Pathology,proteomics and the pathway to personalised medicine

Introduction: As we move from a discovery to a translational phase in proteomics, with a focus on developing validated clinical assays to assist personalized medicine, there is a growing need for strong bidirectional interactions with the clinical pathology community. Thus, while on one hand the proteomics community will provide candidate biomarkers to assist in diagnosis, prognosis, surveillance, identification of individualized patient medication, and development and validation of new assays for diagnostic use, on the other the pathology community will assist with specific tissue identification and selection (e.g. laser capture microdissection, tissue sections for MS imaging), biobanking, validation of emerging automated histopathology techniques, preparation and classification of relevant patient medical reports, and assisting with the optimization of experimental design for clinical trials.

Areas covered: Here we discuss these topics with a particular emphasis on recent publications and relevant initiatives and outline some of the hurdles that still remain for personalized medicine.

Expert commentary: It is clear that effective crosstalk between the proteomics and pathology communities will greatly accelerate crossover of candidate biomarkers to personalized medicine, which will have significant benefits not only for patient wellbeing, but also the global healthcare budget. However, analysis of the big data generated may become rate-limiting.     

Integrative analysis of the colorectal cancer proteome: potential clinical impact

Introduction: Colorectal cancer (CRC) is one of the common types of cancer that affects a significant proportion of the population and is a major contributor to cancer related mortality. The relatively poor survival rate of CRC could be improved through the identification of clinically useful biomarkers.

Areas covered: This review highlights the need for biomarkers and discusses recent proteomics discoveries in the aspects of CRC clinical practice including diagnosis, prognosis, therapy, screening and molecular pathological epidemiology (MPE). Studies have been evaluated in relation to biomarker target, methodology, sample selection, limitations, and potential impact. Finally, the progress in proteomic approaches is briefly discussed and the main difficulties facing the translation of proteomics biomarkers into the clinical practice are highlighted.

Expert commentary: The establishment of specific guidelines, best practice recommendations and the improvement in proteomic strategies will significantly improve the prospects for developing clinically useful biomarkers.     

Mining the malignant ascites proteome for pancreatic cancer biomarkers

Pancreatic cancer (PC) is one of the most lethal malignancies and disease‐specific biomarkers are desperately needed for better diagnosis, prognosis, monitoring treatment efficacy and for accelerating the development of novel targeted therapeutics. Being an advanced stage manifestation and a proximal fluid in contact with cancer tissues, the ascitic fluid presents itself as a promising rich source of biomarkers. Herein, we present a comprehensive proteomic analysis of pancreatic ascitic fluid. To fractionate the complex ascites proteome, we adopted a multi‐dimensional chromatographic approach that included size‐exclusion, ion‐exchange and lectin‐affinity chromatographic techniques. Our detailed proteomic analysis with high‐resolution Orbitrap^® mass spectrometer resulted in the identification of 816 proteins. We followed rigorous filtering criteria that consisted of PC‐specific information obtained from three publicly available databases (Oncomine, Protein Atlas and Unigene) to segregate 20 putative biomarker candidates for future validation. Since these proteins are of membranous and extra‐cellular origin, most are glycosylated, and many of them are over‐expressed in cancer tissues, the probability of these proteins entering the peripheral blood circulation is high. Their validation as serological PC biomarkers in the future is highly warranted.     

Friend or food: Different cues to the autophagosomal proteome

A hallmark of macroautophagy is the formation of autophagosomes, double-membrane vesicles that enwrap cellular components destined for lysosomal degradation. We examined autophagosomal protein dynamics under various inducing stimuli using a comprehensive mass spectrometry-based proteomics approach in combination with functional studies in yeast and human cell cultures. Time frame and stimuli type influenced the autophagosome proteome, underlining the dynamic constitution of the organelle. We identified both a core set of proteins always localizing to autophagosomes and stimulus-dependent components that will serve as a resource for further characterization of the autophagosomal machinery and cargo selection. Among the core proteins were newly discovered autophagy regulators found to be conserved from yeast to humans, as well as the proteasome.     

