Antiapoptotic effect of haem oxygenase-1 induced by nitric oxide in experimental solid tumour

HSP32 (HO-1) inhibitor, copoly(styrene-maleic acid)-zinc protoporphyrin IX, a water-soluble micelle as anticancer agent: In vitro and in vivo anticancer effect

We reported previously the antitumor effect of heme oxygenase-1 (HO-1) inhibition by zinc protoporphyrin IX (ZnPP). ZnPP per se is poorly water soluble and thus cannot be used as anticancer chemotherapeutic. Subsequently, we developed water-soluble micelles of ZnPP using styrene-maleic acid copolymer (SMA), which encapsulated ZnPP (SMA-ZnPP). In this report, the in vitro and in vivo therapeutic effects of SMA-ZnPP are described. In vitro experiments using 11 cultured tumor cell lines and six normal cell lines revealed a remarkable cytotoxicity of SMA-ZnPP against various tumor cells; average IC(50) is about 11.1 μM, whereas the IC(50) to various normal cells is significantly higher, that is, more than 50 μM. In the pharmacokinetic study, we found that SMA-ZnPP predominantly accumulated in the liver tissue after i.v. injection, suggesting its applicability for liver cancer. As expected, a remarkable antitumor effect was achieved in the VX-2 tumor model in the liver of rabbit that is known as one the most difficult tumor models to cure. Antitumor effect was also observed in murine tumor xenograft, that is, B16 melanoma and Meth A fibrosarcoma. Meanwhile, no apparent side effects were found even at the dose of ∼7 times higher concentration of therapeutics dose. These findings suggest a potential of SMA-ZnPP as a tool for anticancer therapy toward clinical development, whereas further investigations are warranted.

Novel insights into the vasoprotective role of heme oxygenase-1

Cardiovascular risk factors contribute to enhanced oxidative stress which leads to endothelial dysfunction. These events trigger platelet activation and their interaction with leukocytes and endothelial cells, thus contributing to the induction of chronic inflammatory processes at the vascular wall and to the development of atherosclerotic lesions and atherothrombosis. In this scenario, endogenous antioxidant pathways are induced to restrain the development of vascular disease. In the present paper, we will discuss the role of heme oxygenase (HO)-1 which is an enzyme of the heme catabolism and cleaves heme to form biliverdin and carbon monoxide (CO). Biliverdin is reduced enzymatically to the potent antioxidant bilirubin. Recent evidence supports the involvement of HO-1 in the antioxidant and antiinflammatory effect of cyclooxygenase(COX)-2-dependent prostacyclin in the vasculature. Moreover, the role of HO-1 in estrogen vasoprotection is emerging. Finally, possible strategies to develop novel therapeutics against cardiovascular disease by targeting the induction of HO-1 will be discussed.

Involvement of heme oxygenase-1 in Korean colon cancer

Heme oxygenase-1 (HO-1) catabolizes heme into carbon monoxide, biliverdin, and free iron which mediate its protective effect against oxidative stress. The aim of the present study was to determine the expression level and activity of HO-1 in Korean colon cancer tissues and cell lines. HO-1 protein expression was higher (>1.5-fold) in tumor tissues than in adjacent normal tissues in 14 of 20 colon cancer patients, and HO-1 protein expression was closely correlated with HO-1 enzyme activity in cancer tissues. Immunohistochemical data confirmed that HO-1 protein was expressed at a higher level in colon cancer tissues than in normal mucosa. Furthermore, HO-1 mRNA and protein expression and enzyme activity were higher in the colon cancer cell lines Caco-2, SNU-407, SNU-1033, HT-29, and SW-403 than in the normal fetal human colon cell line FHC. Treatment with the HO-1 inhibitor zinc protoporphyrin decreased the viability of colon cancer cell lines. These data indicate that HO-1 may serve as a clinically useful biomarker of colon cancer and as a target for anticolon cancer drugs.

Carbon monoxide, generated by heme oxygenase-1, mediates the enhanced permeability and retention effect in solid tumors

The enhanced permeability and retention (EPR) effect is a unique pathophysiological phenomenon of solid tumors that sees biocompatible macromolecules (>40 kDa) accumulate selectively in the tumor. Various factors have been implicated in this effect. Herein, we report that heme oxygenase-1 (HO-1; also known as heat shock protein 32) significantly increases vascular permeability and thus macromolecular drug accumulation in tumors. Intradermal injection of recombinant HO-1 in mice, followed by i.v. administration of a macromolecular Evans blue-albumin complex, resulted in dose-dependent extravasation of Evans blue-albumin at the HO-1 injection site. Almost no extravasation was detected when inactivated HO-1 or a carbon monoxide (CO) scavenger was injected instead. Because HO-1 generates CO, these data imply that CO plays a key role in vascular leakage. This is supported by results obtained after intratumoral administration of a CO-releasing agent (tricarbonyldichlororuthenium(II) dimer) in the same experimental setting, specifically dose-dependent increases in vascular permeability plus augmented tumor blood flow. In addition, induction of HO-1 in tumors by the water-soluble macromolecular HO-1 inducer pegylated hemin significantly increased tumor blood flow and Evans blue-albumin accumulation in tumors. These findings suggest that HO-1 and/or CO are important mediators of the EPR effect. Thus, anticancer chemotherapy using macromolecular drugs may be improved by combination with an HO-1 inducer, such as pegylated hemin, via an enhanced EPR effect.

Effects of heme oxygenase-1 on induction and development of chemically induced squamous cell carcinoma in mice

Heme oxygenase-1 (HO-1) is an antioxidative and cytoprotective enzyme, which may protect neoplastic cells against anticancer therapies, thereby promoting the progression of growing tumors. Our aim was to investigate the role of HO-1 in cancer induction. Experiments were performed in HO-1(+/+), HO-1(+/-), and HO-1(-/-) mice subjected to chemical induction of squamous cell carcinoma with 7,12-dimethylbenz[a]anthracene and phorbol 12-myristate 13-acetate. Measurements of cytoprotective genes in the livers evidenced systemic oxidative stress in the mice of all the HO-1 genotypes. Carcinogen-induced lesions appeared earlier in HO-1(-/-) and HO-1(+/-) than in wild-type animals. They also contained much higher concentrations of vascular endothelial growth factor and keratinocyte chemoattractant, but lower levels of tumor necrosis factor-α and interleukin-12. Furthermore, tumors grew much larger in HO-1 knockouts than in the other groups, which was accompanied by an increased rate of animal mortality. However, pathomorphological analysis indicated that HO-1(-/-) lesions were mainly large but benign papillomas. In contrast, in mice expressing HO-1, most lesions displayed dysplastic features and developed to invasive carcinoma. Thus, HO-1 may protect healthy tissues against carcinogen-induced injury, but in already growing tumors it seems to favor their progression toward more malignant forms.

