Abstract 684: Trifluoperazine modulates DNA damage-induced cell death in human lung cancer cells through inhibition of DNA repair, cell cycle delays, and augmentation of pro-apoptotic signaling

Abstract

Abstract Trifluoperazine modulates DNA damage-induced cell death in human lung cancer cells through inhibition of DNA repair, cell cycle delays, and augmentation of pro-apoptotic signaling Resistance of human tumors to DNA damaging chemotherapy poses severe limitations to the efficacy of current available treatment. Small molecule compounds of the phenothiazine class, such as trifluoperazine (TFP), have documented chemosensitizing activities. We exposed human non-small cell lung cancer (NSCLC) cell lines to the DNA damaging drug bleomycin in the presence or absence of TFP, and studied potential differences with regard to DNA repair and cell death signaling. A colony formation assay showed that TFP significantly enhanced the cytotoxic potential of bleomycin, at doses achievable clinically. Bleomycin treatment resulted in a reversible arrest at the G2-M phase of the cell cycle. Notably, TFP delayed the repair of bleomycin-induced DNA double strand breaks (DSBs), causing higher residual levels of γH2AX 24 h after treatment. Despite the presence of unrepaired DNA DSBs, cells co-treated with bleomycin and TFP overcame the G2-M checkpoint arrest, as evidenced by the reappearance of the mitosis marker histone H3 phospho-Ser10 and reduction in CFSE fluorescence. This process, which is reminiscent of checkpoint adaptation, was associated with increased micronucleation and secondary arrest in G2-M phase during subsequent rounds of the cell cycle. Furthermore, the onset of secondary checkpoint arrest in cells co-treated with bleomycin and TFP coincided with the activation of pro-apoptotic Bak and Bax, and was followed by activation of caspase-3, which occurred preferentially in cells in the G2-M phase. In conclusion, we demonstrate here that the chemosensitizing effect of TFP in NSCLC cells involves interference with DNA DSBs repair, resulting in secondary G-M checkpoint arrest after initial checkpoint adaptation, and concomitant increases in pro-apoptotic signaling. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 684.