Upregulation of heme oxygenase-1 and p21 confers resistance to apoptosis in human gastric cancer cells

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.

The Galpha12/13 family of heterotrimeric G proteins and the small GTPase RhoA link the Kaposi sarcoma-associated herpes virus G protein-coupled receptor to heme oxygenase-1 expression and tumorigenesis

Heme oxygenase-1 (HO-1), an inducible enzyme that metabolizes the heme group, is highly expressed in human Kaposi sarcoma lesions. Its expression is up-regulated by the G protein-coupled receptor from the Kaposi sarcoma-associated herpes virus (vGPCR). Although recent evidence shows that HO-1 contributes to vGPCR-induced tumorigenesis and vascular endothelial growth factor (VEGF) expression, the molecular steps that link vGPCR to HO-1 remain unknown. Here we show that vGPCR induces HO-1 expression and transformation through the Galpha(12/13) family of heterotrimeric G proteins and the small GTPase RhoA. Targeted small hairpin RNA knockdown expression of Galpha(12), Galpha(13), or RhoA and inhibition of RhoA activity impair vGPCR-induced transformation and ho-1 promoter activity. Knockdown expression of RhoA also reduces vGPCR-induced VEFG-A secretion and blocks tumor growth in a murine allograft tumor model. NIH-3T3 cells expressing constitutively activated Galpha(13) or RhoA implanted in nude mice develop tumors displaying spindle-shaped cells that express HO-1 and VEGF-A, similarly to vGPCR-derived tumors. RhoAQL-induced tumor growth is reduced 80% by small hairpin RNA-mediated knockdown expression of HO-1 in the implanted cells. Likewise, inhibition of HO-1 activity by chronic administration of the HO-1 inhibitor tin protoporphyrin IX to mice reduces RhoAQL-induced tumor growth by 70%. Our study shows that vGPCR induces HO-1 expression through the Galpha(12/13)/RhoA axes and shows for the first time a potential role for HO-1 as a therapeutic target in tumors where RhoA has oncogenic activity.

Colonic expression of heme oxygenase-1 is associated with a better long-term survival in patients with colorectal cancer

OBJECTIVE

Heme oxygenase-1 (HO-1) has emerged as a crucial mediator of mucosal defense in the gastrointestinal tract. Its metabolic pathway products, biliverdin/bilirubin and carbon monoxide, can reduce oxidative stress and inflammation, and promote resistance to apoptosis. The role of HO-1 in gastrointestinal malignancies, however, remains to be elucidated. The purpose of this study was to analyze HO-1 expression in human colon adenoma and cancer samples.

MATERIAL AND METHODS

Fifty-five paraffin-embedded surgical specimens of colorectal cancer and 19 colonic adenoma samples were stained immunhistochemically for HO-1 expression using an anti-HO-1 monoclonal antibody. HO-1 expression was evaluated independently by two different investigators and subsequently correlated to clinical data and patients' life expectancy.

RESULTS

Focal HO-1 expression could be documented in 41.8% (23/55) of patients with colorectal cancer. HO-1 expression in colonic adenoma was detectable in 36.8% (7/19) of cases. The rate of lymphatic tumor invasion was significantly lower in colorectal cancer samples expressing HO-1 (p=0.048). Additionally, fewer lymph node metastases were found in colorectal cancer samples with HO-1 expression, but these differences did not reach statistical significance. Mean observation period was 65.87+/-3.96 months. Kaplan-Meier analysis showed a significantly better survival for colorectal cancer patients with colonic HO-1 expression (p=0.018).

CONCLUSIONS

This study demonstrates that colonic HO-1 may be a prognostic marker of colorectal-cancer outcome.

Heme oxygenase-1 gene promoter polymorphism is associated with risk of gastric adenocarcinoma and lymphovascular tumor invasion

PURPOSE

Heme oxygenase-1 (HO-1) gene, which encodes an oxidative response protein, plays a role in cytoprotection. A (GT)n dinucleotide repeat in HO-1 promoter is polymorphic and modulates the transcriptional activity of the gene. A HO-1 gene promoter polymorphism was reported to be associated with the risks of lung adenocarcinoma and oral squamous cancer. In this study, the correlation between the HO-1 gene promoter polymorphism and the clinicopathological characteristics, along with the risk of gastric cancer, was analyzed.

EXPERIMENTAL DESIGN

We examined the genotypic frequencies of (GT)n repeats in 183 gastric cancer patients and 250 control subjects by PCR-based genotyping and DNA sequencing. The length polymorphisms of (GT)n repeats were classified into short (S) component (n <or= 25), medium (M) component (26 <or= n <or= 30) and long (L) component (n >or= 31). The distribution of S, M and L components in patient and control groups were evaluated to determine the correlation with susceptibility and clinicopathological characteristics of gastric adenocarcinoma.

RESULTS

Higher frequencies of L-allele, L-allele carrier (S/L, M/L, L/L) and S/L genotype were found in gastric cancer patients. The frequencies of M-allele, M-allele carrier (M/M, M/L, M/S) and M/M genotype were significantly lower in patients with gastric cancer than controls. Furthermore, the frequency of lymphovascular tumor invasion was significantly lower in M-allele carriers compared to non-M-allele carriers (S/S, S/L, L/L) (p = 0.009).

CONCLUSIONS

These findings suggest that the long (GT)n repeat of HO-1 gene promoter was associated with a higher frequency of gastric adenocarcinoma, and the medium (GT)n repeat might possess protective effect against gastric adenocarcinoma with a lower frequency of lymphovascular invasion in tumors.