Simvastatin induces the expression of hemeoxygenase-1 against ischemia-reperfusion injury on the testes in rats

We evaluate the protective role of simvastatin-induced HO-1 in remote preconditioning against testis ischemia-reperfusion (IR) injury in vivo. Simvastatin was intraperitoneally (i.p.) injected 24 h before IR injury. Testis was occluded in the right testis for 40 min and followed by 30 min of reperfusion to induce IR injury. Tin protoporphyrin (Snpp), a competitive inhibitor of hemeoxygenase, was i.p. injected 1 h before the IR injury in separate groups of rats. The rat testes were harvested 24 h later. Induction of HO-1 expression by simvastatin was significantly increased at 24 and 48 h. Rats pre-treated with simvastatin showed higher expression of HO-1 protein by Western blotting and immunohistochemistry (IHC), and presented lower caspases-3 activity by caspase-3 activity assay. TUNEL staining analysis revealed simvastatin pretreatment significantly reduced IR induced cellular apoptosis. Contrarily, the simvastatin-induced cytoprotective effect was entirely abolished by administrations of Snpp. Further, lower caspase-3 activities were also noted in simvastatin plus Snpp (SS) group than the control plus Snpp (CS) group. After IR injury, eNOS immunoreactivity was markedly increased in the germ cell and Leydig cell of testicular tissues. Pretreatment of simvastatin significantly decreased eNOS immunoreactivity in the germ cell of the tubules in the rat testes. In conclusion, we suggest HO-1 plays a protective role in IR-induced injury in the testes of rats.

Heme oxygenase and carbon monoxide as an immunotherapeutic approach in transplantation and cancer

Heme oxygenases (HOs) are the rate-limiting intracellular enzymes that degrade heme into carbon monoxide (CO), biliverdin and free divalent iron. Among HOs, HO-1 is the only isoform that is highly inducible in response to numerous stress factors and proinflammatory cytokines. This enzyme has shown cytoprotective, antioxidant and anti-inflammatory properties. Moreover, HO-1 and, in particular, CO also have tolerogenic actions in adaptive immune responses. HO-1 can provide immunosuppression through its expression by regulatory T cells or antigen-presenting cells. The physiological importance of HO-1 has been demonstrated in both mice and humans, and modulation of HO-1 expression has therapeutic effects in a variety of disorders involving inflammation and immune responses, including organ transplantation and cancer. Consistently, upregulation of the HO-1 pathway has a significant protective effect against spontaneous or induced autoimmune diseases, allergy and can be beneficial to graft survival. However, HO-1 may also play a role in tumorigenesis by lowering antitumor innate immune responses that control tumor growth or reduce tumor expansion. Thus, controlling HO-1 expression may be of great interest in immune intervention protocols where tolerance is desirable, such as in transplantation, or where enhanced immunogenicity is needed in the case of cancer.

Enhancement of parthenolide-induced apoptosis by a PKC-alpha inhibition through heme oxygenase-1 blockage in cholangiocarcinoma cells

Cholangiocarcinoma (CC) is a chemoresistant intrahepatic bile duct carcinoma with a poor prognosis. The aims of this study were to identify molecular pathways that enhance sesquiterpene lactone parthenolide (PTL)-induced anticancer effects on CC cells. The effects of PTL on apoptosis and hemoxygenase-1 (HO-1) induction were examined in CC cell lines. The enhancement of PTL-mediated apoptosis by modulation of HO-1 expression and the mechanisms involved were also examined in an in vitro cell system. Low PTL concentrations (5 to 10 microM) led to Nrf2-dependent HO-1 induction, which attenuated the apoptogenic effect of PTL in Choi-CK and SCK cells. PTL-mediated apoptosis was enhanced by the protein kinase C-alpha inhibitor Ro317549 (Ro) through inhibition of expression and nuclear translocation of Nrf2, resulting in blockage of HO-1 expression. Finally, HO-1 silencing resulted in enhancement of apoptotic cell death in CC cells. The combination of PTL and Ro efficiently improved tumor growth inhibition compared to treatment with either agent alone in an in vivo subcutaneous tumor model. In conclusion, the modulation of HO-1 expression substantially improved the anticancer effect of PTL. The combination of PTL and Ro could prove to be a valuable chemotherapeutic strategy for CC.

Combination of PDT and inhibitor treatment affects melanoma cells and spares keratinocytes

Photodynamic therapy (PDT) is a potential tool in cancer treatment. Today this therapy is established among others for the treatment of nonmelanoma skin cancer. However, the more dangerous skin cancer--the melanoma--still has to be removed by surgery. Therefore, we investigated the effects of PDT and additional administration of heme oxygenase I (HO-I) and poly(ADP-ribose) polymerase (PARP) inhibitors on the treatment of melanoma cells in comparison to nonmalignant keratinocytes. Therefore, cocultures were established with WM451LU melanoma cells and HaCaT keratinocytes. In the coculture some 65% melanoma cells and 35% HaCaT cells were present before PDT, whereas after PDT the proportion was 41% melanoma cells and 59% HaCaT cells. Combination of both inhibitors improves these results to only 16% melanoma cells and 84% HaCaT cells. PDT is, therefore, a potent skin cancer treatment, which might also be interesting for melanoma treatment. The cytotoxic effects of PDT are largely mediated by ROS. Addition of HO-I and PARP inhibitors could improve the efficiency of photodynamic treatment.

Nucleotides function as endogenous chemical sensors for oxidative stress signaling

Oxidized and nitrated nucleotides including 8-oxogunanine and 8-nitroguanine derivatives such as 8-nitroguanosine 3',5'-cyclic monophosphate were generated by reactive nitrogen oxides and reactive oxygen species in cultured cells and in tissues. 8-oxoguanine and 8-nitroguanine in DNA and RNA are potentially mutagenic, and the former also induces cell death. Some derivative, 8-nitroguanosine 3',5'-cyclic monophosphate a major nitrated guanine nucleotide, was identified as a novel second messenger. Surprisingly, the amount of 8-nitroguanosine 3',5'-cyclic monophosphate generated was found to be higher than that of guanosine 3',5'-cyclic monophosphate in cells expressing inducible nitric oxide synthase. More important, 8-nitroguanosine 3',5'-cyclic monophosphate is electrophilic and reacted efficiently with sulfhydryls of proteins to produce a novel posttranslational modification (named S-guanylation) via guanosine 3',5'-cyclic monophosphate adduction. For example, 8-nitroguanosine 3',5'-cyclic monophosphate-induced S-guanylation of Kelch-like ECH-associated protein 1 led to NF-E2-related factor activation and induction of antioxidant enzymes. 8-nitroguanosine 3',5'-cyclic monophosphate may thus protect cells against oxidative stress-related cytotoxicity. Therefore, although chemically modified nucleotides produced via oxidative and nitrative stress are regarded simply as endogenous mutagens, the endogenous nucleotides stored in cells per se may serve functionally as a sensing mechanism for reactive nitrogen oxides and oxygen species to induce cellular adaptive responses to oxidative stress.

Heme induces DNA damage and hyperproliferation of colonic epithelial cells via hydrogen peroxide produced by heme oxygenase: a possible mechanism of heme-induced colon cancer

Epidemiological and animal model studies have suggested that high intake of heme, present in red meat, is associated with an increased risk of colon cancer. However, the mechanisms underlying this association are not clear. This study aimed to investigate whether heme induces DNA damage and cell proliferation of colonic epithelial cells via hydrogen peroxide produced by heme oxygenase (HO). We examined the effects of zinc protoporphyrin (ZnPP; a HO inhibitor) and catalase on DNA damage, cell proliferation, and IL-8 production induced by the addition of hemin (1-10 microM) to human colonic epithelial Caco-2 cells. DNA damage was determined with a comet assay, and cell proliferation was evaluated with 5-bromo-2'-deoxyuridine incorporation assay. Both ZnPP and exogenous catalase inhibited the hemin-induced DNA damage and cell hyperproliferation dose-dependently. IL-8 messenger RNA expression and IL-8 production in the epithelial cells increased following the hemin treatment, but the production was inhibited by ZnPP and catalase. These results indicate that hemin has genotoxic and hyperproliferative effects on Caco-2 cells by HO and hydrogen peroxide. The mechanism might explain why a high intake of heme is associated with increased risk of colon cancer.

