Analysis of the association between salivary proteins and oral mucositis in patients with head and neck cancer undergoing IMRT: a longitudinal study

INTRODUCTION

This longitudinal study assessed the association between salivary protein composition and the clinical onset/severity of oral mucositis (OM) in patients with head and neck tumours treated with intensity-modulated-radiotherapy (IMRT).

METHODS

Saliva samples/clinical data were obtained from 40 head and neck cancer patients treated at Guy's Hospital before -IMRT(T0) and after-IMRT (T1 = 6 m, T2 = 12 m) (ethics approval/consent). Salivary flow rate, total protein concentration, and secretion rate were determined from saliva samples and compared with pre-treatment values. OM was assessed, total/specific salivary proteins, including mucin 5B and 7, IgA, cystatin-S, albumin, and α-amylase, were quantified.

RESULTS

95% patients experienced OM during IMRT, with 33 subjects reaching grade 2&3. At T1, there was a significant reduction in salivary flow rate, total protein secretion rate, α-amylase and cystatin-S compared to baseline. Remarkably IMRT did not significantly alter mucin 5B and 7, or the IgA secretion rate at any time point. At T1, all the analyzed proteins were associated with the OM outcomes. In addition, there was a significant inverse correlation between IgA concentration at T0 and the severity of OM during IMRT.

CONCLUSION

This study revealed significant associations between several salivary proteins and OM in patients with head and neck cancer undergoing IMRT. Further longitudinal studies are needed to confirm these results.

CLINICAL SIGNIFICANCE

The study contributes to the understanding of certain salivary proteins association with OM. This could be the first step towards identifying potential salivary markers that could offer perspectives for personalized medicine approaches to improve their quality of life (QoL).

RESEARCH QUESTION

What is the association between salivary proteins and the occurrence and severity of OM in head and neck cancer patients?

AIM

To assess the association between salivary protein composition with the clinical onset/severity of oral mucositis (OM) in head and neck cancer patients treated with intensity modulated radiotherapy.

NULL HYPOTHESIS

There is no association between salivary proteins and onset/severity of OM in HNC patients.

Is tear proteome profile a predictor of developing uveitis in ANA-positive patients with oligoarticular juvenile idiopathic arthritis?

PURPOSE

Although less than one-third of anti-nuclear antibody (ANA) positive patients with oJIA develop uveitis, ANA positivity is still the most well-known marker for assessing the risk of uveitis in oligoarticular JIA (oJIA). Therefore, novel biomarkers are needed to better assess the risk of developing uveitis. For this purpose, we performed a comparative tear proteome analysis of uveitis patients to reveal the identity of differentially regulated proteins.

DESIGN

Tear samples were collected using the Schirmer strips in 7 oJIA and 7 oJIA patients with uveitis (oJIA-U). All oJIA-U patients had developed bilateral anterior uveitis and were inactive and topical treatment-free.

METHODS

The nHPLC LC-MS/MS system was used for protein identification and label-free proteome comparisons. The PANTHER and STRING analyses were carried out using UniProt accession numbers of the identified proteins.

RESULTS

Patient characteristics, e.g., age, gender, disease duration, and treatments were similar. For protein identification, three different databases were searched. Twenty-two, 147, and 258 database searches, respectively. Of these, 15 were common to all three proteome databases. Of these 15 proteins, 10 proteins were upregulated, and 2 were downregulated, based on the twofold regulation criteria. The upregulated proteins were, namely, cystatin-S, secretoglobin family 1D member, opiorphin prepropeptide, mammaglobin-B, lysozyme C, mesothelin, immunoglobulin kappa constant, extracellular glycoprotein lacritin, beta-2-microglobulin, and immunoglobulin J chain. The downregulated proteins were dermcidin and prolactin-inducible protein. Among the differentially regulated proteins, cystatin-S was the most regulated protein with an 18-fold upregulation ratio in tear samples from uveitis patients.

