3,3'-diindolylmethane reduces levels of HIF-1alpha and HIF-1 activity in hypoxic cultured human cancer cells

Sinensetin suppresses breast cancer cell progression via Wnt/β-catenin pathway inhibition

Background

Although there are many treatments for breast cancer, such as surgery, radiotherapy, chemotherapy, estrogen receptor antagonists, immune checkpoint inhibitors and so on. However, safer and more effective therapeutic drugs for breast cancer are needed. Sinensetin, a safer therapeutic drugs, come from citrus species and medicinal plants used in traditional medicine, while its role and underlying mechanism in breast cancer remain unclear. Our study aimed to investigate the role and mechanism of sinensetin in breast cancer.

Methods

Cell Counting Kit-8 (CCK-8) was used to determine the safe concentration of sinensetin in MCF-10A, MCF7 and MDA-MB-231 cells; 120 μM sinensetin was used in subsequent experiments. Real time polymerase chain reaction (RT-PCR), Western blotting, Terminal Deoxynucleotidyl Transferase mediated dUTP Nick-End Labeling (TUNEL) apoptosis assay, Transwell invasion assay and Clone formation assay were used in this study to determine cell viability, mRNA expression, protein levels, apoptosis, proliferation, invasion and so on.

Results

Herein, our results showed that 120 μM sinensetin suppressed the cell viability and promoted apoptosis of MCF7 and MDA-MB-231 cells. Treatment with 120 µM sinensetin for 24 h showed no significant toxicity to normal mammary cells; 120 μM sinensetin decreased cell proliferation, invasion, and epithelial-mesenchymal transition (EMT), and downregulated β-catenin, lymphatic enhancing factor 1 (LEF1), T-cell factor (TCF) 1/TCF7, and TCF3/TCF7L1 expression in MCF7 and MDA-MB-231 cells. The Wnt agonist SKL2001 reversed the inhibitory effect of sinensetin on cell survival, metastasis, and EMT. Sinensetin-induced downregulation of β-catenin, LEF1, and TCF1/TCF7 expression were upregulated by SKL2001 in MCF7 and MDA-MB-231 cells.

Conclusions

In summary, sinensetin suppressed the metastasis of breast cancer cell via inhibition of Wnt/β-catenin pathway and there were no adverse effects on normal breast cells. Our study confirmed the role of sinensetin in breast cancer cells and provided a better understanding of the underlying mechanism.

Nanoformulated 3'-diindolylmethane modulates apoptosis, migration, and angiogenesis in breast cancer cells

Background

It is well-established that specific herbal plants contain natural active ingredients that have demonstrated anti-cancer potential. Therefore, they are considered highly beneficial as a potential adjuvant, alternative or complementary agent in anti-cancer therapy. However, the low chemical stability and limited bioavailability of 3, 3'-Diindolylmethane (DIM), a plant-derived compound used in clinical settings, limit its therapeutic applications. To overcome this challenge, researchers have focused on developing innovative approaches to improve DIM's biological activity, such as utilizing nanoformulations. Here, we investigated the potential benefits of coating DIM nanoparticles (DIM-NPs) with PEG/chitosan in the treatment of breast cancer. Our results demonstrate the molecular mechanism underlying the activity of DIM-NPs, highlighting their potential as an effective therapeutic strategy for breast cancer treatment.

Methods

DIM-PLGA-PEG/chitosan NPs were synthesised and characterised using dynamic light scattering (DLS) and evaluated the impact of these NPs on two breast cancer cell models.

Results

DIM-NPs had an average diameter of 102.3 nm and a PDI of 0.182. When treated with DIM-NPs for 48 h, both MCF7 and MDA-MB-231 cells displayed cytotoxicity at a concentration of 6.25 g/mL compared to untreated cells. Furthermore, in MDA-MB-231 cells, treatment with 2.5 μg/mL of DIM-NPs resulted in a significant decrease in cell migration, propagation, and angiogenesis which was further enhanced at 10 μg/mL. In chicken embryos, treatment with 5 μg/mL of DIM-NPs on day 2 led to a significant reduction in angiogenesis. Furthermore, this treatment induced cell death through a regulatory pathway involving the upregulation of Bax and p53, as well as the downregulation of Bcl-2. These results were supported by in-silico analysis of DIM's binding affinity to key proteins involved in this pathway, namely Bax, Bcl-2, and p53.

Conclusion

Our findings show that DIM-NPs induces apoptosis, inhibit migration, and reduce angiogenesis in breast cancer. However, further research using a preclinical cancer model may be necessary to determine the pharmacokinetics of DIM-NPs and ensure their safety and efficacy in vivo.

Natural products derived from medicinal plants and microbes might act as a game-changer in breast cancer: a comprehensive review of preclinical and clinical studies

Breast cancer (BC) is the most prevalent neoplasm among women. Genetic and environmental factors lead to BC development and on this basis, several preventive - screening and therapeutic interventions have been developed. Hormones, both in the form of endogenous hormonal signaling or hormonal contraceptives, play an important role in BC pathogenesis and progression. On top of these, breast microbiota includes both species with an immunomodulatory activity enhancing the host's response against cancer cells and species producing proinflammatory cytokines associated with BC development. Identification of novel multitargeted therapeutic agents with poly-pharmacological potential is a dire need to combat advanced and metastatic BC. A growing body of research has emphasized the potential of natural compounds derived from medicinal plants and microbial species as complementary BC treatment regimens, including dietary supplements and probiotics. In particular, extracts from plants such as Artemisia monosperma Delile, Origanum dayi Post, Urtica membranacea Poir. ex Savigny, Krameria lappacea (Dombey) Burdet & B.B. Simpson and metabolites extracted from microbes such as Deinococcus radiodurans and Streptomycetes strains as well as probiotics like Bacillus coagulans and Lactobacillus brevis MK05 have exhibited antitumor effects in the form of antiproliferative and cytotoxic activity, increase in tumors' chemosensitivity, antioxidant activity and modulation of BC - associated molecular pathways. Further, bioactive compounds like 3,3'-diindolylmethane, epigallocatechin gallate, genistein, rutin, resveratrol, lycopene, sulforaphane, silibinin, rosmarinic acid, and shikonin are of special interest for the researchers and clinicians because these natural agents have multimodal action and act via multiple ways in managing the BC and most of these agents are regularly available in our food and fruit diets. Evidence from clinical trials suggests that such products had major potential in enhancing the effectiveness of conventional antitumor agents and decreasing their side effects. We here provide a comprehensive review of the therapeutic effects and mechanistic underpinnings of medicinal plants and microbial metabolites in BC management. The future perspectives on the translation of these findings to the personalized treatment of BC are provided and discussed.

