Heme oxygenase-1 protects against apoptosis induced by tumor necrosis factor-alpha and cycloheximide in papillary thyroid carcinoma cells

Mechanisms of Heavy Metal Cadmium (Cd)-Induced Malignancy

The environmental pollution of cadmium is worsening, and its significant carcinogenic effects on humans have been confirmed. Cadmium can induce cancer through various signaling pathways, including the ERK/JNK/p38MAPK, PI3K/AKT/mTOR, NF-κB, and Wnt. It can also cause cancer by directly damaging DNA and inhibiting DNA repair systems, or through epigenetic mechanisms such as abnormal DNA methylation, LncRNA, and microRNA. However, the detailed mechanisms of Cd-induced cancer are still not fully understood and require further investigation.

Targeting Nrf2 to treat thyroid cancer

Oxidative stress (OS) is recognized as a contributing factor in the development and progression of thyroid cancer. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a pivotal transcription factor involved in against OS generated by excessive reactive oxygen species (ROS). It governs the expression of a wide array of genes implicated in detoxification and antioxidant pathways. However, studies have demonstrated that the sustained activation of Nrf2 can contribute to tumor progression and drug resistance in cancers. The expression of Nrf2 was notably elevated in papillary thyroid cancer tissues compared to normal tissues, indicating that Nrf2 may play an oncogenic role in the development of papillary thyroid cancer. Nrf2 and its downstream targets are involved in the progression of thyroid cancer by impacting the prognosis and ferroptosis. Furthermore, the inhibition of Nrf2 can increase the sensitivity of target therapy in thyroid cancer. Therefore, Nrf2 appears to be a potential therapeutic target for the treatment of thyroid cancer. This review summarized current data on Nrf2 expression in thyroid cancer, discussed the function of Nrf2 in thyroid cancer, and analyzed various strategies to inhibit Nrf2.

Heme Oxygenase-1 and Its Role in Colorectal Cancer

Heme oxygenase-1 (HO-1) is an enzyme located at the endoplasmic reticulum, which is responsible for the degradation of cellular heme into ferrous iron, carbon monoxide and biliverdin-IXa. In addition to this main function, the enzyme is involved in many other homeostatic, toxic and cancer-related mechanisms. In this review, we first summarize the importance of HO-1 in physiology and pathophysiology with a focus on the digestive system. We then detail its structure and function, followed by a section on the regulatory mechanisms that control HO-1 expression and activity. Moreover, HO-2 as important further HO isoform is discussed, highlighting the similarities and differences with regard to HO-1. Subsequently, we describe the direct and indirect cytoprotective functions of HO-1 and its breakdown products carbon monoxide and biliverdin-IXa, but also highlight possible pro-inflammatory effects. Finally, we address the role of HO-1 in cancer with a particular focus on colorectal cancer. Here, relevant pathways and mechanisms are presented, through which HO-1 impacts tumor induction and tumor progression. These include oxidative stress and DNA damage, ferroptosis, cell cycle progression and apoptosis as well as migration, proliferation, and epithelial-mesenchymal transition.

Nrf2 as a novel diagnostic biomarker for papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy. However, it is very difficult to distinguish PTC from benign carcinoma. Thus, specific diagnostic biomarkers are actively pursued. Previous studies observed that Nrf2 was highly expressed in PTC. Based on this research, we hypothesized that Nrf2 may serve as a novel specific diagnostic biomarker. A single-center retrospective study, including 60 patients with PTC and 60 patients with nodular goiter, who underwent thyroidectomy at the Central Theater General Hospital from 2018 to July 2020, was conducted. The clinical data of the patients were collected. Nrf2, BRAF V600E, CK-19, and Gal-3 proteins were compared from paraffin samples of the patients. Through this study, we obtained the following results: i) Nrf2 exhibits high abundance expression in PTC, but not in adjacent to PTC and nodular goiter; increased Nrf2 expression could serve as a valuable biomarker for PTC diagnosis; the sensitivity and specificity for the diagnosis of PTC were 96.70% and 89.40%, respectively. ii) Nrf2 also shows higher expression in PTC with lymph node metastasis, but not adjacent to PTC and nodular goiter, thus the increased Nrf2 expression might serve as a valuable predictor for lymph node metastasis in PTC patients; the sensitivity and specificity for the prediction in lymph node metastasis were 96.00% and 88.57%, respectively; excellent diagnostic agreements were found between Nrf2 and other routine parameters including HO-1, NQO1 and BRAF V600E. iii) The downstream molecular expression of Nrf2 including HO-1 and NQO1 consistently increased. In conclusion, Nrf2 displays a high abundance expression in human PTC, which leads to the higher expression of downstream transcriptional proteins: HO-1 and NQO1. Moreover, Nrf2 can be used as an extra biomarker for differential diagnosis of PTC and a predictive biomarker for lymph node metastasis of PTC.

Relationship between 4-Hydroxynonenal (4-HNE) as Systemic Biomarker of Lipid Peroxidation and Metabolomic Profiling of Patients with Prostate Cancer

An oxidative degradation product of the polyunsaturated fatty acids, 4-hydroxynonenal (4-HNE), is of particular interest in cancer research due to its concentration-dependent pleiotropic activities affecting cellular antioxidants, metabolism, and growth control. Although an increase in oxidative stress and lipid peroxidation was already associated with prostate cancer progression a few decades ago, the knowledge of the involvement of 4-HNE in prostate cancer tumorigenesis is limited. This study investigated the appearance of 4-HNE-protein adducts in prostate cancer tissue by immunohistochemistry using a genuine 4-HNE monoclonal antibody. Plasma samples of the same patients and samples of the healthy controls were also analyzed for the presence of 4-HNE-protein adducts, followed by metabolic profiling using LC-ESI-QTOF-MS and GC-EI-Q-MS. Finally, the analysis of the metabolic pathways affected by 4-HNE was performed. The obtained results revealed the absence of 4-HNE-protein adducts in prostate carcinoma tissue but increased 4-HNE-protein levels in the plasma of these patients. Metabolomics revealed a positive association of different long-chain and medium-chain fatty acids with the presence of prostate cancer. Furthermore, while linoleic acid positively correlated with the levels of 4-HNE-protein adducts in the blood of healthy men, no correlation was obtained for cancer patients indicating altered lipid metabolism in this case. The metabolic pathway of unsaturated fatty acids biosynthesis emerged as significantly affected by 4-HNE. Overall, this is the first study linking 4-HNE adduction to plasma proteins with specific alterations in the plasma metabolome of prostate cancer patients. This study revealed that increased 4-HNE plasma protein adducts could modulate the unsaturated fatty acids biosynthesis pathway. It is yet to be determined if this is a direct result of 4-HNE or whether they are produced by the same underlying mechanisms. Further mechanistic studies are needed to grasp the biological significance of the observed changes in prostate cancer tumorigenesis.