Clinical proteomics-driven precision medicine for targeted cancer therapy: current overview and future perspectives

Cancer is a common disease that is a leading cause of death worldwide. Currently, early detection and novel therapeutic strategies are urgently needed for more effective management of cancer. Importantly, protein profiling using clinical proteomic strategies, with spectacular sensitivity and precision, offer excellent promise for the identification of potential biomarkers that would direct the development of targeted therapeutic anticancer drugs for precision medicine. In particular, clinical sample sources, including tumor tissues and body fluids (blood, feces, urine and saliva), have been widely investigated using modern high-throughput mass spectrometry-based proteomic approaches combined with bioinformatic analysis, to pursue the possibilities of precision medicine for targeted cancer therapy. Discussed in this review are the current advantages and limitations of clinical proteomics, the available strategies of clinical proteomics for the management of precision medicine, as well as the challenges and future perspectives of clinical proteomics-driven precision medicine for targeted cancer therapy.     

The human urinary proteome: combinational approaches to comprehensive mapping

The development methodologies for the assessment of the protein content of biological samples have been in the ‘eye of the storm’ in proteomics for almost two decades. The work of Zerefos et al. is a continuation of this trend, focusing on analysis of urinary proteins using a combination of separation methodologies. In this work, the authors employ a previously analyzed control urine sample. Three different methodologies are presented, involving the combination of classical separation approaches, such as SDS-PAGE, preparative electrophoresis and liquid chromatography and standard mass spectrometer instrumentation. Several hundred proteins were reported following the application of a typical proteomics workflow and the use of a data meta-analysis platform to enhance the credibility of the final output. This is also established through cross-method (within this study) as well as cross-study (comparison of this with other main studies in the field) data comparisons. Emphasis is placed on the presentation of experimental identifiers as well as information provided at the peptide level.     

From coarse to fine: the absolute Escherichia coli proteome under diverse growth conditions

Accurate measurements of cellular protein concentrations are invaluable to quantitative studies of gene expression and physiology in living cells. Here, we developed a versatile mass spectrometric workflow based on data‐independent acquisition proteomics (DIA/SWATH) together with a novel protein inference algorithm (xTop). We used this workflow to accurately quantify absolute protein abundances in Escherichia coli for > 2,000 proteins over > 60 growth conditions, including nutrient limitations, non‐metabolic stresses, and non‐planktonic states. The resulting high‐quality dataset of protein mass fractions allowed us to characterize proteome responses from a coarse (groups of related proteins) to a fine (individual) protein level. Hereby, a plethora of novel biological findings could be elucidated, including the generic upregulation of low‐abundant proteins under various metabolic limitations, the non‐specificity of catabolic enzymes upregulated under carbon limitation, the lack of large‐scale proteome reallocation under stress compared to nutrient limitations, as well as surprising strain‐dependent effects important for biofilm formation. These results present valuable resources for the systems biology community and can be used for future multi‐omics studies of gene regulation and metabolic control in E. coli.     

The proteome of the presynaptic active zone: from docked synaptic vesicles to adhesion molecules and maxi-channels

The presynaptic proteome controls neurotransmitter release and the short and long term structural and functional dynamics of the nerve terminal. Using a monoclonal antibody against synaptic vesicle protein 2 we immunopurified a presynaptic compartment containing the active zone with synaptic vesicles docked to the presynaptic plasma membrane as well as elements of the presynaptic cytomatrix. Individual protein bands separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis were subjected to nanoscale-liquid chromatography electrospray ionization-tandem mass spectrometry. Combining this method with 2-dimensional benzyldimethyl- n -hexadecylammonium chloride/sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization time of flight and immunodetection we identified 240 proteins comprising synaptic vesicle proteins, components of the presynaptic fusion and retrieval machinery, proteins involved in intracellular signal transduction, a large variety of adhesion molecules and proteins potentially involved in regulating the functional and structural dynamics of the pre-synapse. Four maxi-channels, three isoforms of voltage-dependent anion channels and the tweety homolog 1 were co-isolated with the docked synaptic vesicles. As revealed by in situ hybridization, tweety homolog 1 reveals a distinct expression pattern in the rodent brain. Our results add novel information to the proteome of the presynaptic active zone and suggest that in particular proteins potentially involved in the short and long term structural modulation of the mature presynaptic compartment deserve further detailed analysis.     