Indole-3-Carbinol: Occurrence, Health-Beneficial Properties, and Cellular/Molecular Mechanisms

Indole-3-carbinol (I3C) is a bioactive phytochemical abundant in cruciferous vegetables. One of its main in vivo metabolites is 3,3'-diindolylmethane (DIM), formed by the condensation of two molecules of I3C. Both I3C and DIM alter multiple signaling pathways and related molecules controlling diverse cellular events, including oxidation, inflammation, proliferation, differentiation, apoptosis, angiogenesis, and immunity. There is a growing body of evidence from both in vitro and in vivo models that these compounds possess strong potential to prevent several forms of chronic disease such as inflammation, obesity, diabetes, cardiovascular disease, cancer, hypertension, neurodegenerative diseases, and osteoporosis. This article reviews current knowledge of the occurrence of I3C in nature and foods, along with the beneficial effects of I3C and DIM concerning prevention and treatment of human chronic diseases, focusing on preclinical studies and their mechanisms of action at cellular and molecular levels.

Dietary Diindolylmethane Enhances the Therapeutic Effect of Centchroman in Breast Cancer by Inhibiting Neoangiogenesis

Tumor angiogenesis is primarily regulated by vascular endothelial growth factor and its receptor (VEGF-VEGFR) communication, which is involved in cancer cell growth, progression, and metastasis. Diindolylmethane (DIM), a dietary bioactive from cruciferous vegetables, has been extensively studied in preclinical models for breast cancer prevention and treatment. Nevertheless, the possible role of DIM in the angiogenesis and metastasis regulations in triple-negative breast cancer (TNBC) remains elusive. Here, we investigated the potential anti-angiogenic and anti-metastatic role of DIM in combination with centchroman (CC). We observed that the oral administration of the DIM and CC combination suppressed primary tumor growth and tumor-associated vascularization in 4T1 tumors. Further, the DIM and CC combination exhibited a strong inhibitory effect on VEGF-induced angiogenesis in matrigel plugs. The mechanistic study demonstrated that DIM and CC could effectively downregulate VEGFA expression in tumor tissue and strongly interact with VEGFR2 to block its kinase activity. Interestingly, the DIM and CC combination also suppressed the lung metastasis of the highly metastatic 4T1 tumors through the downregulation of FAK/MMP9/2 signaling and reversal of epithelial-to-mesenchymal transition (EMT). Overall, these findings suggest that DIM-based nutraceuticals and functional foods can be developed as adjuvant therapy for treating TNBC.

F1Fo adenosine triphosphate (ATP) synthase is a potential drug target in non-communicable diseases

F₁F_o adenosine triphosphate (ATP) synthase, also known as the complex V, is the central ATP-producing unit in the cells arranged in the mitochondrial and plasma membranes. F₁F_o ATP synthase also regulates the central metabolic processes in the human body driven by proton motive force (Δp). Numerous studies have immensely contributed toward highlighting its regulation in improving energy homeostasis and maintaining mitochondrial integrity, which otherwise gets compromised in illnesses. Yet, its role in the implication of non-communicable diseases remains unknown. F₁F_o ATP synthase dysregulation at gene level leads to reduced activity and delocalization in the cristae and plasma membranes, which is directly associated with non-communicable diseases: cardiovascular diseases, diabetes, neurodegenerative disorders, cancer, and renal diseases. Individual subunits of the F₁F_o ATP synthase target ligand-based competitive or non-competitive inhibition. After performing a systematic literature review to understand its specific functions and its novel drug targets, the present article focuses on the central role of F₁F_o ATP synthase in primary non-communicable diseases. Next, it discusses its involvement through various pathways and the effects of multiple inhibitors, activators, and modulators specific to non-communicable diseases with a futuristic outlook.

Diindolylmethane Promotes Metabolic Crisis and Enhances the Efficacy of Centchroman in Breast Cancer: A 1H NMR-Based Approach

Diindolylmethane (DIM) is a key metabolite of indole-3-carbinol found in cruciferous vegetables such as broccoli, cauliflower, and cabbage. DIM has been known for its anti-cancerous activity through various mechanisms. Most cancer cells, including triple-negative breast cancer (TNBC), adapt distinct metabolic reprogramming for rapid growth and proliferation. Hence, targeting metabolic dysregulation may provide a favorable therapeutic condition for the treatment of TNBC. Earlier, we found that DIM increases the intracellular accumulation of Centchroman (CC), a potential anticancer agent, thereby enhancing the therapeutic potential of CC against breast cancer. However, the role of DIM in regulating TNBC cellular metabolism remains unknown. In the current study, we investigated the potential therapeutic interventions of DIM in TNBC and its metabolic reprogramming in enhancing the efficacy of CC. We found that DIM induced metabolic catastrophe in TNBC cells by regulating aerobic glycolysis and intermediate metabolism. Further, the DIM and CC combination significantly inhibited the TNBC tumor growth in the 4T1-syngeneic model. The inhibition of tumor growth was associated with the downregulation of key aerobic glycolysis mediators such as PKM2, GLUT1, and hypoxia-inducible factor 1α (HIF-1α). This is a first-of-a-kind investigation linking DIM with aerobic glycolysis regulation and enhancing the treatment efficacy of CC against TNBC. Therefore, these findings suggest that DIM-based nutraceuticals and functional foods can be developed as adjuvant therapy for treating metabolically dysregulated TNBC.

