Pro-apoptotic Family Proteins Research Articles

Experimental Study on the Mechanism of Mangiferin Inhibiting Malignant Biological Characteristics of Multiple Myeloma and Exerting Anticancer Effect

To investigate the effect of pure Chinese herbal extract Mangiferin on the malignant biological behaviors of multiple myeloma (MM) cells, and to analyze the molecular mechanism of the anti-myeloma effect of Mangiferin, so as to provide experimental basis for MM replacement therapy. U266 and RPMI8226 of human MM cell lines were intervened with different concentrations of Mangiferin. Cell proliferation was detected by CCK-8 method. Annexin V/PI double staining flow cytometry was used to detect cell apoptosis. Western blot was used to detect the expression of apoptosis and related signaling pathway proteins, and real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the expression of matrix metalloproteinase (MMP) and CXC chemokine receptor (CXCR) family. Mangiferin could inhibit the proliferation activity of U266 and RPMI8226 cells and induce cells apoptosis. After Mangiferin intervened in U266, RPMI8226 cells for 48 h, the expression of Bcl-2 family pro-apoptotic protein Bax was up-regulated, while the expression of survivin and Bcl-xL proteins was down-regulated and caspase-3 was hydrolyzed and activated to promote cell apoptosis, besides, the expression of Bcl-2 protein in U266 cells was also significantly down-regulated to induce apoptosis (P<0.05). After Mangiferin intervenes in MM cells, it can not only increase the expression level of tumor suppressor p53, but also induce programmed cell death of MM cells by inhibiting the expression of anti-apoptotic molecules and down-regulating the phosphorylation levels of AKT and NF-κB. In addition, after the intervention of Mangiferin, the expressions of CXCR4, MMP2 and MMP9 in U266 cells were down-regulated (P<0.05), while there is no effect on the expressions of CXCR2, CXCR7 and MMP13 (P>0.05). However, the expressions of CXCR4, MMP9, and MMP13 in RPMI8226 cells were down-regulated (P<0.01), the expression of MMP2 was weakly affected, and the expression of CXCR2 and CXCR7 was basically not affected (P>0.05). Mangiferin can inhibit the proliferation and induce apoptosis of MM cells, and its mechanism may be related to inhibiting the activation of NF-κB signaling pathway, affecting the expression of Bcl-2 family proteins, and inhibiting the expression of core members of MMP and CXCR family.

Anti-Apoptotic and Pro-Apoptotic Bcl-2 Family Proteins in Peri-Implant Diseases.

Intrinsic apoptosis, which is regulated by Bcl-2 family proteins, has an important role in chronic inflammatory diseases. The aim of the study was to identify the tissue levels and ratios of anti- and pro-apoptotic Bcl-2 family proteins in peri-implant diseases. Twenty-three individuals with peri-implant mucositis, 25 individuals with peri-implantitis, and 24 controls were included. The following clinical parameters were recorded: keratinized mucosa width, modified bleeding index, probing depth, modified plaque index, modified gingival index, and keratinized tissue thickness. Marginal alveolar bone assessments were performed by a software program. Granulation tissues were collected during treatments of peri-implant diseases. The control tissue samples were collected during the second stage of implant surgery. The tissue levels of Bcl-2 family pro-apoptotic (Bak, Bax, active caspase-3) and anti-apoptotic (Bcl-2, Bcl-xL, Mcl-1) proteins were determined by multiplex immunoassay method. The pro-apoptotic proteins; Bak, Bax and anti-apoptotic proteins Bcl-2, Bcl-xL, Mcl-1 were detected significantly higher in controls compared with patients with peri-implant mucositis and peri-implantitis (p < .001), respectively. The higher active caspase-3 levels were also detected in controls in comparison with peri-implant mucositis (p = .018) and peri-implantitis (p = .005). Anti-apoptotic: pro-apoptotic protein ratios (Bcl-2:Bax, p < .001; Bcl-2:Bak, p = .01; Bcl-xL: Bax, p = .006, Bcl-xL:Bak, p = .011; Mcl-1:Bak, p < .001) were significantly increased in diseased groups. A positive correlation was demonstrated between clinical variables and anti-apoptotic: pro-apoptotic ratios. Our findings indicate dysregulation of the Bcl-2 family proteins in peri-implant diseases. This unregulated response may disturb the homeostasis of peri-implant tissue.

Characterization of the Second Apoptosis Inhibitor Encoded by Guinea Pig Cytomegalovirus.

