Background: Oral lichen planus (OLP), a relatively common chronic inflammatory disease of the oral mucosa, is considered to be a premalignant disorder of the oral cavity. Previously, several biomarkers have been tested for their diagnostic potential. Here, we aimed to investigate the diagnostic potential of four miRNAs, miR-21, -125a, -31 and -200a, known to be involved in oral squamous cell carcinoma (OSCC) development, in the saliva of OLP patients as also their putative relation to OSCC development in these patients.
Materials and methods: Saliva samples from 30 patients with OLP were collected, 15 of whom were diagnosed with dysplasia upon histopathologic examination. In addition, 15 saliva samples from patients with OSCC and 15 saliva samples from healthy donors were collected. After RNA extraction, the respective miRNA levels were assessed by quantitative RT-PCR.
Results: We found that the miR-21 levels were significantly increased in saliva samples derived from patients with OLP, dysplastic OLP and OSCC, compared to those from healthy controls (p = 0.012, p = 0.0017 and p < 0.0001, respectively). Conversely, significant decreases in miR-125a levels were found in the OLP, dysplastic OLP and OSCC samples, compared to those from healthy controls (p < 0.0014, p < 0.0001 and p < 0.0001, respectively). In addition, significant increases in miR-31 levels were found in samples derived from dysplastic OLP and OSCC patients, but not in those from nondysplastic OLP patients, compared to those in healthy controls (p = 0.01 and p = 0.004, respectively). Finally, we found that the miR-200a levels were significantly decreased only in samples derived from OSCC patients (p < 0.0001).
Conclusions: From our data we conclude that increased miR-21 levels in conjunction with decreased miR-125a levels in saliva of OLP patients may be indicative for a poor prognosis. Conversely, we conclude that lack of significant alterations in miR-31 and miR-200a levels in saliva of OLP patients may be indicative for absence of malignant transformation.
Keywords: Oral lichen planus; Oral squamous cell carcinoma; Saliva; microRNA.