What can we learn from treatments of oral lichen planus?

Oral lichen planus (OLP), a T-lymphocyte-mediated disease of the oral mucosa, has a complex pathogenesis that involves a number of factors. The disease is characterized by recurrent episodes and requires continuous follow up, and there is no curative treatment available. Erosive lichen planus, among others, has a risk of malignant transformation and requires standardized treatment to control its progression. Different clinical subtypes of oral lichen planus require appropriate treatment. Pharmacological treatments are the most widely available and have the greatest variety of options and a number of novel pharmacological treatments are presented as highlights, including JAK enzyme inhibitors. The second is photodynamic therapy, which is the leading physiological treatment. In addition, periodontal treatment and psychological treatment should not be neglected. In this review, we briefly discuss the most recent developments in therapies for oral lichen planus after summarizing the most widely used clinical treatments, aiming to provide different proposals for future clinical treatment.

[Study of the kinetics of accumulation and distribution of the photosensitizer photoditazin in the oral mucosa in patients with lichen planus]. / Izuchenie kinetiki nakopleniya i raspredeleniya fotosensibilizatora fotoditazin v slizistoi obolochke rta u patsientov s krasnym ploskim lishaem.

THE AIM OF THE STUDY: Was to explore the accumulation and distribution of the photosensitizer Photoditazine in the oral mucosa when applied to pathological lesions in patients with severe forms of lichen planus. MATERIAL AND METHODS: A clinical and laboratory examination was carried out in 50 patients with severe forms of lichen planus (bullous and erosive-ulcerative) aged 18 to 70 years, including 6 men and 44 women. For autofluorescent imaging a LED device with a wavelength in the violet region of the spectrum (400±10 nm) was used. Quantitative registration of the kinetics of accumulation and distribution of the photosensitizer was carried out using the method of local fluorescence spectroscopy by measuring the fluorescence spectra. RESULTS: The measurements were made before applying the photosensitizer, 10, 20 and 30 minutes after application. The study showed that in most patients with erosive-ulcerative and bullous forms of lichen planus, the accumulation of the photosensitizer in the lesions on the oral mucosa increased as the exposure time increased from 20 to 30 minutes. The fastest accumulation of the photosensitizer occurred in the areas of mucosal lesions with the most pronounced vascularization, namely, in the area of the tongue and the bottom of the oral cavity. CONCLUSION: Using the method of local fluorescence spectroscopy, the kinetics of accumulation and destruction of photosensitizer in pathological areas of the oral mucosa was determined, and therefore the optimal time of laser exposure to the lesion was determined.

Oral lichen planus and lichenoid lesions - challenges and pitfalls for the general dental practitioner.

Lichen planus is a chronic, mucocutaneous inflammatory condition which, due to its prevalence, will be familiar to the dental profession. However, diverse forms of presentation, important differential diagnosis, potential malignant change and monitoring requirements often result in challenges for those in primary care. This paper looks to examine these challenges and provide information to support those who are involved in recognition and management of patients with lichen planus.

Evaluation of the association between TNF-α-1031 T/C polymorphism with oral lichen planus disease.

BACKGROUND: Oral lichen planus (OLP) is a T-cell-mediated autoimmune disease that affects the epithelial cells of the oral cavity. This study was performed to investigate any possible relationship between - 1031(T/C) polymorphism (rs1799964) of the tumor necrosis factor α (TNF-α) gene with the risk and severity of oral lichen planus (OLP) disease among an Iranian population. METHOD: Saliva samples were collected from 100 patients with OLP and a similar number of healthy controls (age and sex-matched). Then, DNA was extracted from the collected samples for genotyping TNF-α-1031 T/C polymorphism using the PCR-CTPP method. The results were assessed using SPSS software. RESULTS: The findings revealed a significantly higher prevalence of the C allele in OLP patients (53%) compared to healthy controls (36%), suggesting an association between TNF-alpha gene polymorphism and OLP. A multivariate logistic regression analysis supported this finding, as the presence of the C allele was significantly associated with an increased risk of OLP [χ2 = 4.17, p = 0.04, 95% CI = 1.01-2.65, OR = 1.64]. However, our data indicated no significant association between TNF-alpha-1031 T/C gene polymorphism and OLP severity. CONCLUSIONS: These findings provide the first evidence supporting a possible role of TNF-α-1031 T/C gene polymorphism in OLP susceptibility in the Iranian population. The findings of this study demonstrate a positive association between TNF-α-1031 C/T allele distribution and the risk of OLP disease in the Iranian population. Therefore, carrying the C allele may increase the susceptibility to OLP disease.