Cycloheximide promotes type I collagen maturation mainly via collagen prolyl 4-hydroxylase subunit α2

Aberrant deposition of collagen is associated with cancer development and tissue fibrosis. Proline hydroxylation, catalyzed by collagen prolyl 4-hydroxylases (C-P4Hs), is necessary for collagen maturation and secretion. Here, we try to evaluate the mechanism of the regulation of CHX on collagen maturation. Using pepsin digestion, liquid chromatograph mass spectrometry and gene knockout, we find that treatment of mouse embryonic fibroblasts with cycloheximide (CHX) increases type I collagen proline hydroxylation partially via P4HA1 and mainly via P4HA2. Western blot analysis results show that CHX treatment reduces type I collagen but does not obviously impact the level of P4HA1/2 protein in the endoplasmic reticulum, which enhances the molar ratio of P4HA1/2 to type I collagen, and coimmunoprecipitation results confirm that more P4HA1/2 can bind to each type I collagen. Since C-P4Hs possess the capability to hydroxylate proline independent of ascorbate for a few cycles, this enhanced binding between P4HA1/2 and type I collagen can partially explain how CHX stimulates type I collagen maturation.

Internal Jugular Vein Thrombosis After Microwave Ablation of Cervical Lymph Node Metastasis in Papillary Thyroid Microcarcinoma: A Case Report

In this study, two patients with papillary thyroid carcinoma and lymph node metastasis were treated by Dr. Shurong Wang's team and are reported. The two patients refused surgery and underwent microwave ablation (MWA) of the thyroid and lymph node lesions. Ultrasound review 2 days after MWA revealed internal jugular vein thrombosis. Patient #1 received low molecular weight heparin calcium injection, Xueshuantong injection, Xiangdan injection, and rivaroxaban. Patient #2 was treated with enoxaparin sodium injection, Xueshuantong injection, urokinase, and warfarin sodium tablet. The thrombus was successfully managed in each patient using anticoagulant treatment. Such complication of MWA has not been reported in many cases before. According to the relevant literature, thrombosis after thyroid cancer ablation might be related to subclinical hypothyroidism, increased heme oxidase 1 (HO-1) levels in the blood of patients with papillary thyroid cancer, and increased platelet content and mean platelet volume in patients with thyroid cancer. No specific cause of thrombosis was identified in the two cases reported here. No recurrence was observed after 1 (patient #1) and 4 (#2) years of follow-up. In conclusion, patients with papillary thyroid carcinoma and lymph node metastasis should undergo color Doppler ultrasound of the neck after MWA of thyroid lesions and neck metastasis.

Quercetin Protects Human Thyroid Cells against Cadmium Toxicity

Various natural compounds have been successfully tested for preventing or counteracting the toxic effects of exposure to heavy metals. In this study, we analyzed the effects of cadmium chloride (CdCl₂) on immortalized, non-tumorigenic thyroid cells Nthy-ori-3-1. We investigated the molecular mechanism underlying its toxic action as well as the potential protective effect of quercetin against CdCl₂-induced damage. CdCl₂ suppressed cell growth in a dose- and time-dependent manner (IC50 value ~10 μM) associated with a decrease in levels of phospho-ERK. In addition, CdCl₂ elicited an increase in reactive oxygen species (ROS) production and lipid peroxidation. A significant increase in GRP78, an endoplasmic reticulum (ER) stress-related protein, was also observed. Supplementation of quercetin counteracted the growth-inhibiting action of CdCl₂ by recovering ERK protein phosphorylation levels, attenuating ROS overproduction, decreasing MDA content and reducing the expression of GRP78 in cells exposed to CdCl₂. Thus, in addition to revealing the molecular effects involved in cadmium-induced toxicity, the present study demonstrated, for the first time, a protective effect of quercetin against cadmium-induced damages to normal thyroid cells.

[Research on Analysis of Final Diagnosis and Prognostic Factors, and Development of New Therapeutic Drugs for Malignant Tumors (Especially Malignant Pediatric Tumors)]

Outcomes of treatment for malignant pediatric tumors including leukemia are improving by conventional multimodal treatment with strong chemotherapy, surgical resection, radiotherapy, and bone marrow transplantation. However, patients with advanced neuroblastoma, metastatic Ewing's sarcoma family of tumor (ESFT), and metastatic osteosarcoma continue to have an extremely poor prognosis. Therefore novel therapeutic strategies are urgently needed to improve their survival. Apoptotic cell death is a key mechanism for normal cellular homeostasis. Intact apoptotic mechanisms are pivotal for embryonic development, tissue remodeling, immune regulation, and tumor regression. Genetic aberrations disrupting programmed cell death often underpin tumorigenesis and drug resistance. Moreover, it has been suggested that apoptosis or cell differentiation proceeds to spontaneous regression in early stage neuroblastoma. Therefore apoptosis or cell differentiation is a critical event in this cancer. We extracted many compounds from natural plants (Angelica keiskei, Alpinia officiarum, Lycaria puchury-major, Brassica rapa) or synthesized cyclophane pyridine, indirubin derivatives, vitamin K3 derivatives, burchellin derivatives, and GANT61, and examined their effects on apoptosis, cell differentiation, and cell cycle in neuroblastoma and ESFT cell lines compared with normal cells. Some compounds were very effective against these tumor cells. These results suggest that they may be applicable as an efficacious and safe drug for the treatment of malignant pediatric tumors.

