Global Quantitative Proteomics reveal Deregulation of Cytoskeletal and Apoptotic Signalling Proteins in Oral Tongue Squamous Cell Carcinoma

The 'omics of obesity in B-cell acute lymphoblastic leukemia

The obesity pandemic currently affects more than 70 million Americans and more than 650 million individuals worldwide. In addition to increasing susceptibility to pathogenic infections (eg, SARS-CoV-2), obesity promotes the development of many cancer subtypes and increases mortality rates in most cases. We and others have demonstrated that, in the context of B-cell acute lymphoblastic leukemia (B-ALL), adipocytes promote multidrug chemoresistance. Furthermore, others have demonstrated that B-ALL cells exposed to the adipocyte secretome alter their metabolic states to circumvent chemotherapy-mediated cytotoxicity. To better understand how adipocytes impact the function of human B-ALL cells, we used a multi-omic RNA-sequencing (single-cell and bulk transcriptomic) and mass spectroscopy (metabolomic and proteomic) approaches to define adipocyte-induced changes in normal and malignant B cells. These analyses revealed that the adipocyte secretome directly modulates programs in human B-ALL cells associated with metabolism, protection from oxidative stress, increased survival, B-cell development, and drivers of chemoresistance. Single-cell RNA sequencing analysis of mice on low- and high-fat diets revealed that obesity suppresses an immunologically active B-cell subpopulation and that the loss of this transcriptomic signature in patients with B-ALL is associated with poor survival outcomes. Analyses of sera and plasma samples from healthy donors and those with B-ALL revealed that obesity is associated with higher circulating levels of immunoglobulin-associated proteins, which support observations in obese mice of altered immunological homeostasis. In all, our multi-omics approach increases our understanding of pathways that may promote chemoresistance in human B-ALL and highlight a novel B-cell-specific signature in patients associated with survival outcomes.

Evaluation of the Anti-Carcinogenic Effect of Centella Asiatica on Oral Cancer Cell Line: In vitro Study

OBJECTIVE

To evaluate the anti-carcinogenic effect of Centella Asiatica on to evaluate the  Anti-Carcinogenic Effect of Centella Asiatica on Oral Cancer Cell Line oral cancer cell line.

MATERIALS AND METHODS

 Oral Cancer cell line and normal oral keratinocyte cell line were procured.Centella asiatica extract was prepared. The cells were then subjected to the test herbal specimens -Centella asiatica extract in succeeding concentrations of 25 µg/ml, 50 µg/ml, 100 µg/ml at time intervals of 24,48 and 72 hours. Cisplatin (2 µg/ml, 4 µg/ml, 6 µg/ml, 8 µg/ml) was used as a positive control. This experiment was done in triplets.

RESULTS

The study revealed that the p values were less than 0.05 at concentration 12.5µg/ml, 25µg/ml, 50 µg/ml,100 µg/ml and time period of 24hrs,48hrs,72hrs, thus implying that at these concentrations and time period, the obtained data were statistically significant, thus indicating that there is a statistically significantly decreases in the viable cells as the concentration of the drug as a time period increases The results reveals that  centella asiatica possess potential effect of anti-carcinogenic, effect when compared to positive control (Cisplatin).

CONCLUSION

The current study reveals that Centella asiatica has an potential anti-carcinogenic effect on oral cancer cell line. So this can be used to treat oral cancer with minimal crippling as compared with allopathic drugs.

Quantitative Proteomic Analysis of Non-Tobacco Associated Oral Squamous Cell Carcinoma Reveals Deregulation of Cytoskeletal and Apoptotic Proteins

BACKGROUND

The exact etiology of non-tobacco associated oral squamous cell carcinoma (NT-OSCC) is still unknown. The lack of established biomarkers for oral NT-OSCC has resulted in less effective management and poor prognosis. Here, we report for the first time a panel of potential markers identified from the quantitative proteomic analysis of NT-OSCC using two-dimensional gel-electrophoresis (2D-GE) using matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF) coupled with mass spectrometry (MS) and further analysis using protein analysis through evolutionary relationships (PANTHER) database.

OBJECTIVE

To quantitatively analyze the proteomic profile of non-tobacco associated oral squamous cell carcinoma.

METHODS

Twenty fresh tissue samples were collected from healthy controls and NT-OSCC, ten each, and were subjected to proteomic analysis. Sample quantification for the presence of protein was done using Bradford assay and bovine serum albumin was used as a standard protein to obtain the standard graph. Fractionation of protein was done using sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) and they were separated based on their molecular weight. MS analysis was done and the purified peptides were analysed using MALDI-TOF. PANTHER database for functional classification and pathway analysis was done for identification of protein expression.

