Heme oxygenase inhibition in cancers: possible tools and targets

Computational screening of pathogenic missense nsSNPs in heme oxygenase 1 (HMOX1) gene and their structural and functional consequences

Heme Oxygenase 1 (HMOX1) is a cytoprotective enzyme, exhibiting the highest activity in the spleen, catalyzing the heme ring breakdown into products of biological significance- biliverdin, CO, and Fe2+. In vascular cells, HMOX1 possesses strong anti-apoptotic, antioxidant, anti-proliferative, anti-inflammatory, and immunomodulatory actions. The majority of these activities are crucial for the prevention of atherogenesis. Single amino acid substitutions in proteins generated by missense non-synonymous single nucleotide polymorphism (nsSNPs) in the protein-encoding regions of genes are potent enough to cause significant medical challenges due to the alteration of protein structure and function. The current study aimed at characterizing and analyzing high-risk nsSNPs associated with the human HMOX1 gene. Preliminary screening of the total available 288 missense SNPs was performed through the lens of deleteriousness and stability prediction tools. Finally, a total of seven nsSNPs (Y58D, A131T, Y134H, F166S, F167S, R183S and M186V) were found to be most deleterious by all tools that are present at highly conserved positions. Molecular dynamics simulations (MDS) analysis explained the mutational effects on the dynamic action of the wild-type and mutant proteins. In a nutshell, R183S (rs749644285) was identified as a highly detrimental mutation that could significantly render the enzymatic activity of HMOX1. The finding of this computational analysis might help subject the experimental confirmatory analysis to characterize the role of nsSNPs in HMOX1.Communicated by Ramaswamy H. Sarma.

Putative Molecular Mechanisms Underpinning the Inverse Roles of Mitochondrial Respiration and Heme Function in Lung Cancer and Alzheimer's Disease

Mitochondria are the powerhouse of the cell. Mitochondria serve as the major source of oxidative stress. Impaired mitochondria produce less adenosine triphosphate (ATP) but generate more reactive oxygen species (ROS), which could be a major factor in the oxidative imbalance observed in Alzheimer's disease (AD). Well-balanced mitochondrial respiration is important for the proper functioning of cells and human health. Indeed, recent research has shown that elevated mitochondrial respiration underlies the development and therapy resistance of many types of cancer, whereas diminished mitochondrial respiration is linked to the pathogenesis of AD. Mitochondria govern several activities that are known to be changed in lung cancer, the largest cause of cancer-related mortality worldwide. Because of the significant dependence of lung cancer cells on mitochondrial respiration, numerous studies demonstrated that blocking mitochondrial activity is a potent strategy to treat lung cancer. Heme is a central factor in mitochondrial respiration/oxidative phosphorylation (OXPHOS), and its association with cancer is the subject of increased research in recent years. In neural cells, heme is a key component in mitochondrial respiration and the production of ATP. Here, we review the role of impaired heme metabolism in the etiology of AD. We discuss the numerous mitochondrial effects that may contribute to AD and cancer. In addition to emphasizing the significance of heme in the development of both AD and cancer, this review also identifies some possible biological connections between the development of the two diseases. This review explores shared biological mechanisms (Pin1, Wnt, and p53 signaling) in cancer and AD. In cancer, these mechanisms drive cell proliferation and tumorigenic functions, while in AD, they lead to cell death. Understanding these mechanisms may help advance treatments for both conditions. This review discusses precise information regarding common risk factors, such as aging, obesity, diabetes, and tobacco usage.

Ergolide mediates anti-cancer effects on metastatic uveal melanoma cells and modulates their cellular and extracellular vesicle proteomes

Background

Uveal melanoma is a poor prognosis cancer. Ergolide, a sesquiterpene lactone isolated from Inula Brittanica, exerts anti-cancer properties. The objective of this study was to 1) evaluate whether ergolide reduced metastatic uveal melanoma (MUM) cell survival/viability in vitro and in vivo; and 2) to understand the molecular mechanism of ergolide action.

Methods

Ergolide bioactivity was screened via long-term proliferation assay in UM/MUM cells and in zebrafish MUM xenograft models. Mass spectrometry profiled proteins modulated by ergolide within whole cell or extracellular vesicle (EVs) lysates of the OMM2.5 MUM cell line. Protein expression was analyzed by immunoblots and correlation analyses to UM patient survival used The Cancer Genome Atlas (TCGA) data.

Results

Ergolide treatment resulted in significant, dose-dependent reductions (48.5 to 99.9%; p<0.0001) in OMM2.5 cell survival in vitro and of normalized primary zebrafish xenograft fluorescence (56%; p<0.0001) in vivo, compared to vehicle controls. Proteome-profiling of ergolide-treated OMM2.5 cells, identified 5023 proteins, with 52 and 55 proteins significantly altered at 4 and 24 hours, respectively ( p<0.05; fold-change >1.2). Immunoblotting of heme oxygenase 1 (HMOX1) and growth/differentiation factor 15 (GDF15) corroborated the proteomic data. Additional proteomics of EVs isolated from OMM2.5 cells treated with ergolide, detected 2931 proteins. There was a large overlap with EV proteins annotated within the Vesiclepedia compendium. Within the differentially expressed proteins, the proteasomal pathway was primarily altered. Interestingly, BRCA2 and CDKN1A Interacting Protein (BCCIP) and Chitinase Domain Containing 1 (CHID1), were the only proteins significantly differentially expressed by ergolide in both the OMM2.5 cellular and EV isolates and they displayed inverse differential expression in the cells versus the EVs.

Conclusions

Ergolide is a novel, promising anti-proliferative agent for UM/MUM. Proteomic profiling of OMM2.5 cellular/EV lysates identified candidate pathways elucidating the action of ergolide and putative biomarkers of UM, that require further examination.

The dual role of heme oxygenase in regulating apoptosis in the nervous system of Drosophila melanogaster

Accumulating evidence from mammalian studies suggests the dual-faced character of heme oxygenase (HO) in oxidative stress-dependent neurodegeneration. The present study aimed to investigate both neuroprotective and neurotoxic effects of heme oxygenase after the ho gene chronic overexpression or silencing in neurons of Drosophila melanogaster. Our results showed early deaths and behavioral defects after pan-neuronal ho overexpression, while survival and climbing in a strain with pan-neuronal ho silencing were similar over time with its parental controls. We also found that HO can be pro-apoptotic or anti-apoptotic under different conditions. In young (7-day-old) flies, both the cell death activator gene (hid) expression and the initiator caspase Dronc activity increased in heads of flies when ho expression was changed. In addition, various expression levels of ho produced cell-specific degeneration. Dopaminergic (DA) neurons and retina photoreceptors are particularly vulnerable to changes in ho expression. In older (30-day-old) flies, we did not detect any further increase in hid expression or enhanced degeneration, however, we still observed high activity of the initiator caspase. In addition, we used curcumin to further show the involvement of neuronal HO in the regulation of apoptosis. Under normal conditions, curcumin induced both the expression of ho and hid, which was reversed after exposure to high-temperature stress and when supplemented in flies with ho silencing. These results indicate that neuronal HO regulates apoptosis and this process depends on ho expression level, age of flies, and cell type.

Deoxyshikonin Mediates Heme Oxygenase-1 Induction and Apoptotic Response via p38 Signaling in Tongue Cancer Cell Lines

Deoxyshikonin (DSK), a phytochemical constituent, has been documented to elicit various oncostatic properties alone or in combination with established therapeutics. However, its role in restraining oral squamous cell carcinoma (OSCC) is mostly unclear. Here, we examined the tumor-suppressive effect of DSK and explored the molecular mechanisms underlying DSK’s activities on controlling oral cancer. Our results showed that DSK dose-dependently lessened the cell viability of tongue cancer cell lines, involving induction of cell cycle arrest at the sub-G1 phase and apoptotic cell death. Moreover, a unique signature of apoptosis-related proteins, including augmented nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) expression and caspase activation, was observed in DSK-treated tongue cancer cell lines. Furthermore, DSK-mediated upregulation of HO-1 and cleavage of caspase-9 and -3 were significantly inhibited by pharmacological blockage of p38 kinase. Collectively, these data revealed that DSK halted cell cycle progression and elicited cell apoptosis in tongue cancer cell lines, reshaping a p38-dependent profile of apoptotic proteome. Our findings provided novel insights into the therapeutic implications of a natural compound on the management of OSCC.