Roles of JNK/Nrf2 Pathway on Hemin-Induced Heme Oxygenase-1 Activation in MCF-7 Human Breast Cancer Cells

Heme oxygenase-1 (HO-1) is highly induced in various human disease states, including cancer, indicating that HO-1 is an emerging target of cancer therapy. In this study, we investigated that the mechanisms of hemin-induced HO-1 expression and its signaling pathways in human breast cancer cell. We used MCF-7 cells, a human breast cancer cell line. Hemin increased HO-1 expression in MCF-7 cells in a dose- and time-dependent manner. Hemin enhanced HO-1 expression through the activation of c-Jun N-terminal kinases (JNK) signaling pathway. Hemin also induced activation of Nrf2, a major transcription factor of HO-1 expression. These responses in MCF-7 cells were completely blocked by pretreatment with brazilin, a HO-1 regulator. These results indicated that brazilin inhibits hemin-induced HO-1 expressions through inactivation of JNK/Nrf2 in MCF-7 cells. Thus, our findings suggest that HO-1 is an important anticancer-target of brazilin in human breast cancer.

SCREENED: A Multistage Model of Thyroid Gland Function for Screening Endocrine-Disrupting Chemicals in a Biologically Sex-Specific Manner

Endocrine disruptors (EDs) are chemicals that contribute to health problems by interfering with the physiological production and target effects of hormones, with proven impacts on a number of endocrine systems including the thyroid gland. Exposure to EDs has also been associated with impairment of the reproductive system and incidence in occurrence of obesity, type 2 diabetes, and cardiovascular diseases during ageing. SCREENED aims at developing in vitro assays based on rodent and human thyroid cells organized in three different three-dimensional (3D) constructs. Due to different levels of anatomical complexity, each of these constructs has the potential to increasingly mimic the structure and function of the native thyroid gland, ultimately achieving relevant features of its 3D organization including: 1) a 3D organoid based on stem cell-derived thyrocytes, 2) a 3D organoid based on a decellularized thyroid lobe stromal matrix repopulated with stem cell-derived thyrocytes, and 3) a bioprinted organoid based on stem cell-derived thyrocytes able to mimic the spatial and geometrical features of a native thyroid gland. These 3D constructs will be hosted in a modular microbioreactor equipped with innovative sensing technology and enabling precise control of cell culture conditions. New superparamagnetic biocompatible and biomimetic particles will be used to produce "magnetic cells" to support precise spatiotemporal homing of the cells in the 3D decellularized and bioprinted constructs. Finally, these 3D constructs will be used to screen the effect of EDs on the thyroid function in a unique biological sex-specific manner. Their performance will be assessed individually, in comparison with each other, and against in vivo studies. The resulting 3D assays are expected to yield responses to low doses of different EDs, with sensitivity and specificity higher than that of classical 2D in vitro assays and animal models. Supporting the "Adverse Outcome Pathway" concept, proteogenomic analysis and biological computational modelling of the underlying mode of action of the tested EDs will be pursued to gain a mechanistic understanding of the chain of events from exposure to adverse toxic effects on thyroid function. For future uptake, SCREENED will engage discussion with relevant stakeholder groups, including regulatory bodies and industry, to ensure that the assays will fit with purposes of ED safety assessment. In this project review, we will briefly discuss the current state of the art in cellular assays of EDs and how our project aims at further advancing the field of cellular assays for EDs interfering with the thyroid gland.

Enhancing responsiveness of pancreatic cancer cells to gemcitabine treatment under hypoxia by heme oxygenase-1 inhibition

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies and has one of the worst prognoses leading to a meager 5-year survival rate of ∼8%. Chemotherapy has had limited success in extending the life span of patients with advanced PDAC due to poor tumor perfusion and hypoxia-induced resistance. Hypoxia reprograms the gene expression profile and upregulates the expression of multiple genes including heme oxygenase-1 (HO-1), which provide survival advantage to PDAC cells. However, the relationships between HO-1, hypoxia, and response to chemotherapy is unclear. Our results showed that hypoxia upregulates the expression of HO-1 in PDAC cells, and HO-1 inhibition using the HO-1 inhibitors zinc protoporphyrin, tin protoporphyrin IX (SnPP), and HO-1 knockout using CRISPR/Cas9 suppresses the proliferation of PDAC cells under hypoxia and sensitize them to gemcitabine under in vitro conditions. Treating orthotopic tumors with SnPP, or SnPP in combination with gemcitabine, significantly reduced the weight of pancreatic tumors (P < 0.05), decreased metastasis and improved the efficacy of gemcitabine treatment (P < 0.05). Mechanistically, inhibition of HO-1 increased the production of reactive oxygen species as demonstrated by increased dihydroethidium, and Mitosox, disrupted glutathione cycle, and enhanced apoptosis. There was significant increase in cleaved caspase-3 staining in tumors after combined treatment with SnPP and gemcitabine comparing to control or gemcitabine alone. In addition, inhibiting HO-1 reduced expression of stemness markers (CD133, and CD44) as compared to control or gemcitabine. Overall, our study may present a novel therapeutic regimen that might be adopted for the treatment of PDAC patients.

Fasting and cancer: molecular mechanisms and clinical application

The vulnerability of cancer cells to nutrient deprivation and their dependency on specific metabolites are emerging hallmarks of cancer. Fasting or fasting-mimicking diets (FMDs) lead to wide alterations in growth factors and in metabolite levels, generating environments that can reduce the capability of cancer cells to adapt and survive and thus improving the effects of cancer therapies. In addition, fasting or FMDs increase resistance to chemotherapy in normal but not cancer cells and promote regeneration in normal tissues, which could help prevent detrimental and potentially life-threatening side effects of treatments. While fasting is hardly tolerated by patients, both animal and clinical studies show that cycles of low-calorie FMDs are feasible and overall safe. Several clinical trials evaluating the effect of fasting or FMDs on treatment-emergent adverse events and on efficacy outcomes are ongoing. We propose that the combination of FMDs with chemotherapy, immunotherapy or other treatments represents a potentially promising strategy to increase treatment efficacy, prevent resistance acquisition and reduce side effects.

