Effect Of Histone Deacetylase Inhibitor Trichostatin Research Articles

Sequence-Dependent Radiosensitization of Histone Deacetylase Inhibitors Trichostatin A and SK-7041

PurposeThis preclinical study is to determine whether the capacity of histone deacetylase (HDAC) inhibitors to enhance radiation response depends on temporal sequences of HDAC inhibition and irradiation.Materials and MethodsThe effects of HDAC inhibitors trichostatin A (TSA) and SK-7041 on radiosensitivity in human lung cancer cells were examined using a clonogenic assay, exposing cells to HDAC inhibitors in various sequences of HDAC inhibition and radiation. We performed Western blot of acetylated histone H3 and flow cytometry to analyze cell cycle phase distribution.ResultsTSA and SK-7041 augmented radiation cell lethality in an exposure time-dependent manner when delivered before irradiation. The impact of TSA and SK-7041 on radiosensitivity rapidly diminished when HDAC inhibition was delayed after irradiation. Radiation induced the acetylation of histone H3 in cells exposed to TSA, while irradiation alone had no effect on the expression of acetylated histone H3 in TSA-naïve cells. Preirradiation exposure to TSA abrogated radiation-induced G2/M-phase arrest. When delivered after irradiation, TSA had no effect on the peak of radiation-induced G2/M-phase arrest.ConclusionTSA and SK-7041 enhances radiosensitivity only when delivered before irradiation. Unless proven otherwise, it seems prudent to apply scheduling including preirradiation HDAC inhibition so that maximal radiosensitization is obtained.

Synergistic cytotoxicity effect of histone deacetylase inhibitor combined with paclitaxel on lung cancer cell lines and its mechanism

Histone deacetylase (HDAC) inhibitors can inhibit cell signal network function through decreasing expression of multiple genes and proteins, thus affect cell proliferation, survival and chemosensitivity. HDAC inhibitors combined with paclitaxel may enhance the inhibitory effect of drugs on lung cancer cells. This study was to observe the synergistic anti-proliferative effect of HDAC inhibitor trichostatin A (TSA) combined with paclitaxel on lung cancer cell lines H322 and H1299, and to investigate its mechanism. H322 and H1299 cells were divided into control group, paclitaxel (TAX) group, TSA group, and combination group (TF group, TSA followed by paclitaxel). Cell proliferation was determined by MTT assay. Cell cycle and apoptosis were determined by flow cytometry. The protein expression levels of survivin, ERK, and PARP were determined by Western blot analysis. When combined with TSA, the 50% inhibition concentration (IC50) of paclitaxel decreased from (48.07+/-26.12) nmol/L to (6.34+/-5.72) nmol/L in H322 cells and from (110.6+/-38.7) nmol/L to (63.7+/-11.8) nmol/L in H1299 cells, with significant differences (P<0.05). Apoptosis rate of H322 cells was higher in the the TF group than in the TAX group(P<0.05). There were more necrosis cells in the TF group of H1299 cell line than in the other groups. pERK was up-regulated in the TAX group of H322 cell line. Expression of Survivin was up-regulated in the TAX group of two cells. Expressions of Survivin and pERK were down-regulated in the TSA and TF groups of two cell lines. Cleaved PARP was detected in the TAX and the TF groups of H322 cells, and its expression was significantly higher in the the TF group than in the TAX group. Cleaved PARP was not detected in each group of H1299 cells. TSA combined with paclitaxel has a synergistic cytotoxicity effect on lung cancer cell lines H322 and H1299 when the cells were treated with TSA followed by paclitaxel. The mechanism may be that TSA down-regulates the survivin high-expression induced by paclitaxel, and blocks pERK protein expression.