 
                 Infiltrating ductal 
                 T2N1M0 
                 IIB 
               
               
                   
                 81 
                 Infiltrating ductal 
                 T2N1M0 
                 IIA 
               
               
                   
                 83 
                 Infiltrating ductal 
                 T2N1M0 
                 IIB 
               
               
                   
                 73 
                 Infiltrating ductal 
                 T2N0MX 
                 IIA 
               
               
                   
                 48 
                 Infiltrating ductal 
                 T2N0MX 
                 IIA 
               
               
                   
                 52 
                 Infiltrating ductal 
                 T2NXM0 
                 IIA 
               
               
                   
                 72 
                 Infiltrating ductal 
                 T2NXM0 
                 IIA 
               
               
                   
                 33 
                 Infiltrating ductal 
                 T2N0M0 
                 IIA 
               
               
                   
                 69 
                 Infiltrating lobular 
                 T2N2M0 
                 IIIA 
               
               
                   
                 42 
                 Lobular 
                 T2N2MX 
                 IIIA 
               
               
                   
                 83 
                 Lobular 
                 T4N0M0 
                 IIIB 
               
               
                   
                 26 
                 Lobular 
                 T2N2M0 
                 IIIA 
               
               
                   
                 79 
                 Lobular 
                 T4N2M0 
                 IIIB 
               
               
                   
                 57 
                 Lobular 
                 T4bN0M0 
                 IIIB 
               
               
                   
                 44 
                 Lobular 
                 T3N2MX 
                 IIIA 
               
               
                   
                 73 
                 Lobular 
                 T4bN1M0 
                 IIIB 
               
               
                   
                 55 
                 Lobular 
                 T2N2M0 
                 IIIA 
               
               
                   
                 66 
                 Invasive Ductal 
                 T2N2M0 
                 IIIA 
               
               
                   
                 73 
                 Infiltrating ductal 
                 T2N2M0 
                 IIIA 
               
               
                   
                 53 
                 Infiltrating ductal 
                 T3N2M0 
                 IIIA 
               
               
                   
                 46 
                 Infiltrating ductal 
                 T1N2M0 
                 IIIA 
               
               
                   
                 76 
                 Infiltrating ductal 
                 T3N2M0 
                 IIIA 
               
               
                   
                 52 
                 Infiltrating ductal 
                 T3N1M0 
                 IIIA 
               
               
                   
                 44 
                 Infiltrating ductal 
                 T2N2M0 
                 IIIA 
               
               
                   
                   
               
               
                   
                 All are from female Caucasian patients 
               
             
          
         
       
     
     
       
         
               
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
               
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Characteristics 
                 No. of samples 
               
               
                   
                   
               
             
             
               
                   
                 Breast Carcinoma 
                 59 
               
               
                   
                 Female 
                 59 
               
               
                   
                 Mean age (years) 
                 57.16 ± 17.33 (26-91) 
               
               
                   
                 Stage I 
                 20 
               
             
          
           
               
                   
                 Stage II 
                 23 
                 (IIA 19, IIB 4) 
               
               
                   
                 Stage III 
                 16 
                 (IIIA 12, IIIB 4) 
               
             
          
           
               
                   
                 Lobular Carcinoma of the Breast 
                 30 
               
               
                   
                 Ductal Carcinoma of the Breast 
                 29 
               
               
                   
                 Non-small Cell Lung Cancer (NSCLC) 
                 111  
               
               
                   
                 Male 
                 50 
               
               
                   
                 Female 
                 61 
               
               
                   
                 Mean age (years) 
                   41 ± 10.39 (41-85) 
               
             
          
           
               
                   
                 Stage I 
                 39 
                 (IA 19, IB 20) 
               
               
                   
                 Stage II 
                 32 
                 (IIA 16, IIB 16) 
               
               
                   
                 Stage III 
                 30 
                 (IIIA 21, IIIB 90 
               
             
          
           
               
                   
                 Stage IV 
                 10 
               
             
          
           
               
                   
                 Colorectal Carcinoma 
                 61 
                 (Rectal 14) 
               
               
                   
                 Male 
                 33 
                 (Rectal 7) 
               
               
                   