Despite the usefulness of guinea pig cytomegalovirus (GPCMV) for studies on congenital CMV infection, its viral mechanisms for the evasion of host defense strategies have not been fully elucidated. We reported previously that GPCMV gp38.1 functions as a viral mitochondria-localized inhibitor of apoptosis-like function, and its weak activity suggested the presence of an additional inhibitory molecule(s). Here, we identified gp38.3-2, a 42-amino-acid (aa) reading frame embedded within the gp38.3 gene that encodes a positional homolog of murine CMV (MCMV) m41. Characterization of gp38.3-2 resulted in the following findings: (i) the aa sequence of gp38.3-2 shows some similarity to that of MCMV m41.1, a viral inhibitor of oligomerization of a member of Bcl-2 family protein BAK, but there is no correspondence in their predicted secondary structures; (ii) gp38.3-2, but not gp38.3, showed inhibitory activities against staurosporine-induced apoptosis; (iii) three-dimensional protein complex prediction suggests that the N-terminal α-helix of gp38.3-2 interacts with residues in the BH3 and BH1 motifs of BAK, and analysis of gp38.3-2 and BAK mutants supported this model; (iv) guinea pig fibroblast cells infected with gp38.3-2-deficient GPCMV strain Δ38.3-2 died earlier than cells infected with rescued strain r38.3-2, resulting in lower yields of Δ38.3-2; (v) Δ38.3-2 exhibited a partial but significant decrease in monocyte and macrophage infection in comparison with r38.3-2; and, however, (vi) little difference in the viral infection of guinea pigs was observed between these two strains. Therefore, we hypothesize that gp38.3-2 contributes little to the evasion of host defense mechanisms under the experimental conditions used. IMPORTANCE Although GPCMV provides a useful animal model for studies on the pathogenesis of congenital CMV infection and the development of CMV vaccine strategies, our understanding of the viral mechanisms by which it evades apoptosis of infected cells has been limited in comparison with those of murine and human CMVs. Here, we report a second GPCMV apoptosis inhibitor (42 amino acids in length) that interacts with BAK, a Bcl-2 family proapoptotic protein. Three-dimensional structural prediction indicated a unique BAK recognition by gp38.3-2 via the BH3 and BH1 motif sequences. Our findings suggest the potential development of BH3 mimetics that can regulate inhibition or induction of apoptosis based on short ~40-amino-acid peptide molecules as with GPCMV.

Acetaldehyde Induces Neurotoxicity In Vitro via Oxidative Stress- and Ca2+ Imbalance-Mediated Endoplasmic Reticulum Stress.

Excessive drinking can damage brain tissue and cause cognitive dysfunction. Studies have found that the early stage of neurodegenerative disease is closely related to heavy drinking. Acetaldehyde (ADE) is the main toxic metabolite of alcohol. However, the exact mechanisms of ADE-induced neurotoxicity are not fully clear. In this article, we studied the cytotoxic effect of ADE in HT22 cells and primary cultured cortical neuronal cells. We found that ADE exhibited cytotoxicities against HT22 cells and primary cultured cortical neuronal cells in dose-dependent manners. Furthermore, ADE induced apoptosis of HT22 cells by upregulating the expression of caspase family proapoptotic proteins. Moreover, ADE treatment could significantly increase the intracellular Ca2+ and reactive oxygen species (ROS) levels and activate endoplasmic reticulum stress (ERS) in HT22 cells. ADE upregulated ERS-related CHOP expression dose-dependently in primary cultured cortical neuronal cells. In addition, inhibition of ROS with antioxidant N-acetyl-L-cysteine (NAC) reduced the accumulation of ROS and reversed ADE-induced increase of ERS-related protein and apoptosis-related protein levels. Mitigation of ERS with ERS inhibitor 4-PBA obviously suppressed ADE-induced apoptosis and the expression of ERS-related proteins. Therefore, ADE induces neurotoxicity of HT22 cells via oxidative stress- and Ca2+ imbalance-mediated ERS.

The Clearance Effect of Tetrahedral DNA Nanostructures on Senescent Human Dermal Fibroblasts.

Senescent cells are characterized by their resistance to apoptosis, and upon their long-term survival senescent cells affect tissue function and eventually become deleterious to the organism. Thus, far, it has been gradually accepted that clearance of these senescent cells could reduce tissue dysfunction. This study aimed to investigate biological effects of tetrahedral DNA nanostructures (TDNs) on senescent cells. The results revealed a different biological effect of TDNs, and their clearance effect on senescent cells. TDNs can induce phenotypic changes in senescent cells, suppressing antiapoptotic BCL-2 family proteins and upregulating BAX, a BCL-2 family proapoptotic protein, to influence the expression levels and function of downstream proteins. Consequently, cytochrome C releasing promoted cleavage-mediated activation of pro-caspase-3 and its nuclear translocation from the cytoplasm to mediate apoptosis. The present results provide a foundation for further studies on the application of TDNs in studies on aging.

Histone deacetylation, as opposed to promoter methylation, results in epigenetic BIM silencing and resistance to EGFR TKI in NSCLC.