Role of Platelet-activating factor and HO-1 in mediating the protective effect of rupatadine against 5-fluorouracil-induced hepatotoxicity in rats

5-fluorouracil (5-FU) is a widely used chemotherapeutic drug, but its hepatotoxicity challenges its clinical use. Thus, searching for a hepatoprotective agent is highly required to prevent the accompanied hepatic hazards. The current study aimed to investigate the potential benefit and mechanisms of action of rupatadine (RU), a Platelet-activating factor (PAF) antagonist, in the prevention of 5-FU-related hepatotoxicity in rats. Hepatotoxicity was developed in male albino rats by a single 5-FU (150 mg/kg) intra-peritoneal injection on the 7th day of the experiment. RU (3 mg/kg/day) was orally administrated to the rodents for 10 days. Hepatic toxicity was assessed by measuring both liver and body weights, serum alanine aminotransferase and aspartate aminotransferase (ALT and AST), hepatic oxidative stress parameters (malondialdehyde (MDA), nitric oxide levels (NOx), reduced glutathione (GSH), superoxide dismutase (SOD)), and heme oxygenase-1 (HO-1). Inflammatory markers expressions (inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNFα), interleukins; IL-1B, IL-6), the apoptotic marker (caspase-3), and PAF were measured in the hepatic tissue. 5-FU-induced hepatotoxicity was proved by the biochemical along with histopathological assessments. RU ameliorated 5-FU-induced liver damage as proved by the improved serum ALT, AST, and hepatic oxidative stress parameters, the attenuated expression of hepatic pro-inflammatory cytokines and PAF, and the up-regulation of HO-1. Therefore, it can be concluded that RU pretreatment exerted a hepatoprotective effect against 5-FU-induced liver damage through both its powerful anti-inflammatory, antioxidant, and anti-apoptotic effect.

Targeting the NRF2/HO-1 Antioxidant Pathway in FLT3-ITD-Positive AML Enhances Therapy Efficacy

Acute myeloid leukemia (AML) is a molecularly heterogenous hematological malignancy, with one of the most common mutations being internal tandem duplication (ITD) of the juxtamembrane domain of the fms-like tyrosine kinase receptor-3 (FLT3). Despite the development of FLT3-directed tyrosine kinase inhibitors (TKI), relapse and resistance are problematic, requiring improved strategies. In both patient samples and cell lines, FLT3-ITD raises levels of reactive oxygen species (ROS) and elicits an antioxidant response which is linked to chemoresistance broadly in AML. NF-E2–related factor 2 (NRF2) is a transcription factor regulating the antioxidant response including heme oxygenase -1 (HO-1), a heat shock protein implicated in AML resistance. Here, we demonstrate that HO-1 is elevated in FLT3-ITD-bearing cells compared to FLT3-wild type (WT). Transient knockdown or inhibitor-based suppression of HO-1 enhances vulnerability to the TKI, quizartinib, in both TKI-resistant and sensitive primary AML and cell line models. NRF2 suppression (genetically or pharmacologically using brusatol) results in decreased HO-1, suggesting that TKI-resistance is dependent on an active NRF2-driven pathway. In AML-patient derived xenograft (PDX) models, brusatol, in combination with daunorubicin, reduces leukemia burden and prolongs survival. Cumulatively, these data encourage further development of brusatol and NRF2 inhibition as components of combination therapy for refractory AML.

Heme Oxygenase-1 Has a Greater Effect on Melanoma Stem Cell Properties Than the Expression of Melanoma-Initiating Cell Markers

Melanoma-initiating cells (MICs) contribute to the tumorigenicity and heterogeneity of melanoma. MICs are identified by surface and functional markers and have been shown to display cancer stem cell (CSC) properties. However, the existence of MICs that follow the hierarchical CSC model has been questioned by studies showing that single unselected melanoma cells are highly tumorigenic in xenotransplantation assays. Herein, we characterize cells expressing MIC markers (CD20, CD24, CD133, Sca-1, ABCB1, ABCB5, ALDH^high) in the B16-F10 murine melanoma cell line. We use flow cytometric phenotyping, single-cell sorting followed by in vitro clonogenic assays, and syngeneic in vivo serial transplantation assays to demonstrate that the expression of MIC markers does not select CSC-like cells in this cell line. Previously, our group showed that heme-degrading enzyme heme oxygenase-1 (HO-1) can be upregulated in melanoma and increase its aggressiveness. Here, we show that HO-1 activity is important for non-adherent growth of melanoma and HO-1 overexpression enhances the vasculogenic mimicry potential, which can be considered protumorigenic activity. However, HO-1 overexpression decreases clone formation in vitro and serial tumor initiation in vivo. Thus, HO-1 plays a dual role in melanoma, improving the progression of growing tumors but reducing the risk of melanoma initiation.

Short-Term Fasting Synergizes with Solid Cancer Therapy by Boosting Antitumor Immunity

Simple Summary

Stimulating our body’s own immune response to fight cancer is important for the success of cancer treatment in general. To further improve current cancer therapy, preclinical research shows that short-term fasting diets enhance cancer therapy efficacy, such as chemotherapy. Short-term fasting diets are low-caloric and low in protein for 3–5 days; they are usually done every couple of weeks. This review summarizes preclinical and clinical evidence of fasting diets synergizing with cancer therapy by boosting antitumor immunity.

Abstract

Short-term fasting (STF), using a low caloric, low protein fasting mimicking diet (FMD), appears to be a promising strategy to enhance chemotherapy-based cancer efficacy, while potentially alleviating toxicity. Preclinical results suggest that enhanced tumor immunity and decreased growth signaling, via lowering of circulating insulin and insulin growth factor 1 (IGF-1) levels form the potential underlying mechanisms. STF may boost anti-tumor responses by promoting tumor immunogenicity and decreasing local immunosuppression. These findings warrant further studies focused on the combination of STF, not only with chemotherapy, but also with immunotherapy to evaluate the full range of benefits of STF in cancer treatment. Here, we delineate the underlying anticancer mechanisms of fasting. We summarize preclinical evidence of STF boosting antitumor immunity and alleviating immunosuppression, as well as the clinical findings reporting the immunomodulatory effects of STF during various cancer treatments, including immunotherapy.

From Far West to East: Joining the Molecular Architecture of Imidazole-like Ligands in HO-1 Complexes

HO-1 overexpression has been reported in several cases/types of human malignancies. Unfortunately, poor clinical outcomes are reported in most of these cases, and the inhibition of HO-1 is considered a valuable and proven anticancer approach. To identify novel hit compounds suitable as HO-1 inhibitors, we report here a fragment-based approach where ligand joining experiments were used. The two most important parts of the classical structure of the HO-1 inhibitors were used as a starting point, and 1000 novel compounds were generated and then virtually evaluated by structure and ligand-based approaches. The joining experiments led us to a novel series of indole-based compounds. A synthetic pathway for eight selected molecules was designed, and the compounds were synthesized. The biological activity revealed that some molecules reach the micromolar activity, whereas molecule 4d inhibits the HO-1 with an IC₅₀ of 1.03 μM. This study suggested that our joining approach was successful, and a novel hit compound was generated. These results are ongoing for further development.

