ORIGINAL ARTICLE Evaluating the role of tissue microRNA‐27b as a diagnostic marker for oral lichen planus and possible correlation with CD8 Sana Maher Aghbari 1 | Shaimaa Omar Zayed 2 | Olfat Gamil Shaker 3 | Abdelrahman Ibrahim Abushouk 4 1 Oral Medicine, Faculty of Dentistry, Aden University, Aden, Yemen 2 Oral Pathology, Faculty of Dentistry, Cairo University, Cairo, Egypt 3 Medical Biochemistry and Molecular Biology Department, Faculty of Medicine Cairo University, Cairo, Egypt 4 Faculty of Medicine, Ain Shams University, Cairo, Egypt Correspondence Sana Maher Aghbari, Faculty of Dentistry, Aden University, Aden, Yemen. Email: Sana_aghbary@hotmail.com Background: MicroRNA‐27b (miR27b) is a small, non‐coding RNA that is involved in physiological keratinocyte differentiation and regulating inflammatory processes. We performed this study to investigate the value of miR27b as a diagnostic marker for oral lichen planus (OLP) and the correlation between CD8 (cytotoxic T‐cell marker) and miR27b tissue expression in OLP patients. Methods: Forty participants (including 20 OLP patients and 20 controls) underwent oral biopsy. The obtained specimens were examined by immunostaining and quanti- tative RT‐PCR for CD8 and miR27b tissue expression, respectively. We used the Spearman rank correlation test to evaluate the correlation between both variables. Results: Our analysis showed that in comparison with healthy tissues, OLP tissue samples exhibited significantly higher CD8 levels (P < 0.01), as well as a significant downregulation of miR27b expression (P < 0.0001). Upon comparing different OLP subgroups, no significant difference was detected in terms of miR27b expression; however, the tissue levels of CD8 varied significantly (highest in the erosive sub- group and lowest in the papular/plaque/reticular subgroup). The Spearman rank anal- ysis showed a negative correlation between tissue expression of miR27b and CD8; however, this was not statistically significant (P > 0.05). Further, the receiver operat- ing characteristic curve of tissue miR27b as an OLP biomarker revealed 100% sensi- tivity and 65% specificity at cutoff value of 4.4. Conclusion: This study demonstrated increased CD8 levels and downregulation of miR27b in OLP tissues, compared to healthy tissues. Moreover, it revealed the potential of miR27b as an OLP disease biomarker. The possible negative correlation between CD8 and miR27b tissue expression requires further investigation in larger studies. KEYWORDS CD8, cytotoxic T cells, miR27b, oral lichen planus 1 | INTRODUCTION Oral lichen planus (OLP) is an inflammatory mucocutaneous disease that follows a chronic clinical course and affects about 2% of the worldwide population. 1 It is recognized by the World Health Organization (WHO) as a premalignant condition. 2,3 Pathologically, it is characterized by (a) degeneration of the basal epithelial cells; (b) rupture of the basement membrane; and (c) sub‐epithelial infiltration by T‐helper and T‐cytotoxic lymphocytes. 4,5 However, to date, the exact etiology, pathogenesis, and malignant transformation mechanisms of OLP are not yet clear. Received: 30 April 2018 | Revised: 3 September 2018 | Accepted: 26 September 2018 DOI: 10.1111/jop.12785 J Oral Pathol Med. 2018;1–6. wileyonlinelibrary.com/journal/jop © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd | 1