Drug resistance remains a major challenge in epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) therapy. Bcl-2-like protein 11 (BIM), a B-cell lymphoma 2 family pro-apoptotic protein, is a prime target for specific anti-cancer therapeutics. However, the epigenetic regulation of BIM in non-small cell lung cancer (NSCLC) cell lines and patients with NSCLC in association with EGFR-TKI resistance requires investigation. Methylation-specific PCR (MSP), pyrosequencing, and nested quantitative (q)-MSP were conducted to explore the methylation status of BIM in NSCLC cell lines. In addition, the methylation profile of BIM in patients with NSCLC was assessed by nested q-MSP using circulating free DNA. Cell lines, treated with methylation inhibitor 5-Aza-2'-deoxycytidine (AZA) or histone deacetylation inhibitor trichostatin A (TSA) prior to gefitinib treatment, were examined for BIM gene expression and resistance to gefitinib. All cell lines used in the present study presented with hypo-methylated BIM. Treatment with AZA had no effect on BIM RNA expression in PC9 cells or the gefitinib-resistant cell lines PC9/R and PC9/G2, nor did it reverse their resistance to gefitinib. In contrast, TSA treatment produced the opposite result. In the present study, 25 (78.1%) patients with hypo-methylated BIM and 7 patients (21.9%) with partial or hyper-methylated BIM were identified. The clinicopathological data revealed a random hypo-methylated BIM distribution amongst patients with NSCLC. In the overall study group and EGFR mutant group, hypo-methylated BIM carriers presented with no significant differences in progression free survival compared with patients with partial or hyper-methylated BIM. All cell lines in the present study and the majority of patients with NSCLC carried hypo-methylated BIM. Histone deacetylation, as opposed to promoter methylation, may contribute to the epigenetic silencing of BIM and lead to EGFR TKI resistance in NSCLC.

Restoration of DAP Kinase Tumor Suppressor Function: A Therapeutic Strategy to Selectively Induce Apoptosis in Cancer Cells Using Immunokinase Fusion Proteins.

Targeted cancer immunotherapy is designed to selectively eliminate tumor cells without harming the surrounding healthy tissues. The death-associated protein kinases (DAPk) are a family of proapoptotic proteins that play a vital role in the regulation of cellular process and have been identified as positive mediators of apoptosis via extrinsic and intrinsic death-regulating signaling pathways. Tumor suppressor activities have been shown for DAPk1 and DAPk2 and they are downregulated in e.g., Hodgkin’s (HL) and B cell lymphoma (CLL), respectively. Here, we review a targeted therapeutic approach which involves reconstitution of DAPks by the generation of immunokinase fusion proteins. These recombinant proteins consist of a disease-specific ligand fused to a modified version of DAPk1 or DAPk2. HL was targeted via CD30 and B-CLL via CD22 cell surface antigens.

Prodelphinidins isolated from Chinese bayberry leaves induces apoptosis via the p53-dependent signaling pathways in OVCAR-3 human ovarian cancer cells.

Chinese bayberry leaves are rich in prodelphinidins. Since the isolation and purification of prodelphinidins is difficult, the association between the degree of prodelphinidin polymerization and their anti-carcinogenic activity remains ambiguous. The cytotoxic and apoptotic activities of prodelphinidin Chinese bayberry leaf extracts (PCBLs), oligomeric proanthocyanidins (OPAs) and polymeric proanthocyanidins (PPAs), isolated by normal-phase preparative high-performance liquid chromatography were investigated in OVCAR-3 human ovarian cancer cells. The PCBLs, OPAs and PPAs inhibited cancer cell growth and induced apoptosis via the caspase-dependent pathway. Apoptosis was triggered through the intrinsic pathway by upregulating the expression of several B-cell lymphoma-2 (Bcl-2) family proapoptotic proteins, including p53-upregulated modulator of apoptosis (PUMA), Bcl-2-associated X protein and Bcl-2-associated agonist of cell death, and by downregulating the antiapoptotic protein Bcl-extra large. Apoptosis was also triggered through the extrinsic pathway via the upregulation of death receptor 5 (DR5) and Fas expression. In addition, OPAs and PPAs induced caspase-dependent apoptosis at least partially through the inhibition of the protein kinase B signaling pathway. The knockdown of p53 by specific small interfering RNA resulted in the depletion of p53, and inhibited the OPA and PPA treatment-induced increases in p53, which led to a decrease in the expression of p21, DR5, Fas, PUMA and phosphatase and tensin homolog proteins. These observations demonstrate that p53 is a mediator of OPA and PPA-induced apoptosis in OVCAR-3 cells. The PPAs exhibited stronger anti-proliferative and pro-apoptotic activities compared with OPAs and PCBLs. These results suggest that PCBLs, OPAs and PPAs may be useful for the treatment of ovarian cancer.