RESULTS

Our approach of combining 2D-GE with MS identified four candidate proteins including keratin, alpha-1-antitrypsin (AAT), S100 and serpin B5 with significant differential expression in NT-OSCC as compared with healthy controls. The results showed that the levels of these proteins were significantly upregulated in NT-OSCC when compared to the healthy controls that suggests that these proteins can be used as candidate targets for NT-OSCC therapeutics.

CONCLUSION

The differentially expressed proteins are found to be involved in apoptotic signalling pathways, cytoskeletal dynamics and are known to play a critical role in oral tumorigenesis. Put together, the results provide available baseline information for understanding the development and progression of NT-OSCC. These identified proteins on further validation may be used as potential biomarkers in future for early detection and predicting therapeutic outcome of patients with NT-OSCC.

Investigating the Function of Human Jumping Translocation Breakpoint Protein (hJTB) and Its Interacting Partners through In-Solution Proteomics of MCF7 Cells

Human jumping translocation breakpoint (hJTB) gene is located on chromosome 1q21 and is involved in unbalanced translocation in many types of cancer. JTB protein is ubiquitously present in normal cells but it is found to be overexpressed or downregulated in various types of cancer cells, where this protein and its isoforms promote mitochondrial dysfunction, resistance to apoptosis, genomic instability, proliferation, invasion and metastasis. Hence, JTB could be a tumor biomarker for different types of cancer, such as breast cancer (BC), and could be used as a drug target for therapy. However, the functions of the protein or the pathways through which it increases cell proliferation and invasiveness of cancer cells are not well-known. Therefore, we aim to investigate the functions of JTB by using in-solution digestion-based cellular proteomics of control and upregulated and downregulated JTB protein in MCF7 breast cancer cell line, taking account that in-solution digestion-based proteomics experiments are complementary to the initial in-gel based ones. Proteomics analysis allows investigation of protein dysregulation patterns that indicate the function of the protein and its interacting partners, as well as the pathways and biological processes through which it functions. We concluded that JTB dysregulation increases the epithelial-mesenchymal transition (EMT) potential and cell proliferation, harnessing cytoskeleton organization, apical junctional complex, metabolic reprogramming, and cellular proteostasis. Deregulated JTB expression was found to be associated with several proteins involved in mitochondrial organization and function, oxidative stress (OS), apoptosis, and interferon alpha and gamma signaling. Consistent and complementary to our previous results emerged by using in-gel based proteomics of transfected MCF7 cells, JTB-related proteins that are overexpressed in this experiment suggest the development of a more aggressive phenotype and behavior for this luminal type A non-invasive/poor-invasive human BC cell line that does not usually migrate or invade compared with the highly metastatic MDA-MB-231 cells. This more aggressive phenotype of MCF7 cells related to JTB dysregulation and detected by both in-gel and in-solution proteomics could be promoted by synergistic upregulation of EMT, Mitotic spindle and Fatty acid metabolism pathways. However, in both JTB dysregulated conditions, several downregulated JTB-interacting proteins predominantly sustain antitumor activities, attenuating some of the aggressive phenotypical and behavioral traits promoted by the overexpressed JTB-related partners.

2D-DIGE-Based Proteomic Profiling with Validations Identifies Vimentin as a Secretory Biomarker Useful for Early Detection and Poor Prognosis in Oral Cancers

Oral tongue squamous cell carcinoma (OTSCC) is an aggressive cancer with high morbidity and mortality rates, despite multimodality management. There are currently no clinically relevant molecular markers that identify patients at higher risk of recurrence and failure. We undertook 2D-DIGE proteomic profiling to study the differentially expressed proteins in OTSCC evaluating their role in prognosis. 2D-DIGE coupled with tandem mass spectrometry was performed on tissues obtained from early staged OTSCC along with its paired apparently adjacent normal tissue samples (n = 10). Top upregulated protein was validated using immunohistochemistry (n = 345), comprising of retrospective early stage OTSCC (n = 150) and prospective series of oral precancers, normal, and oral cancers (n = 195). Saliva samples collected from oral cancer and precancer samples were analyzed by ELISA (n = 146). We found statistically significant differential expression in 151 proteins out of 700 proteins quantified. Top ten differentially regulated proteins were identified using mass spectrometry analysis. We found vimentin, the mesenchymal protein, to be the most upregulated protein in tongue tumor tissues compared to adjacent apparent normal tissues. Vimentin was found to be significantly overexpressed in oral precancers along with cancers compared to normal tissues. The vimentin expression correlated significantly with differentiated states of oral precancers and cancers. Vimentin was also detected at significantly higher levels in saliva collected from oral precancer and cancer patients compared to normal healthy volunteers. Validation of vimentin in an independent series of retrospective early staged OTSCC showed that the vimentin expression is significantly associated with treatment failures and poorer DFS. The vimentin expression is useful as both poor prognostic and early detection marker in oral cancer. Vimentin detection in saliva can be a diagnostic test to detect oral precancers that may have malignant potential, needing closer follow-up, and disease monitoring.

