: Background: The aberrant expression of microRNAs (miRNAs) has been associated with several diseases, including cancer, inflammatory, and autoimmune conditions. Interest in salivary miRNAs as non-invasive tools for the diagnosis of malignancies and systemic diseases is rapidly increasing. The present systematic review was developed for answering the question: “Are salivary microRNAs reliable biomarkers for diagnosis of cancer and systemic diseases?” Methods: The application of inclusion and exclusion criteria led to the selection of 11 papers. Critical appraisals and quality assessments of the selected studies were performed through the National Institute of Health “Study Quality Assessment Tool” and the classification of the Oxford Center for Evidence-Based Medicine. Results: Seven studies reported statistically significant correlations between one or more salivary miRNAs and the investigated disease. The critical analysis allowed us to classify only two studies (18.2%) as having “good” quality, the rest being scored as “intermediate” (8; 73%) and “poor” (1; 9%). Evidence exists that salivary miR-940 and miR-3679-5p are reliable markers for pancreatic cancer and that miR140-5p and miR301a are promising molecules for the salivary diagnosis of gastric cancer. Conclusions: Further studies, possibly avoiding the risk of bias highlighted here, are necessary to consolidate these findings and to identify new reliable salivary biomarkers.

The detection of salivary molecules associated with pathological and physiological alterations has encouraged the search of novel and non-invasive diagnostic biomarkers for oral health evaluation. While genomic, transcriptomic, and proteomic profiles of human saliva have been reported, its metabolic composition is a topic of research: metabolites in submandibular/sublingual saliva have never been analyzed systematically. In this study, samples of whole, parotid, and submandibular/sublingual saliva from 20 healthy donors, without dental or periodontal diseases, were examined by nuclear magnetic resonance. We identified metabolites which are differently distributed within the three saliva subtypes (54 in whole, 49 in parotid, and 36 in submandibular/sublingual saliva). Principal component analysis revealed a distinct cluster for whole saliva and a partial overlap for parotid and submandibular/sublingual metabolites. We found exclusive metabolites for each subtype: 2-hydroxy-3-methylvalerate, 3-methyl-glutarate, 3-phenylpropionate, 4-hydroxyphenylacetate, 4-hydroxyphenyllactate, galactose, and isocaproate in whole saliva; caprylate and glycolate in submandibular/sublingual saliva; arginine in parotid saliva. Salivary metabolites were classified into standard and non-proteinogenic amino acids and amines; simple carbohydrates; organic acids; bacterial-derived metabolites. The identification of a salivary gland-specific metabolic composition in healthy people provides the basis to invigorate the search for salivary biomarkers associated with oral and systemic diseases.

Metabolome is the comprehensive assembly of metabolites in biologic tissues and/or fluids. The study of metabolic profiles may give important information about the health status

Aim. Salivary transcriptomics is an relatively new field of research that will probably allow in the next feature the development of some non-invasive diagnostic techniques. Among transcripts, microRNAs (miRNA) , small non-coding RNA molecules which regulate the expression of target genes seem to be the most promising molecules. Expression of several miRNAs are associated with the development of specific human diseases, including malignant tumours. The aim of the present research is to perform a systematic review in order to establish if there is scientific evidence supporting the role of salivary miRNA for the diagnosis of systemic diseases and malignant tumors. Materials and Methods. We searched into the Medline database, using as entry terms “salivary microRNA”, “saliva and microRNA”, “saliva and tumor”, “saliva and cancer”, “saliva and carcinoma”, “saliva and malignancies” and “saliva and systemic diseases”. Only articles in English and published after 2000 were included in the review. Inclusion criteria were established including only studies specifically reporting data on saliva sample; studies analyzing peculiar microRNA; studies evaluating patients with systemic diseases where miRNA were used diagnostic purpose. We excluded studies on animals or in vitro samples and papers dealing with systemic microbial infections, hormones, drug dosage. Case reports, conference proceedings, personal communication and reviews were also excluded. We further excluded researches investigating salivary biomarkers in patients with systemic diseases with oral, oropharyngeal and esophageal involvement. References listed in reviews, were screened in order to identify papers possibly missing from the database search. From each studies we extrapolated title, authors, publication year, systemic diseases, type of miRNA, devices used for analyse the samples and significances of results. We divided studies on the basis of the disease. Qualitative analysis was performed using as tool for quality score assessment the guidelines provided by the National Institute of Health (NIH - scores ranging from “poor” to “good”). Results. The preliminary research initially obtained 12327 papers. After exclusion of repetition 3422 papers were included for further evaluation. The evaluation of title, abstract and the application of inclusion and exclusion criteria eventually led to the identification of 6 articles. One more study was obtained from screening of reference list. Four studies were focused on pancreatic cancer (among others miRNA identified were the following: miR‑1246, miR‑3976, miR‑4306,miR‑4644, miR-21,miR-34a, miR-155, miR-196a, miR-200b, miR-376a, hsa-miR-23a, hsa-miR-23b, miR-29c, hsa-miR-210, miR-4433-5p, miR-4665-3p, miR-940, miR-1273g-3p, miR-3676-5p, miR-3679-5p, miR-3940-5p, miR-4327, miR-4442 and miR-5100), one on bowel inflammatory diseases (miRNA identified: miR-19a, miR-21, miR-31, miR-101, miR-146a, and miR-375), one on colorectal cancer (miR-21) and one on prostate cancer (miR-141, miR-21). Six articles searched miRNA through quantitative real-time PCR and one article used RNA microarray. Most of studies (6 on seven) obtained statistically significant association between miRNA and the specific disease. Only one study obtained no significant results. Following the NIH guidelines, 5 studies were scored as “fair” (4 studies on pancreatic cancer and one on colorectal cancer) and two studies were scored as “poor” (bowel inflammatory diseases and prostate cancer). No one of the papers could be identified has having a “good” quality. Discussion. The results of our review highlight the paucity of papers focused on early diagnosis of systemic diseases through salivary miRNA. The few number and the low quality of articles show the necessity of more comprehensive studies. More studies are needed, also on the basis of the encouraging results obtained from each experiment (statistically significant correlation) and the relatively high quantitative of such molecules in saliva. Particularly, mir21 seems to be the salivary miRNA molecule present in most of the diseases studied.

Oral squamous-cell carcinoma, the most frequent malignant neoplasm of the oral cavity, has a poor 5 years survival rate.