Enhanced antimyeloma cytotoxicity by the combination of arsenic trioxide and bortezomib is further potentiated by p38 MAPK inhibition. Leuk Res. 2010;34:85-92. [PMID: 19608275 DOI: 10.1016/j.leukres.2009.05.024]

Arsenic trioxide: applications, mechanisms of action, toxicity and rescue strategies to date

Arsenical medicine has obtained its status in traditional Chinese medicine for more than 2,000 years. In the 1970s, arsenic trioxide was identified to have high efficacy and potency for the treatment of acute promyelocytic leukemia, which promoted many studies on the therapeutic effects of arsenic trioxide. Currently, arsenic trioxide is widely used to treat acute promyelocytic leukemia and various solid tumors through various mechanisms of action in clinical practice; however, it is accompanied by a series of adverse reactions, especially cardiac toxicity. This review presents a comprehensive overview of arsenic trioxide from preclinical and clinical efficacy, potential mechanisms of action, toxicities, and rescue strategies for toxicities to provide guidance or assistance for the clinical application of arsenic trioxide.

Dietary plant pigment on blood-digestive physiology, antioxidant-immune response, and inflammatory gene transcriptional regulation in spotted snakehead (Channa punctata) infected with Pseudomonas aeruginosa

The current study addressed to investigate the effect of lycopene (LYC) on blood physiology, digestive-antioxidant enzyme activity, specific-nonspecific immune response, and inflammatory gene transcriptional regulation (cytokines, heat shock proteins, vitellogenins) in spotted snakehead (Channa punctata) against Pseudomonas aeruginosa. In unchallenged and challenged fish treated with 200 mg LYC enriched diet the growth performance and digestive-antioxidant enzymes increased after 30 days, whereas with inclusion of 100 or 400 mg LYC in the diets, the increase manifested on or after 45 days. No mortality in fish treated with any LYC diet against P. aeruginosa was revealed. In the unchallenged and challenged fish the phagocytic (PC) activity in head kidney (HK) and spleen were significantly enhanced when fed the control diet or other LYC diets, whereas the respiratory burst (RB) activity and nitric oxide (NO) production significantly increased when fed the 200 mg diet for 45 and 60 days. Similarly, the lysozyme (Lyz) activity in the HK and spleen, and total Ig content in serum were significantly higher in both groups fed the 200 mg LYC diet for 15, 45, and 60 days. Heat shock protein (Hsp 70) was significantly improved in the uninfected group fed the 200 mg LYC diet for 45 and 60 days, but Hsp27 did not significantly change among the experimental groups at any time points. TNF-α and IL-6 mRNA pro-inflammatory cytokine expression significantly increased in both groups fed the 200 mg LYC diet after 45 and 60 days, while the IL-12 mRNA expression was moderate in both groups fed the same diet for 60 days. The IL-10 did not significant mRNA expression between groups at any sampling. The iNOS and NF-κB mRNA expression was pointedly high in both groups fed the 200 mg LYC diet on day 45 and 60. Vitellogenin A (VgA) mRNA was significantly higher in the uninfected fish fed the 100 and 200 mg LYC diets for 45 and 60 days, but VgB did not reveal significant difference between the treatment groups at any time points. The present results suggest that supplementation of LYC at 200 mg significantly modulate the blood physiology, digestive-antioxidant enzymes, specific-nonspecific immune parameters, and cytokines, Hsp, and vitellogenins in spotted snakehead against P. aeruginosa.

[miR-202 contributes to sensitizing MM cells to drug significantly via activing JNK/SAPK signaling pathway]

目的

研究microRNA-202（miR-202）对多发性骨髓瘤（MM）细胞生长的影响，并初步探讨miR-202在MM细胞药物敏感性中的作用机制。

方法

荧光定量PCR检测miR-202及其靶基因B淋巴细胞刺激因子（BAFF）在MM细胞中的表达水平。将miR-202模拟物、miR-202抑制物、BAFF干扰质粒（siBAFF）及其阴性对照转染U266细胞，Western blot检测Bcl-2家族和MAPK信号通路蛋白的表达。WST-1法、流式细胞术（Annexin V-FLUOS）分别检测转染后U266细胞的增殖和凋亡情况。

结果

U266细胞、MM患者CD138⁺细胞中miR-202 mRNA表达（分别为0.052±0.009、0.304±0.354）均低于健康对照组（3.550±1.126）（P<0.001，P=0.009），BAFF表达水平（5.700±0.734、9.576±2.887）均高于健康对照组（1.819±0.853）（P<0.001，P=0.006）。miR-202模拟物转染组细胞增殖抑制率高于对照组[（56.04±0.02）％对（18.89±0.32）%，P=0.002]。Western blot结果显示，转染miR-202模拟物后，U266细胞Bcl-2表达下调约24%，而Bax蛋白的表达上调约1.24倍，miR-202模拟物组细胞凋亡率高于对照组[（49.60 ± 4.89）％对（26.20 ± 1.28）%，P=0.029]。硼替佐米和miR-202模拟物联合组细胞凋亡率为（51.23 ± 5.41）%，高于硼替佐米单独处理组（31.70 ± 4.40）％和硼替佐米与模拟物对照联合处理组[（51.23±5.41）％对（31.70±4.40）%，P=0.047；（51.23±5.41）％对（27.94±4.04）%，P=0.028）]，而miR-202模拟物联合沙利度胺和地塞米松与miR-202模拟物对照组相比差异无统计学意义[（11.66±1.91）％对（10.63±1.74）%，P=0.700；（16.35±1.32）％对（17.43±1.95）%，P=0.400]。miR-202模拟物联合硼替佐米对U266细胞的增殖抑制率高于硼替佐米单独处理组[（36.93±5.98）%对（18.18±4.10）%，P=0.029]。miR-202模拟物及硼替佐米处理U266细胞后，p-JNK蛋白表达水平下调。

结论

miR-202模拟物和硼替佐米可协同抑制MM细胞增殖、诱导其凋亡，可能通过miR-202负向调控靶基因BAFF的表达、抑制JNK/SAPK信号通路的活化来实现的。

Extracellular vesicles of multiple myeloma cells utilize the proteasome inhibitor mechanism to moderate endothelial angiogenesis