Integrated Proteomics Based on 2D Gel Electrophoresis and Mass Spectrometry with Validations: Identification of a Biomarker Compendium for Oral Submucous Fibrosis—An Indian Study

Oral Submucous Fibrosis (OSMF) is a chronic debilitating disease more frequently found in the South East Asian population. This disease poses a public health priority, as it is grouped under oral potentially malignant disorders, with malignant transformation rates of around 7 to 13%. Hence, early identification of high-risk OSMF patients is of the utmost importance to prevent malignant transformation. Proteomic expression profiling is a promising method for identifying differentially expressed proteins for disease prognosis and risk stratification in OSMF. In this study, overexpressed proteins in OSMF, OSMF transformed into oral squamous cell carcinoma (OSCC) and normal tissues were evaluated by proteomic analysis using two-dimensional electrophoresis (2DE) and mass spectrometry, which revealed 23 upregulated proteins. Validation was done using immunohistochemistry for three secretory proteins, namely 14-3-3ε (n = 130), carbonic anhydrase 1 (CA 1) (n = 125) and heat shock protein 70 (HSP 70) (n = 117), which showed significant overexpression in OSMF, OSCC compared to normal. The present study is the first of its kind in India to the best of our knowledge, assessing the altered expression of proteins in OSMF and OSMF which has undergone malignant transformation, obtaining a better knowledge of the molecular pathways involved in the disease progression. The current study shows that the biomarkers studied can be potentially useful for risk stratification of OSMF to OSCC serving as novel targets for therapeutic intervention. Clinical validation of the targets can further pave way for precision medicine to improve the quality of life in OSMF patients.

Label-free quantitation of the changes in salivary proteome associated with the chronic consumption of the betel nut (Areca catechu)

Areca nut or betel nut chewing is most frequently used in Pakistan and is associated with a high risk for oral cancer. Until now, however, there has not been any research conducted on the long-term effect(s) of betel nut chewing on the saliva proteome. In the present study, initially, the changes in the saliva proteome associated with betel nut chewing were investigated. Secondly, the analysis was focused on the changes in salivary proteome with respect to prolonged usage of betel nuts. After extraction, the saliva proteins were digested into peptides and these were subsequently analyzed using mass spectrometry. Data are available via ProteomeXchange with identifier PXD029768. Label-free quantitation of saliva samples revealed a total of 12 proteins that were differentially expressed between betel nut addicts (BNAs), and the control group. The study groups were further divided into three subgroups, the BNA-1, BNA-2, and BNA-3 groups, with respect to the extent of consumption of betel nuts in terms of years. The data analysis revealed a more detailed profiling of proteins expressed after five, ten, and more than ten years of betel nut consumption. A total of 30, 17, and 22 proteins were found to be differentially expressed when divided into the BNA-1, BNA-2, and BNA-3 groups. The present study shows that the chronic usage of betel nuts leads to the expression of proteins, such as SPARC1, profilin, and SBSN, which are known to be involved in head and neck cancers.

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.

Molecular basis for RASSF10/NPM/RNF2 feedback cascade-mediated regulation of gastric cancer cell proliferation