Effects of Curcumin on the treatment of oral lichen planus symptoms: a systematic review and meta-analysis study.

BACKGROUND AND OBJECTIVES: Oral lichen planus (OLP) is a relatively common chronic T-cell-mediated disease that can cause significant pain, particularly in its erosive or ulcerative forms. This study aimed to examine the therapeutic impact of curcumin on symptoms of OLP. MATERIALS AND METHODS: This meta-analysis was performed according to the PRISMA guidelines. All related English documents indexed in electronic databases (including PubMed, Web of Science, Scopus, Embase, Wiley, Cochrane, and ProQuest databases [updated to August 15, 2023]) were retrieved. Data were double-extracted into a predefined worksheet, and quality analysis was performed using the Joanna Briggs Institute (JBI) scale. We carried out meta-analyses, and the random effects model was used to estimate the differences in erythema, lesion size, and pain between the curcumin control groups. RESULTS: The search identified 289 studies, of which 10 were found to meet the inclusion criteria. The overall findings of the meta-analysis revealed that curcumin did not have a significant effect on erythema of OLP (standardized mean difference [SMD] = -0.14; 95% CI, -0.68 to 0.40; P = 0.61; I2 = 57.50%), lesion size of OLP (SMD = -0.15; 95% CI, -0.45 to 0.15; P = 0.33; I2 = 28.42%), and pain of OLP (SMD = -0.38; 95% CI, -0.97 to 0.22; P = 0.22; I2 = 86.60%). However, subgroup analysis based on treatment duration indicated that 2-week treatment duration was significantly associated with a reduction in OLP pain (n = 3; SMD = -1.21; 95% CI, -2.19 to -0.23; P = 0.01). CONCLUSIONS: Curcumin had no significant effect on erythema, lesion size, and pain of OLP compared to the control groups. However, subgroup analysis revealed that curcumin was more effective in reducing pain in non-randomized trials and in trials with a treatment duration of 2 weeks.

Photodynamic therapy for refractory erosive oral lichen planus: a case series study.

Oral lichen planus is a chronic inflammatory disease that occurs on the oral mucosa and is an oral potentially malignant disease. Treatment of oral lichen planus aims to promote healing of the erosion, relieve pain, reduce recurrence of the erosion, and prevent canceration. Corticosteroids are the first line of treatment for oral lichen planus. Refractory oral lichen planus is a clinical classification of oral lichen planus that has not responded to corticosteroid treatment for more than 2 months. Topical 5-aminolevulinic acid-mediated photodynamic therapy is an innovative and effective treatment for potentially malignant oral diseases and has been reported as an alternative treatment to conventional therapies for oral lichen planus. On this basis, we report 3 cases of refractory erosive oral lichen planus in which persistent erosive lesions healed after topical application of 5-aminolevulinic acid-mediated photodynamic therapy without any adverse effects or any signs of recurrence. Topical 5-aminolevulinic acid-mediated photodynamic therapy will become an effective clinical treatment for refractory erosive oral lichen planus.

Oral bacteriome and oral potentially malignant disorders: A systematic review of the associations.