CONCLUSION

Here, the identities and regulation ratios of several proteins were revealed when tear samples from uveitis patients were compared to patients without uveitis. These proteins are putative biomarkers for assessing uveitis risk and require further attention.

A Pilot Study of a Panel of Ocular Inflammation Biomarkers in Patients with Primary Sjögren’s Syndrome

Ocular diseases have a strong impact on individuals, the effects of which extend from milder visual impairment to blindness. Due to this and to their prevalence, these conditions constitute important health, social and economic challenges. Thus, improvements in their early detection and diagnosis will help dampen the impact of these conditions, both on patients and on healthcare systems alike. In this sense, identifying tear biomarkers could establish better non-invasive approaches to diagnose these diseases and to monitor responses to therapy. With this in mind, we developed a solid phase capture assay, based on antibody microarrays, to quantify S100A6, MMP-9 and CST4 in human tear samples, and we used these arrays to study tear samples from healthy controls and patients with Sjögren’s Syndrome, at times concomitant with rheumatoid arthritis. Our results point out that the detection of S100A6 in tear samples seems to be positively correlated to rheumatoid arthritis, consistent with the systemic nature of this autoinflammatory pathology. Thus, we provide evidence that antibody microarrays may potentially help diagnose certain pathologies, possibly paving the way for significant improvements in the future care of these patients.

Intraglandular mesenchymal stem cell treatment induces changes in the salivary proteome of irradiated patients

BACKGROUND

Hyposalivation and xerostomia (dry mouth), are the leading site-effects to treatment of head and neck cancer. Currently, there are no effective therapies to alleviate radiation-induced hyposalivation. Adipose tissue-derived mesenchymal stem/stromal cells (AT-MSCs) have shown potential for restoring salivary gland function. However, the mode of action is unknown. The purpose of the present study was therefore to characterize the effect of AT-MSC therapy on the salivary proteome in previously irradiated head and neck cancer patients.

METHODS

Whole saliva was collected from patients with radiation-induced salivary gland hypofunction (n = 8) at baseline, and 120 days after AT-MSC treatment, and from healthy controls (n = 10). The salivary proteome was characterized with mass spectrometry based proteomics, and data was compared within the AT-MSC group (baseline versus day 120) and between AT-MSC group and healthy controls. Significance levels between groups were determined by using double-sided t-test, and visualized by means of principal component analysis, volcano plots and cluster analysis.

RESULTS

Here we show that 140 human proteins are significantly differentially expressed in saliva from patients with radiation-induced hypofunction versus healthy controls. AT-MSC treatment induce a significant impact on the salivary proteome, as 99 proteins are differentially expressed at baseline vs. 120 days after treatment. However, AT-MSC treatment does not restore healthy conditions, as 212 proteins are significantly differentially expressed in saliva 120 days after AT-MSCs treatment, as compared to healthy controls.

CONCLUSION

The results indicate an increase in proteins related to tissue regeneration in AT-MSCs treated patients. Our study demonstrates the impact of AT-MSCs on the salivary proteome, thereby providing insight into the potential mode of action of this novel treatment approach.

Individual Sweet Taste Perception Influences Salivary Characteristics After Orosensory Stimulation With Sucrose and Noncaloric Sweeteners