                 Female 
                 31 
                 (Rectal 7) 
               
             
          
           
               
                   
                 Mean age (years) 
                 63.84 ± 12.20 (39-38) 
               
               
                   
                 Stage I 
                  6 
               
             
          
           
               
                   
                 Stage II 
                 36 
                 (Rectal 7) 
               
               
                   
                 Stage III 
                 22 
                 (Rectal 7) 
               
             
          
           
               
                   
                 Kidney Carcinoma 
                 30 
               
               
                   
                 Male 
                 17 
               
               
                   
                 Female 
                 13 
               
               
                   
                 Mean age (years) 
                 55.07 ± 11.22 (34-76) 
               
               
                   
                 Stage I 
                 26 
               
               
                   
                 Stage II 
                  4 
               
               
                   
                 Normal Control 
                 100  
               
               
                   
                 Male 
                 50 
               
               
                   
                 Female 
                 50 
               
               
                   
                 Male Mean age (years) 
                 44.54 ± 14.85 (20-76) 
               
               
                   
                 Female Mean age (years) 
                 43.70 ± 14.95 (18-71) 
               
               
                   
                 Male/Female Mean age (years) 
                 44.12 ± 14.83 (18-76) 
               
               
                   
                   
               
               
                   
                 *All serums are from white Caucasian. 
               
             
          
         
       
     
     Example 4 
     ELISA Assay 
     ELISA (Enzyme-linked immunosorbent assay) was performed to quantitatively analyze blood proteins. 
     Sera obtained after the centrifugation of blood samples taken from normal persons and breast cancer patients were used for quantitative protein analysis with an ELISA kit using antibodies of interest (Express ELISA kit (rabbit), GenScript). In this regard, mono-specific antibodies to respective antigens were obtained by injecting purified peptides into rabbits to form antisera and purifying the antisera on a Protein A column. 
     A standard curve was made from the absorbance at 450 nm of various concentrations of each antigen peptide. Serum protein levels were determined with reference to the standard curve from the mean values of three measurements of absorbance at 450 nm. For statistical analysis, the software GraphPad Prism (ver. 5.04) (GraphPad Software) was used. 
     4-1: Measurement of Serum Thioredoxin 1 Level in Breast Cancer Patients 
     Measurements of the ELISA performed on the sera of 50 normal female persons and 59 breast cancer patients over a wide range of ages (41-85) with a uniform distribution (41±10.39, mean±SD) were subjected to ROC curve analysis and the results are shown in  FIG. 8  and Table 5. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 (ng/ml of serum) 
               
             
          
           
               
                   
                 Normal Control 
                 Breast Cancer 
                 KC 
                 LC 
                 CRC 
               
             
          
           
               
                   
                 F/M 
                 F 
                 M 
                 I-III 
                 I 
                 II 
                 III 
                 L 
                 D 
                 (I/II) 
                 (I-IV) 
                 (I-III) 
               
               
                   
                   
               
             
          
           
               
                 # of values 
                 100 
                 50 
                 50 
                 59 
                 20 
                 23 
                 16 
                 30 
                 29 
                 30 
                 111 
                 64 
               
               
                 75% Percentile 
                 23.26 
                 23.98 
                 22.35 
                 36.84 
                 34.27 
                 36.14 
                 40.73 
                 38.18 
                 35.65 
                 25.79 
                 25.23 
                 27.71 
               
               
                 Median 
                 27.64 
                 28.50 
                 26.22 
                 43.21 
                 38.64 
                 43.48 
                 46.19 
                 43.94 
                 40.37 
                 30.96 
                 31.89 
                 31.09 
               
               
                 75% Percentile 
                 31.96 
                 32.04 
                 31.97 
                 50.76 
                 44.65 
                 51.43 
                 53.16 
                 51.64 
                 47.39 
                 35.54 
                 37.84 
                 38.29 
               
               
                 Mean 
                 27.93 
                 28.62 
                 27.24 
                 43.77 
                 40.10 
                 44.36 
                 47.53 
                 45.09 
                 42.41 
                 31.12 
                 31.71 
                 32.92 
               
