New approaches for biomarker discovery in lung cancer

What did we learn from multiple omics studies in asthma?

More than a decade has passed since the finalization of the Human Genome Project. Omics technologies made a huge leap from trendy and very expensive to routinely executed and relatively cheap assays. Simultaneously, we understood that omics is not a panacea for every problem in the area of human health and personalized medicine. Whilst in some areas of research omics showed immediate results, in other fields, including asthma, it only allowed us to identify the incredibly complicated molecular processes. Along with their possibilities, omics technologies also bring many issues connected to sample collection, analyses and interpretation. It is often impossible to separate the intrinsic imperfection of omics from asthma heterogeneity. Still, many insights and directions from applied omics were acquired-presumable phenotypic clusters of patients, plausible biomarkers and potential pathways involved. Omics technologies develop rapidly, bringing improvements also to asthma research. These improvements, together with our growing understanding of asthma subphenotypes and underlying cellular processes, will likely play a role in asthma management strategies.

Protein profiling in respiratory disease: techniques and impact

Multifactorial diseases such as respiratory disease call for a global analysis of such disorders. Recent advances in protein profiling techniques may allow for early diagnosis of respiratory disease, which is crucial for intervention and treatment. In order to reduce false-positive rates, clinical diagnosis requires a high degree of sensitivity and specificity to be an effective screening tool. Protein profiles identified by ProteinChip (Ciphergen Biosystems) technology coupled with mass spectrometry affords a global analysis of clinical samples and is beginning to reach acceptable levels of sensitivity and specificity. Combining the profile with another diagnostic tool enhances the effectiveness of protein profiles to classify disease. Although current efforts have centered on serum protein profiling, the local environment of the lung may be better reflected in proteins of bronchoalveolar lavage or sputum. Identification of biomarkers of disease by protein profiling analyses may lead to an understanding of the mechanisms of this disease and contribute to the discovery of new therapeutics for the prevention and treatment of disease. Advancing these analyses are techniques such as ProteinChip mass spectrometry, laser capture microdissection, tissue microarrays and fluorescently labeled antibody bead arrays, which enable the direct global analysis of complex mixtures. Effective high-throughput and ease of use of clinical testing will arrive with improvements in bioinformatics and decreases in instrumentation costs.

Subunit-specific mass spectrometry method identifies haptoglobin subunit alpha as a diagnostic marker in non-small cell lung cancer

Haptoglobin (Hp) subunits have been suggested as a potential serum marker for lung cancer. Research is intense on the application of Hp subunits to predict the cancer earlier. Nevertheless, it remains difficult to accurately measure the content of Hp subunits. We developed stable isotope dilution-multiple reaction monitoring mass spectrometry (SID-MRM-MS) capable of measuring Hp subunits (alpha and beta chains). Three isotopic analogs (NPANPVQ, TEGDGVYTLNDK and ILGGHLDAK for alpha, alpha2 and beta chain, respectively) were used as internal standard (IS) for SID-MRM-MS. Serum levels of each Hp subunit were measured in 210 clinical samples using SID-MRM-MS. A concentration ratio of each Hp subunit to total Hp was investigated. Secretion levels of alpha and beta chains were significantly increased in non-small cell lung cancer (NSCLC) compared to controls (P<0.0001). Alterations of the alpha chain ratio were more apparent than beta chain between controls and NSCLC (P=0.0001 and 0.338 for alpha and beta chains, respectively). In conclusion, this study provides not only an efficient quantitative method to determine each Hp subunit in crude sera, but also evidence that Hp alpha chain is a more prospective biomarker to diagnose NSCLC than beta chain.

BIOLOGICAL SIGNIFICANCE

Recent several studies have reported Hp as a potential biomarker for diagnosis of lung cancer. However a successful evaluation of the value of Hp subunits was not achieved on clinical samples. To evaluate the diagnostic performance of each Hp subunit, the development of an accurate quantitative assay of Hp subunits is necessary. In this regard, we employed a new analytical method using stable isotope dilution-multiple reaction monitoring mass spectrometry (SID-MRM-MS), capable of measuring Hp subunits in 210 clinical specimens. In this article, we measured the Hp subunit concentrations and Hp subunits/total Hp ratios in patients with NSCLC using SID-MRM-MS. This is the first report on the evaluation of each Hp subunit as a lung cancer marker using SID-MRM-MS. Consequently, we evaluated specific three tryptic peptides (e.g. NPANPVQ, TEGDGVYTLNDK and ILGGHLDAK for alpha, alpha2 and beta chain, respectively) with high specificity and sensitivity for determination of Hp subunits. Through future large prospective cohort studies, the clinical application of Hp subunits as complementary markers, especially Hp alpha, would be useful for the diagnosis of NSCLC.

