Análise dos efeitos biológicos associados ao fator de choque térmico 1 (HSF1) no carcinoma de células escamosas oral

Abstract

Oral squamous cell carcinoma exhibits high rates of morbimortality and evidence in several tumor types shows that processes associated with initiation, progression and therapeutic resistance are regulated by HSF1. Therefore, to clarify the pathways of HSF1 participation in the oral cancer may help in the understanding of its biological behavior. In research previously developed by our group, a clinicopathological analysis and an immunoexpression study of HSF1 of 70 cases of oral tongue squamous cell carcinoma (OTSCC) were performed in comparison with 30 samples of the normal oral mucosa (NOM). In this current investigation, the role of HSF1 in OTSCC tumorigenesis was evaluated, through in vitro experiments with the SCC15 cell line, silenced and non-silenced, with silencing confirmed by qRT-PCR and Western Blot. Cell viability and proliferation (CellTiter and BrdU, respectively), influence on cell cycle (propidium iodide and flow cytometry analysis), invasion capacity (transwell / Matrigel system), and epithelial-mesenchymal (EMT) (expression of E-cadherin and vimentin by qRT-PCR) were evaluated. Our previous results showed that as for the cases of OTSCC, 57.1% exhibited clinical stage III or IV, 82.9% were graded as high grade according to Bryne (1998), 47.1% as high risk according to BrandweinGensler et al. (2005) and 58.8% as high risk according to the BD model. Bryne's gradation (1998) (p = 0.05) had an impact on disease-free survival. Tumor size T3 or T4 (p = 0.04), local recurrence (p = 0.02) and BD model (p = 0.02) impacted overall survival. A significant initial result (p <0.01) was found when comparing an HSF1 immunoexpression between NOM and OTSCC, with no significant association of immunoexpression with clinicopathological tests. From the functional studies, it was observed that HSF1 is overexpressed in the SCC15 cell line compared to immortalized keratinocytes (p <0.005) and that the silencing of this gene inhibited cell proliferation (p <0.005), advance in the cell cycle phases, with an increase in the number of cells in phases G0/G1 (p <0.01) and reduction of cells in phase S (p <0.001), invasion capacity (p <0.05) and EMT, with decreased vimentin expression (p <0.001) and increased E-cadherin (p <0.05), when compared to silenced and control lines. Given these results, it is suggested that HSF1 can exert a range of functions that maintain cell stability amid the stressful conditions of the tumor microenvironment. Thus, in the future, strategies involving its regulation may be a useful therapeutic tool in controlling the progress of the oral cancer.