Passing the baton: the HIF switch.
ABSTRACT Hypoxia is an inadequate oxygen supply to tissues and cells, which can restrict their function. The hypoxic response is primarily mediated by the hypoxia-inducible transcription factors, HIF-1 and HIF-2, which have both overlapping and unique target genes. HIF target gene activation is highly context specific and is not a reliable indicator of which HIF-α isoform is active. For example, in some cell lines, the individual HIFs have specific temporal and functional roles: HIF-1 drives the initial response to hypoxia (<24h) and HIF-2 drives the chronic response (>24h). Here, we review the significance of the HIF switch and the relation between HIF-1 and HIF-2 under both physiological and pathophysiological conditions.
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ABSTRACT: CONTENTS 1. Introduction 1 1.1. Brain tumor glioblastoma multiforme (GBM) 1 1.2. Cancer stem cell (CSC) paradigm 2 1.3. GBM stem-like cells (GSCs) 4 2. Isolation methodologies of GSCs 4 2.1. SP and ABC transporters 5 2.2. Isolation based on biomarkers 5 2.2.1. CD133 5 2.2.2. ALDH 5 2.2.3. Aptamers 5 3. Enrichment of GSC cultures 6 3.1. Effects of medium and substrates 6 3.2. Effects of hypoxia 7 3.3. Effects of endothelial cells 8 3.4. Effects of pericyte cells 9 3.5. Effects of immunosuppressed animals 9 4. Validation of the GSC phenotype 10 4.1. Sphere-formation assay 10 4.2. Tumor formation in vivo 10 4.3. Expression of biomarkers 11 4.4. Chemoresistance assay 11 4.5. Differentiation assay 12 5. Conclusions 12 Acknowledgments 13 References 13 Abstract: Glioblastoma (GBM) stem-like cells (GSCs) represent the most undifferentiated state of malignant cells with distinct biological characteristics. The fraction of these cells within a glial brain tumor, ranging from 2–30%, is correlating with the increasing WHO stage and poor prognosis of patients' survival. GSCs represent the least vulnerable, thus most preferential target cell population to be exposed to various therapeutic modalities, although the underlying mechanisms of this resistance are not yet fully understood. For the development of GSC-targeting therapies, further in depth studies are needed using enriched and stable GSC cell populations. Here, we discuss the current approaches of GSC isolation and validation based on expression of stemness and oncogenic markers as well as on functional assays. The enrichment of GSC phenotypes in established cell lines and/or primary tumor cultures, achieved by different strategies, is reviewed, providing a comprehensive comparison of selected studies and contemplating the characterization of the plethora of variants of reported GBM population exhibiting the GSC phenotype. ABBREVIATIONS: Aldehyde dehydrogenase (ALDH) Brain tumor initiating cells (BTIC) Cancer stem cell (CSC) Epidermal growth factor (EGF) Epithelial to mesenchymal transition (EMT) Fibroblast growth factor (FGF) Glioblastoma multiforme (GBM) Glioblastoma stem-like cell (GSC) Iso-dehydrogenase 1 (IDH1) Neural progenitor cell (NPC) Neural stem cell (NSC) O-6-methylguanine-DNA-methyltransferase (MGMT) Temozolomide (TMZ)Journal of Cancer Sttem Cell Research. 11/2014;
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ABSTRACT: SERPINB3 is a cysteine-proteases inhibitor up-regulated in a significant number of cirrhotic patients carrying hepatocellular carcinoma (HCC) and recently proposed as a prognostic marker for HCC early recurrence. SERPINB3 has been reported to stimulate proliferation, inhibit apoptosis and, similar to what reported for hypoxia, to trigger epithelial-to-mesenchymal transition (EMT) and increased invasiveness in liver cancer cells. This study has investigated whether SERPINB3 expression is regulated by hypoxia-related mechanisms in liver cancer cells. Exposure of HepG2 and Huh7 cells to hypoxia up-regulated SERPINB3 transcription, protein synthesis and release in the extracellular medium. Hypoxia-dependent SERPINB3 up-regulation was selective (no change detected for SERPINB4) and operated through hypoxia inducible factor (HIF)-2α (not HIF-1α) binding to SERPINB3 promoter, as confirmed by chromatin immuno-precipitation assay and silencing experiments employing specific siRNAs. HIF-2α-mediated SERPINB3 up-regulation under hypoxic conditions required intracellular generation of ROS. Immuno-histochemistry (IHC) and transcript analysis, performed in human HCC specimens, revealed co-localization of the two proteins in liver cancer cells and the existence of a positive correlation between HIF-2α and SERPINB3 transcript levels, respectively. Hypoxia, through HIF-2α-dependent and redox-sensitive mechanisms, up-regulates the transcription, synthesis and release of SERPINB3, a molecule with a high oncogenic potential.Oncotarget 01/2015; · 6.63 Impact Factor
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ABSTRACT: Epidemiology studies have established a strong link between lung cancer and arsenic exposure. Currently, the role of disturbed cellular energy metabolism in carcinogenesis is a focus of scientific interest. Hypoxia inducible factor-1 alpha (HIF-1A) is a key regulator of energy metabolism, and it has been found to accumulate during arsenite exposure under oxygen-replete conditions. We modeled arsenic-exposed human pulmonary epithelial cells in vitro with BEAS-2B, a non-malignant lung epithelial cell line. Constant exposure to 1 microM arsenite (As) resulted in the early loss of anchorage-dependent growth, measured by soft agar colony formation, beginning at 6 weeks of exposure. This arsenite exposure resulted in HIF-1A accumulation and increased glycolysis, similar to the physiologic response to hypoxia, but in this case under oxygen-replete conditions. This "pseudo-hypoxia" response was necessary for the maximal acquisition of anchorage-independent growth in arsenite-exposed BEAS-2B. The HIF-1A accumulation and induction in glycolysis was sustained throughout a 52 week course of arsenite exposure in BEAS-2B. There was a time-dependent increase in anchorage-independent growth during the exposure to arsenite. When HIF-1A expression was stably suppressed, arsenite-induced glycolysis was abrogated, and the anchorage-independent growth was reduced. These findings establish that arsenite exerts a hypoxia-mimetic effect, which plays an important role in the subsequent gain of malignancy-associated phenotypes.PLoS ONE 12/2014; 9(12):e114549. · 3.53 Impact Factor