Association between HO‑1 gene promoter polymorphisms and diseases (Review)

Heme oxygenase‑1 (HO‑1) is an inducible cytoprotective enzyme that degrades heme into free iron, carbon monoxide and biliverdin, which is then rapidly converted into bilirubin. These degradation products serve an important role in the regulation of inflammation, oxidative stress and apoptosis. While the expression level of HO‑1 is typically low in most cells, it may be highly expressed when induced by a variety of stimulating factors, a process that contributes to the regulation of cell homeostasis. In the 5'‑non‑coding region of the HO‑1 gene, there are two polymorphic sites, namely the (GT)n dinucleotide and T(‑413)A single nucleotide polymorphism sites, which regulate the transcriptional activity of HO‑1. These polymorphisms have been shown to be closely associated with the occurrence and progression of numerous diseases, including cardiovascular, pulmonary, liver and kidney, various types of cancer and viral diseases. The present article reviews the progress that has been made in research on the association between the two types of polymorphisms and these diseases, which is expected to provide novel strategies for the diagnosis, treatment and prognosis of various diseases.

Protocatechuic Acid, a Simple Plant Secondary Metabolite, Induced Apoptosis by Promoting Oxidative Stress through HO-1 Downregulation and p21 Upregulation in Colon Cancer Cells

Gastrointestinal cancers, particularly colorectal cancer, are mainly influenced by the dietary factor. A diet rich in fruits and vegetables can help to reduce the incidence of colorectal cancer thanks to the phenolic compounds, which possess antimutagenic and anticarcinogenic properties. Polyphenols, alongside their well-known antioxidant properties, also show a pro-oxidative potential, which makes it possible to sensitize tumor cells to oxidative stress. HO-1 combined with antioxidant activity, when overexpressed in cancer cells, is involved in tumor progression, and its inhibition is considered a feasible therapeutic strategy in cancer treatment. In this study, the effects of protocatechuic acid (PCA) on the viability of colon cancer cells (CaCo-2), annexin V, LDH release, reactive oxygen species levels, total thiol content, HO-1, γ-glutamylcysteine synthetase, and p21 expression were evaluated. PCA induced, in a dose-dependent manner, a significantly reduced cell viability of CaCo-2 by oxidative/antioxidant imbalance. The phenolic acid induced modifications in levels of HO-1, non-proteic thiol groups, γ-glutamylcysteine synthetase, reactive oxygen species, and p21. PCA induced a pro-oxidant effect in cancer cells, and the in vitro pro-apoptotic effect on CaCo-2 cells is mediated by the modulation of redox balance and the inhibition of the HO-1 system that led to the activation of p21. Our results suggest that PCA may represent a useful tool in prevention and/or therapy of colon cancer.

Proteomics of colorectal cancer liver metastasis: A quantitative focus on drug elimination and pharmacodynamics effects

Aims

This study aims to quantify drug‐metabolising enzymes, transporters, receptor tyrosine kinases (RTKs) and protein markers (involved in pathways affected in cancer) in pooled healthy, histologically normal and matched cancerous liver microsomes from colorectal cancer liver metastasis (CRLM) patients.

Methods

Microsomal fractionation was performed and pooled microsomes were prepared. Global and accurate mass and retention time liquid chromatography–mass spectrometry proteomics were used to quantify proteins. A QconCAT (KinCAT) for the quantification of RTKs was designed and applied for the first time. Physiologically based pharmacokinetic (PBPK) simulations were performed to assess the contribution of altered abundance of drug‐metabolising enzymes and transporters to changes in pharmacokinetics.

Results

Most CYPs and UGTs were downregulated in histologically normal relative to healthy samples, and were further reduced in cancer samples (up to 54‐fold). The transporters, MRP2/3, OAT2/7 and OATP2B1/1B3/1B1 were downregulated in CRLM. Application of abundance data in PBPK models for substrates with different attributes indicated substantially lower (up to 13‐fold) drug clearance when using cancer‐specific instead of default parameters in cancer population. Liver function markers were downregulated, while inflammation proteins were upregulated (by up to 76‐fold) in cancer samples. Various pharmacodynamics markers (e.g. RTKs) were altered in CRLM. Using global proteomics, we examined proteins in pathways relevant to cancer (such as metastasis and desmoplasia), including caveolins and collagen chains, and confirmed general over‐expression of such pathways.

Conclusion

This study highlights impaired drug metabolism, perturbed drug transport and altered abundance of cancer markers in CRLM, demonstrating the importance of population‐specific abundance data in PBPK models for cancer.

Discovery of Novel Acetamide-Based Heme Oxygenase-1 Inhibitors with Potent In Vitro Antiproliferative Activity

Heme oxygenase-1 (HO-1) promotes heme catabolism exercising cytoprotective roles in normal and cancer cells. Herein, we report the design, synthesis, molecular modeling, and biological evaluation of novel HO-1 inhibitors. Specifically, an amide linker in the central spacer and an imidazole were fixed, and the hydrophobic moiety required by the pharmacophore was largely modified. In many tumors, overexpression of HO-1 correlates with poor prognosis and chemoresistance, suggesting the inhibition of HO-1 as a possible antitumor strategy. Accordingly, compounds 7i and 7l-p emerged for their potency against HO-1 and were investigated for their anticancer activity against prostate (DU145), lung (A549), and glioblastoma (U87MG, A172) cancer cells. The selected compounds showed the best activity toward U87MG cells. Compound 7l was further investigated for its in-cell enzymatic HO-1 activity, expression levels, and effects on cell invasion and vascular endothelial growth factor (VEGF) extracellular release. The obtained data suggest that 7l can reduce cell invasivity acting through modulation of HO-1 expression.

The Role of HO-1 and Its Crosstalk with Oxidative Stress in Cancer Cell Survival

Heme oxygenases (HOs) act on heme degradation to produce carbon monoxide (CO), free iron, ferritin, and biliverdin. Upregulation of cellular HO-1 levels is signature of oxidative stress for its downstream effects particularly under pro-oxidative status. Subcellular traffics of HO-1 to different organelles constitute a network of interactions compromising a variety of effectors such as pro-oxidants, ROS, mitochondrial enzymes, and nucleic transcription factors. Some of the compartmentalized HO-1 have been demonstrated as functioning in the progression of cancer. Emerging data show the multiple roles of HO-1 in tumorigenesis from pathogenesis to the progression to malignancy, metastasis, and even resistance to therapy. However, the role of HO-1 in tumorigenesis has not been systematically addressed. This review describes the crosstalk between HO-1 and oxidative stress, and following redox regulation in the tumorigenesis. HO-1-regulated signaling pathways are also summarized. This review aims to integrate basic information and current progress of HO-1 in cancer research in order to enhance the understandings and facilitate following studies.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Hemin-induced increase in saponin content contributes to the alleviation of osmotic and cold stress damage to Conyza blinii in a heme oxygenase 1-dependent manner

Hemin can improve the stress resistance of plants through the heme oxygenase system. Additionally, substances contained in plants, such as secondary metabolites, can improve stress resistance. However, few studies have explored the effects of hemin on secondary metabolite content. Therefore, the effects of hemin on saponin synthesis and the mechanism of plant injury relief by hemin in Conyza blinii were investigated in this study. Hemin treatment promoted plant growth and increased the antioxidant enzyme activity and saponin content of C. blinii under osmotic stress and cold stress. Further study showed that hemin could provide sufficient precursors for saponin synthesis by improving the photosynthetic capacity of C. blinii and increasing the gene expression of key enzymes in the saponin synthesis pathway, thus increasing the saponin content. Moreover, the promotion effect of hemin on saponin synthesis is dependent on heme oxygenase-1 and can be reversed by the inhibitor Zn-protoporphyrin-IX (ZnPPIX). This study revealed that hemin can increase the saponin content of C. blinii and alleviate the damage caused by abiotic stress, and it also broadened the understanding of the relationship between hemin and secondary metabolites in plant abiotic stress relief.

Proteomic Analysis of the Non-genetic Response to Cisplatin in Lung Cancer Cells

BACKGROUND

Drug resistance is the main cause of therapy failure in advanced lung cancer. Although non-genetic mechanisms play important roles in tumor chemoresistance, drug-induced epigenetic reprogramming is still poorly understood.