Identification of heat shock protein 32 (Hsp32) as a novel survival factor and therapeutic target in neoplastic mast cells

Systemic mastocytosis (SM) is a myeloid neoplasm characterized by increased survival and accumulation of neoplastic mast cells (MCs). In most patients, the D816V-mutated variant of KIT is detectable. We report here that heat shock protein 32 (Hsp32), also known as heme oxygenase-1 (HO-1), is a novel KIT-inducible survival factor in neoplastic MCs. As assessed by reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry, and Western blotting, the KIT D816V(+) MC line HMC-1.2 as well as highly enriched primary neoplastic MCs were found to express Hsp32 mRNA and the Hsp32 protein. Moreover, KIT D816V and stem cell factor (SCF)-activated wild-type KIT were found to induce Hsp32 promoter activity, expression of Hsp32 mRNA, and expression of the Hsp32 protein in Ba/F3 cells. Correspondingly, the KIT D816V-targeting drug PKC412 decreased the expression of Hsp32 as well as proliferation/survival in neoplastic MCs. The inhibitory effects of PKC412 on the survival of HMC-1.2 cells were counteracted by the HO-1 inductor hemin or lentiviral-transduced HO-1. Moreover, 2 Hsp32-targeting drugs, pegylated zinc protoporphyrin (PEG-ZnPP) and styrene maleic acid copolymer micelle-encapsulated ZnPP (SMA-ZnPP), were found to inhibit proliferation and to induce apoptosis in neoplastic MCs. Furthermore, both drugs were found to cooperate with PKC412 in producing growth inhibition. Together, these data show that Hsp32 is an important survival factor and interesting new therapeutic target in neoplastic MCs.

Association of cooking oil fumes exposure with lung cancer: Involvement of inhibitor of apoptosis proteins in cell survival and proliferation in vitro

Cooking oil fumes (COF) have been shown to be associated with lung cancer incidence in Chinese women. Our recent report indicates that inhibitor of apoptosis protein 2 (IAP2) induced by COF may contribute to the survival and proliferation of A549 lung cancer cells. In this study, to further verify whether other antiapoptosis proteins including IAP1, X-linked IAP (XIAP), and survivin, were linked with lung cancer cell survival and proliferation, these IAPs expressions in A549 cells after treatment with COF and its two major components, benzo[a]pyrene (BaP) and 2,4-decadienal (2,4-DDE) were evaluated by Western blotting. Our data showed that IAP2 was significantly induced by COF, BaP, and 2,4-DDE, but XIAP was decreased by COF and 2,4-DDE, but not by BaP. Even though different effects of COF and 2,4-DDE on IAP2 and XIAP protein expressions were observed, the caspase-3 expression was diminished by COF and 2,4-DDE. In addition, induction of IAP2 and phosphorylated Akt proteins by COF and 2,4-DDE were simultaneously abolished by LY294002. Flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis showed that the proportion of A549 cells at the S-phase was increased significantly after treatment with COF or 2,4-DDE. The cell proliferation induced by COF is associated with the attenuation of p21(Cip/Waf1) expression. Therefore, increases of IAP1, IAP2, survivin, and cyclin D1 expressions and decreases of XIAP, caspase-3, and p21 expressions might partly contribute to the survival and proliferation of lung cancer cells after exposure to 2,4-DDE and COF. In conclusion, the lung cancer cell growth promoted by COF might support previous epidemiological reports indicating that exposure of COF was associated with lung cancer development among Chinese women.

Specific mTOR inhibitor rapamycin enhances cytotoxicity induced by alkylating agent 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU) in human U251 malignant glioma cells

Loss of the PTEN tumor suppressor gene and amplification of the epidermal growth factor receptor (EGFR), which is common in malignant gliomas, result in activation of the mammalian target of rapamycin (mTOR). Rapamycin is a highly specific inhibitor of mTOR and induces a cytostatic effect in various glioma cell lines. DNA-damaging agents such as nitrosourea are widely used in malignant glioma treatment; therefore, we investigated the effect of rapamycin on cell growth and death in combination with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU, nimustine hydrochloride) in human glioma cells. In U251 malignant glioma (U251MG) cells, we confirmed that rapamycin enhanced ACNU-induced apoptosis. We found that rapamysin inhibited ACNU-induced p21 induction, and knocking down of p21 protein by siRNA enhanced ACNU-induced apoptosis in U251MG cells. Furthermore, adenovirus-mediated over-expression of p21 protein rescued U251MG cells from apoptosis induced by ACNU and rapamycin. Finally, treatment of intracerebral U251MG xenografts with a combination of rapamycin and ACNU in vivo resulted in statistically prolonged median survival (P<0.05). These results suggest that rapamycin in combination with DNA-damaging agents may be efficacious in the treatment of malignant gliomas.

Molecular imaging using visible light to reveal biological changes in the brain

Advances in imaging have enabled the study of cellular and molecular processes in the context of the living body that include cell migration patterns, location and extent of gene expression, degree of protein-protein interaction, and levels of enzyme activity. These tools, which operate over a range of scales, resolutions, and sensitivities, have opened up broad new areas of investigation where the influence of organ systems and functional circulation is intact. There are a myriad of imaging modalities available, each with its own advantages and disadvantages, depending on the specific application. Among these modalities, optical imaging techniques, including in vivo bioluminescence imaging and fluorescence imaging, use visible light to interrogate biology in the living body. Optimal imaging with these modalities require that the appropriate marker be used to tag the process of interest to make it uniquely visible using a particular imaging technology. For each optical modality, there are various labels to choose from that range from dyes that permit tissue contrast and dyes that can be activated by enzymatic activity, to gene-encoding proteins with optical signatures that can be engineered into specific biological processes. This article provides and overview of optical imaging technologies and commonly used labels, focusing on bioluminescence and fluorescence, and describes several examples of how these tools are applied to biological questions relating to the central nervous system.

