Publications

Supplementary Figure Legends from PHGDH Expression Is Required for Mitochondrial Redox Homeostasis, Breast Cancer Stem Cell Maintenance, and Lung Metastasis

<p>Legends for Supplementary Figures S1-S6</p>

Insulin Stimulates Hypoxia-inducible Factor 1 through a Phosphatidylinositol 3-Kinase/Target of Rapamycin-dependent Signaling Pathway

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor involved in normal mammalian development and in the pathogenesis of several disease states. It consists of two subunits, HIF-1alpha, which is degraded during normoxia, and HIF-1beta, which is constitutively expressed. Activated HIF-1 induces the expression of genes involved in angiogenesis, erythropoiesis, and glucose metabolism. We have previously reported that insulin stimulates vascular endothelial growth factor (VEGF) expression (). In this study, we show that insulin activates HIF-1, leading to VEGF expression in retinal epithelial cells. Insulin activates HIF-1alpha protein expression in a dose-dependent manner with a maximum reached within 6 h. The expression of HIF-1alpha is correlated with the activation of HIF-1 DNA binding activity and the transactivation of a HIF-1-dependent reporter gene. Insulin does not appear to affect HIF-1alpha mRNA transcription but regulates HIF-1alpha protein expression through a translation-dependent pathway. The expression of an active form of protein kinase B and treatment of cells with specific inhibitors of phosphatidylinositol 3-kinase (PI3K), MAPK, and target of rapamycin (TOR) show that mainly PI3K and to a lesser extent TOR are required for insulin-induced HIF-1alpha expression. HIF-1 activity and VEGF expression are also dependent on PI3K- and TOR-dependent signaling. In conclusion, we show here that insulin regulates HIF-1 action through a PI3K/TOR-dependent pathway, resulting in increased VEGF expression.

Differentiation Stage-Specific Requirement in Hypoxia-Inducible Factor-1α–Regulated Glycolytic Pathway during Murine B Cell Development in Bone Marrow

Abstract Hypoxia-inducible factor (HIF)-1α plays a central role in oxygen homeostasis and energy supply by glycolysis in many cell types. We previously reported that an HIF-1α gene deficiency caused abnormal B cell development and autoimmunity. In this study we show that HIF-1α–enabled glycolysis during B cell development is required in a developmental stage-specific manner. Supporting this conclusion are observations that the glycolytic pathway in HIF-1α–deficient B220+ bone marrow cells is much less functionally effective than in wild-type control cells. The expression of genes encoding the glucose transporters and the key glycolytic enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bishosphatase 3, was greatly reduced in HIF-1α–deficient cells. The compensatory adaptation to the defect of glycolysis was reflected in higher levels of expression of respiratory chain-related genes and TCA cycle-related genes in HIF-1α–deficient cells than in wild-type cells. In agreement with these findings, HIF-1α–deficient cells used pyruvate more efficiently than wild-type cells. The key role of HIF-1α–enabled glycolysis in bone marrow B cells was also demonstrated by glucose deprivation during in vitro bone marrow cell culture and by using a glycolysis inhibitor in the bone marrow cell culture. Taken together, these findings indicate that glucose dependency differs at different B cell developmental stages and that HIF-1α plays an important role in B cell development.

<i>Trans</i> -Acting Factors

Abstract Transcription factors are trans-acting proteins that affect the rate of transcription by specific interactions with DNA and/or other proteins (see Chapter 1). Transcriptional activators and repressors have positive and negative effects, respectively, on the rate of transcription. Transcriptional regulators may affect the rate of transcription initiation and/or mRNA elongation. In addition to DNA-binding activators and repressors, a variety of coactivators, corepressors, and other cofactors have been identified that do not bind to DNA directly but instead interact with the DNA-binding proteins and mediate their effects on transcription. Some of these co-factors have enzymatic activities that allow them to modify other cofactors, Pol II, or histones. Each of the transcription factor classes listed in Table 3.1 will be described in this chapter, followed by a discussion of pathways that transduce signals (e.g., cytokines, growth fac tors, and small molecules) at the cell surface to transcription factors that alter gene expression in the nucleus.