Advances in mass spectrometry-based cancer research and analysis: from cancer proteomics to clinical diagnostics

Introduction: The last 20 years have seen significant improvements in the analytical capabilities of biological mass spectrometry (MS). Studies using advanced MS have resulted in new insights into cell biology and the etiology of diseases as well as its use in clinical applications.

Areas covered: This review discusses recent developments in MS-based technologies and their cancer-related applications with a focus on proteomics. It also discusses the issues around translating the research findings to the clinic and provides an outline of where the field is moving.

Expert commentary: Proteomics has been problematic to adapt for the clinical setting. However, MS-based techniques continue to demonstrate potential in novel clinical uses beyond classical cancer proteomics.     

The discovery of protein biomarkers in pre-eclampsia: the promising role of mass spectrometry

Abstract

Context: Pre-eclampsia (PE) is a common hypertensive disorder of pregnancy that substantially affects maternal and neonatal morbidity and mortality worldwide. The aetiology of the disease remains poorly understood with lack of reliable diagnostic tests. PE is a multisystem disorder so it is very unlikely that a single or a small group of biomarkers will accurately predict the disease. Mass spectrometry (MS) is indispensable analytical tool in protein analysis studies. MS-based proteomics have the ability to detect the entire protein complement to provide a useful window into a range of biological processes and allow the identification of differentially expressed proteins between samples.

Objective: The aim of this review is to summarise, discuss and evaluate the current predominant MS-based approaches applied for protein biomarker discovery. The paper also seeks to evaluate the current potential PE biomarkers described in the literature and identify issues that can guide future research.

Conclusion: MS-based proteomics studies are promising alternatives to classical hypothesis-driven approaches to discover novel biomarkers and provide new insights into the underlying phathophysiological mechanisms of PE. This should aid in the early diagnosis of PE and the understanding of the aetiology of the disease.     

Tackling the plant proteome: practical approaches, hurdles and experimental tools

The study of complex biological questions through comparative proteomics is becoming increasingly attractive to plant biologists as the rapidly expanding plant genomic and expressed sequence tag databases provide improved opportunities for protein identification. This review focuses on practical issues associated with comparative proteomic analysis, including the challenges of effective protein extraction and separation from plant tissues, the pros and cons of two-dimensional gel-based analysis and the problems of identifying proteins from species that are not recognized models for functional genomic studies. Specific points are illustrated using data from an ongoing study of the tomato and pepper fruit proteomes.     

Platelet proteomics: from discovery to diagnosis

Introduction: Platelets are the smallest cells within the circulating blood with key roles in physiological hemostasis and pathological thrombosis regulated by the onset of activating/inhibiting processes via receptor responses and signaling cascades.

Areas covered: Proteomics as well as genomic approaches have been fundamental in identifying and quantifying potential targets for future diagnostic strategies in the prevention of bleeding and thrombosis, and uncovering the complexity of platelet functions in health and disease. In this article, we provide a critical overview on current functional tests used in diagnostics and the future perspectives for platelet proteomics in clinical applications.

Expert commentary: Proteomics represents a valuable tool for the identification of patients with diverse platelet associated defects. In-depth validation of identified biomarkers, e.g. receptors, signaling proteins, post-translational modifications, in large cohorts is decisive for translation into routine clinical diagnostics.     

Immunoaffinity techniques coupled to mass spectrometry for the analysis of human peptide hormones: advances and applications

Introduction: The accurate and comprehensive determination of peptide hormones from biological fluids has represented a considerable challenge to analytical chemists for decades. Besides long-established bioanalytical ligand binding assays (or ELISA, RIA, etc.), more and more mass spectrometry-based methods have been developed recently for purposes commonly referred to as targeted proteomics. Eventually the combination of both, analyte extraction by immunoaffinity and subsequent detection by mass spectrometry, has shown to synergistically enhance the test methods’ performance characteristics.

