Sensitive liquid chromatography/tandem mass spectrometry assay for absolute quantification of ITIH4-derived putative biomarker peptides in clinical serum samples

Opposing roles of inter-α-trypsin inhibitor heavy chain 4 in recurrent pregnancy loss

Background

The mechanism behind an increased risk of recurrent pregnancy loss (RPL) remains largely unknown. In our previous study, we identified that inter-α-trypsin inhibitor heavy chain 4 (ITI-H4) is highly expressed at a modified molecular weight of 36 kDa in serum derived from RPL patients. Yet, the precise molecular mechanism and pathways by which the short form of ITI-H4 carries out its function remain obscure.

Methods

Human sera and peripheral blood mononucleated cells (PBMCs) were collected from patients and normal controls to compare the expression levels of ITI-H4 and plasma kallikrein (KLKB1). Flow cytometric assay was performed to measure inflammatory markers in sera and culture supernatants. Furthermore, to investigate the functions of the two isoforms of ITI-H4, we performed migration, invasion, and proliferation assays.

Findings

In the current study, we showed that ITI-H4 as a biomarker of RPL could be regulated by KLKB1 through the IL-6 signaling cascade, indicating a novel regulatory system for inflammation in RPL. In addition, our study indicates that the two isoforms of ITI-H4 possess opposing functions on immune response, trophoblast invasion, and monocytes migration or proliferation.

Interpretation

The ITI-H4 (∆N⁶⁸⁸) might be a crucial inflammatory factor which contributes to the pathogenesis of RPL. Moreover, it is expected that this study would give some insights into potential functional mechanisms underlying RPL.

Fund

This study was supported by the Ministry of Health & Welfare of the Republic of Korea (HI18C0378) through the Korea Health Industry Development Institute.

Inflammation and hemostasis in older octogenarians: implication in 5-year survival

Social changes and medical advances have increased longevity, but the conditions governing healthy vs unhealthy cardiovascular (CV) aging are not fully known. Factors beyond classical CV risk factors may have an important unrecognized value. We sought to identify proteins differentially expressed in healthy octogenarians (HOs) without a history of cardiovascular disease (CVD) and preserved functional and cognitive state compared with octogenarians with a history of CVD and cognitive decline (UHOs) using a systems biology approach, and investigated how these proteins relate to CV mortality at 5-year follow-up. Plasmas obtained from older octogenarians (87 ± 0 years) were analyzed by 2-DE + MS and bioinformatic pathway analysis in HOs (N = 38) and UHOs with cognitive (MEC<25) and functional (Barthel<90) decline and a previous ischemic event (acute myocardial infarction and/or stroke; N = 27). Results were validated by ELISA in HOs and UHOs and in an additional group of older octogenarians without cognitive impairment but with a previous CVD manifestation (HO-CVD; N = 35). UHOs showed a coordinated change in several inflammation-related proteins (AMBP, RBP4, and ITIH4; P < 0.05), together with a significant increase in the major inducer of the acute-phase reaction, interleukin-6 (P = 0.03). UHOs also showed a coordinated increase in hemostatic proteins that was associated with an impairment of fibrinolysis and an increased 5-year CV mortality (P = 0.003). The combination of inflammation (ITIH4 and interleukin-6) and hemostatic markers (D-dimer, A2AP, and coagulation factor XIII) was able to discriminate the presence of an unhealthy phenotype in the elderly (AUC = 0.750; P = 0.001). Unhealthy older octogenarians show increased levels of several plasma proteins of inflammation and coagulation. In older octogenarians, the increase in hemostatic markers indicated an increase in 5-year CV mortality at follow-up.

Quantitation of human peptides and proteins via MS: review of analytically validated assays

Since the development of monoclonal antibodies in the 1970s, antibody-based assays have been used for the quantitation of proteins and peptides and, today, they are the most widely used technology in routine laboratory medicine and bioanalysis. However, in the last couple of decades, liquid chromatography-mass spectrometry/mass spectrometry (LC–MS/MS) techniques have been adopted in the quantitation of small molecules, and more recently have made significant contributions in the quantitation of proteins and peptides. In this article, we will review clinical MS-based assays for endogenous peptides, proteins, and therapeutic antibodies, for which validated methods exist. We will also cover the measurement of protein turnover and the unique solutions that MS can offer in this field.