Emerging evidence points to a major role of salivary flow and viscoelastic properties in taste perception and mouthfeel. It has been proposed that sweet-tasting compounds influence salivary characteristics. However, whether perceived differences in the sensory properties of structurally diverse sweet-tasting compounds contribute to salivary flow and saliva viscoelasticity as part of mouthfeel and overall sweet taste perception remains to be clarified. In this study, we hypothesized that the sensory diversity of sweeteners would differentially change salivary characteristics in response to oral sweet taste stimulation. Therefore, we investigated salivary flow and saliva viscoelasticity from 21 healthy test subjects after orosensory stimulation with sucrose, rebaudioside M (RebM), sucralose, and neohesperidin dihydrochalcone (NHDC) in a crossover design and considered the basal level of selected influencing factors, including the basal oral microbiome. All test compounds enhanced the salivary flow rate by up to 1.51 ± 0.12 g/min for RebM compared to 1.10 ± 0.09 g/min for water within the 1st min after stimulation. The increase in flow rate was moderately correlated with the individually perceived sweet taste (r = 0.3, p < 0.01) but did not differ between the test compounds. The complex viscosity of saliva was not affected by the test compounds, but the analysis of covariance showed that it was associated (p < 0.05) with mucin 5B (Muc5B) concentration. The oral microbiome was of typical composition and diversity but was strongly individual-dependent (permutational analysis of variance (PERMANOVA): R² = 0.76, p < 0.001) and was not associated with changes in salivary characteristics. In conclusion, this study indicates an impact of individual sweet taste impressions on the flow rate without measurable changes in the complex viscosity of saliva, which may contribute to the overall taste perception and mouthfeel of sweet-tasting compounds.

Salivary Proteomics Markers for Preclinical Sjögren’s Syndrome: A Pilot Study

Primary Sjögren’s syndrome (pSS) is a complex autoimmune disorder that particularly affects the salivary and lachrymal glands, generally causing a typical dryness of the eyes and of the mouth. The disease encompasses diverse clinical representations and is characterized by B-cell polyclonal activation and autoantibodies production, including anti-Ro/SSA. Recently, it has been suggested that autoantibody profiling may enable researchers to identify susceptible asymptomatic individuals in a pre-disease state. In this pilot study, we used mass spectrometry to analyze and compare the salivary proteomics of patients with established pSS and patients with pre-clinical SS, identifying a common protein signature in their salivary fluid. We found that several inflammatory, immunity-related, and typical acinar proteins (such as MUC5B, PIP, CST4, and lipocalin 1) were differently expressed in pSS and in pre-clinical SSA+ carriers, compared to healthy controls. This suggests that saliva may closely reflect exocrine gland inflammation from the early phases of the disease. This study confirms the value of salivary proteomics for the identification of reliable biomarkers for SS that could be identified, even in a preclinical phase of the disease.

Tear and ocular surface disease biomarkers: A diagnostic and clinical perspective for ocular allergies and dry eye disease

Validated biomarkers to be used as biological tools for managing ocular surface diseases (OSDs) are still an unmet need in daily clinical practice. Many studies have contributed to the already extensive list of candidate biomarkers for these disorders. Dry eye (DE) and ocular allergy (OA) are complex and multifactorial diseases, often coexisting and with overlapping symptoms. The purpose of this review is to present a comprehensive updated revision of the most relevant biomarkers of DE and OA, with an emphasis on quantitative analyses and correlations with clinical parameter data. Analysis of biomarkers common for these pathologies has highlighted an important physiological process. Namely, the interleukin proteins (IL-1α, IL-1β and IL-17), tumour necrotic factor (TNFα) and interferon gamma (IFNγ; Th1-Th7 pathway) and IL-4, IL-5 and IL-13 (Th2 pathway) seem to represent similar inflammatory mechanisms. Moreover, changes in the levels of mucins (MUC1, MUC2, MUC4, MUC5 and MUC16) are common alterations in the tear film mucous layer. We also examine the current state of medical devices and the main limitations to their use in clinical practice. Translational research in biomarkers for clinical practice depends on a feasible transition from the laboratory to the point-of-care. This requires large-scale, coordinated clinical validation campaigns to select the biomarkers with the highest specificity and sensitivity and significant correlation with clinical parameters. Moreover, technical limitations of multiplexed quantitation systems must be overcome to detect and measure the levels of several biomarkers in very small samples. To ensure the future of biomarker research, significant progress is necessary in a number of fields. There is an urgent need for global unification of clinical classification and diagnostics criteria. Widespread integration of proteomic and transcriptomic data is paramount for performing meaningful analyses using appropriate bioinformatics tools and artificial intelligence systems.