Bone marrow microenvironment is known to support angiogenesis, thus contributing to progression of multiple myeloma (MM). Bortezomib, a proteasome inhibitor (PI) widely used in MM treatment, has anti-angiogenic activity. Extracellular vesicles (EVs), shedding from cell surface, serve as mediators in cell-to-cell communication. We have hypothesized that MM cells (MMCs) treated with bortezomib generate EVs that could diminish angiogenesis, thus limiting MM progression. In the present study, EVs were obtained from MMCs (RPMI-8226), untreated (naïve) or pre-treated with bortezomib. EVs were outlined using NanoSight, FACS, protein arrays and proteasome activity assays. The impact of MMC-EVs on endothelial cell (EC) functions was assessed, employing XTT assay, Boyden chamber and Western blot. A high apoptosis level (annexin V binding 70.25 ± 16.37%) was observed in MMCs following exposure to bortezomib. Compared to naïve EVs, a large proportion of bortezomib-induced EVs (Bi-EVs) were bigger in size (> 300 nm), with higher levels of annexin V binding (p = 0.0043).They also differed in content, presenting with increased levels of pro-inflammatory proteins, reduced levels of pro-angiogenic growth factors (VEGFA, PDGF-BB, angiogenin), and displayed lower proteasome activity. Naïve EVs were found to promote EC migration and proliferation via ERK1/2 and JNK1/2/3 phosphorylation, whereas Bi-EVs inhibited these functions. Moreover, Bi-EVs appeared to reduce EC proteasome activity. EVs released from apoptotic MMCs following treatment with bortezomib can promote angiogenesis suppression by decreasing proliferation and migration of EC. These activities are found to be mediated by specific signal transduction pathways.

Expression patterns of heat shock protein genes in Rita rita from natural riverine habitat as biomarker response against environmental pollution

River pollution is one of the principal environmental concerns and biomonitoring tools can play an important role in pollution assessment in the riverine environment. Heat shock proteins (Hsps) have been found to be suitable tools for monitoring stress response. In the present study, expression analyses of hsp genes (hsp27, hsp47, hsp60, hsp70, hsc70, and hsp90) and selected hsp-regulatory genes (hsf1, hyou1, ask1, jnk) were carried out by RT-qPCR in catfish Rita rita collected from selected stretches of river Ganga to investigate changes in their expression patterns as biomarker response. Water quality characteristics were measured in terms of physico-chemical characteristics (DO, BOD, COD, pH, conductivity), element profile (arsenic, mercury, cadmium, lead, chromium, zinc, copper) and persistent organic pollutants (POPs; HCH, DDT, aldrin, endosulphan, heptachlor). Water quality index was calculated and sampling sites were categorized as good/medium/bad. Multivariate analysis was carried out taking the water quality parameters and the fold changes in hsp gene expression as variables, which showed that hsp47 and hsp70b correlated well with BOD, an indicator of organic pollution. To identify the organic pollutant(s) which could be influencing the expression of hsps, again multivariate analysis was employed taking concentration of POPs and fold changes of hsps, which showed up-regulation of hsp47 and hsp70b (HSP72i) correlated well with concentrations of aldrin and HCH. Synergistic effects of these POPs could be responsible for the up-regulation of said hsps, although individually present in low concentration; thus, indicating synergistic effect of the POPs on hsp47 and hsp70b up-regulation as biomarker response.

Realgar nanoparticles versus ATO arsenic compounds induce in vitro and in vivo activity against multiple myeloma

Multiple myeloma (MM), a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow, remains incurable despite the use of novel and conventional therapies. In this study, we demonstrated MM cell cytotoxicity triggered by realgar (REA; As₄ S₄ ) nanoparticles (NREA) versus Arsenic trioxide (ATO) against MM cell lines and patient cells. Both NREA and ATO showed in vivo anti-MM activity, resulting in significantly decreased tumour burden. The anti-MM activity of NREA and ATO is associated with apoptosis, evidenced by DNA fragmentation, depletion of mitochondrial membrane potential, cleavage of caspases and anti-apoptotic proteins. NREA induced G₂ /M cell cycle arrest and modulation of cyclin B1, p53 (TP53), p21 (CDKN1A), Puma (BBC3) and Wee-1 (WEE1). Moreover, NREA induced modulation of key regulatory molecules in MM pathogenesis including JNK activation, c-Myc (MYC), BRD4, and histones. Importantly, NREA, but not ATO, significantly depleted the proportion and clonogenicity of the MM stem-like side population, even in the context of the bone marrow stromal cells. Finally, our study showed that both NREA and ATO triggered synergistic anti-MM activity when combined with lenalidomide or melphalan. Taken together, the anti-MM activity of NREA was more potent compared to ATO, providing the preclinical framework for clinical trials to improve patient outcome in MM.

Mitigating potential of Melissa officinale against As3+-induced cytotoxicity and transcriptional alterations of Hsp70 and Hsp27 in fish, Channa punctatus (Bloch)

The mitigating potential of Melissa officinale (MO) (Lamiaceae) against arsenite (As³⁺)-induced oxidative stress, cytogenotoxicity, and expression of stress genes in fish, Channa punctatus (Bloch), teleost, was explored. After confirming the composition of MO extract, caffeic acid (0.96%), hesperidin (1.73%), naringenin (7.70%), lutenolin (3.29%), kaempferol (11.46%) and hesperetin (6.24%), by HPLC-PDA analysis, the experiment was set up in six groups (G1-G6), each containing 10 specimens. Blood, muscle, gills and liver tissues of control and treated fishes were excised at an interval of 24 till 96 h. Ameliorative potential of MO was confirmed by satisfactory restoration of altered activities of malondialdehyde, hydrogen peroxide, superoxide dismutase, catalase, glutathione peroxidise, glutathione reductase, reduced glutathione and ascorbate peroxidase in G4, G5 and G6, co-exposed with 96 h-LC₅₀/10 As³⁺ with MO. A significant (p < 0.05) recovery in the frequencies of cytogenotoxic markers, micronuclei, disintegrated nucleus and echinocytes, which were expressed significantly (p < 0.05) in G3 exposed to sub-lethal concentration of ATO alone, was recorded in fish groups (G4, G5 and G6) together treated with 96 h-LC₅₀/10 of ATO and 2, 4 and 8 ppm of MO, respectively. Moreover, the expression of Hsp70 gene was downregulated (2.29-fold); whereas, Hsp27 gene was upregulated (1.16-fold) in G6, the group co-exposed with 96 h-LC₅₀/10 As³⁺ with 8 ppm of MO in comparison with G3 (3.11-fold for Hsp70; 0.51-fold for Hsp27) after 96 h of exposure period. Thus, it can be inferred that the MO at its tested concentration can be effectively used to mitigate As³⁺ generated toxicities in C. punctatus.

