In vitro evaluation of the suppressor potential of conditioned medium from benign myoepithelial cells from pleomorphic adenoma in malignant cell invasion

Cellular senescence and autophagy of myoepithelial cells are involved in the progression of in situ areas of carcinoma ex-pleomorphic adenoma to invasive carcinoma. An in vitro model

During tumor invasion, benign myoepithelial cells of carcinoma ex-pleomorphic adenoma (CXPA) surround malignant epithelial cells and disappear. The mechanisms involved in the death and disappearance of these myoepithelial cells were investigated via analysis of the expression of regulatory proteins for apoptosis, autophagy and cellular senescence in an in situ in vitro model. Protein expression relating to apoptosis (Bax, Bcl-2, Survivin), autophagy (Beclin-1, LC3B) and cellular senescence (p21, p16) was evaluated using indirect immunofluorescence. β-galactosidase expression was assessed via histochemistry. Biopsies of CXPA (ex vivo) allowed immunhistochemical evaluation of p21 and p16, whilst LC3B, p21 and p16 protein expression was analyzed by western blotting. In the in vitro model, the myoepithelial cells were positive for LC3B (cytoplasm) and p21 (nucleus), whilst in vivo positivity for p21 and p16 was observed. In vitro, β-galactosidase activity increased in the myoepithelial cells over time. Western blotting analysis revealed an increased LC3B, p16 and p21 expression in the myoepithelial cells with previous contact with the malignant cells when compared with those without contact. The investigation of behavior of benign myoepithelial cells in ductal areas of CXAP revealed that the myoepithelial cells are involved in the autophagy-senescence phenotype that subsequently leads to their disappearance.

The role of FGF-2/HGF and fibronectin matrix on pleomorphic adenoma myoepithelial cell morphology and immunophenotype: an in vitro study

Myoepithelial cells play a central role in glandular tumors, regulating the progression of in situ to invasive neoplasias, with the tumor microenvironment being shown to be involved in both initiation and progression. This study aimed to analyze the in vitro effects of fibroblast growth factor-2 (FGF-2) and hepatocyte growth factor (HGF) in myoepithelial cells under the influence of the fibronectin matrix extracellular protein. Benign myoepithelial cells were obtained from pleomorphic adenoma and cultured on a fibronectin substratum. FGF-2 and HGF were supplemented at different concentrations and time intervals, in order to evaluate cell proliferation, morphology and immunophenotype. Individually, FGF-2 and HGF supplementation did not alter myoepithelial cell proliferation, morphology or immunophenotype. The fibronectin substratum provoked an increase in cell proliferation and immunopositivity for α-smooth muscle actin and FGF-2. The myoepithelial cell morphology changed when the fibronectin substratum and FGF-2 acted together, highlighting the importance of the fibronectin extracellular matrix protein on the behavior of these cells.

Myoepithelial cells from pleomorphic adenoma are not influenced by tumor conditioned media from breast ductal adenocarcinoma and melanoma cells: An in vitro study

Myoepithelial cells have been implicated in the regulation of the transition from in situ to invasive neoplasia in salivary gland tumors. Considering the importance of the microenvironment of the tumor, the present in vitro study therefore analyzed the morphological and phenotypic changes undergone by benign myoepithelial cells from pleomorphic adenoma (PA) stimulated by tumor-conditioned medium. The benign myoepithelial cells were obtained from PA and were cultured with fibronectin extracellular matrix protein, supplemented with tumor-conditioned medium, which was harvested from breast ductal adenocarcinoma AU-565 and melanoma Hs 852.T cells. The morphological alterations were assessed by immunofluorescence analysis using vimentin antibody. The α-smooth muscle actin (α-SMA) and fibroblast growth factor (FGF)-2 proteins were analyzed by indirect immunofluorescence and quantitative polymerase chain reaction (qPCR). No morphological changes were observed in the myoepithelial cells cultured in fibronectin protein under stimulation from either tumor-conditioned medium. The immunofluorescence results, which were supported by qPCR analysis, revealed that only α-SMA was upregulated in the fibronectin substratum, with or without tumor-conditioned medium obtained from breast ductal adenocarcinoma and melanoma cells. No significant difference in FGF-2 mRNA expression was detected when the cells were cultured either in the tumor-conditioned medium or in the fibronectin substratum. The tumor-conditioned medium harvested from breast ductal adenocarcinoma and melanoma did not affect myoepithelial cell differentiation and function, which was reflected by the fact that there was no observed increase in α-SMA and FGF-2 expression, respectively.