Mechanisms and potential molecular markers of early response to combination epigenetic therapy in patients with myeloid malignancies.

Combination epigenetic treatment (EGT) utilizing DNA methyl transferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) may be more efficacious than single agent treatment in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). The molecular mechanisms behind the potential clinical efficacy of combination EGT treatment are incompletely understood and the frequently lengthy EGT regimes required to determine clinical response have generated a significant demand for early molecular markers of treatment response. Our study aimed to identify the effect of combination azacitidine (AZA) and panobinostat (LBH589) on expression levels of a panel of genes implicated in the pathogenesis of high-risk MDS or AML in HL-60 cells. We also characterized gene expression profiles in peripheral blood mononuclear (PBMCs) from patients in a recently reported phase Ib/II clinical trial using the combination of AZA and LBH589 and correlated these findings with clinical response to treatment. In vitro analysis demonstrated increased expression of caspase-3, Nor-1, NUR77, p15INK4B and p21WAF1/CIP1 and decreased expression of Bcl­xL in HL-60 cells treated with combination EGT. Analysis of patient samples prior to treatment demonstrated a significant reduction in NUR77 and p21WAF1/CIP1 expression compared to healthy controls. NUR77 and p21WAF1/CIP1 levels were similar between treatment non­responders and responders at screening. Early post first cycle treatment (day 25) analysis demonstrated a significant increase in expression of both NUR77, and p21WAF1/CIP1. A significant increase in NUR77, and p21WAF1/CIP1 together with a trend to increase in p15INK4B first cycle expression was observed in treatment responders compared to non-responders. In summary, combination AZA and LBH589 epigenetic treatment is associated with in vitro and in vivo modulation of genes implicated in the pathogenesis of MDS/AML. Early expression of NUR77 and p21WAF1/CIP1 correlated with clinical response to combination EGT suggesting investigation for potential use as molecular markers of early treatment response may be warranted.

A novel agent with histone deacetylase inhibitory activity attenuates neointimal hyperplasia.

PURPOSE: Neointimal hyperplasia (NIH), a pathophysiological event identified in bypass graft and stent re-stenosis, is characterised by aberrant vascular smooth muscle cell (VSMC) migration and proliferation. Recent evidence identifies histone deacetylase modulation as a regulator of VSMC proliferation and migration and a potential therapeutic target in the treatment of NIH. The purpose of our study was to determine the in vitro and in vivo potential of a novel agent, MCT-3, to modulate VSMC migration, proliferation and NIH. METHODS: In vitro VSMC studies utilized reverse transcriptase and real time Q-PCR gene expression analysis, western blot, elisa assay and cellular proliferation and migration scratch assay's. In vivo studies utilized the partial carotid artery ligation model of NIH together with immunohistochemistry in FVB/N mice. RESULTS: MCT-3 treatment induced histone H3 and H4 acetylation and inhibited VSMC migration and proliferation in vitro and significantly attenuated NIH in vivo. MCT-3-mediated regulation of orphan nuclear receptor NUR77, Plasminogen Activator Inhibitor Type-1 (PAI-1) and cyclin dependent kinase inhibitors (CDKI) p21(CIP1/WAF1) and p27(KIP1) expression was also identified. CONCLUSIONS: Together these observations identify a novel agent, MCT-3, with histone deacetylase inhibitory activity, able to inhibit NIH and identify a potential molecular mechanism responsible for these effects. Additional pre-clinical studies may be warranted to determine the potential clinical utility of this compound.

The anti-leukemic effect and molecular mechanisms of novel hydroxamate and benzamide histone deacetylase inhibitors with 5-aza-cytidine.

Histone deacetylase inhibitors (HDACi) demonstrate considerable in vitro and in vivo activity and clinical efficacy in the treatment of hematological malignancies. Pre-clinical and early phase clinical trials identify therapeutic activity using a combination of HDACi and demethylating agents which may be more efficacious than single agent treatment. Our studies aimed to determine the effects and molecular mechanisms of action of novel hydroxamate (MCT-3) and benzamide [MGCD0103 (MG)] HDACi's in the HL-60 cell line alone and in combination with the demethylating agent 5-aza-cytidine (AZA). MG, MCT-3 and AZA treatment significantly inhibited HL-60 cell growth in vitro with MG being the most potent agent. MG in combination with AZA demonstrated no significant increase in inhibition of cell growth over MG treatment alone whilst MCT-3 in combination with AZA demonstrated increased inhibition of cell growth over either agent alone although no more significant than MG alone. MG alone or MCT-3 in combination with AZA significantly increased p15 and caspase-3 expression. MG and MCT-3 significantly attenuated AZA-induced MMP-9 mRNA expression and proteolytic activity. Interestingly, MCT-3, MG and AZA alone and in combination increased expression of the novel tumour suppressor gene Nur77, important in leukemogenesis, with MG a more potent inducer as a single agent. These observations suggest the enhanced anti-leukemia activity of the combination of AZA and HDACi may only reside with certain HDACi classes and may be in-part explained by regulation of genes associated with cell cycle arrest, apoptosis and tumour suppression.

