Academic literature on the topic 'LBH-589'

Abstract Medulloblastoma (MB) is the most common primary pediatric malignant brain tumor. Current molecular analysis classifies MB into 4 groups, classic (WNT), sonic hedgehog (Shh), group 3, and group 4. Furthermore, atypical p53 signaling is associated with disease progression and confers poor prognosis. This study investigated the correlation of mutational status of p53 and iSO17q with disease progression and metastatic potential. In addition, we used small molecule inhibitors of PI3K (Buparlisib; BKM120) and HDAC (LBH-589) on a p53-mutant MB cell line to find novel therapeutic targets. Efficacy of these drugs were assessed using functional assays (cell proliferation, migration, cell cycle and drug resistance). MB tumors (n=53) were evaluated for GLI-1, GAB-1, NPR, KV1, YAP expression and mutant p53 via immunohistochemistry and correlated to patient outcomes. Results demonstrated that: 1) high expression of GAB-1 and YAP were found in the Shh group, while KV1 expression was present in all subtypes; 2) mutant p53 expression was present in various subsets of MB with no apparent correlation with metastasis or disease progression; 3) patients displaying iSO17q (determined by fluorescence in situ hybridization (FISH) technique) exhibited metastatic disease; 4) LBH-589 and BKM120 caused both time and dose-dependent inhibition of MB cell proliferation and migration; 5) combined treatment of BKM120 and LBH-589 had a synergistic effect; 6) MB cells demonstrated drug-resistance to BKM120. In conclusion, these findings underscore use of Buparlisib and LBH-589 in treatment of MB. Further, the role of mutant p53 in disease progression remains elusive, whereas presence of iSO17q defines metastatic potential.

Abstract Introduction Although T cell acute lymphoblastic leukemia (T-ALL) is a genetically heterogeneous disease, mutations resulting in activation of the Notch-1 signalling pathway are present in over 50% of patients, thus defining Notch signaling as a central player in T-ALL disease regulation. Furthermore, despite improvement in remission rates following conventional chemotherapeutics, the prognosis for T-ALL remains poor due to disease relapse, which is often refractory to the initial therapies. Inhibitors against the γ-secretase complex, which is part of intracellular Notch-1 (ICN1) signalling, have so far shown limited efficacy and are associated with severe toxicity. Therefore, alternative approaches to treat Notch-1-driven T-ALL are required. The gene expression signature of Notch-1-mutated T-ALLs has revealed downstream activation of numerous pathways, including Myc, PI3K-AKT-mTOR and NFκB, indicating potential sensitivity to small molecule histone deacetylase inhibitors (HDACi). Therefore, the aim of this study was to use a traceable pre-clinical mouse model of Notch-1 driven T-ALL to investigate the potential of HDACi as therapy. Methods Retroviral transduction of mouse hematopoietic stem cells with constructs encoding ICN, followed by transplantation into irradiated recipient mice, is an established model of T-ALL resulting from Notch-1 activating mutations, and closely mimics human disease. For the present study, we transduced foetal liver stem cells from day E14.5 embryos with constructs expressing either ICN1-GFP, or GFP only. Cohorts of recipient mice developed leukaemia as described previously, characterized by splenomegaly, lymphadenopathy, elevated peripheral white blood cell counts, and the presence of double positive CD4+CD8+GFP+ blasts in peripheral blood, with a small fraction of recipients presenting with single positive CD4+GFP+ or CD8+GFP+ blasts. T-ALL blasts were isolated from this primary leukemia colony and transplanted into sub-lethally irradiated recipient mice. Using this model, cohorts of mice rapidly developed onset of leukemia with significant engraftment of T-ALL blasts in bone marrow, spleen, thymus, liver and detectable blasts in peripheral blood 15 days post transplant. Results GFP+ T-ALL blasts were isolated from lymph nodes and spleen and cultured in vitro in the presence of αCD3 and interleukin 2 to induce robust proliferation. Treatment of these T-ALL blasts with the pan-HDACi Panobinostat (LBH-589) induced cell death and inhibited proliferation of remaining viable blasts in a dose-dependent manner. These results illustrate that LBH-589 is a potent inhibitor of survival and proliferation of Notch driven T-ALL at low nM concentrations in vitro. Furthermore, treatment of cohorts of mice transplanted with ICN1-T-ALL with LBH-589 significantly prevented expansion of disease in vivo as determined by white blood cell counts. Additionally, we monitored leukemic cells infiltration in secondary lymphatic tissues using non-invasive GFP imaging. Whilst high GFP readings were observed in vehicle treated groups, we observed very little signal in LBH-589 treated mice confirming prevention of disease expansion. Of most importance, the effect of LBH-589 on progression of disease was reflected in a significant increase in survival of treated cohorts compared to controls. Conclusions The considerably high relapse rates of T-ALL patients demands the development of novel therapies for disease that is refractory to initial therapies. Our results indicate that LBH-589 has strong potential for development of therapies for Notch driven T-ALL and may be a useful addition to current therapies, either during initial treatment or after relapse of chemoresistant T-ALL. Moreover, we have preliminary data suggesting that LBH-589 has the ability to target the predominant oncogenic “Myc signature” associated with constitutive Notch expression. We are currently performing gene and protein expression analysis to exactly determine the molecular effects of HDACi on ICN and associated downstream effector signalling. Disclosures: Johnstone: Novartis: Research Funding.