Overexpression of heme oxygenase-1 in murine melanoma: increased proliferation and viability of tumor cells, decreased survival of mice

Heme oxygenase-1 (HO-1), a cytoprotective enzyme, can be induced in tumors in response to anti-cancer therapies. We investigated the role of HO-1 in B16(F10), S91, and Sk-mel188 melanoma cells. Overexpression of HO-1 after transduction with adenoviral vectors increased cell proliferation, resistance to oxidative stress generated by H2O2, and angiogenic potential as determined by induction of endothelial cell divisions. Likewise, cells stably transfected with HO-1 cDNA (B16-HO-1) showed higher proliferation, stress resistance, and angiogenic activity than the wild-type line (B16-WT). HO-1 overexpression in tumors significantly shortened survival of mice after subcutaneous injection of cancer cells (38 and 22 days for B16-WT and B16-HO-1, respectively; P=0.017). This also resulted in development of more packed tumors, with more melanoma cells, and reduced inflammatory edemas. Mice injected with B16-HO-1 had lower levels of tumor necrosis factor and higher serum concentrations of its soluble receptor tumor necrosis factor-RI, whereas tumors overexpressing HO-1 displayed augmented vascularization and stronger production of vascular endothelial growth factor. Finally, B16-HO-1 cells injected intravenously formed more metastases in lungs. Thus, HO-1 overexpression increased viability, proliferation, and angiogenic potential of melanoma cells, augmented metastasis, and decreased survival of tumor-bearing mice, suggesting that induction of HO-1 may be detrimental in anti-cancer therapy of melanoma.

Heme oxygenase-1 as a potential therapeutic target for hepatoprotection

Heme oxygenase (HO), the rate limiting enzyme in the breakdown of heme into carbon monoxide (CO), iron and bilirubin, has recently received overwhelming research attention. To date three mammalian HO isozymes have been identified, and the only inducible form is HO-1 while HO-2 and HO-3 are constitutively expressed. Advances in unveiling signal transduction network indicate that a battery of redox-sensitive transcription factors, such as activator protein-1 (AP-1), nuclear factor-kappa B (NF-kappaB) and nuclear factor E2-related factor-2 (Nrf2), and their upstream kinases including mitogen-activated protein kinases play an important regulatory role in HO-1 gene induction. The products of the HO-catalyzed reaction, particularly CO and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression contributes to protection against liver damage induced by several chemical compounds such as acetaminophen, carbon tetrachloride and heavy metals, suggesting HO-1 induction as an important cellular endeavor for hepatoprotection. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect against chemically-induced liver injury as well as hepatocarcinogenesis.

Localization of a Prostate Cancer Predisposition Gene to an 880-kb Region on Chromosome 22q12.3 in Utah High-Risk Pedigrees

Chromosome 22q has become recently a region of interest for prostate cancer. We identified previously a logarithm of odds (LOD) of 2.42 at chromosome 22q12.3. Additionally, this region has been noted by eight other studies, with linkage evidence ranging from LOD of 1.50 to 3.57. Here, we do fine mapping and localization of the region using a pedigree-specific recombinant mapping approach in 14 informative, high-risk Utah pedigrees. These 14 pedigrees were chosen because they were either "linked" or "haplotype-sharing" pedigrees or both. "Linked" pedigrees were those with significant pedigree-specific linkage evidence (LOD, >0.588; P < 0.05) to the 22q12.3 region, regardless of the number of prostate cancer cases sharing the segregating haplotype. "Haplotype-sharing" pedigrees were those with at least five prostate cancer cases sharing a segregating haplotype in the 22q12.3 region, regardless of the linkage evidence. In each pedigree, the most likely haplotype configuration (in addition to the multipoint LOD graph for linked pedigrees) was used to infer the position of recombinant events and delimit the segregating chromosomal segment in each pedigree. These pedigree-specific chromosomal segments were then overlaid to form a consensus recombinant map across all 14 pedigrees. Using this method, we identified a 881,538-bp interval at 22q12.3, between D22S1265 and D22S277, which is the most likely region that contains the 22q prostate cancer predisposition gene. The unique Utah extended high-risk pedigree resource allows this powerful localization approach in pedigrees with evidence for segregating predisposition to prostate cancer. We are mutation screening candidate genes in this region to identify specific genetic variants segregating in these pedigrees.

How many transcription factors does it take to turn on the heme oxygenase-1 gene?

The ability to communicate with the environment and respond to changes--particularly those of an adverse nature--within that environment is critical for cell function and survival. A key component of the overall cellular stress response includes adjustments in the gene expression program in favor of proteins that manifest activities capable of frustrating and eventually eliminating the molecular constituents of the stress condition. One protein providing such cytoprotective activity is heme oxygenase-1 (HO-1), an enzyme that catalyzes the rate-limiting reaction in heme catabolism (i.e., the oxidative cleavage of b-type heme molecules to yield equimolar quantities of biliverdin IXalpha, carbon monoxide, and iron). Because of the potent antioxidant, anti-inflammatory, and signaling properties of the reaction products, the HO-1 gene (hmox1) is frequently activated under a variety of cellular stress conditions. Cells use multiple signaling pathways and transcription factors to fine-tune their response to a specific circumstance. Among these factors, members of the heat-shock factor, nuclear factor-kappaB, nuclear factor-erythroid 2, and activator protein-1 families are arguably the most important regulators of the cellular stress response in vertebrates. Although there is functional overlap between individual families, each broadly regulates different aspects of the cellular stress response and thus, with some exceptions, modulates the expression of different sets of targets genes. To the best of our knowledge, hmox1 is unique in that it is proposed to be directly regulated by all four of these stress-responsive transcription factors. In this article we provide a review and analysis of the data supporting this proposition.

