Induction of heme oxygenase-1 by Na+-H+ exchanger 1 protein plays a crucial role in imatinib-resistant chronic myeloid leukemia cells

Intracellular Acidification in a Rat C6 Glioma Model following Cariporide Injection Investigated by CEST-MRI

Acidification of cancerous tissue induced pharmacologically may slow tumor growth and can be detected using magnetic resonance imaging. Numerous studies have shown that pharmacologically inhibiting specific transporters, such as the Na⁺/H⁺ exchanger 1 (NHE1), can alter glycolitic metabolism and affect tumor acidosis. The sodium proton exchanger inhibitor Cariporide can acidify U87MG gliomas in mice. This study aimed to determine whether Cariporide could acidify C6 glioma tumors in rats with an intact immune system. C6 glioma cells were implanted in the right brain hemisphere of ten rats. Chemical exchange saturation transfer (CEST) MRI (9.4T) was acquired on days 7-8 and 14-15 after implantation to measure in vivo tissue intracellular pH (pH_i) within the tumors and on the contralateral side. pH_i was basic relative to contralateral tissue at both time points assessed using the amine and amide concentration-independent detection (AACID) value. On day 14-15, measurements were made before and up to 160 min after Cariporide injection (N = 6). Twenty minutes after drug injection, the average AACID value in the tumor significantly increased by ∼6.4% compared to pre-injection, corresponding to 0.31 ± 0.20 lower pH_i, while in contralateral tissue, AACID value increased significantly by ∼4.3% compared to pre-injection, corresponding to 0.22 ± 0.19 lower pH_i. Control rats without tumors showed no changes following injection of Cariporide dissolved in 10% or 1% DMSO and diluted in PBS. This study demonstrates the sensitivity of CEST-based pH-weighted imaging for monitoring the response of tumors to pharmacologically induced acidification.

The prognostic and therapeutic potential of HO-1 in leukemia and MDS

BACKGROUND

Heme oxygenase-1 (HO-1), a heme-degrading enzyme, is proven to have anti-apoptotic effects in several malignancies. In addition, HO-1 is reported to cause chemoresistance and increase cell survival. Growing evidence indicates that HO-1 contributes to the course of hematological malignancies as well. Here, the expression pattern, prognostic value, and the effect of HO-1 targeting in HMs are discussed.

MAIN BODY

According to the recent literature, it was discovered that HO-1 is overexpressed in myelodysplastic syndromes (MDS), chronic myeloid leukemia (CML), acute myeloblastic leukemia (AML), and acute lymphoblastic leukemia (ALL) cells and is associated with high-risk disease. Furthermore, in addition to HO-1 expression by leukemic and MDS cells, CML, AML, and ALL leukemic stem cells express this protein as well, making it a potential target for eliminating minimal residual disease (MRD). Moreover, it was concluded that HO-1 induces tumor progression and prevents apoptosis through various pathways.

CONCLUSION

HO-1 has great potential in determining the prognosis of leukemia and MDS patients. HO-1 induces resistance to several chemotherapeutic agents as well as tyrosine kinase inhibitors and following its inhibition, chemo-sensitivity increases. Moreover, the exact role of HO-1 in Chronic Lymphocytic Leukemia (CLL) is yet unknown. While findings illustrate that MDS and other leukemic patients could benefit from HO-1 targeting. Future studies can help broaden our knowledge regarding the role of HO-1 in MDS and leukemia. Video abstract.

Extracellular Vesicles and Cell Pathways Involved in Cancer Chemoresistance

Chemoresistance is a pharmacological condition that allows transformed cells to maintain their proliferative phenotype in the presence of administered anticancer drugs. Recently, extracellular vesicles, including exosomes, have been identified as additional players responsible for the chemoresistance of cancer cells. These are nanovesicles that are released by almost all cell types in both physiological and pathological conditions and contain proteins and nucleic acids as molecular cargo. Extracellular vesicles released in the bloodstream reach recipient cells and confer them novel metabolic properties. Exosomes can foster chemoresistance by promoting prosurvival and antiapoptotic pathways, affecting cancer stem cells and immunotherapies, and stimulating drug efflux. In this context, a crucial role is played by membrane transporters belonging to ABC, SLC, and P-type pump families. These proteins are fundamental in cell metabolism and drug transport in either physiological or pathological conditions. In this review, different roles of extracellular vesicles in drug resistance of cancer cells will be explored.

