Table 1.
Biomarkers of saliva for cancer diagnosis.
| Identified Salivary Biomarkers | Proteomic Tools | Inference | References |
|---|---|---|---|
| Glutathione | HPLC | Epidemiological marker to identify subjects with an increased risk of developing oral squamous cell carcinoma (OSCC) to submit strict follow up and chemoprevention. | [25] |
| Interleukin 1a (IL-1a), Interleukin 1b (IL-1b), Interleukin-6(IL-6), Interleukin-8(IL-8), TNF-a | ELISA | These pro-angiogenic, pro-inflammatory cytokines were found to be elevated in the whole saliva of oral cancer patients and oral pre-cancers as compared to controls, which suggested its utility as surrogate indicators of carcinogenic transformation from oral pre-cancer to oral cancer. | [26,27,28] |
| CD44 | Immunoblot | CD44 is elevated in the majority of head and neck squamous cell carcinoma (HNSCC) and distinguishes cancer from benign diseases with high specificity; these markers will detect HNSCC with very high sensitivity and specificity. | [19] |
| CD59 | Immunoblot | Non-invasive method for the diagnosis of oral cancer. | [15] |
| Immunoglobulin heavy chain constant region gamma (IgG) | LC/MS | Significantly altered in OSCC patients as compared with healthy controls; they are inhibitors of apoptosis. | [21] |
| Mac-2 binding protein (M2BP) | ELISA | Provide a sensitivity of 90% and a specificity of 83% for OSCC detection. | [15] |
| MRP14 | Immunoblotting | MRP14 is a calcium-binding protein that has been implicated in different types of human cancers. Provides a sensitivity of 90% and a specificity of 83% for OSCC detection. | [15] |
| p53 antibodies | ELISA | Presence of p53 autoantibodies in saliva, as well as serum of oral cancer patients demonstrated that its detection in saliva can offer a non-invasive method for the detection of a subset of tumors with p53 aberrations. | [29,30] |
| Profilin | Immunoblot | The data proved that these new targets may lead to a simple clinical tool for the non-invasive diagnosis of oral cancer and suggested that patient-based salivary proteomics is a promising approach to the discovery of biomarkers for oral cancer detection. | [15] |
| S100 calcium binding protein | LC/MS | S100A2, an 11.4 kDa protein, is a member of the S100 family of calcium-binding proteins that have diverse functions, regulating a variety of cellular processes such as differentiation, regeneration, cell growth, and signal transduction in neoplastic cells and is a prognostic marker for oral cancer patients. | [21,31] |
| Endothelin-1 | Quantitative real time RT-PCR | Salivary ET-1is a good biomarker for OSCC development in oral lichen planus (OLP) patients regardless of the degree of OLP disease activity. However, it appeared not to be a good biomarker for detecting recurrence of OSCC in patients in remission. | [22,32] |
| Cofilin-1 | LC/MS | These proteins are involved in tumour progression, metastasis and angiogenesis. | [21] |
| Albumin | MALDI-MS | Serum albumin levels decreased in oral pre-malignancy and oral malignancy cases compared to healthy individuals. Salivary albumin levels increased in oral pre-malignancy and oral malignancy cases compared to healthy individuals, suggesting that albumin may play a role in the early diagnosis and prognosis of oral pre-malignant and oral malignant tissues. | [33,34] |
| Telomerase | PCR and ELISA | Telomerase is required for the maintenance of telomere length during chromosome replication; telomerase activity has been detected in tumor cells. | [35] |
| Tissue polypeptide antigen (TPA), Cyfra 21-1, Cancer antigen 125 (CA-125) | ELISA, TRFIA, Immuno-radiometric assay | Significant increases in salivary concentrations of Cyfra 21-1, CA-125 and tissue polypeptide antigen markers revealed sensitivity, specificity, and it is used as a diagnostic tool, especially when a concurrent analysis for significantly increased markers is done. | [20,36,37] |
| Transferrin | LC/MS | Salivary transferrin levels in patients are strongly correlated with the size and stage of the tumor. | [21,38] |
| Fibrin | LC/MS | Similarly, the use of the fibrin SCC biomarker is limited by its non-specificity, even though it is involved with various carcinogenic processes. | [21,39] |