Therapy-induced modulation of extracellular vesicles in hepatocellular carcinoma

Despite rapid development of anti-tumorigenic treatments, the clinical outcome for hepatocellular carcinoma (HCC) is still far from satisfactory. With a deeper understanding about tumor microenvironment (TME), the critical role of extracellular vesicles (EVs) as intercellular liaison has come into spotlight. The dynamic functionality of these nanoparticles revealed cancer cells can employ both tumor and non-tumorous components for their own benefit, so as to mediate cell-to-cell communication and interchange of oncogenic biomolecules. Increasing studies on HCC-derived EVs have identified various irregulated biomolecules, that may serve as biomarkers or therapeutic targets. In this review, we first introduce the current knowledge about EVs and how they operate to maintain a healthy liver microenvironment. We then summarize some of the aberrant observations reported on HCC-derived EVs and how they contribute to HCC pathogenesis. Finally, we describe how current treatments for HCC alter behavior of EVs, which may shed light for potential prognostic markers and therapeutic strategies.

Targeting HIF-1α by Natural and Synthetic Compounds: A Promising Approach for Anti-Cancer Therapeutics Development

Advancement in novel target detection using improved molecular cancer biology has opened up new avenues for promising anti-cancer drug development. In the past two decades, the mechanism of tumor hypoxia has become more understandable with the discovery of hypoxia-inducible factor-1α (HIF-1α). It is a major transcriptional regulator that coordinates the activity of various transcription factors and their downstream molecules involved in tumorigenesis. HIF-1α not only plays a crucial role in the adaptation of tumor cells to hypoxia but also regulates different biological processes, including cell proliferation, survival, cellular metabolism, angiogenesis, metastasis, cancer stem cell maintenance, and propagation. Therefore, HIF-1α overexpression is strongly associated with poor prognosis in patients with different solid cancers. Hence, pharmacological targeting of HIF-1α has been considered to be a novel cancer therapeutic strategy in recent years. In this review, we provide brief descriptions of natural and synthetic compounds as HIF-1α inhibitors that have the potential to accelerate anticancer drug discovery. This review also introduces the mode of action of these compounds for a better understanding of the chemical leads, which could be useful as cancer therapeutics in the future.

3,3′-Diindolylmethane Enhances Fluorouracil Sensitivity via Inhibition of Pyrimidine Metabolism in Colorectal Cancer

Chemoresistance limits treatment outcomes in colorectal cancer (CRC) patients. A dimeric metabolite of indole-3-carbinol, 3,3′-diindolylmethane (DIM) is abundant in cruciferous vegetables and has shown anticancer efficacy. The role of DIM in regulating chemosensitivity in CRC remains unknown. In this study, we demonstrated that DIM treatment inhibits the malignant progression of CRC. RNA sequencing indicated that pyrimidine synthesis genes are attenuated by DIM treatment. Stable 1³C-labeled glucose tracing revealed that DIM inhibits de novo pyrimidine biosynthesis in CRC. DIM increases 5-FU cytotoxicity in CRC via regulation of the expression of pyrimidine metabolism-related genes. DIM synergizes with 5-FU to enhance its inhibitory effects on CRC both in vivo and in vitro. Our results suggest that DIM improves the therapeutic outcomes of FU-based chemotherapy in CRCs by inhibiting pyrimidine metabolism, identifying a new strategy for clinical therapy.

Treatment with the Prolyl Hydroxylase Inhibitor JNJ Promotes Abdominal Aortic Aneurysm Progression in Diabetic Mice

OBJECTIVE

Prolyl hydroxylase domain containing proteins (PHD) rigorously regulate intracellular hypoxia inducible factor-1 (HIF-1) protein expression and activity. Diabetes impairs PHD activity and attenuates abdominal aortic aneurysm (AAA) progression. The extent to which dysregulated PHD activity contributes to diabetes mediated AAA suppression remains undetermined.

METHODS

AAAs were induced in diabetic and non-diabetic male C57BL/6J mice via intra-aortic elastase infusion. A PHD inhibitor (JNJ-42041935, aka "JNJ", 150 mmol/kg) or vehicle alone was administered daily starting one day prior to AAA induction for 14 days. Influences on AAA progression was assessed via ultrasonography and histopathology. Expression of aortic HIF-1α, three of its target genes and macrophage derived mediators were assayed via quantitative reverse transcription polymerase chain reaction. Aneurysmal sections from AAA patients with and without diabetes (two patients in each group) were immunostained for HIF-1α and vascular endothelial growth factor (VEGF)-A.

RESULTS

Expression of HIF-1α target genes (erythropoietin, VEGF-A, and glucose transporter-1) was reduced by 45% - 95% in experimental diabetic aortas. Diameter enlargement was similarly limited, as were mural elastin degradation, leukocyte infiltration, and neo-angiogenesis (reduced capillary density and length) on histopathology. Pre-treatment with JNJ prior to AAA initiation augmented aortic HIF-1α target gene expression and aneurysm progression in diabetic mice, along with macrophage VEGF-A and matrix metalloproteinase 2 mRNA expression. No differences were noted in HIF-1α or VEGF-A expression on aortic immunohistochemical staining of human aortic tissue as a function of diabetes status.

CONCLUSION

Small molecule PHD inhibitor treatment reduces or offsets impairment of experimental AAA progression in hyperglycemic mice, highlighting the potential contribution of dysregulated PHD activity to diabetes mediated aneurysm suppression.