Constitutive overexpression of Nrf2-dependent heme oxygenase-1 in A549 cells contributes to resistance to apoptosis induced by epigallocatechin 3-gallate

Epigallocatechin 3-gallate (EGCG), the major polyphenol found in green tea, exerts antiproliferative and proapoptotic effects in many cancer cells. However, we found that among many cancer cells human lung adenocarcinoma A549 cells are markedly resistant to apoptosis induction by EGCG (even at 100 microm for 72 h). Heme oxygenase-1 (HO-1) induced by stress stimuli represents a prime cellular defense mechanism, but it may be associated with enhanced cell proliferation and chemoresistance in some cancer cells. Because we found that A549 cells constitutively overexpress HO-1 and its associated transcription factor Nrf2, we tested an hypothesis that EGCG resistance in these cells may be linked with Nrf2-mediated HO-1 overexpression. HO-1 inhibition with tin-protoporphyrin IX and silencing with RNA interference rendered cells more sensitive to apoptosis induction by EGCG and classical prooxidants. Interestingly, EGCG at high concentration (>200 microm) induced apoptosis by suppressing expression of HO-1 protein and mRNA, and this effect correlated with a decrease in both Nrf2-ARE binding and HO-1-ARE-luciferase activity, suggesting Nrf2-driven transcriptional activation of ho-1. Because we observed notably high levels of phosphorylated protein kinase C alpha and its suppression by EGCG and deferoxamine (an iron chelator), a possible mechanism involving phosphorylated protein kinase C alpha and iron in Nrf2-HO-1 activation was further investigated. Collectively, our findings suggest that Nrf2-mediated HO-1 overexpression confers resistance to apoptosis induction by EGCG; therefore, its inactivation may be a target for overcoming the resistance to chemoprevention and chemotherapy.

Baicalein inhibition of oxidative-stress-induced apoptosis via modulation of ERKs activation and induction of HO-1 gene expression in rat glioma cells C6

In the present study, we examined the protective mechanism of baicalein (BE) and its glycoside, baicalin (BI), on hydrogen-peroxide (H(2)O(2))-induced cell death in rat glioma C6 cells. Results of the MTT assay, LDH release assay, and morphological observation showed that H(2)O(2) addition reduced the viability of C6 cells, and this was prevented by the addition of BE but not BI. Incubation of C6 cells with BE significantly decreased the intracellular peroxide level induced by H(2)O(2) according to flow cytometric analysis using DCHF-DA as a fluorescent substrate. Suppression of H(2)O(2)-induced apoptotic events including DNA ladders, hypodiploid cells, and activation of caspases 3, 8, and, 9 by BE but not BI was identified in C6 cells. The cytotoxicity and phosphorylation of ERK proteins induced by H(2)O(2) were blocked by the ERK inhibitor PD98059. Catalase addition prevented H(2)O(2)-induced ROS production, ERKs protein phosphorylation, and cell death, and BE dose-dependently inhibited H(2)O(2)-induced ERK protein phosphorylation in C6 cells. These data suggest that ROS-scavenging activity is involved in BE prevention of H(2)O(2)-induced cell death via blocking ERKs activation. Additionally, BE but not BI induced heat shock protein 32 (HSP32; HO-1) protein expression in both time- and dose-dependent manners, but not heme oxygenase 2 (HO-2), heat shock protein 70 (HSP70), or heat shock protein 90 (HSP90) protein expression. In the absence of H(2)O(2), BE induces ERKs protein phosphorylation, and HO-1 protein expression induced by BE was blocked by the addition of cycloheximide, actinomycin D, and the ERK inhibitor PD98059. The addition of the HO inhibitor ZnPP inhibited the protective effect of BE against H(2)O(2)-induced cytotoxicity in C6 cells according to the MTT assay and apoptotic morphology under microscopic observation, accompanied by blocking the ROS-scavenging activity of BE in C6 cells. However, BE treatment was unable to protect C6 cells from C2-ceramide-induced cell death. These data indicate that BE possesses abilities to inhibit ROS-mediated cytotoxic effects through modulation of ERKs activation and induction of HO-1 protein expression. The role of HO-1 in ROS-scavenging activity of BE is proposed.

Heme oxygenase-1/carbon monoxide: from basic science to therapeutic applications

The heme oxygenases, which consist of constitutive and inducible isozymes (HO-1, HO-2), catalyze the rate-limiting step in the metabolic conversion of heme to the bile pigments (i.e., biliverdin and bilirubin) and thus constitute a major intracellular source of iron and carbon monoxide (CO). In recent years, endogenously produced CO has been shown to possess intriguing signaling properties affecting numerous critical cellular functions including but not limited to inflammation, cellular proliferation, and apoptotic cell death. The era of gaseous molecules in biomedical research and human diseases initiated with the discovery that the endothelial cell-derived relaxing factor was identical to the gaseous molecule nitric oxide (NO). The discovery that endogenously produced gaseous molecules such as NO and now CO can impart potent physiological and biological effector functions truly represented a paradigm shift and unraveled new avenues of intense investigations. This review covers the molecular and biochemical characterization of HOs, with a discussion on the mechanisms of signal transduction and gene regulation that mediate the induction of HO-1 by environmental stress. Furthermore, the current understanding of the functional significance of HO shall be discussed from the perspective of each of the metabolic by-products, with a special emphasis on CO. Finally, this presentation aspires to lay a foundation for potential future clinical applications of these systems.

Heme oxygenase-1 inhibits apoptosis in Caco-2 cells via activation of Akt pathway

Heme oxygenase-1 can play a protective role against cellular stress. In colon cancer cells, these effects would be relevant to oncogenesis and resistance to chemotherapy. The aim of the study was to examine the effects of heme oxygenase-1 induction on cell survival in a human colon cancer cell line, Caco-2. Serum deprivation induced apoptosis, reduced Akt and p38 phosphorylation, and increased p21(Cip/WAF1) levels. Heme oxygenase-1 induction by treatment with cobalt protoporphyrin IX resulted in resistance to apoptosis, activation of Akt, reduction in p21(Cip/WAF1) levels and modification of bcl2/bax ratio towards survival. Indomethacin reduced apoptosis but in contrast to heme oxygenase-1, arrested cells in G0/G1. Apoptosis was also inhibited by the heme oxygenase metabolites bilirubin and biliverdin but the CO donor tricarbonyldichlororuthenium(II) dimer did not exert significant effects. Protection against apoptosis in cells treated with cobalt protoporphyrin IX was reverted by incubation with heme oxygenase-1 small interfering RNA. This study shows an antiapoptotic effect of heme oxygenase-1 in colon cancer cells which could be mediated by the formation of bilirubin and biliverdin. Our results support an antiapoptotic role for HO-1 in these cells and provide a mechanism by which overexpression of HO-1 may promote tumor resistance to stress in conditions of limited nutrient supply. We have extended these observations by demonstrating that these effects are independent of p38 but are mediated via Akt pathway.

