In vitro activity: LBH589 induces apoptosis among MOLT-4 and Reh cells in a time- and dose-dependent manner. Moreover, LBH589 is more potent in MOLT-4 than in Reh cells. LBH589 markedly prevents the growth of both MOLT-4 and Reh cells in a dose-dependent manner at 48 hours. LBH589 treatment causes a 2- to 3-fold increase in the number of cells in the G2/M phase of the cell cycle compared with the control cells. LBH589 is associated with induction of histone H3K9 and histone H4K8 acetylation as well as decreasing levels of c-Myc expression in a dose-dependent manner. LBH589 treatment also increases the levels of p21 expression. LBH589 treatment also decreases the levels of c-Myc after an initial increase at the lowest dose (10 nM) in Reh cells. In addition, LBH589 gives rise to substantial increases in mRNA levels of proapoptosis and DNA repair genes. LBH589 induces increased levels of acetylated histone H3 and H4 at the GADD45G promoter. Besides, LBH589 inhibits growth of non small cell lung cancer cell lines (such as human H1299, L55 and A549 with IC50 of 5 nM, 11 nM and 30 nM, respectively), mesothelioma (such as human OK-6 and Ok-5 with IC50 of 5 nM and 7 nM, respectively) and small cell lung cancer cell lines (such as human RG-1 and LD-T with IC50 of 4 nM and 5 nM, respectively).

Kinase Assay: Panobinostat is a non-selective histone deacetylase (HDAC) inhibitor.

Cell Assay: Untreated and LBH589-treated cells [human Ph- acute lymphoblastic leukemia MOLT-4 (T cells) and Reh (pre-B cells)] are stained with annexin V and propidium iodide using annexin V-FITC apoptosis detection kit I. The percentage of apoptotic and nonviable cells is determined by flow cytometry. At least 5 × 104 cells are collected with a CyAn ADP Violet cytometer. Percentage apoptosis is calculated considering all the annexin V-positive plus the annexin V/PI-positive cells; percentage loss of cell viability is calculated considering all the annexin V-positive plus the PI-positive and the annexinV/PI-positive cells.