MicroRNA-mRNA expression profiles and functional network after injection of botulinum toxin type A into submandibular glands

Botulinum toxin type A (BTXA) is effective for the treatment of sialorrhea. MicroRNAs (miRNAs) have significant functions in salivary diseases, but the role of miRNAs during BTXA-inhibited salivary secretion is not yet clear. A total of 19 differentially expressed (DE) miRNAs and 1072 DE mRNAs were identified following BTXA injected into submandibular glands of rats (n = 4) through miRNA sequencing and microarray analysis. Bioinformatic analysis identified that several pathways may be associated with the inhibition of salivary secretion, such as the MAPK signalling pathway, tight junctions, and cytokine-cytokine receptor interaction. We predicted the target genes of DE miRNAs and established the miRNA-mRNA interaction network. The intersection of DE mRNAs and target genes of DE miRNAs was performed and seven mRNAs were obtained: Egr2, Paqr9, Zkscan1, Usp6n, Cyb561a3, Zfhx4, and Clic5. These findings explore the mechanism of BTXA in inhibiting salivary secretion and probably will provide new ideas for clinical application.

Prognostic value of immune-related cells and genes in the tumor microenvironment of ovarian cancer, especially CST4

Ovarian cancer (OC) is the most common gynecological malignant tumor with the highest mortality rate. However, identification of effective immune therapeutic targets and biomarkers are beset by many challenges. CIBERSORT was used to calculate the abundance of 22 immune cell types in 379 OC samples, and indicated that three immune cell types were associated with poor prognoses. Further analysis revealed that 17 hub genes were associated with these three cell types. We screened differentially expressed immune-related prognostic gene associated with clinicopathological factors, which was CST4. We used clinical specimens to detect the expression of CST4, and determined that CST4 was both highly expressed in OC patients and associated with poor prognoses. Our findings indicated that infiltration of immune cells affected the survival of patients with OC, provided therapeutic targets represented by CST4, deepened our understanding of the immune microenvironment of OC, and enhanced the theoretical basis of immunotherapy.

Radiotherapy changes acquired enamel pellicle proteome in head and neck cancer patients

OBJECTIVES

To evaluate in vivo the proteomic profile of the acquired enamel pellicle (AEP) in patients with head and neck cancer (HNC) before, during and after radiotherapy.

METHODS

Nine patients, after prophylaxis, had their AEPs collected before (BRT), during (DRT; 2-5 weeks) and after (ART; 3-4 months) radiotherapy. AEP was also collected from nine healthy patients (Control). The proteins were extracted in biological triplicate and processed by label-free proteomics.

RESULTS

Statherin was increased more than 9-fold and several hemoglobin subunits were increased more than 5-fold DRT compared to BRT, while lactotransferrin, proline-rich proteins, cystatins, neutrophil defensins 1 and 3 and histatin-1 were decreased. ART, there was an increase in lactotransferrin and several isoforms of histones, while statherin and alpha-amylase proteins were decreased. MOAP-1 was exclusively found ART in comparison to BRT. When compared to Control, AEP of patients BRT showed an increase in proteins related to the perception of bitter taste, mucin-7 and alpha-amylases, while cystatin-S was decreased.

CONCLUSIONS

HNC and radiotherapy remarkably altered the proteome of the AEP. Antibacterial and acid-resistant proteins were decreased during radiotherapy.

CLINICAL SIGNIFICANCE

Our results provide important information for designing more effective dental products for these patients, in addition to contributing to a better understanding of the differential protective roles of the AEP proteins during radiotherapy. Moreover, some proteins identified in the AEP after radiotherapy may serve as prognostic markers for survival of HNC patients.