Ras-association domain family (RASSF) proteins are encoded by numerous tumor suppressor genes that frequently become silenced in human cancers. RASSF10 is downregulated by promoter hypermethylation in cancers and has been shown to inhibit cell proliferation; however, the molecular mechanism(s) remains poorly understood. Here, we demonstrate for the first time that RASSF10 inhibits Cdk1/cyclin-B kinase complex formation to maintain stable levels of cyclin-B for inducing mitotic arrest during cell cycle. Using LC-MS/MS, live cell imaging, and biochemical approaches, we identify Nucleophosmin (NPM) as a novel functional target of RASSF10 and revealed that RASSF10 expression promoted the nuclear accumulation of GADD45a and knockdown of either NPM or GADD45a, resulting in impairment of RASSF10-mediated G2/M phase arrest. Furthermore, we demonstrate that RASSF10 is a substrate for the E3 ligase ring finger protein 2 (RNF2) and show that an NPM-dependent downregulation of RNF2 expression is critical to maintain stable RASSF10 levels in cells for efficient mitotic arrest. Interestingly, the Kaplan-Meier plot analysis shows a positive correlation of RASSF10 and NPM expression with greater gastric cancer patient survival and the reverse with expression of RNF2, suggesting that they may have a role in cancer progression. Finally, our findings provide insights into the mode of action of the RASSF10/NPM/RNF2 signaling cascade on controlling cell proliferation and may represent a novel therapeutic avenue for the prevention of gastric cancer metastasis.

Comparative Proteomic Analysis Reveals Novel Biomarkers for Gastric Cancer in South Indian Tamil Population

BACKGROUND

Gastric cancer (GC) remains a major global health problem due to a poor understanding of its progression at the molecular level and a lack of early detection or diagnosis. Early detection is highly crucial for improving prognosis. The incidence of GC is very high in countries like India due to the limitations among the established biomarkers for GC owing to poor sensitivity and specificity.

OBJECTIVE

To identify the novel biomarkers from serum samples obtained from GC patients when compared with healthy subjects.

METHODS

Serum samples from GC patients were analyzed by two-dimensional gel electrophoresis (2DGE) coupled with tandem mass spectrometry (MS), including both matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) and liquid chromatography-MS (LC-MS/MS) analysis. Identified proteins were further analyzed by gene ontology and protein interaction studies.

RESULTS

A total of 73 protein spots were detected in 2DGE image analysis. Among them, seven differentially-expressed proteins were identified using MS analyses, which included serotransferrin/transferrin, albumin, ceruloplasmin, C-reactive protein (CRP), fibrinogen γ-chain (FGG), and two unreported novel proteins, immunoglobulin kappa constant (IgκC) region and Homo sapiens zinc finger protein 28 (ZNF28) homolog. Among these proteins, serotransferrin, albumin, ceruloplasmin, FGG, and ZNF28 were down-regulated in GC samples (p < 0.05), while IgκC region and CRP were up-regulated significantly.

CONCLUSION

Most of the differentially expressed proteins were involved in angiogenesis, plasminogen-activating cascade, and blood coagulation pathways which are known to play a critical role in gastric tumorigenesis. Our current results provide a panel of candidate biomarkers for GC with novel biomarkers which were not reported earlier.

Long Intergenic Non-Protein Coding RNA 519 Promotes the Biological Activities of Tongue Squamous Cell Carcinoma by Sponging microRNA-876-3p and Consequently Upregulating MACC1

Purpose

Long intergenic non-protein coding RNA 519 (LINC00519) promotes the development of lung squamous cell carcinoma. In this study, we detected the expression of LINC00519 in tongue squamous cell carcinoma (TSCC) and examined its clinical significance. Additionally, the regulatory effects of LINC00519 on behaviors of TSCC tumor cells were explored through functional experiments. Finally, mechanistic studies were performed to elucidate the molecular events underlying the tumor-promoting actions of LINC00519 in TSCC.

Materials and Methods

The expression of LINC00519 in TSCC tissues and cell lines was determined using quantitative reverse transcription-polymerase chain reaction. Cell counting kit-8 assay, flow cytometric analysis, cell migration and invasion assays and xenograft tumor model analyses were used to detect TSCC cell proliferation, apoptosis, migration and invasion and in vivo tumor growth, respectively. Mechanistic studies were performed using bioinformatics analysis, RNA immunoprecipitation assay, luciferase reporter assay and rescue experiments.

Results

LINC00519 was overexpressed in both TSCC tissues and cell lines. A high LINC00519 level was associated with poor overall survival in patients with TSCC. In vitro, LINC00519 played cancer-promoting roles in TSCC progression by facilitating cell proliferation, migration and invasion and restraining cell apoptosis. In vivo, LINC00519 downregulation resulted in decreased TSCC tumor growth. Mechanistically, LINC00519 acted as a competing endogenous RNA for microRNA-876-3p (miR-876-3p), which directly targets metastasis associated with colon cancer-1 (MACC1), in TSCC cells. LINC00519 upregulated the expression of MACC1 in TSCC cells by sequestering miR-876-3p. Rescue experiments further affirmed that miR-876-3p inhibition or MACC1 overexpression mitigated the inhibitory influences of LINC00519 depletion on cell proliferation, migration and invasion and neutralized the promoting actions of LINC00519 knockdown on cell apoptosis in TSCC.