Abstract BACKGROUND: Infant acute lymphoblastic leukaemia (ALL) is a rare but aggressive malignancy, mainly presenting with chromosomal rearrangements of the MLL (Mixed Lineage Leukaemia) gene locus on 11q23. The majority of these MLL rearrangements involve the translocation partners AF4, AF9 or ENL within the translocation events t(4;11)(q21;q23), t(9;11)(p22;q23) and t(11;19)(q23;p13.3), respectively. The resulting fusion genes, MLL-AF4, MLL-AF9 and MLL-ENL, code for chimeric transcription regulators acting as strong oncogenic drivers, rewriting the epigenetic landscape of the cell and profoundly altering gene expression. Consequently, these cytogenetic lesions define an ALL subtype both biologically and clinically distinct from other subtypes, strongly associated with drug resistance to first-line chemotherapeutics, high relapse rates and a dismal prognosis. Hence, novel treatment strategies which specifically target the underlying molecular pathobiology of this disease are urgently needed. AIMS: Previously, our group performed extensive patient cohort profiling on both transcript and epigenetic level in order to understand the molecular events underlying the disease, and identified histone deacetylase inhibitors (HDACi) as effective therapeutic drugs both in silico and in vitro. The aim of the current study was to elucidate potential molecular mechanisms by which the candidate HDACi Panobinostat is able to target MLL-rearranged ALL (MLLr-ALL) cells, and to confirm its efficacy in vivo using pre-clinical MLLr-ALL xenograft mouse models able to recapitulate the disease phenotype observed in humans. METHODS: Immunodeficient NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice were injected intrafemurally with a MLL-AF4+ B-ALL cell line (SEM) genetically modified to express a luciferase reporter. These mice were subsequently either treated with low-dose (1mg/kg) or high-dose (5mg/kg) Panobinostat using a continuous 5-day-on-2-day-off regimen for a period of up to 12 weeks, or they were assigned to a control group and left untreated. Disease onset and progression was monitored using in vivo bioluminescence imaging, and systemic human ALL cell infiltration was determined by multi-colour flow cytometry and histochemistry. In addition, molecular changes induced by Panobinostat exposure in MLLr-ALL and non-MLLr-ALL cell lines were assessed in vitro using immunoblotting and cell death assays. RESULTS: High-dose Panobinostat resulted in a significantly and substantially delayed MLLr-ALL disease onset and progression in NSG mice when compared to controls; this was accompanied by a reduction of the systemic disease burden, as evidenced by significantly lower whole-body luminescence signals and substantially decreased splenomegaly. Furthermore, immunohistochemical and flow cytometric data showed hypocellularity and increased cell death in the BM of xenografted NSG mice treated with Panobinostat when compared to untreated control xenografts. This finding correlated well with in vitro results, where exposure with 5 nM Panobinostat induced cell death in MLLr-ALL cells, but not in non-MLLr ALL cells, as determined by both ANNEXINV/7AAD flow cytometry assays and immunoblotting. In addition, on a molecular level, in vitro exposure with Panobinostat induced histone H3 hyperacetylation in all leukaemic cell lines, but did not affect other histone modification marks investigated such as, i.e., histone H3K4 methylation or histone H3K79 methylation. A notable exception was observed in MLLr-ALL cell lines, where Panobinostat exposure correlated with a reduction in histone H2B ubiquitination, a histone modification recently reported to be pivotal for MLLr leukaemogenesis. Concomitantly, Panobinostat - or more generally - HDACi-mediated loss of H2B ubiquitination might play a role in the observed sensitivity of MLLr-ALL cell towards this drug class. CONCLUSIONS: Both the in vivo and the molecular in vitro results show the HDACi Panobinostat to have promising therapeutic potential against MLLr-ALL. Currently, we are investigating Panobinostat in combination with other epigenetic drugs in xenograft models with primary MLLr-ALL patient material in order to consolidate these observations, and to confirm HDACi as a novel powerful treatment strategy in MLLr-ALL. Disclosures No relevant conflicts of interest to declare.