Heme Oxygenase-1 Inhibitors Induce Cell Cycle Arrest and Suppress Tumor Growth in Thyroid Cancer Cells

Heme oxygenase-1 (HO-1) is induced by a variety of stimuli and plays a multifaceted role in cellular protection. We have shown that HO-1 is overexpressed in thyroid cancer and is associated with tumor aggressiveness. Therefore, we set out to assess the effects of HO-1 inhibitors on the biology of thyroid cancer cells. Two different classes of HO-1 inhibitors were used, including a metalloporphyrin, zinc protoporphyrin-IX (ZnPP), and an azole antifungal agent, ketoconazole. The viability and colony formation of thyroid cancer cells decreased in a concentration- and time-dependent fashion following treatment with HO-1 inhibitors. Cancer cells exhibited a higher sensitivity to HO-1 inhibitors than non-malignant cells. HO-1 inhibitors induced a G0/G1 arrest accompanied by decreased cyclin D1 and CDK4 expressions and an increase in levels of p21 and p27. HO-1 inhibitors significantly increased intracellular ROS levels and suppressed cell migration and invasion. Oxygen consumption rate and mitochondrial mass were increased with ZnPP treatment. Mice treated with ZnPP had a reduced xenograft growth and diminished cyclin D1 and Ki-67 staining in tumor sections. Taken together, HO-1 inhibitors might have therapeutic potential for inducing cell cycle arrest and promoting growth suppression of thyroid cancer cells in vitro and in vivo.

Overview of Cadmium Thyroid Disrupting Effects and Mechanisms

Humans are exposed to a significant number of chemicals that are suspected to produce disturbances in hormone homeostasis. Hence, in recent decades, there has been a growing interest in endocrine disruptive chemicals. One of the alleged thyroid disrupting substances is cadmium (Cd), a ubiquitous toxic metal shown to act as a thyroid disruptor and carcinogen in both animals and humans. Multiple PubMed searches with core keywords were performed to identify and evaluate appropriate studies which revealed literature suggesting evidence for the link between exposure to Cd and histological and metabolic changes in the thyroid gland. Furthermore, Cd influence on thyroid homeostasis at the peripheral level has also been hypothesized. Both in vivo and in vitro studies revealed that a Cd exposure at environmentally relevant concentrations results in biphasic Cd dose-thyroid response relationships. Development of thyroid tumors following exposure to Cd has been studied mainly using in vitro methodologies. In the thyroid, Cd has been shown to activate or stimulate the activity of various factors, leading to increased cell proliferation and a reduction in normal apoptotic activity. Evidence establishing the association between Cd and thyroid disruption remains ambiguous, with further studies needed to elucidate the issue and improve our understanding of Cd-mediated effects on the thyroid gland.

hnRNPK-regulated PTOV1-AS1 modulates heme oxygenase-1 expression via miR-1207-5p

Antisense transcripts were initially identified as transcriptional noise, but have since been reported to play an important role in the quality control of miRNA functions. In this report, we tested the hypothesis that heterogeneous nuclear ribonucleoprotein K (hnRNPK) regulates miRNA function via competitive endogenous RNAs, such as pseudogenes, long non-coding RNAs, and antisense transcripts. Based on analyses of RNA sequencing data, the knockdown of hnRNPK decreased the antisense PTOV1-AS1 transcript which harbors five binding sites for miR-1207-5p. We identified heme oxygenase-1 (HO-1) mRNA as a novel target of miR-1207-5p by western blotting and Ago2 immunoprecipitation. The knockdown of hnRNPK or PTOV1-AS1 suppressed HO-1 expression by increasing the enrichment of HO-1 mRNA in miR-1207-5p-mediated miRISC. Downregulation of HO-1 by a miR-1207-5p mimic or knockdown of hnRNPK and PTOV1-AS1 inhibited the proliferation and clonogenic ability of HeLa cells. Taken together, our results demonstrate that hnRNPKregulated PTOV1-AS1 modulates HO-1 expression via miR- 1207-5p. [BMB Reports 2017; 50(4): 220-225].

High expression of HO-1 predicts poor prognosis of ovarian cancer patients and promotes proliferation and aggressiveness of ovarian cancer cells

PURPOSE

HO-1 has been proved to be associated with tumor aggressivity and poor prognosis in various cancers. Our study provides the first study to demonstrate the relationship of HO-1 expression and clinical characteristics in ovarian cancer patients.

METHODS

Immunohistochemistry and western blotting were used to examine the expression of HO-1 in tissue species and fresh tissues. CCK-8 was used to investigate cell viability. Transwell chamber was performed to estimate migration and invasion capacities in A2780 and Skov-3 cells.

RESULTS

Immunohistochemistry and western blotting showed that the expression of HO-1 was higher in ovarian cancer tissues than normal ovarian tissues. High expression of HO-1 was significantly associated with serous ovarian cancer, high FIGO stage, lymph node metastasis, and non-optimal debulking. Patients with high expression of HO-1 exhibited an unfavorable prognosis. In vitro inducing the expression of HO-1 promoted the proliferation and metastasis of A2780 and Skov-3 cells, with the increased expressions of mesenchymal marker (Vimentin), epithelial-mesenchymal transition-associated transcript factor (Zeb-1), anti-apoptotic protein (Bcl-2), and the decreased expressions of epithelial marker (Keratin) and pro-apoptotic protein (Bax). Meanwhile, after incubating A2780 and Skov-3 together with HO-1 inhibitor, above results could be reversed.

CONCLUSION

HO-1 might be a potential marker for prediction of ovarian cancer prognosis and a target for ovarian cancer treatment.

Heme Oxygenase Database (HemeOxDB) and QSAR Analysis of Isoform 1 Inhibitors

Due to increasing interest in the field of heme oxygenases (HOs), we built a ligand database called HemeOxDB that includes the entire set of known HO-1 and HO-2 inhibitors, resulting in more than 400 compounds. The HemeOxDB is available online at http://www.researchdsf.unict.it/hemeoxdb/, and having a robust search engine allows end users to build complex queries, sort tabulated results, and generate color-coded two- and three-dimensional graphs. This database will grow to be a tool for the design of potent and selective HO-1 or HO-2 inhibitors. We were also interested in virtually searching for alternative inhibitors, and, for the first time in the field of HOs, a quantitative structure-activity relationship (QSAR) model was built using half-maximal inhibitory concentration (IC₅₀ ) values of the whole set of known HO-1 inhibitors, taken from the HemeOxDB and employing the Monte Carlo technique. The statistical quality suggested that the model is robust and possesses desirable predictive potential. The screening of US Food and Drug Administration (FDA)-approved drugs, external to our dataset, suggested new predicted inhibitors, opening the way for replacing imidazole groups. The HemeOxDB and the QSAR model reported herein may help in prospectively identifying or repurposing new drugs with optimal structural attributes for HO enzyme inhibition.