INTRODUCTION: Periodontal bacteria can infiltrate the epithelium, activate signaling pathways, induce inflammation, and block natural killer and cytotoxic cells, all of which contribute to the vicious circle of carcinogenesis. It is unknown whether oral dysbiosis has an impact on the etiology or prognosis of OPMD. AIMS: Within this paradigm, this work systemically investigated and reported on the composition of oral microbiota in patients with oral potentially malignant disorders (OPMD) versus healthy controls. METHODS: Observational studies that reported next generation sequencing analysis of oral tissue or salivary samples and found at least three bacterial species were included. Identification, screening, citation analysis, and graphical synthesis were carried out. RESULTS: For oral lichen planus (OLP), the bacteria with the highest abundance were Fusobacterium, Capnocytophaga, Gemella, Granulicatella, Porphyromonas, and Rothia; for oral leukoplakia (OLK), Prevotella. Streptococci levels in OLK and OLP were lower. The usage of alcohol or smoke had no effect on the outcomes. CONCLUSIONS: An increase in periodontal pathogenic bacteria could promote the development and exacerbation of lichen. Effective bacteriome-based biomarkers are worthy of further investigation and application, as are bacteriome-based treatments.

Painful refractory erosive tongue lichen planus with malignant transformation.

We present a recent case of long standing erosive tongue lichen planus successfully treated by wide excision and reconstruction with a submental artery island flap. Erosive Lichen Planus is a progressive indolent potentially malignant condition that tends to end up with severe somatic or even neuropathic pain and malignant changes towards its final stages as elaborated in the presented commentary.

Prognosis of oral epithelial dysplasia in individuals with and without oral lichen planus.

OBJECTIVES: To investigate the role of oral lichen planus (OLP) on the long-term prognosis of oral epithelial dysplasia (OED). METHODS: Retrospective single-centre cohort study using the 2007-2019 database of the Head and Neck Cancer and Oral Medicine units of University College London Hospital. The exposure of interest was the presence of OLP, and the prognostic outcomes included the development of new primary episodes of OED, progression to malignancy and mortality. Cox proportional hazard and Poisson regression models were performed. RESULTS: A total of 299 patients, of whom 144 had OED arising on the background of OLP (OLP/OED) and 155 had OED without underlying OLP (non-OLP/OED), were included. A pre-existing diagnosis of OLP was significantly associated with a twofold increased risk of subsequent primary OED events (HR = 2.02, p = 0.04), which also developed faster (1.46 vs. 2.96 years, p = 0.04) and with more involvement of non-cancer-prone sites (p = 0.001) than in the non-OLP/OED group. There was no difference between groups in the progression to malignancy or mortality. CONCLUSIONS: Oral lichen planus/OED patients are at higher risk of multiple episodes of primary OED, which can develop faster and at non-cancer-prone sites as compared to non-OLP/OED individuals. Further research is needed to clarify the effects of OLP upon progression to OSCC and mortality.

Assessment of periodontal status in patients with oral lichen planus.

OBJECTIVE: Inflammatory pathogenesis is common to periodontitis and oral lichen planus. This study was conducted to assess and compare the periodontal status of patients with and without oral lichen planus. METHOD AND MATERIALS: 108 patients comprising 54 with oral lichen planus and 54 age-matched systemically healthy participants without oral lichen planus were selected. Periodontal parameters, ie Plaque Index, Gingival Index, bleeding on probing, probing pocket depth, clinical attachment level, and periodontal phenotype were measured. RESULTS: On comparing the test and control groups, statistically significant differences were observed in respect to Plaque Index (P = .00), Gingival Index (P = .00), and bleeding on probing (P = .00). A higher proportion of sites with deeper pockets was observed in the test group (P = .00). On comparison of various oral lichen planus subtypes, significant difference was observed in respect to Gingival Index (P = .00) and bleeding on probing (P = .00). A higher proportion of sites with deeper pockets (P = .01) and greater CAL (P = .00) was observed in the erosive/atrophic subgroup compared to the reticular group. However, the differences between the reticular (a less severe form of oral lichen planus) and control group in terms of Gingival Index (P = .94), Plaque Index (P = .05), bleeding on probing (P = .17), probing pocket depth (P = .56), and clinical attachment level (P = .23) were not statistically significant. Statistically significant differences were observed in terms of Gingival Index (P = .01) and bleeding on probing (P = .00) between thin and thick periodontal phenotypes in the oral lichen planus group. Statistically significant positive correlations in periodontal parameters with increased gingival involvement and severity were observed using Spearman rank correlation coefficient. CONCLUSION: Significantly greater periodontal inflammation in the test group means there is a risk of greater attachment loss in future. Thus, increased attention towards periodontal health in these patients might reduce the rate of disease progression.