Identification of Novel Anthracycline Resistance Genes and Their Inhibitors

Differentially expressed genes have been previously identified by us in multidrug-resistant tumor cells mainly resistant to doxorubicin. In the present study, we exemplarily focused on some of these genes to investigate their causative relationship with drug resistance. HMOX1, NEIL2, and PRKCA were overexpressed by lentiviral-plasmid-based transfection of HEK293 cells. An in silico drug repurposing approach was applied using virtual screening and molecular docking of FDA-approved drugs to identify inhibitors of these new drug-resistant genes. Overexpression of the selected genes conferred resistance to doxorubicin and daunorubicin but not to vincristine, docetaxel, and cisplatin, indicating the involvement of these genes in resistance to anthracyclines but not to a broader MDR phenotype. Using virtual drug screening and molecular docking analyses, we identified FDA-approved compounds (conivaptan, bexarotene, and desloratadine) that were interacting with HMOX1 and PRKCA at even stronger binding affinities than 1-(adamantan-1-yl)-2-(1H-imidazol-1-yl)ethenone and ellagic acid as known inhibitors of HMOX1 and PRKCA, respectively. Conivaptan treatment increased doxorubicin sensitivity of both HMOX1- and PRKCA-transfected cell lines. Bexarotene treatment had a comparable doxorubicin-sensitizing effect in HMOX1-transfected cells and desloratadine in PRKCA-transfected cells. Novel drug resistance mechanisms independent of ABC transporters have been identified that contribute to anthracycline resistance in MDR cells.

PKC-β/Alox5 axis activation promotes Bcr-Abl-independent TKI-resistance in chronic myeloid leukemia

Bcr-Abl independent resistance to tyrosine kinase inhibitor (TKI) is a crucial factor lead to relapse or acute leukemia transformation in chronic myeloid leukemia (CML). However, its mechanism is still unclear. Herein, we found that of nine common protein kinases C (PKCs), PKC-β overexpression was significantly related with TKI resistance. Blockage of its expression in CD34+ cells and CML cell lines increased sensitivity to imatinib. Then, eighty-four leukemia related genes were compared between TKI-resistant CML cell lines with PKC-β silenced or not. Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that Arachidonate 5-lipoxygenase (Alox5) and its relative pathway mainly participated in the resistance induced by PKC-β overexpression. It's also observed that Alox5 was increased not only in bone marrow biopsy but also in CD34⁺ cells derived from IM-resistant CML patients. The signaling pathway exploration indicated that ERK1/2 pathway mediates Alox5 upregulation by PKC-β. Meanwhile, we also proved that Alox5 induces TKI-insensitivity in CML through inactivation of PTEN. In vivo experiment, PKC-β elective inhibitor LY333531 prolonged survival time in CML-PDX mice model. In conclusion, targeted on PKC-β overexpression might be a novel therapy mechanism to overcome TKI-resistance in CML.

Adipose Mesenchymal Stem Cell-Derived Exosomal microRNA-1236 Reduces Resistance of Breast Cancer Cells to Cisplatin by Suppressing SLC9A1 and the Wnt/β-Catenin Signaling

BACKGROUND

Emerging evidence has noted the versatile functions of mesenchymal stem cell-derived exosomes (MSC-Exos) in cancer control. This work aims to probe to function of adipose MSC-Exos (adMSC-Exos) in drug-resistance of breast cancer (BC) cells to cisplatin (DDP) and the molecules involved.

METHODS

Parental and DDP-resistant BC cell lines MCF-7 and MDA-MB-231 were used. All cells were pre-treated with adMSC-Exos. Then, the viability and apoptosis of cells after DDP treatment were determined. Differentially expressed miRNAs after adMSC-exo treatment were screened out. Rescue experiments were conducted by pre-transfecting miR-1236 inhibitor into adMSCs, and the role of miR-1236 in DDP sensitivity was determined. Targeting mRNAs of miR-1236 were predicted by bioinformatics analysis. Altered SLC9A1 expression was administrated to evaluate its function in DDP resistance.

RESULTS

The adMSC-Exos notably increased the sensitivity of either parental or DDP-resistant BC cells to DDP. SLC9A1 was notably highly expressed in DDP-resistant cells but inhibited following adMSC-exo administration. Importantly, miR-1236, which could directly bind to SLC9A1 and suppress its expression, was confirmed as an enriched miRNA in adMSC-Exos. Either inhibition of miR-1236 or upregulation of SLC9A1 blocked the pro-sensitize roles of adMSC-Exos. In addition, the Wnt/β-catenin pathway activity was suppressed by adMSC-Exos but recovered by SLC9A1.