A blood pressure-associated variant of the SLC39A8 gene influences cellular cadmium accumulation and toxicity

Genome-wide association studies have revealed a relationship between inter-individual variation in blood pressure and the single nucleotide polymorphism rs13107325 in the SLC39A8 gene. This gene encodes the ZIP8 protein which co-transports divalent metal cations, including heavy metal cadmium, the accumulation of which has been associated with increased blood pressure. The polymorphism results in two variants of ZIP8 with either an alanine (Ala) or a threonine (Thr) at residue 391. We investigated the functional impact of this variant on protein conformation, cadmium transport, activation of signalling pathways and cell viability in relation to blood pressure regulation. Following incubation with cadmium, higher intracellular cadmium was detected in cultured human embryonic kidney cells (HEK293) expressing heterologous ZIP8-Ala391, compared with HEK293 cells expressing heterologous ZIP8-Thr391. This Ala391-associated cadmium accumulation also increased the phosphorylation of the signal transduction molecule ERK2, activation of the transcription factor NFκB, and reduced cell viability. Similarly, vascular endothelial cells with the Ala/Ala genotype had higher intracellular cadmium concentration and lower cell viability than their Ala/Thr counterpart following cadmium exposure. These results indicate that the ZIP8 Ala391-to-Thr391 substitution has an effect on intracellular cadmium accumulation and cell toxicity, providing a potential mechanistic explanation for the association of this genetic variant with blood pressure.

Fasting-Mimicking Diet Reduces HO-1 to Promote T Cell-Mediated Tumor Cytotoxicity

Immune-based interventions are promising strategies to achieve long-term cancer-free survival. Fasting was previously shown to differentially sensitize tumors to chemotherapy while protecting normal cells, including hematopoietic stem and immune cells, from its toxic side effects. Here, we show that the combination of chemotherapy and a fasting-mimicking diet (FMD) increases the levels of bone marrow common lymphoid progenitor cells and cytotoxic CD8(+) tumor-infiltrating lymphocytes (TILs), leading to a major delay in breast cancer and melanoma progression. In breast tumors, this effect is partially mediated by the downregulation of the stress-responsive enzyme heme oxygenase-1 (HO-1). These data indicate that FMD cycles combined with chemotherapy can enhance T cell-dependent targeted killing of cancer cells both by stimulating the hematopoietic system and by enhancing CD8(+)-dependent tumor cytotoxicity.

Knockdown of heme oxygenase-1 promotes apoptosis and autophagy and enhances the cytotoxicity of doxorubicin in breast cancer cells

Heme oxygenase-1 (HMOX-1) is a microsomal enzyme that exerts anti-apoptotic and cytoprotective effects. In the present study, HMOX-1 was demonstrated to be overexpressed and able to be induced by doxorubicin in breast cancer cell lines. Knockdown of HMOX-1 using short interfering (si)RNA enhanced the cytotoxicity of doxorubicin in MDA-MB-231 and BT549 cells. Knockdown of HMOX-1 downregulated B cell lymphoma (Bcl)-2 and Bcl-extra large expression, and significantly enhanced doxorubicin-induced apoptosis in MDA-MB-231 and BT549 cells. Additionally, knockdown of HMOX-1 upregulated light chain 3B expression and markedly increased the accumulation of autophagic vacuoles in MDA-MB-231 and BT549 cells treated with doxorubicin. These results indicated that HMOX-1 may be involved in conferring the chemoresistance of breast cancer cells, by preventing apoptosis and autophagy. Therefore, HMOX-1 may represent a potential therapeutic target for enhancing the cytotoxicity and efficacy of doxorubicin during the treatment of breast cancer.

Tobacco carcinogen NNK-induced lung cancer animal models and associated carcinogenic mechanisms

Tobacco usage is a major risk factor in the development, progression, and outcomes for lung cancer. Of the carcinogens associated with lung cancer, tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is among the most potent ones. The oncogenic mechanisms of NNK are not entirely understood, hindering the development of effective strategies for preventing and treating smoking-associated lung cancers. Here, we introduce the NNK-induced lung cancer animal models in different species and its potential mechanisms. Finally, we summarize several chemopreventive agents developed from these animal models.

Heme oxygenase-1: emerging target of cancer therapy

Heme oxygenase-1 (HO-1) is a rate-limiting enzyme catalyzing oxidative degradation of cellular heme to liberate free iron, carbon monoxide (CO) and biliverdin in mammalian cells. In addition to its primary role in heme catabolism, HO-1 exhibits anti-oxidative and anti-inflammatory functions via the actions of biliverdin and CO, respectively. HO-1 is highly induced in various disease states, including cancer. Several lines of evidence have supported the implication of HO-1 in carcinogenesis and tumor progression. HO-1 deficiency in normal cells enhances DNA damage and carcinogenesis. Nevertheless, HO-1 overexpression in cancer cells promotes proliferation and survival. Moreover, HO-1 induces angiogenesis through modulating expression of angiogenic factors. Although HO-1 is an endoplasmic reticulum resident protein, HO-1 nuclear localization is evident in tumor cells of cancer tissues. It has been shown that HO-1 is susceptible to proteolytic cleavage and translocates to nucleus to facilitate tumor growth and invasion independent of its enzymatic activity. HO-1 also impacts cancer progression through modulating tumor microenvironment. This review summarizes the current understanding of the protumorigenic role of HO-1 and its potential as a molecular target for cancer therapy.

Expression of haem oxygenase-1 correlates with tumour aggressiveness and BRAF V600E expression in thyroid cancer

AIMS

Haem oxygenase-1 (HO-1) is an inducible enzyme that participates in haem degradation. Recent studies have indicated that HO-1 activation may play a role in tumour development and progression. The aim of this study was to evaluate the expression of HO-1 in thyroid cancer and its clinicopathological significance.