Overexpression of adenylate cyclase-associated protein 1 is associated with metastasis of lung cancer

Lung cancer ranks first in both prevalence and mortality rates among all types of cancer. Metastasis is the main cause of treatment failure. Biomarkers are critical to early diagnosis and prediction and monitoring of progressive lesions. Several biomarkers have been identified for lung cancer but none have been routinely used clinically. The present study assessed the diagnostic and prognostic value of cyclase-associated protein 1 (CAP1) for lung cancer. CAP1 mRNA abundance and protein content were determined by real-time PCR and western blot analysis and/or immunostaining in biopsy specimens (24 neoplastic and 6 non-neoplastic) freshly collected at surgical lung resection, in 82 pathologically banked lung cancer specimens and in cultured non-invasive (95-C) and invasive (95-D) lung cancer cells. Multivariate regression analysis was performed to correlate immunoreactive CAP1 signal with cancer type and stage. In vitro cell migration was performed to determine the effect of RNA interference-mediated CAP1 gene silencing on invasiveness of 95-D cells. These analyses collectively demonstrated that: i) both CAP1 mRNA abundance and protein content were significantly higher in neoplastic compared to non-neoplastic specimens and in metastatic compared to non-metastatic specimens but not different between adenocarcinoma and squamous cell carcinoma; ii) immunoreactive CAP1 signal was significantly stronger in metastatic specimens and 95-D cells compared to non-metastatic specimens and 95-C cells; and iii) RNA interference-mediated CAP1 gene silencing adequately attenuated the invasive capacity of 95-D cells in vitro. These findings suggest that overexpression of CAP1 in lung cancer cells, particularly at the metastatic stage, may have significant clinical implications as a diagnostic/prognostic factor for lung cancer.

Identification of serum amyloid A in the serum of gastric cancer patients by protein expression profiling

The purpose of this study was to screen serum samples from gastric carcinoma patients and to determine whether serum amyloid A protein (SAA) served as a biomarker. SELDI technology was used to screen for changes in SAA levels in the serum samples. A mass cluster with a mass/charge (m/z) value between 11.1 and 11.9 kDa was identified in the serum samples from gastric carcinoma patients which was much higher than that of the control group. Furthermore, the increase in this m/z peak correlated with the severity of the cancer. High-performance liquid chromatography (HPLC) analysis confirmed that the peak was SAA1. In conclusion, this increase in SAA may be used as a potential biomarker for gastric cancer.

Large-scale isotype-specific quantification of Serum amyloid A 1/2 by multiple reaction monitoring in crude sera

Quantification is an essential step in biomarker development. Multiple reaction monitoring (MRM) is a new modified mass spectrometry-based quantification technology that does not require antibody development. Serum amyloid A (SAA) is a positive acute-phase protein identified as a lung cancer biomarker in our previous study. Acute SAA exists in two isoforms with highly similar (92%) amino acid sequences. Until now, studies of SAA have been unable to distinguish between SAA1 and SAA2. To overcome the unavailability of a SAA2-specific antibody, we developed MRM methodology for the verification of SAA1 and SAA2 in clinical crude serum samples from 99 healthy controls and 100 lung adenocarcinoma patients. Differential measurement of SAA1 and SAA2 was made possible for the first time with the developed isotype-specific MRM method. Most healthy control samples had small or no MS/MS peaks of the targeted peptides otherwise, higher peak areas with 10- to 34-fold increase over controls were detected in lung cancer samples. In addition, our SAA1 MRM data demonstrated good agreement with the SAA1 enzyme-linked immunosorbent assay (ELISA) data. Finally, successful quantification of SAA2 in crude serum by MRM, for the first time, shows that SAA2 can be a good biomarker for the detection of lung cancers.