Desquamative gingivitis treatment with topical tacrolimus applied to a custom tray: an open trial regarding its efficacy on patients' symptoms.

OBJECTIVE: To evaluate the efficacy of topical tacrolimus offered on a custom tray to treat desquamative gingivitis (DG). STUDY DESIGN: Eighteen patients with symptomatic DG related to oral lichen planus (OLP) or mucous membrane pemphigoid (MMP) were selected, of which 13 completed the study. Periodontal treatment was followed by the fabrication of a custom silicone tray to apply a tacrolimus gel formulation (0.1%). Clinical evaluation (complaint of pain and burning - visual analog scale from 0 to 10; and the presence of erythema, desquamation, vesicle/blister, erosion, ulcer, and bleeding) was performed by the same examiner on day 1, and every 15 days for 90 days. RESULTS: Total remission was found in 4 patients (30.76%). Partial remission was found in 69.24% of the patients, classified with an excellent (30.76%), good (30.76%), and regular (7.69%) recovery, respectively. There was a reduction of about 60% in pain and 65% in burning sensation complaints. Wilcoxon test revealed significant differences between pre- and post-treatment pain and burning sensation symptoms (P < .01). CONCLUSION: Topical application of 0.1% tacrolimus gel was effective in the treatment of DG in controlling pain and burning sensation, leading to the clinical remission of gingival lesions in patients with OLP and MMP.

The expression of p53, ki67 and COX-2 in erosive-type oral lichen planus.

Oral lichen planus is a chronic inflammatory disease that affects the oral mucosa and may undergo malignant changes, which can be reflected in the expression of specific proteins that are responsible for maintaining cellular mitosis and apoptosis. The study aimed to investigate the expression of p53, ki67, and COX-2 in erosive lichen planus using immunohistochemistry to correlate these findings with the histological aspects of the disease. Thirty-three biopsies of erosive lichen planus were collected and diagnosed based on histological and clinical criteria. The blocks were processed for immunohistochemistry to assess p53, ki67, and COX-2 expression in the basal layer, suprabasal, and inflammatory infiltrate respectively. The histological analysis of the samples showed no dysplasia or metastasis. P53 stained positively in 80% of the samples, while ki67 was positive in all the cases, ranging from 5% to 85% positivity. COX-2 expression ranged from 0-50% positivity. The highest expression of p53 was observed in 8 cases (24.2%), with a maximum of 5%, and ki67 exhibited the highest expression of 90% in 3 cases (9.1%). COX-2 was negative in 27 cases (81.8%) and positive in 6 cases (18.1%), with the highest expression at 50% in 1 case and 10 % positivity in 4 cases (12.1%). In our study, the markers p53, ki67, and COX-2 proved to be useful for detecting the proliferative, inflammatory, and physiologic states of the keratinocytes. However, they did not demonstrate utility in detecting any malignant transformation.

Toll-like receptor 9-positive plasmacytoid dendritic cells promote Th17 immune responses in oral lichen planus stimulated by epithelium-derived cathepsin K.