Neuroglobin overexpression in cultured human neuronal cells protects against hydrogen peroxide insult via activating phosphoinositide-3 kinase and opening the mitochondrial K(ATP) channel

Cultured neurons tolerate low H(2)O(2) concentrations (< or =50 microM) through the activity of constitutive antioxidant response elements (ARE). At H(2)O(2) levels (> or =100 microM), neurons increase expression of the gene encoding for inducible hemoxygenase-1 while superoxide dismutase-2 and catalase remain unchanged. Despite this adaptive response, the endogenous antioxidant systems are overwhelmed, leading to decreased viability. Elevating the neuronal cell content of human neuroglobin (Ngb) prior to insult with 100 or 200 microM H(2)O(2) enhanced cell viability and this resulted in a significant decrease in oxidative stress and an increase in the intracellular ATP concentration, whereas in parental cells exposed to the same H(2)O(2)-insult, oxidative stress and ATP increased and decreased, respectively. The mechanism for this increase in ATP involves sustained activation of the mito-K(ATP) channel and an increase in phosphoinositide-3 kinase (PI3K)-mediated phosphorylation of Akt. Pharmacological inhibitors directed toward PI3K (wortmannin and LY294002), or the mito-K(ATP) channel (glybenclamide) inhibited the H(2)O(2)-mediated increase in ATP in cells overexpressing human Ngb and consequently cell viability decreased. Neuroglobin's ability to bolster the intracellular pool of ATP in response to added H(2)O(2) is central to the preservation of cytoskeletal integrity and cell viability.

The critical role of nitric oxide signaling, via protein S-guanylation and nitrated cyclic GMP, in the antioxidant adaptive response

A nitrated guanine nucleotide, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), is formed via nitric oxide (NO) and causes protein S-guanylation. However, intracellular 8-nitro-cGMP levels and mechanisms of formation of 8-nitro-cGMP and S-guanylation are yet to be identified. In this study, we precisely quantified NO-dependent formation of 8-nitro-cGMP in C6 glioma cells via liquid chromatography-tandem mass spectrometry. Treatment of cells with S-nitroso-N-acetylpenicillamine led to a rapid, transient increase in cGMP, after which 8-nitro-cGMP increased linearly up to a peak value comparable with that of cGMP at 24 h and declined thereafter. Markedly high levels (>40 microm) of 8-nitro-cGMP were also evident in C6 cells that had been stimulated to express inducible NO synthase with excessive NO production. The amount of 8-nitro-cGMP generated was comparable with or much higher than that of cGMP, whose production profile slightly preceded 8-nitro-cGMP formation in the activated inducible NO synthase-expressing cells. These unexpectedly large amounts of 8-nitro-cGMP suggest that GTP (a substrate of cGMP biosynthesis), rather than cGMP per se, may undergo guanine nitration. Also, 8-nitro-cGMP caused S-guanylation of KEAP1 in cells, which led to Nrf2 activation and subsequent induction of antioxidant enzymes, including heme oxygenase-1; thus, 8-nitro-cGMP protected cells against cytotoxic effects of hydrogen peroxide. Proteomic analysis for endogenously modified KEAP1 with matrix-assisted laser desorption/ionization time-of-flight-tandem mass spectrometry revealed that 8-nitro-cGMP S-guanylated the Cys(434) of KEAP1. The present report is therefore the first substantial corroboration of the biological significance of cellular 8-nitro-cGMP formation and potential roles of 8-nitro-cGMP in the Nrf2-dependent antioxidant response.

Cell signaling mediated by nitrated cyclic guanine nucleotide

We recently clarified the physiological formation of 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) and its critical roles in nitric oxide (NO) signal transductions. This discovery of 8-nitro-cGMP is the first demonstration of a nitrated cyclic nucleotide functioning as a new second messenger in mammals since the identification of cGMP more than 40 years ago. By means of chemical analyses, e.g., liquid chromatography-tandem mass spectrometry, we unequivocally identified 8-nitro-cGMP formation, which depended on NO production, in several types of cultured cells, including macrophages and glial cells. Most important, we previously showed that 8-nitro-cGMP as an electrophile reacted with particular sulfhydryls of proteins to generate a unique post-translational modification that we called protein S-guanylation. In fact, certain specific intracellular proteins, such as the redox-sensor protein Keap1, readily underwent S-guanylation induced by 8-nitro-cGMP. 8-Nitro-cGMP activated the Nrf2 signaling pathway by triggering dissociation of Keap1, via S-guanylation of its highly nucleophilic cysteine sulfhydryls. We also determined that S-guanylation of Keap1 was involved in cytoprotective actions of NO and 8-nitro-cGMP by inducing oxidative stress response genes such as heme oxygenase-1. Such unique chemical properties of 8-nitro-cGMP shed light on new areas of NO and cGMP signal transduction. Protein S-guanylation induced by 8-nitro-cGMP may thus have important implications in NO-related physiology and pathology, pharmaceutical chemistry, and development of therapeutics for many diseases.

Tumour growth following portal branch ligation in an experimental model of liver metastases

BACKGROUND

Portal branch ligation (PBL) is being used increasingly before hepatectomy for colorectal metastases. This study evaluated the effect of PBL on angiogenesis, growth factor expression and tumour growth in a mouse model of hepatic colorectal metastases.

METHODS

CT26.WT cells were implanted into the left liver lobe of BALB/c mice. Animals underwent PBL of the left liver lobe or sham treatment. Angiogenesis, microcirculation, growth factor expression, cell proliferation and tumour growth were studied over 14 and 21 days by intravital multifluorescence microscopy, laser Doppler flowmetry, immunohistochemistry and western blotting.

RESULTS

Left hilar blood flow and tumour microcirculation were significantly diminished during the first 7 days after PBL. This resulted in tumour volume being 20 per cent less than in sham controls by day 14. Subsequently, PBL-treated animals demonstrated recovery of left hilar blood flow and increased expression of hepatocyte growth factor and transforming growth factor alpha, associated with increased cell proliferation and acceleration of growth by day 21.

CONCLUSION

PBL initially reduced vascular perfusion and tumour growth, but this was followed by increased growth factor expression and cell proliferation. This resulted in delayed acceleration of tumour growth, which might explain the stimulated tumour growth observed occasionally after PBL.

Protein cysteine S-guanylation and electrophilic signal transduction by endogenous nitro-nucleotides

Nitric oxide (NO), a gaseous free radical that is synthesized in organisms by nitric oxide synthases, participates in a critical fashion in the regulation of diverse physiological functions such as vascular and neuronal signal transduction, host defense, and cell death regulation. Two major pathways of NO signaling involve production of the second messenger guanosine 3',5'-cyclic monophosphate (cGMP) and posttranslational modification (PTM) of redox-sensitive cysteine thiols of proteins. We recently clarified the physiological formation of 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) as the first demonstration, since the discovery of cGMP more than 40 years ago, of a new second messenger derived from cGMP in mammals. 8-Nitro-cGMP is electrophilic and reacts efficiently with sulfhydryls of proteins to produce a novel PTM via cGMP adduction, a process that we named protein S-guanylation. 8-Nitro-cGMP may regulate electrophilic signaling on the basis of its electrophilicity through induction of S-guanylation of redox sensor proteins. Examples include S-guanylation of the redox sensor protein Kelch-like ECH-associated protein 1 (Keap1), which leads to activation of NF-E2-related factor 2 (Nrf2)-dependent expression of antioxidant and cytoprotective genes. This S-guanylation-mediated activation of an antioxidant adaptive response may play an important role in cytoprotection during bacterial infections and oxidative stress. Identification of new redox-sensitive proteins as targets for S-guanylation may help development of novel therapeutics for oxidative stress- and inflammation-related disorders and vascular diseases as well as understanding of cellular protection against oxidative stress.