CONCLUSION

This study evidenced that adMSC-Exos carry miR-1236 to increase sensitivity of BC cells to DDP with the involvement of SLC9A1 downregulation and Wnt/β-catenin inactivation. This finding may offer novel insights into treatment for drug-resistant BC.

Pharmacogenetics in the treatment of gastrointestinal stromal tumors - an updated review

INTRODUCTION

Gastrointestinal stromal tumors (GIST) are the best example of a targeted therapy in solid tumors. The introduction of tyrosine kinase inhibitors (TKIs) deeply improved the prognosis of this tumor. However, a degree of inter-patient variability is still reported in response rates and pharmacogenetics may play an important role in the final clinical outcome.

AREAS COVERED

In this review, the authors provide an updated overview of the pharmacogenetic literature analyzing the role of polymorphisms in both GIST treatment efficacy and toxicity.

EXPERT OPINION

Besides the primary role of somatic DNA in dictating the clinical response to TKIs, several polymorphisms influencing their pharmacokinetics and pharmacodynamics have been identified as being potentially involved. In the last 10 years, many potential biomarkers have been proposed to predict clinical response and toxicity after TKI administration. However, the evidence is still too limited to promote a clinical translation. To date, the somatic mutational status represents the main player in clinical response to TKIs in GIST treatment; however, pharmacogenetics could still explain the degree of inter-patient variability observed in GIST patients. A combination of different theoretical approaches, experimental model systems, and statistical methods is clearly needed, in order to translate pharmacogenetics to clinical practice in the near future.

Widespread expression of Sonic hedgehog (Shh) and Nrf2 in patients treated with cisplatin predicts outcome in resected tumors and are potential therapeutic targets for HPV-negative head and neck cancer

Background:

Sonic hedgehog (Shh) and Nrf2 play a critical role in chemotherapeutic resistance. These two genes have been found to be dysregulated in head and neck squamous cell carcinomas (HNSCC). The purpose of this study was to analyze the expression, function and clinical prognostic relationship of Shh and Nrf2 in HNSCC in the context of therapeutic resistance and cancer stem cells (CSCs).

Methods:

We analyzed a cohort of patients with HNSCC to identify potential therapeutic biomarkers correlating with overall survival (OS) as well as disease-free survival (DFS) from our own data and validated these results using The Cancer Genome Atlas dataset. Expression of Shh and Nrf2 was knocked down by siRNA and cell growth, sphere growth and chemotherapeutic resistance were evaluated.

Results:

Widespread abundant expression of Shh and Nrf2 proteins were associated with shorter OS and DFS. The combination of Shh and Nrf2 expression levels was found to be a significant predictor of patient DFS. The tumor stromal index was correlated with Shh expression and inversely associated with shorter OS and DFS. Inhibition of Shh by siRNA or cyclopamine resulted in the attenuation of resistant CSC self-renewal, invasion, clonogenic growth and re-sensitization to the chemotherapeutic agents. Concomitant upregulation of Shh and Nrf2 proved to be an independent predictor of poor OS and DFS in patients with HNSCC.

Conclusions:

These findings suggest that Shh and Nrf2 could serve as therapeutic targets as well as promising dual prognostic therapeutic biomarkers for HNSCC.

Deletion of HO-1 blocks development of B lymphocytes in mice

B lymphocytes, a key cluster of cells composing the immune system, can protect against abnormal biological factors. Heme oxygenase-1 (HO-1) plays important roles in cell proliferation and immune regulation, but its effects on the development and growth of B lymphocytes are still unknown. Herein, the count of B lymphocytes in HO-1 gene knockout (HO-1^+/-) mice was significantly lower than that of the HO-1 gene wild-type (HO-1^WT) mice. Meanwhile, the cell count of HO-1^+/- mice did not recover after irradiation for one week, due to the G0/G1 phase arrest of Pro-B cells and the augmented apoptosis of Pre-B cells. Up-regulation of HO-1 by lentivirus attenuated the Pro-B cell cycle arrest and Pre-B cell apoptosis. To understand the molecular mechanism by which HO-1 knockout blocked B lymphocyte development, protein-to-protein interaction network and Western blot were used. The PI3K/AKT signaling pathway mediated the regulatory effects of HO-1 on B lymphocytes. In conclusion, HO-1 is a crucial transcriptional repressor for B cell development.