Correction: PHGDH Expression Is Required for Mitochondrial Redox Homeostasis, Breast Cancer Stem Cell Maintenance, and Lung Metastasis

Hypoxia-inducible factors promote breast cancer stem cell specification and maintenance in response to hypoxia or cytotoxic chemotherapy

Supplementary Fig. S1 from Hypoxia-induced resistance to anticancer drugs is associated with decreased senescence and requires hypoxia-inducible factor-1 activity

Supplementary Fig. S1 from Hypoxia-induced resistance to anticancer drugs is associated with decreased senescence and requires hypoxia-inducible factor-1 activity

Inhibition of lactate dehydrogenase A induces oxidative stress and inhibits tumor progression

As the result of genetic alterations and tumor hypoxia, many cancer cells avidly take up glucose and generate lactate through lactate dehydrogenase A (LDHA), which is encoded by a target gene of c-Myc and hypoxia-inducible factor (HIF-1). Previous studies with reduction of LDHA expression indicate that LDHA is involved in tumor initiation, but its role in tumor maintenance and progression has not been established. Furthermore, how reduction of LDHA expression by interference or antisense RNA inhibits tumorigenesis is not well understood. Here, we report that reduction of LDHA by siRNA or its inhibition by a small-molecule inhibitor (FX11 [3-dihydroxy-6-methyl-7-(phenylmethyl)-4-propylnaphthalene-1-carboxylic acid]) reduced ATP levels and induced significant oxidative stress and cell death that could be partially reversed by the antioxidant N -acetylcysteine. Furthermore, we document that FX11 inhibited the progression of sizable human lymphoma and pancreatic cancer xenografts. When used in combination with the NAD + synthesis inhibitor FK866, FX11 induced lymphoma regression. Hence, inhibition of LDHA with FX11 is an achievable and tolerable treatment for LDHA-dependent tumors. Our studies document a therapeutical approach to the Warburg effect and demonstrate that oxidative stress and metabolic phenotyping of cancers are critical aspects of cancer biology to consider for the therapeutical targeting of cancer energy metabolism.

HIF-1α, pimonidazole, and iododeoxyuridine to estimate hypoxia and perfusion in human head-and-neck tumors

Hypoxia-inducible factor 1: oxygen homeostasis and disease pathophysiology

HIF-1 regulates hypoxic induction of NHE1 expression and alkalinization of intracellular pH in pulmonary arterial myocytes

Vascular remodeling resulting from altered pulmonary arterial smooth muscle cell (PASMC) growth is a contributing factor to the pathogenesis of hypoxic pulmonary hypertension. PASMC growth requires an alkaline shift in intracellular pH (pH i ) and we previously showed that PASMCs isolated from mice exposed to chronic hypoxia exhibited increased Na + /H + exchanger (NHE) expression and activity, which resulted in increased pH i . However, the mechanism by which hypoxia caused these changes was unknown. In this study we tested the hypothesis that hypoxia-induced changes in PASMC pH homeostasis are mediated by the transcriptional regulator hypoxia-inducible factor 1 (HIF-1). Consistent with previous results, increased NHE isoform 1 (NHE1) mRNA and protein, enhanced NHE activity, and an alkaline shift in pH i were observed in PASMCs isolated from wild-type mice exposed to chronic hypoxia (3 wk at 10% O 2 ). In contrast, these changes were absent in PASMCs isolated from chronically hypoxic mice with partial deficiency for HIF-1. Exposure of PASMCs to hypoxia ex vivo (48 h at 4% O 2 ) or overexpression of HIF-1 in the absence of hypoxia also increased NHE1 mRNA and protein expression. Our results indicate that full expression of HIF-1 is essential for hypoxic induction of NHE1 expression and changes in PASMC pH homeostasis and suggest a novel mechanism by which HIF-1 mediates pulmonary vascular remodeling during the pathogenesis of hypoxic pulmonary hypertension.

Chronic cold exposure results in subcutaneous adipose tissue browning and altered global metabolism in Qinghai-Tibetan plateau pika (Ochotona curzoniae)

Four-and-a-Half LIM Domain Proteins Inhibit Transactivation by Hypoxia-inducible Factor 1

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that promotes angiogenesis, metabolic reprogramming, and other critical aspects of cancer biology. The four-and-a-half LIM domain (FHL) proteins are a family of LIM domain-only proteins implicated in transcriptional regulation and suppression of tumor growth. Here we describe functional interactions between the FHL proteins and HIF-1. FHL1-3 inhibit HIF-1 transcriptional activity and HIF-1α transactivation domain function by oxygen-independent mechanisms. FHL2 directly interacts with HIF-1α to repress transcriptional activity. FHL1 binds to the p300/CBP co-activators and disrupts binding with HIF-1α. FHL3 does not bind to HIF-1α or p300, indicating that it regulates transactivation by a novel molecular mechanism. Expression of the FHL proteins increased upon HIF-1α induction, suggesting the existence of a feedback loop. These results identify FHL proteins as negative regulators of HIF-1 activity, which may provide a mechanism by which they suppress tumor growth.