Inhibition of heme oxygenase-1 with an epidermal growth factor receptor inhibitor and cisplatin decreases proliferation of lung cancer A549 cells

Heme oxygenase-1 (HO-1) is induced by a variety of stress stimuli and by many antitumor agents. We investigated involvement of HO-1 in chemoresistance of cisplatin in human lung epithelial adenocarcinoma cell line, A549, which constitutively expressed HO-1. We found that treatment with cisplatin further augmented HO-1 expression, which was associated with activation of the epidermal growth factor receptor (EGFR) mediated signaling pathway and subsequent nuclear translocation of NF-kappaB. In concordance with the findings, treatment with EGFR-selective tyrosine kinase inhibitor (AG1478) or an Akt inhibitor, which interfere with the post-EGFR signaling pathway, suppressed cisplatin induced HO-1 expression. While either AG1478 or HO-1 siRNA alone did not alter cell viability of A549 cells, both agents significantly augmented cytotoxicity of cisplatin. The similar data also found in large cell carcinoma cell line, H460. Collectively, the results indicate that resistance to cisplatin in A549 cells is associated with HO-1 through EGFR mediated signaling pathway including activation of the PI3k/Akt and NF-kappaB systems. Our data also suggest that the chemosensitivity of A549 cells to cisplatin is restored by EGFR-selective tyrosine kinase inhibitor and an Akt inhibitor.

Isoliquiritigenin 2'-methyl ether induces growth inhibition and apoptosis in oral cancer cells via heme oxygenase-1

We previously reported that a chloroform extract of Caesalpinia sappan L. induces apoptosis in oral cancer cells but not in normal epithelial cell lines. In the present study, we explored the effects of a single compound isolated from C. sappan heartwood, isoliquiritigenin 2'-methyl ether (ILME), on cultured primary and metastatic oral cancer cell lines using MTT assays, fluorescence microscopy, flow cytometry, and Western blotting. ILME inhibited the growth of the oral cancer cells in a time- and dose-dependent manner. The major mechanism of growth inhibition was apoptosis induction, as shown by flow cytometric analysis of sub-G(1)-phase arrest and by annexin V-FITC and propidium iodide staining. ILME time-dependently activated NF-kappaB transcription factors, phospholated the MAP kinases JNK (c-Jun N-terminal kinase) and ERK (extracellular signal-regulated kinase). Furthermore, ILME treatment upregulated HO-1 expression though activation of Nrf2 (NF-E2-related factor 2) pathway, and induced the expression of heme oxygenase-1 (HO-1). Tin protoporphyrin, an HO-1 inhibitor, dose-dependently attenuated the growth-inhibitory effect of ILME and blocked ILME-induced expression of the p21 and p53 cell cycle-regulatory proteins. These results provide the first evidence that the anti-oral cancer effects of ILME may involve a mechanism in which HO-1 is upregulated via a pathway involving MAP kinases, NF-kappaB, and Nrf2. Thus, ILME could be considered to be a potential chemotherapeutic target for anti-oral cancer treatment strategies.

Heme oxygenase-1 and its metabolites affect pancreatic tumor growth in vivo

Background

Pancreatic cancer (PaCa) is a fatal human cancer due to its exceptional resistance to all current anticancer therapies. The cytoprotective enzyme heme oxygenase-1 (HO-1) is significantly overexpressed in PaCa and seems to play an important role in cancer resistance to anticancer treatment. The inhibition of HO-1 sensitized PaCa cells to chemo- and radiotherapy in vitro.

Therefore, we investigated the effects of HO-1 and its metabolites biliverdin, carbon monoxide and iron on PaCa cells.

PaCa cell lines with divergent HO-1 expression patterns were used in a murine orthotopic cancer model. HO-1 expression and activity was regulated by zinc (inhibition) and cobalt (induction) protoporphyrin. Furthermore, the influence of cellular HO-1 levels and its metabolites on effects of standard chemotherapy with gemcitabine was tested in vivo and in vitro.

Results

High HO-1 expression in PaCa cell lines was associated with increased chemoresistance in vitro. Chemoresistance to gemcitabine was increased during HO-1 induction in PaCa cells expressing low levels of HO-1. The inhibition of HO-1 activity in pancreatic tumors with high HO-1 boosted chemotherapeutic effects in vivo significantly. Furthermore, biliverdin and iron promoted PaCa resistance to chemotherapy. Consequently, specific iron chelation by desferrioxamine revealed profound anticancerous effects.

Conclusion

In summary, the inhibition of HO-1 and the chelation of iron in PaCa cells were associated with increased sensitivity and susceptibility of pancreatic tumors to chemotherapy in vivo. The metabolites biliverdin and iron seem to be involved in HO-1-mediated resistance to anticancer treatment. Therefore, HO-1 inhibition or direct interference with its metabolites may evolve new PaCa treatment strategies.

Cytoprotective function of heme oxygenase 1 induced by a nitrated cyclic nucleotide formed during murine salmonellosis

Signaling mechanisms of NO-mediated host defense are yet to be elucidated. In this study, we report a unique signal pathway for cytoprotection during Salmonella infection that involves heme oxygenase 1 (HO-1) induced by a nitrated cyclic nucleotide, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP). Wild-type C57BL/6 mice and C57BL/6 mice lacking inducible NO synthase (iNOS) were infected with Salmonella enterica serovar Typhimurium LT2. HO-1 was markedly up-regulated during the infection, the level being significantly higher in wild-type mice than in iNOS-deficient mice. HO-1 up-regulation was associated with 8-nitro-cGMP formation detected immunohistochemically in Salmonella-infected mouse liver and peritoneal macrophages. 8-Nitro-cGMP either exogenously added or formed endogenously induced HO-1 in cultured macrophages infected with Salmonella. HO-1 inhibition by polyethylene glycol-conjugated zinc-protoporphyrin IX impaired intracellular killing of bacteria in mouse liver and in both RAW 264 cells and peritoneal macrophages. Infection-associated apoptosis was also markedly increased in polyethylene glycol-conjugated zinc-protoporphyrin IX-treated mouse liver cells and cultured macrophages. This effect of HO-1 inhibition was further confirmed by using HO-1 short interfering RNA in peritoneal macrophages. Our results suggest that HO-1 induced by NO-mediated 8-nitro-cGMP formation contributes, via its potent cytoprotective function, to host defense during murine salmonellosis.