| α-Amylase | MALDI-MS | α-amylase (57 kDa) dominated the high mass range in the MALDI mass spectra of the saliva from healthy subjects, but the peak was suppressed for patients with oral cancer. SDS-PAGE results show that concentrations of alpha-amylase in patients' saliva were significantly higher than those in healthy subjects. MALDI-MS thus has potential as a possible rapid diagnostic screening tool for oral cancer. | [40] |
| Salivary zinc finger, Protein 510 peptide | MALDI-TOF MS Technology | ZNF510 peptides, as OSCC-related salivary biomarkers via the proteomic approach, proved useful in adjunct diagnosis for early detection rather than as a specific diagnosis marker for progression of OSCC patients. | [41] |
| Keratin 36, cystatin A. | MS-based proteomics | Keratin overexpression in OSCC cells may have important molecular functions as structural constituents of the cytoskeleton as well as implications on cell shape and cell size. A 14 kDa protein detected in pre-treatment saliva from the OSCC patients was identified as a truncated cystatin SA-I, with deletion of three amino acids from the N-terminus, proposing that Protein-Chip analysis may provide a reliable screening test and cystatin SA-I might be a useful tumor biomarker for OSCC. | [42,43] |
| Truncated cystatin SA-I | Anion exchange (Q10), cation-exchange (CM10), reversed phase (H50), and immobilized affinity capture (IMAC3) Protein-Chip array | A 14 kDa protein detected in pre-treatment saliva from the OSCC patients was identified as a truncated cystatin SA-I, with deletion of three amino acids from the N-terminus. Truncated cystatin SA-I is a useful tumor biomarker for OSCC. | [43] |
| Myosin, actin, S100A7, keratin-19 and catalase | iTRAQ labeling and Mass spectrometric analysis, Immunoblot |
Actin and myosin are promising salivary biomarkers for distinguishing premalignant and malignant oral lesions. It is highly beneficial and noninvasive, being an effective alternative to serum testing, and it provides the possibility of developing self-, home-testing kits for such markers, further facilitating it as a diagnostic aid. | [44,45] |
| Signal transducer and activator of transcription 3(STAT3), Serpin B3 (SCCA1) | (1) preparative IEF using free flow electrophoresis (FFE), (2) SCX chromatography, and (3) LC on line with ESI-MS/MS |
Transcription factor that binds to the interleukin-6-responsive elements, may act as a protease inhibitor to modulate the host immune response against tumor cells. | [12] |
| α-1-antitrypsin (AAT), haptoglobin (HAP) | 2DE and MS | The patients' saliva α1-antitrypsin (AAT) and haptoglobin (HAP) β-chains were resolved into polypeptide spots with increased micro heterogeneity. A strong association of AAT and HAP with OSCC was further supported by immunohistochemical staining of cancer tissues. | [46] |
| Thioredoxin | MALDI–MS and LC-MS/MS | Saliva thioredoxin mRNA level was concordantly up-regulated in OSCC subjects. In addition, thioredoxin was found over-expressed in human cancers such as non-small cell lung, gastric, cervical and hepatocellular carcinomas. | [47] |
| KNG1, ANA2, and HSPA5 | Multiple reaction monitoring-MS | Four-protein panel offers a clinically effective tool for detecting OSCC and monitoring high-risk oral premalignant diseases (OPMDs). | [48] |
| Tobacco specific nitrosamines (TSNAs), N'-nitrosonornicotine (NNN) | A simple method with an alkaline single liquid–liquid extraction with dichloromethane/isopropanol was used for quantification. | Biomarker of cancer risk associated with exposure to tobacco smoke. | [49] |
| AAT and HAP | Two-Dimensional Electrophoresis, Mass spectrometry | Panel of proteins is useful for the prediction of aggressive phenotypes in OSCC; and the distinctive expression of proteins and tumor size parameter shows the aggression of cancer. | [50] |
| Secretory leukocyte peptidase inhibitor, keratin 36, cystatin A. | Mass spectrometry | Non-invasive biomarker of oral cancer progression with potential in preventive treatment. | [51] |
High performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), liquid chromatograph/mass spectrometer (LC/MS), matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), polymerase chain reaction (PCR), time-resolved fluoro-immunoassay (TRFIA).