Genome-wide DNA methylation profiling of CpG islands in a morpholino anthracycline derivative-resistant leukemia cell line: p38α as a novel candidate for resistance

Effective leukemia treatment is seriously hampered by drug resistance. We previously showed that aberrant methylation of the topoisomerase IIα gene causes altered gene expression and acquired drug resistance in etoposide‐resistant leukemia cells. In this study, we analyzed the genome‐wide methylation status in resistant leukemia cells. We used MX2, which is a morpholino anthracycline derivative that functions as a topoisomerase IIα inhibitor. We established a human myelogenous leukemia cell line (K562/P) and a related cell line with resistance to MX2 (K562/MX2). Using these cell lines, we investigated the genome‐wide methylation status, compared expression profiles with a microarray, and analyzed the data using Gene Ontology and key node analysis. We demonstrate that the MX2‐resistant cell line was globally hypermethylated. Gene Ontology analysis identified genes involved in the immunological response and gene silencing that were responsible for methylation‐related altered gene expression in drug‐resistant cells. Key node analysis showed that p38α mitogen‐activated protein kinase was a novel enzyme involved in MX2‐related resistance. p38 kinase activity in resistant cells was increased compared to MX2‐sensitive parent cells. Blocking p38α activity using inhibitors and p38α knock down with small interfering RNA restored the sensitivity to MX2 in resistant cells with a decrease in p38 kinase activity as well as decreased expression of p38α mRNA and phosphorylated p38α protein. These findings may lead to a new strategy for treatment of drug‐resistant leukemia cells.

microRNA-539 suppresses tumor growth and tumorigenesis and overcomes arsenic trioxide resistance in hepatocellular carcinoma

AIMS

Dysregulation of microRNAs (miRNAs) plays a critical role in tumor growth and progression. In this study, we sought to explore the expression and biological roles of miR-539 in hepatocellular carcinoma (HCC).

MAIN METHODS

The expression of miR-539 in human HCC tissues and cell lines was examined. The effects of miR-539 overexpression on cell growth, tumorigenicity, arsenic trioxide resistance of HCC cells were determined. The signaling pathways involved in the action of miR-539 in HCC were also investigated.

KEY FINDINGS

miR-539 was downregulated in HCC tissues and cells, relative to corresponding controls. Overexpression of miR-539 inhibited HCC cell viability and colony formation in vitro and impaired tumorigenesis of HCC cells in vivo. Transfection with miR-539 mimic significantly induced apoptosis in HepG2 cells, which was coupled with reduced expression of anti-apoptotic proteins Bcl-2 and Bcl-xL and decreased phosphorylation of Stat3. Overexpression of a constitutively active form of Stat3 partially blocked miR-539-mediated apoptosis. Enforced expression of miR-539 resensitized arsenic trioxide-resistant HCC cells to arsenic trioxide. Intratumoral delivery of miR-539 mimic significantly retarded the growth of xenograft tumors from arsenic trioxide-resistant HCC cells by about 35%, compared to delivery of control miRNA (P<0.05). In combination with arsenic trioxide, miR-539 mimic yielded about 80% decrease in tumor burden.

SIGNIFICANCE

miR-539 functions as a tumor suppressor in HCC and reexpression of this miRNA offers a potential therapeutic strategy for this disease.

P38 MAPK expression and activation predicts failure of response to CHOP in patients with Diffuse Large B-Cell Lymphoma

BACKGROUND

The p38 MAPK is constitutively activated in B-NHL cell lines and regulates chemoresistance. Accordingly, we hypothesized that activated p38 MAPK may be associated with the in vivo unresponsiveness to chemotherapy in B-NHL patients.

METHODS

Tissue microarrays generated from eighty untreated patients with Diffused Large B Cell Lymphoma (DLBCL) were examined by immunohistochemistry for the expression of p38 and phospho p38 (p-p38) MAPK. In addition, both Bcl-2 and NF-κB expressions were determined. Kaplan Meier analysis was assessed.

RESULTS

Tumor tissues expressed p38 MAPK (82 %) and p-p38 MAPK (30 %). Both p38 and p-p38 MAPK expressions correlated with the high score performance status. A significant correlation was found between the expression p-p38 and poor response to CHOP. The five year median follow-up FFS was 81 % for p38(-) and 34 % for p38(+) and for OS was 83 % for p38(-) and 47 % for p38(+). The p-p38(+) tissues expressed Bcl-2 and 90 % of p-p38(-) where Bcl-2(-). The coexpression of p-p38 and Bcl-2 correlated with pool EFS and OS. There was no correlation between the expression of p-p38 and the expression of NF-κB.

CONCLUSION

The findings revealed, for the first time, that a subset of patients with DLBCL and whose tumors expressed high p-p38 MAPK responded poorly to CHOP therapy and had poor EFS and OS. The expression of p38, p-p38, Bcl2 and the ABC subtype are significant risk factors both p38 and p-p38 expressions remain independent prognostic factors.

Effects of p38α/β inhibition on acute lymphoblastic leukemia proliferation and survival in vivo

P38α/β has been described as a tumor-suppressor controlling cell cycle checkpoints and senescence in epithelial malignancies. However, p38α/β also regulates other cellular processes. Here, we describe a role of p38α/β as a regulator of acute lymphoblastic leukemia (ALL) proliferation and survival in experimental ALL models. We also report first evidence that p38α/β phosphorylation is associated with the occurrence of relapses in TEL-AML1-positive leukemia. First, in vitro experiments show that p38α/β signaling is induced in a cyclical manner upon initiation of proliferation and remains activated during log-phase of cell growth. Next, we provide evidence that growth-permissive signals in the bone marrow activate p38α/β in a novel avian ALL model, in which therapeutic targeting can be tested. We further demonstrate that p38α/β inhibition by small molecules can suppress leukemic expansion and prolong survival of mice bearing ALL cell lines and primary cells. Knockdown of p38α strongly delays leukemogenesis in mice xenografted with cell lines. Finally, we show that in xenografted TEL-AML1 patients, ex vivo p38α/β phosphorylation is associated with an inferior long-term relapse-free survival. We propose p38α/β as a mediator of proliferation and survival in ALL and show first preclinical evidence for p38α/β inhibition as an adjunct approach to conventional therapies.