Increased NHE1 expression is targeted by specific inhibitor cariporide to sensitize resistant breast cancer cells to doxorubicin in vitro and in vivo

Background

The Na⁺/H⁺ exchanger (NHE1) plays a crucial role in cancer cell proliferation and metastasis. However, the mechanism underlying chemotherapeutic resistance in cancer cells has not been completely elucidated. The NHE1 inhibitor cariporide has been demonstrated to inhibit human cancer cell lines. The goal of this study was to provide new sights into improved cancer cell chemosensitivity mediated by cariporide with activation of the apoptosis pathway.

Methods

The NHE1 expression levels were first evaluated using the online database Oncomine and were determined by RT-PCR and western blot in vitro and in vivo. Cell proliferation was assessed In vitro through a CCK-8 assay, and apoptosis was analyzed by flow cytometry. An in vivo analysis was performed in BALB/c nude mice, which were intraperitoneally injected with MCF-7/ADR cells.

Results

NHE1 levels were significantly higher in breast cancer tissue than adjacent tissue, as well as in resistant cancer cells compared to sensitive cells. Cariporide induced the apoptosis of MCF-7/ADR cells and was associated with the intracellular accumulation of doxorubicin and G0/G1 cell cycle arrest. Moreover, cariporide decreased MDR1 expression and activated cleaved caspase-3 and caspase-9, promoting caspase-independent apoptosis in vitro. In vivo, cariporide significantly improved doxorubicin sensitivity in a xenograft model, enhancing tumor growth attenuation and diminishing tumor volume.

Conclusions

Our results demonstrate that cariporide significantly facilitates the sensitivity of breast cancer to doxorubicin both in vitro and in vivo. This finding suggests that NHE1 may be a novel adjuvant therapeutic candidate for the treatment of resistant breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5397-7) contains supplementary material, which is available to authorized users.

Heme oxygenase-1 reduces the sensitivity to imatinib through nonselective activation of histone deacetylases in chronic myeloid leukemia

Resistance towards imatinib (IM) remains troublesome in treating many chronic myeloid leukemia (CML) patients. Heme oxygenase-1 (HO-1) is a key enzyme of antioxidative metabolism in association with cell resistance to apoptosis. Our previous studies have shown that overexpression of HO-1 resulted in resistance development to IM in CML cells, while the mechanism remains unclear. In the current study, the IM-resistant CML cells K562R indicated upregulation of some of the histone deacetylases (HDACs) compared with K562 cells. Therefore, we herein postulated HO-1 was associated with HDACs. Silencing HO-1 expression in K562R cells inhibited the expression of some HDACs, and the sensitivity to IM was increased. K562 cells transfected with HO-1 resisted IM and underwent obvious some HDACs. These findings related to the inhibitory effects of high HO-1 expression on the reactive oxygen species (ROS) signaling pathway that negatively regulated HDACs. Increased expression of HO-1 activated HDACs by inhibiting ROS production. In summary, HO-1, which is involved in the development of drug resistance in CML cells by regulating the expression of HDACs, is probably a novel target for improving CML therapy.

Targeting of heme oxygenase-1 attenuates the negative impact of Ikaros isoform 6 in adult BCR-ABL1-positive B-ALL

The correlation between Heme oxygenase-1 (HO-1) and dominant-negative Ikaros isoform 6 (IK6) is unclear. Firstly, we detected that IK6 existed in 20 of 42 (47.6%) adult BCR-ABL1-positive B-lineage acute lymphoblastic leukemia (BCR-ABL1-positive B-ALL) by using reverse transcribed polymerase chain reaction (PCR) and nucleotide sequencing. IK6-positive patients had an unfavorable outcome compared with IK6-negative ones. Further study showed that the level of HO-1 expression was higher in IK6-positive patients' samples than that in IK6-negative ones. And there was a strong correlation between the expression of IK6 and HO-1. The growth of primary CD34+ leukemic cells derived from our IK6-positive patients' pool was prohibited by silencing HO-1, further promoting their apoptosis. Furthermore, primary CD34+ leukemic cells derived from IK6-positive patients shown poor responses to imatinib in comparison with wild-type (IK1) patients, suggesting that the expression of IK6 resisted to imatinib in adult BCR-ABL1-positive B-ALL. Importantly, inhibition of HO-1 also increased their sensitivity to tyrosine kinase inhibitors (TKIs). Finally, we found that IK6 activated downstream STAT5, and HO-1 was one of the downstream target genes of STAT5. In conclusion, HO-1 is an essential survival factor in BCR-ABL1-positive B-ALL with IK6, and targeting HO-1 can attenuate the negative impact of IK6.