A Tutorial on Saliva's Role in Swallowing With a Focus on Sjögren's Syndrome

Purpose Saliva is integral to swallowing and necessary for oral health. Understanding saliva's origin and properties is important for swallowing assessment and management. Diseases such as Sjögren's syndrome (SS) can affect saliva negatively, often contributing to dysphagia. Our objectives are to (a) highlight saliva's fundamental role in swallowing, (b) provide a bibliometric overview of literature pertaining to SS pathophysiology and effects on saliva, (c) explore implications of salivary changes on swallowing and quality of life in SS and other populations, and (d) provide suggestions for systematic saliva assessment in practice. Method This tutorial reviews saliva production, composition, and involvement in swallowing within health and disease. Using rapid review methodology, we outline the effect of SS on saliva and describe SS etiology, diagnosis, and treatment. We discuss formal saliva assessments and a multidisciplinary approach. Results Saliva plays a vital role in swallowing, particularly lubrication, bolus formation, and oral health. SS affects the salivary glands altering salivary flow rate and composition. We identified 55 studies (N) measuring salivary changes, grouping them according to four strata demarcated by SS classification criteria updates. For some, xerostomia, dysphagia, and reduced life quality result. Formal saliva assessments include the Clinical Oral Dryness Score, Xerostomia Inventory, and Secretion Rating Scale. Multidisciplinary care is optimal for patients with salivary changes. Conclusion Understanding salivary changes in disease may enhance understanding of swallowing and inform dysphagia practice. Expanding swallowing assessments with formal saliva evaluations, and patient perspectives thereof, may aid in developing bespoke treatments, ultimately improving outcomes and quality of life. Supplemental Material https://doi.org/10.23641/asha.12456449.

Analysis of salivary factors related to the oral health status in children

Early detection of oral disease is important to reduce its severity and increase the likelihood of successful treatment. This study aimed to perform a quantitative assessment of the saliva components as a first stage of the research to screen oral homeostasis. Here, saliva secretions collected from children were evaluated, and their constituents were analyzed to investigate the potential correlations between the buffering capacity and a range of salivary factors. Subjects aged 3-16 years in the primary, mixed, or permanent dentition stage, were selected for this study. The following salivary factors were analyzed: flow rate, total protein, total sugar quantifications, and constituent analyses using RT-PCR and western blotting. The associations between each factor and the buffering capacity were then analyzed using multiple regression analysis. Flow rate, BPIFA2 RNA level, histatin 1 and BPIFB1 protein levels as well as female sex were positively associated with buffering capacity. In contrast, total sugar concentration and MUC7 RNA levels showed a negative relationship with the buffering capacity. Some of these constituents may indicate oral homeostasis and are therefore potential biomarkers of oral health status. These results suggest that the analyses of the correlations between oral homeostasis and salivary factors are an effective strategy for identifying the susceptibility to oral diseases.

MicroRNA expression profile of Lacrimal Glands in rabbit autoimmune dacryoadenitis model

Purpose: To identify the differential expression of microRNAs (miRs) and the related gene networks and signal pathways in lacrimal glands (LGs) of rabbit autoimmune dacryoadenitis. Methods: Autoimmune dacryoadenitis in rabbits was induced by transferring activated peripheral blood lymphocytes (PBLs). The LGs of normal and model group rabbits were collected for small RNA sequencing. The most differentially expressed miRs were validated by quantitative real time-polymerase chain reaction (qRT-PCR). Further, bioinformatics analysis including target gene prediction, Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed. Results: A total of 15 miRs were differentially expressed in the LGs of rabbit autoimmune dacryoadenitis relative to normal controls. GO and KEGG analysis revealed that most target genes of these dysregulated miRs were implicated in MAPK signaling pathway. Conclusion: Our results showed for the first time the differentially expressed miRs and the related pathways involved in the pathogenesis of rabbit autoimmune dacryoadenitis. These results may contribute to elucidating molecular pathogenesis of Sjögren's syndrome (SS) dry eye.