Metalloporphyrins inactivate caspase-3 and -8

Activation of caspases represents one of the earliest biochemical indicators for apoptotic cell death. Therefore, measurement of caspase activity is a widely used and generally accepted method to determine apoptosis in a wide range of in vivo and in vitro settings. Numerous publications characterize the role of the heme-catabolizing enzyme heme oxygenase-1 (HO-1) in regulating apoptotic processes. Different metalloporphyrins representing inducers and inhibitors of this enzyme are often used, followed by assessment of apoptotic cell death. In the present work, we found that caspase-3-like activity, as well as activity of caspase-8 measured in either Fas (CD95) ligand-treated Jurkat T-lymphocytes or by the use of recombinant caspase-3 or -8, was inhibited by different metalloporphyrins (cobalt(III) protoporphyrin IX, tin and zinc(II) protoporphyrin-IX). Moreover, employing the mouse model of Fas-induced liver apoptosis these properties of porphyrins could also be demonstrated in vivo. The metalloporphyrins were shown to inhibit caspase-3-mediated PARP cleavage. Molecular modeling studies demonstrated that porphyrins can occupy the active site of caspase-3 in an energetically favorable manner and in a binding mode similar to that of known inhibitors. The data shown here introduce metalloporphyrins as direct inhibitors of caspase activity. This finding points to the need for careful employment of metalloporphyrins as modulators of HO-1.

Heme as key regulator of major mammalian cellular functions: molecular, cellular, and pharmacological aspects

Heme (iron protoporphyrin IX) exists as prosthetic group in several hemoproteins, which include respiration cytochromes, gas sensors, P450 enzymes (CYPs), catalases, peroxidases, nitric oxide synthases (NOS), guanyl cyclases, and even transcriptional factors. Hemin (the oxidized form of iron protoporphyrin IX) on the other hand is an essential regulator of gene expression and growth promoter of hematopoietic progenitor cells. This review is focused on the major developments occurred in this field of heme biosynthesis and catabolism and their implications in our understanding the pathogenesis of heme-related disorders like anemias, acute porphyrias, hematological malignancies (leukemias), and other disorders. Heme is transported into hematopoietic cells and enters the nucleus where it activates gene expression by removing transcriptional potential repressors, like Bach1, from enhancer DNA sequences. Evidence also exists to indicate that heme acts like a signaling ligand in cell respiration and metabolism, stress response adaptive processes, and even transcription of several genes. Impaired heme biosynthesis or heme deficiency lead to hematological disorders, tissue degeneration, and aging, while heme prevents cell damage via activation of heme oxygenase-1 (HO-1) gene. Therefore, heme, besides being a key regulator of mammalian functions, can be also a useful therapeutic agent alone or in combination with other drugs in several heme-related disorders.

Heme oxygenase-1 inhibits rat and human breast cancer cell proliferation: mutual cross inhibition with indoleamine 2,3-dioxygenase

Heme oxygenase-1 (HO-1) is the rate limiting enzyme of heme catabolism whereas indoleamine 2,3 dioxygenase (IDO) catabolizes tryptophan through the kynurenine pathway. We analyzed the expression and biological effects of these enzymes in rat and human breast cancer cell lines. We show that rat (NMU and 13762) but not human cells (MCF-7 and T47D) express HO-1. When overexpressed, we found this enzyme to have anti-proliferative and proapoptotic effects by antioxidant mechanisms in these four cell lines. We show that IDO is expressed by rat and human breast cancer cells. IDO inhibition with 1-MT and siRNA leads to diminished proliferation in rat cells. In contrast, HO-1 negative human cell lines increase proliferation upon IDO inhibition. Since we also demonstrate that IDO inhibits the anti-proliferative HO-1, we propose that IDO has opposite effects on proliferation depending on the coexpression or not of HO-1. We also describe that HO-1 inhibits IDO at the post-translational level through heme starvation. In vivo, we show that rat normal breast expresses HO-1 and IDO. In contrast, N-nitrosomethylurea-induced breast adenocarcinomas only express IDO. In conclusion, we show that HO-1/IDO cross-regulation modulates apoptosis and proliferation in rat and human breast cancer cells.

T cell epitope definition by differential mass spectrometry: Identification of a novel, immunogenic HLA-B8 ligand directly from renal cancer tissue

In this study, we describe a differential mass spectrometric technique for the immuno-proteomic analysis of the major histocompatibility complex (MHC) peptides of a renal cell carcinoma (RCC) biopsy compared with the healthy kidney tissue of the same patient after nephrectomy. Using a stable isotope labeling approach, we could directly compare and relatively quantify 43 MHC-peptide pairs, most of which were present in similar proportions on both normal kidney and tumor. Significantly, two dominant peptides of monoisotopic masses ([M+H](+)) 973.43 u and 967.59 u, respectively, were found exclusively in the tumor sample. One of these was identified as originating from heme oxygenase-1 (HO-1), a protein involved in induction of apoptosis resistance, immuno-suppression and neoangiogenesis and reported to be up-regulated in various cancer types. Moreover, the corresponding synthetic HO-1-derived peptide was shown to be immunogenic in vitro by generation of CD8+ T cell lines with peptide-specific cytolytic activity. Thus, this peptide is an example of a differentially identified T cell epitope that could be considered as a target for immunotherapy.