METHODS AND RESULTS

We observed up-regulation of HO-1 in papillary thyroid tumours in comparison with normal thyroid tissue. Immunohistochemical analysis revealed that 48% of papillary cancers and 36% of follicular cancers, but none of normal thyroid tissues, were positive for HO-1 expression. Among 129 differentiated thyroid cancers, HO-1 expression was associated with patient age (P = 0.001), TNM stage (P = 0.001), and Mayo Clinic metastasis, patient age, completeness of resection, local invasion and tumour size score (P = 0.001). BRAF V600E expression was evaluated immunohistochemically and validated by Sanger sequencing. There was a strong association between HO-1 and BRAF V600E expression in papillary cancers (P = 0.002).

CONCLUSIONS

Overexpression of HO-1 in a subset of thyroid cancers is associated with tumour aggressiveness and BRAF V600E expression. HO-1 might have a potential role in prognosis and targeted treatment in patients with thyroid cancer.

The cross-talk between estrogen receptor and peroxisome proliferator-activated receptor gamma in thyroid cancer

BACKGROUND

Estrogen receptor (ER) and peroxisome proliferator-activated receptor gamma (PPARγ) are associated with thyroid tumorigenesis and treatment. However, the interaction between them has not been studied.

METHODS

The impact of ER over-expression or down-expression by DNA/small interfering RNA (siRNA) transfection, ERα agonists, and the ERβ agonist diarylpropiolnitrile (DPN) on PPARγ expression/activity was examined in papillary thyroid carcinoma (PTC) and anaplastic thyroid carcinoma (ATC) cells. The effects of PPARγ modulation by rosiglitazone (RTZ), a PPARγ ligand, and of PPARγ siRNA on ER expression were determined. Cellular functions reflected by cell proliferation and migration were assayed. Apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick-end labeling, and apoptotic-related proteins were evaluated by Western blot analysis.

RESULTS

PPARγ protein and activity were reduced by the over-expression of either ERα or ERβ, whereas repression of ERα or ERβ increased PPARγ expression. The administration of RTZ counteracted the effects of ER and also reduced their expression, particularly in PTC cells. Moreover, knockdown of PPARγ increased ER expression and activity. Functionally, ERα activation offset the inhibitory effect of PPARγ on cellular functions, but ERβ activation aggregated it and induced apoptosis, particularly in PTC cells. Finally, the interaction between ERβ and PPARγ enhanced the expression of proapoptotic molecules, such as caspase-3 and apoptosis-inducing factor.

CONCLUSIONS

This study provides evidence supporting a cross-talk between ER and PPARγ. The reciprocal interaction between PPARγ and ERβ significantly inhibits the proliferation and migration of thyroid cancer cells, providing a new therapeutic strategy against thyroid cancer.

Overexpressions of HO-1/HO-1G143H in C57/B6J mice affect melanoma B16F10 lung metastases rather than change the survival rate of mice-bearing tumours

Heme oxygenase-1 (HO-1) is often upregulated in tumour tissues and endows tumour cells with cytoprotection and antiapoptosis. It is worthy of note that some people show higher activity of HO-1 and some anti-cancer therapies could induce HO-1 expression in normal tissues, but the effect of HO-1 of normal tissues on tumours among these people remains unknown. To assess the effect of HO-1 of normal tissues on tumour progressiveness, we investigated the growth, metastasis and angiogenic potential of murine melanoma B16F10 cells in transgenic mice overexpressing HO-1 and its negative dominant mutant HO-1G143H, respectively. The results demonstrated that neither overexpression of HO-1 nor overexpression of HO-1G143H in normal tissues could significantly change the survival rate of tumour-bearing mice, but HO-1 overexpression could inhibit lung metastases and HO-1G143H could significantly promote lung metastases. Meanwhile, the leukocytes infiltration was reduced and angiogenesis was promoted in tumours in mice overexpressing HO-1, but the opposite was true in mice overexpressing HO-1G143H. Our findings suggested that overexpression of HO-1 might be conducive to patients bearing melanoma metastasis.

TRC8 suppresses tumorigenesis through targeting heme oxygenase-1 for ubiquitination and degradation

The TRC8 gene, which was previously shown to be disrupted by a 3;8 chromosomal translocation in hereditary kidney cancer, encodes for an endoplasmic reticulum-resident E3 ligase. Studies have shown that TRC8 exhibits a tumor-suppressive effect through its E3-ligase activity. Therefore, the identification of its physiological substrates will provide important insights into the molecular mechanism underlying TRC8-mediated tumor suppression. Here we show that TRC8 targets heme oxygenase-1 (HO-1), an antioxidant enzyme highly expressed in various cancers, for ubiquitination and degradation. Ectopic TRC8 expression suppresses HO-1-induced cancer cell growth and migration/invasion. Conversely, HO-1 depletion reduced the tumorigenic and invasive capacities promoted by TRC8 knockdown. HO-1 downregulation in renal carcinoma cells induces a mitotic delay at G2/M phase by increasing the intracellular reactive oxygen species and the DNA-damage-induced checkpoint activation. These results highlight the tumorigenic role of HO-1 and the importance of TRC8-mediated HO-1 degradation in the control of cancer growth.

Carbon monoxide mediates the anti-apoptotic effects of heme oxygenase-1 in medulloblastoma DAOY cells via K+ channel inhibition

Tumor cell survival and proliferation is attributable in part to suppression of apoptotic pathways, yet the mechanisms by which cancer cells resist apoptosis are not fully understood. Many cancer cells constitutively express heme oxygenase-1 (HO-1), which catabolizes heme to generate biliverdin, Fe(2+), and carbon monoxide (CO). These breakdown products may play a role in the ability of cancer cells to suppress apoptotic signals. K(+) channels also play a crucial role in apoptosis, permitting K(+) efflux which is required to initiate caspase activation. Here, we demonstrate that HO-1 is constitutively expressed in human medulloblastoma tissue, and can be induced in the medulloblastoma cell line DAOY either chemically or by hypoxia. Induction of HO-1 markedly increases the resistance of DAOY cells to oxidant-induced apoptosis. This effect was mimicked by exogenous application of the heme degradation product CO. Furthermore we demonstrate the presence of the pro-apoptotic K(+) channel, Kv2.1, in both human medulloblastoma tissue and DAOY cells. CO inhibited the voltage-gated K(+) currents in DAOY cells, and largely reversed the oxidant-induced increase in K(+) channel activity. p38 MAPK inhibition prevented the oxidant-induced increase of K(+) channel activity in DAOY cells, and enhanced their resistance to apoptosis. Our findings suggest that CO-mediated inhibition of K(+) channels represents an important mechanism by which HO-1 can increase the resistance to apoptosis of medulloblastoma cells, and support the idea that HO-1 inhibition may enhance the effectiveness of current chemo- and radiotherapies.