The clinical activity of arsenic trioxide, ascorbic acid, ifosfamide and prednisone combination therapy in patients with relapsed and refractory multiple myeloma

This study aimed to investigate the activity of arsenic trioxide (As2O3) combined with ascorbic acid, ifosfamide, and prednisone chemotherapy in patients with repeatedly relapsed and refractory multiple myeloma (MM). Here, we retrospectively analyzed medical data of 30 MM patients showing progressive disease after receiving at least two previous lines of treatment including an immunomodulatory agent (thalidomide or lenalidomide) and a proteasome inhibitor. There were 19 men and eleven women, aged 54-73 (median 65) years, in this study. The distribution of different isotypes included immunoglobulin G(IgG) (12 patients), IgA (six patients), IgD (three), and light chain (nine patients). All the patients were Durie-Salmon stage III and had relapsed at least three times; the median cycles of prior therapies was 15 (range 10-18). The patients were treated with As2O3, ascorbic acid, and CP (ifosfamide 1 g on day 1, day 3, day 5, and day 7; prednisone 30 mg taken orally for 2 weeks). As2O3 was administered as an intravenous infusion at a dose of 10 mg/d and ascorbic acid at a dose of 2 g/d for 14 days of each 4-week cycle. The results showed that after 2 cycles of therapy, there were five patients that attained partial response, 15 had minimal response, five had no change, and five had progressive disease. The overall response rate was 66.7% (20/30 cases), 50% (10/20 cases), and 40% (2/5 cases), respectively, after 2, 4, and 6 cycles of the therapy. But there were no patients that attained complete remission. The median time of overall survival and progression-free survival were 48 (29-120) and 6 (2-8) months, respectively. The most common treatment-related adverse events included neutropenia, fatigue, anemia, thrombocytopenia, and infection that could be tolerated. The results showed that As2O3 combined with ascorbic acid, ifosfamide, and prednisone chemotherapy may be a choice treatment for repeatedly relapsed and refractory MM patients.

Emerging Therapeutic Strategies for Overcoming Proteasome Inhibitor Resistance

The debut of the proteasome inhibitor bortezomib (Btz; Velcade®) radically and immediately improved the treatment of multiple myeloma (MM), an incurable malignancy of the plasma cell. Therapeutic resistance is unavoidable, however, and represents a major obstacle to maximizing the clinical potential of the drug. To address this challenge, studies have been conducted to uncover the molecular mechanisms driving Btz resistance and to discover new targeted therapeutic strategies and combinations that restore Btz activity. This review discusses the literature describing molecular adaptations that confer Btz resistance with a primary disease focus on MM. Also discussed are the most recent advances in therapeutic strategies that overcome resistance, approaches that include redox-modulating agents, murine double minute 2 inhibitors, therapeutic monoclonal antibodies, and new epigenetic-targeted drugs like bromodomain and extra terminal domain inhibitors.

Arsenic trioxide-based therapy in relapsed/refractory multiple myeloma patients: a meta-analysis and systematic review

Multiple myeloma (MM) is a clonal malignancy characterized by the proliferation of malignant plasma cells in the bone marrow and the production of monoclonal immunoglobulin. Although some newly approved drugs (thalidomide, lenalidomide, and bortezomib) demonstrate significant benefit for MM patients with improved survival, all MM patients still relapse. Arsenic trioxide (ATO) is the most active single agent in acute promyelocytic leukemia, the antitumor activity of which is partly dependent on the production of reactive oxygen species. Due to its multifaceted effects observed on MM cell lines and primary myeloma cells, Phase I/II trials have been conducted in heavily pretreated patients with relapsed or refractory MM. Therapy regimens varied dramatically as to the dosage of ATO and monotherapy versus combination therapy with other agents available for the treatment of MM. Although ATO-based combination treatment was well tolerated by most patients, most trials found that ATO has limited effects on MM patients. However, since small numbers of patients were randomized to different treatment arms, trials have not been statistically powered to determine the differences in progression-free survival and overall survival among the experimental arms. Therefore, large Phase III studies of ATO-based randomized controlled trials will be needed to establish whether ATO has any potential beneficial effects in the clinical setting.

p38α MAPK pathway: A key factor in colorectal cancer therapy and chemoresistance

Colorectal cancer (CRC) remains one of the most common malignancies in the world. Although surgical resection combined with adjuvant therapy is effective at the early stages of the disease, resistance to conventional therapies is frequently observed in advanced stages, where treatments become ineffective. Resistance to cisplatin, irinotecan and 5-fluorouracil chemotherapy has been shown to involve mitogen-activated protein kinase (MAPK) signaling and recent studies identified p38α MAPK as a mediator of resistance to various agents in CRC patients. Studies published in the last decade showed a dual role for the p38α pathway in mammals. Its role as a negative regulator of proliferation has been reported in both normal (including cardiomyocytes, hepatocytes, fibroblasts, hematopoietic and lung cells) and cancer cells (colon, prostate, breast, lung tumor cells). This function is mediated by the negative regulation of cell cycle progression and the transduction of some apoptotic stimuli. However, despite its anti-proliferative and tumor suppressor activity in some tissues, the p38α pathway may also acquire an oncogenic role involving cancer related-processes such as cell metabolism, invasion, inflammation and angiogenesis. In this review, we summarize current knowledge about the predominant role of the p38α MAPK pathway in CRC development and chemoresistance. In our view, this might help establish the therapeutic potential of the targeted manipulation of this pathway in clinical settings.

Dynamic balance of multiple myeloma clonogenic side population cell percentages controlled by environmental conditions

Cancer stem cells are key drivers of tumor progression and disease recurrence in multiple myeloma (MM). However, little is known about the regulation of MM stem cells. Here, we show that a population of MM cells, known as the side population (SP), exhibits stem-like properties. Cells that constitute the SP in primary MM isolates are negative or seldom expressed for CD138 and CD20 markers. In addition, the SP population contains stem cells that belong to the same lineage as the mature neoplastic plasma cells. Importantly, our data indicate that the SP and nonside population (NSP) percentages in heterogeneous MM cells are balanced, and that this balance can be achieved through a prolonged in vitro culture. Furthermore, we show that SP cells, with confirmed molecular characteristics of MM stem cells, can be regenerated from purified NSP cell populations. We also show that the percentage of SP cells can be enhanced by the hypoxic stress, which is frequently observed within MM tumors. Finally, hypoxic stress enhanced the expression of transforming growth factor β1 (TGF-β1) and blocking the TGF-β1 signaling pathway inhibited the NSP dedifferentiation. Taken together, these findings indicate that the balance between MM SP and NSP is regulated by environmental factors and TGF-β1 pathway is involved in hypoxia-induced increase of SP population. Understanding the mechanisms that facilitate SP maintenance will accelerate the design of novel therapeutics aimed at controlling these cells in MM.

