Quantitative proteomic analysis of oral brush biopsies identifies secretory leukocyte protease inhibitor as a promising, mechanism-based oral cancer biomarker

The secretory leukocyte protease inhibitor (SLPI) in pathophysiology of non-communicable diseases: Evidence from experimental studies to clinical applications

Non-communicable diseases (NCDs) are a worldwide health issue because of their prevalence, negative impacts on human welfare, and economic costs. Protease enzymes play important roles in viral and NCD diseases. Slowing disease progression by inhibiting proteases using small-molecule inhibitors or endogenous inhibitory peptides appears to be crucial. Secretory leukocyte protease inhibitor (SLPI), an inflammatory serine protease inhibitor, maintains protease/antiprotease balance. SLPI is produced by host defense effector cells during inflammation to prevent proteolytic enzyme-induced tissue damage. The etiology of noncommunicable illnesses is linked to SLPI's immunomodulatory and tissue regeneration roles. Disease phases are associated with SLPI levels and activity changes in regional tissue and circulation. SLPI has been extensively evaluated in inflammation, but rarely in NCDs. Unfortunately, the thorough evaluation of SLPI's pathophysiological functions in NCDs in multiple research models has not been published elsewhere. In this review, data from PubMed from 2014 to 2023 was collected, analysed, and categorized into in vitro, in vivo, and clinical studies. According to the review, serine protease inhibitor (SLPI) activity control is linked to non-communicable diseases (NCDs) and other illnesses. Overexpression of the SLPI gene and protein may be a viable diagnostic and therapeutic target for non-communicable diseases (NCDs). SLPI is also cytoprotective, making it a unique treatment. These findings suggest that future research should focus on these pathways using advanced methods, reliable biomarkers, and therapy approaches to assess susceptibility and illness progression. Implications from this review will help pave the way for a new therapeutic target and diagnosis marker for non-communicable diseases.

Detection of volatile sulfur compounds (VSCs) in exhaled breath as a potential diagnostic method for oral squamous cell carcinoma

Background

Oral squamous cell carcinoma causes a significant proportion of global cancer morbidity and mortality. The aim of this study is to investigate whether the exhaled breath test can be a new, non-invasive, and effective method for diagnosing oral squamous cell carcinoma.

Methods

A comparative analysis of exhaled breath between patients with oral squamous cell carcinoma (OSCC) and healthy controls (HC) was performed with the Twin Breasor II™, a simple gas chromatography system.

Results

Both hydrogen sulfide (H₂S) and methyl mercaptan (Ch₃SH) were significantly higher in the OSCC group than in the HC group. The total sulfur concentration was also higher in the OSCC group, but there was no significant difference in the ratio of Ch₃SH to H₂S between the two groups. Using logistic regression, we constructed a new variable with an area under the curve (AUC) of 0.740, 68.0% sensitivity, and 72.0% specificity.

Conclusions

Exhaled gas analysis via simple gas chromatography can potentially serve as an accessory non-invasive method for OSCC diagnosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02301-3.

A Systematic Review of Oral Biopsies, Sample Types, and Detection Techniques Applied in Relation to Oral Cancer Detection

Background: Early identification of the stage of oral cancer development can lead to better treatment outcomes and avoid malignant transformation. Therefore, this review aims to provide a comprehensive overview that describes the development of standardized procedures for oral sample collection, characterization, and molecular risk assessment. This can help investigators to choose the appropriate sampling method and downstream analyses for different purposes. Methods: This systematic review was conducted according to the PRISMA guidelines. Using both PubMed and Web of Science databases, four independent authors conducted a literature search between 15 and 21 June 2021. We used key search terms to broaden the search for studies. Non-conforming articles were removed using an EndNote-based and manual approach. Reviewers used a designed form to extract data. Results: This review included a total of 3574 records, after eliminating duplicate articles and excluding papers that did not meet the inclusion criteria. Finally, 202 articles were included in this review. We summarized the sampling methods, biopsy samples, and downstream analysis. The biopsy techniques were classified into tissue and liquid biopsy. The common sequential analysis of tissue biopsy includes histopathological examination such as H&E or IHC to identify various pathogenic features. Meanwhile, liquid samples such as saliva, blood, and urine are analyzed for the purpose of screening to detect mutations in cancer. Commonly used technologies are PCR, RT-PCR, high-throughput sequencing, and metabolomic analysis. Conclusions: Currently, tissue biopsies provide increased diagnostic value compared to liquid biopsy. However, the minimal invasiveness and convenience of liquid biopsy make it a suitable method for mass screening and eventual clinical adoption. The analysis of samples includes histological and molecular analysis. Metabolite analysis is rising but remains scarce.

