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Diverse proteomics-based strategies have been applied to saliva to quantitatively identify diagnostic and prognostic targets for oral cancer. Considering that these targets may be regulated by events that do not imply variation in protein abundance levels, we hypothesized that changes in protein conformation can be associated with diagnosis and prognosis, revealing biological processes and novel targets of clinical relevance. For this, we employed limited proteolysis-mass spectrometry in saliva samples to explore structural alterations, comparing the proteome of healthy control and oral squamous cell carcinoma (OSCC) patients with and without lymph node metastasis. Thirty-six proteins with potential structural rearrangements were associated with clinical patient features including transketolase and its interacting partners. Moreover, N -glycosylated peptides contribute to structural rearrangements of potential diagnostic and prognostic markers. Altogether, this approach utilizes saliva proteins to search for targets for diagnosing and prognosing oral cancer and can guide the discovery of potential regulated sites beyond protein-level abundance.

EEF1D (eukaryotic translation elongation factor 1δ) is a subunit of the elongation factor 1 complex of proteins that mediates the elongation process during protein synthesis via enzymatic delivery of aminoacyl-tRNAs to the ribosome. Although the functions of EEF1D in the translation process are recognized, EEF1D expression was found to be unbalanced in tumours. In the present study, we demonstrate the overexpression of EEF1D in OSCC (oral squamous cell carcinoma), and revealed that EEF1D and protein interaction partners promote the activation of cyclin D1 and vimentin proteins. EEF1D knockdown in OSCC reduced cell proliferation and induced EMT (epithelial-mesenchymal transition) phenotypes, including cell invasion. Taken together, these results define EEF1D as a critical inducer of OSCC proliferation and EMT., (© 2016 Authors; published by Portland Press Limited.)

Background: ADAM17 is one of the main sheddases of the cells and it is responsible for the cleavage and the release of ectodomains of important signaling molecules, such as EGFR ligands. Despite the known crosstalk between ADAM17 and EGFR, which has been considered a promising targeted therapy in oral squamous cell carcinoma (OSCC), the role of ADAM17 in OSCC development is not clear., Method: In this study the effect of overexpressing ADAM17 in cell migration, viability, adhesion and proliferation was comprehensively appraised in vitro. In addition, the tumor size, tumor proliferative activity, tumor collagenase activity and MS-based proteomics of tumor tissues have been evaluated by injecting tumorigenic squamous carcinoma cells (SCC-9) overexpressing ADAM17 in immunodeficient mice., Results: The proteomic analysis has effectively identified a total of 2,194 proteins in control and tumor tissues. Among these, 110 proteins have been down-regulated and 90 have been up-regulated in tumor tissues. Biological network analysis has uncovered that overexpression of ADAM17 regulates Erk pathway in OSCC and further indicates proteins regulated by the overexpression of ADAM17 in the respective pathway. These results are also supported by the evidences of higher viability, migration, adhesion and proliferation in SCC-9 or A431 cells in vitro along with the increase of tumor size and proliferative activity and higher tissue collagenase activity as an outcome of ADAM17 overexpression., Conclusion: These findings contribute to understand the role of ADAM17 in oral cancer development and as a potential therapeutic target in oral cancer. In addition, our study also provides the basis for the development of novel and refined OSCC-targeting approaches.

Unlabelled: Oral cancer disease represents a significant fraction of all human cancer types and its poor early diagnosis contributes to reduced individual survival rate. The identification of proteins modulated in tumorigenic cells and its post-translational modifications may improve our understanding of tumor development in epithelial cells. We have analyzed the phosphoproteome of tumorigenic (SCC-9) and non-tumorigenic (HaCaT) cell lines using MS-based approach in order to identify phosphopeptides with differing patterns of modifications and/or abundance. Our results revealed the identity of 4,206 protein phosphorylation sites with sixty-two sites showing to be significantly modulated between the two cell lines. The phosphoproteome data showed an overrepresentation of proteins with a possible role in nuclear regulatory functions. Pathway analysis was further performed on the phosphoproteome dataset and differences and commonalities of the functional pathways present in tumorigenic and non-tumorigenic cells were identified. Phosphopeptides that belong to the proteins lamina-associated polypeptide 2 isoform alpha and serine-arginine repetitive matrix protein 2 were identified with differential abundance and they appear as promising tumor-related phosphopeptides. These two proteins may be related to the structural alterations generally found in the nucleus of tumorigenic cells. The identification of phosphorylation sites in tumorigenic cells may contribute to disclose novel signaling mechanisms associated with OSCC., Significance: Oral Squamous Cell Carcinoma (OSCC) is an important cancer disease affecting thousands of people worldwide. Many cellular processes related to the development of oral cancer remain unknown; however, the studies performed in vitro with cancer cells have contributed to guide more specific research which may be further performed by using in vivo approaches or clinical samples. To our knowledge, only few studies have been published showing the results of phosphoproteome profiling of squamous cell carcinoma models, and many signaling proteins must be identified and functionally characterized in order to increase the knowledge available about the complexity of the signaling networks responsible for oral cancer development and its progression. Furthermore, our knowledge regarding proteins exclusive or very low abundant in cancer cells remains limited. A better understanding of the differences between signaling pathways present in epithelial cell lines may contribute to reveal the processes underlying the OSCC., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Saliva is a biofluid that maintains the health of oral tissues and the homeostasis of oral microbiota. Studies have demonstrated that Oral squamous cell carcinoma (OSCC) patients have different salivary microbiota than healthy individuals. However, the relationship between these microbial differences and clinicopathological outcomes is still far from conclusive. Herein, we investigate the capability of using metagenomic and metaproteomic saliva profiles to distinguish between Control (C), OSCC without active lesion (L0), and OSCC with active lesion (L1) patients. The results show that there are significantly distinct taxonomies and functional changes in L1 patients compared to C and L0 patients, suggesting compositional modulation of the oral microbiome, as the relative abundances of Centipeda, Veillonella , and Gemella suggested by metagenomics are correlated with tumor size, clinical stage, and active lesion. Metagenomics results also demonstrated that poor overall patient survival is associated with a higher relative abundance of Stenophotromonas , Staphylococcus , Centipeda , Selenomonas , Alloscordovia , and Acitenobacter. Finally, compositional and functional differences in the saliva content by metaproteomics analysis can distinguish healthy individuals from OSCC patients. In summary, our study suggests that oral microbiota and their protein abundance have potential diagnosis and prognosis value for oral cancer patients. Further studies are necessary to understand the role of uniquely detected metaproteins in the microbiota of healthy and OSCC patients as well as the crosstalk between saliva host proteins and the oral microbiome present in OSCC. • Saliva metagenomics and metaproteomics analysis are promising meta-omics approach. • Saliva microbiome and their microbiota proteins distinguished C, L0, and L1 groups. • Proteins were modulated in OSCC and may be related to microbiota compositional and functional changes. • Oral microbiota and its proteins show potential use in prognosis of OSCC patients. [ABSTRACT FROM AUTHOR]