Oral lichen planus (OLP) is a chronic inflammatory disease associated with T cell infiltration. The crosstalk between oral epithelium and mucosal T cells was considered to be crucial in the pathogenesis of OLP. Here, we selectively extracted the normal epithelium (NE) and lesional epithelium (LE) of buccal mucosa specimens from three patients with OLP by laser capture microdissection due to identify the pathogenic factors. Cathepsin K (CTSK) was identified as one of common upregulated genes in the LE by DNA microarray. Immunohistochemically, CTSK was distinctly detected in and around the LE, while it was rarely seen in the NE. Recent studies showed that CTSK enhanced Toll-like receptor 9 (TLR9) signaling in antigen-presenting cells, leading to Th17 cell differentiation. TLR9 expression mainly co-localized with CD123+ plasmacytoid dendritic cells (pDCs). The number of RORγt-positive cells correlated with that of CTSK-positive cells in OLP tissues. CD123+ pDCs induced the production of Th17-related cytokines (IL-6, IL-23, and TGF-ß) upon stimulation with TLR9 agonist CpG DNA. Moreover, single cell RNA-sequencing analysis revealed that TLR9-positive pDCs enhanced in genes associated with Th17 cell differentiation in comparison with TLR9-negative pDCs. CTSK could induce Th17-related production of CD123+ pDCs via TLR9 signaling to promote the pathogenesis of OLP.

ALDH1 immunoexpression in epithelial and stromal cells of oral lichen planus and lesions with lichenoid inflammatory infiltrate

Background: Oral Lichen Planus is a potential malignant disorder and shares clinical and histopathological features with other similar lesions. ALDH1 is a specific biomarker for stem cells identification, however its role in stromal cells of immune inflammatory infiltrate has not been explored. The aim of this study was to investigate the ALDH1 immunoexpression in epithelial and stromal cells of Oral Lichen Planus and other lesions with lichenoid inflammatory infiltrate. Material and Methods: 64 samples of Oral Lichen Planus, Oral Lichenoid Lesions, Oral Leukoplakia and Unspecific Chronic Inflammation were included. ALDH1 was evaluated in both epithelium and stromal cells. ALDH1+ cells ≥ 5% were considered positive in epithelium. Stromal cells were evaluated semi quantitatively. Fields were ranked in scores, according to criteria: 1 (0 to 10%); 2 (11 to 50%) and 3 (>50%). The mean value of the sum of the fields was the final score. Statistical differences among groups were investigated, considering p < 0.05. Results: ALDH1 expression in epithelium was low in all groups without difference among them. ALDH1+ cells in the lamina propria were higher for Lichen Planus [2.0], followed by Leukoplakia [1.3], Lichenoid lesions [1.2] and control [1.1] (p<0.05). Conclusions: ALDH1 immunoexpression in epithelium of lichenoid potential malignant disorders did not show a contributory tool, however ALDH1 in stromal cells of lichen planus might be involved in the complex process of immune regulation associated with the pathogenesis of this disease. (AU)

The expression of Th17/Treg in oral submucosal fibrosis carcinogenesis and the significance in the development of mucosal lesions.