The anti-leukemic effect of a novel histone deacetylase inhibitor MCT-1 and 5-aza-cytidine involves augmentation of Nur77 and inhibition of MMP-9 expression.

A combination of demethylating agents and histone deacetylase inhibitors (HDACi) has been proposed as a novel therapy in leukemia and myelodysplasia. In HL-60 cells azacytidine (AZA) and Metacept-1 (MCT-1), a novel HDACi augmented inhibition of cell growth and increased apoptosis. In identifying a molecular mechanism responsible for these effects MCT-1 alone and in combination with AZA induced p15INK4b, p21WAF1/CIP1 and Caspase-3 whilst attenuating Bcl-XL expression. Interestingly, MCT-1 in combination with AZA significantly induced the recently identified suppressor of leukemogenesis Nur77 and attenuated AZA-induced MMP-9 expression. The combination of MCT-1 and AZA is more effective in inhibiting leukemic cell growth and induction of apoptosis. Regulation of a recently identified tumour suppressor gene together with cell cycle, apoptosis and matrix degrading proteases may underpin the molecular mechanism responsible for these effects.

Analysis of the apoptotic and therapeutic activities of histone deacetylase inhibitors by using a mouse model of B cell lymphoma.

Histone deacetylase inhibitors (HDACi) can elicit a range of biological responses that affect tumor growth and survival, including inhibition of cell cycle progression, induction of tumor cell-selective apoptosis, suppression of angiogenesis, and modulation of immune responses, and show promising activity against hematological malignancies in clinical trials. Using the Emu-myc model of B cell lymphoma, we screened tumors with defined genetic alterations in apoptotic pathways for therapeutic responsiveness to the HDACi vorinostat. We demonstrated a direct correlation between induction of tumor cell apoptosis in vivo and therapeutic efficacy. Vorinostat did not require p53 activity or a functional death receptor pathway to kill Emu-myc lymphomas and mediate a therapeutic response but depended on activation of the intrinsic apoptotic pathway with the proapoptotic BH3-only proteins Bid and Bim playing an important role. Our studies provide important information regarding the mechanisms of action of HDACi that have broad implications regarding stratification of patients receiving HDACi therapy alone or in combination with other anticancer agents.

Thiazolidinediones inhibit TNFalpha induction of PAI-1 independent of PPARgamma activation.

Increased plasminogen activator inhibitor type 1 (PAI-1) levels are observed in endothelial cells stimulated by tumour necrosis factor alpha (TNFalpha). Thiazolidinediones (TZDs) may inhibit elevated endothelial cell PAI-1 accounting, in part, for the putative atheroprotective effects of TZDs. In an endothelial cell line, Rosiglitazone (RG) and Pioglitazone (PG) inhibited induction of PAI-1 by TNFalpha. The specific peroxisome proliferator-activated receptor gamma (PPARgamma) inhibitor, SR-202, failed to modulate this effect. RG also inhibited the effect of TNFalpha on a reporter gene construct harbouring the proximal PAI-1 promoter and PAI-1 mRNA in cells co-transfected with a dominant-negative PPARgamma construct. RG and PG attenuated TNFalpha-mediated induction of trans-acting factor(s) Nur77/Nurr1 and binding of nuclear proteins (NP) to the cis-acting element (NBRE). SR-202 failed to modulate these effects. The observations suggest TZDs inhibit TNFalpha-mediated PAI-1 induction independent of inducible PPARgamma activation and this may involve in the modulation of Nur77/Nurr1 expression and NP binding to the PAI-1 NBRE.

The novel anti-tumour agent oxamflatin differentially regulates urokinase and plasminogen activator inhibitor type 2 expression and inhibits urokinase-mediated proteolytic activity.

Cell surface, urokinase (u-PA)-mediated, plasminogen activation has recently been recognised as a process integral to extracellular matrix degradation. The primary inhibitor of u-PA activity in the extracellular matrix is plasminogen activator inhibitor type 2 (PAI-2), a serine protease inhibitor. The malignant metastatic phenotype is associated with excessive and uncontrolled, tumour cell-associated, u-PA-mediated, extracellular matrix degradation. Inhibition of the malignant metastatic phenotype via induction of PAI-2 expression and/or inhibition of u-PA expression may represent a novel means via which the metastatic phenotype can be arrested. Agents capable of inducing PAI-2 and/or inhibiting u-PA activity may restrict u-PA-mediated tumour cell proteolysis and facilitate in the development of therapeutic strategies to combat malignant disease. We have identified the hydroxamic acid derivative oxamflatin, previously noted to revert the malignant phenotype in K-ras-transformed NIH-3T3 cells, as capable of upregulating PAI-2 and simultaneously suppressing u-PA expression in two different cell systems. In addition, zymographic analysis indicated that oxamflatin treatment results in a significant reduction in u-PA proteolytic activity in both HT-1080 fibrosarcoma and U-937 histiocytic lymphoma cells. We postulate that oxamflatin represents a novel means by which induction of PAI-2 and concomitant inhibition of u-PA gene and protein expression can be achieved and may be of benefit in inhibiting the malignant metastatic phenotype.

