Ti_0.8O₂Nanosheets Inhibit Lung Cancer Stem Cells by Inducing Production of Superoxide Anion

Abstract

Recent research into the cancer stem cell (CSC) concept has driven progress in the understanding of cancer biology and has revealed promising CSC-specific targets for drug discovery efforts. As malignancies of lung cancer have been shown to be strongly associated with activities of CSCs, we examined the effects of Ti 0.8 O 2 nanosheets on these cells. Here we show that the nanosheets target lung CSCs but not normal primary dermal papilla (DP) stem cells. Whereas Ti 0.8 O 2 caused a dramatic apoptosis along with a decrease in CSC phenotypes, in primary human DP cells such effects of nanosheets have been minimal. Nanosheets reduced the ability of lung cancer cells to generate three-dimensional tumor spheroids, lung CSC markers (CD133 and ALDH1A1), and CSC transcription factors (Nanog and Oct-4). Ti 0.8 O 2 nanosheets reduced CSC signaling through mechanisms involving suppression of protein kinase B (AKT) and Notch-1 pathways. In addition, the nanosheets inhibited the migration and invasive activities of lung cancer cells and reduced epithelial-to-mesenchymal transition (EMT) markers as N-cadherin, vimentin, and Slug, as well as metastasis-related integrins (integrin-av and integrin-b1). Importantly, we found that the selectivity of the Ti 0.8 O 2 nanosheets in targeting cancer cells was mediated by induction of cellular superoxide anion in cancerous but not normal cells. Inhibition of nanosheet-induced superoxide anion restored the suppression of CSC and EMT in cancer cells. These findings demonstrate a promising distinctive effect of Ti 0.8 O 2 nanosheets on lung CSC that may lead to opportunities to use such a nanomaterial in cancer therapy.

Titania Nanosheets Generates Peroxynitrite for S-Nitrosylation and Enhanced p53 Function in Lung Cancer Cells

“…4). In addition, we have provided supportive information explaining that the cancer cell selectivity of Ti0.8O2 nanosheets may be caused through the generation of superoxide anions, like in a previous study [20].…”

“…Japan To determine proteins regulation in apoptosis pathway, the treated cells (H460 and A549) were lysed into cellular lysates as previous described [20] Then, the blots were washed in TBST and incubated with horseradish peroxidase (HRP)-conjugated secondary antibodies for 2 hours at room temperature.…”

“…Nanosheets are a developing class of nanomaterial that are highly anisotropic and flexible [19]. Moreover, Ti0.8O2 nanosheets have also been found to induce superoxide anions in cancer without harming normal dermal papilla cells [20]. However, to the best of our knowledge, the nanotoxicity and mechanism of Ti0.8O2 nanosheets for specific site-targeting strategies in NSCLC have not yet been investigated.…”

Titania Nanosheet Generates Peroxynitrite-Dependent S-Nitrosylation and Enhances p53 Function in Lung Cancer Cells

“…Equal amounts of protein from each sample were subjected to SDS-PAGE for separation and transferred to nitrocellulose or PVDF membranes (Bio-Rad, Hercules, CA, USA). The blots were blocked for 1 h. with 5% non-fat dry milk [ 20 ] and, after that, incubated with specific primary antibodies against p-p53 (Ser15), p53, Bcl-2, Mcl-1, Bax, caspase 3, and β-actin at 4 °C overnight. Then, the blots were washed in TBST and incubated with horseradish peroxidase (HRP)-conjugated secondary antibodies for 2 h at room temperature.…”

“…Nanosheets are a developing class of nanomaterial that are highly anisotropic and flexible [ 19 ]. Ti 0.8 O 2 nanosheets are the two-dimensionality (2D) analog of TiO 2 with potential anti-cancer stem cell activity [ 20 ]. However, to the best of our knowledge, the nanotoxicity and mechanism of Ti 0 .8 O 2 nanosheets for specific site-targeting strategies in NSCLC have not yet been investigated.…”