Areas covered: The review provides an overview about the actual state of existing methods and applications concerning the analysis of endogenous peptide hormones. Here, special focus is on recent developments considering the extraction procedures with immobilized antibodies, the subsequent separation of target analytes, and their detection by mass spectrometry.

Expert commentary: Key aspects of procedures aiming at the detection and/or quantification of peptidic analytes in biological matrices have experienced considerable improvements in the last decade, particularly in terms of the assays’ sensitivity, the option of multiplexing target compounds, automatization, and high throughput operation. Despite these advances and progress as expected to be seen in the near future, immunoaffinity purification coupled to mass spectrometry is not yet a standard procedure in routine analysis compared to ELISA/RIA.     

Targeted proteomics of solid cancers: from quantification of known biomarkers towards reading the digital proteome maps

The concept of personalized medicine includes novel protein biomarkers that are expected to improve the early detection, diagnosis and therapy monitoring of malignant diseases. Tissues, biofluids, cell lines and xenograft models are the common sources of biomarker candidates that require verification of clinical value in independent patient cohorts. Targeted proteomics – based on selected reaction monitoring, or data extraction from data-independent acquisition based digital maps – now represents a promising mass spectrometry alternative to immunochemical methods. To date, it has been successfully used in a high number of studies answering clinical questions on solid malignancies: breast, colorectal, prostate, ovarian, endometrial, pancreatic, hepatocellular, lung, bladder and others. It plays an important role in functional proteomic experiments that include studying the role of post-translational modifications in cancer progression. This review summarizes verified biomarker candidates successfully quantified by targeted proteomics in this field and directs the readers who plan to design their own hypothesis-driven experiments to appropriate sources of methods and knowledge.     

From genome to proteome: back to the future. Report on the 7th Siena meeting, September 3-7, 2006

This report reviews the 7th Siena Meeting 'From Genome to Proteome: Back to the Future' which took place in Italy from 3-7 September, 2006. There was a significant rise in the number of delegates attending compared with previous Siena meetings. A diversity of speakers and presentations addressed the theme of the meeting in moving proteomics forward to integrate with biology as a whole entity rather than in isolated fractions. In addition, technological advancements in sample preparation and separation as well as identification were discussed.     

Advances in endometrial cancer protein biomarkers for use in the clinic

Introduction: Endometrial cancer (EC) is the fourth most common cancer in women in developed countries. The identification of sensitive and specific biomarkers to improve early detection of EC is crucial for an appropriate management of this disease, in which 30% of patients are diagnosed only at advanced stages, which is associated with high levels of morbidity and mortality. Despite major efforts and investments made to identify EC biomarkers, no protein has yet reached the stage of clinical application.

Areas covered: This review gathers the numerous candidate biomarkers for EC diagnosis proposed in proteomic studies published from 1978 to 2017. Additionally, we summarize limitations associated with the proteomic technologies and study designs employed in those articles. Finally, we address new perspectives in EC biomarker research, including the comprehensive knowledge of previously suggested candidate biomarkers in conjunction with novel mass spectrometry-based proteomic technologies with enhanced sensitivity and specificity not yet applied to EC studies and a directed clinical perspective in the study design.

Expert commentary: These ingredients could be the recipe to accelerate the application of protein biomarkers in the clinic.     

Recent findings from the human proteome project: opening the mass spectrometry toolbox to advance cancer diagnosis,surveillance and treatment

The Human Proteome Project stands to eclipse the Human Genome Project in terms of scope, content and interpretation. Its outputs, in conjunction with recent developments across the proteomics community, provide new tools for cancer research with the potential of providing clinically relevant insights into the disease. These collectively may guide the development of future diagnosis, surveillance and treatment strategies. Having established a robust organizational framework within the international community, the Human Proteome Organization and the proteomics community at large have made significant advances in biomarker discovery, detection, molecular imaging and in exploring tumor heterogeneity. Here, the authors discuss some developments in cancer proteomics and how they can be implemented to reduce the global burden of the disease.