HIF-α Prolyl Hydroxylase Inhibitors and Their Implications for Biomedicine: A Comprehensive Review

Oxygen is essential for the maintenance of the body. Living organisms have evolved systems to secure an oxygen environment to be proper. Hypoxia-inducible factor (HIF) plays an essential role in this process; it is a transcription factor that mediates erythropoietin (EPO) induction at the transcriptional level under hypoxic environment. After successful cDNA cloning in 1995, a line of studies were conducted for elucidating the molecular mechanism of HIF activation in response to hypoxia. In 2001, cDNA cloning of dioxygenases acting on prolines and asparagine residues, which play essential roles in this process, was reported. HIF-prolyl hydroxylases (PHs) are molecules that constitute the core molecular mechanism of detecting a decrease in the partial pressure of oxygen, or hypoxia, in the cells; they can be called oxygen sensors. In this review, I discuss the process of molecular cloning of HIF and HIF-PH, which explains hypoxia-induced EPO expression; the development of HIF-PH inhibitors that artificially or exogenously activate HIF by inhibiting HIF-PH; and the significance and implications of medical intervention using HIF-PH inhibitors.

An intimate crosstalk between iron homeostasis and oxygen metabolism regulated by the hypoxia-inducible factors (HIFs)

Oxygen and iron are among the most abundant elements and have significant roles in human biology. Iron is essential for oxygen transport and is a component of molecular O₂-carrying proteins, such as hemoglobin and myoglobin. Iron is also a constituent of redox enzymes and can occupy multiple oxidation states. An elaborate system has evolved to stringently regulate the concentrations of both, free iron and oxygen, in various sites of the body. The final destination for iron and oxygen in the cells is the mitochondria. The mitochondria require substantial amounts of iron for heme synthesis and maturation of iron-sulfur clusters, and oxygen, as the electron acceptor in oxidative phosphorylation. Therefore, the balance between the control of iron availability and the physiology of hypoxic responses is critical for maintaining cell homeostasis. Several lines of study have clearly demonstrated that the transcription factors, hypoxia-inducible factors (HIFs), play a central role in cellular adaptation to critically low oxygen levels in both normal and compromised tissues. It has also been shown that several target genes of HIFs are involved in iron homeostasis, reflecting the molecular links between oxygen homeostasis and iron metabolism. Furthermore, HIF activation is modulated by intracellular iron, through regulation of hydroxylase activity, which requires iron as a cofactor. In addition, HIF-2α translation is controlled by iron regulatory protein (IRP) activity, providing another level of interdependence between iron and oxygen homeostasis.

Emerging evidence of the molecular landscape specific for hematogenous metastasis from gastric cancer

Gastric cancer (GC) is one of the most frequently diagnosed cancers in the world. Most GC patients are diagnosed when the cancer is in an advanced stage, and consequently, some develop metastatic lesions that generally cause cancer-related death. Metastasis establishment is affected by various conditions, such as tumor location, hemodynamics and organotropism. While digestive cancers may share a primary site, certain cases develop hematogenous metastasis with the absence of peritoneal metastasis, and vice versa. Numerous studies have revealed the clinicopathological risk factors for hematogenous metastasis from GC, such as vascular invasion, advanced age, differentiation, Borrmann type 1 or 2 and expansive growth. Recently, molecular mechanisms that contribute to metastatic site determination have been elucidated by advanced molecular biological techniques. Investigating the molecules that specifically participate in metastasis establishment in distinct secondary organs will lead to the development of novel biomarkers for patient stratification according to their metastatic risk and strategies for preventing and treating distinct metastases. We reviewed articles related to the molecular landscape of hematogenous metastasis from GC.

Natural Products for the Management and Prevention of Breast Cancer

Among all types of cancer, breast cancer is one of the most challenging diseases, which is responsible for a large number of cancer related deaths. Hormonal therapy, surgery, chemotherapy, and radiotherapy have been used as treatment of breast cancer, for a very long time. Due to severe side effects and multidrug resistance, these treatment approaches become increasingly ineffective. However, adoption of complementary treatment approach can be a big solution for this situation, as it is evident that compounds derived from natural source have a great deal of anticancer activity. Natural compounds can fight against aggressiveness of breast cancer, inhibit cancerous cell proliferation, and modulate cancer related pathways. A large number of research works are now focusing on the natural and dietary compounds and trying to find out new and more effective treatment strategies for the breast cancer patients. In this review, we discussed some significant natural chemical compounds with their mechanisms of actions, which can be very effective against the breast cancer and can be more potent by their proper modifications and further clinical research. Future research focusing on the natural anti-breast-cancer agents can open a new horizon in breast cancer treatment, which will play a great role in enhancing the survival rate of breast cancer patients.

Chemopreventive properties of 3,3'-diindolylmethane in breast cancer: evidence from experimental and human studies

Diet is a modifiable factor associated with the risk of several cancers, with convincing evidence showing a link between diet and breast cancer. The role of bioactive compounds of food origin, including those found in cruciferous vegetables, is an active area of research in cancer chemoprevention. This review focuses on 3,3'-diindolylmethane (DIM), the major bioactive indole in crucifers. Research of the cancer-preventive activity of DIM has yielded basic mechanistic, animal, and human trial data. Further, this body of evidence is largely supported by observational studies. Bioactive DIM has demonstrated chemopreventive activity in all stages of breast cancer carcinogenesis. This review describes current evidence related to the metabolism and mechanisms of DIM involved in the prevention of breast cancer. Importantly, this review also focuses on current evidence from human observational and intervention trials that have contributed to a greater understanding of exposure estimates that will inform recommendations for DIM intake.