Crucial role of HO-1/IRF4-dependent apoptosis induced by panobinostat and lenalidomide in multiple myeloma

Inhibition of histone deacetylase (HDAC) is a promising therapeutic strategy for various hematologic cancers. Panobinostat has been approved for treating patients with multiple myeloma (MM) by the FDA. Since the mechanism for the resistance of panobinostat to MM remains elusive, we aimed to clarify this mechanism and the synergism of panobinostat with lenalidomide. The mRNA and protein of transcription factor IRF4 were overexpressed in CD138⁺ mononuclear cells from MM patients compared with in those from healthy donors. Given that direct IRF4 inhibitors are clinically unavailable, we intended to explore the mechanism by which IRF4 expression was regulated in MM. Heme oxygenase-1 (HO-1) promotes the growth and drug resistance of various malignant tumors, and its expression is positively correlated with IRF4 mRNA and protein expression levels. Herein, panobinostat induced acetylation of histone H3K9 and activation of caspase-3 in MM cells, being inversely correlated with the reduction of HO-1/IRF4/MYC protein levels. Adding Z-DEVD-FMK, a caspase-3 inhibitor, abolished the HO-1/IRF4 reduction by panobinostat alone or in combination with lenalidomide, suggesting that caspase-3-mediated HO-1/IRF4/MYC degradation occurred. Given that lenalidomide stabilized cereblon and facilitated IRF4 degradation in MM cells, we combined it with LBH589, an HDAC inhibitor. LBH589 and lenalidomide exerted synergistic effects, and LBH589 reversed the efficacy of lenalidomide on the resistance of CD138⁺ primary MM cells, in part due to simultaneous suppression of HO-1, IRF4 and MYC. The results provide an eligible therapeutic strategy for targeting MM depending on the IRF4 network and clinical testing of this drug combination in MM patients.

The Heme Oxygenase System in Hematological Malignancies

SIGNIFICANCE

Several lines of evidence suggest that hematological malignancies exhibit an altered redox balance homeostasis that can lead to the activation of various survival pathways that, in turn, lead to the progression of disease and chemoresistance. Among these pathways, the heme oxygenase-1 (HO-1) pathway is likely to play a major role. HO catalyzes the enzymatic degradation of heme with the simultaneous release of carbon monoxide (CO), ferrous iron (Fe²⁺), and biliverdin. This review focuses on the role of HO-1 in various hematological malignancies and the possibility of exploiting such targets to improve the outcome of well-established chemotherapeutic regimens. Recent Advances and Critical Issues: Interestingly, the inhibition of the expression of HO-1 (e.g., with siRNA) or HO activity (with competitive inhibitors) contributes to the increased efficacy of chemotherapy and improves the outcome in animal models. Furthermore, some hematological malignancies (e.g., chronic myeloid leukemia and multiple myeloma) have served to explore the non-canonical functions of HO-1, such as the association between nuclear compartmentalization and genetic instability and/or chemoresistance.

FUTURE DIRECTIONS

The HO system may serve as an important tool in the field of hematological malignancies because it can be exploited to counteract chemoresistance and to monitor the outcome of bone marrow transplants and may be an additional target for combined therapies. Antioxid. Redox Signal. 27, 363-377.

Cariporide Enhances the DNA Damage and Apoptosis in Acid-tolerable Malignant Mesothelioma H-2452 Cells

