Apoptosis In Hodgkin Lymphoma Cells Research Articles

Correction: Chidamide and decitabine can synergistically induce apoptosis of Hodgkin lymphoma cells by up-regulating the expression of PU.1 and KLF4.

[This corrects the article DOI: 10.18632/oncotarget.20659.].

Chidamide and decitabine can synergistically induce apoptosis of Hodgkin lymphoma cells by up-regulating the expression of PU.1 and KLF4.

Epigenetic abnormalities play important roles in the pathogenesis of Hodgkin lymphoma (HL). Highly expressed class I histone acetyltransferase (HDAC) and hyper-methylation of the promoter region of tumor suppressor genes have been demonstrated in Hodgkin lymphoma. In this paper, we investigated the synergistic effects of combination treatment of chidamide, a selective HDAC inhibitor, and decitabine, a demethylation agent, for HL cell lines and explored a new strategy for treating HL. The apoptosis rates, cell cycle, mitochondrial transmembrane potentials, epigenetic changes and gene expression of HL cell lines treated with chidamide as a single agent and in combination with decitabine were tested. We found that chidamide inhibited the proliferation of HL cells through increased apoptosis. Interestingly, after combined with decitabine, the inhibition rate and apoptotic death in HL cells were significantly increased. Further studies demonstrated that when combined with decitabine the expression of acetylated histone H3 and H3K9 induced by chidamide in HL cells increased, and also the expression of tumor suppressor genes PU.1 and KLF4, which exert inhibition through apoptosis pathway. Therefore, we could come to a conclusion that chidamide and decitabine can synergistically induce apoptosis of Hodgkin lymphoma cells by up-regulating the expression of PU.1 and KLF4. These results provide a new sight in combining two different epigenetic regulatory agents for treating HL.

Characteristic mTOR activity in Hodgkin-lymphomas offers a potential therapeutic target in high risk disease – a combined tissue microarray, in vitro and in vivo study

BackgroundTargeting signaling pathways is an attractive approach in many malignancies. The PI3K/Akt/mTOR pathway is activated in a number of human neoplasms, accompanied by lower overall and/or disease free survival. mTOR kinase inhibitors have been introduced in the therapy of renal cell carcinoma and mantle cell lymphoma, and several trials are currently underway. However, the pathological characterization of mTOR activity in lymphomas is still incomplete.MethodsmTOR activity and the elements of mTOR complexes were investigated by immunohistochemistry on tissue microarrays representing different human non-Hodgkin-lymphomas (81 cases) and Hodgkin-lymphomas (87 cases). The expression of phospho-mTOR, phospho-4EBP1, phospho-p70S6K, phospho-S6, Rictor, Raptor and Bcl-2, Bcl-xL, Survivin and NF-kappaB-p50 were evaluated, and mTOR activity was statistically analyzed along with 5-year survival data. The in vitro and in vivo effect of the mTOR inhibitor rapamycin was also examined in human Hodgkin-lymphoma cell lines.ResultsThe majority (>50%) of mantle cell lymphoma, Burkitt lymphoma, diffuse large B-cell lymphoma, anaplastic large-cell lymphoma and Hodgkin-lymphoma cases showed higher mTOR activity compared to normal lymphoid tissues. Hodgkin-lymphoma was characterized by high mTOR activity in 93% of the cases, and Bcl-xL and NF-kappaB expression correlated with this mTOR activity. High mTOR activity was observed in the case of both favorable and unfavorable clinical response. Low mTOR activity was accompanied by complete remission and at least 5-year disease free survival in Hodgkin-lymphoma patients. However, statistical analysis did not identify correlation beetween mTOR activity and different clinical data of HL patients, such as survival. We also found that Rictor (mTORC2) was not overexpressed in Hodgkin-lymphoma biopsies and cell lines. Rapamycin inhibited proliferation and induced apoptosis in Hodgkin-lymphoma cells both in vitro and in vivo, moreover, it increased the apoptotic effect of chemotherapeutic agents.ConclusionsTargeting mTOR activity may be a potential therapeutic tool in lymphomas. The presence of mTOR activity probably indicates that the inclusion of mTOR inhibition in the therapy of Hodgkin-lymphomas may be feasible and beneficial, especially when standard protocols are ineffective, and it may also allow dose reduction in order to decrease late treatment toxicity. Most likely, the combination of mTOR inhibitors with other agents will offer the highest efficiency for achieving the best clinical response.

