Oral and non-oral lichen planus show genetic heterogeneity and differential risk for autoimmune disease and oral cancer.

Lichen planus (LP) is a T-cell-mediated inflammatory disease affecting squamous epithelia in many parts of the body, most often the skin and oral mucosa. Cutaneous LP is usually transient and oral LP (OLP) is most often chronic, so we performed a large-scale genetic and epidemiological study of LP to address whether the oral and non-oral subgroups have shared or distinct underlying pathologies and their overlap with autoimmune disease. Using lifelong records covering diagnoses, procedures, and clinic identity from 473,580 individuals in the FinnGen study, genome-wide association analyses were conducted on carefully constructed subcategories of OLP (n = 3,323) and non-oral LP (n = 4,356) and on the combined group. We identified 15 genome-wide significant associations in FinnGen and an additional 12 when meta-analyzed with UKBB (27 independent associations at 25 distinct genomic locations), most of which are shared between oral and non-oral LP. Many associations coincide with known autoimmune disease loci, consistent with the epidemiologic enrichment of LP with hypothyroidism and other autoimmune diseases. Notably, a third of the FinnGen associations demonstrate significant differences between OLP and non-OLP. We also observed a 13.6-fold risk for tongue cancer and an elevated risk for other oral cancers in OLP, in agreement with earlier reports that connect LP with higher cancer incidence. In addition to a large-scale dissection of LP genetics and comorbidities, our study demonstrates the use of comprehensive, multidimensional health registry data to address outstanding clinical questions and reveal underlying biological mechanisms in common but understudied diseases.

Detection of herpes simplex virus in oral tongue squamous cell carcinoma.

Introduction: Oral tongue squamous cell carcinoma (OTSCC) is the most common cancer of the oral cavity. Contradictory results have been observed on the involvement of herpes simplex virus 1 (HSV-1) in oral squamous cell carcinomas. Here, we aimed to study the predominance of HSV-1 or HSV-2 in oral HSV infections and to investigate the presence of HSV-1 in OTSCC and its effect on carcinoma cell viability and invasion. Methods: The distribution of HSV types one and two in diagnostic samples taken from suspected oral HSV infections was determined from the Helsinki University Hospital Laboratory database. We then analysed 67 OTSCC samples for HSV-1 infection using immunohistochemical staining. We further tested the effects of HSV-1 using six concentrations (0.00001-1.0 multiplicity of infection [MOI]) on viability and two concentrations (0.001 and 0.1 MOI) on invasion of highly invasive metastatic HSC-3 and less invasive primary SCC-25 OTSCC cell lines using MTT and Myogel-coated Transwell invasion assays. Results: Altogether 321 oropharyngeal samples were diagnosed positive for HSV during the study period. HSV-1 was the predominant (97.8%) HSV type compared with HSV-2 (detected in 2.2% of samples). HSV-1 was also detected in 24% of the OTSCC samples and had no association with patient survival or recurrence. OTSCC cells were viable even after 6 days with low viral load (0.00001, 0.0001, 0.001 MOI) of HSV-1. In both cell lines, 0.001 MOI did not affect cell invasion. However, 0.1 MOI significantly reduced cell invasion in HSC-3 cells. Discussion: HSV-1 infection is predominant compared with HSV-2 in the oral cavity. HSV-1 is detected in OTSCC samples without clinical significance, and OTSCC cell survival or invasion was not affected at low doses of HSV-1.

No detection of TSH or TSHR in oral lichen planus lesions in patients with or without hypothyroidism.

Objective: An association between hypothyroidism (HT) and oral lichen planus (OLP) has been reported. However, the mechanisms that could explain this association remain unresolved. This study aimed to evaluate the expression of thyroid-stimulating hormone (TSH) and thyroid-stimulating hormone receptor (TSHR) in healthy oral mucosa and in OLP lesions of individuals with and without HT.Material and methods: Immunohistochemical expression of TSH and TSHR was studied in oral mucosal biopsies obtained from 14 OLP patients with HT, 14 OLP patients without HT and 10 healthy controls without oral mucosal lesions. Gene expression of TSHR was investigated by using three different PCR techniques in oral mucosal samples from 7 OLP patients with HT, 3 OLP patients without HT, 9 healthy controls and in cultured human oral epithelial cells. Gene expression of TSH was examined by employing 2 PCR techniques in oral mucosal samples from 2 OLP patients with HT, 2 OLP patients without HT and 4 healthy controls.Results: TSH and TSHR stainings were negative in the studied oral mucosal specimens. Gene quantification assays demonstrated negative gene expression of TSH and TSHR in clinical and in vitro samples.Conclusions: These results suggest that TSH and TSHR may not be commonly involved in the pathogenetic mechanism that could explain the association between OLP and hypothyroidism.

Role of the high mobility group box 1 signalling axes via the receptor for advanced glycation end-products and toll-like receptor-4 in the immunopathology of oral lichen planus: a potential drug target?

High mobility group box 1 (HMGB1) is an extremely conserved DNA-binding protein that stabilizes nucleosomes and facilitates gene transcription in mammalian cells. When released extracellularly, HMGB1 becomes an alarmin that can mediate systemic diseases. High mobility group box 1 signals via two main receptors: receptor for advanced glycation end-products (RAGE) and toll-like receptor-4 (TLR4). We hypothesized that HMGB1 expression is increased in patients with oral lichen planus (OLP) relative to healthy controls. Therefore, HMGB1 and its receptors were mapped in tissue biopsies from 25 patients with OLP and from 20 healthy controls by immunostaining and ImageJ analysis. High mobility group box 1 was induced in oral keratinocytes in all patients with OLP. The band-like cell infiltrate in patients with OLP revealed very strong staining for RAGE. Likewise, TLR4 was overexpressed throughout OLP mucosa which co-localized with HMGB1. In conclusion, we suggest that OLP could partly be an HMGB1-mediated condition by creating a proinflammatory loop cycle via RAGE- and TLR4-signalling axes, which may contribute to the chronicity of this disease.