Molecular Insights in Oral Leukoplakia: Epigenetic, Immunological and Proteomic Perspectives.

Abstract

Oral leukoplakia, a potentially malignant oral disorder, with a risk of transformation into oral squamous cell carcinoma (OSCC). This thesis investigates the molecular, immunological, and proteomic alterations in leukoplakia, aiming to identify early cancer transformation markers. Study I examined the expression of the epigenetic regulator EZH2 in leukoplakia. Increased nuclear EZH2 expression in transforming leukoplakia, correlated directly with CD3 positive- and CD8 positive T-cell infiltration in the epithelium, suggesting an immune response and epithelial dysregulation. Study II explored the localization and expression of Toll-like receptors (TLR3, TLR7, TLR8, TLR9) in leukoplakia. Nuclear translocation of TLR7 was significantly associated with dysplasia, while reduced cytoplasmic expression of TLR8 and TLR9 might play a role in immune dysregulation during transformation. Study III assessed the expression of intracellular TLRs in oral epithelial cell lines (DOK, CaLH3, SCC25). TLR3 and TLR9 expression were inducible in DOK and CaLH3 but absent in SCC25. Stimulation with TLR agonists led to downregulation of TRIF. The TLR7 agonist imiquimod inhibited DOK cell proliferation, suggesting its therapeutic potential in early-stage oral lesions. Study IV employed proteomic profiling of leukoplakia not transforming and transforming to OSCC and OSCC tissues. Proteins related to cytoplasmic trafficking, matrix remodeling, and immune pathways were differentially expressed during progression from leukoplakia to OSCC. Notably, nuclear expression of EEF1D and cytoplasmic expression of Perlecan was evident in OSCC, suggesting subcellular shifts might be responsible for transformation. Collectively, these studies highlight epigenetic reprogramming, immune modulation, and proteomic remodeling from leukoplakia that progress into OSCC. In the future, integrating transcriptomic, proteomic, and spatial analyses may enable early detection, enhance diagnostic and treatment precision in patients with leukoplakia.