The Haptoglobin β chain as a supportive biomarker for human lung cancers

Haptoglobin (Hp) is produced as an acute phase reactant during inflammation, infection, malignant diseases, and several cancers. In proteomics analysis using human blood samples, the Hp peptide levels were about 3-fold higher in lung cancer patients versus normal individuals. This study is aimed at analyzing the elevation of which chain of Hp is closely related to lung cancers and can be a serum biomarker for lung cancers. In Western blot (WB) analysis, we found that the Hp β chain can be a better diagnostic biomarker for lung cancers. In the result of the Hp β chain ELISA developed by us, the concentrations of the Hp β chain in the sera increased about 4-fold in 190 lung adenocarcinoma patients versus 190 healthy controls (8.0 ± 3.8 μg ml(-1)vs. 1.9 ± 1.2 μg ml(-1)). ELISA data showed that the serum levels of the Hp β chain in breast cancer (1.5 ± 0.5 μg ml(-1)) and hepatocellular carcinoma (HCC) (1.4 ± 1.0 μg ml(-1)) patients remained similar to those of healthy controls. Compared to lung adenocarcinoma, the Hp β chain levels in the plasma of patients with other respiratory diseases such as tuberculosis (TBC), idiopathic pulmonary fibrosis (IPF) and bronchial asthma (BA) were closer to those of healthy controls. Our data suggest that an increase of the Hp β chain can be a potential serum biomarker for lung cancers.

Identification and validation of SAA as a potential lung cancer biomarker and its involvement in metastatic pathogenesis of lung cancer

Lung cancer is recently regarded as an overhealed inflammatory disease. Serum amyloid A (SAA) is known as an acute phase protein, but it is likely involved in the cancer pathogenesis. We identified both SAA1 and SAA2 in the pooled sera of lung cancer patients but not in the healthy control, by LC-MS/MS analysis. We found that about 14-fold higher levels of SAA in lung cancer patients' sera and plasma compared to healthy controls by ELISA using total 350 samples (13.89 ± 37.18 vs 190.49 ± 234.70 ug/mL). The SAA levels were also significantly higher than in other pulmonary disease or other cancers. An immunohistochemical study using tissue microarray showed that, unlike other cancer tissues, lung cancer tissues highly express SAA. Further in vitro experiments showed that SAA is induced from lung cancer cells by the interaction with THP-1 monocytes and this, in return, induces MMP-9 from THP-1. In in vivo animal models, overexpressed SAA promoted Lewis lung carcinoma (LLC) cells to metastasize and colonize in the lung. Our data suggest that a higher concentration of SAA can serve as an indicator of lung adenocarcinoma and represents a therapeutic target for the inhibition of lung cancer metastasis.

Detection of lung cancer using plasma protein profiling by matrix-assisted laser desorption/ionization mass spectrometry

There are no satisfactory plasma biomarkers which are available for the early detection and monitoring of lung cancer, one of the most frequent cancers worldwide. The aim of this study is to explore the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) to plasma proteomic patterns to distinguish lung cancer patients from healthy individuals. The EDTA plasma samples have been pre-fractionated using magnetic bead kits functionalized with weak cation exchange coatings. We compiled MS protein profiles for 90 patients with squamous cell carcinomas (SCC) and compared them with profiles from 187 healthy controls. The MALDI-ToF spectra were analyzed statistically using ClinProTools bioinformatics software. Depending on the sample used, up to 441 peaks/spectrum could be detected in a mass range of 1000-20,000 Da; 33 of these proteins had statistically differential expression levels between SCC and control plasma (P < 0.001). The series of the peaks were automatically chosen as potential biomarker patterns in the training set. They allowed the discrimination of plasma samples from healthy control and samples from SCC patients (sensitivity and specificity >90%) in external validation test. These results suggest that plasma MALDI-ToF MS protein profiling can distinguish patients with SCC and also from healthy individuals with relatively high sensitivity and specificity and that MALDI- ToF MS is a potential tool for the screening of lung cancer.

Mass spectrometry-based biomarker discovery: toward a global proteome index of individuality

Biomarker discovery and proteomics have become synonymous with mass spectrometry in recent years. Although this conflation is an injustice to the many essential biomolecular techniques widely used in biomarker-discovery platforms, it underscores the power and potential of contemporary mass spectrometry. Numerous novel and powerful technologies have been developed around mass spectrometry, proteomics, and biomarker discovery over the past 20 years to globally study complex proteomes (e.g., plasma). However, very few large-scale longitudinal studies have been carried out using these platforms to establish the analytical variability relative to true biological variability. The purpose of this review is not to cover exhaustively the applications of mass spectrometry to biomarker discovery, but rather to discuss the analytical methods and strategies that have been developed for mass spectrometry-based biomarker-discovery platforms and to place them in the context of the many challenges and opportunities yet to be addressed.

Haptoglobin and posttranslational glycan-modified derivatives as serum biomarkers for the diagnosis of nonsmall cell lung cancer

BACKGROUND

The purpose was to evaluate the clinical utility of serum haptoglobin (Hp) and posttranslational glycan modifications of Hp for the diagnosis of nonsmall cell lung cancer (NSCLC).