Inter-alpha-trypsin inhibitor heavy chain H4 as a diagnostic and prognostic indicator in patients with hepatitis B virus-associated hepatocellular carcinoma

OBJECTIVES

Inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4) is associated with various diseases. We evaluated the diagnostic and prognostic significance of serum ITIH4 levels in healthy controls and patients with chronic hepatitis B (CHB), hepatitis B virus (HBV)-related liver cirrhosis, and HBV-related hepatocellular carcinoma (HCC).

DESIGN AND METHODS

The study enrolled 300 individuals (50 healthy controls, 50 with CHB, 100 with HBV-associated cirrhosis, and 100 with HBV-associated HCC). Serum ITIH4 levels were determined by western blot analysis and expressed in densitometry units (DU).

RESULTS

ITIH4 levels were higher in CHB (mean: 252.96 DU) and liver cirrhosis (mean: 206.43 DU) patients than in healthy controls (mean: 75.92 DU) and HCC patients (mean: 92.86 DU) (P<0.001). The area under the receiver operating characteristic curve was 0.71 for the diagnosis of HCC in patients with HBV-related liver disease. Multivariate Cox regression analysis showed that large tumor size (≥5 cm) was independently associated with overall survival (hazard ratio 5.894, 95% confidence interval 1.373-25.300, P=0.017). A Kaplan-Meier survival analysis showed significantly worse survival among HCC patients with both low ITIH4 (<80 DU) and a large tumor size compared to that among other HCC patients (P<0.001), and among patients with high AFP (>200 ng/mL) and low ITIH4 compared to that among other HCC patients (P=0.041).

CONCLUSIONS

Serum ITIH4 levels are reduced in HCC patients compared to that in CHB and cirrhosis patients, and low serum ITIH4 levels are associated with shorter survival in HBV-associated HCC patients.

Recent advances in molecular imaging of premalignant gastrointestinal lesions and future application for early detection of barrett esophagus

Recent advances in optical molecular imaging allow identification of morphologic and biochemical changes in tissues associated with gastrointestinal (GI) premalignant lesions earlier and in real-time. This focused review series introduces high-resolution imaging modalities that are being evaluated preclinically and clinically for the detection of early GI cancers, especially Barrett esophagus and esophageal adenocarcinoma. Although narrow band imaging, autofluorescence imaging, and chromoendoscopy are currently applied for this purpose in the clinic, further adoptions of probe-based confocal laser endomicroscopy, high-resolution microendoscopy, optical coherence tomography, and metabolomic imaging, as well as imaging mass spectrometry, will lead to detection at the earliest and will guide predictions of the clinical course in the near future in a manner that is beyond current advancements in optical imaging. In this review article, the readers will be introduced to sufficient information regarding this matter with which to enjoy this new era of high technology and to confront science in the field of molecular medical imaging.

Proteomics for breast cancer urine biomarkers

Although the survival of breast cancer (BC) patients has increased over the last two decades due to improved screening programs and postoperative adjuvant systemic therapies, many patients die from metastatic relapse. Current biomarkers used in the clinic are not useful for the early detection of BC, or monitoring its progression, and have limited value in predicting response to treatment. The development of proteomic techniques has sparked new searches for novel protein markers for many diseases including BC. Proteomic techniques allow for a high-throughput analysis of samples with the visualization and quantification of thousands of potential protein and peptide markers. Human urine is one of the most interesting and useful biofluids for routine testing and provides an excellent resource for the discovery of novel biomarkers, with the advantage over tissue biopsy samples due to the ease and less invasive nature of collection. In this review, we summarize the results from studies where urine was used as a source for BC biomarker research and discuss urine sample preparation, its advantage, challenges, and limitation. We focus on the gel-based proteomic approaches as well as the recent development of quantitative techniques in BC urine biomarker detection. Finally, the future use of modern proteomic techniques in BC biomarker identification will be discussed.

