The pan-deacetylase inhibitor panobinostat induces cell death and synergizes with everolimus in Hodgkin lymphoma cell lines.

The pan-deacetylase inhibitor panobinostat (LBH589) recently has been shown to have significant clinical activity in patients with relapsed Hodgkin lymphoma, but its mechanism of action in Hodgkin lymphoma remains unknown. In this study, we demonstrate that panobinostat has potent antiproliferative activity against Hodgkin lymphoma-derived cell lines. At the molecular level, panobinostat activated the caspase pathway, inhibited STAT5 and STAT6 phosphorylation, and down-regulated hypoxia-inducible factor 1 α and its downstream targets, glucose transporter 1 (GLUT1) and vascular endothelial growth factor. Paradoxically, panobinostat inhibited LKB1 and AMP-activated protein kinase, leading to activation of mammalian target of rapamycin (mTOR) that promotes survival. Combining panobinostat with the mTOR inhibitor everolimus (RAD001) inhibited panobinostat-induced mTOR activation and enhanced panobinostat antiproliferative effects. Collectively, our data demonstrate that panobinostat is a potent deacetylase inhibitor against Hodgkin lymphoma-derived cell lines, and provide a mechanistic rationale for combining panobinostat with mTOR inhibitors for treating Hodgkin lymphoma patients. Furthermore, the effect of panobinostat on GLUT1 expression suggests that panobinostat may modulate the results of clinical diagnostic imaging tests that depend of functional GLUT1, such as fluorodeoxyglucose positron emission tomography.

Histone deacetylase inhibitors in the treatment of lymphoma.

Histone deacetylases (HDACs) play an important role in the regulation of gene expression. In addition to histones, HDACs can modulate the function of many other proteins involved in the regulation of cell survival and proliferation, angiogenesis, inflammation, and immunity. Deregulated HDACs have been shown to be commonly associated with many types of cancer, and are considered promising targets for cancer therapy. Several HDAC inhibitors are in clinical trials as monotherapies or in combination with other anticancer agents, but only two such inhibitors -- vorinostat (suberoylanilide hydroxamic acid) and romidepsin (depsipeptide) -- have been approved by the US Food and Drug Administration for treating relapsed cutaneous T-cell lymphoma. Other HDAC inhibitors, such as belinostat (PXD101), mocetinostat (MGCD0103), entinostat (SNDX-275), and panobinostat (LBH589), are currently in clinical development. This review focuses on the use of HDAC inhibitors in the treatment of relapsed lymphoma.

Potential involvement of several signaling pathways in initiation of the chicken acrosome reaction.

Avian sperm biology has demonstrated specific features in preparation for fertilization. For example, capacitationlike processes and motility hyperactivation do not exist in the form described in mammals. The present study investigated the potential involvement of several signaling pathways, including protein kinase A (PKA), phosphatidylinositol 3 kinase (PIK3), mitogen-activated protein kinase 3/1 (MAPK3/1), and MAPK14 in the chicken acrosome reaction (AR). The presence in chicken spermatozoa of key proteins involved in these signaling pathways (i.e., cAMP-responsive element-binding protein [CREB], AKT, MAPK1, and MAPK14 and their respective phosphorylated forms) was detected using immunoblotting and localized by immunocytochemistry, mainly in the heads. The potential involvement of these pathways in the AR induced by inner perivitelline layer (IPVL) and Ca(2+) was then examined using specific inhibitors and phosphorylation status measurements. The effects of the specific inhibitors on motility were also measured. Phosphorylations of AKT, CREB, and MAPK1, but not MAPK14, were increased at the time of AR. Phosphorylation of AKT was increased in the presence of IPVL alone, whereas both IPVL and Ca(2+) were needed to increase CREB and MAPK1 phosphorylations. Inhibition of the three corresponding pathways blocked the increase in phosphorylation and significantly decreased AR. Inhibitions of the PKA and MAPK1 pathways also significantly decreased motility, whereas MAPK14 and PIK3 inhibition had no effect on motility. Our results suggest that the AR could be mediated by activation of the PKA, PIK3, and MAPK1 pathways through a sequential action involving, successively, PIK3 and then PKA and MAPK1 activations.