Therapeutic strategies by modulating oxygen stress in cancer and inflammation

Oxygen is the essential molecule for all aerobic organisms, and plays predominant role in ATP generation, namely, oxidative phosphorylation. During this process, reactive oxygen species (ROS) including superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) are produced as by-products, while it seems indispensable for signal transduction pathways that regulate cell growth and reduction-oxidation (redox) status. However, during times of environmental stress ROS levels may increase dramatically, resulting in significant damage to cell structure and functions. This cumulated situation of ROS is known as oxidative stress, which may, however, be utilized for eradicating cancer cells. It is well known that oxidative stress, namely over-production of ROS, involves in the initiation and progression of many diseases and disorders, including cardiovascular diseases, inflammation, ischemia-reperfusion (I/R) injury, viral pathogenesis, drug-induced tissue injury, hypertension, formation of drug resistant mutant, etc. Thus, it is reasonable to counter balance of ROS and to treat such ROS-related diseases by inhibiting ROS production. Such therapeutic strategies are described in this article, that includes polymeric superoxide dismutase (SOD) (e.g., pyran copolymer-SOD), xanthine oxidase (XO) inhibitor as we developed water soluble form of 4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine (AHPP), heme oxygenase-1 (HO-1) inducers (e.g., hemin and its polymeric form), and other antioxidants or radical scavengers (e.g., canolol). On the contrary, because of its highly cytotoxic nature, ROS can also be used to kill cancer cells if one can modulate its generation selectively in cancer. To achieve this goal, a unique therapeutic strategy was developed named as "oxidation therapy", by delivering cytotoxic ROS directly to the solid tumor, or alternatively inhibiting the antioxidative enzyme system, such as HO-1 in tumor. This anticancer strategy was examined by use of O(2)(-) or H(2)O(2)-generating enzymes (i.e., XO and d-amino acid oxidase [DAO] respectively), and by discovering the inhibitor of HO-1 (i.e., zinc protoporphyrin [ZnPP] and its polymeric derivatives). Further for the objective of tumor targeting and thus reducing side effects, polymer conjugates or micellar drugs were prepared by use of poly(ethylene glycol) (PEG) or styrene maleic acid copolymer (SMA), which utilize EPR (enhanced permeability and retention) effect for tumor-selective delivery. These macromolecular drugs further showed superior pharmacokinetics including much longer in vivo half-life, particularly tumor targeted accumulation, and thus remarkable antitumor effects. The present review concerns primarily our own works, in the direction of "Controlling oxidative stress: Therapeutic and delivery strategy" of this volume.

MTDH activation by 8q22 genomic gain promotes chemoresistance and metastasis of poor-prognosis breast cancer

Targeted therapy for metastatic diseases relies on the identification of functionally important metastasis genes from a large number of random genetic alterations. Here we use a computational algorithm to map minimal recurrent genomic alterations associated with poor-prognosis breast cancer. 8q22 genomic gain was identified by this approach and validated in an extensive collection of breast tumor samples. Regional gain of 8q22 elevates expression of the metastasis gene metadherin (MTDH), which is overexpressed in more than 40% of breast cancers and is associated with poor clinical outcomes. Functional characterization of MTDH revealed its dual role in promoting metastatic seeding and enhancing chemoresistance. These findings establish MTDH as an important therapeutic target for simultaneously enhancing chemotherapy efficacy and reducing metastasis risk.

Matrix-free high-resolution imaging mass spectrometry with high-energy ion projectiles

The importance of imaging mass spectrometry (MS) for visualizing the spatial distribution of molecular species in biological tissues and cells is growing. We have developed a new system for imaging MS using MeV ion beams, termed MeV-secondary ion mass spectrometry (MeV-SIMS) here, and demonstrated more than 1000-fold increase in molecular ion yield from a peptide sample (1154 Da), compared to keV ion irradiation. This significant enhancement of the molecular ion yield is attributed to electronic excitation induced in the near-surface region by the impact of high energy ions. In addition, the secondary ion efficiency for biologically important compounds (>1 kDa) increased to more than 10(10) cm(-2), demonstrating that the current technique could, in principle, achieve micrometer lateral resolution. In addition to MeV-SIMS, peptide compounds were also analyzed with cluster-SIMS and the results indicated that in the former method the molecular ion yields increased substantially compared to the latter. To assess the capability of MeV-SIMS to acquire heavy-ion images, we have prepared a micropatterned peptide surface and successfully obtained mass spectrometric imaging of the deprotonated peptides (m/z 1153) without any matrix enhancement. The results obtained in this study indicate that the MeV-SIMS technique can be a powerful tool for high-resolution imaging in the mass range from 100 to over 1000 Da.

Induction of tumor growth after preoperative portal vein embolization: is it a real problem?

Although preoperative portal vein embolization (PVE) is an effective means to increase future remnant liver (FRL) volume, little has been published on possible adverse effects. This review discusses the clinical and experimental evidence regarding the effect of PVE on tumor growth in both embolized and nonembolized liver lobes, as well as potential strategies to control tumor progression after PVE. A literature review was performed using MEDLINE with keywords related to experimental and clinical studies concerning PVE, portal vein ligation (PVL), and tumor growth. Cross-references and references from reviews were also checked. Clinical and experimental data suggest that tumor progression can occur after preoperative PVE in embolized and nonembolized liver segments. Clinical evidence indicating possible tumor progression in patients with colorectal metastases or with primary liver tumors is based on studies with small sample size. Although multiple studies demonstrated tumor progression, evidence concerning a direct increase in tumor growth rate as a result of PVE is circumstantial. Three possible mechanisms influencing tumor growth after PVE can be recognized, namely changes in cytokines or growth factors, alteration in hepatic blood supply and an enhanced cellular host response promoting local tumor growth after PVE. Post-PVE chemotherapy and sequential transcatheter arterial chemoembolization (TACE) before PVE have been proposed to reduce tumor mass after PVE. We conclude that tumor progression can occur after PVE in patients with colorectal metastases as well as in patients with primary liver tumors. However, further research is needed in order to rate this risk of tumor progression after PVE.

Progression of intracranial glioma disrupts thymic homeostasis and induces T-cell apoptosis in vivo

The thymus is the site where all T-cell precursors develop, mature, and subsequently leave as mature T-cells. Since the mechanisms that mediate and regulate thymic apoptosis are not fully understood, we utilized a syngenic GL261 murine glioma model to further elucidate the fate of T-cells in tumor bearing C57BL/6 mice. First, we found a dramatic reduction in the size of the thymus accompanied by a decrease in thymic cellularity in response to glioma growth in the brains of affected mice. There was a marked reduction of double positive subset and an increase in the frequency of CD4(+) and CD8(+) single positive T-cell subsets. Analysis of double negative thymocytes showed an increase in the accumulation of CD44(+) cells. In contrast, there was a marked loss of CD44 and CD122 expression in CD4(+) and CD8(+) subsets. The growth of intracranial tumors was also associated with decreased levels of HO-1, a mediator of anti-apoptotic function, and increased levels of Notch-1 and its ligand, Jagged-1. To determine whether thymic atrophy could be due to the effect of Notch and its ligand expression by glioma in vivo, we performed a bone marrow transplant experiment. Our results suggest that Notch-1 and its ligand Jagged-1 can induce apoptosis of thymocytes, thereby influencing thymic development, immune system homeostasis, and function of the immune cells in a model of experimental glioma.

Dual roles of Nrf2 in cancer

In response to oxidative stress, the transcription factor NF-E2-related factor 2 (Nrf2) controls the fate of cells through transcriptional upregulation of antioxidant response element (ARE)-bearing genes, including those encoding endogenous antioxidants, phase II detoxifying enzymes, and transporters. Expression of the Nrf2-dependent proteins is critical for ameliorating or eliminating toxicants/carcinogens to maintain cellular redox homeostasis. As a result, activation of the Nrf2 pathway, by naturally-occurring compounds or synthetic chemicals at sub-toxic doses, confers protection against subsequent toxic/carcinogenic exposure. Thus, the use of dietary compounds or synthetic chemicals to boost the Nrf2-dependent adaptive response to counteract environmental insults has emerged to be a promising strategy for cancer prevention. Interestingly, recent emerging data has revealed the "dark" side of Nrf2. Nrf2 and its downstream genes are overexpressed in many cancer cell lines and human cancer tissues, giving cancer cells an advantage for survival and growth. Furthermore, Nrf2 is upregulated in resistant cancer cells and is thought to be responsible for acquired chemoresistance. Therefore, it may be necessary to inhibit the Nrf2 pathway during chemotherapy. This review is primarily focused on the role of Nrf2 in cancer, with emphasis on the recent findings indicating the cancer promoting function of Nrf2 and its role in acquired chemoresistance.