Inhibition of heme oxygenase-1 by zinc protoporphyrin IX reduces tumor growth of LL/2 lung cancer in C57BL mice

Heme oxygenase (HO)-1 is a key player reducing cytotoxicity and enhancing protumoral effects of nitric oxide (NO). We examined zinc protoporphyrin (ZnPP) IX, an HO-1 inhibitor, to affect tumor growth of LL/2 mouse lung cancer cells. ZnPPIX reduced HO-1 expression and HO activity in LL/2 cells, whereas cobalt PPIX (CoPPIX), an HO-1 activator, increased both. LL/2 cells treated with sodium nitropurusside, an NO donor, showed growth inhibition dose-dependently, which was enhanced by ZnPPIX cotreatment, but was reduced by CoPPIX. In mice tumors, ZnPPIX decreased HO-1 expression. LL/2-tumors were found in 88% (7/8) vehicle-treated mice, whereas tumors were found in 38% (3/8) and 25% (2/8) mice treated with 5 and 20 microg/mouse ZnPPIX, respectively (p = 0.0302). Tumor growth was inhibited dose-dependently by ZnPPIX. Vascular endothealial growth factor concentration in tumors was reduced by ZnPPIX (p = 0.0341). Microvessel density (MVD) in ZnPPIX-treated tumors was lower than that in vehicle-treated tumors (p = 0.0362). Apoptotic cell count in ZnPPIX-treated tumors was higher than that in vehicle-treated tumors (p = 0.0003). In contrast, CoPPIX treatment increased HO-1 expression, enhanced tumorigenicity and MVD and reduced apoptosis. From these findings, inhibition of HO-1 by ZnPPIX provides relevant antitumoral effects.

Involvement of Nrf2, p38, B-Raf, and nuclear factor-kappaB, but not phosphatidylinositol 3-kinase, in induction of hemeoxygenase-1 by dietary polyphenols

The highly inducible enzyme, hemeoxygenase-1 (HO-1), metabolizes heme, thereby protecting a variety of cells against oxidative stress and apoptosis. Up-regulation by cancer chemopreventive agents has been reported, but its regulation and function in transformed cells are unclear. We compared induction by two dietary polyphenols, curcumin and epigallocatechin-3-gallate (EGCG), with that by the endogenous substrate hemin in epithelial and endothelial cells and examined the relevance to apoptosis. Curcumin or hemin (20 microM) induced HO-1 in breast cells from 5 to 24 h. Curcumin (5-40 microM) or hemin (5-100 microM) induced HO-1 and nuclear levels of nuclear factor (erythroid-derived 2)-related factor (Nrf2) in a dose-dependent manner. EGCG had no effect in breast cells, but at 30 microM, it induced nuclear translocation of Nrf2 and HO-1 expression in B-lymphoblasts. In all cases, induction was inhibited by pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) or the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580). The nuclear factor-kappaB (NF-kappaB)-DNA binding inhibitor helenalin (20 microM) also prevented induction. However, wortmannin had no effect, suggesting that PI3K was not involved. Curcumin and hemin also induced nuclear Nrf2 and HO-1 effectively in wild-type mouse embryo fibroblasts (wt MEFs) and in B-Raf(-/-) MEFs but not in Nrf2(-/-) MEFs. However, EGCG (5-20 microM) induced HO-1 only in wt MEFs. Results suggest that signaling through p38 mitogen-activated protein kinase, NF-kappaB, and Nrf2 as well as other unidentified molecules is involved in HO-1 induction by hemin and both polyphenols, but cell-specific factors also play a role, particularly with respect to EGCG. Induction of HO-1 by curcumin, EGCG, or low concentrations (5-10 microM) of helenalin did not protect MDA-MB468 breast cells or B-lymphoblasts from apoptosis.

Association of genetic polymorphisms of MK, IL-4, p16, p21, p53 genes and human gastric cancer in Taiwan

AIMS

To assess gastric cancer risk and clinical-pathological factors associated with genetic polymorphisms of MK, IL-4, p16, p21 and p53 genes.

METHODS

A retrospective study was conducted for 123 patients who had recently developed primary gastric cancer. Clinical data and pathological findings were collected, genetic polymorphisms of MK, IL-4, p16, p21 and p53 genes were analysed, and the associations of genetic polymorphisms with gastric cancer carcinogenesis were evaluated.

RESULTS

There was significant association of genetic polymorphisms between gastric cancer and control groups in p53 genes. After further stratification of the cancer group into different clinical-pathologic parameters, there were significant associations in the sex and LN involvement groups in MK gene; alcohol consumption group in p16 gene; age and cell differentiation groups in p21 gene; age and tumour location groups in p53 gene; but we fail to find any significant association with IL-4 gene polymorphisms.

CONCLUSIONS

Genetic susceptibility testing is a tool to evaluate the association of genetic polymorphisms with gastric cancer carcinogenesis.

Molecular basis of heme oxygenase-1 induction: implications for chemoprevention and chemoprotection

Heme oxygenase (HO)-1, involved in the heme degradation process, is an important antioxidant enzyme. The induction of HO-1 gene expression, in response to diverse oxidative stimuli, represents a critical event in adaptive cellular response. Experimental models of various diseases, including acute inflammation, atherosclerosis, degenerative diseases, and carcinogenesis, have demonstrated that the induction of HO-1 can prevent or mitigate the symptoms associated with these ailments. Recent progress in our understanding of cellular signaling networks as critical modulators of gene transcription sheds light on the molecular basis of HO-1 gene expression. A panel of redox-sensitive transcription factors such as activator protein-1, nuclear factor- kappaB, and nuclear factor E2-related factor-2, and some of the upstream kinases have been identified as regulators of HO-1 gene induction. The scope of this review is limited to focus on molecular mechanisms underlying HO-1 expression and the significance of targeted induction of HO-1 as a strategy to achieve chemoprevention and chemoprotection.