Epigenetics in Primary Sjögren's Syndrome

Primary Sjögren's syndrome (SjS) is a chronic and systemic autoimmune epithelitis with predominant female incidence, which is characterized by exocrine gland dysfunction. Incompletely understood, the etiology of SjS is multi-factorial and evidence is growing to consider that epigenetic factors are playing a crucial role in its development. Independent from DNA sequence mutations, epigenetics is described as inheritable and reversible processes that modify gene expression. Epigenetic modifications reported in minor salivary gland and lymphocytes from SjS patients are related to (i) an abnormal DNA methylation process inducing in turn defective control of normally repressed genes involving such matters as autoantigens, retrotransposons, and the X chromosome in women; (ii) altered nucleosome positioning associated with autoantibody production; and (iii) altered control of microRNA. Results from epigenome-wide association studies have further revealed the importance of the interferon pathway in disease progression, the calcium signaling pathway for controlling fluid secretions, and a cell-specific cross talk with risk factors associated with SjS. Importantly, epigenetic modifications are reversible thus opening opportunities for therapeutic procedures in this currently incurable disease.

Phenotyping multiple subsets in Sjögren's syndrome: a salivary proteomic SWATH-MS approach towards precision medicine

Background

This proof of concept study was aimed at characterizing novel salivary biomarkers specific for different subsets in primary Sjögren's syndrome (pSS) in order to improve patients' profiling.

Methods

pSS patients were stratified in three subgroups according to both (a) focus score in the minor salivary gland biopsies (i.e. intensity of immune cell infiltration in the tissue) and (b) unstimulated salivary flow rate. Healthy volunteers were included as controls. A nano-HPLC-SWATH-MS approach was used for the analysis of saliva proteome of different subsets.

Results

We found 203 differentially expressed proteins in pSS patients with respect to controls with evident differences in the expression of normal constituents of the human salivary proteome (i.e. prolactin-inducible protein, proline-rich proteins, cystatins) and several mediators of inflammatory processes. The comparative analysis of the pSS phenotypes unrevealed 63 proteins that were shared and specifically modulated in the three subsets of pSS patients converging on several inflammatory pathways. Among them S100A protein appeared of particular interest merging on IL-12 signaling and being significantly influenced by either salivary flow impairment or intensity of immune cell infiltration in the tissue.

Conclusions

Constellations of proteins, including S100A proteins, characterize different pSS subsets reflecting either salivary gland dysfunction or inflammation. Salivary proteomics may foster future research projects ultimately aimed at developing personalized treatments for pSS patients.

Soluble siglec-5 is a novel salivary biomarker for primary Sjogren's syndrome

Despite advances in the understanding of the pathogenesis, disease-specific biomarkers have not been included in the classification criteria for Primary Sjogren's syndrome (pSS). Based on a microarray of peripheral blood mononuclear cells (PBMCs) from patients with primary Sjogren's syndrome (pSS), we aimed to investigate whether soluble sialic acid-binding immunoglobulin-like lectin (siglec)-5 in saliva might be a biomarker for pSS. The concentration of siglec-5 in saliva and sera was determined by ELISA. Clinical parameters related with pSS were obtained from pSS registry and correlation with salivary siglec-5 level was evaluated. Receiver operating curve (ROC) analysis was performed to determine cut off value. A separate validation cohort consisted of subjects with suspicious pSS was evaluated to determine the performance. The level of salivary siglec-5 was significantly higher in pSS patients (n = 170) compared with HCs (n = 25), non SS sicca patients (n = 78) or patients with systemic lupus erythematosus (SLE) (n = 43) (1346.8 [202.8-4280.0] pg/mL, 6.08 [0-134.0] pg/mL, 195 [0-947.5] pg/mL, and 0 [0-238.7] pg/mL, median [interquartile range], P < 0.001). Salivary siglec-5 level negatively correlated with salivary flow rate (spearman's rho: -0.420, P < 0.001), and positively correlated with ocular surface score (rho: 0.331, P < 0.001) and serum immunoglobulin G level (rho = 0.202, P = 0.008). In ROC analysis, area under the curve was 0.774[0.724-0.826]. With a cut off value of 400 pg/mL, sensitivity and specificity was 0.69 and 0.70 respectively. In validation cohort (45 pSS patients and 45 non SS sicca patients), sensitivity and specificity of siglec-5 was 64.4% and 77.8%, respectively. In conclusion, the level of soluble siglec-5 is significantly higher in the saliva from pSS patients, which reflects the severity of hyposalivation and ocular surface damage. This novel salivary biomarker may provide benefits for pSS diagnosis.

