Abstract 1226: p53 signaling pathway acts as rescue mechanism to β1 integrin silencing in head and neck cancer cell line

Abstract

Abstract β1 integrin's aberrant expression has implicated a cancer progression and resistance to cytotoxic therapy. Moreover, cancer cells gained epithelial mesenchymal transition (EMT) features were more resistant to the detachment-induced cell death. In this regard, we investigated the mechanism by which β1-Integrin governs cell viability and verified whether the signaling pathway is associated with EMT features. Cancer cell lines from head and neck cancer patients (AMC-HN3 and AMC-HN9) and well-known EMT cancer, MDA-MB231, were used in this study. To determine whether three cell lines reveal the epithelial EMT features, EMT markers such as Snail, vimentin, fibronectin and E-cadherin were evaluated by western blot analysis and immunofluroscence. To knockdown β1 integrin signal, β1 integrin small interfering RNA (siRNA) was transiently transfected into all cell lines. The cell viability was examined by looking at the results of propidium iodide staining, MTT assay, changes in the mitochondrial membrane potential and cell morphology. MDA-MB231 and AMC-HN9 cells possessed EMT features whereas AMC-HN3 cells were not shown EMT phenotype. β1 integrin silencing cell increased the sub G1 from 1.0% to 29.8%, increased the percentage of cells losing their mitochondrial membrane potential from 5.3% to 65.9% as well as the number of fragmented mitochondria in AMC-HN3 cells. In contrast, MDA-MB231 cells showed more resistance to silencing of β1 integrin, lower cell death rate from 0.6% to 9.6% and less changes in the mitochondrial membrane potential from 4.34% to 34.51%. Interestingly, AMC-HN9 cells showed complete resistance to β1 integrin blocking even though FAK phosphorylation signaling was blocked in AMC-HN9 cells, same as AMC-HN3 cells, which is a different response from typical EMT featured cells. When AMC-HN9 cells were treated to inhibit β1 integrin and p53 separately, it showed no response to changes in the cellular morphology, viability and apoptosis-related signal pathway; however, when it was given the combined β1 integrin and p53, apoptosis occurred in the cell line. In this study, acquisition of the EMT features in cancer cells presented resistance to the β1 integrin inhibition. In addition, the activation of p53-p21 signaling pathway provided resistance to detachment-induced apoptosis in head and neck cancer cell line with EMT features. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1226. doi:10.1158/1538-7445.AM2011-1226