The Na+/H+ exchanger is responsible for maintaining the acidic tumor microenvironment through its promotion of the reabsorption of extracellular Na+ and the extrusion of intracellular H+. The resultant increase in the extracellular acidity contributes to the chemoresistance of malignant tumors. In this study, the chemosensitizing effects of cariporide, a potent Na+/H+-exchange inhibitor, were evaluated in human malignant mesothelioma H-2452 cells preadapted with lactic acid. A higher basal level of phosphorylated (p)-AKT protein was found in the acid-tolerable H-2452AcT cells compared with their parental acid-sensitive H-2452 cells. When introduced in H-2452AcT cells with a concentration that shows only a slight toxicity in H-2452 cells, cariporide exhibited growth-suppressive and apoptosis-promoting activities, as demonstrated by an increase in the cells with pyknotic and fragmented nuclei, annexin V-PE(+) staining, a sub-G0/G1 peak, and a G2/M phase-transition delay in the cell cycle. Preceding these changes, a cariporide-induced p-AKT down-regulation, a p53 up-regulation, an ROS accumulation, and the depolarization of the mitochondrial-membrane potential were observed. A pretreatment with the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 markedly augmented the DNA damage caused by the cariporide, as indicated by a much greater extent of comet tails and a tail moment with increased levels of the p-histone H2A.X, p-ATMSer1981, p-ATRSer428, p-CHK1Ser345, and p-CHK2Thr68, as well as a series of pro-apoptotic events. The data suggest that an inhibition of the PI3K/AKT signaling is necessary to enhance the cytotoxicity toward the acid-tolerable H-2452AcT cells, and it underlines the significance of proton-pump targeting as a potential therapeutic strategy to overcome the acidic-microenvironment-associated chemotherapeutic resistance.

Restoration of secreted frizzled-related protein 1 suppresses growth and increases cisplatin sensitivity in laryngeal carcinoma cells by downregulating NHE1

It has been documented that secreted frizzled-related protein 1 (SFRP1) is epigenetically silenced in laryngeal carcinoma. However, the function of SFRP1 in laryngeal carcinoma remains elusive. In this study, we performed gain-of-function studies to determine the roles of SFRP1 in laryngeal carcinoma growth, tumorigenesis, and cisplatin resistance. Laryngeal carcinoma cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC) and examined for SFRP1 expression. The effects of overexpression of SFRP1 on cell proliferation, colony formation, apoptosis, tumorigenesis, and cisplatin sensitivity were assessed. It was found that 5-aza-dC exposure significantly induced the expression of SFRP1 in both Hep-2 and SNU899 laryngeal carcinoma cells. Ectopic expression of SFRP1 significantly decreased cell proliferation and colony formation in vitro and retarded xenograft tumor growth in vivo. SFRP1-overexpressing Hep-2 cells displayed a higher percentage of apoptosis and enhancement of caspase-3 cleavage, which was coupled with loss of Δψm and increased release of cytochrome c from the mitochondria to the cytosol. Moreover, SFRP1 overexpression sensitized laryngeal carcinoma cells to cisplatin and decreased intracellular pH values. Mechanistically, SFRP1 inhibited the expression of Na+/H+ exchanger 1 (NHE1) and overexpression of NHE1 reversed the suppressive activity of SFRP1 on laryngeal carcinoma cells. In conclusion, we demonstrate that SFRP1 induces mitochondrial apoptosis and increases cisplatin sensitivity in laryngeal carcinoma cells via downregulation of NHE1. Delivery of SFRP1 may offer therapeutic benefits in the treatment of laryngeal carcinoma.

Silencing heme oxygenase-1 increases the sensitivity of ABC-DLBCL cells to histone deacetylase inhibitor in vitro and in vivo

Heme oxygenase-1 (HO-1) can promote tumor growth and reinforce the resistance of diffuse large B-cell lymphoma (DLBCL) cells to chemotherapeutic drug vincristine. We herein found that HO-1 protein expression was higher in high-risk DLBCL patients than in low-risk ones. Silencing HO-1 gene expression resisted vorinostat-induced apoptosis and arrested cell cycle in the G0/G1 phase of LY-10 cells. Western blot, co-immunoprecipitation and chromatin immunoprecipitation assays confirmed that the possible mechanisms may be increased cleaved caspase-3 protein expression, decreased phospho-histone deacetylase 3 protein expression, and activated histone acetylation of P27^Kip1 promoter. Moreover, silencing HO-1 gene expression enhanced vorinostat-induced tumor cell apoptosis, prolonged survival time and promoted P27^Kip1 protein expression in a xenograft mouse model.

In conclusion, HO-1 is a potential therapeutic target of DLBCL. The findings provide a valuable preclinical evidence for sensitizing DLBCL patients with poor prognosis to histone deacetylase inhibitors.