It targets to explore the expression of Th17/Treg in oral submucous fibrosis (OSF) carcinogenesis and its significance in the development of mucosal lesions. In this research, 100 patients with OSF who visited our hospital for surgical treatment from March 2020 to April 2022 were selected. Based on pathological examination results, the patients were divided into 27 patients with oral leukoplakia (OK) group, 14 patients with oral lichen planus (OLP) group, 9 patients with oral squamous cell carcinoma (OSCC) group, and 50 patients with OSF group. It adopted flow cytometry (FC) to calculate the ratio of peripheral blood Th17 cells and Treg cells in four groups, and the Th17/Treg ratio was calculated; The area of oral mucosal lesions (OML) from patients was collected. It needs to compare the differences in Th17/Treg ratio and OML area among four groups and determine the correlation between indicators. ROC curve was used to analyze the diagnostic threshold of the Th17/Treg ratio for carcinogenesis. Except for the OK and OLP, it had statistical significance differences in Th17, Treg cells, and Th17/Treg ratio (P<0.001); The area of OML in the OK, OLP, and OSCC was higher than that in the simple OSF, with statistical significance (P<0.001); Th17 (%), Treg (%), and Th17/Treg all had direct ratio with the area of OML; The area of OML has directed ratio with the development of mucosal lesions (r>0, P<0.05); The areas under the ROC curve for patients with OSF combined with OK, OLP, or OSCC with Th17 (%), Treg (%), Th17/Treg, and OML area were 0.560, 0.986, 0.936, and 0.466, respectively. The expression of Th17/Treg is elevated in oral submucosal fibrosis and carcinogenesis. When mucosal lesions progress or become cancerous, the Th17/Treg ratio increases accordingly, and it has more clinical value than the increase in the OML area.

ALDH1 immunoexpression in epithelial and stromal cells of oral lichen planus and lesions with lichenoid inflammatory infiltrate.

BACKGROUND: Oral Lichen Planus is a potential malignant disorder and shares clinical and histopathological features with other similar lesions. ALDH1 is a specific biomarker for stem cells identification, however its role in stromal cells of immune inflammatory infiltrate has not been explored. The aim of this study was to investigate the ALDH1 immunoexpression in epithelial and stromal cells of Oral Lichen Planus and other lesions with lichenoid inflammatory infiltrate. MATERIAL AND METHODS: 64 samples of Oral Lichen Planus, Oral Lichenoid Lesions, Oral Leukoplakia and Unspecific Chronic Inflammation were included. ALDH1 was evaluated in both epithelium and stromal cells. ALDH1+ cells ≥ 5% were considered positive in epithelium. Stromal cells were evaluated semi quantitatively. Fields were ranked in scores, according to criteria: 1 (0 to 10%); 2 (11 to 50%) and 3 (>50%). The mean value of the sum of the fields was the final score. Statistical differences among groups were investigated, considering p < 0.05. RESULTS: ALDH1 expression in epithelium was low in all groups without difference among them. ALDH1+ cells in the lamina propria were higher for Lichen Planus [2.0], followed by Leukoplakia [1.3], Lichenoid lesions [1.2] and control [1.1] (p<0.05). CONCLUSIONS: ALDH1 immunoexpression in epithelium of lichenoid potential malignant disorders did not show a contributory tool, however ALDH1 in stromal cells of lichen planus might be involved in the complex process of immune regulation associated with the pathogenesis of this disease.

Immunohistochemical expression of T-cell subsets (CD4 and CD8) in oral lichen planus.

Introduction: oral lichen planus (OLP) is a common oral mucosal disease with various clinical manifestations. The most predominant types are reticular and erosive. Despite extensive research on the causes of OLP, the exact etiology remains unclear. However, it is believed that a T-cell-mediated response, which triggers the apoptosis of oral epithelial cells, may contribute to the development of this disorder. This study aims to investigate the different types of T-cells (specifically CD4 and CD8) present in OLP tissue samples. By using immunohistochemistry, the expressions of cluster of differentiation 4 (CD4) and cluster of differentiation 8 (CD8) will be evaluated in biopsy samples taken from OLP patients who exhibit various clinical presentations. Methods: this study was a retrospective analysis study. Oral lichen planus was established histologically in forty paraffin-embedded tissue samples. Blocks of OLP were diagnosed and characterized as reticular or erosive. Immunohistochemical staining was conducted using a monoclonal antibody for (CD4) and a polyclonal antibody for CD8. Semi-quantitative techniques were used to analyze the patterns of positively stained cells. Results: forty biopsies of OLP cases were obtained from 24 females and 16 males. The mean age was (49.15±11.39) years. Using an immunohistochemical method, the proportion of CD4 expression: CD8 expression among the epithelial-connective tissue interface was shown to be 24 (60%) cases with a predominance of CD8, 9 (22.5%) cases with no difference, and only 7 (17.5%) cases with a predominance of CD4. The proportion of CD4: CD8 among perivascular parts was shown to be 8 (20%) cases with a predominance of CD8, 20 (50%) cases with no difference, while only 12 (30%) cases had a predominance of CD4. The CD4 perivascular expression was significantly stronger in (71.4%) of erosive OLP than in reticular cases. Conclusion: T-cell subsets (CD4 and CD8) were found in the OLP infiltrates. The correlation may have contributed to the pathogenesis of OLP.