Data from Reciprocal Regulation of DUSP9 and DUSP16 Expression by HIF1 Controls ERK and p38 MAP Kinase Activity and Mediates Chemotherapy-Induced Breast Cancer Stem Cell Enrichment

&lt;div&gt;Abstract&lt;p&gt;Triple-negative breast cancer (TNBC) has a poor prognosis due to its aggressive characteristics and lack of targeted therapies. Cytotoxic chemotherapy may reduce tumor bulk, but leaves residual disease due to the persistence of chemotherapy-resistant breast cancer stem cells (BCSC), which are critical for tumor recurrence and metastasis. Here, we demonstrate that hypoxia-inducible factor (HIF)-1–dependent regulation of mitogen-activated protein kinase (MAPK) signaling pathways contributes to chemotherapy-induced BCSC enrichment. Chemotherapy increased DUSP9 expression and decreased DUSP16 expression in a HIF1–dependent manner, leading to inhibition of ERK and activation of p38 signaling pathways, respectively. Inhibition of ERK caused transcriptional induction of the pluripotency factor Nanog through decreased inactivating phosphorylation of FoxO3, while activation of p38 stabilized Nanog and Klf4 mRNA through increased inactivating phosphorylation of RNA-binding protein ZFP36L1, both of which promoted specification of the BCSC phenotype. Inhibition of HIF1 or p38 signaling blocked chemotherapy-induced pluripotency factor expression and BCSC enrichment. These surprising results delineate a mechanism by which a transcription factor switches cells from ERK to p38 signaling in response to chemotherapy and suggest that therapeutic targeting of HIF1 or the p38 pathway in combination with chemotherapy will block BCSC enrichment and improve outcome in TNBC.&lt;/p&gt;&lt;p&gt;&lt;b&gt;Significance:&lt;/b&gt; These findings provide a molecular mechanism that may account for the increased relapse rate of women with TNBC who are treated with cytotoxic chemotherapy and suggest that combining chemotherapy with an inhibitor of HIF1 or p38 activity may increase patient survival. &lt;i&gt;Cancer Res; 78(15); 4191–202. ©2018 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;

Hypoxia-Inducible Factor 1 and Cardiovascular Disease

Cardiac function is required for blood circulation and systemic oxygen delivery. However, the heart has intrinsic oxygen demands that must be met to maintain effective contractility. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that functions as a master regulator of oxygen homeostasis in all metazoan species. HIF-1 controls oxygen delivery, by regulating angiogenesis and vascular remodeling, and oxygen utilization, by regulating glucose metabolism and redox homeostasis. Analysis of animal models suggests that by activation of these homeostatic mechanisms, HIF-1 plays a critical protective role in the pathophysiology of ischemic heart disease and pressure-overload heart failure.

Data Supplement from Decreased Expression of Cystathionine β-Synthase Promotes Glioma Tumorigenesis

&lt;p&gt;Supplementary Figure Legends&lt;/p&gt;

Interpreting intratumoral hypoxia: Can it guide therapy?

The role of hypoxia as a key determinant of outcome for human cancers has encouraged efforts to noninvasively detect and localize regions of poor oxygenation in tumors. In this review, we will summarize existing and developing techniques for imaging tumoral hypoxia. A brief review of the biology of tumor oxygenation and its effect on tumor cells will be provided initially. We will then describe existing methods for measurement of tissue oxygenation status. An overview of emerging molecular imaging techniques based on radiolabeled hypoxic markers such as misonidazole or hypoxia-related genes and proteins will then be given, and the usefulness of these approaches toward targeting hypoxia directly will be assessed. Finally, we will evaluate the clinical potential of oxygen- and molecular-specific techniques for imaging hypoxia, and discuss how these methods will individually and collectively advance oncology.

Heat-acclimation-ischemia cross-tolerance: Does HIF-1α play a role?