Resveratrol‐mediated apoptosis of hodgkin lymphoma cells involves SIRT1 inhibition and FOXO3a hyperacetylation

Resveratrol (RSV), a plant-derived stilbene, induces cell death in Hodgkin lymphoma (HL)-derived L-428 cells in a dose-dependent manner (IC50 = 27 μM, trypan blue exclusion assay). At a lower range (25 μM), RSV treatment for 48 hr causes arrest in the S-phase of the cell cycle, while at a higher concentration range (50 μM), apoptosis can be detected, with activation of caspase-3. The histone/protein deacetylase SIRT1 has been described as a putative target of RSV action in other model systems, even though its role in cancer cells is still controversial. Here we show that RSV, at both concentration ranges, leads to a marked increase in p53, while a decrease of SIRT1 expression level, as well as enzyme activity, only occurred at the higher concentration range. Concomitantly, however, treatments at both concentration ranges resulted in a marked increase in K373-acetylated p53 and lysine-acetylated FOXO3a. Immunohistochemical stainings of human lymph nodes show a preferential distribution of SIRT1 in the germinal center of the follicles while the mantle zone shows nearly no staining to few positive cells. The classical HL-affected lymph nodes show a strong positivity of the diagnostic Hodgkin Reed-Sternberg cells. Notably, both the HL-derived cell lines and the Hodgkin Reed-Sternberg cells of the affected lymph nodes derive from germinal center-derived B cells. The study of SIRT1 distribution and expression on a larger number of biopsies might disclose a novel role for this histone/protein deacetylase as therapeutic target.

Rocaglamide and a XIAP inhibitor cooperatively sensitize TRAIL‐mediated apoptosis in Hodgkin's lymphomas

Although most of the patients with Hodgkin's lymphoma (HL) can be cured by the current regimen of high-dose multiagent chemotherapy, the treatment causes high risks of later toxicities including secondary malignancies. Therefore, new rational strategies are needed for HL treatment. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent due to its tumor selectivity and its lack of toxicity for normal cells. Unfortunately, many cancers remain resistant to TRAIL including HL. HL is characterized by enhanced expression of cellular caspase-8 (FLICE)-inhibitory protein (c-FLIP) and X-linked inhibitor of apoptosis (XIAP), which block receptor-mediated apoptosis by inhibiting caspase-8 and caspase-3, respectively. We have recently discovered the herbal compound Rocaglamide, which breaks TRAIL-resistance in acute T cell leukemia through inhibition of c-FLIP expression. We have also shown that small molecule XIAP inhibitors can sensitize TRAIL-mediated apoptosis in several resistant tumors. However, whether targeting XIAP or c-FLIP is also a suitable strategy to prime HL cells for TRAIL-induced apoptosis has not yet been investigated. In our study, we show that Rocaglamide suppresses c-FLIP expression in HL cells in a dose- and time-dependent manner. However, downregulation of c-FLIP alone was not sufficient to sensitize TRAIL-induced apoptosis in HL cells. Similarly, treatment of HL cells with a small molecule XIAP inhibitor resulted in a moderate induction of apoptosis. However, inhibition of XIAP alone was also not sufficient to enhance TRAIL-induced cell death. Synergistic increase in TRAIL-mediated killing of HL cells was only obtained by combination of Rocaglamide and XIAP inhibitors. Our study demonstrates that targeting both c-FLIP and XIAP are necessary for an efficient treatment of HL.

The histone deacetylase inhibitor entinostat (SNDX-275) induces apoptosis in Hodgkin lymphoma cells and synergizes with Bcl-2 family inhibitors

Based on promising invitro and invivo activity of several histone deacetylase inhibitors in Hodgkin lymphoma (HL), we investigated SNDX-275, an oral class 1 isoform-selective histone deacetylase inhibitors in HL-derived cell lines. Proliferation and cell death were examined by MTS assay, Annexin V/propidium iodide, and fluorescence-activated cell sorting analysis. Gene and protein expression were measured by reverse transcriptase polymerase chain reaction, Western blotting, and immunohistochemical analysis. A multiplex assay was used to determine cytokines and chemokines. SNDX-275 induced cell death in a dose- and time-dependent manner with an IC(50) at the sub- and lower micromolar range at 72 hours. At the molecular level, SNDX-275 increased histone H3 acetylation, upregulated p21 expression, and activated the intrinsic apoptosis pathway by downregulating the X-linked inhibitor of apoptosis protein. SNDX-275 downregulated expression of antiapoptotic Bcl-2 and Bcl-xL proteins without altering Mcl-1 or Bax levels. Combination studies demonstrated that two Bcl-2 inhibitors (ABT-737 and obatoclax) significantly enhanced the effect of SNDX-275. SNDX-275 modulated the level of several cytokines and chemokines, including interleukin-12 p40-70, interferon-inducible protein-10, RANTES (regulated on activation, normal T expressed and secreted), interleukin-13, interleukin-4, and thymus and activation-regulated chemokine and variably induced the cancer/testis antigen expression of MAGE-A4 and survivin in HL cell lines. SNDX-275 has antiproliferative activity in HL cell lines, involving several mechanisms: induction of apoptosis, regulation of cytokines and chemokines, and alteration of cancer/testis antigens. Clinical investigation of SNDX-275 alone or in combination with Bcl-2 inhibitors is warranted in patients with HL. Phase 2 studies with SNDX-275 in HL are ongoing, and future clinical studies should investigate combinations with SNDX-275.