Inhibition of heme oxygenase 1 expression by small interfering RNA decreases orthotopic tumor growth in livers of mice

Endogenous overexpression of the antiapoptotic protein heme oxygenase 1 (HO-1) has been shown to occur in various cancer diseases and might contribute to cancer progression. We compared the expression levels of HO-1 in human liver to expression levels in hepatocellular carcinoma (HCC), as well as the effect of HO-1 inhibition by small interfering RNA (siRNA) on cellular survival and apoptosis in the mouse hepatoma cell lines Hepa129 and Hepa1-6 and on orthotopic tumor growth in immune-competent C3H/HeN mice. Our results show that HO-1 is frequently overexpressed in human HCC. Downmodulation of HO-1 by siRNA resulted in increased cellular damage and apoptosis, reduced proliferation, reduced growth of orthotopic HCC and reduced angiogenesis. Livers and kidneys of treated animals did not reveal signs of damage by this treatment. In conclusion, a specific knockdown of HO-1 might represent a novel therapeutic approach in HCC therapy.

Implication of heme oxygenase-1 in the sensitivity of nasopharyngeal carcinomas to radiotherapy

High expression of the inducible isoform of heme oxygenase (HO-1) is well known in various solid tumors in human and experimental animal models. To investigate the relationship between HO-1 and nasopharyngeal carcinomas, especially its involvement in the response of nasopharyngeal carcinomas to radiotherapy, thirty-two nasopharyngeal carcinomas were semi-quantitatively analyzed by RT-PCR, and the expression of HO-1 was correlated with the consequence after novel radiotherapy, which was evaluated by the reduction of tumor size. Among 32 nasopharyngeal carcinomas, HO-1 expression was found in19 samples (59.4%), in which 9 patients (47.4%) showed no response to radiotherapy. Interestingly, in 13 nasopharyngeal carcinoma patients with negative expression of HO-1, radiotherapy exhibited to be effective (9 patients, 69.2%) or responsive (3 patients, 23.1%). In this study, we first demonstrated the expression of HO-1 in nasopharyngeal carcinomas, and more important, these findings strongly suggest the potential of HO-1as a useful index in identifying patients with well response to radiotherapy, further these data indicate a new therapeutic for nasopharyngeal carcinoma by inhibiting HO-1 activity, which warrants further investigation.

Increased risk of gastric cancer in Japanese subjects is associated with microsatellite polymorphisms in the heme oxygenase-1 and the inducible nitric oxide synthase gene promoters

Microsatellite polymorphism in the promoter region of the heme oxygenase-1 (HO-1) gene was analyzed jointly with that of the inducible nitric oxide synthase (iNOS) gene among Japanese subjects (control and gastric cancer patients). A higher promoter activity genotype of the HO-1 gene was associated with increased risk for gastric cancer in women. Gastric cancer risk was notably increased in subjects carrying a higher promoter activity genotype for both HO-1 and iNOS compared to those with a lower promoter activity genotype for both genes. Our data suggest that genetic polymorphisms of HO-1 and iNOS modulate individual susceptibility to gastric cancer risk.

Age-related effects of cocultured rat nucleus pulposus cells and macrophages on nitric oxide production and cytokine imbalance

STUDY DESIGN

A study of age-related effects on nitric oxide (NO) and cytokine production in cocultured rat nucleus pulposus (NP) cells and macrophages.

OBJECTIVE

To evaluate the effects of age on NO and cytokine production in an in vitro model of cocultured NP cells and macrophages.

SUMMARY OF BACKGROUND DATA

It is well known that the clinical characteristics of lumbar disc herniation differ with age. The relationship between age-related differences in clinical features and immuno-chemical factors, such as NO and inflammatory cytokines, has not been established.

METHODS

Male Sprague Dawley rats (n = 45), including 15 animals from 3 groups (3-, 12-, and 32-weeks old), were used. NP cells and exudated peritoneal macrophages were cocultured in serum-free media. NO levels were measured at 2-, 24-, 48-, and 72 hours using the Griess method. After 7 days of culture, the production of cytokines, including tissue inhibitor metalloproteinase-1, interferon-gamma (IFN-gamma), and interleukin-10 (IL-10) were evaluated.

RESULTS

NO levels of coculture increased with age. In the coculture groups, tissue inhibitor metalloproteinase-1 and IFN-gamma level of 3 weeks old were statistically higher than 12 and 32 weeks old. IL-10 level of 3 weeks old was statistically lower than 12 and 32 weeks old.

CONCLUSION

NO levels of cocultures increased with age that suggests inflammatory reactions increase with age. This study showed an age-related cytokine imbalance, as represented by levels of IFN-gamma and IL-10. Stress and aging are thought to affect the extracellular matrix and change the immunologic response. Younger rat NP cells had higher cell-mediated immunity activity, while the older rat had higher humoral immunity activity. These results demonstrate that age affects the immunologic response attributable to NP cells. Further studies are needed to elucidate the mechanism of this newly observed occurrence and to apply these findings clinically.

HO-1 underlies resistance of AML cells to TNF-induced apoptosis

In human monocytes, tumor necrosis factor (TNF) induces a proinflammatory response. In NF-κB–inhibited monocytes, TNF stimulates cell death/apoptosis. In the present study, we analyzed the response of acute myeloid leukemia (AML) cells to TNF stimulation in conjunction with NF-κB inhibition. In all AML-derived cells tested, NF-κB–inhibited cells were resistant to TNF-induced apoptosis. Further investigation revealed that the cytoprotective gene heme oxygenase-1 (HO-1) was induced in NF-κB–inhibited AML cells in response to TNF stimulation, and HO-1 was responsible for the resistance of AML cells to the cytotoxic actions of TNF. Moreover, after transfection with HO-1 siRNA, the resistance to TNF-induced cell death signals of AML cells was removed. The HO-1 promoter region contains antioxidant-response elements that can bind the transcription factor NF-E2–related factor 2 (Nrf2). We further demonstrated that Nrf2 was activated by TNF under NF-κB–inhibited conditions, to play the major role in up-regulating HO-1 expression and ultimately the fate of AML cells. These results demonstrate a novel mechanism by which TNF-induced cell death is inhibited in AML cells through the induction of HO-1, via Nrf2 activation.