               
                 Std. Deviation 
                 6.113 
                 6.054 
                 6.155 
                 8.182 
                 6.551 
                 8.727 
                 7.695 
                 8.168 
                 8.112 
                 7.541 
                 8.254 
                 7.864 
               
               
                 Std. Error 
                 0.611 
                 0.856 
                 0.871 
                 1.065 
                 1.465 
                 1.82 
                 1.924 
                 1.491 
                 1.506 
                 1.377 
                 0.784 
                 0.991 
               
               
                 Lower 95% CI 
                 26.72 
                 26.90 
                 25.49 
                 41.64 
                 37.03 
                 40.58 
                 43.43 
                 42.04 
                 39.33 
                 28.31 
                 30.16 
                 30.94 
               
               
                 Upper 95% CI 
                 29.14 
                 30.34 
                 28.99 
                 45.91 
                 43.17 
                 48.13 
                 51.63 
                 48.14 
                 49.50 
                 33.94 
                 33.26 
                 34.9 
               
               
                   
               
             
          
         
       
     
     As shown in  FIG. 8  and Table 5, the mean value of serum thioredoxin levels was detected at 28.62±6.054 ng/mL in the female normal control (NF), and at 43.77±8.182 ng/mL in the breast cancer group (BC), with about a 53% increase compared to the normal control. With reference to the serum level of thioredoxin 1 according to sub-type of breast cancer, it was 45.09±8.168 in lobular carcinoma of breast (BC_L) and 42.41±8.112 in ductal carcinoma of breast (BC_D). The serum thioredoxin 1 level in lobular carcinoma of breast was about 6.3% increased compared to that in ductal carcinoma of breast. 
     In addition, measurements of serum thioredoxin 1 levels in the female normal control (n=50) and the breast cancer group (n=59) were subjected to ROC curve analysis, and the results are summarized in Table 6. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 Type of 
                 AUC* 
                 Sensitivity 
                 Specificity 
                 Trx1 Cut-off 
                 # of serum 
               
               
                 Cancer 
                 (±SEM) 
                 (%) 
                 (%) 
                 Value (ng/ml) 
                 (Grade) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Breast(F) 
                 0.941 ± 0.0205 
                 94.9 
                 82.0 
                 &gt;33.8179 
                 59 
                 (I/II/III) 
               
               
                 Breast(F/M) 
                 0.947 ± 0.0155 
                 94.9 
                 83.0 
                 &gt;33.8179 
                 59 
                 (I/II/III) 
               
               
                 Colorectal 
                 0.687 ± 0.0425 
                 68.3 
                 61.0 
                 &gt;29.0533 
                 64 
                 (I/II/III) 
               
               
                 Kidney 
                 0.633 ± 0.0617 
                 46.7 
                 81.0 
                 &gt;32.9986 
                 30 
                 (I/II) 
               
               
                 Lung 
                 0.643 ± 0.0381 
                 54.1 
                 73.0 
                 &gt;31.181 
                 108 
                 (I/II/III/IV) 
               
             
          
           
               
                 Normal 
                 — 
                 — 
                 — 
                   
                 100: 50F/50M 
               
               
                   
               
               
                 *p &lt; 0.0001 
               
             
          
         
       
