Publications

Hypoxia-inducible factor (HIF) 1 and HIF-2 are heterodimeric proteins composed of an oxygen-regulated HIF-1α or HIF-2α subunit, respectively, and a constitutively expressed HIF-1β subunit, which mediate adaptive transcriptional responses to hypoxia. Here, we report that Sirt7 (sirtuin-7) negatively regulates HIF-1α and HIF-2α protein levels by a mechanism that is independent of prolyl hydroxylation and that does not involve proteasomal or lysosomal degradation. The effect of Sirt7 was maintained in the presence of the sirtuin inhibitor nicotinamide and upon deletion or mutation of its deacetylase domain, indicating a non-catalytic function. Knockdown of Sirt7 led to an increase in HIF-1α and HIF-2α protein levels and an increase in HIF-1 and HIF-2 transcriptional activity. Thus, we identify a novel molecular function of Sirt7 as a negative regulator of HIF signaling.

<p>Supplementary Table S1. Primer sequences used for qPCR.</p>

Abstract Metastasis is the leading cause of death among patients who have breast cancer. Understanding the role of the extracellular matrix in the metastatic process may lead to the development of improved therapies to treat cancer patients. Intratumoral hypoxia, found in the majority of breast cancers, is associated with an increased risk of metastasis and mortality. Here we demonstrate that hypoxia-inducible factor 1 activates the transcription of genes encoding collagen prolyl hydroxylases that are critical for collagen deposition by breast cancer cells. We identify that expression of collagen prolyl hydroxylases promotes cancer cell alignment along collagen fibers resulting in enhanced cancer cell invasion and metastasis to lymph nodes and lungs. We establish the prognostic significance of collagen hydroxylase expression in human breast cancer biopsies and evaluate the novel use of ethyl 3,4-dihydroxybenzoate, a hydroxylase inhibitor, which decreases tumor fibrosis and metastasis in a mouse model of breast cancer. Citation Format: Daniele M. Gilkes, Pallavi Chaturvedi, Carmen Wong, Saumendra Bajpai, Hong Wei, Maimon Hubbi, Denis Wirtz, Gregg Semenza. Collagen hydroxylases are essential for breast cancer metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A3.

Abstract Hypoxia-inducible factor 1 (HIF-1) activates transcription of genes encoding proteins that play key roles in breast cancer biology. We hypothesized that interaction of HIF-1 with epigenetic regulators may increase HIF-1 transcriptional activity and thereby promote breast cancer progression. We report that the histone demethylase jumonji domain containing protein 2C (JMJD2C) selectively interacts with HIF-1α, but not HIF-2α, and that HIF-1α mediates recruitment of JMJD2C to the hypoxia response elements (HREs) of HIF-1 target genes. JMJD2C decreases trimethylation of histone H3 at lysine 9, and enhances HIF-1 binding to HREs, thereby activating transcription of BNIP3, LDHA,PDK1, and SLC2A1, which encode proteins that are required for metabolic reprogramming, as well as LOXL2 and L1CAM, which encode proteins that are required for lung metastasis. JMJD2C expression is significantly associated with expression of GLUT1, LDHA, PDK1, LOX, LOXL2, and L1CAM mRNA in human breast cancer biopsies. JMJD2C knockdown inhibits breast tumor growth and spontaneous metastasis to the lungs of mice following mammary fat pad injection. Taken together, these findings establish a novel epigenetic mechanism that stimulates HIF-1-mediated transactivation of genes encoding proteins involved in metabolic reprogramming and lung metastasis in breast cancer. Citation Format: Weibo Luo, Ryan Chang, Jun Zhong, Akhilesh Pandey, Gregg L. Semenza. Histone demethylase JMJD2C is a coactivator for hypoxia-inducible factor 1 that is required for breast cancer progression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2319. doi:10.1158/1538-7445.AM2013-2319

<p>Supplemental Legends</p>

Nitric oxide (NO) is a signaling molecule that can trigger adaptive (physiological) or maladaptive (pathological) responses to stress stimuli in a context-dependent manner. We have previously reported that NO may signal axonal injury to neighboring glial cells. In this study, we show that mice deficient in neuronal nitric oxide synthase (nNOS −/− ) are more vulnerable than WT mice to toxin-induced peripheral neuropathy. The administration of NO donors to primary dorsal root ganglion cultures prevents axonal degeneration induced by acrylamide in a dose-dependent manner. We demonstrate that NO-induced axonal protection is dependent on hypoxia-inducible factor (HIF)-1–mediated transcription of erythropoietin (EPO) within glial (Schwann) cells present in the cultures. Transduction of Schwann cells with adenovirus AdCA5 encoding a constitutively active form of HIF-1α results in amelioration of acrylamide-induced axonal degeneration in an EPO-dependent manner. Mice that are partially deficient in HIF-1α (HIF-1α +/− ) are also more susceptible than WT littermates to toxic neuropathy. Our results indicate that NO→HIF-1→EPO signaling represents an adaptive mechanism that protects against axonal degeneration.