Targeted Restoration of Down-regulated DAPK2 Tumor Suppressor Activity Induces Apoptosis in Hodgkin Lymphoma Cells

Death-associated protein kinase 2 (DAPK2) is a calcium/calmodulin-regulated proapoptotic serine/threonine kinase that acts as a tumor suppressor. Here we show that DAPK2 is down-regulated in Hodgkin lymphoma-derived tumor cell lines and that promoter-region hypermethylation is one mechanism for DAPK2 inactivation. To determine whether selective reconstitution of DAPK2 catalytic activity in these cells could induce apoptosis, we created a fusion protein comprising a human CD30 ligand conjugated to a human DAPK2 calmodulin-deletion mutant. Thus, recombinant immunokinase DAPK2'-CD30L has a constitutive kinase activity with enhanced proapoptotic function. We show that this immunokinase fusion protein inhibits cell proliferation and induces apoptotic cell death specifically in CD30/DAPK2-negative tumor cell lines. This proof-of-concept study provides the first demonstration of therapeutic strategies based on the restoration of a defective, tumor-suppressing kinase activity by a novel class of recombinant immunotherapeutics.

Vorinostat (SAHA) Inhibits STAT6 Phosphorylation and Transcription, Downregulates Bcl-xL, and Induces Apoptosis in Hodgkin Lymphoma (HL) Cell Lines.

Vorinostat (SAHA) Inhibits STAT6 Phosphorylation and Transcription, Downregulates Bcl-xL, and Induces Apoptosis in Hodgkin Lymphoma (HL) Cell Lines. Although the malignant Hodgkin and Reed Sternberg (HRS) cells of HL are of B-cell origin, they infrequently express B-cell antigens. Recent studies demonstrated that several B-cell specific genes are silenced in HRS cells by epigenetic mechanism, suggesting that this process may be reversible and could be explored therapeutically with deacetylase (DAC) inhibitors or hypomethylating agents. Pan-DAC and isotype-selective DAC inhibitors have shown promising activity in vitro and in vivo in a variety of lymphoid malignancies, including HL. However, the mechanisms of antiproliferative action of DAC inhibitors in HL remain unknown. In this study, we examined the antiproliferative effects of the pan-DAC inhibitor vorinostat (inhibits class I and class II DACs) on HL cell lines and determined its effect on signaling mechanisms that are known to promote HRS cell survival, including STAT3, STAT6, Akt, and ERK pathways. Vorinostat inhibited DACs as evident by the increase in histone-3 acetylation as early as 30 minutes of incubation. Furthermore, vorinostat induced the expression of the cell cycle regulatory protein p21 which was associated with an early increase in the G2M cell cycle fraction in HL cells. Vorinostat had no inhibitory effect on SATA3 or ERK, but inhibited STAT6 phosphorylation and transcription in a dose and time dependant manner. This effect was associated with a decrease in Akt phosphorylation on Ser473 residue. Because STAT6 has been reported to transcriptionally regulate Bcl-XL and Thymus and activation-regulated chemokines (TARC), we examined the effect of vorinostat on these two targets in HL cells. TARC has been shown to play an important role in attracting Th2-type T cells and T-regulatory (T-reg) cells, and to be elevated in sera from patients with HL. Vorinostat downregulated the mRNA expression of TARC in a dose dependent manner, suggesting that it may have a role in regulating chemotaxis of reactive T cells and T-reg cells to HL microenvironment in vivo. Moreover, vorinostat reduced the cellular level of the antiapoptotic protein Bcl-xL which was associated with activation of the caspase pathway, and induction of apoptosis in HL cells. Collectively, these data suggest that DAC inhibition in HL by vorinostat may induce cell death by inhibiting STAT6 and downregulating its antiapoptotic target bcl-xL protein. Furthermore, our data suggest that DAC inhibition may have an added effect in vivo on the cellular component in HL microenvironment by inhibiting TARC.