ATP-dependent mitochondrial porphyrin importer ABCB6 protects against phenylhydrazine toxicity

Abcb6 is a mammalian mitochondrial ATP-binding cassette (ABC) transporter that regulates de novo porphyrin synthesis. In previous studies, haploinsufficient (Abcb6(+/-)) embryonic stem cells showed impaired porphyrin synthesis. Unexpectedly, Abcb6(-/-) mice derived from these stem cells appeared phenotypically normal. We hypothesized that other ATP-dependent and/or -independent mechanisms conserve porphyrins. Here, we demonstrate that Abcb6(-/-) mice lack mitochondrial ATP-driven import of coproporphyrin III. Gene expression analysis revealed that loss of Abcb6 results in up-regulation of compensatory porphyrin and iron pathways, associated with elevated protoporphyrin IX (PPIX). Phenylhydrazine-induced stress caused higher mortality in Abcb6(-/-) mice, possibly because of sustained elevation of PPIX and an inability to convert PPIX to heme despite elevated ferrochelatase levels. Therefore, Abcb6 is the sole ATP-dependent porphyrin importer, and loss of Abcb6 produces up-regulation of heme and iron pathways necessary for normal development. However, under extreme demand for porphyrins (e.g. phenylhydrazine stress), these adaptations appear inadequate, which suggests that under these conditions Abcb6 is important for optimal survival.

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

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

Aged red garlic extract reduces cigarette smoke extract-induced cell death in human bronchial smooth muscle cells by increasing intracellular glutathione levels

Increasing antioxidant capacity has been proposed as a promising strategy to prevent cigarette smoke-induced lung diseases. This study tested whether garlic extracts prevented cigarette smoke extract (CSE)-induced cell death in human bronchial smooth muscle cells (HBSMCs). Garlic extracts were prepared from fresh raw garlic (FRG), aged black garlic (ABG) and aged red garlic (ARG). Treatment of HBSMCs with 10% CSE induced cell death accompanied by activation of caspase. Of the garlic extracts, treatment with ARG extract reduced CSE-induced cell death. The combination of ARG extract with CSE attenuated the CSE-induced reduction in glutathione (GSH) content, generation of reactive oxygen species (ROS) and induction of heme oxygenase-1 expression compared with CSE treatment without ARG extract. Furthermore, the combination of L-BSO, a GSH synthesis inhibitor, with ARG and CSE extracts failed to increase the intracellular GSH content and cell viability. Taken together, these results demonstrate that ARG extract reduces CSE-induced cell death by increasing GSH content and reducing ROS generation in HBSMCs.

Enhancement of temozolomide-induced apoptosis by valproic acid in human glioma cell lines through redox regulation

Temozolomide (TMZ) is an oral alkylating agent that has been widely used in the treatment of refractory glioma, although inherent and acquired resistance to this drug is common. The clinical use of valproic acid (VPA) as an anticonvulsant and mood-stabilizing drug has been reported primarily for the treatment of epilepsy and bipolar disorder and less commonly for major depression. VPA is also used in the treatment of glioma-associated seizures with or without intracranial operation. In this study, we evaluated the potential synergistic effect of TMZ and VPA in human glioma cell lines. Compared with the use of TMZ or VPA alone, concurrent treatment with both drugs synergistically induced apoptosis in U87MG cells as evidenced by p53 and Bax expression, mitochondrial transmembrane potential loss, reactive oxygen species production, and glutathione depletion. This synergistic effect correlated with a decrease in nuclear translocation of the nuclear factor-erythroid 2 p45-related factor and corresponded with reduced heme oxygenase-1 and γ-glutamylcysteine synthetase expression. Pretreatment with N-acetylcysteine partially recovered the apoptotic effect of the TMZ/VPA combination treatment. The same degree of synergism is also seen in p53-mutant Hs683 cells, which indicates that p53 may not play a major role in the increased proapoptotic effect of the TMZ/VPA combination. In conclusion, VPA enhanced the apoptotic effect of TMZ, possibly through a redox regulation mechanism. The TMZ/VPA combination may be effective for treating glioma cancer and may be a powerful agent against malignant glioma. This drug combination should be further explored in the clinical setting.

Docosahexaenoic acid suppresses neuroinflammatory responses and induces heme oxygenase-1 expression in BV-2 microglia: implications of antidepressant effects for ω-3 fatty acids

Accumulating evidence suggests that the pathophysiology of depression might be associated with neuroinflammation, which could be attenuated by pharmacological treatment for depression. Omega-3 polyunsaturated fatty acids (PUFAs) are anti-inflammatory and exert antidepressant effects. The aim of this study was to identify the molecular mechanisms through which docosahexaenoic acid (DHA), the main omega-3 PUFA in the brain, modulates oxidative reactions and inflammatory cytokine production in microglial and neuronal cells. The results of this study showed that DHA reduced expressions of tumor necrosis factor-α, interleukin-6, nitric oxide synthase, and cyclo-oxygenase-2, induced by interferon-γ, and induced upregulation of heme oxygenase-1 (HO-1) in BV-2 microglia. The inhibitory effect of DHA on nitric oxide production was abolished by HO-1 inhibitor zinc protoporphyrin IX. In addition, DHA caused AKT and ERK activation in a time-dependent manner, and the DHA-induced HO-1 upregulation could be attenuated by PI-3 kinase/AKT and MEK/ERK inhibitors. DHA also increased IKKα/β phosphorylation, IκBα phosphorylation, and IκBα degradation, whereas both nuclear factor-κB and IκB protease inhibitors could inhibit DHA-induced HO-1 expressions. The other major n-3 PUFA, eicosapentaenoic acid, showed similar effects of DHA on inflammation and HO-1 in repeated key experiments. In connecting with inflammation hypothesis of depression and clinical studies supporting the antidepressant effects of omega-3 PUFAs, this study provides a novel implication of the antidepressant mechanisms of DHA.