Translocation of heme oxygenase-1 contributes to imatinib resistance in chronic myelogenous leukemia

Heme oxygenase-1 (HO-1) degrades heme to bilirubin. In addition, it is upregulated in malignant disease and has been described as an important factor for cancer prognosis and therapy. Under physiological conditions HO-1 is anchored to the endoplasmic reticulum (ER). Under stress conditions HO-1 can be cleaved and subsequently translocates to the cytosol and nucleus.

In this study we systematically investigated the influence of HO-1's catabolic activity and subcellular localization on resistance against the tyrosine kinase inhibitor imatinib in leukemia cells by confocal laser scanning microscopy, hemoglobin synthesis experiments and cell viability assays. We created two types of monoclonal K562 cell lines stably transfected with GFP-tagged HO-1: cell lines expressing ER anchored HO-1 or anchorless HO-1. Since translocation of HO-1 disrupts the association with cytochrome P450 reductase, heme degrading activity was higher for ER anchored versus anchorless HO-1. Cell viability tests with increasing concentrations of imatinib showed IC50-values for all six cell lines with ER localized HO-1 that were similar to control cells. However, out of the seven cell lines with anchorless HO-1, two showed a statistically significant increase in the imatinib IC50 (19.76 μM and 12.35 μM versus 2.35 – 7.57 μM of sensitive cell lines) corresponding to plasma concentrations outside the therapeutic range.

We conclude that the presence of translocated HO-1 in the cytosol and nucleus supports imatinib resistance while it is not sufficient to cause imatinib resistance in every cell line. In contrast, an increase in ER anchored HO-1 with high heme degrading activity does not contribute to imatinib resistance.

Genomic and transcriptomic profiling of resistant CEM/ADR-5000 and sensitive CCRF-CEM leukaemia cells for unravelling the full complexity of multi-factorial multidrug resistance

We systematically characterised multifactorial multidrug resistance (MDR) in CEM/ADR5000 cells, a doxorubicin-resistant sub-line derived from drug-sensitive, parental CCRF-CEM cells developed in vitro. RNA sequencing and network analyses (Ingenuity Pathway Analysis) were performed. Chromosomal aberrations were identified by array-comparative genomic hybridisation (aCGH) and multicolour fluorescence in situ hybridisation (mFISH). Fifteen ATP-binding cassette transporters and numerous new genes were overexpressed in CEM/ADR5000 cells. The basic karyotype in CCRF-CEM cells consisted of 47, XX, der(5)t(5;14) (q35.33;q32.3), del(9) (p14.1), +20. CEM/ADR5000 cells acquired additional aberrations, including X-chromosome loss, 4q and 14q deletion, chromosome 7 inversion, balanced and unbalanced two and three way translocations: t(3;10), der(3)t(3;13), der(5)t(18;5;14), t(10;16), der(18)t(7;18), der(18)t(21;18;5), der(21;21;18;5) and der(22)t(9;22). CCRF-CEM consisted of two and CEM/ADR5000 of five major sub-clones, indicating genetic tumor heterogeneity. Loss of 3q27.1 in CEM/ADR5000 caused down-regulation of ABCC5 and ABCF3 expression, Xq28 loss down-regulated ABCD1 expression. ABCB1, the most well-known MDR gene, was 448-fold up-regulated due to 7q21.12 amplification. In addition to well-known drug resistance genes, numerous novel genes and genomic aberrations were identified. Transcriptomics and genetics in CEM/AD5000 cells unravelled a range of MDR mechanisms, which is much more complex than estimated thus far. This may have important implications for future treatment strategies.

Novel interactions between erythroblast macrophage protein and cell migration

Erythroblast macrophage protein is a novel protein known to mediate attachment of erythroid cells to macrophages to form erythroblastic islands in bone marrow during erythropoiesis. Emp-null macrophages are small with round morphologies, and lack cytoplasmic projections which imply immature structure. The role of Emp in macrophage development and function is not fully elucidated. Macrophages perform varied functions (e.g. homeostasis, erythropoiesis), and are implicated in numerous pathophysiological conditions such as cellular malignancy. The objective of the current study is to investigate the interaction of Emp with cytoskeletal- and cell migration-associated proteins involved in macrophage functions. A short hairpin RNA lentiviral system was use to down-regulate the expression of Emp in macrophage cells. A cell migration assay revealed that the relocation of macrophages was significantly inhibited when Emp expression was decreased. To further analyze changes in gene expression related to cell motility, PCR array was performed by down-regulating Emp expression. The results indicated that expression of mitogen-activated protein kinase 1 and thymoma viral proto-oncogene 1 were significantly higher when Emp was down-regulated. The results implicate Emp in abnormal cell motility, thus, warrants to assess its role in cancer where tumor cell motility is required for invasion and metastasis.

