Effect of ΔNp63β on cell cycle and apoptosis in T98G cells.

Background/aim: The p53 protein, a crucial tumor suppressor, governs cell cycle regulation and apoptosis. Similarly, p63, a member of the p53 family, exhibits traits of both tumor suppression and oncogenic behavior through its isoforms. However, the functional impact of ΔNp63β, an isoform of the p63 protein, on human glioma cancer cells like T98G cells remains poorly understood, representing the novelty of this study in the current literature.

Materials and methods: Employing the pRetroX-Tet-On vector system, the apoptotic effects of ΔNp63β on T98G cell lines was investigated and its influence on the cell cycle was assessed. Initially, an rtTA-expressing vector, a component of the pRetroX-Tet-On system, was established in the T98G cell lines. Subsequently, the ΔNp63β cDNA was cloned into the Retropur Tight retroviral vector and transfected into T98G cells containing the pRetroX-Tet-On system for functional analysis. The gene expression and cell cycle regulation were evaluated through reverse-transcription polymerase chain reaction and flow cytometry, determining protein translation via western blotting. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and β-galactosidase cell staining were employed to assess the cytotoxicity and senescence of ΔNp63β, respectively.

Results: The overexpression of ΔNp63β in the T98G cells correlated with increased cell viability and altered cell cycle regulation, notably upregulating the p21 expression independent of p53. Caspase-3/7 activity analyses showed no changes in the apoptotic genes but revealed an increase in antiapoptotic gene expression. Surprisingly, cell death in the ΔNp63β-overexpressing T98G cells did not occur through apoptosis as anticipated. Instead, it resulted from the cytotoxic effects of the ΔNp63β protein.

Conclusion: Δp63β increased the p21 levels, induced cell death, and caused cell cycle arrest at the G1 phase, while exhibiting antiapoptotic properties and promoting senescence. Unexpectedly, overexpression of Δp63β in T98G cells led to significant cell death, potentially through necrosis rather than apoptosis, suggesting a complex role for Δp63β in cell cycle regulation and tumor suppression.