A systematic review of proteomic biomarkers in oral squamous cell cancer

BACKGROUND

Head and neck squamous cell cancer (HNSCC) is the most common cancer associated with chewing tobacco, in the world. As this is divided in to sites and subsites, it does not make it to top 10 cancers. The most common subsite is the oral cancer. At the time of diagnosis, more than 50% of patients with oral squamous cell cancers (OSCC) had advanced disease, indicating the lack of availability of early detection and risk assessment biomarkers. The new protein biomarker development and discovery will aid in early diagnosis and treatment which lead to targeted treatment and ultimately a good prognosis.

METHODS

This systematic review was performed as per PRISMA guidelines. All relevant studies assessing characteristics of oral cancer and proteomics were considered for analysis. Only human studies published in English were included, and abstracts, incomplete articles, and cell line or animal studies were excluded.

RESULTS

A total of 308 articles were found, of which 112 were found to be relevant after exclusion. The present review focuses on techniques of cancer proteomics and discovery of biomarkers using these techniques. The signature of protein expression may be used to predict drug response and clinical course of disease and could be used to individualize therapy with such knowledge.

CONCLUSIONS

Prospective use of these markers in the clinical setting will enable early detection, prediction of response to treatment, improvement in treatment selection, and early detection of tumor recurrence for disease monitoring. However, most of these markers for OSCC are yet to be validated.

Proteomic approaches to assist in diagnosis and prognosis of oral cancer

Introduction: Oral squamous cell carcinoma (OSCC) ranks among the top 10 leading causes of cancer worldwide, with 5-year survival rate of about 50%, high lymph node metastasis, and relapse rates. The OSCC diagnosis, prognosis, and treatment are mostly based on the clinical TNM classification. There is an urgent need for the discovery of biomarkers and therapeutic targets to assist in the clinical decision-making process.Areas covered: We summarize proteomic studies of the OSCC tumor, immune microenvironment, potential liquid biopsy sites, and post-translational modifications trying to retrieve information in the discovery and verification or (pre)validation phases. The search strategy was based on the combination of MeSH terms and expert refinement.Expert opinion: Untargeted combined with targeted proteomics are strategies that provide reliable and reproducible quantitation of proteins and are the methods of choice of many groups worldwide. Undoubtedly, proteomics has been contributing to the understanding of OSCC progression and uncovers potential candidates as biomarker or therapeutic targets. Nevertheless, none of these targets are available in the clinical practice yet. The scientific community needs to overcome the limitations by investing in robust experimental designs to strengthen the value of the findings, leveraging the translation of knowledge, and further supporting clinical decisions.

Saliva proteomics updates in biomedicine

In the years of personalized (or precision) medicine the 'omics' methodologies in biomedical sciences-genomics, transcriptomics, proteomics and metabolomics-are helping researchers to detect quantifiable biological characteristics, or biomarkers, that will best define the human physiology and pathologies. Proteomics use high throughput and high efficiency approaches with the support of bioinformatic tools in order to identify and quantify the total protein content of cells, tissues or biological fluids. Saliva receives a lot of attention as a rich biological specimen that offers a number of practical and physiological advantages over blood and other biological fluids in monitoring human health. The aim of this review is to present the latest advances in saliva proteomics for biomedicine.