3,3'-Diindolylmethane (DIM) and its ring-substituted halogenated analogs (ring-DIMs) induce differential mechanisms of survival and death in androgen-dependent and -independent prostate cancer cells

We recently reported that novel ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) induce apoptosis and necrosis in androgen-dependent and -independent prostate cancer cells. In this paper, we have focused on the mechanism(s) associated with ring-DIM-mediated cell death, and on identifying the specific intracellular target(s) of these compounds. The 4,4'- and 7,7'-dichloroDIMs and 4,4'- and 7,7'-dibromoDIMs induced the death of LNCaP, C42B and DU145 prostate cancer cells, but not that of immortalized normal human prostate epithelial (RWPE-1) cells. Ring-DIMs caused the early loss of mitochondrial membrane potential (MMP) and decreased mitochondrial ATP generation in prostate cancer cells. Cyclosporin A, an inhibitor of the mitochondrial permeability transition pore, inhibited ring-DIM-mediated cell death, and salubrinal, an inhibitor of ER stress, inhibited cell death mediated only by 4,4'-dihaloDIMs. We found that although salubrinal did not inhibit the onset of ER stress, it prevented 4,4'-dibromoDIM mediated loss of MMP. Salubrinal potentiated cell death in response to 7,7'-dihaloDIMs and DIM, and this effect concurred with increased loss of MMP. Using in silico 3-D docking affinity analysis, we identified Ca2+/calmodulin-dependent kinase II (CaMKII) as a potential direct target for the most toxic ring-DIM, 4,4'-dibromoDIM. An inhibitor of CaMKII, KN93, but not its inactive analog KN92, abrogated cell death mediated by 4,4'-dibromoDIM. The ring-DIMs induced ER stress and autophagy, but these processes were not necessary for ring-DIM-mediated cell death. Inhibition of autophagy with bafilomycin A1, 3-methyladenine or by LC3B gene silencing sensitized LNCaP and C42B, but not ATG5-deficient DU145 cells to ring-DIM- and DIM-mediated cell death. We propose that autophagy induced by the ring-DIMs and DIM has a cytoprotective function in prostate cancer cells.

Adaptive cellular stress pathways as therapeutic targets of dietary phytochemicals: focus on the nervous system

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phytochemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examplesof such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-κB, hypoxia-inducible factor 1α, peroxisome proliferator-activated receptor γ, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Translational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.

Prolyl hydroxylase domain enzymes: important regulators of cancer metabolism

The hypoxia-inducible factor (HIF) prolyl hydroxylase domain enzymes (PHDs) regulate the stability of HIF protein by post-translational hydroxylation of two conserved prolyl residues in its α subunit in an oxygen-dependent manner. Trans-4-prolyl hydroxylation of HIFα under normal oxygen (O₂) availability enables its association with the von Hippel-Lindau (VHL) tumor suppressor pVHL E3 ligase complex, leading to the degradation of HIFα via the ubiquitin-proteasome pathway. Due to the obligatory requirement of molecular O₂ as a co-substrate, the activity of PHDs is inhibited under hypoxic conditions, resulting in stabilized HIFα, which dimerizes with HIFβ and, together with transcriptional co-activators CBP/p300, activates the transcription of its target genes. As a key molecular regulator of adaptive response to hypoxia, HIF plays important roles in multiple cellular processes and its overexpression has been detected in various cancers. The HIF1α isoform in particular has a strong impact on cellular metabolism, most notably by promoting anaerobic, whilst inhibiting O₂-dependent, metabolism of glucose. The PHD enzymes also seem to have HIF-independent functions and are subject to regulation by factors other than O₂, such as by metabolic status, oxidative stress, and abnormal levels of endogenous metabolites (oncometabolites) that have been observed in some types of cancers. In this review, we aim to summarize current understandings of the function and regulation of PHDs in cancer with an emphasis on their roles in metabolism.

Molecular mechanisms of action and therapeutic uses of pharmacological inhibitors of HIF-prolyl 4-hydroxylases for treatment of ischemic diseases

SIGNIFICANCE

In this review, we have discussed the efficacy and effect of small molecules that act as prolyl hydroxylase domain inhibitors (PHDIs). The use of these compounds causes upregulation of the pro-angiogenic factors and hypoxia inducible factor-1α and -2α (HIF-1α and HIF-2α) to enhance angiogenic, glycolytic, erythropoietic, and anti-apoptotic pathways in the treatment of various ischemic diseases responsible for significant morbidity and mortality in humans.

RECENT ADVANCES

Sprouting of new blood vessels from the existing vasculature and surgical intervention, such as coronary bypass and stent insertion, have been shown to be effective in attenuating ischemia. However, the initial reentry of oxygen leads to the formation of reactive oxygen species that cause oxidative stress and result in ischemia/reperfusion (IR) injury. This apparent "oxygen paradox" must be resolved to combat IR injury. During hypoxia, decreased activity of PHDs initiates the accumulation and activation of HIF-1α, wherein the modulation of both PHD and HIF-1α appears as promising therapeutic targets for the pharmacological treatment of ischemic diseases.

CRITICAL ISSUES

Research on PHDs and HIFs has shown that these molecules can serve as therapeutic targets for ischemic diseases by modulating glycolysis, erythropoiesis, apoptosis, and angiogenesis. Efforts are underway to identify and synthesize safer small-molecule inhibitors of PHDs that can be administered in vivo as therapy against ischemic diseases.

FUTURE DIRECTIONS

This review presents a comprehensive and current account of the existing small-molecule PHDIs and their use in the treatment of ischemic diseases with a focus on the molecular mechanisms of therapeutic action in animal models.