Comparison of triple quadrupole and high-resolution TOF-MS for quantification of peptides

Background: With an increased interest in peptides and proteins as potential new drug candidates, new approaches for sensitive and selective quantitative analysis are required. LC–MS/MS analysis provides a good alternative to immunoassays with reduced method development times and increased specificity. Results: We have evaluated two state-of-the-art triple quadrupole and high-resolution TOF mass spectrometers with respect to their performance for quantification of six peptides (glufibrinopeptide B, somatostatin, enfuvirtide, TRI1144, C34 and exenatide). The peptides were spiked into protein-precipitated plasma supernatant. Triple quadrupole quantification was performed in SRM mode, and in high-resolution, MS narrow-width extracted chromatograms were generated for quantification. Specificity, accuracy, reproducibility and robustness were found to be comparable between the two instruments. The triple quadrupole instrument is still the most sensitive instrument for quantification of peptides with a median factor of about four-times higher sensitivity (based on LLOQ evaluation). Conclusion: Based on sensitivity, the newest generation triple quadrupole MS systems are still the preferred technology for quantification of peptides. Since the sensitivity difference between triple quadrupole instruments and the new-generation high-resolution TOF-MS instruments is minor, the latter offer a useful alternative whenever additional selectivity is preferred or the use of a generic approach not requiring method optimization is advantageous.

Towards clinical applications of selected reaction monitoring for plasma protein biomarker studies

The widespread clinical adoption of protein biomarkers with diagnostic, prognostic and/or predictive value remains a formidable challenge for the biomedical community. From discovery to validation, the path to biomarkers of clinical relevance abounds with many protein candidates, yet so few concrete examples have been substantiated. In this review, we focus on the recent adoption of selected reaction monitoring (SRM) of plasma proteins in the path to clinical use for a broad range of diseases including cancer, cardiovascular disease, genetic disorders and various metabolic disorders. Recent progress reveals a promising outlook for clinical applications using SRM, which now provides the routine analysis of clinically relevant protein markers at low nanogram per millilitre in plasma.

Surface shaving as a versatile tool to profile global interactions between human serum proteins and the Staphylococcus aureus cell surface

The human commensal bacterium Staphylococcus aureus is renowned as a causative agent of severe invasive diseases. Upon entering the bloodstream, S. aureus can infect almost every tissue and organ system in the human body. To withstand insults from the immune system upon invasion, several immune-evasive mechanisms have evolved in S. aureus, such as complement inhibition by secreted proteins and IgG-binding by surface-exposed protein A. While it is generally accepted that S. aureus cells bind a range of host factors for various purposes, no global analyses to profile staphylococcal host factor binding have so far been performed. Therefore, we explored the possibility to profile the binding of human serum proteins to S. aureus cells by "surface shaving" with trypsin and subsequent MS analysis of liberated peptides. This resulted in the identification of several components of the complement system, the platelet factor 4 and the isoform 1 of the inter-α-trypsin inhibitor heavy chain H4 on the staphylococcal cell surface. We conclude that surface shaving is a versatile tool to profile global interactions between human serum proteins and the S. aureus cell surface.

The absolute quantification of eight inter-α-trypsin inhibitor heavy chain 4 (ITIH4)-derived peptides in serum from breast cancer patients

PURPOSE

Various studies exploring the potential of the low-molecular-weight serum peptidome have identified proteolytic cleavage products of inter-α-trypsin inhibitor heavy chain-4 (ITIH(4)) as potential markers for different types of cancer, presumably generated by tumor-associated exoproteases. However, further elucidation of the discriminative properties of such peptides requires specific quantitative analytical methods.

EXPERIMENTAL DESIGN

Using a recently developed and fully validated liquid chromatography-tandem mass spectrometric method, we have compared absolute serum concentrations of eight peptides derived from ITIH(4 [658-687]) to ([667-687]) (ITIH(4)-30 to -21) between breast cancer patients (n=45) and controls (n=78). Furthermore, serum samples obtained before and after surgical removal of the tumor were analyzed (n=30).