Secretory Leukocyte Protease Inhibitor in Oral Potentially Malignant Disorders and Oral Squamous Cell Carcinoma

Objectives: Secretory leukocyte protease inhibitor (SLPI) is a protein found in body fluids and implicated as a prognostic factor in many cancers. There is limited research regarding serum and salivary SLPI in oral potentially malignant disorders (OPMDs) and oral squamous cell carcinoma (OSCC). Materials and Methods: A total of 90 participants were included in the study; of which 30 formed the control group, 30 included participants with OPMD, and 30 included participants with OSCC. Serum and salivary levels of SLPI were estimated using enzyme-linked immunosorbent assay. Results: Serum levels of SLPI showed progressive increase in potentially malignant disorders and SCC patients when compared with controls, while salivary levels were increased in both OPMD and OSCC groups as compared to controls. However, the difference between groups was not statistically significant (P < 0.05). Conclusion: The above results suggest that increase in SLPI levels in the serum may have a role in indicating progression of OPMD to OSCC.

Secretory leukocyte protease inhibitor suppresses HPV E6-expressing HNSCC progression by mediating NF-κB and Akt pathways

Background

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide and human papillomavirus (HPV) has been increasingly recognized as a pathogenic factor for the initiation and development of HNSCC. E6 oncogene, an essential component of the HPV 16 virus, acts as a leading cause of the malignant transformation of cancer cells. Therefore, investigating the biological effect and potential mechanisms of E6 oncogene on HNSCC cells and exploring potential therapeutic methods is of great value.

Methods

MTT assay, cell cycle analysis, and apoptosis assay were implemented to detect the biological effect of E6 oncogene on the growth of HNSCC cells. Wound healing assay and transwell assay were used to evaluate the role of E6 in the migration and invasion of HNSCC cells. Western blot and immunofluorescence assay were adopted to explore the regulatory mechanisms underlying E6-induced HNSCC progression. Then, exogenous secretory leukocyte protease inhibitor (SLPI) was added into the cell culture to investigate whether it could maintain its tumor suppressor effect on E6-expressing HNSCC cells.

Results

HPV E6 oncogene could promote the proliferation, cell cycle period, apoptosis resistance, migration and invasion of HNSCC cells by activating NF-κB and Akt pathways. Immunohistochemical analysis conducted on HNSCC tissues illustrated that SLPI was further downregulated in HPV positive HNSCC compared to HNSCC without HPV infection. Exogenous SLPI significantly inhibited HPV E6-mediated malignant phenotypes in HNSCC cells by inhibiting the activation of NF-κB and Akt and signaling pathways.

Conclusions

This study demonstrated that E6 oncogene led to the malignant transformation of HNSCC cells by regulating multiple pathways. SLPI could reverse the effect of E6 oncogene on HNSCC, implying that the functional inhibition of E6 by SLPI may be exploited as an attractive therapeutic strategy.

Role of Salivary Biomarkers in Oral Cancer Detection

Oral cancers are the sixth most frequent cancer with a high mortality rate. Oral squamous cell carcinoma accounts for more than 90% of all oral cancers. Standard methods used to detect oral cancers remain comprehensive clinical examination, expensive biochemical investigations, and invasive biopsy. The identification of biomarkers from biological fluids (blood, urine, saliva) has the potential of early diagnosis. The use of saliva for early cancer detection in the search for new clinical markers is a promising approach because of its noninvasive sampling and easy collection methods. Human whole-mouth saliva contains proteins, peptides, electrolytes, organic, and inorganic salts secreted by salivary glands and complimentary contributions from gingival crevicular fluids and mucosal transudates. This diagnostic modality in the field of molecular biology has led to the discovery and potential of salivary biomarkers for the detection of oral cancers. Biomarkers are the molecular signatures and indicators of normal biological, pathological process, and pharmacological response to treatment hence may provide useful information for detection, diagnosis, and prognosis of the disease. Saliva's direct contact with oral cancer lesions makes it more specific and potentially sensitive screening tool, whereas more than 100 salivary biomarkers (DNA, RNA, mRNA, protein markers) have already been identified, including cytokines (IL-8, IL-1b, TNF-α), defensin-1, P53, Cyfra 21-1, tissue polypeptide-specific antigen, dual specificity phosphatase, spermidine/spermineN1-acetyltransferase , profilin, cofilin-1, transferrin, and many more. However, further research is still required for the reliability and validation of salivary biomarkers for clinical applications. This chapter provides the latest up-to-date list of known and emerging potential salivary biomarkers for early diagnosis of oral premalignant and cancerous lesions and monitoring of disease activity.