Comprehensive analysis of homeobox genes in Hodgkin lymphoma cell lines identifies dysregulated expression of HOXB9 mediated via ERK5 signaling and BMI1

AbstractMany members of the nearly 200-strong homeobox gene family have been implicated in cancer, mostly following ectopic expression. In this study we analyzed homeobox gene expression in Hodgkin lymphoma (HL) cell lines. Both reverse transcription–polymerase chain reaction (RT-PCR) using degenerate primers and microarray profiling identified consistently up-regulated HOXB9 expression. Analysis of HOXB9 regulation in HL cells revealed E2F3A and BMI1 as activator and repressor, respectively. Furthermore, a constitutively active ERK5 pathway was identified in all HL cell lines analyzed as well as primary HL cells. Our data show that ERK5 probably mediates HOXB9 expression by repressing BMI1. In addition, expression analysis of the neighboring microRNA gene mir-196a1 revealed coregulation with HOXB9. Functional analysis of HOXB9 by knockdown and overexpression assays indicated their influence on both proliferation and apoptosis in HL cells. In summary, we identified up-regulation of HOXB9 in HL mediated by constitutively active ERK5 signaling which may represent novel therapeutic targets in HL.

Prenylation Inhibitors as Potential Therapeutic Drugs in Hodgkin Lymphoma.

Although the therapy of Hodgkin lymphoma has improved, patients still suffer from late toxicities and insufficient treatment of relapses. Hence, new treatment strategies are needed. Statins are used to treat hypercholesterolaemia and prevent cardiovascular disease. There is evidence for a preventive effect of statins in cancer, including lymphoma. So far, nothing is known about a therapeutic activity of statins or related drugs in Hodgkin lymphoma. Statins block the conversion of 3-hydroxy-3-methylglutaryl-coenzyme A to downstream isoprenoid products like farnesyl and geranylgeranyl-pyrophosphate, inhibiting protein prenylation and leading to apoptosis in several malignancies. The anti-tumour activity of the statin simvastatin and three specific prenylation inhibitors (FTI-277, GGTI-298 and tipifarnib) in Hodgkin lymphoma cells was evaluated in cytotoxicity and apoptosis assays. Furthermore, simvastatin was tested in a xenograft model for human Hodgkin lymphoma. First simvastatin induced caspase-related apoptosis in Hodgkin lymphoma cells via the isoprenoid pathway. The IC50 of simvastatin in cytotoxicity assays was < 2 μM. Second simvastatin showed high activity in a mouse model for Hodgkin lymphoma, delaying tumour establishment and inhibiting tumour growth. Finally the geranylgeranyltransferase inhibitor GGTI-298 and the farnesyltransferase inhibitors FTI-277 and tipifarnib displayed anti-tumour activity in Hodgkin lymphoma cells (approximate IC50 in cytotoxicity assays: 20, 7.5 and < 0.1 μM respectively). Importantly, the concentration of simvastatin that induced apoptosis in Hodgkin lymphoma cells was in the range of 2 μM. This corresponds to plasma levels reached in humans in clinical trials with high dose statins in cancer. Thus, our results suggest two possible applications of simvastatin in Hodgkin lymphoma: First simvastatin in high doses could be included in polychemotherapy regimens to improve the remission rate of relapsed patients. Second simvastatin in the cholesterol-lowering dose should be evaluated as a preventive drug for patients in remission to avoid relapses. Moreover, in comparison to other haematological malignancies, the farnesyltransferase-inhibitor tipifarnib was highly cytotoxic in Hodgkin lymphoma cells. Given its activity in clinical trials in haematological neoplasia, its clinical evaluation in Hodgkin lymphoma is warranted. Taken together, prenylation inhibitors are promising drugs for the treatment of Hodgkin lymphoma.

Comprehensive Analysis of Homeobox Genes in Hodgkin Lymphoma Cell Lines Identified Dysregulated Expression of HOXB9 Mediated by Constitutive Active ERK5 Signalling Pathway and BMI1.