RESULTS

The inter-individual variability in measured serum concentrations was high. Nevertheless, most peptides showed a tendency toward elevated levels in the presence of the breast cancer tumor. Significantly increased serum concentrations were observed in the breast cancer group for ITIH(4)-25 (p=0.036) and -29 (p=0.015). Intra-individual comparisons of serum obtained before and after surgery showed significantly decreased serum levels after surgery for seven of the ITIH(4)-derived peptides (p<0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

The obtained results particularly suggest potential for these ITIH(4)-derived peptides in the follow-up of breast cancer after surgery.

Liquid chromatography/tandem mass spectrometry assay for the absolute quantification of the expected circulating apelin peptides in human plasma

Apelin peptides are of great interest owing to their involvement in physiological and pathological processes and they have been proposed as novel biomarkers for heart failure. The plasma concentrations of bioactive peptides of 12 (apelin-12), 13 (apelin-13) and pyroglutamyl apelin-13 (apelin-p13), 17 (apelin-17) and 36 (apelin-36) amino acids are reported to range from 20 to 4000 pg/mL in healthy subjects. As standard immunoassays cannot specifically quantify each apelin peptide, we have developed a sensitive and targeted multiplexed liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for each plasma apelin fragment. The approach was based on a cation-exchange extraction step of apelin forms present in human plasma. Apelin-12, -13, -p13, -17 and -36 were quantified using a triple quadrupole mass spectrometer operating in the multiple reaction monitoring mode. Stable isotope-labeled internal standards were used for quantification. Following assay validation, apelin peptide stability in plasma was investigated. Ten plasma samples from healthy donors were analyzed both with a standard immunoassay and with our LC/MS/MS method. The immunoassay results for the ten healthy donors showed immunoreactive plasma apelin concentrations ranging from 208 to 466 pg/mL. The lower limits of detection of our LC/MS/MS assay ranged from 10 to 50 pg/mL for apelin-12, -13, -p13, -17, and -36. Surprisingly, none of the five expected circulating forms of apelin was detected. These results question the nature and/or the concentration of circulating apelin peptides as well as the specificity of the immunoassays that have hitherto been used for clinical applications.

Specific Investigation of Sample Handling Effects on Protease Activities and Absolute Serum Concentrations of Various Putative Peptidome Cancer Biomarkers

Introduction

In the search for novel cancer biomarkers, various proteolytically derived peptides have been proposed to exhibit cancer or cancer-type specificity. As these peptides are presumably also generated after sample collection by tumor-specific proteases, extensive investigation of the involved proteolytic processes is crucial for further research.

Materials and Methods

Using two previously developed and fully validated liquid-chromatography coupled to tandem-mass spectrometry assays, absolute quantification of, in total, 13 proteolytically derived peptides in human serum was accomplished. The analytes included eight peptides derived from inter-α-trypsin inhibitor heavy chain-4 (ITIH₄-30, ITIH₄-29, ITIH₄-28, ITIH₄-27, ITIH₄-26, ITIH₄-25, ITIH₄-22, and ITIH₄-21), bradykinin, des-Arg⁹-bradykinin, Hyp³-bradykinin, and fragments from fibrinogen-α-chain (Fib-α _[605–629]) and complement component 4a (C4a _{[1337–1350]}). Samples were obtained from different healthy individuals and prepared with variable tube types, clotting times, and temperatures. Furthermore, stabilities in the serum fraction were assessed and compared to stabilities in serum from breast cancer patients.

Results and Discussion

The quantitative analyses showed either increasing or decreasing serum concentrations during blood coagulation, while comparable effects were observed in serum separated from the blood clot. Furthermore, comparisons of inter- and intra-individual variations suggested better reflection of an individual’s protease activity after prolonged ex vivo incubation. This was illustrated for the putative breast cancer marker ITIH₄-22, revealing better differentiation after incubation of serum at ambient temperature for 24 h.

Conclusion

The presented study provides suggestions for more specific and optimized sample preparation, as well as extended knowledge necessary to further explore the opportunities of these proteolytic peptides as cancer biomarkers.