Assessment of cellular and serum proteome from tongue squamous cell carcinoma patient lacking addictive proclivities for tobacco, betel nut, and alcohol: Case study

The intriguing molecular pathways involved in oral carcinogenesis are still ambiguous. The oral squamous cell carcinoma (OSCC) ranks as the most common type constituting more than 90% of the globally diagnosed oral cancers cases. The elevation in the OSCC incidence rate during past 10 years has an alarming impression on human healthcare. The major challenges associated with OSCC include delayed diagnosis, high metastatic rates, and low 5-year survival rates. The present work foundations on reverse genetic strategy and involves the identification of genes showing expressional variability in an OSCC case lacking addictive proclivities for tobacco, betel nut, and/or alcohol, major etiologies. The expression modulations in the identified genes were analyzed in 16 patients comprising oral pre-cancer and cancer histo-pathologies. The genes SCCA1 and KRT1 were found to down regulate while DNAJC13, GIPC2, MRPL17, IG-Vreg, SSFA2, and UPF0415 upregulated in the oral pre-cancer and cancer pathologies, implicating the genes as crucial players in oral carcinogenesis.

Efficacy of oral brush biopsy in potentially malignant disorder management

BACKGROUND

Oral potentially malignant disorders (PMD) harbour unpredictable risk for squamous cell carcinoma development. Current management requires tissue biopsy for histopathology characterisation, dysplasia grading and targeted intervention to "high-risk" lesions, although evidence-based guidelines are limited and diagnoses subjective. This study investigated the use of adjunctive oral brush biopsy techniques during the management of PMD in a UK hospital population.

METHODS

Retrospective review of a 310 PMD patient cohort presenting to Maxillofacial Surgery in Newcastle upon Tyne with new, single-site lesions between December 2009 and May 2014. Patients underwent Orcellex^® brush biopsy and liquid-based cytology examination in addition to conventional biopsy techniques, with management proceeding along established care pathways. Patient demographics, cytology data, most significant histopathology diagnoses and clinical outcome were all documented at the study census date (31.12.15).

RESULTS

A total of 170 male & 140 female patients (age range 18-91 years), exhibiting primarily leukoplakia (86.5%) at floor of mouth and ventrolateral tongue sites (44.9%), were identified. Management comprised: observation (49.7%), laser surgery (44.9%), antifungal treatment (3.5%) and Head & Neck clinic referral following cancer diagnosis (1.9%). Clinical outcomes were as follows: disease free (51.3%), persistent PMD (42.3%) and malignant transformation (6.4%). Histology and cytology diagnoses strongly correlated (r = .305). Treatment modality, lesion site, histology and cytology diagnoses were the best predictors of clinical outcome.

CONCLUSIONS

Orcellex^® brush cytology provides reliable diagnoses consistent with conventional histopathology and offers less invasive, adjunctive assessment appropriate for long-term monitoring of patients in specialist clinics.

