Leucoplasias orais com e sem transformação maligna são metabolicamente diferentes

Abstract

Oral squamous cell carcinoma is the main type of oral cancer and is also one of the most common malignancies worldwide, accounting for high morbidity and mortality rates. Some oral cancer cases are preceded by mucosal lesions called oral potentially malignant disorders. Oral leukoplakia is the most frequent oral potentially malignant disorder. Therefore, several studies have been performed to elucidate the mechanisms that underlie the lesion's malignant transformation. However, the biological events that promote the malignant progression of oral leukoplakia are still poorly understood. An altered metabolomic profile between samples of oral leukoplakia, oral cancer, and healthy controls was previously reported. However, no metabolomic study has compared transformed and non-transformed oral leukoplakia samples. Therefore, in the present study we aimed to identify the metabolic alterations at the early stages of the oral carcinogenesis process throughout untargeted metabolomic analysis of 5 transformed and 15 non-transformed oral leukoplakias. Samples were obtained from a retrospective collection of tissue blocks fixed in formalin and embedded in paraffin. Tissue blocks were cut, dewaxed and metabolites were extracted using methanol, chloroform and water solution. Then, the extracts were analyzed using high-performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (HPLC-QToF-MS). After pre-processing and pre-treatment of data acquired by HPLC-QToF-MS, univariate and multivariate statistical analysis methods were combined to detect discriminant compounds between groups. The enrichment analysis was performed through the association between the mummichog and GSEA algorithms for the prediction of enriched biological pathways in the samples of oral leukoplakia. Seventeen discriminant compounds were correspondingly detected in all applied statistical methods. The unsupervised hierarchical clustering revealed the potential of these compounds to distinguish the study groups. Enriched metabolic pathways were mostly related to lipid metabolism, synthesis of pro-inflammatory molecules, retinoic acid, and vitamin E metabolism, which are carcinogenesis-related processes. For the first time in the literature, the present study revealed the potential of untargeted metabolomics to distinguish malignantly transformed from untransformed oral leukoplakia. Additionally, we shed light on the metabolic pathways behind oral carcinogenesis.