Pharmacological and clinical aspects of heme oxygenase

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

Upregulation of heme oxygenase-1 in oral epithelial dysplasias

The expression of heme oxygenase-1 (HO-1), stress-related enzyme, is induced in leukaemia and some cancer tissues, but relatively little is known about the differential pattern of HO-1 expression and proliferation in premalignant lesions of the epithelial oral mucosa. The purpose of this study was to evaluate whether HO-1 expression and proliferation were increased in preneoplastic lesions compared to normal and oral cancer tissues. Immunohistochemical staining was used to examine the expression patterns of HO-1 and proliferating cell nuclear antigen (PCNA) in a series of normal mucosa and mild-to-severe cases of oral epithelial dysplasia (OED) and oral squamous cell carcinoma. Both HO-1 and PCNA are expressed in the basal cells of normal oral mucosa. In patients with OED and carcinoma in situ, immunostaining for PCNA and HO-1 was more intense, and gradually extended into the superficial layers of the mucosa. HO-1 and PCNA expression was correlated with the degree of epithelial dysplasia. Oral squamous cell carcinoma also showed elevated expression of HO-1, but this level was not higher than in severe OED or carcinoma in situ. These results suggest that the up-regulation of HO-1 in premalignant oral lesions is part of an early cytoprotection mechanism against carcinogenesis in the oral mucosa.

Heme oxygenase-1 in tumors: is it a false friend?

Heme oxygenase-1 (HO-1) catalyzes the oxidation of heme to biologically active products: carbon monoxide (CO), biliverdin, and ferrous iron. It participates in maintaining cellular homeostasis and plays an important protective role in the tissues by reducing oxidative injury, attenuating the inflammatory response, inhibiting cell apoptosis, and regulating cell proliferation. HO-1 is also an important proangiogenic mediator. Most studies have focused on the role of HO-1 in cardiovascular diseases, in which its significant, beneficial activity is well recognized. A growing body of evidence indicates, however, that HO-1 activation may play a role in carcinogenesis and can potently influence the growth and metastasis of tumors. HO-1 is very often upregulated in tumor tissues, and its expression is further increased in response to therapies. Although the exact effect can be tissue specific, HO-1 can be regarded as an enzyme facilitating tumor progression. Accordingly, inhibition of HO-1 can be suggested as a potential therapeutic approach sensitizing tumors to radiation, chemotherapy, or photodynamic therapy.

Nuclear translocation of haeme oxygenase-1 is associated to prostate cancer

The role of oxidative stress in prostate cancer has been increasingly recognised. Acute and chronic inflammations generate reactive oxygen species that result in damage to cellular structures. Haeme oxygenase-1 (HO-1) has cytoprotective effects against oxidative damage. We hypothesise that modulation of HO-1 expression may be involved in the process of prostate carcinogenesis and prostate cancer progression. We thus studied HO-1 expression and localisation in 85 samples of organ-confined primary prostate cancer obtained via radical prostatectomy (Gleason grades 4–9) and in 39 specimens of benign prostatic hyperplasia (BPH). We assessed HO-1 expression by immunohistochemical staining. No significant difference was observed in the cytoplasmic positive reactivity among tumours (84%), non-neoplastic surrounding parenchyma (89%), or BPH samples (87%) (P=0.53). Haeme oxygenase-1 immunostaining was detected in the nuclei of prostate cancer cells in 55 of 85 (65%) patients but less often in non-neoplastic surrounding parenchyma (30 of 85, 35%) or in BPH (9 of 39, 23%) (P<0.0001). Immunocytochemical and western blot analysis showed HO-1 only in the cytoplasmic compartment of PC3 and LNCaP prostate cancer cell lines. Treatment with hemin, a well-known specific inducer of HO-1, led to clear nuclear localisation of HO-1 in both cell lines and highly induced HO-1 expression in both cellular compartments. These findings have demonstrated, for the first time, that HO-1 expression and nuclear localisation can define a new subgroup of prostate cancer primary tumours and that the modulation of HO-1 expression and its nuclear translocation could represent new avenues for therapy.

Suppression of Nrf2-driven heme oxygenase-1 enhances the chemosensitivity of lung cancer A549 cells toward cisplatin

Heme oxygenase-1 (HO-1) is highly expressed in various tumor tissues and plays an important role in tumor cell growth through anti-oxidative and anti-apoptotic effects. Herein, we demonstrate that A549 cells express high levels of HO-1, Nrf2, and NF-kappaB compared to other lung cancer cell lines, including H23, H157, and H460. Ectopic expression of HO-1 small interfering RNA (siRNA) increased both apoptosis and degradation of procaspase-3. Transfection studies with siRNA specific for Nrf2 and NF-kappaB revealed that HO-1 expression in A549 cells is mediated by transcriptional activation of Nrf2, but not NF-kappaB. A549 cells are less susceptible to cisplatin cytotoxicity than other lung cancer cell lines, concomitant with increases in HO-1 expression and MAPK phosphorylation in a time-dependent fashion. Furthermore, inhibition of HO-1 by siRNA and a specific HO-1 inhibitor ZnPP augments cisplatin cytotoxicity toward A549 cells. Pharmacologic suppression of HO-1 activity resulted in a marked increase in the ROS generation in cisplatin-treated cells. In addition, pharmacologic inhibitors of MAPK suppressed the induction of HO-1 and Nrf2 expression by cisplatin. These findings suggest that HO-1 may modulate the chemosensitivity of lung cancer A549 cells to cisplatin through the MAPK-Nrf2 pathway.

Targeting of heat shock protein 32 (Hsp32)/heme oxygenase-1 (HO-1) in leukemic cells in chronic myeloid leukemia: a novel approach to overcome resistance against imatinib

Resistance toward imatinib and other BCR/ABL tyrosine kinase inhibitors remains an increasing clinical problem in the treatment of advanced stages of chronic myeloid leukemia (CML). We recently have identified the heat shock protein 32 (Hsp32)/heme oxygenase-1 (HO-1) as a BCR/ABL-dependent survival molecule in CML cells. We here show that silencing Hsp32/HO-1 in CML cells by an siRNA approach results in induction of apoptosis. Moreover, targeting Hsp32/HO-1 by either pegylated zinc protoporphyrine (PEG-ZnPP) or styrene maleic acid-micelle-encapsulated ZnPP (SMA-ZnPP) resulted in growth inhibition of BCR/ABL-transformed cells. The effects of PEG-ZnPP and SMA-ZnPP were demonstrable in Ba/F3 cells carrying various imatinib-resistant mutants of BCR/ABL, including the T315I mutant, which exhibits resistance against all clinically available BCR/ABL tyrosine kinase inhibitors. Growth-inhibitory effects of PEG-ZnPP and SMA-ZnPP also were observed in the CML-derived human cell lines K562 and KU812 as well as in primary leukemic cells obtained from patients with freshly diagnosed CML or imatinib-resistant CML. Finally, Hsp32/HO-1-targeting compounds were found to synergize with either imatinib or nilotinib in producing growth inhibition in imatinib-resistant K562 cells and in Ba/F3 cells harboring the T315I mutant of BCR/ABL. In summary, these data show that HO-1 is a promising novel target in imatinib-resistant CML.