Modulator of Apoptosis 1 (MOAP-1) Is a Tumor Suppressor Protein Linked to the RASSF1A Protein

Modulator of apoptosis 1 (MOAP-1) is a BH3-like protein that plays key roles in cell death or apoptosis. It is an integral partner to the tumor suppressor protein, Ras association domain family 1A (RASSF1A), and functions to activate the Bcl-2 family pro-apoptotic protein Bax. Although RASSF1A is now considered a bona fide tumor suppressor protein, the role of MOAP-1 as a tumor suppressor protein has yet to be determined. In this study, we present several lines of evidence from cancer databases, immunoblotting of cancer cells, proliferation, and xenograft assays as well as DNA microarray analysis to demonstrate the role of MOAP-1 as a tumor suppressor protein. Frequent loss of MOAP-1 expression, in at least some cancers, appears to be attributed to mRNA down-regulation and the rapid proteasomal degradation of MOAP-1 that could be reversed utilizing the proteasome inhibitor MG132. Overexpression of MOAP-1 in several cancer cell lines resulted in reduced tumorigenesis and up-regulation of genes involved in cancer regulatory pathways that include apoptosis (p53, Fas, and MST1), DNA damage control (poly(ADP)-ribose polymerase and ataxia telangiectasia mutated), those within the cell metabolism (IR-α, IR-β, and AMP-activated protein kinase), and a stabilizing effect on microtubules. The loss of RASSF1A (an upstream regulator of MOAP-1) is one of the earliest detectable epigenetically silenced tumor suppressor proteins in cancer, and we speculate that the additional loss of function of MOAP-1 may be a second hit to functionally compromise the RASSF1A/MOAP-1 death receptor-dependent pathway and drive tumorigenesis.

Notch4 Signaling Confers Susceptibility to TRAIL-Induced Apoptosis in Breast Cancer Cells.

Notch signaling has been established as a key regulator of cell fate in development, differentiation, and homeostasis. In breast cancers, increased Notch1 and Notch4 activity have been implicated in tumor progression and, accumulation of the intracellular domain of Notch4 (ICN4), reported in basal breast cancer cells. While, TNF-related apoptosis-inducing ligand (TRAIL) receptor agonists have demonstrated selectively in targeting tumor cells, the majority of primary tumors are resistant to TRAIL. This necessitates the identification of factors that might regulate TRAIL sensitivity. Here we investigate TRAIL sensitivity in tumor cells following the modulation of Notch (1 and 4) activity using siRNA-mediated depletions or ectopic expression of GFP-tagged constructs of the intracellular domains of Notch1 (ICN1) or Notch4 (ICN4). Our findings suggest that Notch4, but not Notch1 signaling, sensitizes breast tumor cells to TRAIL-induced apoptosis. ICN4-induced sensitization to TRAIL is characterized by CBF1-dependence. Apoptosis was mediated via caspase-8 activation and regulated by the Bcl-2 family pro-apoptotic proteins Bak and Bid. Finally, we present evidence that endogenous Notch4 activity regulates susceptibility to TRAIL in basal-like breast cancer cells but not in cell lines of luminal origin. These experiments reveal a hitherto unexplored Notch4-TRAIL signaling axis in breast cancer cells.

Histone Deacetylation, Instead of Promoter Methylation, Results in the Epigenetic Silencing of Bim and Resistance to Egfr Tki in Nsclc

ABSTRACT Aim: With targeted therapy improving the survival of advanced stage epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) patients, resistannce remains a major issue in the application of EGFR tyrosine kinase inhibitors (TKIs). Bim, a Bcl-2 family pro-apoptotic protein, has been intensively studied for its role in various targeted therapies. Hence we investigated the epigenetic regulation of Bim in NSCLC cell lines and patients in the hope of identifying its relationship with EGFR TKI resistance. Methods: Methylation specific PCR, pyrosequencing and nested quantitative MSP (nested q-MSP) were applied to study the methylation status of BIM in NSCLC cell lines and the BIM methylation profile in NSCLC patients was assessed by nested q-MSP. PC9 and its gefitinib-resistant cell lines were treated with methylation inhibitor 5-aza-2′-deoxycytidine (AZA) and histone deacetylation inhibitor trichostatin A (TSA) before gefitinib treatment. Bim RNA level, cell survival and resistance to gefitinib were examined. The distribution of various levels of methylated BIM and their relationship with EGFR TKI efficacy was statistically analyzed. Results: 8 NSCLC cell lines all carried hypo-methylated BIM. AZA did not increase the expression of Bim in PC9 and its gefitinib-resistant cell lines, nor did it reverse their resistance to gefitinib. Instead, cells experienced less apoptosis from gefitinib when pre-treated with AZA. TSA on the other hand, not only increased the expression of Bim RNA significantly in the three cell lines, but also reversed their resistance to gefitinib. 25 (78.1%) patients with hypo-methylated BIM and 7 (21.9%) with partial or hyper-methylated BIM were identified. Hypo-methylated BIM distributed randomly in different clinicalpathological charcteristics. In both the entire study group and EGFR mutant group, hypo-methylated BIM carriers experienced no significant PFS difference compared with patients with partial or hyper-methylated BIM. Conclusions: All cell lines in the study and the majority of patients were with hypo-methylated BIM. AZA didn't reverse the resistance to EGFR TKI in acquired resistant cell lines PC9/R and PC9/G2, while HDACi TSA did. Thus histone deacetylation, rather than promoter methylation, may play a major role in the epigenetic silencing of BIM and leads to EGFR TKI resistance in NSCLC. Disclosure: All authors have declared no conflicts of interest.