MATERIALS AND METHODS

The A549 cell line was used to generate cells with non-genetic resistance to cisplatin (CDDP), namely A549/CDDP cells. Bioorthogonal non-canonical amino acid tagging (BONCAT) and mass spectrometry were used to identify proteins modulated by CDDP in A549 and A549/CDDP cells.

RESULTS

Proteins related to proteostasis, telomere maintenance, cell adhesion, cytoskeletal remodeling, and cell redox homeostasis were found enriched in both cell lines upon CDDP exposure. On the other hand, proteins involved in drug response, metabolic pathways and mRNA processing and splicing were up-regulated by CDDP only in A549/CDDP cells.

CONCLUSION

Our study revealed proteome dynamics involved in the non-genetic response to CDDP, pointing out potential targets to monitor and overcome epigenetic resistance in lung cancer.

Novel mutual prodrug of 5-fluorouracil and heme oxygenase-1 inhibitor (5-FU/HO-1 hybrid): design and preliminary in vitro evaluation

In this work, the first mutual prodrug of 5-fluorouracil and heme oxygenase1 inhibitor (5-FU/HO-1 hybrid) has been designed, synthesised, and evaluated for its in vitro chemical and enzymatic hydrolysis stability. Predicted in silico physicochemical properties of the newly synthesised hybrid (3) demonstrated a drug-like profile with suitable Absorption, Distribution, Metabolism, and Excretion (ADME) properties and low toxic liabilities. Preliminary cytotoxicity evaluation towards human prostate (DU145) and lung (A549) cancer cell lines demonstrated that 3 exerted a similar effect on cell viability to that produced by the reference drug 5-FU. Among the two tested cancer cell lines, the A549 cells were more susceptible for 3. Of note, hybrid 3 also had a significantly lower cytotoxic effect on healthy human lung epithelial cells (BEAS-2B) than 5-FU. Altogether our results served as an initial proof-of-concept to develop 5-FU/HO-1 mutual prodrugs as potential novel anticancer agents.

Tin Mesoporphyrin Selectively Reduces Non-Small-Cell Lung Cancer Cell Line A549 Proliferation by Interfering with Heme Oxygenase and Glutathione Systems

In order to maintain redox homeostasis, non-small-cell lung cancer (NSCLC) increases the activation of many antioxidant systems, including the heme-oxygenase (HO) system. The overexpression of HO-1 has been often associated with chemoresistance and tumor aggressiveness. Our results clearly showed an overexpression of the HO-1 protein in A549 NSCLC cell lines compared to that in non-cancerous cells. Thus, we hypothesized that "off-label" use of tin mesoporphyrin, a well-known HO activity inhibitor clinically used for neonatal hyperbilirubinemia, has potential use as an anti-cancer agent. The pharmacological inhibition of HO activity caused a reduction in cell proliferation and migration of A549. SnMP treatment caused an increase in oxidative stress, as demonstrated by the upregulation of reactive oxygen species (ROS) and the depletion of glutathione (GSH) content. To support these data, Western blot analysis was performed to analyze glucose-6-phosphate dehydrogenase (G6PD), TP53-induced glycolysis and the apoptosis regulator (TIGAR), and the glutamate cysteine ligase catalytic (GCLC) subunit, as they represent the main regulators of the pentose phosphate pathway (PPP) and glutathione synthesis, respectively. NCI-H292, a subtype of the NSCLC cell line, did not respond to SnMP treatment, possibly due to low basal levels of HO-1, suggesting a cellular-dependent antitumorigenic effect. Altogether, our results suggest HO activity inhibition may represent a potential target for selective chemotherapy in lung cancer subtypes.

Clinical Significance of Heme Oxygenase 1 in Tumor Progression

Heme oxygenase 1 (HO-1) plays a key role in cell adaptation to stressors through the antioxidant, antiapoptotic, and anti-inflammatory properties of its metabolic products. For these reasons, in cancer cells, HO-1 can favor aggressiveness and resistance to therapies, leading to poor prognosis/outcome. Genetic polymorphisms of HO-1 promoter have been associated with an increased risk of cancer progression and a high degree of therapy failure. Moreover, evidence from cancer biopsies highlights the possible correlation between HO-1 expression, pathological features, and clinical outcome. Indeed, high levels of HO-1 in tumor specimens often correlate with reduced survival rates. Furthermore, HO-1 modulation has been proposed in order to improve the efficacy of antitumor therapies. However, contrasting evidence on the role of HO-1 in tumor biology has been reported. This review focuses on the role of HO-1 as a promising biomarker of cancer progression; understanding the correlation between HO-1 and clinical data might guide the therapeutic choice and improve the outcome of patients in terms of prognosis and life quality.

A Coumarin-Porphyrin FRET Break-Apart Probe for Heme Oxygenase-1

Heme oxygenase-1 (HO-1) is a vital enzyme in humans that primarily regulates free heme concentrations. The overexpression of HO-1 is commonly associated with cardiovascular and neurodegenerative diseases including atherosclerosis and ischemic stroke. Currently, there are no known chemical probes to detect HO-1 activity, limiting its potential as an early diagnostic/prognostic marker in these serious diseases. Reported here are the design, synthesis, and photophysical and biological characterization of a coumarin-porphyrin FRET break-apart probe to detect HO-1 activity, Fe-L1. We designed Fe-L1 to "break-apart" upon HO-1-catalyzed porphyrin degradation, perturbing the efficient FRET mechanism from a coumarin donor to a porphyrin acceptor fluorophore. Analysis of HO-1 activity using Escherichia coli lysates overexpressing hHO-1 found that a 6-fold increase in emission intensity at 383 nm was observed following incubation with NADPH. The identities of the degradation products following catabolism were confirmed by MALDI-MS and LC-MS, showing that porphyrin catabolism was regioselective at the α-position. Finally, through the analysis of Fe-L2, we have shown that close structural analogues of heme are required to maintain HO-1 activity. It is anticipated that this work will act as a foundation to design and develop new probes for HO-1 activity in the future, moving toward applications of live fluorescent imaging.

Heme Oxygenase-1 Signaling and Redox Homeostasis in Physiopathological Conditions

Heme-oxygenase is the enzyme responsible for degradation of endogenous iron protoporphyirin heme; it catalyzes the reaction’s rate-limiting step, resulting in the release of carbon monoxide (CO), ferrous ions, and biliverdin (BV), which is successively reduced in bilirubin (BR) by biliverdin reductase. Several studies have drawn attention to the controversial role of HO-1, the enzyme inducible isoform, pointing out its implications in cancer and other diseases development, but also underlining the importance of its antioxidant activity. The contribution of HO-1 in redox homeostasis leads to a relevant decrease in cells oxidative damage, which can be reconducted to its cytoprotective effects explicated alongside other endogenous mechanisms involving genes like TIGAR (TP53-induced glycolysis and apoptosis regulator), but also to the therapeutic functions of heme main transformation products, especially carbon monoxide (CO), which has been shown to be effective on GSH levels implementation sustaining body’s antioxidant response to oxidative stress. The aim of this review was to collect most of the knowledge on HO-1 from literature, analyzing different perspectives to try and put forward a hypothesis on revealing yet unknown HO-1-involved pathways that could be useful to promote development of new therapeutical strategies, and lay the foundation for further investigation to fully understand this important antioxidant system.

SIO: A Spatioimageomics Pipeline to Identify Prognostic Biomarkers Associated with the Ovarian Tumor Microenvironment

Stromal and immune cells in the tumor microenvironment (TME) have been shown to directly affect high-grade serous ovarian cancer (HGSC) malignant phenotypes, however, how these cells interact to influence HGSC patients' survival remains largely unknown. To investigate the cell-cell communication in such a complex TME, we developed a SpatioImageOmics (SIO) pipeline that combines imaging mass cytometry (IMC), location-specific transcriptomics, and deep learning to identify the distribution of various stromal, tumor and immune cells as well as their spatial relationship in TME. The SIO pipeline automatically and accurately segments cells and extracts salient cellular features to identify biomarkers, and multiple nearest-neighbor interactions among tumor, immune, and stromal cells that coordinate to influence overall survival rates in HGSC patients. In addition, SIO integrates IMC data with microdissected tumor and stromal transcriptomes from the same patients to identify novel signaling networks, which would lead to the discovery of novel survival rate-modulating mechanisms in HGSC patients.