High throughput quantitative reverse transcription PCR assays revealing over-expression of cancer testis antigen genes in multiple myeloma stem cell-like side population cells

Multiple myeloma (MM) stem cells, proposed to be responsible for the tumourigenesis, drug resistance and recurrence of this disease, are enriched in the cancer stem cell-like side population (SP). Cancer testis antigens (CTA) are attractive targets for immunotherapy because they are widely expressed in cancers but only in limited types of normal tissues. We designed a high throughput assay, which allowed simultaneous relative quantifying expression of 90 CTA genes associated with MM. In the three MM cell lines tested, six CTA genes were over-expressed in two and LUZP4 and ODF1 were universally up-regulated in all three cell lines. Subsequent study of primary bone marrow (BM) from eight MM patients and four healthy donors revealed that 19 CTA genes were up-regulated in SP of MM compared with mature plasma cells. In contrast, only two CTA genes showed a moderate increase in SP cells of healthy BM. Furthermore, knockdown using small interfering RNA (siRNA) revealed that LUZP4 expression is required for colony-forming ability and drug resistance in MM cells. Our findings indicate that multiple CTA have unique expression profiles in MM SP, suggesting that CTA may serve as targets for immunotherapy that it specific for MM stem cells and which may lead to the long-term cure of MM.

Sequential treatment of HPV E6 and E7-expressing TC-1 cells with bortezomib and celecoxib promotes apoptosis through p-p38 MAPK-mediated downregulation of cyclin D1 and CDK2

Interruption of the cell cycle is accompanied by changes in several related molecules that result in the activation of apoptosis. The present study was performed to verify the apoptotic effects of sequential treatment with bortezomib and celecoxib in TC-1 cells expressing the human papillomavirus (HPV) E6 and E7 proteins. In TC-1 cells sequentially treated with bortezomib and celecoxib, apoptosis was induced through decreased expression of signal transducer and activator of transcription-3 (STAT3), cyclin D1 and cyclin-dependent kinase (CDK) 2, which are major regulators of the G0/G1 cell cycle checkpoint. In addition, increased levels of p21, CHOP, BiP and p-p38 MAPK were identified in these cells. The treatment-induced apoptosis was effectively inhibited by treatment with SB203580, an inhibitor of p-p38. Moreover, the growth of tumors sequentially treated with bortezomib and celecoxib was retarded compared to the growth of tumors exposed to a single treatment with either bortezomib or celecoxib in vivo. We demonstrated that sequential treatment with bortezomib and celecoxib induced apoptosis via p-p38-mediated G0/G1 cell cycle arrest and endoplasmic reticulum (ER) stress. Sequential treatment with these two drugs could therefore be a useful therapy for cervical cancer.

Characterization of p38 MAPK isoforms for drug resistance study using systems biology approach

MOTIVATION

p38 mitogen-activated protein kinase activation plays an important role in resistance to chemotherapeutic cytotoxic drugs in treating multiple myeloma (MM). However, how the p38 mitogen-activated protein kinase signaling pathway is involved in drug resistance, in particular the roles that the various p38 isoforms play, remains largely unknown.

METHOD

To explore the underlying mechanisms, we developed a novel systems biology approach by integrating liquid chromatography-mass spectrometry and reverse phase protein array data from human MM cell lines with computational pathway models in which the unknown parameters were inferred using a proposed novel algorithm called modularized factor graph.

RESULTS

New mechanisms predicted by our models suggest that combined activation of various p38 isoforms may result in drug resistance in MM via regulating the related pathways including extracellular signal-regulated kinase (ERK) pathway and NFкB pathway. ERK pathway regulating cell growth is synergistically regulated by p38δ isoform, whereas nuclear factor kappa B (NFкB) pathway regulating cell apoptosis is synergistically regulated by p38α isoform. This finding that p38δ isoform promotes the phosphorylation of ERK1/2 in MM cells treated with bortezomib was validated by western blotting. Based on the predicted mechanisms, we further screened drug combinations in silico and found that a promising drug combination targeting ERK1/2 and NFκB might reduce the effects of drug resistance in MM cells. This study provides a framework of a systems biology approach to studying drug resistance and drug combination selection.

AVAILABILITY AND IMPLEMENTATION

RPPA experimental Data and Matlab source codes of modularized factor graph for parameter estimation are freely available online at http://ctsb.is.wfubmc.edu/publications/modularized-factor-graph.php.

Targeting the biophysical properties of the myeloma initiating cell niches: a pharmaceutical synergism analysis using multi-scale agent-based modeling

Multiple myeloma, the second most common hematological cancer, is currently incurable due to refractory disease relapse and development of multiple drug resistance. We and others recently established the biophysical model that myeloma initiating (stem) cells (MICs) trigger the stiffening of their niches via SDF-1/CXCR4 paracrine; The stiffened niches then promote the colonogenesis of MICs and protect them from drug treatment. In this work we examined in silico the pharmaceutical potential of targeting MIC niche stiffness to facilitate cytotoxic chemotherapies. We first established a multi-scale agent-based model using the Markov Chain Monte Carlo approach to recapitulate the niche stiffness centric, pro-oncogenetic positive feedback loop between MICs and myeloma-associated bone marrow stromal cells (MBMSCs), and investigated the effects of such intercellular chemo-physical communications on myeloma development. Then we used AMD3100 (to interrupt the interactions between MICs and their stroma) and Bortezomib (a recently developed novel therapeutic agent) as representative drugs to examine if the biophysical properties of myeloma niches are drugable. Results showed that our model recaptured the key experimental observation that the MBMSCs were more sensitive to SDF-1 secreted by MICs, and provided stiffer niches for these initiating cells and promoted their proliferation and drug resistance. Drug synergism analysis suggested that AMD3100 treatment undermined the capability of MICs to modulate the bone marrow microenvironment, and thus re-sensitized myeloma to Bortezomib treatments. This work is also the first attempt to virtually visualize in 3D the dynamics of the bone marrow stiffness during myeloma development. In summary, we established a multi-scale model to facilitate the translation of the niche-stiffness centric myeloma model as well as experimental observations to possible clinical applications. We concluded that targeting the biophysical properties of stem cell niches is of high clinical potential since it may re-sensitize tumor initiating cells to chemotherapies and reduce risks of cancer relapse.