     
     As can be seen in Table 6, the AUC (area under curve, a probability for screening cancer) value was measured at 0.941±0.0205 (mean±SEM), and the cut-off value at &gt;33.8179 ng mL, with a sensitivity of 94.9% and a specificity of 82.0%. 
     This data indicates that thioredoxin 1 can be used as a breast cancer marker capable of discriminating breast cancer patients from the female normal control at a probability of about 95%, with superior sensitivity and selectivity. 
     4-2. Measurement of Serum Thioredoxin 1 Level in Patients with Breast Cancer and Other Cancers 
     Thioredoxin 1 levels in blood samples, preferably serum samples obtained from patients with breast cancer (BC), lung cancer (LC), kidney cancer (KC) and colorectal cancer (CRC) were assayed using ELISA, and the results are shown in  FIG. 9  and Table 5. 
     As can be seen in  FIG. 9 , serum thioredoxin 1 levels were higher in the breast cancer group than in other cancer patients as well as in the female normal control (NF) and male normal control (NM), with statistical significance. Further, as show in Table 5, the blood of breast cancer patients retained significantly higher levels of thioredoxin 1 than did that of other cancer patients. 
     In addition, measurements of blood thioredoxin 1 levels were subjected to ROC curve analysis and the results are summarized in Table 6. 
     As can be seen in Table 6, when compared to the female normal control (NF, n=50) and the male normal control (NM, n=50), the cut-off value for breast cancer was detected at &gt;33.8179 ng/mL, with a sensitivity of 94.9% and a specificity of 83.0%. 
     4-3. Analysis of Thioredoxin 1 as Breast Cancer-Specific Marker 
     To examine the selectivity of the blood marker thioredoxin 1 for breast cancer, the data of serum thioredoxin 1 levels for breast cancer in comparison to other cancers of Example 4-2 (lung cancer (LC), kidney cancer (KC) and colorectal cancer (CRC)) was subjected to interactive dot diagram and ROC curve analysis, and the results are shown in  FIG. 10  and Table 7. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 Type of 
                 AUC* 
                 Sensitivity 
                 Specificity 
                 Trx1 Cut-off 
               
               
                 Cancer 
                 (±SEM) 
                 (%) 
                 (%) 
                 Value (ng/ml) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 BC/NMF 
                 0.947 ± 0.0155 
                 94.9 
                 33.0 
                 &gt;33.8179 
               
               
                 BC/CRC 
                 0.831 ± 0.0365 
                 94.9 
                 60.3 
                 &gt;33.5024 
               
               
                 BC/KC 
                 0.873 ± 0.0390 
                 79.7 
                 80.7 
                 &gt;36.1850 
               
               
                 BC/LC 
                 0.842 ± 0.0295 
                 94.9 
                 59.5 
                 &gt;33.9448 
               
               
                   
               
               
                 *p &lt; 0.0001 
               
             
          
         
       
     
     As is understood from the data of  FIG. 10  and Table 7, serum thioredoxin 1 levels were significantly higher in the breast cancer group than in other cancer patient groups as well as in the female and male normal control (NFM). In addition, when the serum thioredoxin 1 level was measured in breast cancer patients in comparison with other cancer patients, the AUC (area under curve) value exceeded 0.83, with the sensitivity and selectivity detected at more than 80% and 60%, respectively, in all cases, indicating that thioredoxin 1 is useful as a breast cancer-specific marker. 
     4-4. Comparison of Sensitivity Between Thioredoxin 1 and Antioxidant Proteins 
     Serum levels of TXNDC1 (thioredoxin domain-containing protein 1) and Grx3 (Glutaredoxin 3), both of which belong to the thioredoxin superfamily and increase in expression level within cells in sensitive response to oxidative stresses, were compared to those of thioredoxin 1 in breast cancer patients, and the results are shown in  FIG. 11 . 
     As shown in  FIG. 11 , increased serum levels of TXNDC1 and Grx3 were detected in breast cancer patients, but the levels were significantly lower than thioredoxin 1 levels. Further, TXNDC1 and Grx3 exhibited an AUC of less than 0.6. The serum thioredoxin 1 level was observed to have a proportional correlation with the progress of breast cancer, with statistical significance, whereas there were no significant correlations between the serum levels of TXNDC1 and Grx3 and the progress of breast cancer. 
     4-5. Sensitivity of Thioredoxin 1 with the Progress of Cancer 
     In order to reexamine the selectivity of thioredoxin 1 as a breast cancer-specific marker and to confirm the proportional correlation of serum thioredoxin 1 level with the progress of breast cancer, a comparison was made with blood samples taken from many lung cancer patients (LC). The results are shown in  FIG. 12 . 
     As can be seen in  FIG. 12 , the serum thioredoxin 1 level exhibited a correlation with the progress of breast cancer in a pattern similar to that shown in the progress of lung cancer. 
     This data indicates that the increase of serum thioredoxin 1 level with the progress of cancer is due to the oxidative stress increased with the progress of cancer. However, the serum thioredoxin 1 level in the lung cancer group was 35% lower than that in the breast cancer group, suggesting that the high increase in the breast cancer group is attributed to the specificity of thioredoxin 1 for breast cancer. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.