METHODS

Serum proteins from patients with a new diagnosis of NSCLC and age- and sex-matched controls without cancer were compared using 2-dimensional difference gel electrophoresis (2D-DIGE). Four of the differentially expressed gel spots were identified as the beta chain of Hp. Immunoblots confirmed sialyl and fucosyl group posttranslational modifications (PTMs) of Hp. Serum enzyme-linked immunosorbent assays (ELISAs) for total Hp, sialylated Hp (SAHp), and fucosylated Hp (FHp) were designed, and levels of each were measured in an independent sample set of 74 patients. Receiver operating characteristic (ROC) analysis assessed the clinical diagnostic utility of each marker.

RESULTS

Statistically significant differences between lung cancer patients and matched controls were found by ELISA for Hp (P < .002), SAHp (P < .001), and FHp (P < .04). ROC analysis determined an area under the curve (AUC) of 0.754 for Hp, 0.740 for SAHp, and 0.794 for FHp. In addition, serum concentrations correlated with stage; Hp (r = 0.388; P = .018), SAHp (r = 0.300; P = .072), and FHp (r = 0.363; P = .027).

CONCLUSIONS

Hp and 2 of its glycoforms, SAHp and FHp, are potentially useful in the clinical diagnosis of NSCLC. The markers increase with stage, suggesting they may also be useful in stratifying patients at presentation and in following patients after treatment.

Reduced transthyretin expression in sera of lung cancer

Lung cancer is a leading cause of cancer death worldwide, and very few specific biomarkers can be used in its clinical diagnosis. Using surface-enhanced laser desorption-ionization time-of-flight mass spectrometry (MS) to find novel serum biomarkers for lung cancer, we analyzed 227 serum samples, including 146 lung cancers, 41 benign lung diseases and 40 normal individuals. Three peaks, at 13.78, 13.90 and 14.07 k m/z, were significantly lower in lung cancer sera compared with sera from normal individuals (P < 0.001), whereas these peaks were higher than those in the sera of benign lung diseases (P < 0.001). The peaks were identified as native transthyretin (TTR) and its two variants by one-dimensional polyacrylamide gel electrophoresis, ESI-MS/MS, immunoprecipitation and western blot analysis. An enzyme-linked immunosorbent assay indicated that TTR levels were consistent with surface-enhanced laser desorption-ionization analysis in all groups tested. It gave 78.5% sensitivity and 77.5% specificity for lung cancer versus normal at the cut-off point 115 microg/mL, and 66.7% sensitivity and 64.4% specificity for lung cancer versus benign lung diseases at the cut-off point 88.5 microg/mL. Therefore, TTR may be useful as a biomarker to improve the diagnosis of lung cancer.

Telomerase activity in sputum and telomerase and its components in biopsies of advanced lung cancer

PURPOSE

In this study, we explored the diagnostic utility of sputum telomerase activity as a non-invasive biomarker of lung cancer. In biopsies of lung cancer, the relationship of telomerase activity to telomerase reverse transcriptase (hTERT) and telomerase RNA component (hTERC) and to c-Myc expression was also evaluated.

METHODS

Paired biopsy and sputum samples were evaluated for telomerase activity by the telomerase repeat amplification protocol (TRAP) assay in 34 cases of lung cancer and in 30 control subjects without any evidence of lung cancer. hTERT and hTERC transcript expression was evaluated in 42 cases of lung cancer and compared to telomerase activity and c-Myc transcript expression.

RESULTS

Telomerase activity was present in 85.2% of biopsies and in 67.6% of paired sputum with a good concordance. Three out of the 30 negative controls showed a weak telomerase activity, all of whom had sarcoidosis. Thus, sputum telomerase activity had sensitivity, specificity, Negative Predictive Value and Positive Predictive Value of 67.6%, 90%, 71% and 88.46%, respectively. The hTERT levels correlated to the telomerase activity but not to the c-Myc oncogene expression.

CONCLUSIONS

In lung cancer, sputum telomerase activity is a candidate non-invasive biomarker of malignancy.