Arsenic trioxide inhibits the proliferation of myeloma cell line through notch signaling pathway

Arsenic Trioxide (ATO) has shown remarkable efficacy for the treatment of multiple myeloma (MM). However, the mechanism by which ATO exerts its inhibitory effect on the proliferation of myeloma cells remains to be clarified. We study the inhibitory effect of ATO at various concentrations on the proliferation of the myeloma cell line RPMI 8226 and discussed the molecular mechanism of ATO on myeloma cell line. Our results proved that ATO had a significant dose-dependent and time-dependent inhibitory effect on the expressions of the Notch receptor (Notch1) and Notch ligand (Jag2). Data from the real-time PCR assay showed that the mRNA expression levels of the Jag2 gene and its downstream gene Hes1 were both significantly down-regulated after the myeloma cells were treated with ATO while the expression of the tumor suppressor gene PTEN was up-regulated. These results elucidated the molecular mechanism underlying the ATO mediated inhibition of myeloma cell proliferation. This is the first report on the anti-myeloma activity in myeloma cells through inhibition of the Notch signaling pathway.

Bortezomib enhances antigen-specific cytotoxic T cell responses against immune-resistant cancer cells generated by STAT3-ablated dendritic cells

Dendritic cell (DC)-based vaccines have received attention as a new therapeutic modality against cancer. However, increased STAT3 activity in the tumor microenvironment makes DCs tolerogenic and suppresses their antitumor activity. In this study, we explored the effects of a combination treatment consisting of a proteasome inhibitor, bortezomib, and an antigen specific STAT3-ablated (STAT3⁻/⁻) DC-based vaccine on the control of TC-1(P3) tumors, a p53-degraded immune resistant cancer cells. We found that E7-antigen expressing STAT3⁻/⁻ DC (E7-DC-1STAT3⁻/⁻) vaccination enhanced generation of E7-specific CD8⁺ T cells, but was not enough to control TC-1(P3) cancer cells. Therefore, we investigated whether bortezomib could create a synergistic effect with E7-DC-1STAT3⁻/⁻ vaccination. We found that apoptosis via down-regulation of STAT3 and NF-κB and up-regulation of Fas and death receptor 5 (DR5) expression in TC-1(P3) induced by bortezomib was independent of p53 status. We also observed that TC-1(P3) cells pretreated with bortezomib had markedly enhanced anti-tumor effects on E7-specific CD8⁺ T cells through a Fas/DR5-mediated mechanism. In addition, TC-1(P3) tumor-bearing mice treated with bortezomib prior to vaccination with E7-DC-1STAT3⁻/⁻ demonstrated enhanced generation of E7-specific CD8⁺ T cells and prolonged survival compared to those treated with monotherapy. These results suggest that the anti-tumor effects against a p53-degraded immune resistant variant generated by antigen-expressing STAT3-ablated mature DCs may be enhanced by bortezomib via death receptor-mediated apoptosis.

The role of p38 in irinotecan-induced DNA damage and apoptosis of colon cancer cells

The role of p38 in irinotecan (CPT-11)-induced damage and cell death in colon cancer cell line SW620 was investigated. We demonstrate that CPT-11 treatment activates p38 in exposed cells, however with concentration dependent dynamics and differing consequences. Higher CPT-11 concentrations induce a massive early but relatively short-lasting p38 activity leading to apoptosis mediated by mitochondria and caspases. Pharmacological or siRNA inhibition of p38 then significantly prevents CPT-11-dependent cell death. Conversely, lower CPT-11 concentrations activate p38 in a delayed, however sustained manner, with apoptosis occurring only in a fraction of cells and in the absence of significant autophagy. Blocking p38 in thus treated cells increases their sensitivity toward CPT-11 and increases cell death. In summary, our results confirm the involvement of p38 in colon cancer cells response to CPT-11 while indicating a varying role of p38 in the final biological response.

Synergistic anticancer effects of arsenic trioxide with bortezomib in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a subtype of B-cell Non-Hodgkin's Lymphoma (NHL) and accounts for ~6% of all lymphomas. MCL is highly refractory to most chemotherapy including newer antibody-based therapeutic approaches, and high-grade MCL has one of the worst survival rates among NHLs. Therefore, the development of new therapeutic strategies to overcome drug resistance of MCL is important. In this article, we tested the effects of arsenic trioxide (As(2) O(3) , ATO) in bortezomib-resistant MCL. ATO is reported to induce complete remission in the patients with relapsed or refractory acute promyelocytic leukemia. Their effects in MCL, however, have not been explored. In this report, we show that ATO effectively inhibited the growth of MCL cells in vitro. ATO treatment also reduced cyclin D1 expression which is a genetic hallmark of MCL and NF-kB expression which was reported to have a prosurvival role in some MCL cells. The induction of apoptosis in MCL was partially due to reduced levels of cyclin D1 and increased levels of apoptosis-related molecules. The antiproliferative effects of bortezomib on MCL greatly increased when the cells were also treated with ATO, indicating ATO can sensitize MCL to bortezomib. Similar results were noted in bortezomib-resistant cell lines. In conclusion, ATO may be an alternative drug for use in combined adjuvant therapies for MCL, and further clinical testing should be performed.

Sulforaphane synergistically enhances the cytotoxicity of arsenic trioxide in multiple myeloma cells via stress-mediated pathways

Persistent paraprotein production in plasma cells necessitates a highly developed rough endoplasmic reticulum (ER) that is unusually susceptible to perturbations in protein synthesis. This biology is believed to account for the exquisite sensitivity of multiple myeloma (MM) to the proteasomal inhibitor bortezomib (BTZ). Despite remarkable response rates to BTZ in MM, BTZ carries the potential for serious side-effects and development of resistance. We, therefore, sought to identify therapeutic combinations that effectively disrupt proteostasis in order to provide new potential treatments for MM. We found that sulforaphane, a dietary isothiocyanate found in cruciferous vegetables, inhibits TNFα-induced Iκβ proteasomal degradation in a manner similar to BTZ. Like BTZ, sulforaphane synergistically enhances the cytotoxicity of arsenic trioxide (ATO), an agent with clinical activity in MM. ATO and sulforaphane co-treatment augmented apoptotic induction as demonstrated by cleavage of caspase-3, -4 and PARP. The enhanced apoptotic response was dependent upon production of reactive oxygen species (ROS) as demonstrated by glutathione depletion and partial inhibition of the apoptotic cascade after pretreatment with the radical scavenger N-acetyl-cysteine (NAC). Combination treatment resulted in enhanced ER stress signaling and activation of the unfolded protein response (UPR), indicative of perturbation of proteostasis. Specifically, combination treatment caused elevated expression of the molecular chaperone HSP90 (heat shock protein 90) along with increased PERK (protein kinase RNA-like endoplasmic reticulum kinase) and eIF2α phosphorylation and XBP1 (X-box binding protein 1) splicing, key indicators of UPR activation. Moreover, increased splicing of XBP1 was apparent upon combination treatment compared to treatment with either agent alone. Sulforaphane in combination with ATO effectively disrupts protein homeostasis through ROS generation and induction of ER stress to culminate in inhibition of protein secretion and apoptotic induction in MM. Our results suggest that sulforaphane deserves further investigation in combination with ATO in the treatment of MM.