CD8+ tissue-resident memory T cells induce oral lichen planus erosion via cytokine network.

CD8+ tissue-resident memory T (CD8+ Trm) cells play key roles in many immune-inflammation-related diseases. However, their characteristics in the pathological process of oral lichen planus (OLP) remains unclear. Therefore, we investigated the function of CD8+ Trm cells in the process of OLP. By using single-cell RNA sequencing profiling and spatial transcriptomics, we revealed that CD8+ Trm cells were predominantly located in the lamina propria adjacent to the basement membrane and were significantly increased in patients with erosive oral lichen planus (EOLP) compared to those with non-erosive oral lichen planus (NEOLP). Furthermore, these cells displayed enhanced cytokine production, including IFN-γ (Interferon-gamma, a pro-inflammatory signaling molecule), TNF-α (Tumor Necrosis Factor-alpha, a cytokine regulating inflammation), and IL-17 (Interleukin-17, a cytokine involved in immune response modulation), in patients with EOLP. And our clinical cohort of 1-year follow-up was also supported the above results in RNA level and protein level. In conclusion, our study provided a novel molecular mechanism for triggering OLP erosion by CD8+ Trm cells to secrete multiple cytokines, and new insight into the pathological development of OLP.

CircHLA-C: A significantly upregulated circRNA co-existing in oral leukoplakia and oral lichen planus.

BACKGROUND: Oral leukoplakia (OLK) and oral lichen planus (OLP) are common precancerous lesions of the oral mucosa. The role of circular RNAs (circRNAs) in OLK and OLP is unclear. The aim of this study was to evaluate the circRNA expression profiles of OLK and OLP, and further explore the potential role of circRNAs in the pathogenesis of these two diseases. METHODS: High throughput sequencing technology was performed to detect the differentially expressed circRNA in OLK (n = 6), OLP (n = 6), oral squamous cell carcinoma (n = 6), and normal oral mucosa tissues (n = 6). Expression of selected circRNAs was validated by qRT-PCR, enzyme tolerance assay, and Sanger sequencing. Expanded sample size validation was done in 20 tissue pairs. The biological processes and signal pathways involved in differential circRNA were analyzed by GO and KEGG enrichment. TargetScan and MiRanda were used to predict miRNAs downstream of circRNA and draw competitive endogenous RNA network diagram. RESULTS: Forty-nine circRNAs were significantly altered in OLK and OLP, including 30 upregulated and 19 downregulated circRNAs. The five selected circRNAs were validated by qRT-PCR, Sanger sequencing, and RNase R assay. GO and KEGG analyses indicated that the upregulated circHLA-C may be involved in the biological process of immune function of OLK and OLP. Bioinformatics analysis indicated that circHLA-C may be involved in the progression of OLK and OLP as a ceRNA. In validation with expanded sample size, PCR results showed that circHLA-C expression was significantly upregulated in OLK and OLP. ROC analysis indicated that circHLA-C has potential diagnostic value with good accuracy and specificity. CONCLUSION: Our study revealed that circHLA-C is the most significantly upregulated circRNA co-existing in OLK and OLP, and we preliminarily discuss the role of circHLA-C in the etiopathogenesis and progression of OLK and OLP.