Importance of Proapoptotic Protein PUMA in Cell Radioresistance

Protein p53 plays an essential role in the induction of apoptosis by ionizing radiation in haemopoietic cells, the damage of which is the main reason for the development of bone marrow post-irradiation syndrome. p53 activation leads to an increase in the Bcl-2 family pro-apoptotic protein PUMA level. PUMA inhibits all the five anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-XL, Bcl-W and A1) and directly triggers apoptosis mediated by pro-apoptotic proteins Bax/Bak. In proliferating cells, knockout of p53 inhibits apoptosis on the one hand, but on the other disables the cellular division arrest moderated by p21Cip1/Waf1. The radioprotective effect of p53 inhibitor pifithrin was obvious at radiation doses causing the bone marrow syndrome. Knockout of PUMA also exerts its radioprotective effect through blocking the apoptosis induction, but the arrest of cells in the cell cycle through p21 induction is not abolished. PUMA -/- mice are radioresistant in terms of the development of post-irradiation syndrome after all radiation doses. Small molecules are being searched for that could prevent binding of PUMA with Bcl-2 family anti-apoptotic proteins. This would result in apoptosis inhibition and radioprotective or mitigating effects of these inhibitors.

Bcl2-interacting killer CpG methylation in multiple myeloma: a potential predictor of relapsed/refractory disease with therapeutic implications

BIK (bcl2-interacting killer) is the founding member of the BH3-only bcl-2 family of pro-apoptotic proteins, which is suppressed in various cancers. In multiple myeloma (MM), BIK has been shown to be epigenetically silenced in vitro, but there is a lack of clinical data. We investigated the CpG methylation status of the BIK promoter in a well-characterized clinical series of patients with MM and investigated its clinical relevance. Forty patients with MM (21 male, 19 female; mean age 66) were studied. According to the International Staging System (ISS) they were classified as 16 patients with stage I, 12 patients with stage II and 12 patients with stage III disease. Methylation in the BIK CpG island was assessed by methylation-specific polymerase chain reaction (MSP) assay. Logistic regression analysis was used to investigate associations between gene methylation and age, ISS stage, performance status, extramedullary disease, bone disease, anemia (hemoglobin ≤10 mg/dL), serum albumin, β2-microglobulin level and relapsed/refractory disease. Methylation in the BIK CpG island was detected in 16 patients (40%), with a trend favoring male gender (odds ratio [OR] = 3.08, p = 0.09) and development of bone disease and extramedullary disease (OR = 1.6, p = 0.35 and OR = 3, p = 0.14, respectively). Patients with MM with methylated BIK CpG island had a statistically significant risk for disease evolution to relapsed/refractory disease (OR = 5.4, p = 0.03). This study provides clinical evidence that methylation-induced transcriptional silencing of the BIK pro-apoptotic gene may occur in MM, which might serve as a predictor of the development of relapsed/refractory MM. These findings warrant validation in larger cohorts of patients and suggest therapeutic utility for agents that enhance BIK expression.

Mineral Trioxide Aggregate Inhibits Osteoclastic Bone Resorption

Mineral trioxide aggregate (MTA), a commonly used endodontic repair material, is useful for both basic and clinical research, and the effect of MTA on osteoblast differentiation has been well-defined. However, the effects of MTA on osteoclastic bone resorption are not fully understood. Hence, the aim of this study is to examine the effect of MTA solution in the regulation of osteoclast bone-resorbing activity using osteoclasts formed in co-cultures of primary osteoblasts and bone marrow cells. MTA solution dose-dependently reduced the total area of pits formed by osteoclasts. The reduction of resorption induced by 20% MTA treatment was due to inhibition of osteoclastic bone-resorbing activity and had no effect on osteoclast number. A 20% MTA solution disrupted actin ring formation, a marker of osteoclastic bone resorption, by reducing phosphorylation and kinase activity of c-Src, and mRNA expressions of cathepsin K and mmp-9. A high concentration of MTA solution (50%) induced apoptosis of osteoclasts by increasing the expression of Bim, a member of the BH3-only (Bcl-2 homology) family of pro-apoptotic proteins. Taken together, our results suggest that MTA is a useful retrofilling material for several clinical situations because it both stimulates osteoblast differentiation and inhibits bone resorption.