Conclusion

LINC00519 aggravated the oncogenicity of TSCC by regulating the miR-876-3p/MACC1 axis. Our findings suggest that the LINC00519/miR-876-3p/MACC1 pathway may be an underlying therapeutic target in TSCC.

The development and clinical applications of proteomics: an Indian perspective

INTRODUCTION

Proteomic research has been extensively used to identify potential biomarkers or targets for various diseases. Advances in mass spectrometry along with data analytics have led proteomics to become a powerful tool for exploring the critical molecular players associated with diseases, thereby, playing a significant role in the development of proteomic applications for the clinic.

AREAS COVERED

This review presents recent advances in the development and clinical applications of proteomics in India toward understanding various diseases including cancer, metabolic diseases, and reproductive diseases. Keywords combined with 'clinical proteomics in India' 'proteomic research in India' and 'mass spectrometry' were used to search PubMed.

EXPERT OPINION

The past decade has seen a significant increase in research in clinical proteomics in India. This approach has resulted in the development of proteomics-based marker technologies for disease management in the country. The majority of these investigations are still in the discovery phase and efforts have to be made to address the intended clinical use so that the identified potential biomarkers reach the clinic. To move toward this necessity, there is a pressing need to establish some key infrastructure requirements and meaningful collaborations between the clinicians and scientists which will enable more effective solutions to address health issues specific to India.

LncRNA CASC9 Affects Cell Proliferation, Migration, and Invasion of Tongue Squamous cell Carcinoma via Regulating miR-423-5p/SOX12 Axes

Introduction

The incidence of tongue squamous cell carcinoma (TSCC) has increased in recent decades. However, the function of long non-coding RNA (lncRNA) CASC9 in the occurrence and progression of TSCC is unclear. In this work, we attempted to clarify the role of lncRNA CASC9 in determining the phenotype of TSCC cells, and to clarify the underlying mechanisms.

Methods

We used qRT-PCR analysis to identify the level of CASC9 mRNA expression in TSCC clinical samples and cell lines. We investigated cell proliferation, and cell migration and invasion of TSCC cells transfected with siCASC9 or siNC using CCK-8 and transwell assays. Bioinformatics analysis and a luciferase reporter assay were employed to predict and verify the target microRNA (miRNA).

Results

CASC9 was up-regulated in the TSCC tissues and cells, and predicted a poor prognosis. CASC9 silencing significantly inhibited cell proliferation, migration, and invasion of the TSCC cells compared with the non-targeting control small interfering RNA (siCtrl) treatment. miR-423-5p was predicted as the targeting miRNA of CASC9; this was verified by a luciferase reporter assay. CASC9 expression showed a negative correlation with miR-423-5p expression and a positive correlation with SOX12 expression. The miR-423-5p inhibitor can rescue the carcinogenesis effect of CASC9 on TSCC cells.

Conclusion

Our work indicates that CASC9 plays a role in TSCC tumorigenesis; this novel information will improve TSCC molecular targeting therapy.

Cooperative Effects of Cytosine Methylation on DNA Structure and Dynamics

The behavior of the structural parameters of DNA considering different levels of methylation in CpG islands is studied by means of full-atom molecular dynamics simulations and electronic circular dichroism, both in an artificial model system and in a gene promoter sequence. It is demonstrated that methylation although intrinsically brings quite local perturbations may, if its level is high enough, induce cooperative effects that strongly modify the DNA backbone torsional parameters altering the helicity as compared to the nonmethylated case. Because methylation of the CpG island is correlated with the regulation of gene expression, understanding the structural modifications induced in DNA is crucial to characterize all the fine equilibria into play in epigenetics phenomena.

MiR-940 inhibits migration and invasion of tongue squamous cell carcinoma via regulatingCXCR2/NF-κB system-mediated epithelial-mesenchymal transition

Tongue squamous cell carcinoma (TSCC) is one of the most common incident oral cancers, which is accompanied by high rate of metastasis and recurrence. It has been demonstrated that elevated interleukin-8 (IL-8) promoted metastasis of various cancers via regulating epithelial-mesenchymal transition (EMT) process, whereas the accurate mechanism is left to be elucidated. The present work was aimed to investigate the role of microRNA-940 (miR-940)/C-X-C chemokine receptor type 2 (CXCR2) system in the metastasis ability and EMT process of IL-8-treated TSCC cells and further explore the underlying mechanisms. We found that miR-940 up-regulation inhibited IL-8-induced migration and invasion, which could be deprived by CXCR2 silence. We also observed that miR-940 suppressed epithelial marker E-cadherin expression while increased mesenchymal markers N-cadherin and Twist levels in IL-8-stimulated TSCC cells. Besides, IL-8-induced invasion and EMT process of TSCC cells were impeded in the present of the NF-κB inhibitor, PDTC or BAY117082. In conclusion, our data demonstrated that miR-940/CXCR2 system regulated the metastasis of TSCC cells via NF-κB-induced EMT process.