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

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

Fatty acid transduction of nitric oxide signaling: nitrolinoleic acid mediates protective effects through regulation of the ERK pathway

In vivo and in vitro studies revealed that nitroalkenes serve as protective mediators in the lung by inducing the cytoprotective enzyme heme oxygenase-1 (HO-1). Nitrolinoleic acid (LNO2) increased HO-1 mRNA, protein, and activity in cultured pulmonary epithelial cells treated with 5 to 50 microM LNO2 and in lungs of rats injected intraperitoneally with 2.6 mg/kg LNO2 twice daily for 20 days. Western blotting revealed that HO-1 protein increased significantly within 4 h of in vitro LNO2 addition and was preceded by an increase in HO-1 mRNA, consistent with transcriptional regulation of HO-1 expression by LNO2. LNO2 also dephosphorylated and activated eukaryotic initiation factor 2alpha, a key translational regulatory protein, indicating that increased translation may also contribute to LNO2-induced increases in HO-1. Exposure of cells to LNO2 activated ERK and JNK, as evidenced by increased phosphorylation. Downstream targets of ERK and JNK, Elk-1 and c-Jun, respectively, were also phosphorylated in response to LNO2 exposure. However, inhibitor studies revealed that only the ERK pathway is necessary for the LNO2-mediated increase in HO-1 mRNA and protein. These data reveal that LNO2 induces pulmonary epithelial HO-1 expression and downstream adaptive responses to inflammation via both transcriptional and translational regulatory mechanisms.

Inhibitors of the heme oxygenase - carbon monoxide system: on the doorstep of the clinic?

The past decade has seen substantial developments in our understanding of the physiology, pathology, and pharmacology of heme oxygenases (HO), to the point that investigators in the field are beginning to contemplate therapies based on administration of HO agonists or HO inhibitors. A significant amount of our current knowledge is based on the judicious application of metalloporphyrin inhibitors of HO, despite their limitations of selectivity. Recently, imidazole-based compounds have been identified as potent and more selective HO inhibitors. This 'next generation' of HO inhibitors offers a number of desirable characteristics, including isozyme selectivity, negligible effects on HO protein expression, and physicochemical properties favourable for in vivo distribution. Some of the applications of HO inhibitors that have been suggested are treatment of hyperbilirubinemia, neurodegenerative disorders, certain types of cancer, and bacterial and fungal infections. In this review, we address various approaches to altering HO activity with a focus on the potential applications of second-generation inhibitors of HO.

Reactive oxygen species: current knowledge and applications in cancer research and therapeutic

Reactive oxygen species (ROS) are natural products inevitably generated along cellular metabolism. Due to their highly reactive nature, which can damage DNA, proteins and lipids, cells utilize antioxidative or defense systems to balance these toxic products to keep the cells in a state of redox homeostasis. However, under the situation of imbalance in redox status, depending on the magnitude of ROS encountered, high levels of ROS can induce apoptosis, whereas chronic low levels of ROS promote vascular diseases such as arteriosclerosis. Although ROS seem to be catastrophic to life, accumulating evidence points to the beneficial roles of ROS by virtue of the ability as chemotherapeutic agents to cure human diseases. Many anti-cancer drugs have been developed in this way which can generate ROS and cause oxidative stress-induced apoptosis in cancer cells. The effects of ROS are paradoxical because they can act as both disease culprits and chemotherapeutic agents. In this review, the current knowledge of ROS and the potential applications of ROS in cancer therapeutic will be discussed.

Oestrogen mediates the growth of human thyroid carcinoma cells via an oestrogen receptor-ERK pathway

OBJECTIVES

Although thyroid cancer occurs much more frequently in females, the role of sex hormones in thyroid carcinogenesis is unknown. In this study, it has been investigated how 17beta-oestradiol (E2) influenced proliferation and growth of thyroid cancer cells.

MATERIALS AND METHODS

Cell proliferation and its related molecules were examined in thyroid papillary carcinoma cells (KAT5), follicular thyroid carcinoma cells (FRO) and anaplastic carcinoma cells (ARO). Levels of oestrogen receptor (ER) alpha and beta were regulated by their agonists (PPT and DPN), antagonists and siRNA.

RESULTS

E2 promoted cell proliferation. Such an effect was positively related to ERalpha but negatively to ERbeta; PPT enhanced cell proliferation while DPN inhibited it. PPT increased Bcl-2 expression while DPN decreased it. DPN also elevated Bax expression. PPT elevated the level of phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), suggesting a positive role of ERK1/2 in E2-induced cell proliferation. Knockdown of ERalpha significantly attenuated E2-mediated Bcl-2 and pERK1/2 expression. In contrast, knockdown of ERbeta markedly enhanced them.

CONCLUSIONS

Oestrogen stimulates proliferation of thyroid cancer cells, associated with increase in Bcl-2 and decrease in Bax levels in an ERK1/2-related pathway. Imbalance between ERalpha and ERbeta may contribute to thyroid carcinogenesis.

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

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

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.

Physiology and pathophysiology of heme: implications for kidney disease

An iron-containing, tetrapyrrole ring, heme is an essential prosthetic group in an array of proteins that comprehensively affect cellular function and metabolism; yet "free" heme in sufficient amounts can be damaging to the kidney and other organs because of its bioreactivity and pro-oxidant effects. This review discusses the cellular metabolism of heme in health and disease and covers such areas as the synthesis of heme and its utilization in heme proteins; mechanisms underlying the toxicity of heme; and the extent to which pathophysiologic processes, such as renal incorporation of heme proteins or destabilization of intracellular heme proteins, increase intracellular levels of heme and provoke renal injury. The main catabolic process that degrades heme, the heme oxygenase (HO) system, is reviewed, and evidence for the protective effects of HO-1 against acute and chronic heme/heme protein-induced renal injury is summarized. Finally, current views regarding the molecular basis for heme-induced upregulation of HO-1 are discussed.

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.

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.