Potencial oncogênico da via de sinalização da leptina no carcinoma epidermoide de boca e estratégia de modulação pelo ácido gálico: Análise bioinformática e funcional

Abstract

Leptin (Lep), a hormone related to energetic metabolism, can be involved in the development of different types of neoplasias, favoring angiogenesis and metastasis. Despite efforts to better understand the molecular mechanisms associated with oral squamous cell carcinoma (OSCC), there is no precise knowledge about the role of Lep in the pathogenesis of the disease. Therefore, it is necessary to investigate a possible involvement of Lep in oral carcinogenesis. A substantial interest in the therapeutic potential of substances derived from Brazilian plants has directed research about antineoplastics agents. Gallic acid (GA), a polyphenol widely found in fruits and plants, has demonstrated its antineoplastic potential in several types of cancers. However, in oral carcinogenesis, the effect of GA on neoplastic cells is not well understood. Thus, this study aims to investigate, through a bioinformatic approach and functional assays, the neoplastic potential of components of the leptin pathway in OSCC, as well as a strategy of modulation of leptin by GA. Three study approaches were outlined. In the first approach, through systematic literature review and bioinformatics analysis, we investigated the initial hypothesis that Lep is a key molecule linking genes associated with obesity and oral cancer. The analyses revealed a genes network involved in the two pathological processes. In addition, the analysis display interactions of Lep with p53 protein through CREBBP and EP300 and HIF-1α proteins, being able to favor angiogenesis. Based on these evidences, we investigated a second work approach, through in vitro and in vivo assays, to verify whether Lep can affect the neoplastic behavior of OSCC, as well as the expression of genes and proteins possibly linked to the Lep pathway. In the immortalized cell lines of OSCC, SCC4 and SCC9 cells treated with recombinant Lep, the effect of Lep on the proliferation, migration and invasion phenotype of the neoplastic cells was investigated, as well as the analysis of Lep, LepR, HIF-1α, E-cadherin, MMP2, MMP9, Col1A1, Ki67 and mir-210, through qPCR. Gene expression and immunohistochemical analysis of Lep and LepR were also quantified in human biological samples associated with clinical-pathological parameters. Lep treatment favored cell proliferation and migration and decreased apoptosis. Accordingly, Leptreated OSCC cells exhibited decreased expression of caspase-3 mRNA and increased levels of Ecadherin, Col1A1, MMP2, MMP9 and mir210. In tissue samples, the expression of HIF-1α mRNA and Lep and LepR protein were higher in OSCC cases. Serum levels of Lep were increased in the early clinical stages of the disease. In the animal model, mice with induced OSCC had a higher expression of LepR and the level of serum Lep increased in the group of dysplasia. In the third approach of the study, based in the bioinformatic simulations of molecular interactions between GA, Lep and LepR, we explored the hypothesis that GA interacts with components of the Lep signaling pathway, interfering with the neoplastic phenotype of OSCC cells. The effect of GA on the secretion of Lep by OSCC cells, as well as the underlying molecular mechanisms, was also evaluated. GA decreased the proliferation and migration of Lep-treated OSCC cells and reduced expression of mRNA of MMP2, MMP9, Col1A1, mir210, but did not alter HIF-1α. GA decreased levels of Lep secreted by OSCC cells in accordance with the downregulation of p44 / 42 MAPK expression. The findings suggest that Lep seems to exert an effect on the behavior of OSCC cells, as well as on molecular markers related to cell proliferation, migration and tumor angiogenesis. GA seems to inhibit the neoplastic phenotype of OSCC cells by interfering with the Lep pathway. Despite the need for further functional studies on the effect of GA on OSCC, this study highlights GA as a promising compound with the antineoplastic effect on OSCC cells and points to the Lep signaling pathway as a possible target for GA action.