Middle-down approach: a choice to sequence and characterize proteins/proteomes by mass spectrometry

Owing to rapid growth in the elucidation of genome sequences of various organisms, deducing proteome sequences has become imperative, in order to have an improved understanding of biological processes. Since the traditional Edman method was unsuitable for high-throughput sequencing and also for N-terminus modified proteins, mass spectrometry (MS) based methods, mainly based on soft ionization modes: electrospray ionization and matrix-assisted laser desorption/ionization, began to gain significance. MS based methods were adaptable for high-throughput studies and applicable for sequencing N-terminus blocked proteins/peptides too. Consequently, over the last decade a new discipline called 'proteomics' has emerged, which encompasses the attributes necessary for high-throughput identification of proteins. 'Proteomics' may also be regarded as an offshoot of the classic field, 'biochemistry'. Many protein sequencing and proteomic investigations were successfully accomplished through MS dependent sequence elucidation of 'short proteolytic peptides (typically: 7-20 amino acid residues), which is called the 'shotgun' or 'bottom-up (BU)' approach. While the BU approach continues as a workhorse for proteomics/protein sequencing, attempts to sequence intact proteins without proteolysis, called the 'top-down (TD)' approach started, due to ambiguities in the BU approach, e.g., protein inference problem, identification of proteoforms and the discovery of posttranslational modifications (PTMs). The high-throughput TD approach (TD proteomics) is yet in its infancy. Nevertheless, TD characterization of purified intact proteins has been useful for detecting PTMs. With the hope to overcome the pitfalls of BU and TD strategies, another concept called the 'middle-down (MD)' approach was put forward. Similar to BU, the MD approach also involves proteolysis, but in a restricted manner, to produce 'longer' proteolytic peptides than the ones usually obtained in BU studies, thereby providing better sequence coverage. In this regard, special proteases (OmpT, Sap9, IdeS) have been used, which can cleave proteins to produce longer proteolytic peptides. By reviewing ample evidences currently existing in the literature that is predominantly on PTM characterization of histones and antibodies, herein we highlight salient features of the MD approach. Consequently, we are inclined to claim that the MD concept might have widespread applications in future for various research areas, such as clinical, biopharmaceuticals (including PTM analysis) and even for general/routine characterization of proteins including therapeutic proteins, but not just limited to analysis of histones or antibodies.

Label-free tissue proteomics can classify oral squamous cell carcinoma from healthy tissue in a stage-specific manner

OBJECTIVES

No prognostic or predictive biomarkers for oral squamous cell carcinoma (OSCC) exist. We aimed to discover novel proteins, altered in OSCC, to be further investigated as potential biomarkers, and to improve understanding about pathways involved in OSCC.

MATERIALS AND METHODS

Proteomic signatures of seven paired healthy and OSCC tissue samples were identified using ultra-definition quantitative mass spectrometry, then analysed and compared using Anova, principal component analysis, hierarchical clustering and OPLS-DA modelling. A selection of significant proteins that were also altered in the serum from a previous study (PMID: 28632724) were validated immunohistochemically on an independent cohort (n = 66) to confirm immunopositivity and location within tumour tissue. Ingenuity Pathways Analysis was employed to identify altered pathways.

RESULTS

Of 829 proteins quantified, 257 were significant and 72 were able to classify healthy vs OSCC using OPLS-DA modelling. We identified 19 proteins not previously known to be upregulated in OSCC, including prosaposin and alpha-taxilin. KIAA1217 and NDRG1 were upregulated in stage IVa compared with stage I tumours. Altered pathways included calcium signalling, cellular movement, haematological system development and function, and immune cell trafficking, and involved NF-kB and MAPK networks.

CONCLUSIONS

We found a set of proteins reliably separating OSCC tumour from healthy tissue, and multiple proteins differing between stage I and stage IVa OSCC. These potential biomarkers can be studied and validated in larger cohorts.