The state of histone acetylation plays a very crucial role in carcinogenesis and its development by chromatin remodeling and thus altering transcription of oncogenes and tumor suppressor genes. Such epigenetic regulation was controlled by zinc-dependent histone deacetylases (HDACs), one of the major regulators. Due to the therapeutic potential of HDACs as one of the promising drug targets in cancer, HDAC inhibitors have been intensively investigated over the last few decades. Notably, there are five HDAC inhibitors already approved to the market. Vorinostat (SAHA), Belinostat (PXD-101) and Romidepsin (FK228) have been approved by Food and Drug Administration (FDA) in USA for treating cutaneous T-cell lymphoma (CTCL) or peripheral T cell lymphoma (PTCL) while Panbinostat (LBH-589) has also been approved by the FDA for the treatment of multiple myeloma. Recently, Chidamide was approved by China Food and Drug Administration (CFDA) for the treatment of PTCL. The structural feature of almost all HDAC inhibitors consists of Cap group, linker, and zinc-binding group (ZBG). The binding of ZBG groups to zinc ion plays a decisive role in the inhibition of HDAC. Therefore, we will summarize the developed HDAC inhibitors according to different ZBG groups and discuss their binding mode with zinc ion.

Abstract Osteoblasts are known to protect acute myeloid leukemia (AML) cells in the bone marrow microenvironment, however, the identity of these protective signals is not known. Because disrupting this protection could help prevent the relapse of AML patients following chemotherapy, we characterized the molecular mechanisms. We previously showed that SDF-1 (CXCL12), a chemokine abundant in the bone marrow, induces apoptosis of AML cells in cocultures unless the leukemic cells are protected via proximity to differentiating osteoblasts. Treating differentiating osteoblasts with either suberoylanilide hydroxamic acid (SAHA) or LBH-589 histone deacetylase (HDAC) inhibitor drugs inhibited their protection of AML cells. RNAseq revealed that SAHA globally inhibits osteoblast differentiation while inducing expression of the scaffold protein, Nherf-1. Remarkably, expressing Nherf-1 in differentiating osteoblasts was both required and sufficient to block osteoblast-mediated protection of AML cells. Together, these results indicate that disrupting the differentiation of osteoprogenitors in the bone marrow inhibits their ability to protect AML cells from apoptosis, and that this can be achieved via either inhibiting HDACs or overexpressing Nherf-1 in osteoblast-lineage cells. HDAC inhibitors or treatments specifically designed to induce Nherf-1 expression either during or immediately prior to chemotherapy may therefore be a useful strategy for reducing the risk of disease relapse in AML patients.

440 Background: LBH589 is a novel histone deacetylase inhibitor (HDACi) that induces apoptosis of tumor cells. In renal cell carcinoma (RCC) and non-small-cell lung cancer (NSCLC) cell lines, the combination of sorafenib and HDACi was found to have synergistic inhibition, which correlated with the induction of an ER stress response. In this phase I study, we evaluated the combination of LBH589 and sorafenib in previously treated patients with RCC (9pts), soft tissue sarcomas (1pt), and NSCLC (6pts). The trial was designed to determine the safety profile and maximum tolerated dose of LBH589 and sorafenib when administered concurrently. Methods: Patients were dosed with either i.v. or oral LBH 589 (three times per week, continuously) every twenty eight days in combination with standard daily dose sorafenib (400 mg bid). The dose escalation was based on a “3+3” algorithmic design. LBH was initially administered at an i.v. dose of 5 mg/m2 with escalation to 10 mg/m2. Due to the manufacturer’s phase-out of the i.v. formulation, this was then changed to an oral formulation administered three times a week (doses 15 mg, 20 mg, and 25 mg). Results: Sixteen patients, median age 57 years, have been treated. Dose limiting toxicities were observed with grade 4 thrombocytopenia in two patients at the oral dose of 25 mg. There were no other grade 4 events. Grade 3 events included fatigue (2 pts), hypophosphatemia (2 pts), hypertension (1 pts), anemia (1 pt), rash (1 pt) and hand-foot erythroderma (1 pt). Common toxicities for the combination were fatigue (81%), weight loss (62%), loss of appetite (56%), diarrhea (56%), rash (50%), thrombocytopenia (31%), and hand-foot erythroderma (25%). No patients had significant QT prolongation. There was 1 partial response in a patient with lung cancer (31 weeks). Stable disease was noted in seven patients with RCC (78+, 48, 47, 31, 21, 17, and 10+ weeks). Seven patients had progressive disease Conclusions: The administration of oral LBH589 at a dose of 20 mg was found to be well tolerated and will be used in the expansion phase of the trial. Prolonged stable disease was observed in patients previously treated with sorafenib alone, sunitinib and axitinib.