High expression of heme oxygenase-1 in tumor-associated macrophages characterizes a poor-prognosis subtype in nasopharyngeal carcinoma

Tumor-associated macrophages (TAMs) are important components of the tumor microenvironment, which are characterized by pro-tumor M2 phenotype and correlate with poor survival of nasopharyngeal carcinoma (NPC). Heme oxygenase-1 (HO-1) plays a crucial role in macrophage polarization toward M2 phenotype, but its prognosis significance in NPC has been rarely determined. To gain insights into the HO-1 expression profile and to determine the clinical significance of HO-1 in NPC, we performed immunohistochemistry analyses in 126 NPC specimens. CD163, a highly specific marker of M2 macrophages, was used as a surrogate for the polarization state of TAMs. Our results showed that high expression of HO-1 and CD163 were detected in TAMs for 57.9% (73/126) and 61.9% (78/126) of the studied patients, and both of them were significantly associated with worse survival. Additionally, a significant correlation between the intensities of HO-1 and CD163 was identified, and HO-1 exhibited a superior ability in predicting survival compared with CD163. Our study revealed for the first time that overexpression of HO-1 characterized a poor-prognosis subtype in NPC. Individualized therapy targeting HO-1 might serve as a promising treatment modality for NPC.

Immune Modulation by Inhibitors of the HO System

The heme oxygenase (HO) system involves three isoforms of this enzyme, HO-1, HO-2, and HO-3. The three of them display the same catalytic activity, oxidating the heme group to produce biliverdin, ferrous iron, and carbon monoxide (CO). HO-1 is the isoform most widely studied in proinflammatory diseases because treatments that overexpress this enzyme promote the generation of anti-inflammatory products. However, neonatal jaundice (hyperbilirubinemia) derived from HO overexpression led to the development of inhibitors, such as those based on metaloproto- and meso-porphyrins inhibitors with competitive activity. Further, non-competitive inhibitors have also been identified, such as synthetic and natural imidazole-dioxolane-based, small synthetic molecules, inhibitors of the enzyme regulation pathway, and genetic engineering using iRNA or CRISPR cas9. Despite most of the applications of the HO inhibitors being related to metabolic diseases, the beneficial effects of these molecules in immune-mediated diseases have also emerged. Different medical implications, including cancer, Alzheimer´s disease, and infections, are discussed in this article and as to how the selective inhibition of HO isoforms may contribute to the treatment of these ailments.

Novel Heme Oxygenase-1 (HO-1) Inducers Based on Dimethyl Fumarate Structure

Novel heme oxygenase-1 (HO-1) inducers based on dimethyl fumarate (DMF) structure are reported in this paper. These compounds are obtained by modification of the DMF backbone. Particularly, maintaining the α, β-unsaturated dicarbonyl function as the central chain crucial for HO-1 induction, different substituted or unsubstituted phenyl rings are introduced by means of an ester or amide linkage. Symmetric and asymmetric derivatives are synthesized. All compounds are tested on a human hepatic stellate cell line LX-2 to assay their capacity for modifying HO-1 expression. Compounds 1b, 1l and 1m stand out for their potency as HO-1 inducers, being 2–3 fold more active than DMF, and for their ability to reverse reactive oxygen species (ROS) production mediated using palmitic acid (PA). These properties, coupled with a low toxicity toward LX-2 cell lines, make these compounds potentially useful for treatment of diseases in which HO-1 overexpression may counteract inflammation, such as hepatic fibrosis. Docking studies show a correlation between predicted binding free energy and experimental HO-1 expression data. These preliminary results may support the development of new approaches in the management of liver fibrosis.

Therapeutic Potential of Heme Oxygenase-1 and Carbon Monoxide in Acute Organ Injury, Critical Illness, and Inflammatory Disorders

Heme oxygenase-1 (HO-1) is an inducible stress protein that catalyzes the oxidative conversion of heme to carbon monoxide (CO), iron, and biliverdin (BV), the latter of which is converted to bilirubin (BR) by biliverdin reductase. HO-1 has been implicated as a cytoprotectant in various models of acute organ injury and disease (i.e., lung, kidney, heart, liver). Thus, HO-1 may serve as a general therapeutic target in inflammatory diseases. HO-1 may function as a pleiotropic modulator of inflammatory signaling, via the removal of heme, and generation of its enzymatic degradation-products. Iron release from HO activity may exert pro-inflammatory effects unless sequestered, whereas BV/BR have well-established antioxidant properties. CO, derived from HO activity, has been identified as an endogenous mediator that can influence mitochondrial function and/or cellular signal transduction programs which culminate in the regulation of apoptosis, cellular proliferation, and inflammation. Much research has focused on the application of low concentration CO, whether administered in gaseous form by inhalation, or via the use of CO-releasing molecules (CORMs), for therapeutic benefit in disease. The development of novel CORMs for their translational potential remains an active area of investigation. Evidence has accumulated for therapeutic effects of both CO and CORMs in diseases associated with critical care, including acute lung injury/acute respiratory distress syndrome (ALI/ARDS), mechanical ventilation-induced lung injury, pneumonias, and sepsis. The therapeutic benefits of CO may extend to other diseases involving aberrant inflammatory processes such as transplant-associated ischemia/reperfusion injury and chronic graft rejection, and metabolic diseases. Current and planned clinical trials explore the therapeutic benefit of CO in ARDS and other lung diseases.

Cigarette smoke preparations, not electronic nicotine delivery system preparations, induce features of lung disease in a 3D lung repeat-dose model

Cigarette smoking is a risk factor for several lung diseases, including chronic obstructive pulmonary disease, cardiovascular disease, and lung cancer. The potential health effects of chronic use of electronic nicotine delivery systems (ENDS) is unclear. This study utilized fully differentiated primary normal human bronchial epithelial (NHBE) cultures in a repeat-dose exposure to evaluate and compare the effect of combustible cigarette and ENDS preparations. We show that 1-h daily exposure of NHBE cultures over a 10-day period to combustible cigarette whole smoke-conditioned media (WS-CM) increased expression of oxidative stress markers, cell proliferation, airway remodeling, and cellular transformation markers and decreased mucociliary function including ion channel function and airway surface liquid. Conversely, aerosol conditioned media (ACM) from ENDS with similar nicotine concentration (equivalent-nicotine units) as WS-CM and nicotine alone had no effect on those parameters. In conclusion, primary NHBE cultures in a repeat-dose exposure system represent a good model to assess the features of lung disease. This study also reveals that cigarette and ENDS preparations differentially elicit several key endpoints, some of which are potential biomarkers for lung cancer or chronic obstructive pulmonary disease (COPD).

Simultaneous Detection of Carbon Monoxide and Viscosity Changes in Cells

A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.

Blood-Brain Barrier, Blood-Brain Tumor Barrier, and Fluorescence-Guided Neurosurgical Oncology: Delivering Optical Labels to Brain Tumors

Recent advances in maximum safe glioma resection have included the introduction of a host of visualization techniques to complement intraoperative white-light imaging of tumors. However, barriers to the effective use of these techniques within the central nervous system remain. In the healthy brain, the blood-brain barrier ensures the stability of the sensitive internal environment of the brain by protecting the active functions of the central nervous system and preventing the invasion of microorganisms and toxins. Brain tumors, however, often cause degradation and dysfunction of this barrier, resulting in a heterogeneous increase in vascular permeability throughout the tumor mass and outside it. Thus, the characteristics of both the blood-brain and blood-brain tumor barriers hinder the vascular delivery of a variety of therapeutic substances to brain tumors. Recent developments in fluorescent visualization of brain tumors offer improvements in the extent of maximal safe resection, but many of these fluorescent agents must reach the tumor via the vasculature. As a result, these fluorescence-guided resection techniques are often limited by the extent of vascular permeability in tumor regions and by the failure to stain the full volume of tumor tissue. In this review, we describe the structure and function of both the blood-brain and blood-brain tumor barriers in the context of the current state of fluorescence-guided imaging of brain tumors. We discuss features of currently used techniques for fluorescence-guided brain tumor resection, with an emphasis on their interactions with the blood-brain and blood-tumor barriers. Finally, we discuss a selection of novel preclinical techniques that have the potential to enhance the delivery of therapeutics to brain tumors in spite of the barrier properties of the brain.