Within the human genome nearly 200 homeobox genes have been identified. These are functionally involved in distinct developmental processes during embryogenesis and in the adult. Many have been implicated in cancer mostly following ectopic expression. In this study, we analyzed homeobox gene expression in Hodgkin lymphoma (HL) cell lines using degenerate primers for RT-PCR and Affymetrix U133A expression arrays followed by extended RT-PCR analysis of candidate homeobox genes in additional hematopoietic cell lines. We identified upregulated HOXB9 expression in HL, as well as in anaplastic large cell lymphoma and mediastinal B-cell lymphoma cell lines. Analysis of HOXB9 regulation in HL cells revealed activation by E2F3A, and repression by BMI1, respectively. Constitutive ERK5 pathway activation was identified in all HL cell lines analyzed together with primary HL lymph nodes biopsies. Our data show that ERK5 regulates HOXB9 expression, probably mediated via BMI1 repression. Expression analysis of microRNA gene mir-196a1 which is located upstream of HOXB9 indicated coregulation together with HOXB9. Functional analysis of HOXB9 by knockdown or overexpression assays revealed its influence in both proliferation and apoptosis in HL cells. In summary we identified upregulated expression of HOXB9 in HL, and its regulation mediated by constitutively active ERK5 signalling, thus representing novel therapeutic targets in both HL and NHL subtypes.

Comprehensive Analysis of Homeobox Gene Expression in Hodgkin Lymphoma Cell Lines Reveals Similarities to Prostate Carcinoma.

Homeobox genes code for transcription factors with essential regulatory impact on cellular processes during embryogenesis and in the adult. Increasingly, members of the circa 200 gene strong family are emerging as major oncogenic players, prompting our investigation into possible homeobox gene dysregulation in Hodgkin lymphoma (HL) in which no recurrent oncogene involvement has been known. Accordingly, we screened 6 well characterized HL cell lines (HDLM-2, KM-H2, L-1236, L-428, L-540, SUP-HD1) and 3 non-Hodgkin lymphoma (NHL) cell lines (RC-K8, RI-1, SC-1) for homeobox gene expression using Affymetrix U133-2.0 whole-genome oligonucleotide microarrays. Of 15 candidate genes thus shown to reveal HL-specific expression patterns, 5 homeobox genes were shortlisted as potentially key dysregulatory targets in HL after additional RT-PCR expression analysis relative to controls. While 3/5 homeobox genes were upregulated in HL (HOXB9, HOXC8, HLXB9), 2/5 were downregulated (BOB1, PAX5). Furthermore, cloning and sequencing RT-PCR products obtained with degenerate primers recognizing conserved homeobox motifs confirmed the predominant expression of HOXB9 in HL cells. However, fluorescence in situ hybridization (FISH) analysis of the HOXB locus (at 17q21) revealed no cytogenetic aberrations, indicating that its activation is conducted non-chromosomally in HL cells. Surprisingly, known target genes of HOXB9 and HOXC8 remained unperturbed, implying novel downstream effector pathways in HL cells. Antisense oligos directed against HOXB9 and forced expression experiments using cloned full length HOXB9 cDNA indicated its involvement in both proliferation and apoptosis. Cell cycle regulators BTG1, BTG2 and GEMININ have been described to interact with HOXB9 and may represent potential targets deserving investigation. We recently showed that HLXB9 promotes IL6 expression in HL cells in response to a constitutively active PI3K signalling pathway therein (Nagel et al., Leukemia 19, 841–6, 2005). Our most recent data indicate that HLXB9 is also expressed in various NHL cell lines including anaplastic, diffuse and mediastinal large cell as well as follicular B-cell lymphomas while expression is notably absent from Burkitt, mantle cell and natural killer T-cell lymphomas reflecting their pathologic classification. Intriguingly, our data highlight unexpected similarities between HL and prostate cancer cells which together uniquely overexpress HOXB9, HOXC8 and HLXB9 (or its close homolog GBX2). Additional genes expressed in prostate carcinoma (HOXB13, PRAC1, PRAC2) were detected in two HL cell lines (KM-H2 and L-428) suggesting further parallels may be revealed. Detection of downregulated B-cell differentiation factors BOB1 and PAX5 in our panel of HL cell lines validated this approach. Both factors were previously implicated in oncogenesis of HL lacking IGH rearrangements and other key B-cell characteristics. In summary, we identified a unique homeobox gene expression pattern involving HOXB9, HOXB13, HOXC8 and HLXB9 in HL cell lines resembling that of prostate carcinoma cells. Overexpressed HOXB9 contributes to proliferation and protects against apoptosis in HL cells potentially via interacting with cell cycle regulators BTG1/2 and/or GEMININ.