Mutations in the 5′ UTR of ANKRD26, the Ankirin Repeat Domain 26 Gene, Cause an Autosomal-Dominant Form of Inherited Thrombocytopenia, THC2

THC2, an autosomal-dominant thrombocytopenia described so far in only two families, has been ascribed to mutations in MASTL or ACBD5. Here, we show that ANKRD26, another gene within the THC2 locus, and neither MASTL nor ACBD5, is mutated in eight unrelated families. ANKRD26 was also found to be mutated in the family previously reported to have an ACBD5 mutation. We identified six different ANKRD26 mutations, which were clustered in a highly conserved 19bp sequence located in the 5' untranslated region. Mutations were not detected in 500 controls and are absent from the 1000 Genomes database. Available data from an animal model and Dr.Watson's genome give evidence against haploinsufficiency as the pathogenetic mechanism for ANKRD26-mediated thrombocytopenia. The luciferase reporter assay suggests that these 5' UTR mutations might enhance ANKRD26 expression. ANKRD26 is the ancestor of a family of primate-specific genes termed POTE, which have been recently identified as a family of proapoptotic proteins. Dysregulation of apoptosis might therefore be the pathogenetic mechanism, as demonstrated for another thrombocytopenia, THC4. Further investigation is needed to provide evidence supporting this hypothesis.

Bortezomib Interacts Synergistically with Belinostat to Induce Apoptosis In Human Acute Myeloid and Lymphoid Leukemia Cells

AbstractAbstract 3266Previous studies have demonstrated interactions between histone deacetylase (HDAC) and proteasome inhibitors (PIs) in multiple myeloma, NHL, and CLL. However, exploration of this strategy in acute leukemias has been more limited. In this context, we have previously demonstrated that HDACIs activate the cytoprotective NF-κB pathway in acute myeloid leukemia (AML) cells, and that interruption of this process dramatically increases lethality. Such findings raise the possibility that PIs, which block degradation of the NF-κB-inhibitory protein IκBα, may act via an analogous mechanism in acute leukemias. Consequently, interactions between the clinically relevant pan-HDAC inhibitor belinostat (PXD-101) and the FDA-approved proteasome inhibitor bortezomib were evaluated in both continuously cultured cell lines and primary AML and acute lymphoid leukemia (ALL) samples. First, whereas each agent individually displayed only modest toxicity, co-treatment for 24 hr or 48 hr with low concentrations of bortezomib (3 - 5 nM) and belinostat (50 - 300 nM) led to pronounced increases in apoptosis in diverse human acute leukemia cell lines (e.g., AML, U937, HL-60, MV-4-11/Flt3-ITD; T-cell ALL, Jurkat; B-cell ALL, SEM). Interactions between these agents were determined to be synergistic by Median Dose Effect analysis. Significantly, equivalent interactions were observed in multiple primary AML (n = 4) and ALL (n = 3) blast specimens, while largely sparing normal CD34+ hematopoietic cells isolated from umbilical cord blood (n = 4), as determined by annexin V/PI, DiOC6, and/or 7-AAD uptake by flow cytometry. Western blot analysis demonstrated that co-exposure of primary leukemia blasts to bortezomib and belinostat resulted in marked increase in PARP cleavage, compared with each agent administrated alone. In addition, cell morphology exhibited classical features of apoptosis in primary acute leukemia blasts, but not in normal CD34+ cells, following combination treatment. Second, in both cell lines and primary blasts, administration of bortezomib resulted in accumulation of the phosphorylated (S32/S36) form of IκBα, accompanied by diminished belinostat-mediated hyperacetylation (K310) of RelA/p65. Bortezomib also blocked processing of the precursor p100 into the active p52, an event enhanced by co-treatment with belinostat. These results indicate that a regimen combining bortezomib and belinostat interrupts both canonical and non-canonical NF-κB signaling pathways in acute leukemia cells. Moreover, co-exposure to these agents diminished expression of NF-κB-dependent pro-survival proteins including Bcl-xL, XIAP, and SOD2, but not NF-κB-independent anti-apoptotic proteins such as survivin. Third, because the BH3-only Bcl-2 family pro-apoptotic protein Bim plays an important role in the lethality of PIs or HDACIs as single agents, the expression and functional role of Bim in bortezomib/belinostat interactions was examined. Notably, whereas treatment with marginally toxic concentrations of either agent alone clearly increased Bim protein levels, co-exposure of either leukemia cell lines or primary blasts to bortezomib and belinostat led to sharply increased Bim expression (particularly the BimEL isoform). Importantly, shRNA knock-down of Bim substantially attenuated lethality mediated by co-treatment with bortezomib and belinostat in both AML (U937) and ALL (Jurkat) cells, supporting the notion that up-regulation of Bim plays a critical role in anti-leukemic activity of the combination regimen. Lastly, exposure of cultured leukemia cells and primary blasts to belinostat ± bortezomib induced hyperacetylation of a-tubulin, indicating inhibition of HDAC6, a microtubule-associated deacetylase that regulates aggresome formation and cell survival in response to misfolded protein-induced stress. Together, these findings indicate that the regimen combining belinostat and bortezomib is highly active against human AML and ALL cells, including primary leukemic blasts, in association with perturbation in the balance between pro-survival (NF-κB-dependent) and pro-death (e.g., Bim) signals. They also suggest that this strategy warrants further attention in acute leukemias. Accordingly, a Phase I trial of belinostat and bortezomib in patients with refractory acute leukemia or MDS has recently been initiated. Disclosures:Off Label Use: Investigational use of belinostat and bortezomib.

