Avaliação in vitro e in vivo dos efeitos de ácidos graxos de cadeia curta no câncer de mama

• Autor(a) principal: Muradás, Thaís Cristina
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Texto Completo: https://tede2.pucrs.br/tede2/handle/tede/10190
• topic: Câncer de Mama; Ácidos Graxos de Cadeia Curta; Cultivo Celular; Modelo de Câncer de Mama Murino 4T1; Metástases; Camundongos; Cell Culture; Mouse 4T1 Breast Tumor Model; Metastasis; Mice; Breast Cancer; Short-Chain Fatty Acids; CIENCIAS DA SAUDE::MEDICINA

Breast cancer has the highest worldwide incidence of all types of tumors. Treatments are defined according to molecular subtypes: luminal A and B, HER2+, and triple-negative. Despite the success rates for hormonal and HER2+ types, patients who relapse for the most aggressive or triple-negative tumors remain with low overall survival and the prognosis is poor due, for example, to the absence of a therapeutic target or high aggressiveness. Furthermore, alterations in the microbiota composition, consequently, in short-chain fatty acids (SCFA) – through baseline clinical conditions or side effects of treatments – might affect the risk and prognosis for breast cancer. In this sense, this study evaluated the effects of SCFA in different models of breast cancer to identify a new approach for the treatment of these tumors. In vitro assays using breast cancer cell lines of different molecular subtypes, human (MCF-7, SK-BR-3, and MDA-MB-231) or murine (4T1) exhibited contrasting effects after treatments with SCFA. In the analysis of cell viability, acetate showed positive effects at concentrations above 100 mM. While propionate demonstrated a dual concentration-dependent effect. In a time and concentration-dependent manner, butyrate, propionate, and valerate significantly reduced the cell viability of human cells, and valerate reduced the viability of the murine cells under an IC50 of 9.6 mM in 48 h. On the other hand, selective FFA2 and FFA3 agonists 4-CMTB and AR420626, respectively, modestly reduced cell viability only of the more aggressive MDA-MB-231 and 4T1 cell lines. As in the evaluation of the FFA2 and FFA3 antagonists CATPB and βhydroxybutyrate, respectively, only CATPB produced inhibitory effects in the 4T1 cells. These data suggest that SCFA have antitumor effects in breast cancer, probably through FFA2 and FFA3 receptor independent mechanisms. From this screening, SCFAs with best inhibitory effects, butyrate, propionate, and valerate, were selected to investigate their effects on the malignancy capacity of MDAMB-231 and 4T1 cells. Several changes in cell morphology were observed, as well as a reduction in the new colonies formation. In the evaluation of cell adhesion, valerate reduced this parameter in the MDA-MB-231 cells, however, it increased about the 4T1 cells. Regarding the evaluation of cell migration, only the treatment with butyrate (10 mM) prevented the migration of the 4T1 cells within 24 h. Although discreet, these results corroborate the antitumor effects observed in the reduction of colony formation and changes in cell morphology after exposure with butyrate in the 4T1 cells, mainly. To investigate the effects of these SCFAs on tumor progression, was used the orthotopic model of metastatic breast cancer in female Balb/CJ mice induced by inoculation of 4T1 cells. The preliminary results of oral administration of SCFA in both the therapeutic and preventive protocols did not demonstrate a mirror effect according to the in vitro evaluation, except for the number of lung metastases that were significantly reduced by butyrate (600 mg/kg) in the therapeutic scheme. These evidence suggests that the participation of the tumor microenvironment is involved in the action of SCFA, as well as their cellular effects can be modulated by alternative mechanisms to the FFA2 and FFA3 receptors, such as the HDACs inhibition. Therefore, to establish a promising treatment, the definition of these mechanisms might contribute to the determination of SCFA as a therapeutic target in the management of breast cancer.