Figure 2.

Summary of the biological effects of the prototypical broad-spectrum HDAC inhibitor (HDAC inhibitors) Trichostatin A (TSA). (A) TSA alters gene transcription by inhibiting histone deacetylase activity and remodelling chromatin architecture. Hyperacetylation of the core histones results in a more open, transcriptionally permissive chromatin structure. TSA also results in the deacetylation of numerous non-histone protein targets. The overall effect of TSA in malignant and transformed cells is decreased proliferation, increased cell-death, induction of apoptosis, decreased migration, cell cycle arrest (predominantly G1 arrest and G1 and G2/M arrest at higher concentrations) and differentiation. (B) TSA results in the accumulation of hyperacetylated histone H3 and α-tubulin in T-cell leukemic CEM-CCRF cells. Cells were treated with the indicated concentrations of TSA for 24 hours prior to extraction of whole cells lysates. Immunoblots of acetylated histone H3 and α-tubulin with a GAPDH loading control are shown. (C) TSA decreases the relative cell viability of CEM-CCRF cells. Cells were treated with the indicated concentrations of TSA for 24 and 48 hours and relative cell viability was measured using the Cell Titre (Promega) assay kit. (D) TSA induces apoptosis in CEM-CCRF cells. Cells were treated with the indicated concentrations of TSA for 24 hours and caspase 3/7 activity was measured using the Apo-One (Promega) assay kit. (E) TSA augments doxorubicin- and radiation-induced DNA double-strand breaks in CEM-CCRF cells. Micrographs of CEM-CCRF cells immunostained forγH2AX (depicted as white foci) are shown. (F) Cells were treated with 0.5μM TSA for 24 hours prior to one hour incubation with 1μM doxorubicin at 37°C. Cells were washed and incubated for a further 24 hours prior to staining for γH2AX. In separate experiments cells were treated with 0.5μM TSA for 24 hours prior to irradiation with 2 Gy (¹³⁷Cs). Cells were stained for γH2AX foci one hour following irradiation.