BLyS expression and JNK activation may form a feedback loop to promote survival and proliferation of multiple myeloma cells

B-Lymphocyte stimulator (BLyS), a member of tumor necrosis factor superfamily, is a potent co-activator of B cells in vitro, and in vivo induces B cell proliferation and immunoglobulin secretion. Multiple myeloma (MM) is an incurable malignancy of terminally differentiated B cells (plasma cells). Previous studies have well ascertained that BLyS plays an important contributory role in the pathogenesis and propagation of multiple myeloma by virtue of its ability to promote B cell survival, expansion, and differentiation. However, the intracellular signaling of BLyS in human MM cells remains undefined. This study was designed to see whether there was interaction between MAPK signaling pathway and BLyS expression. It was found that the active protein p-JNK was expressed in KM3, U266 and PBMCs of MM patients, and that the expression of BLyS could be changed by JNK pathway activator and inhibitor. In addition, recombinant BLyS activated JNK pathway, while BLyS siRNA treatment inhibited the activation of JNK pathway. The level of BLyS expression and the activation of JNK pathway were positively correlated. These findings suggest that JNK activation and BLyS expression in MM cells may form a positive feedback loop that promotes the survival and proliferation of MM cells, and these may shed some light on the pathogenesis and treatment of MM.

Constitutive activation of p38 MAPK in tumor cells contributes to osteolytic bone lesions in multiple myeloma

Bone destruction is a hallmark of multiple myeloma and affects more than 80% of patients. However, current therapy is unable to completely cure and/or prevent bone lesions. Although it is accepted that myeloma cells mediate bone destruction by inhibition of osteoblasts and activation of osteoclasts, the underlying mechanism is still poorly understood. This study demonstrates that constitutive activation of p38 mitogen-activated protein kinase in myeloma cells is responsible for myeloma-induced osteolysis. Our results show that p38 is constitutively activated in most myeloma cell lines and primary myeloma cells from patients. Myeloma cells with high/detectable p38 activity, but not those with low/undetectable p38 activity, injected into SCID or SCID-hu mice caused bone destruction. Inhibition or knockdown of p38 in human myeloma reduced or prevented myeloma-induced osteolytic bone lesions without affecting tumor growth, survival, or homing to bone. Mechanistic studies showed that myeloma cell p38 activity inhibited osteoblastogenesis and bone formation and activated osteoclastogenesis and bone resorption in myeloma-bearing SCID mice. This study elucidates a novel molecular mechanism—sactivation of p38 signaling in myeloma cells—by which myeloma cells induce osteolytic bone lesions and indicates that targeting myeloma cell p38 may be a viable approach to treating or preventing myeloma bone disease.

Drug inhibition profile prediction for NFκB pathway in multiple myeloma

Nuclear factor κB (NFκB) activation plays a crucial role in anti-apoptotic responses in response to the apoptotic signaling during tumor necrosis factor (TNFα) stimulation in Multiple Myeloma (MM). Although several drugs have been found effective for the treatment of MM by mainly inhibiting NFκB pathway, there are not any quantitative or qualitative results of comparison assessment on inhibition effect between different drugs either used alone or in combinations. Computational modeling is becoming increasingly indispensable for applied biological research mainly because it can provide strong quantitative predicting power. In this study, a novel computational pathway modeling approach is employed to comparably assess the inhibition effects of specific drugs used alone or in combinations on the NFκB pathway in MM and to predict the potential synergistic drug combinations.

Targeting the p38 MAPK pathway inhibits irinotecan resistance in colon adenocarcinoma

Despite recent advances in the treatment of colon cancer, tumor resistance is a frequent cause of chemotherapy failure. To better elucidate the molecular mechanisms involved in resistance to irinotecan (and its active metabolite SN38), we established SN38-resistant clones derived from HCT-116 and SW48 cell lines. These clones show various levels (6- to 60-fold) of resistance to SN-38 and display enhanced levels of activated MAPK p38 as compared with the corresponding parental cells. Because four different isoforms of p38 have been described, we then studied the effect of p38 overexpression or downregulation of each isoform on cell sensivity to SN38 and found that both α and β isoforms are involved in the development of resistance to SN38. In this line, we show that cell treatment with SB202190, which inhibits p38α and p38β, enhanced the cytotoxic activity of SN38. Moreover, p38 inhibition sensitized tumor cells derived from both SN38-sensitive and -resistant HCT116 cells to irinotecan treatment in xenograft models. Finally, we detected less phosphorylated p38 in primary colon cancer of patients sensitive to irinotecan-based treatment, compared with nonresponder patients. This indicates that enhanced level of phosphorylated p38 could predict the absence of clinical response to irinotecan. Altogether, our results show that the p38 MAPK pathway is involved in irinotecan sensitivity and suggest that phosphorylated p38 expression level could be used as a marker of clinical resistance to irinotecan. They further suggest that targeting the p38 pathway may be a potential strategy to overcome resistance to irinotecan-based chemotherapies in colorectal cancer.

Arsenic trioxide-mediated growth inhibition of myeloma cells is associated with an extrinsic or intrinsic signaling pathway through activation of TRAIL or TRAIL receptor 2

Arsenic trioxide (ATO) is a well-known inhibitor of cell proliferation. Preclinical and clinical studies showed that ATO has anti-myeloma effects. However, the underlying mechanism remains elusive. In this study, the molecular mechanisms of ATO-induced myeloma apoptosis were explored on four myeloma cell lines of wild type or mutant p53 status and also on six primary myeloma cells. ATO induced potent inhibition of myeloma cell growth and myeloma cell apoptosis compared with controls. Further investigation showed that ATO down-regulated c-Myc and phosphorylated (p)-Rb while up-regulating p53, p21Cip1, and p27Kip1 proteins, resulting in G0/G1 or G2/M cell cycle arrest. ATO treatment increased mRNA levels of interferon regulatory factor-1 and TRAIL, as well as protein levels of caspase 8 and cleaved caspase 3, indicating the involvement of the extrinsic apoptotic pathway in the mutated p53 myeloma cells. ATO also activated caspases 3 and 9, indicating involvement of the intrinsic apoptotic pathway in the wild type p53 myeloma cells. More importantly, these molecular changes induced by ATO-treated myeloma cells are very similar to the baseline expression pattern of hyperdiploid myeloma, which has a relative good prognosis with high expression of TRAIL and interferon related genes. Together, our data suggest that ATO induces apoptosis in MM through either extrinsic or intrinsic signaling pathway, depending on the p53 genetic background. These observations may be employed as prognostic tools and lead to novel therapies in primary myelomas.