Methylated BNIP3 gene in colorectal cancer prognosis

The DNA methylation of apoptosis-related genes in various cancers contributes to the disruption of the apoptotic pathway and results in resistance to chemotherapeutic agents. Irinotecan (CPT-11) is one of the key chemotherapy drugs used to treat metastatic colorectal cancer (CRC). However, a number of metastatic CRC patients do not benefit from this drug. Thus, the identification of molecular genetic parameters associated with the response to CPT-11 is of interest. To identify apoptosis-related genes that may contribute to CPT-11 resistance, microarray analysis was conducted using colon cancer cells in which 5-aza-2'deoxycytidine (DAC) enhanced sensitivity to CPT-11. Microarray analysis identified 10 apoptosis-related genes that were up-regulated following treatment with DAC. Among the genes, Bcl-2/adenovirus E1B 19 kDa protein interacting protein 3 (BNIP3), a Bcl-2 family pro-apoptotic protein, was identified as being involved in CPT-11 resistance following methylation of its promoter. An analysis of 112 primary CRC cases revealed that approximately 58% of cases showed BNIP3 methylation, and that patients with methylation exhibited a poorer outcome compared to those without methylation. In addition, in 30 patients who received first-line CPT-11 chemotherapy, patients with methylation exhibited resistance to chemotherapy compared to patients with no methylation. The results suggest that methylation of BNIP3 is a predictive factor in the prognosis and response to CPT-11 treatment in CRC patients.

BIK (Bcl2-Interacting Killer) CpG methylation status as a potential predictive biomarker of relapsed/refractory multiple myeloma disease.

8118 Background: BIK (bcl2-interacting killer) is the founding member of the BH3-only family proapoptotic proteins. Genomic deletions, epigenetic silencing or post-transcriptional downregulation of BIK by the proteasome and induction of apoptosis upon BIK re-expression reinforce the notion that BIK is a tumor suppressor. Although it has been shown that BIK is a target of epigenetic silencing in cell lines, no studies exist regarding the CpG methylation status of BIK in MM patients. Methods: Bone marrow aspirate samples from MM patients were obtained at diagnosis. Methylation-specific PCR (MSP) was employed to study methylation in the BIK CpG island. Genomic DNA was isolated and bisulphite modification performed using commercially available kits. Control methylated and unmethylated genomic DNAs were included in each experiment. Logistic regression analysis was used to measure the association between gene methylation and age, ISS stage, ECOG performance status, extramedullary disease, bone disease, anemia (Hb <10 g/dl), serum albumin and beta 2 microglobulin levels and relapsed/refractory disease. Results: Methylation in the BIK CpG island was studied in 40 MM patients (21 male, 19 female, mean age 66). Methylation of the BIK CpG island was found in 16 patients (40%) and men were more likely to be methylated (OR=3.08, p=0.01) than women. No correlation was found between BIK CpG methylation and age, ECOG performance status, ISS staging, anemia, beta 2 microglobulin levels, albumin levels, and overall survival. Patients methylated for BIK had a 2-fold tendency to have bone disease (p=0.35) and a 3-fold tendency to have extramedullary disease (p=0.14). Notably, patients with methylated BIK had a significantly higher risk of relapsed/refractory disease (OR=5.4, p=0.033). Conclusions: To the best of our knowledge, this is the first demonstration of aberrant methylation in the BIK CpG island in MM patients. BIK CpG methylation in this series of patients was found to be strongly associated with relapsed/refractory disease. Patients with refractory/relapsed disease could possibly benefit from agents enhancing BIK expression, such as proteasome inhibitors. No significant financial relationships to disclose.