Overexpression of heme oxygenase-1 induced by constitutively activated NF-κB as a potential therapeutic target for activated B-cell-like diffuse large B-cell lymphoma

There is an urgent requirement for a new therapeutic target for activated B-cell-like lymphoma (ABC-DLBCL), which is known to have dismal outcome and constitutive activation of NF-κB. Heme oxygenase-1 (HO-1) can inhibit apoptosis and promote proliferation in many cancers. To our knowledge, no studies have been performed on the correlation between HO-1 and DLBCL. In this study, immunohistochemical analysis of 31 tumor tissues from DLBCL patients [20 of ABC subtype and 11 of germinal center B-cell-like (GCB) subtype] and 11 normal lymph nodes revealed that HO-1 overexpression was characteristic of ABC-DLBCL. In addition, HO-1 mRNA expression levels were consistent with the immunohistochemistry results. High levels of HO-1 expression were significantly correlated with the involvement of more than 1 extranodal site (p=0.025), with a high positivity rate of Ki-67 (p<0.01). Similar to its anti-apoptotic role in other malignancies, HO-1 upregulation suppressed apoptosis of the ABC-DLBCL cell line OCI-ly10, whereas its downregulation sensitized the tumor cells to chemotherapeutic drugs. Further study demonstrated that the HO-1 overexpression was mediated by constitutively activated NF-κB which together played an anti-apoptotic role in ABC-DLBCL. Combination of the NF-κB inhibitor Bay11‑7082 and the lentivirus vector Lenti-siHO-1 significantly decreased HO-1 protein expression and increased apoptosis in OCI-ly10 cells. However, in GCB-DLBCL cells with low levels of NF-κB expression, the TNF-α-mediated activation of NF-κB leading to HO-1 upregulation rescued the cells from apoptosis caused by HO-1 silencing. These results indicated that HO-1 can be a potential target for the treatment of ABC-DLBCL.

Heme oxygenase-1 contributes to imatinib resistance by promoting autophagy in chronic myeloid leukemia through disrupting the mTOR signaling pathway

Heme oxygenase-1 (HO-1) has been verified to play an important role in imatinib (IM)-resistant chronic myeloid leukemia (CML) cells, but the mechanism remains unclear. In drug resistant CML cells, HO-1 expression abnormally increased and that of autophagy-related protein LC-3I/II also increased, so we herein postulated HO-1 was associated with autophagy. HO-1 expressions in IM-sensitive/resistant K562/K562R cells were regulated through lentiviral mediation. K562 cells transfected with HO-1 resisted IM and underwent obvious autophagy. After HO-1 expression was silenced in K562R cells, autophagy was inhibited and the sensitivity to IM was increased. The findings were related with the inhibitory effects of high HO-1 expression on the mTOR signaling pathway that negatively regulated autophagy. High HO-1 expression promoted autophagy by inhibiting mTOR. Similar to the cell line results, mononuclear cells of IM-resistant CML patients became significantly sensitive to IM when HO-1 expression was inhibited. In summary, HO-1, which is involved in the development of chemoresistance in leukemia cells by regulating autophagy, may be a novel target for improving leukemia therapy.

Detection of oxidative stress biomarkers in myricetin treated red blood cells

Effect of myricetin on RBC membrane enzymes (Na⁺, K⁺-ATPase and Ca²⁺-ATPase) and Na⁺, H⁺exchanger.

The Nrf2/HO-1 Axis in Cancer Cell Growth and Chemoresistance

The transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2), acts as a sensor of oxidative or electrophilic stresses and plays a pivotal role in redox homeostasis. Oxidative or electrophilic agents cause a conformational change in the Nrf2 inhibitory protein Keap1 inducing the nuclear translocation of the transcription factor which, through its binding to the antioxidant/electrophilic response element (ARE/EpRE), regulates the expression of antioxidant and detoxifying genes such as heme oxygenase 1 (HO-1). Nrf2 and HO-1 are frequently upregulated in different types of tumours and correlate with tumour progression, aggressiveness, resistance to therapy, and poor prognosis. This review focuses on the Nrf2/HO-1 stress response mechanism as a promising target for anticancer treatment which is able to overcome resistance to therapies.