MicroRNAs in Autoimmune Sjögren's Syndrome

MicroRNAs (miRNAs), small non-coding RNAs, have been implicated in various diseases and cellular functions as microregulators of gene expression. Although the history of miRNA investigation in autoimmune Sjögren’s syndrome (SjS) is fairly short, a substantial amount of data has already been accumulated. These findings clearly indicate potential clinical implications of miRNAs, such as autoantigen expression and autoantibody production, viral miRNAs regulating the calcium signaling pathway, and aberrant immune cell regulation and cytokine production. Research endeavors in the field are currently underway to select disease-specific diagnostic and prognostic biomarkers by utilizing different types of tissues or biological specimens of SjS patients. Various techniques for miRNA analysis with different stringencies have been applied, with the most recent one being next-generation sequencing. This review compiles and highlights differentially-expressed miRNAs in various samples collected from SjS patients and their potential implications in the pathogenesis of SjS. To facilitate the development of miRNA-targeted personalized therapy in the future, we urge more follow-up studies that confirm these findings and elucidate the immunopathological roles of differentially-expressed miRNAs. Furthermore, improved diagnostic criteria for the disease itself will minimize sampling errors in patient recruitment, preventing the generation of inconsistent data.

Salivary Cystatins: Exploring New Post-Translational Modifications and Polymorphisms by Top-Down High-Resolution Mass Spectrometry

Cystatins are a complex family of cysteine peptidase inhibitors. In the present study, various proteoforms of cystatin A, cystatin B, cystatin S, cystatin SN, and cystatin SA were detected in the acid-soluble fraction of human saliva and characterized by a top-down HPLC-ESI-MS approach. Proteoforms of cystatin D were also detected and characterized by an integrated top-down and bottom-up strategy. The proteoforms derive from coding sequence polymorphisms and post-translational modifications, in particular, phosphorylation, N-terminal processing, and oxidation. This study increases the current knowledge of salivary cystatin proteoforms and provides the basis to evaluate possible qualitative/quantitative variations of these proteoforms in different pathological states and reveal new potential salivary biomarkers of disease. Data are available via ProteomeXchange with identifier PXD007170.

Biomarkers for Sjögren's syndrome

Sjögren's syndrome (pSS) is a complex and heterogeneous disorder characterized by different clinical subsets. Recently, great efforts have been made searching for reliable biomarkers able to ameliorate the diagnostic algorithm and the prognostic stratification of pSS patients and ultimately allowing the scientific community to address some of the unmet needs for the disease. In this review, we have summarized the state of the art of 'traditional' widely acknowledged clinical, serological and histologic biomarkers for pSS with the aim of highlighting their relevance and limitations in clinical practice. We have also explored some of the novel potential biomarkers that have been proposed more recently, potentially able to open new ways in the assessment of the disease.

Updates on Sjögren's syndrome: from proteomics to protein biomarkers

INTRODUCTION

Primary Sjögren's syndrome (pSS) is a complex heterogeneous autoimmune disorder, typically affecting exocrine glands. Recently, a great interest has arisen in searching for novel biomarkers able to improve the diagnostic work-up of the disease as well as the general assessment and the prognostic stratification of pSS patients. From this perspective, salivary proteomics has appeared as a promising tool considering that salivary proteins may closely reflect the underlying disease processes in the salivary glands. Areas covered: Here we will provide an update on the state of the art of proteomics in pSS, focusing in particular on putative novel biomarkers for the disease. There is a special focus on candidate salivary protein and their role in non-invasive diagnosis of pSS. Expert commentary: Proteomics represents an emerging throughput omics-based approach for use in diagnosis of pSS. The studies that have been presented in this review have provided major contributions towards the identification of putative protein biomarkers, that once validated, could be able not only to contribute to a non-invasive diagnosis of pSS but also to the stratification of different disease subsets, ultimately allowing a better comprehension of the disease.