Heme oxygenase 1 (HO‐1) regulates osteoclastogenesis and bone resorption

Heme oxygenase 1 (HO-1) plays an important role in vascular disease, transplantation, and inflammation. In animal models of acute and chronic inflammation, induction of HO-1 has anti-inflammatory and cytoprotective properties. Since inflammation is an important trigger of osteoclastogenesis, we hypothesized that HO-1 might influence osteoclastogenesis. We investigated the effects of induction of HO-1 on osteoclast formation in vitro and in vivo. Furthermore, we addressed the role of HO-1 in inflammatory bone loss in humans. When HO-1 was induced by hemin in vitro, a significant dose-dependent inhibition of osteoclastogenesis was observed. Up-regulation of HO-1 was mediated by activation of MAPK and primarily prevented differentiation of osteoclast precursors to osteoclasts, whereas it did not affect mature osteoclasts. Anti-osteoclastogenic properties of hemin were based on a down-regulation of c-fms, RANK, TRAF-6, and c-fos. In addition, induction of HO-1 inhibited TNF-triggered osteoclast differentiation in vitro as well as LPS-driven inflammatory bone loss in vivo. Furthermore, HO-1 induction suppressed osteoclastogenesis and bone destruction in a TNF-mediated arthritis. In line, assessment of synovial tissue from rheumatoid arthritis patients revealed that osteoclasts are usually HO-1 negative. Moreover, serum levels of bilirubin, a metabolite of HO-1, were elevated in rheumatoid arthritis patients without bone damage, suggesting HO-1 affects bone loss in humans. In summary, these data indicate that HO-1 negatively regulates osteoclastogenesis, leading to a positive net balance of bone.

Targeted inhibition of p38alpha MAPK suppresses tumor-associated endothelial cell migration in response to hypericin-based photodynamic therapy

Photodynamic therapy (PDT) is an established anticancer modality and hypericin is a promising photosensitizer for the treatment of bladder tumors. We show that exposure of bladder cancer cells to hypericin PDT leads to a rapid rise in the cytosolic calcium concentration which is followed by the generation of arachidonic acid by phospholipase A2 (PLA2). PLA2 inhibition significantly protects cells from the PDT-induced intrinsic apoptosis and attenuates the activation of p38 MAPK, a survival signal mediating the up-regulation of cyclooxygenase-2 that converts arachidonic acid into prostanoids. Importantly, inhibition of p38alpha MAPK blocks the release of vascular endothelial growth factor and suppresses tumor-promoted endothelial cell migration, a key step in angiogenesis. Hence, targeted inhibition of p38alpha MAPK could be therapeutically beneficial to PDT, since it would prevent COX-2 expression, the inducible release of growth and angiogenic factors by the cancer cells, and cause an increase in the levels of free arachidonic acid, which promotes apoptosis.

Transcriptome analysis of human colon Caco-2 cells exposed to sulforaphane

Sulforaphane (SF), a dietary phytochemical obtained from broccoli, has been implicated in several physiological processes consistent with anticarcinogenic activity, including enhanced xenobiotic metabolism, cell cycle arrest, and apoptosis. In this study, we report changes in global gene expression in Caco-2 cells exposed to physiologically appropriate concentrations of SF, through the use of replicated Affymetrix array and RT-PCR experiments. After exposure to 50 micromol/L SF, 106 genes exhibited a >2-fold increase in expression and 63 genes exhibited a >2-fold decrease in expression. There were fewer changes in gene expression at lower SF concentrations. The majority of these genes had not previously been shown to be modulated by SF, suggesting novel mechanisms of possible anticarcinogenic activity, including induction of differentiation and modulation of fatty acid metabolism. The changes in the expression of 10 of these genes, together with 4 additional genes of biological interest, were further quantified in independent studies with RT-PCR. These genes include several that have recently become associated with carcinogenesis, such as Krüppel-like factor (KLF)4, a gut-enriched transcription factor associated with induction of differentiation and reduction in cellular proliferation; DNA (cytosine-5-)-methyltransferase 1, associated with methylation; and alpha-methylacyl-CoA racemase (AMACR), a marker associated with the development of colon and prostate cancer. The expression of 5 of these genes [caudal type homeo box transcription factor 2 (CDX-2), KLF4, KLF5, cyclin-dependent kinase inhibitor 1A (p21), and AMACR] was additionally studied after in vitro exposure to SF of surgically resected healthy and cancerous colon tissue from each of 3 patients. The study suggests the complex effects that SF has on gene expression and highlights several potential mechanisms by which the consumption of broccoli may reduce the risk of carcinogenesis.

The mTOR inhibitor RAD001 sensitizes tumor cells to DNA-damaged induced apoptosis through inhibition of p21 translation

Although DNA damaging agents have revolutionized chemotherapy against solid tumors, a narrow therapeutic window combined with severe side effects has limited their broader use. Here we show that RAD001 (everolimus), a rapamycin derivative, dramatically enhances cisplatin-induced apoptosis in wild-type p53, but not mutant p53 tumor cells. The use of isogenic tumor cell lines expressing either wild-type mTOR cDNA or a mutant that does not bind RAD001 demonstrates that the effects of RAD001 are through inhibition of mTOR function. We further show that RAD001 sensitizes cells to cisplatin by inhibiting p53-induced p21 expression. Unexpectedly, this effect is attributed to a small but significant inhibition of p21 translation combined with its short half-life. These findings provide the molecular rationale for combining DNA damaging agents with RAD001, showing that a general effect on a major anabolic process may dramatically enhance the efficacy of an established drug protocol in the treatment of cancer patients with solid tumors.