<p>Supplementary Data PDF file 764K, Supplementary Figure S1, HIF-1 dependent P4HA1 and P4HA2 induction Supplementary Figure S2, P4HA1 and P4HA2 knockdown inhibits breast cancer growth and metastasis Supplementary Figure S3, Collagen hydroxylase knockdown decreases collagen deposition in vivo Supplementary Figure S4, P4HA1 and P4HA2 knockdown inhibits growth and metastasis of MDA-MB-435 cells Supplementary Figure S5, Picrosirius red staining of mouse lungs Supplementary Figure S6, P4HA re-expression in HIF-deficient cells rescues collagen deposition and metastasis Supplementary Figure S7, DHB treatment of MDA-MB-231 Cells Supplementary Table S1, Real-time qPCR primers. Supplemental Table S2, Comparison of human P4HA1 mRNA versus mouse P4HA1 mRNA expression in tumors. Supplemental Table S3, Correlation of P4HA1 and P4HA2 mRNA expression with receptor status</p>

<p>This figure provides an overview of the TEM results.</p>

Exposure of breast cancer cells to hypoxia increases the percentage of breast cancer stem cells (BCSCs), which are required for tumor initiation and metastasis, and this response is dependent on the activity of hypoxia-inducible factors (HIFs). We previously reported that exposure of breast cancer cells to hypoxia induces the ALKBH5-mediated demethylation of N6-methyladenosine (m6A) in NANOG mRNA leading to increased expression of NANOG, which is a pluripotency factor that promotes BCSC specification. Here we report that exposure of breast cancer cells to hypoxia also induces ZNF217-dependent inhibition of m6A methylation of mRNAs encoding NANOG and KLF4, which is another pluripotency factor that mediates BCSC specification. Although hypoxia induced the BCSC phenotype in all breast-cancer cell lines analyzed, it did so through variable induction of pluripotency factors and ALKBH5 or ZNF217. However, in every breast cancer line, the hypoxic induction of pluripotency factor and ALKBH5 or ZNF217 expression was HIF-dependent. Immunohistochemistry revealed that expression of HIF-1α and ALKBH5 was concordant in all human breast cancer biopsies analyzed. ALKBH5 knockdown in MDA-MB-231 breast cancer cells significantly decreased metastasis from breast to lungs in immunodeficient mice. Thus, HIFs stimulate pluripotency factor expression and BCSC specification by negative regulation of RNA methylation.

Actin filaments play an essential role in cell movement, and many posttranslational modifications regulate actin filament assembly. Here we report that prolyl hydroxylase 3 (PHD3) interacts with nonmuscle actin in human cells and catalyzes hydroxylation of actin at proline residues 307 and 322. Blocking PHD3 expression or catalytic activity by short hairpin RNA knockdown or pharmacological inhibition, respectively, decreased actin prolyl hydroxylation. PHD3 knockdown increased filamentous F-actin assembly, which was reversed by PHD3 overexpression. PHD3 knockdown increased cell velocity and migration distance. Inhibition of PHD3 prolyl hydroxylase activity by dimethyloxalylglycine also increased actin polymerization and cell migration. These data reveal a novel role for PHD3 as a negative regulator of cell motility through posttranslational modification of nonmuscle actins.

BACKGROUND Hypoxia inducible factor-1 (HIF-1) plays a critical role in angiogenesis during vascular development. The authors tested the hypothesis that HIF-1 expression correlates with progression and angiogenesis in brain tumors. METHODS The authors investigated the expression of the HIF-1α and HIF-1β subunits in human glioma cell lines and brain tumor tissues using Western blot analysis and immunohistochemistry. RESULTS In glioblastomas multiforme (GBMs), HIF-1α primarily was localized in pseudopalisading cells around areas of necrosis and in tumor cells infiltrating the brain at the tumor margin. In contrast, HIF-1α was expressed in stromal cells throughout hemangioblastomas (HBs). Like HIF-1α, HIF-1β was most highly expressed in high grade tumors but was expressed more widely than HIF-1α, including cells away from necrotic zones. In the brains of mice injected with Glioma 261 cells, a pattern of HIF-1α expression identical to that observed in human GBMs was noted. CONCLUSIONS In GBMs, the heterogeneous pattern of HIF-1α expression appears to be determined at least in part by tissue oxygenation, whereas in HBs the homogeneous expression of HIF-1α may be driven by an oncogenic rather than a physiologic stimulus. Cancer 2000;88:2606–18. © 2000 American Cancer Society.