Magneto immuno-PCR: a novel immunoassay based on biogenic magnetosome nanoparticles

We describe an innovative modification of the Immuno-PCR technology for automatable high sensitive antigen detection. The Magneto Immuno-PCR (M-IPCR) is based on antibody-functionalized biogenic magnetosome nanoparticles revealing major advantages over synthetic magnetic particles. The general principle of the M-IPCR is similar to that of a two-sided (sandwich) immunoassay. However, antibody-functionalized magnetosome conjugates were employed for the immobilization and magnetic enrichment of the signal generating detection complex enabling the establishment of a surface independent immunoassay. To this end, the M-IPCR was carried out by simultaneously tagging the antigen with the reagent for read-out, i.e., a conjugate comprising the specific antibody and DNA fragments, in the presence of the antibody-functionalized magnetosomes. To demonstrate the general functionality of the M-IPCR, the detection of recombinant Hepatitis B surface Antigen (HBsAg) in human serum was established. We observed a detection limit of 320pg/ml of HBsAg using the M-IPCR, which was about 100-fold more sensitive than the analogous Magneto-ELISA, established in parallel for comparison purposes.

Identification and validation of differences in protein levels in normal, premalignant, and malignant lung cells and tissues using high-throughput Western Array and immunohistochemistry

The identification of proteins, which exhibit different levels in normal, premalignant, and malignant lung cells, could improve early diagnosis and intervention. We compared the levels of proteins in normal human bronchial epithelial (NHBE) and tumorigenic HBE cells (1170-I) by high-throughput immunoblotting (PowerBlot Western Array) using 800 monoclonal antibodies. This analysis revealed that 87 proteins increased by >2-fold, and 45 proteins decreased by >2-fold, in 1170-I compared with NHBE cells. These proteins are involved in DNA synthesis and repair, cell cycle regulation, RNA transcription and degradation, translation, differentiation, angiogenesis, apoptosis, cell adhesion, cytoskeleton and cell motility, and the phosphatidylinositol 3-kinase signaling pathway. Conventional Western blotting using lysates of normal, immortalized, transformed, and tumorigenic HBEs and non-small cell lung cancer cell lines confirmed some of these changes. The expression of several of these proteins has been then analyzed by immunohistochemistry in tissue microarrays containing 323 samples, including normal bronchial epithelium, hyperplasia, squamous metaplasia, dysplasias, squamous cell carcinomas, atypical adenomatous hyperplasia, and adenocarcinomas from 144 patients. The results of the immunohistochemical studies correlated with the Western blotting findings and showed gradual increases (caspase-8, signal transducers and activators of transcription 5, and p70s6K) or decrease (E-cadherin) in levels with tumor progression. These results indicate that the changes in proteins detected in this study may occur early in lung carcinogenesis and persist in lung cancer. In addition, some of the proteins detected by this approach may be novel biomarkers for early detection of lung cancer and novel targets for chemoprevention or therapy.

Proteomic patterns of preinvasive bronchial lesions

PURPOSE

A proteomics approach is warranted to further elucidate the molecular steps involved in lung tumor development. We asked whether we could classify preinvasive lesions of airway epithelium according to their proteomic profile.

EXPERIMENTAL DESIGN

We obtained matrix-assisted laser desorption/ionization time-of-flight mass spectrometry profiles from 10-microm sections of fresh-frozen tissue samples: 25 normal lung, 29 normal bronchial epithelium, and 20 preinvasive and 36 invasive lung tumor tissue samples from 53 patients. Proteomic profiles were calibrated, binned, and normalized before analysis. We performed class comparison, class prediction, and supervised hierarchic cluster analysis. We tested a set of discriminatory features obtained in a previously published dataset to classify this independent set of normal, preinvasive, and invasive lung tissues.

RESULTS

We found a specific proteomic profile that allows an overall predictive accuracy of over 90% of normal, preinvasive, and invasive lung tissues. The proteomic profiles of these tissues were distinct from each other within a disease continuum. We trained our prediction model in a previously published dataset and tested it in a new blinded test set to reach an overall 74% accuracy in classifying tumors from normal tissues.

CONCLUSIONS

We found specific patterns of protein expression of the airway epithelium that accurately classify bronchial and alveolar tissue with normal histology from preinvasive bronchial lesions and from invasive lung cancer. Although further study is needed to validate this approach and to identify biomarkers of tumor development, this is a first step toward a new proteomic characterization of the human model of lung cancer tumorigenesis.

Screening for lung cancer: New horizons?

Lung cancer remains the leading cause of cancer-related deaths in the world. At present, the only high rate of cure therapy is surgical resection at early stage of disease. Early detection could potentially decrease lung cancer mortality suggesting that this cancer should be a good candidate for screening. Results of trials involving chest X-ray, sputum cytology and low-dose computed tomography (CT) are discussed here. The latter tool offers advantages over chest X-ray, but final results from controlled well conducted trials are necessary before the real utility of CT mass screening can be determined. Further approaches to secondary prevention such as screening with positron emission tomography (PET), autofluorescence bronchoscopy and biomarkers hold great promise for the future.