Heme Oxygenase-1 in Central Nervous System Malignancies

Central nervous system tumors are the most common pediatric solid tumors and account for 20–25% of all childhood malignancies. Several lines of evidence suggest that brain tumors show altered redox homeostasis that triggers the activation of various survival pathways, leading to disease progression and chemoresistance. Among these pathways, heme oxygenase-1 (HO-1) plays an important role. HO-1 catalyzes the enzymatic degradation of heme with the simultaneous release of carbon monoxide (CO), ferrous iron (Fe²⁺), and biliverdin. The biological effects of HO-1 in tumor cells have been shown to be cell-specific since, in some tumors, its upregulation promotes cell cycle arrest and cellular death, whereas, in other neoplasms, it is associated with tumor survival and progression. This review focuses on the role of HO-1 in central nervous system malignancies and the possibility of exploiting such a target to improve the outcome of well-established therapeutic regimens. Finally, several studies show that HO-1 overexpression is involved in the development and resistance of brain tumors to chemotherapy and radiotherapy, suggesting the use of HO-1 as an innovative therapeutic target to overcome drug resistance. The following keywords were used to search the literature related to this topic: nuclear factor erythroid 2 p45-related factor 2, heme oxygenase, neuroblastoma, medulloblastoma, meningioma, astrocytoma, oligodendroglioma, glioblastoma multiforme, and gliomas.

Regulation of the Expression of Heme Oxygenase-1: Signal Transduction, Gene Promoter Activation, and Beyond

Significance: Heme oxygenase-1 (HO-1) is a ubiquitous 32-kDa protein expressed in many tissues and highly inducible. They catalyze the degradation of the heme group and the release of free iron, carbon monoxide, and biliverdin; the latter converted to bilirubin by biliverdin reductase. Its role in the regulation of cellular homeostasis is widely documented. Studying regulation of HO-1 expression is important not only to understand the life of healthy cells but also the unbalances in cell metabolism that lead to disease. Recent Advances: The regulation of its enzymatic activity depends heavily upon changes in expression studied mainly at the transcriptional level. Current knowledge regarding HO-1 gene expression focuses primarily on transcription factors such as Nrf2 (nuclear factor erythroid 2-related factor 2), AP-1 (activator protein-1), and hypoxia-inducible factor, which collect signal transduction pathway information at the HO-1 gene promoter. Understanding of gene expression regulation is not limited to transcription factor activity but also involves an extended range of post- or cotranscriptional regulated events. Critical Issues: In addition to the regulation of gene promoter activity, alternative splicing, alternative polyadenylation, and regulation of messenger RNA stability play critical roles in changes in HO-1 gene expression levels, involving specific factors, proteins, and microRNAs. All potential targets for diagnosis or treatment of diseases are related to HO-1 dysregulation. Future Directions: Unbalances in the tightly regulated gene expression mechanisms lead to cell transformation and cancer development. Knowledge of these events and signal transduction cascades triggered by oncogenes in which HO-1 plays a critical role is of upmost importance for research in this field.

Dual Targeting of the p38 MAPK-HO-1 Axis and cIAP1/XIAP by Demethoxycurcumin Triggers Caspase-Mediated Apoptotic Cell Death in Oral Squamous Cell Carcinoma Cells

Demethoxycurcumin (DMC) is a curcumin analogue with better stability and higher aqueous solubility than curcumin after oral ingestion and has the potential to treat diverse cancers, including oral squamous cell carcinoma (OSCC). The aim of this study was to investigate the anticancer effects and underlying mechanisms of DMC against OSCC. We found that DMC suppressed cell proliferation via simultaneously inducing G2/M-phase arrest and cell apoptosis. Mechanistic investigations found that the downregulation of cellular IAP 1 (cIAP1)/X-chromosome-linked IAP (XIAP) and upregulation of heme oxygenase-1 (HO-1) were critical for DMC-induced caspase-8/-9/-3 activation and apoptotic cell death. Moreover, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK)1/2 were activated by DMC treatment in OSCC cells, and only the inhibition of p38 MAPK significantly abolished DMC-induced HO-1 expression and caspase-8/-9/-3 activation. The analyses of clinical datasets revealed that patients with head and neck cancers expressing high HO-1 and low cIAP1 had the most favorable prognoses. Furthermore, a combinatorial treatment of DMC with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib, significantly enhanced the inhibitory effect of gefitinib on the proliferation of OSCC cells. Overall, the current study supported a role for DCM as part of a therapeutic approach for OSCC through suppressing IAPs and activating the p38-HO-1 axis.

New Arylethanolimidazole Derivatives as HO-1 Inhibitors with Cytotoxicity against MCF-7 Breast Cancer Cells

In this paper, a novel series of imidazole-based heme oxygenase-1 (HO-1) inhibitors is reported. These compounds were obtained by modifications of previously described high potent and selective arylethanolimidazoles. In particular, simplification of the central linker and repositioning of the hydrophobic portion were carried out. Results indicate that a hydroxyl group in the central region is crucial for the potency as well as the spatial distribution of the hydrophobic portion. Docking studies revealed a similar interaction of the classical HO-1 inhibitors with the active site of the protein. The most potent and selective compound (5a) was tested for its potential cytotoxic activity against hormone-sensitive and hormone-resistant breast cancer cell lines (MCF-7 and MDA-MB-231).

Hydrogen sulfide renal protective effects: possible link between hydrogen sulfide and endogenous carbon monoxide in a rat model of renal injury

Hydrogen sulfide (H2S), along with nitric oxide (NO) and carbon monoxide (CO), proved to have renoprotective effects in various renal diseases. Therefore, this study investigated the renoprotective effect of H2S, in a renal injury model, and its crosstalk with other gasotransmitters such as CO. Thirty-two adult rats were divided into four groups: control, gentamicin (GEN)-treated, GEN + sodium hydrosulfide (NaHS), and GEN + NaHS + zinc protoporphyrin (ZnPP) groups. GEN was used to induce renal injury, NaHS is a water-soluble H2S, and ZnPP is a selective heme oxygenase-1 (HO-1) inhibitor used to inhibit CO synthesis in vivo. NaHS improved kidney functions in the GEN group as evidenced by significantly lower levels of renal injury markers: serum urea, creatinine, uric acid, urinary albumin excretion, and urinary albumin/creatinine. Moreover, NaHS administration to the GEN-treated group significantly lowered renal levels of NO and tumor necrosis factor-α with an increase in total antioxidant, HO-1, and interleukin-10 levels. Furthermore, NaHS administration downregulated the GEN-induced overexpression of the renal inducible nitric oxide synthase (iNOS) and upregulated the suppression of endothelial nitric oxide synthase (eNOS) with improvement in the histological examination and periodic acid Schiff (PAS) staining. However, this improvement in kidney function produced by NaHS was reduced by combination with ZnPP but still improved as compared with the GEN-treated group. The renoprotective effects of H2S can be through its effects on renal tissue antioxidants, pro-inflammatory and anti-inflammatory cytokines, and expression of eNOS and iNOS which can be partially dependent on CO pathway via induction of HO-1 enzyme.