Theranostic tumor homing nanocarriers for the treatment of lung cancer

The drugs/strategies to selectively inhibit tumor blood supply have generated interest in recent years for enhancement of cancer therapeutics. The objective of this study was to formulate tumor homing PEGylated CREKA peptide conjugated theranostic nanoparticles of DIM-C-pPhC6H5 (DIM-P) and investigate in vivo antitumor activity as well as evaluate the targeted efficiency to lung tumors using imaging techniques. DIM-P loaded Nanoparticles (NCs-D) were prepared using lipids, and DOGS-NTA-Ni and the surface of NCs-D were modified with PEGylated CREKA peptide (PCNCs-D). PCNCs-D showed 3 fold higher binding to clotted plasma proteins in tumor vasculature compared to NCs-D. PCNCs-D showed 26%±4% and 22%±5% increase in tumor reduction compared to NCs-D in metastatic and orthotopic models respectively. In-vivo imaging studies showed ~40 folds higher migration of PCNCs-Di in tumor vasculature than NCs-Di. Our studies demonstrate the role of PCNCs-D as theranostic tumor homing drug delivery and imaging systems for lung cancer diagnosis and treatment.

FROM THE CLINICAL EDITOR

This study demonstrates a very efficient delivery system to address lung cancer growth through blood supply inhibition.

Magnolol suppresses hypoxia-induced angiogenesis via inhibition of HIF-1α/VEGF signaling pathway in human bladder cancer cells

The hypoxic environment in tumors is an important factor causing tumor angiogenesis by activating the key transcription factor, hypoxia-inducible factors-1α (HIF-1α). Magnolol isolated from Magnolia officinalis has been reported to exhibit an anticancer activity via elevation of apoptosis. However, whether magnolol inhibits tumor angiogenesis remains unknown. In the present study, we demonstrated that magnolol significantly inhibited angiogenesis in vitro and in vivo evidenced by the attenuation of hypoxia and vascular endothelial growth factor (VEGF)-induced tube formation of human umbilical vascular endothelial cells, vasculature generation in chicken chorioallantoic membrane and Matrigel plug. In hypoxic human bladder cancer cells (T24), treatment with magnolol inhibited hypoxia-stimulated H2O2 formation, HIF-1α induction including mRNA, protein expression, and transcriptional activity as well as VEGF secretion. Additionally, the enhanced degradation of HIF-1α protein via enhancing prolyl hydroxylase activity and the decreased newly-synthesized HIF-1α protein in hypoxic T24 cells may involve the reduction of HIF-1α protein accumulation by magnolol. Interestingly, magnolol also acts as a VEGFR2 antagonist, and subsequently attenuates the down-stream AKT/mTOR/p70S6K/4E-BP-1 kinase activation both in hypoxic T24 cells and tumor tissues. As expected, administration of magnolol greatly attenuated tumor growth, angiogenesis and the protein expression of HIF-1α, VEGF, CD31, a marker of endothelial cells, and carbonic anhydrase IX, an endogenous marker for hypoxia, in the T24 xenograft mouse model. Collectively, these findings strongly indicate that the anti-agngiogenic activity of magnolol is, at least in part, mediated by suppressing HIF-1α/VEGF-dependent pathways, and suggest that magnolol may be a potential drug for human bladder cancer therapy.

The biological kinship of hypoxia with CSC and EMT and their relationship with deregulated expression of miRNAs and tumor aggressiveness

Hypoxia is one of the fundamental biological phenomena that are intricately associated with the development and aggressiveness of a variety of solid tumors. Hypoxia-inducible factors (HIF) function as a master transcription factor, which regulates hypoxia responsive genes and has been recognized to play critical roles in tumor invasion, metastasis, and chemo-radiation resistance, and contributes to increased cell proliferation, survival, angiogenesis and metastasis. Therefore, tumor hypoxia with deregulated expression of HIF and its biological consequence lead to poor prognosis of patients diagnosed with solid tumors, resulting in higher mortality, suggesting that understanding of the molecular relationship of hypoxia with other cellular features of tumor aggressiveness would be invaluable for developing newer targeted therapy for solid tumors. It has been well recognized that cancer stem cells (CSCs) and epithelial-to-mesenchymal transition (EMT) phenotypic cells are associated with therapeutic resistance and contribute to aggressive tumor growth, invasion, metastasis and believed to be the cause of tumor recurrence. Interestingly, hypoxia and HIF signaling pathway are known to play an important role in the regulation and sustenance of CSCs and EMT phenotype. However, the molecular relationship between HIF signaling pathway with the biology of CSCs and EMT remains unclear although NF-κB, PI3K/Akt/mTOR, Notch, Wnt/β-catenin, and Hedgehog signaling pathways have been recognized as important regulators of CSCs and EMT. In this article, we will discuss the state of our knowledge on the role of HIF-hypoxia signaling pathway and its kinship with CSCs and EMT within the tumor microenvironment. We will also discuss the potential role of hypoxia-induced microRNAs (miRNAs) in tumor development and aggressiveness, and finally discuss the potential effects of nutraceuticals on the biology of CSCs and EMT in the context of tumor hypoxia.

Oxygen versus Reactive Oxygen in the Regulation of HIF-1α: The Balance Tips

Hypoxia inducible factor (HIF) is known as the master regulator of the cellular response to hypoxia and is of pivotal importance during development as well as in human disease, particularly in cancer. It is composed of a constitutively expressed β subunit (HIF-1β) and an oxygen-regulated α subunit (HIF-1α and HIF-2α), whose stability is tightly controlled by a family of oxygen- and iron-dependent prolyl hydroxylase enzymes. Whether or not mitochondria-derived reactive oxygen species (ROS) are involved in the regulation of Hypoxia Inducible Factor-1α has been a matter of contention for the last 10 years, with equally compelling evidence in favor and against their contribution. A number of recent papers appear to tip the balance against a role for ROS. Thus, it has been demonstrated that HIF prolyl hydroxylases are unlikely to be physiological targets of ROS and that the increase in ROS that is associated with downregulation of Thioredoxin Reductase in hypoxia does not affect HIF-1α stabilization. Finally, the protein CHCHD4, which modulates cellular HIF-1α concentrations by promoting mitochondrial electron transport chain activity, has been proposed to exert its regulatory effect by affecting cellular oxygen availability. These reports are consistent with the hypothesis that mitochondria play a critical role in the regulation of HIF-1α by controlling intracellular oxygen concentrations.