The urokinase-type-plasminogen-activator receptor (CD87) is a pleiotropic molecule.

Since its discovery over a decade ago, evidence has accumulated implicating the cell-surface urokinase receptor (u-PAR), in numerous biological processes. Most notable has been the identification of a critical role for u-PAR in the regulation of cell-surface plasminogen activation in physiological and pathological conditions. Recent evidence suggests that u-PAR, a glycosylphosphatidylinositol-linked receptor, lacking transmembrane and cytoplasmic domains, is also involved in processes not related to plasminogen activation, including cellular adhesion and the transmission of extracellular signals across the plasma membrane. Involvement of activated u-PAR in these events identifies previously unsuspected roles for this molecule and defines a new field of research in u-PAR biology. We discuss the molecular biology of u-PAR together with the underlying mechanisms responsible for the novel functional roles recently ascribed to this pleiotropic molecule.

Urokinase-mediated transactivation of the plasminogen activator inhibitor type 2 (PAI-2) gene promoter in HT-1080 cells utilises AP-1 binding sites and potentiates phorbol ester-mediated induction of endogenous PAI-2 mRNA.

Urokinase-type plasminogen activator (u-PA) bound to its receptor, u-PAR, initiates signal transduction pathways able to induce expression of the activator protein-1 (AP-1) family member c-fos [1]. Since transcription factors bound to AP-1 recognition sequences within the PAI-2 gene promoter play a role in basal and phorbol ester-mediated induction of PAI-2 gene expression, we hypothesised that u-PA/u-PAR-mediated modulation of AP-1 activity would in turn influence constitutive and inducible PAI-2 gene expression. Treatment of HT-1080 or U-937 cells with high molecular weight u-PA (HMW u-PA) resulted in induction of nuclear proteins binding to a functional AP-1 element in the proximal PAI-2 promoter. This increase in AP-1 activity correlated with a transactivation of the PAI-2 gene promoter in transiently transfected HT-1080 cells. We also demonstrate the u-PA treatment potentiated phorbol ester (PMA)-mediated induction of PAI-2 mRNA, indicating that u-PA binding produces a bone fide response in vivo.

Molecular mechanisms governing tumor-necrosis-factor-mediated regulation of plasminogen-activator inhibitor type-2 gene expression.

Plasminogen-activator inhibitor type 2 (PAI-2), a serine protease inhibitor involved in the regulation of urokinase-dependent proteolysis, is also implicated in the inhibition of tumor-necrosis-factor-(TNF)-mediated apoptosis. The PAI-2 gene is one of the most TNF-responsive genes known and is also highly induced by the phorbol ester phorbol 12-myristate 13-acetate (PMA) and the phosphatase inhibitor, okadaic acid, in both HT-1080 fibrosarcoma and U-937 histiocytic cells. We sought to identify and characterize regulatory cis-acting DNA elements and trans-acting factors which mediate basal and inducible PAI-2 gene transcription. A series of promoter deletion mutants (nucleotides -1859 to -91) fused to the chloramphenicol acetyl transferase (CAT) reporter gene were transfected into HT-1080 cells. Two repressor regions were identified; one distally between positions -1859 and -1100, and one proximally between positions -259 and -219. Cells transfected with constructs harboring more than 259 bp promoter sequence produced a 10-15-fold increase in CAT activity when treated with PMA or okadaic acid, but produced only a minimal (2.5-fold) increase in response to TNF. Removal of the proximal repressor by deletion to position -219, or by internal deletion from the -1100 PAI-2 CAT construct, resulted in a selective increase in TNF responsiveness, suggesting that induction of PAI-2 gene transcription by TNF is associated with derepression. Detailed analysis of the proximal repressor utilizing the electrophoretic mobility shift assay (EMSA), identified two novel and distinct protein-binding sites (A and B). Site A is located within the 40-bp proximal repressor while site B is situated immediately adjacent to the 3' boundary. Treatment of cells with PMA or okadaic acid produced no change in the binding activity of proteins recognising sites A or B. However, treatment of cells with TNF results in a profound selective reduction in site-B-binding activity, suggesting that this site plays a significant role in TNF-mediated regulation of PAI-2 gene expression. Our findings suggest that TNF-mediated induction of PAI-2 gene expression involves derepression and is associated with cis-acting and trans-acting factors located within and adjacent to the proximal repressor region.

Malignant pulmonary lymphoid disease: case reports illustrating anatomical pattern of disease as a prognostic marker.

Although a well documented phenomenon in Hodgkin's disease, malignant pulmonary lymphoid disease in other lymphoproliferative diseases, such as non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL), is less frequently described. We present 3 patients, 2 with NHL and one with CLL, all demonstrating pulmonary malignant lymphoid involvement. We briefly review the probable mechanism underlying the development of this disease process and identify anatomical distribution of malignant pulmonary lymphoid disease as a prognostic marker in this condition.