Tumor-targeted induction of oxystress for cancer therapy

Reactive oxygen species (ROS), such as superoxide anion radicals (O.-2) and hydrogen peroxide (H2O2) are potentially harmful by-products of normal cellular metabolism that directly affect cellular functions. ROS is generated by all aerobic organisms and it seems to be indispensable for signal transduction pathways that regulate cell growth and reduction-oxidation (redox) status. However, overproduction of these highly reactive oxygen metabolites can initiate lethal chain reactions, which involve oxidation and damage to structures that are crucial for cellular integrity and survival. In fact, many antitumor agents, such as vinblastine, cisplatin, mitomycin C, doxorubicin, camptothecin, inostamycin, neocarzinostatin and many others exhibit antitumor activity via ROS-dependent activation of apoptotic cell death, suggesting potential use of ROS as an antitumor principle. Thus, a unique anticancer strategy named "oxidation therapy" has been developed by inducing cytotoxic oxystress for cancer treatment. This goal could be achieved mainly by two methods, namely, (i) inducing the generation of ROS directly to solid tumors and (ii) inhibiting the antioxidative enzyme (defense) system of tumor cells. Since 1950s, many strategies have been employed based on the first method, namely, administration of ROS per se (e.g. H2O2) or ROS generating enzyme to tumor bearing animals. However no successful and practical results were obtained probably because of the lack of tumor selective ROS delivery and hence resulting in subsequent induction of severe side effects. To overcome these obstacles, we developed polyethylene glycol (PEG) conjugated O.-2 or H2O2-generating enzymes, xanthine oxidase (XO) and D-amino acid oxidase (DAO) (PEG-DAO) respectively. More recently, a pegylated (PEG) zinc protoporphyrin (PEG-ZnPP) and a highly water soluble micellar formulation of ZnPP based on amphiphilic styrene maleic acid (SMA) copolymer, SMA-ZnPP, are prepared, which are potent inhibitors of heme oxygenase-1 (HO-1). HO-1 is a major antioxidative enzyme of tumors, that is different in mechanism of catalase or superoxide dismutase (SOD). Consequently, both PEG-enzymes and PEG-ZnPP exhibited superior in vivo pharmacokinetics than their parental molecules, particularly in tumor delivery by taking advantage of the EPR effect of macromolecular nature, and thus showed remarkable antitumor effects suggesting the potentials of this anticancer therapeutic for clinical application. Furthermore, it has been well known that many antioxidative enzymes such as catalase, SOD are down-regulated in most solid tumors in vivo. On the contrary, HO-1 is highly upregulated and it plays a very important role of antioxidation, because HO-1 generates biliverdin, which being converted to bilirubin exhibits a very potent antioxidative effect, and hence antiapoptosis in tumors. Thus this oxidation therapy, by inhibiting this HO-1 dependent antioxidant (bilirubin) formation by ZnPP, and by enhancing ROS generation, is expected to offer a powerful therapeutic modality for future anticancer therapy.

Decreased heme-oxygenase (HO)-1 in the macrophages of non-small cell lung cancer

Reactive oxygen species (ROS) are important in the initiation and promotion of cells to neoplastic growth. Heme-oxygenase (HO)-1, the inducible form of heme-oxygenase, is a cytoprotective enzyme that plays a central role in the defence against oxidative stress and is implicated in the protection of lung tissue against exogenous oxidant exposure. We investigated whether the expression of HO-1 would be decreased in lung tumour as compared with tumour-free adjacent lung tissues. HO-1 expression was quantified by immunohistochemistry in tumour macrophages, in macrophages of tumour-free lung and in tumour cells of surgical specimens collected from 53 individuals with surgically resectable non-small cell lung cancer (NSCLC). The expression of HO-1 was decreased in tumour as compared with tumour-free lung macrophages. No correlations were observed between the expression of HO-1 and both the clinicopathological characteristics and the overall survival of the examined subjects. In conclusion, our data show that macrophages of non-small cell lung cancer exhibit impaired anti-oxidant defence mechanisms, likely mediated by HO-1. Conversely, HO-1 expression does not seem to be associated with lung tumour progression and prognosis.

Hepatitis C core protein inhibits induction of heme oxygenase-1 and sensitizes hepatocytes to cytotoxicity

Hepatitis C virus (HCV) core protein is a transcriptional modifier whose expression is associated with increased levels of prooxidants in hepatocytes in vivo and in vitro. We previously reported that HCV-infected liver biopsies and core protein-expressing hepatocytes show diminished levels of heme oxygenase-1 (HO-1), which is an important oxidative defense enzyme. The objective of these studies was to test the hypothesis that the expression of core protein sensitizes hepatocytes to toxic injury and inhibits the induction of HO-1 in response to stress. The effects of core protein were tested in two different human hepatocyte cell lines, HepG2 and Huh7, which show increased prooxidative activity and cytotoxicity after treatment with heme, heavy metals, and peroxides compared to control cells. HO-1 is upregulated in response to these treatments in control cells, while the induction is attenuated in core protein-expressing cells. The effects of core protein on HO-1 expression are not accounted for by differences in HO-1 mRNA turnover or by the known effects of core protein on cellular proliferation. Collectively, these data suggest that HCV core protein may contribute to hepatocellular injury by increasing both steady-state levels of prooxidants and the susceptibility of hepatocytes to damage by impairing their response to other sources of oxidative stress.

Portal branch ligation induces a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and cell proliferation in portal blood-deprived liver tissue

Portal branch ligation (PBL) may prevent liver failure after extended hepatic resection. However, clinical studies indicate that tumors within the ligated lobe develop accelerated growth. Although it is well known that tumor growth depends on the host's microvascularization, there is no information about how PBL affects the hepatic microcirculation. Our aims were to determine hepatic artery response, liver microcirculation, tissue oxygenation, and cell proliferation after PBL. Therefore, we used intravital multifluorescence microscopy, laser-Doppler flowmetry, immunohistochemistry, and biochemical techniques to examine microcirculatory responses, microvascular remodeling, and cellular consequences after left lateral PBL in BALB/c mice. During the first 7 days, PBL induced a reduction of left hilar blood flow by approximately 50%. This resulted in 80% sinusoidal perfusion failure, significant parenchymal hypoxia, and liver atrophy. After 14 days, however, left hilar blood flow was found to be restored. However, remodeling of the microvasculature included a rarefaction of the sinusoidal network, however, without substantial perfusion failure, compensated by a hepatic arterial buffer response and significant sinusoidal dilatation. This resulted in normalization of tissue oxygenation, indicating arterialization of the ligated lobe. Interestingly, late microvascular remodeling was associated with increased endothelial nitric oxide synthase expression, significant hepatocellular proliferation, and weight gain of the ligated lobe. Thus PBL induces only an initial microcirculatory failure with liver atrophy, followed by a hepatic arterial buffer response, microvascular remodeling, normoxygenation, and hepatocellular proliferation. This may explain the accelerated tumor progression occasionally observed in patients after PBL.

High-loading nanosized micelles of copoly(styrene–maleic acid)–zinc protoporphyrin for targeted delivery of a potent heme oxygenase inhibitor

Amphiphilic styrene-maleic acid (SMA) copolymer efficiently formed micelles with a potent heme oxygenase inhibitor-zinc protoporphyrin (ZnPP). The micelles were constructed by subtle pH adjustments to form non-covalent interaction between the hydrophobic ZnPP and amphiphilic SMA. The micelles (SMA-ZnPP) thus formed were nanoparticles with narrow size distribution in water (mean diameter 176.5nm), having tunable loading (from 15% to 60% w/w of ZnPP) with remarkable aqueous solubility. SMA-ZnPP had an average molecular size of 144kDa as determined by size-exclusion chromatography (SEC), this size is a marked increase from the molecular weight of free ZnPP (626.03Da), suggesting the formation of micellar structure. The micelles showed a constant ZnPP release rate of about 0.5%/day in vitro at neutral pH. SMA-ZnPP micelles inhibited splenic microsomal HO-1 activity, in a competitive and dose-dependent manner, with an apparent inhibitory constant (K(i)) of 0.12mum, comparable to free ZnPP and also exhibited marked cytotoxic effect on KYSE-510 human esophageal cancer cells. The unique features of SMA-ZnPP micelles are that they are nanoparticles in aqueous solution having high water solubility and loading, yet macromolecular in nature, which can be beneficial in targeted release of a potent HO-1 inhibitor.