Attenuation of multi-targeted proliferation-linked signaling by 3,3'-diindolylmethane (DIM): from bench to clinic

Emerging evidence provide credible support in favor of the potential role of bioactive products derived from ingesting cruciferous vegetables such as broccoli, brussel sprouts, cauliflower and cabbage. Among many compounds, 3,3'-diindolylmethane (DIM) is generated in the acidic environment of the stomach following dimerization of indole-3-carbinol (I3C) monomers present in these classes of vegetables. Both I3C and DIM have been investigated for their use in preventing, inhibiting, and reversing the progression of cancer - as a chemopreventive agent. In this review, we summarize an updated, wide-ranging pleiotropic anti-tumor and biological effects elicited by DIM against tumor cells. It is unfeasible to point one single target as basis of cellular target of action of DIM. We emphasize key cellular and molecular events that are effectively modulated in the direction of inducing apoptosis and suppressing cell proliferation. Collectively, DIM orchestrates signaling through Ah receptor, NF-κB/Wnt/Akt/mTOR pathways impinging on cell cycle arrest, modulation of key cytochrome P450 enzymes, altering angiogenesis, invasion, metastasis and epigenetic behavior of cancer cells. The ability of DIM to selectively induce tumor cells to undergo apoptosis has been observed in preclinical models, and thus it has been speculated in improving the therapeutic efficacy of other anticancer agents that have diverse molecular targets. Consequently, DIM has moved through preclinical development into Phase I clinical trials, thereby suggesting that DIM could be a promising and novel agent either alone or as an adjunct to conventional therapeutics such as chemo-radio and targeted therapies. An important development has been the availability of DIM formulation with superior bioavailability for humans. Therefore, DIM appears to be a promising chemopreventive agent or chemo-radio-sensitizer for the prevention of tumor recurrence and/or for the treatment of human malignancies.

Cruciferous vegetables in cancer prevention

Epidemiological studies have reported a strong inverse correlation between the intake of cruciferous vegetables and the cancer risk. This association has been found stronger than the association between cancer risk and fruit and vegetable intake in general. Cruciferous vegetables are unique in that they are rich sources of glucosinolates. Hydrolytic degradation of glucosinolates results in the formation of biologically active compounds, including indoles (such as I3C - indole-3-carbinol, DIM - diindolylmethane, indole phytoalexins) and isothiocyanates (such as PEITC - phenethyl isothiocyanate, SFN - sulforaphane). Some mechanisms, like effect on biotransformation system, induction of cell cycle arrest and apoptosis, and antiangiogenic effect, by which cruciferous vegetables act as chemopreventive agents have been described. Beneficial modulation of oestrogen metabolism with reduced risk of breast and cervical cancer after DIM and I3C supplementation was noted. Despite all health benefit expectation, some studies found that I3C actually promoted or enhanced the development of cancer when administered chronically after the carcinogen (post initiation) to rats. Because the long-term effects of the supplementation of the mentioned compounds on cancer risk in humans are not known, the widespread use of dietary supplements containing natural compounds in humans should be avoided until the potential risks versus benefits are better understood.

Signaling mechanism(s) of reactive oxygen species in Epithelial-Mesenchymal Transition reminiscent of cancer stem cells in tumor progression

Reactive oxygen species (ROS) are known to serve as a second messenger in the intracellular signal transduction pathway for a variety of cellular processes, including inflammation, cell cycle progression, apoptosis, aging and cancer. Recently, ROS have been found to be associated with tumor metastasis involving the processes of tumor cell migration, invasion and angiogenesis. Emerging evidence also suggests that Epithelial-Mesenchymal Transition (EMT), a process that is reminiscent of cancer stem cells, is an important step toward tumor invasion and metastasis, and intimately involved in de novo and acquired drug resistance. In light of recent advances, we are summarizing the role of ROS in EMT by cataloging how its deregulation is involved in EMT and tumor aggressiveness. Further attempts have been made to summarize the role of several chemopreventive agents that could be useful for targeted inactivation of ROS, suggesting that many natural agents could be useful for the reversal of EMT, which would become a novel approach for the prevention of tumor progression and/or treatment of human malignancies especially by killing EMT-type cells that shares similar characteristics with cancer stem cells.

beta2- but not beta1-adrenoceptor activation modulates intracellular oxygen availability

beta-Adrenoceptors (beta-ARs) play a critical role in the regulation of cardiovascular function. Intracellular oxygen homeostasis is crucial for the survival of cardiomyocytes. However, it is still unclear whether beta-AR activation can modulate intracellular oxygen. Here we used mitochondrial and cytosolic target Renilla luciferase to detect intracellular oxygen concentration. Pharmacological experiments revealed that beta2-AR activation specifically regulates intracellular oxygen in cardiomyocytes and COS7 cells. This effect was abrogated by inhibitory G protein (Gi) inhibition, endothelial nitric oxide synthase (eNOS) blockade, and NO scavenging, implicating that the beta2-AR-Gi-eNOS pathway is involved in this regulation. beta2-AR activation increased the AMP/ATP ratio, AMPK activity, ROS production and prolyl hydroxylase activity. These effects also contribute to the regulation of beta2-AR signalling, thus providing an additional layer of complexity to enforce the specificity of beta1-AR and beta2-AR signalling. Collectively, the study provides novel insight into the modulation of oxygen homeostasis, broadens the scope of beta2-AR function, and may have crucial implications for beta2-AR signalling regulation.