Identification of novel 14-3-3ζ interacting proteins by quantitative immunoprecipitation combined with knockdown (QUICK)

The family of 14-3-3 proteins has emerged as critical regulators of diverse cellular responses under both physiological and pathological conditions. To gain insight into the molecular action of 14-3-3ζ in multiple myeloma (MM), we performed a systematic proteomic analysis of 14-3-3ζ-associated proteins. This analysis, recently developed by Matthias Mann, termed quantitative immunoprecipitation combined with knockdown (QUICK), integrates RNAi, SILAC, immunoprecipitation, and quantitative MS technologies. Quantitative mass spectrometry analysis allowed us to distinguish 14-3-3ζ-interacting proteins from background proteins, resulting in the identification of 292 proteins in total with 95 novel interactions. Three 14-3-3ζ-interacting proteins-BAX, HSP70, and BAG3-were further confirmed by reciprocal coimmunoprecipitations and colocalization analysis. Our results therefore not only uncover a large number of novel 14-3-3ζ-associated proteins that possess a variety of cellular functions, but also provide new research directions for the study of the functions of 14-3-3ζ. This study also demonstrated that QUICK is a useful approach to detect specific protein-protein interactions with very high confidence and may have a wide range of applications in the investigation of protein complex interaction networks.

MicroRNA-dependent regulation of PTEN after arsenic trioxide treatment in bladder cancer cell line T24

Arsenic trioxide has shown remarkable biological activity against bladder cancer in some clinical studies. However, the mechanism of its action is unknown. Our aim was to find the relationship between miRNAs and arsenic trioxide treatment by using T24 human bladder carcinoma cells. By performing microRNA microarray and quantitative real-time PCR after ATO treatment, we found that expression levels of several miRNAs, in particular, miRNA-19a, were significantly decreased in T24 cell line. Furthermore, cell proliferation assay, flow cytometry analysis, prediction of miRNA targets, Western blot analysis, and luciferase reporter assay were performed to determine the role of mir-19a in affecting the biological behaviors of T24 cells. Several miRNAs were up-regulated or down-regulated in T24 cells treated with arsenic trioxide compared to their controls. If only changes above two folds were considered, two miRNAs were identified, miRNA-19a was down-regulated, while miRNA-222* was up-regulated. Among them, knockdown of miRNA-19a by anti-miRNA-19a transfection showed a positive therapeutic effect in bladder cancer cells by inhibiting cell growth and inducing cell apoptosis targeting PTEN through the PTEN/Akt pathway. Besides this, a synergy effect was detected between knockdown of miRNA-19a and arsenic trioxide. Arsenic trioxide altered miRNA expression profile in T24 cells. It seems miRNA-19a plays a critical role in the mechanism of arsenic trioxide treatment in bladder cancer. The synergy effect between miRNA-19a and arsenic trioxide that advocates targeting the mir-19a may represent a potential approach to enhance the efficacy and safety of ATO to treat bladder cancer by a decrease in dose.

Degrasyn potentiates the antitumor effects of bortezomib in mantle cell lymphoma cells in vitro and in vivo: therapeutic implications

Mantle cell lymphoma (MCL) is an aggressive histotype of B-cell non-Hodgkin lymphoma that has increased in incidence over the past few decades and is incurable, usually poorly responsive to standard chemotherapy combinations, and associated with poor prognoses. Discovering new therapeutic agents with low toxicity that produce better outcomes in patients with MCL is an ongoing challenge. Recent studies showed that degrasyn, a novel small-molecule inhibitor of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway, exerts antitumor activity in lymphoid tumors by inhibiting key growth and survival signaling (JAK/STAT) pathways. In the present study, we found that treatment of both typical and blastoid-variant MCL cells with degrasyn in combination with bortezomib resulted in synergistic growth inhibition and apoptosis induction in vitro. The apoptosis in these cells was correlated with the downregulation of constitutive NF-kappaB and phosphorylated STAT3 activation, leading to the inhibition of c-Myc, cyclin D1, and bcl-2 protein expression and the upregulation of bax protein expression. In vivo, degrasyn and bortezomib interacted to synergistically prevent tumor development and prolong survival durations in a xenotransplant severe combined immunodeficient mouse model of MCL. These findings suggest that agents such as degrasyn that can pharmacologically target constitutively expressed NF-kappaB and STAT3 in MCL cells may be useful therapeutic agents for MCL when administered together with bortezomib.

Synergistic antiproliferative effect of arsenic trioxide combined with bortezomib in HL60 cell line and primary blasts from patients affected by myeloproliferative disorders

Both arsenic trioxide (ATO) and bortezomib show separate antileukemic activity. With the purpose of evaluating whether the combination of ATO and bortezomib would be an option for patients with acute leukemia, we incubated HL60 leukemic cells with ATO alone and in combination with bortezomib. ATO and bortezomib cooperated to induce cell death and to inhibit proliferation and apoptosis in a synergistic way. The combined treatment resulted in a stronger activation of caspase 8 and 9, moderate activation of caspase 3, and increased expression of Fas and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-DR5 receptors. When bortezomib was added, some proapoptotic genes (CARD9, TRAIL) were upregulated, and some antiapoptotic genes (BCL2, BCL3, FLICE) were downregulated. When coincubated, approximately 80% of cells showed altered mitochondrial membrane permeability. Moreover, ATO alone and in combination with bortezomib abrogated DNA-binding activity of nuclear factor kappa beta (NF-kappaB). Gene expression assays showed that more deregulated genes were related to proliferation of leukocytes, tumorigenesis, control of cell cycle, hypoxia and oxidative stress, cytokines, PI3K-AKT, ERK-MAPK, EGF pathways, and ubiquitination. Finally, in three cases of acute myeloid leukemia, the addition of bortezomib to ATO significantly increased cytotoxicity. We conclude that the combination of bortezomib and ATO may be efficacious in the treatment of myeloid disorders.