Cyclin D1-induced proliferation is independent of beta-catenin in head and neck cancer.

OBJECTIVE: Head and neck squamous cell carcinoma (HNSCC) progression and metastasis have previously been associated with the activation of phosphatidylinositol 3-kinase-protein kinase B (PI3K-Akt) and Wnt signalling pathways, which lead to the activation of pro-proliferative genes, such as cyclin D1. The current study aims to investigate whether there is a crosstalk between these pathways in HNSCC and which pathway is more likely to regulate cyclin D1. MATERIAL AND METHODS: Two HNSCC and a control keratinocyte cell lines were treated with EGF and wortmannin to respectively activate and block the PI3K-Akt and Wnt pathways. Partial and total levels of cyclin D1, beta-catenin and Akt were evaluated by Western blotting and immunofluorescence. Twenty-four paraffin-embedded samples of human HNSCC, as well as normal oral mucosa biopsies, were also immunohistochemically evaluated for beta-catenin and cyclin D1 expression. RESULTS: Following both treatments, change in cyclin D1 protein was correlated with Akt levels only. Cytoplasmic staining for beta-catenin and loss of its membranous expression in the HNSCC invasive areas were found in 92% of the HNSCC biopsies. CONCLUSION: Taken together, we show that the change in cyclin D1 levels is more likely to be due to the EGFR-Akt pathway activation than due to beta-catenin nuclear translocation.

Brefeldin-A induces apoptosis in human adenoid cystic carcinoma cultured cells.

Adenoid cystic carcinoma (ACC) of salivary glands is characterized by a high rate of local recurrences, neurotropism and metastasis. ACC long-term survival rate is not promising. Thus, different chemotherapeutical approaches had been proposed for this neoplasm, including apoptosis induction by different drugs. This work evaluates the efficacy of Brefeldin-A (BFA), a potent apoptosis inducer, on ACC cultured cells (CAC2 cell line). CAC2 cells were treated with a 375 microM BFA solution in serum-free medium during 18 h. CAC2 cells grown in DMEM supplemented with 10% fetal bovine serum served as controls. Apoptotic cell recognition and counting were carried out through Hoechst staining. Transmission electron microscopy and immunofluorescence assessed the effect of BFA on CAC2 cells phenotype. Treated cultures showed a high apoptotic index presenting +/-30% of cells in evident apoptosis, when compared to controls. Apoptotic CAC2 cells also exhibited different alterations such as cytoplasmic vesicles formation and mitochondrial changes. Cultured ACC cells are strongly susceptible to apoptosis induction under BFA treatment, which may constitute a promising tool in further chemotherapeutical approaches.