Background & objective: Patients suffered from advanced endometrial cancer have poor prognosis. The five-year survival is only 25%. Histone deacetylase inhibitors have shown promise in the treatment for a variety of malignancies. In combination with traditional cytotoxic chemotherapy, histone deacetylase inhibitors can enhance the survival rate of cancer patients. This study was to investigate the effect and mechanism of trichostatin A (TSA), a histone deacetylase inhibitor, combined with paclitaxel (PTX) on the apoptosis of human endometrial carcinoma cell line Ark2.
Methods: Ark2 cells were cultured in RPMI-1640 and treated with PTX alone, TSA alone or the two drugs in combination. Cell apoptosis was detected using Annexin V and Hoechst staining; perturbation of mitochondrial membrane potential was detected using MitoTracker red Poly (ADP-ribose) polymerase; caspase-9 degradation products and tubulin acetylation were detected by Western blot.
Results: Results of Annexin V showed that PTX (1.5 nmol/L) plus TSA (25 nmol/L) induced a significantly higher apoptotic rate (45.2%) than PTX alone (14.1%) or TSA alone (11.2%) did in Ark2 cells after drug treatment for three days. The results of Hoechst staining and Annexin V were consistent. A loss of mitochondrial membrane potential could activate the apoptotic cascade. Cleavages of PARP and caspase-9 were significantly apparent in PTX plus TSA group than in PTX group or TSA group (P<0.05). PTX and TSA could induce tubulin acetylation. PTX in combination with TSA increased acetylated tublins and microtubule stability compared with either drug alone. The loss of mitochondrial membrane potential was more dramatic in the drug combination group than the single drug group. The effects of TSA and PTX were synergistic (q=2.54).
Conclusion: TSA and PTX could induce apoptosis of Ark2 cells, which may be through the loss of mitochondrial membrane potential and acetylation of non-histone proteins induced by histone deacetylase inhibitors.