BIK (Bcl2-Interacting Killer) CpG Methylation Status in Multiple Myeloma Patients: a Potential Predictor of Relapsed/Refractory Disease.

Abstract 2397Poster Board II-374 Background-Aim:BIK (bcl2-interacting killer) is the founding member of the BH3-only family proapoptotic proteins and is implicated in the selection of B cells in humans. The expression of BIK in cancer is prevented by chromosomal deletions or by epigenetic silencing. On the other hand, BIK upregulation is induced by proteasome inhibitors such as bortezomib and MG132. Although it has been shown that BIK is a target of epigenetic silencing in the IL-6 dependent multiple myeloma cell line KAS-6/1, no studies exist regarding the CpG methylation status of BIK in primary tumors. We wished to examine the CpG methylation status of BIK in patients with multiple myeloma (MM). Patients and methods:Bone marrow aspirate samples from individuals with MM were obtained at diagnosis. Methylation-specific PCR (MSP) was employed to study methylation in the BIK CpG island. Genomic DNA was isolated and bisulphite modification performed using commercially available kits (QIAmp DNA mini kit, Qiagen and EZ DNA methylation kit, ZymoResearch respectively). Control methylated (CpG GenomeTM Universal Methylated, Chemicon International) and unmethylated genomic DNAs were included in each experiment. Ten bone marrow samples from individuals with borderline thrombocytopenia, that proved to have no haematological malignancy, served as negative controls. Logistic regression analyses were used to measure the association between gene methylation and age, ISS stage, ECOG performance status, extramedullary disease, bone disease, anemia (Hb 10 mg/dl), serum albumin and beta 2 microglobulin levels and relapsed/refractory disease. Results:Methylation in the BIK CpG island was studied in 40 MM patients (21 male, 19 female, mean age 66). ISS staging were as follows: stage I 14 patients (36%), II 12 patients (31%), III 12 patients (31%). Methylation of the BIK CpG island was founded in 16 patients (40%) and men were more likely to be methylated (OR=3.08, p=0.098). No correlation was found between BIK CpG methylation and age, ECOG performance status, ISS staging, anemia, beta 2 microglobulin levels, albumin levels, and overall survival. Patients methylated for BIK had a 2-fold tendency to have bone disease (p=0.35) and a 3-fold tendency to have extramedullary disease (p=0.14). Notable, patients with methylated BIK had a higher risk of relapsed/refractory disease (OR=5.4, p=0.033). Conclusions:To the best of our knowledge, this is the first demonstration of aberrant methylation in the BIK CpG island in MM patients. Interesting associations between BIK CpG methylation and some relevant clinical parameters in patients with MM were suggested by the data. Most importantly, BIK CpG methylation in this series of patients was found to be strongly associated with relapsed/refractory disease. These findings warrant further evaluation in a larger sample of patients in order to better define the prognostic and clinical utility of BIK methylation in MM. Patients with refractory/relapsed disease could possibly benefit from agents enhancing BIK expression. Disclosures:No relevant conflicts of interest to declare.

A primate-specific POTE-actin fusion protein plays a role in apoptosis

The primate-specific gene family, POTE, is expressed in many cancers but only in a limited number of normal tissues (testis, ovary, prostate). The 13 POTE paralogs are dispersed among 8 human chromosomes. They evolved by gene duplication and remodeling from an ancestral gene, Ankrd26, recently implicated in controlling body size and obesity. In addition, several POTE paralogs are fused to an actin retrogene producing POTE-actin fusion proteins. The biological function of the POTE genes is unknown, but their high expression in primary spermatocytes, some of which are undergoing apoptosis, suggests a role in inducing programmed cell death. We have chosen Hela cells as a model to study POTE function in human cancer, and have identified POTE-2alpha-actin as the major transcript and the protein it encodes in Hela cells. Transfection experiments show that both POTE-2alpha-actin and POTE-2gammaC are localized to actin filaments close to the inner plasma membrane. Transient expression of POTE-2alpha-actin or POTE-2gammaC induces apoptosis in Hela cells. Using wild-type and mutant mouse embryo cells, we find apoptosis induced by over-expression of POTE-2gammaC is decreased in Bak ( -/- ) or Bak ( -/- ) Bax ( -/- ) cells indicating POTE is acting through a mitochondrial pathway. Endogenous POTE-actin protein levels but not RNA levels increased in a time dependent manner by stimulation of death receptors with their cognate ligands. Our data indicates that the POTE gene family encodes a new family of proapoptotic proteins.