Advances of Salivary Proteomics in Oral Squamous Cell Carcinoma (OSCC) Detection: An Update

Oral cancer refers to malignancies that have higher morbidity and mortality rates due to the late stage diagnosis and no early detection of a reliable diagnostic marker, while oral squamous cell carcinoma (OSCC) is amongst the world’s top ten most common cancers. Diagnosis of cancer requires highly sensitive and specific diagnostic tools which can support untraceable hidden sites of OSCC, yet to be unleashed, for which plenty of biomarkers are identified; the most recommended biomarker detection medium for OSCC includes biological fluids, such as blood and saliva. Saliva holds a promising future in the search for new clinical biomarkers that are easily accessible, less complex, accurate, and cost effective as well as being a non-invasive technique to follow, by analysing the malignant cells’ molecular pathology obtained from saliva through proteomic, genomic and transcriptomic approaches. However, protein biomarkers provide an immense potential for developing novel marker-based assays for oral cancer, hence this current review offers an overall focus on the discovery of a panel of candidates as salivary protein biomarkers, as well as the proteomic tools used for their identification and their significance in early oral cancer detection.

Proteomic profile of saliva and plasma from women with impalpable breast lesions

The present study evaluated the proteomic profile of saliva and plasma from women with impalpable breast lesions using nano-liquid chromatography-quadrupole-time-of-flight (nLC-Q-TOF) technology. Plasma and saliva from patients with fibroadenoma (n=10), infiltrating ductal carcinoma (n=10) and healthy control groups (n=8) were assessed by combinations of inter/intra-group analyses, revealing significant quantitative and qualitative differences. The major differentially-expressed proteins in the saliva of patients compared with the controls were α2-macroglobulin and ceruloplasmin, but the proteins that met the minimum fold-change and P-value cut-offs were leukocyte elastase inhibitor and α-enolase, and deleted in malignant brain tumors 1. Concerning plasma, α-2-macroglobulin and ceruplasmin were upregulated, while other proteins such as haptoglobin, hemopexin and vitamin D-binding protein were downregulated compared with the control. The changes in immune, molecular transport and signaling pathways were the most representative in the proteomic profile of the saliva and plasma. This is the first study to describe the proteome of saliva and plasma from the same women with impalpable breast lesions.

Salivary secretory leukocyte protease inhibitor (SLPI) and head and neck cancer: The Cancer Prevention Study II Nutrition Cohort

OBJECTIVES

Secretory leukocyte protease inhibitor (SLPI) is an innate-immunity protein displaying antimicrobial and anti-inflammatory properties that is found in high concentrations in saliva. The role of extracellular salivary SLPI in head and neck squamous cell carcinoma (HNSCC) remains unclear. Thus, we aimed to evaluate the association between SLPI and HNSCC risk in the Cancer Prevention Study II Nutrition Cohort.

MATERIALS AND METHODS

Among 53,180 men and women with no history of cancer who provided an oral rinse between 2001 and 2002, 60 were subsequently diagnosed with incident HNSCC between specimen collection and June 2009. In this nested case-control study, archived oral supernatants were evaluated using the Human SLPI Quantikine ELISA Kit for all 60 cases and 180 controls individually matched on gender, race, date of birth, and date of oral rinse collection. Conditional logistic regression was used to estimate HNSCC risk.

RESULTS

Overall, pre-diagnostic salivary SLPI was associated with a non-statistically significant higher risk of HNSCC (OR=1.6, 95% CI=0.9-3.0). Among never smokers, high SLPI was associated with a non-statistically significant lower risk (OR=0.5, 95% CI=0.1-1.9), whereas among ever smokers, high SLPI was associated with a statistically significant higher risk (OR=2.1, 95% CI=1.0-4.3) of HNSCC, compared to low SLPI.

CONCLUSION

While results from this study suggest that higher concentrations of salivary SLPI might increase the risk of HNSCC among ever smokers, more research is needed to verify these findings and define the mechanisms by which SLPI and smoking influence the etiology of HNSCC.

