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Chitosan is an amino polysaccharide with possible biomedical applications, for example, in bandage materials or as an antibacterial agent or a cytotoxic agent for tumor and cancer cells. In this study, the cytotoxic effect of chitosan (CTSN-P) on MCF-7 breast cancer cells was monitored in a nondestructive and real-time manner by electrical cell-substrate impedance sensing with a fabricated multidisc indium tin oxide electrode array. The electrical impedance characteristics of cell growth on the multidisc electrode were analyzed by equivalent electric circuit modeling. Application of CTSN-P caused deterioration of viability of cells on the electrode substrate and yielded a CTSN-P concentration-dependent decrease in impedance. The 50% cytotoxicity concentrations in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and impedimetric assay were 1266.60 and 543.17 μg/mL, respectively. Thus, impedance measurement is suitable for detecting low-dose effects of CTSN-P on the behavior or morphology of live cells.

The mechanisms through which cancer-upregulated gene 2 (CUG2), a novel oncogene, affects Wnt/β-catenin signaling, essential for tumorigenesis, are unclear. In this study, we aimed to elucidate some of these mechanisms in A549 lung cancer cells. Under the overexpression of CUG2, the protein levels and activity of β-catenin were evaluated by western blot analysis and luciferase assay. To examine a biological consequence of β-catenin under CUG2 overexpression, cell migration, invasion and sphere formation assay were performed. The upregulation of β-catenin induced by CUG2 overexpression was also accessed by xenotransplantation in mice. We first found that CUG2 overexpression increased β-catenin expression and activity. The suppression of β-catenin decreased cancer stem cell (CSC)-like phenotypes, indicating that β-catenin is involved in CUG2-mediated CSC-like phenotypes. Notably, CUG2 overexpression increased the phosphorylation of β-catenin at Ser33/Ser37, which is known to recruit E3 ligase for β-catenin degradation. Moreover, CUG2 interacted with and enhanced the expression and kinase activity of never in mitosis gene A-related kinase 2 (NEK2). Recombinant NEK2 phosphorylated β-catenin at Ser33/Ser37, while NEK2 knockdown decreased the phosphorylation of β-catenin, suggesting that NEK2 is involved in the phosphorylation of β-catenin at Ser33/Ser37. Treatment with CGK062, a small chemical molecule, which promotes the phosphorylation of β-catenin at Ser33/Ser37 through protein kinase C (PKC)α to induce its degradation, reduced β-catenin levels and inhibited the CUG2-induced features of malignant tumors, including increased cell migration, invasion and sphere formation. Furthermore, CGK062 treatment suppressed CUG2-mediated tumor formation in nude mice. Taken together, the findings of this study suggest that CUG2 enhances the phosphorylation of β-catenin at Ser33/Ser37 by activating NEK2, thus stabilizing β-catenin. CGK062 may thus have potential for use as a therapeutic drug against CUG2-overexpressing lung cancer cells.

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