An Effective Concentration of 5-Aza-CdR to Induce Cell Death and Apoptosis in Human Pancreatic Cancer Cell Line through Reactivating RASSF1A and Up-Regulation of Bax Genes

Abstract

Background: Promoter hyper-methylation of tumor suppressor genes is a common event that occurs in cancer. As methylation is a reversible modification, agents capable of reversing an abnormal methylation status should help to combat cancer. 5-Aza-CdR is a DNA methyl-transferase inhibitor. The present study aimed to evaluate the effect of 5-Aza-CdR on the proliferation of human pancreatic cancer cell line (PANC-1) and the expression of RASSF1A and Bax genes. Methods: PANC-1 cells were cultured and treated with 5 and 10 mu M/L of 5-Aza-CdR for 24, 48, 72, and 96 hours and the percentages of cell viability and apoptosis were measured by MTT and flow cytometry. RASSF1A gene promoter methylation was assessed by methyl-specific primer-PCR (MSP-PCR) and the expression of RASSF1A and Bax genes was measured using quantitative real-time PCR (qPCR). All quantitative data are presented as mean +/- SD (standard deviation). The one-way analysis of variance (ANOVA) with the LSD post hoc test was performed for statistical analysis using the SPSS software package, version 16.0. Results: 3-4,5-dimethythiaziazol-2yl-2,5-diphenyl tetrazoliumbr omide (MTT) assay revealed that 5-Aza-CdR significantly inhibit the growth and proliferation of PANC-1. The flow cytometry results showed over 40% and 70% of early and late apoptotic cells after treatment with 5 and 10 mu m/L of 5-Aza-CdR, respectively. MSP-PCR data indicated that the treatment of cells with 10 mu m/L 5-AzaCdR resulted in partial demethylation of RASSF1A gene promoter. qPCR results showed significant re-expression of RASSF1A and up-regulation of Bax genes after 96 hours treatment of cells with 10 mu m/L 5-Aza-CdR versus control cells (P<0.01). Conclusion: The result demonstrated that 5 and 10 mu M of 5-AzaCdR induce cell death and apoptosis by epigenetic reactivation of RASSF1A and up-regulation of Bax genes.