Translational Research and Plasma Proteomic in Cancer

Proteomics is a recent field of research in molecular biology that can help in the fight against cancer through the search for biomarkers that can detect this disease in the early stages of its development. Proteomic is a speedily growing technology, also thanks to the development of even more sensitive and fast mass spectrometry analysis. Although this technique is the most widespread for the discovery of new cancer biomarkers, it still suffers of a poor sensitivity and insufficient reproducibility, essentially due to the tumor heterogeneity. Common technical shortcomings include limitations in the sensitivity of detecting low abundant biomarkers and possible systematic biases in the observed data. Current research attempts are trying to develop high-resolution proteomic instrumentation for high-throughput monitoring of protein changes that occur in cancer. In this review, we describe the basic features of the proteomic tools which have proven to be useful in cancer research, showing their advantages and disadvantages. The application of these proteomic tools could provide early biomarkers detection in various cancer types and could improve the understanding the mechanisms of tumor growth and dissemination.

SLPI knockdown induced pancreatic ductal adenocarcinoma cells proliferation and invasion

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease and still continues to have the worst prognosis of all gastrointestinal malignancies. Reports have demonstrated that secretory leukocyte protease inhibitor (SLPI) is overexpressed in various cancers and may be a potential therapeutic strategy for the treatment of different cancers. However, the possible role of SLPI in PDAC is still unknown. In the present study, we investigate the effects of SLPI gene knockdown on the biological behavior of human pancreatic cancer cells. The expressions of SLPI were detected, by qRT-PCR and Western blot, in human PDAC tissues as well as AsPC-1, BxPC-3 and PANC-1 cells. After transfection with siRNA targeting to SLPI, SLPI expression was detected by qRT-PCR and Western blot in cells. Cell proliferation and apoptosis were also evaluated by MTT assay and flow cytometry (FCM). The trans-well assays were also employed to explore the effects of SLPI knockdown on the migration and invasion of PDAC cells in vitro.

RESULTS

The expressions of SLPI derived from human PDAC and PDAC cell lines were significant higher than those of control groups, respectively (P < 0.05). Regression analysis showed elevated SLPI level was positive correlated with development of PDAC. The siRNA target to SLPI significantly decreased the expressions of SLPI in these PDAC cell lines. Following SLPI-siRNA transduction, the proliferative capacity of the AsPC-1, BxPC-3 and PANC-1 cells was significantly inhibitions, compared to the blank (PDAC-wild type cells) and negative (non-targeting scrambled siRNA transduced PDAC cells) control ones, respectively (P < 0.05). Moreover, SLPI knockdown significantly increased the apoptosis fractions and reduced the migration and invasion of PDAC cells in vitro (P < 0.05).

CONCLUSIONS

The present study demonstrated that: i) SLPI played an important role in PDAC progression; ii) SLPI might be an important characteristic of malignant PDAC associated with migration and invasion in vitro; and iii) siRNA targeting to SLPI might be a potential therapeutic strategy for the treatment of PCC.

Potential biomarkers for oral squamous cell carcinoma: proteomics discovery and clinical validation

Oral squamous cell carcinoma (OSCC) is the worldwide concerned cancer. In spite of the advances in treatment, the 5-year survival rate has only increased subtly during the past two decades, which is largely due to the advanced stages of disease at diagnosis and the frequent development of relapse and second primary tumors. Therefore, the identification of underlying OSCC protein biomarker during cancer initiation and progression could aid the diagnosis and treatment of OSCC. In this review, recent researches on proteomics analysis of tissue, saliva, and serum for early detection and evaluation aggressiveness and occurrence of OSCC were summarized. The emphasis is placed on early detection by tissues, saliva, and serum of patients with histologically defined OSCC patients. Although lots of researches for searching OSCC protein biomarker have done, few common protein biomarkers have been detected. Low-redundant protein in tissues, saliva, and serum from OSCC may more accurately reflected the progression of OSCC, so novel approach for the depth research strategy and the sample choice for proteomics are of importance in OSCC biomarker discovery.