Non-competitive heme oxygenase-1 activity inhibitor reduces non-small cell lung cancer glutathione content and regulates cell proliferation

Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related death mainly due to its high metastatic rate. Impairment of redox homeostasis mechanisms has been previously described in NSCLC and is associated with the disease itself as well as with comorbidities such as smoking. The aim of the present in vitro study was to evaluate the effect of selective and non-competitive inhibition of heme oxygenase-1 (HO-1) on cancer redox homeostasis with particular regards to glutathione (GSH) metabolism related enzymes. NSCLC cell line (A549) was treated with the HO-1 activity inhibitor VP13/47 (10 µM) and we further evaluated cell viability, apoptosis, mitochondrial dysfunction and oxidative stress. Our results showed that VP13/47 significantly reduced HO-1 expression and total HO activity thus, resulting in a significant reduction of cell viability, proliferation and increased apoptosis, mitochondrial dysfunction and oxidative stress. Consistently with increased oxidative stress, we also showed that reduced GSH was significantly decreased and such effect was also accompanied by a significant downregulation of the enzymes involved in its biosynthesis. Taken all together our results show that selective HO-1 inhibition significantly impairs NSCLC progression and may represent a possible pharmacological strategy for new chemotherapy agents.

Synthetically Lethal Interactions of Heme Oxygenase-1 and Fumarate Hydratase Genes

Elevated expression of heme oxygenase-1 (HO-1, encoded by HMOX1) is observed in various types of tumors. Hence, it is suggested that HO-1 may serve as a potential target in anticancer therapies. A novel approach to inhibit HO-1 is related to the synthetic lethality of this enzyme and fumarate hydratase (FH). In the current study, we aimed to validate the effect of genetic and pharmacological inhibition of HO-1 in cells isolated from patients suffering from hereditary leiomyomatosis and renal cell carcinoma (HLRCC)-an inherited cancer syndrome, caused by FH deficiency. Initially, we confirmed that UOK 262, UOK 268, and NCCFH1 cell lines are characterized by non-active FH enzyme, high expression of Nrf2 transcription factor-regulated genes, including HMOX1 and attenuated oxidative phosphorylation. Later, we demonstrated that shRNA-mediated genetic inhibition of HMOX1 resulted in diminished viability and proliferation of cancer cells. Chemical inhibition of HO activity using commercially available inhibitors, zinc and tin metalloporphyrins as well as recently described new imidazole-based compounds, especially SLV-11199, led to decreased cancer cell viability and clonogenic potential. In conclusion, the current study points out the possible relevance of HO-1 inhibition as a potential anti-cancer treatment in HLRCC. However, further studies revealing the molecular mechanisms are still needed.

Antioxidation and Antiapoptosis Characteristics of Heme Oxygenase-1 Enhance Tumorigenesis of Human Prostate Carcinoma Cells

Heme oxygenase-1 (HO-1) has antiinflammatory and antioxidant properties and is deemed as a tissue protector. However, effects of HO-1 in prostate cancer remain in controversy. We evaluated the role of HO-1 in prostate carcinoma in vitro and in vivo.

Overexpression of HO-1 did not affect prostate cell proliferation in the normal condition but enhanced cell proliferation under serum starvation. HO-1 overexpression enhanced cell invasion of PC-3 cells through epithelial–mesenchymal transition (EMT) induction, which was supported by increased Slug, N-cadherin, and vimentin expressions. In the xenograft animal study, HO-1 overexpression enhanced PC-3 cell tumor growth in vivo. HO-1 attenuated reactive oxygen species induced by H₂O₂ or pyocyanin treatment in PC-3 and DU145 cells. HO-1 further reduced PC-3 and DU145 cell apoptosis induced by H₂O₂ or serum starvation. Our results suggested that HO-1 was able to increase prostate carcinoma cell invasion in vitro and tumor growth in vivo. The EMT induction and antioxidant and antiapoptotic effects of HO-1 in the prostate carcinoma cells may be responsible for these findings.

5-ALA/SFC enhances HO-1 expression through the MAPK/Nrf2 antioxidant pathway and attenuates murine tubular epithelial cell apoptosis

Cyclosporin A (CsA) is a common immunosuppressant, but its use is limited as it can cause chronic kidney injury. Oxidative stress and apoptosis play a key role in CsA-induced nephrotoxicity. This study investigated the protective effect of 5-aminolevulinic acid and iron (5-ALA/SFC) on CsA-induced injury in murine proximal tubular epithelial cells (mProx24). 5-ALA/SFC significantly inhibited apoptosis in CsA-treated mProx24 cells with increases in heme oxygenase (HO)-1, nuclear factor E2-related factor 2 (Nrf2), and p38, and Erk-1/2 phosphorylation. Moreover, 5-ALA/SFC suppressed production of reactive oxygen species in CsA-exposed cells and inhibition of HO-1 suppressed the protective effects of 5-ALA/SFC. In summary, 5-ALA/SFC may have potential for development into a treatment for the anti-nephrotoxic/apoptotic effects of CsA.

Role of Heme Oxygenase as a Modulator of Heme-Mediated Pathways

The heme oxygenase (HO) system is essential for heme and iron homeostasis and necessary for adaptation to cell stress. HO degrades heme to biliverdin (BV), carbon monoxide (CO) and ferrous iron. Although mostly beneficial, the HO reaction can also produce deleterious effects, predominantly attributed to excessive product formation. Underrated so far is, however, that HO may exert effects additionally via modulation of the cellular heme levels. Heme, besides being an often-quoted generator of oxidative stress, plays also an important role as a signaling molecule. Heme controls the anti-oxidative defense, circadian rhythms, activity of ion channels, glucose utilization, erythropoiesis, and macrophage function. This broad spectrum of effects depends on its interaction with proteins ranging from transcription factors to enzymes. In degrading heme, HO has the potential to exert effects also via modulation of heme-mediated pathways. In this review, we will discuss the multitude of pathways regulated by heme to enlarge the view on HO and its role in cell physiology. We will further highlight the contribution of HO to pathophysiology, which results from a dysregulated balance between heme and the degradation products formed by HO.

Curcumin-Gene Expression Response in Hormone Dependent and Independent Metastatic Prostate Cancer Cells

The androgen receptor is one of the key targets for prostate cancer treatment. Despite its less satisfactory effects, chemotherapy is the most common treatment option for metastatic and/or castration-resistant patients. There are constant needs for novel anti-prostate cancer therapeutic/prevention agents. Curcumin, a known chemo-preventive agent, was shown to inhibit prostate cancer cell growth. This study aimed to unravel the inhibitory effect of curcumin in prostate cancer through analyzing the alterations of expressions of curcumin targeting genes clusters in androgen-dependent LNCaP cells and androgen-independent metastatic C4-2B cells. Hierarchical clustering showed the highest number of differentially expressed genes at 12 h post treatment in both cells, suggesting that the androgen-dependent/independent manner of curcumin impacts on prostate cancer cells. Evaluation of significantly regulated top canonical pathways highlighted that Transforming growth factor beta (TGF-β), Wingless-related integration site (Wnt), Phosphoinositide 3-kinase/Protein Kinase B/ mammalian target of rapamycin (PIK3/AKT(PKB)/mTOR), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) signaling were primarily inhibited, and Phosphatase and tensin homolog (PTEN) dependent cell cycle arrest and apoptosis pathways were elevated with curcumin treatment. The short term (3–24 h) and long term (48 h) effect of curcumin treatment revealed 31 and four genes modulated in both cell lines. TGF-β signaling, including the androgen/TGF-β inhibitor Prostate transmembrane protein androgen-induced 1 (PMEPA1), was the only pathway impacted by curcumin treatment after 48 h. Our findings also established that MYC Proto-Oncogene, basic helix-loop-helix (bHLH) Transcription Factor (MYC) signaling was down-regulated in curcumin-treated cell lines. This study established, for the first time, novel gene-networks and signaling pathways confirming the chemo-preventive and cancer-growth inhibitory nature of curcumin as a natural anti-prostate cancer compound.

