Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Introduction: Oral lichen planus is a chronic inflammatory condition affecting the mucous membranes of the oral cavity. While its exact cause remains unclear, recent studies suggest a link between dysbiotic oral bacteria and other oral diseases, including periodontal disease and oral squamous cell carcinoma (OSCC). As such, we hypothesized that a unique oral bacterial microbiome may be associated with oral tumors arising in the context of oral lichen planus. In this study, we aimed to profile intratumoral bacteria in OSCC patients with a history of oral lichen planus.
Methods: 29 patients with OSCC and a history of oral lichen planus were identified from an institutional database. A head and neck pathologist confirmed lichenoid lesions, invasive malignant cancer and adjacent normal tissues. DNA was extracted, followed by 16S rRNA gene sequencing and qPCR (Zymobiomics Inc.). Using established computational pipelines, we analyzed bacterial composition and total abundance, correlating findings with clinicopathologic characteristics.
Results: The majority of patients were white (93%), 83% were female, 45% were never smokers, and the mean age was 69 ± 12. The most common tumor subsite was the oral tongue (52%) followed by the alveolar ridge (14%), with most patients presenting with stage I-II disease (69%). The top 5 genera identified in tumor tissue were: Prevotella, Fusobacterium, Corynebacterium, Haemophilus, and Alloprevotella. The top 5 genera identified in lichenoid biopsy lesions were Haemophilus, Streptococcus, Lachnospiraceae, Bacteroidales, and Leptotrichia. Tumor tissue showed a significantly higher bacterial load (mean 89,554 gene copies/μL vs. 8,046 in adjacent normal tissue). Additionally, tumor tissue displayed an increased abundance of Bacteroidetes compared to adjacent normal tissue. However, alpha and beta diversity did not significantly differ between tumor and normal samples.
Discussion: This study provides the first characterization of the intratumoral bacterial microbiome in OSCC associated with lichen planus. Similar genera were identified in the lichen planus cohort that are often found in smoking-related OSCC (e.g. Fusobacterium, Prevotella and Corynebacterium), while lichen planus biopsies had a distinct microbial composition. Significant differences in bacterial load between cancerous and adjacent normal tissues was also observed. Further research into the bacterial community interactions in this unique population may provide additional insight into carcinogenesis and disease progression.