Detecting Early Signs of Malignancy of Oral Leukoplakia in its Tissues and Saliva. Summary of the Doctoral Thesis
Authors:   ,   Rīga Stradiņš University, Dzudzilo Madara 
Published: December 2024

Oral leukoplakia (OL) is one of the most common potentially malignant oral diseases observed in about 3.41–11.74 % of the population, however not all leukoplakias turn into carcinoma. The most common causes of oral malignancies are smoking, alcohol consumption, and HPV infection. In recent years, more and more smokeless tobacco has been used in Latvia, which can also be a reason for the development of pre-cancer and oral carcinoma. Evaluation of epithelial dysplasia is considered as the “gold standard” for the detection of the risk of malignant transformation. Complex immunohistochemical, electron microscopic, genetic, and immunological investigations are necessary for deeper understanding the complicated process of malignisation in the oral mucosa. In our study there are combined clinical, laboratory and immunohistochemical examinations of oral leucoplakias. We have analysed the epithelial cycle regulator p27, transcriptional protein ThPOK, as well as antigens of stem cell membranes CD44 and exosomes CD9. The aim of the study was to evaluate the clinical, morphological and immunohistochemical changes of different types of oral leukoplakia simultaneously with saliva test indicators to determine early signs of malignant transformation oral leukoplakia. The study included 50 oral leukoplakia patients and 2 comparative groups – 20 patients with oral squamous cell carcinoma and 20 persons with healthy oral mucosa. All patients underwent VELscope imaging, as well as determination of soluble CD44 and total protein in saliva. Morphological assessment was performed on healthy tissue, OL and squamous cell carcinoma tissue. CD44, CD9, ThPOK and p27 proteins were evaluated by the standard polymer-based visualisation En-vision method. To evaluate the obtained results, statistical data analysis was performed using GraphPadPrism 9.0 software for MacOS (GraphPad Software, San Diego, CA, USA). For all statistical tests, p values < 0.05 were considered significant. Results are presented as median with interquartile range. We concluded that in our study group, OL was more often observed in men with an average age of 57 years. The mean OL size was 14 ± 3.7 mm and the most frequent localisation was the mucous membrane of the cheeks and the side of the tongue, 26 % of all OL cases had severe dysplasia. VELscope fluorescent spectroscopy provided an opportunity to evaluate and determine the borders of the altered tissue in both OL and carcinoma cases, thereby clarifying the determination of the biopsy site and resection lines. As the severity of the clinical form of oral leukoplakia increases, the increase in salivary total protein level in combination with a positive soluble CD44 test was detected and it indicates about early changes in the epithelial microenvironment. Our study demonstrated the expression of the adhesion molecule CD44 in both hyperplastic and dysplastic areas of OL, as well as in carcinomas. The presence of CD44 antigen in the macrophages of the oral submucosa proved its participation of a hyaluronic receptor protein in epithelial-mesenchymal activities. The expression of CD9 glycoprotein in exosomes demonstrated the so-called transport proteins in the oral epithelium and helped to understand the transport of saliva and other fluids in the healthy mucosa and its pathological lesions. p27 protein showed suppressor and oncogene features in non-homogeneous OL and oral squamous cell carcinoma, demonstrating the dual properties of this antigen with nuclear-to-cytoplasmic translocalisation of p27. The great variety of expression of ThPOK in oral leukoplakias and cancers determines that we cannot recommend this biomarker in the study of malignancy processes of oral leukoplakias. Thick leukoplakia with severe dysplasia, translocation of CD44, CD9 and p27 proteins and elevated numbers of soluble CD44 and total protein in saliva characterize non-homogeneous oral leukoplakia as a high-risk potentially malignant formation in the oral cavity.
The Doctoral Thesis has been developed with financing from the European Social Fund and Latvian state budget within the project No 8.2.2.0/20/I/004 “Support for involving doctoral students in scientific research and studies” at Rīga Stradiņš University.
The Doctoral Thesis was developed at Rīga Stradiņš University, Latvia Defence: at the public session of the Promotion Council of Clinical Medicine on 2 December 2024 at 13.30 in the Hippocrates Lecture Theatre, 16 Dzirciema Street, Rīga Stradiņš University and remotely via online platform Zoom.
3.2 Clinical Medicine; Sub-Sector – Dentistry.
Keywords: oral leukoplakia; VELscope; SolCD44; CD44; CD9; ThPOK; p27 antigenes.