JNK inhibition blocks piperlongumine-induced cell death and transcriptional activation of heme oxygenase-1 in pancreatic cancer cells

Piperlongumine (PL) is an alkaloid that inhibits glutathione S-transferase pi 1 (GSTP1) activity, resulting in elevated reactive oxygen species (ROS) levels and cancer-selective cell death. We aimed to identify stress-associated molecular responses to PL treatment in pancreatic ductal adenocarcinoma (PDAC) cells. GSTP1 directly interacts with JNK, which is activated by oxidative stress and can lead to decreased cancer cell proliferation and cell death. Therefore, we hypothesized that JNK pathways are activated in response to PL treatment. Our results show PL causes dissociation of GSTP1 from JNK; robust JNK, c-Jun, and early ERK activation followed by suppression; increased expression of cleaved caspase-3 and cleaved PARP; and nuclear translocation of Nrf2 and c-Myc in PDAC cells. Gene expression analysis revealed PL caused a > 20-fold induction of heme oxygenase-1 (HO-1), which we hypothesized was a survival mechanism for PDAC cells under enhanced oxidative stress. HO-1 knockout resulted in enhanced PL-induced PDAC cell death under hypoxic conditions. Similarly, high concentrations of the HO-1 inhibitor, ZnPP (10 µM), sensitized PDAC cells to PL; however, lower concentrations ZnPP (10 nM) and high or low concentrations of SnPP both protected PDAC cells from PL-induced cell death. Interestingly, the JNK inhibitor significantly blocked PL-induced PDAC cell death, Nrf-2 nuclear translocation, and HMOX-1 mRNA expression. Collectively, the results demonstrate JNK signaling contributes to PL-induced PDAC cell death, and at the same time, activates Nrf-2 transcription of HMOX-1 as a compensatory survival mechanism. These results suggest that elevating oxidative stress (using PL) while at the same time impairing antioxidant capacity (inhibiting HO-1) may be an effective therapeutic approach for PDAC.

HTLV-1 basic leucine zipper factor protects cells from oxidative stress by upregulating expression of Heme Oxygenase I

Adult T-cell Leukemia (ATL) is a lymphoproliferative disease of CD4+ T-cells infected with Human T-cell Leukemia Virus type I (HTLV-1). With the exception of allogeneic hematopoietic stem cell transplantation, there are no effective treatments to cure ATL, and ATL cells often acquire resistance to conventional chemotherapeutic agents. Accumulating evidence shows that development and maintenance of ATL requires key contributions from the viral protein, HTLV-1 basic leucine zipper factor (HBZ). In this study we found that HBZ activates expression of Heme Oxygenase 1 (HMOX-1), a component of the oxidative stress response that functions to detoxify free heme. Transcription of HMOX1 and other antioxidant genes is regulated by the small Mafs. These cellular basic leucine zipper (bZIP) factors control transcription by forming homo- or heterodimers among themselves or with other cellular bZIP factors that then bind Maf responsive elements (MAREs) in promoters or enhancers of antioxidant genes. Our data support a model in which HBZ activates HMOX1 transcription by forming heterodimers with the small Mafs that bind MAREs located in an upstream enhancer region. Consistent with this model, we found that HMOX-1 is upregulated in HTLV-1-transformed T-cell lines and confers these cells with resistance to heme-induced cytotoxicity. In this context, HBZ-mediated activation of HMOX-1 expression may contribute to resistance of ATL cells to certain chemotherapeutic agents. We also provide evidence that HBZ counteracts oxidative stress caused by two other HTLV-1-encoded proteins, Tax and p13. Tax induces oxidative stress as a byproduct of driving mitotic expansion of infected cells, and p13 is believed to induce oxidative stress to eliminate infected cells that have become transformed. Therefore, in this context, HBZ-mediated activation of HMOX-1 expression may facilitate transformation. Overall, this study characterizes a novel function of HBZ that may support the development and maintenance of ATL.

Pharmacology of ME-344, a novel cytotoxic isoflavone

Isoflavones isolated from members of the Fabaceae (primarily Leguminosae) family have been characterized for their phytoestrogenic properties, but certain derivatives have also shown potential as possible cancer therapeutic agents. ME-344, related to phenoxodiol (Fig. 1), is a second generation isoflavone with a recent history of both preclinical and early clinical testing. The drug has unusual cytotoxicity profiles, where cancer cell lines can be categorized as either intrinsically sensitive or resistant to the drug. Evolving studies show that the cytotoxic properties of the drug are enacted through targeting mitochondrial bioenergetics. While the drug has undergone early Phase I/II trials in solid tumors with confined dose limiting effects and some evidence of disease response, there is a continuing need to define specific cellular targets that determine sensitivity, with the long-term goal of applying such information to individualized therapy. This review article details some of the existing and ongoing studies that are assisting in the continued drug development processes that may lead to new drug application (NDA) status.

Extracts from Sageretia thea reduce cell viability through inducing cyclin D1 proteasomal degradation and HO-1 expression in human colorectal cancer cells

Background

Sageretia thea (S. thea) has been used as the medicinal plant for treating hepatitis and fevers in Korea and China. Recently, anticancer activity of S. thea has been reported, but the potential mechanism for the anti-cancer property of S. thea is still insufficient. Thus, we evaluated whether extracts from the leaves (STL) and branches (STB) of S. thea exert anticancer activity and elucidated its potential mechanism in SW480 cells.

Methods

MTT assay was performed for measuring cell viability. Western blot and RT-PCR were used for analyzing the level of protein and mRNA, respectively.

Results

Treatment of STL or STB decreased the cell viability and induced apoptosis in SW480 cells. Decreased level of cyclin D1 protein was observed in SW480 cells treated with STL or STB, but no change in cyclin D1 mRNA level was observed with the treatment of STL or STB. MG132 blocked downregulation of cyclin D1 protein by STL or STB. Thr286 phosphorylation of cyclin D1 by STL or STB occurred faster than downregulation of cyclin D1 protein in SW480 cells. When SW480 cells were transfected with T286A-cyclin D1, cyclin D1 degradation by STL or STB did not occur. Inhibition of GSK3β and cyclin D1 nuclear export attenuated STL or STB-mediated cyclin D1 degradation. In addition, STL or STB increased HO-1 expression, and the inhibition of HO-1 attenuated the induction of apoptosis by STL or STB. HO-1 expression by STL or STB resulted from Nrf2 activation through ROS-dependent p38 activation.

Conclusions

These results indicate that STL or STB may induce GSK3β-dependent cyclin D1 degradation, and increase HO-1 expression through activating Nrf2 via ROS-dependent p38 activation, which resulted in the decrease of the viability in SW480 cells. These findings suggest that STL or STB may have great potential for the development of anti-cancer drug.

A Dual Role of Heme Oxygenase-1 in Cancer Cells

Heme oxygenase (HO)-1 is known to metabolize heme into biliverdin/bilirubin, carbon monoxide, and ferrous iron, and it has been suggested to demonstrate cytoprotective effects against various stress-related conditions. HO-1 is commonly regarded as a survival molecule, exerting an important role in cancer progression and its inhibition is considered beneficial in a number of cancers. However, increasing studies have shown a dark side of HO-1, in which HO-1 acts as a critical mediator in ferroptosis induction and plays a causative factor for the progression of several diseases. Ferroptosis is a newly identified iron- and lipid peroxidation-dependent cell death. The critical role of HO-1 in heme metabolism makes it an important candidate to mediate protective or detrimental effects via ferroptosis induction. This review summarizes the current understanding on the regulatory mechanisms of HO-1 in ferroptosis. The amount of cellular iron and reactive oxygen species (ROS) is the determinative momentum for the role of HO-1, in which excessive cellular iron and ROS tend to enforce HO-1 from a protective role to a perpetrator. Despite the dark side that is related to cell death, there is a prospective application of HO-1 to mediate ferroptosis for cancer therapy as a chemotherapeutic strategy against tumors.