Bisphosphonates suppress insulin-like growth factor 1-induced angiogenesis via the HIF-1alpha/VEGF signaling pathways in human breast cancer cells

Adjunctive chemotherapy with bisphosphonates has been reported to delay bone metastasis and improve overall survival in breast cancer. Aside from its antiresorptive effect, bisphosphonates exhibit antitumor activities, in vitro and in vivo, via several mechanisms, including antiangiogenesis. In this study, we investigated the potential molecular mechanisms underlying the antiangiogenic effect of non-nitrogen-containing and nitrogen-containing bisphosphonates, clodronate and pamidronate, respectively, in insulin-like growth factor (IGF)-1 responsive human breast cancer cells. We tested whether bisphosphonates had any effects on hypoxia-inducible factor (HIF)-1alpha/vascular endothelial growth factor (VEGF) axis that plays a pivotal role in tumor angiogenesis, and our results showed that both pamidronate and clodronate significantly suppressed IGF-1-induced HIF-1alpha protein accumulation and VEGF expression in MCF-7 cells. Mechanistically, we found that either pamidronate or clodronate did not affect mRNA expression of HIF-1alpha, but they apparently promoted the degradation of IGF-1-induced HIF-1alpha protein. Meanwhile, we found that the presence of pamidronate and clodronate led to a dose-dependent decease in the newly-synthesized HIF-1alpha protein induced by IGF-1 in breast cancer cells after proteasomal inhibition, thus, indirectly reflecting the inhibition of protein synthesis. In addition, our results indicated that the inhibitory effects of bisphosphonates on the HIF-1alpha/VEGF axis are associated with the inhibition of the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin signaling pathways. Consistently, we demonstrated that pamidronate and clodronate functionally abrogated both in vitro and in vivo tumor angiogenesis induced by IGF-1-stimulated MCF-7 cells. These findings have highlighted an important mechanism of the pharmacological action of bisphosphonates in the inhibition of tumor angiogenesis in breast cancer cells.

Nitric oxide, cytochrome C oxidase, and the cellular response to hypoxia

Cytochrome c oxidase (CcO; complex IV of the mitochondrial electron transport chain) is the primary site of cellular oxygen consumption and, as such, is central to oxidative phosphorylation and the generation of adenosine-triphosphate. Nitric oxide (NO), an endogenously-generated gas, modulates the activity of CcO. Depending on the intracellular oxygen concentration and the resultant dominant redox state of CcO, the interaction between CcO and NO can have a range of signaling consequences for cells in the perception of changes in oxygen concentration and the initiation of adaptive responses. At higher oxygen concentrations, when CcO is predominantly in an oxidized state, it consumes NO. At lower oxygen concentrations, when CcO is predominantly reduced, NO is not consumed and accumulates in the microenvironment, with implications for both the respiratory rate of cells and the local vascular tone. Changes in the availability of intracellular oxygen and in the generation of reactive oxygen species that accompany these interactions result in cell signaling and in regulation of oxygen-sensitive pathways that ultimately determine the nature of the cellular response to hypoxia.

Increased expression of enolase alpha in human breast cancer confers tamoxifen resistance in human breast cancer cells

Enolase-alpha (ENO-1) is a key glycolytic enzyme that has been used as a diagnostic marker to identify human lung cancers. To investigate the role of ENO-1 in breast cancer diagnosis and therapy, the mRNA levels of ENO-1 in 244 tumor and normal paired tissue samples and 20 laser capture-microdissected cell clusters were examined by quantitative real-time PCR analysis. Increased ENO-1 mRNA expression was preferentially detected in estrogen receptor-positive (ER+) tumors (tumor/normal ratio >90-fold) when compared to ER-negative (tumor/normal ratio >20-fold) tumor tissues. The data presented here demonstrate that those patients whose tumors highly expressed ENO-1 had a poor prognosis with greater tumor size (>2 cm, *P = .017), poor nodal status (N > 3, *P = .018), and a shorter disease-free interval (<==1 year, *P < .009). We also found that higher-expressing ENO-1 tumors confer longer distance relapse (tumor/normal ratio = 82.8-92.4-fold) when compared to locoregional relapse (tumor/normal ratio = 43.4-fold) in postsurgical 4-hydroxy-tamoxifen (4-OHT)-treated ER+ patients (*P = .014). These data imply that changes in tumor ENO-1 levels are related to clinical 4-OHT therapeutic outcome. In vitro studies demonstrated that decreasing ENO-1 expression using small interfering RNA (siRNA) significantly augmented 4-OHT (100 nM)-induced cytotoxicity in tamoxifen-resistant (Tam-R) breast cancer cells. These results suggest that downregulation of ENO-1 could be utilized as a novel pharmacological approach for overcoming 4-OHT resistance in breast cancer therapy.

3,3'-Diindolylmethane induces a G(1) arrest in human prostate cancer cells irrespective of androgen receptor and p53 status

3,3'-Diindolylmethane (DIM) is a potential chemopreventive phytochemical derived from Brassica vegetables. In this study we characterized the effect of DIM on cell cycle regulation in both androgen-dependent LNCaP and androgen receptor negative p53 mutant DU145 human prostate cancer cells. DIM had an anti-proliferative effect on both LNCaP and DU145 cells, as it significantly inhibited [3H]-thymidine incorporation. FACS analysis revealed a DIM-mediated G(1) cell cycle arrest. DIM strongly inhibited the expression of cdk2 and cdk4 protein and increased the expression of the cell cycle inhibitor p27(Kip1) protein in LNCaP and DU145 cells. Promoter deletion studies with p27(Kip1) reporter gene constructs showed that this DIM-mediated increase in p27(Kip1) was dependent on the Sp1 transcription factor. Moreover, using a dominant negative inhibitor of p38 MAPK, we showed that the induction of p27(Kip1) and subsequent G(1) arrest by DIM involve activation of the p38 MAPK pathway in the DU145 cells. Taken together, our results indicate that DIM is able to stop the cell cycle progression of human prostate cancer cells regardless of their androgen-dependence and p53 status, by differentially modulating cell cycle regulatory pathways. The Sp1 and p38 MAPK pathways mediate the DIM cell cycle regulatory effect in DU145 cells.