Chemoprevention in lung carcinogenesis--an overview

Lung cancer ranks among the most commonly occurring malignancies and is currently the leading cause of cancer-related death worldwide. This is due to its late diagnosis and relative resistance to standard oncological treatment approaches. The heavy burden of lung cancer and its treatment resistance have elicited an intense interest in the promising approach of chemoprevention. Chemoprevention is defined as a pharmacologic intervention to suppress or reverse the carcinogenic process and the lung is one of the most studied sites for cancer chemoprevention. This review, with a short update on pulmonary carcinogenesis, will summarize the available knowledge of chemoprevention trials and agents with a preventive potential in the 'lung field'.

Biomarkers in non-small cell lung cancer prevention

Identification of biomarkers is one of the most promising approaches for the detection of early malignant or even premalignant lesions with the chance of diagnosing early stages of non-small cell lung cancer that could be treated curatively. Alterations of chromosomes (3p, 5q, 9p), genes (Rb, C-myc, C-mos, hTERT), proteins (p16, p53, K-ras, hnRNP A2/B1, MCM2, EGFR, erbB-2, erbB-3, erbB-4) and others can be found in lung cancer. Some of these occur at early stages of the disease and few could serve as potential screening markers. The actual literature is reviewed and the relevance of the different biomarkers for early lung cancer detection is discussed.

Screening for lung cancer

PURPOSE OF REVIEW

With the development of newer forms of technology such as low-dose spiral computed tomography, there has been a resurgent interest in screening for lung cancer. The purpose of this review is to highlight recent advances in screening for lung cancer. Articles published since September 2002 are reviewed here.

RECENT FINDINGS

More frequent screenings (every 4 or 6 months) showed increased mortality from lung cancer, compared with annual screening. A mass screening conducted in 1990 was effective in a case-control study. The results of lung cancer screening by low-dose spiral computed tomography were reported from the Milan group and the Mayo Clinic. Computed tomography depicted peripheral early lung cancer, especially adenocarcinoma. These results are consistent with previous reports from other groups. Screening with imaging becomes more sensitive with automated computerized methods.

SUMMARY

A high percentage of stage IA lung cancers were detected by screening with low-dose helical computed tomography. The characteristics of the nodules detected by low-dose spiral computed tomography have been clarified. There have been many controversial discussions about cost effectiveness and overdiagnosis. There is still no evidence that screening tests reduce the rate of cancer-specific mortality. Several studies of screening for lung cancer are under way.

Identification of serum amyloid a protein as a potentially useful biomarker to monitor relapse of nasopharyngeal cancer by serum proteomic profiling

PURPOSE

Nasopharyngeal cancer (NPC) is a common cancer in Hong Kong, and relapse can occur frequently. Using protein chip profiling analysis, we aimed to identify serum biomarkers that were useful in the diagnosis of relapse in NPC.

EXPERIMENTAL DESIGN

Profiling analysis was performed on 704 sera collected from 42 NPC patients, 39 lung cancer patients, 30 patients with the benign metabolic disorder thyrotoxicosis (TX), and 35 normal individuals (NM). Protein profile in each NPC patient during clinical follow up was correlated with the relapse status.

RESULTS

Profiling analysis identified two biomarkers with molecular masses of 11.6 and 11.8 kDa, which were significantly elevated in 22 of 31 (71%) and 21 of 31 (68%) NPC patients, respectively, at the time of relapse (RP) as compared with 11 patients in complete remission (CR; RP versus CR, P = 0.009), 30 TX (RP versus TX, P < 0.001), or 35 NM (RP versus NM, P < 0.001). The markers were also elevated in 16 of 39 (41%) lung cancer patients at initial diagnosis. By tryptic digestion, followed by tandem mass spectrometry fragmentation, the markers were identified as two isoforms of serum amyloid A (SAA) protein. Monitoring the patients longitudinally for SAA level both by protein chip and immunoassay showed a dramatic SAA increase, which correlated with relapse and a drastic fall correlated with response to salvage chemotherapy. Serum SAA findings were compared with those of serum Epstein-Barr virus DNA in three relapsed patients showing a similar correlation with relapse and chemo-response.

CONCLUSIONS

SAA could be a useful biomarker to monitor relapse of NPC.