NF-κB as a molecular target in adjuvant therapy of gastrointestinal carcinomas

AIM

To describe the role of nuclear factor-kappa B (NF-kappaB) in cancer treatment.

METHODS

We searched the Pubmed database (until Oct, 2004) with the keywords of gastrointestinal carcinoma, NF-kappaB, inhibitor, cancer treatment molecular target and chemoresistance. We reviewed the literature in the role of NF-kappaB activation in chemoresistance, tumour growth suppression and enhancement of apoptosis in gastrointestinal carcinomas.

CONCLUSIONS

Several possible strategies for inhibiting NF-kappaB activation are identified. The importance of targeting NF-kappaB as a potential therapeutic approach in clinical medicine was discussed.

Aging-associated changes in gene expression in the ACI rat prostate: Implications for carcinogenesis

BACKGROUND

Prostate cancer is the most frequently diagnosed neoplasm and the second leading cause of cancer-related mortality in men. Although the incidence of prostate cancer increases with age, the link between aging and prostate cancer is poorly understood.

METHODS

Affymetrix oligonucleotide microarrays were used to analyze the mRNA expression levels in the dorsolateral prostates from 6- and 18-month-old ACI rats. Real-time RT-PCR and immunohistochemistry was performed to validate microarray data in a select set of genes.

RESULTS

Microarray analysis revealed changes in gene expression associated with inflammation, oxidative stress, tissue remodeling, and energy metabolism. Most of these changes have been related to increased proliferative status of the prostate, anti-apoptosis, activated stroma, and alteration of the energy metabolism.

CONCLUSIONS

Age-associated alterations in the gene expression profile may put the aging prostate in risk for the initiation, promotion, and progression of neoplastic transformation in both our animal model and humans.

Association between endogenous gene expression and growth regulation induced by TGF-β1 in human gastric cancer cells

AIM: To investigate the association between endogenous gene expression and growth regulation including proliferation and apoptosis induced by transforming growth factor-β1 (TGF-β1) in human gastric cancer (GC) cells.

METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was performed to detect the main components of the TGF-β1/Smads signal pathway in human poorly differentiated GC cell line BGC-823. Localization of Smad proteins was also determined using immunofluorescence. Then, the BGC-823 cells were cultured in the presence or absence of TGF-β1 (10 ng/mL) for 24 and 48 h, and the effects of TGF-β1 on proliferation and apoptosis were measured by cell growth curve and flow cytometry (FCM) analysis. The ultrastructural features of BGC-823 cells with or without TGF-β1 treatment were observed under transmission electron microscope. The apoptotic cells were visualized by means of the terminal deoxynucleotidyl transferase (TdT)-mediated dTUP in situ nick end-labeling (TUNEL) method. Meanwhile, the expression levels of endogenous p15,p21 and Smad7 mRNA and the corresponding proteins in the cells were detected at 1, 2 and 3 h after culture in the presence or absence of TGF-β1 (10 ng/mL) by semi-quantitative RT-PCR and Western blot, respectively.

RESULTS: The TGF-β1/Smad signaling was found to be intact and functional in BGC-823 cells. The growth curve revealed the most evident inhibition of cell proliferation by TGF-β1 at 48 h, and FCM assay showed G1 arrest accompanied with apoptosis induced by TGF-β1. The typical morphological changes of apoptosis were observed in cells exposed to TGF-β1. The apoptosis index (AI) in TGF-β1-treated cells was significantly higher than that in the untreated controls (10.7±1.3% vs 0.32±0.06%, P<0.01). The levels of p15,p21 and Smad7 mRNA and corresponding proteins in cells were significantly up-regulated at 1 h, but gradually returned to basal levels at 3 h following TGF-β1 (10 ng/mL) treatment.

CONCLUSION: TGF-β1 affects both proliferation and apoptosis of GC cells through the regulation of p15 and p21, and induces transient expression of Smad 7 as a negative feedback modulation of TGF-β1 signal. Our results suggest a novel functional role of p21 as an accelerant of TGF-β1-mediated apoptosis in GC cells.

Survivin and p53 modulate quercetin-induced cell growth inhibition and apoptosis in human lung carcinoma cells

Quercetin, a ubiquitous bioactive plant flavonoid, has been shown to inhibit the proliferation of cancer cells. However, the regulation of survivin and p53 on the quercetin-induced cell growth inhibition and apoptosis in cancer cells remains unclear. In this study, we investigated the roles of survivin and p53 in the quercetin-treated human lung carcinoma cells. Quercetin (20-80 mum for 24 h) induced the cytotoxicity and apoptosis in both A549 and H1299 lung carcinoma cells in a concentration-dependent manner. Additionally, quercetin inhibited the cell growth, increased the fractions of G(2)/M phase, and raised the levels of cyclin B1 and phospho-cdc2 (threonine 161) proteins. Moreover, quercetin induced abnormal chromosome segregation in H1299 cells. The survivin proteins were highly expressed in mitotic phase and were located on the midbody of cytokinesis; however, the survivin proteins were increased and concentrated on the nuclei following quercetin treatment in the lung carcinoma cells. Transfection of a survivin antisense oligodeoxynucleotide enhanced the quercetin-induced cell growth inhibition and cytotoxicity. Subsequently, quercetin increased the levels of total p53 (DO-1), phospho-p53 (serine 15), and p21 proteins, which were translocated to the nuclei in A549 cells. Treatment with a specific p53 inhibitor, pifithrin-alpha, or transfection of a p53 antisense oligodeoxynucleotide enhanced the cytotoxicity of the quercetin-treated cells. Furthermore, transfection of a small interfering RNA of p21 enhanced the quercetin-induced cell death in A549 cells. Together, our results suggest that survivin can reduce the cell growth inhibition and apoptosis, and p53 elevates the p21 level, which may attenuate the cell death in the quercetin-treated human lung carcinoma cells.