oxalylglycine and Lung-Neoplasms

The hypoxia-induced transcription factor HIF1 inhibits cell growth in normoxia through poorly understood mechanisms. A constitutive upregulation of hypoxia response is associated with increased malignancy, indicating a loss of antiproliferative effects of HIF1 in cancer cells. To understand these differences, we examined the control of cell cycle in primary human cells with activated hypoxia response in normoxia. Activated HIF1 caused a global slowdown of cell cycle progression through G1, S and G2 phases leading to the loss of mitotic cells. Cell cycle inhibition required a prolonged HIF1 activation and was not associated with upregulation of p53 or the CDK inhibitors p16, p21 or p27. Growth inhibition by HIF1 was independent of its Asn803 hydroxylation or the presence of HIF2. Antiproliferative effects of hypoxia response were alleviated by inhibition of lactate dehydrogenase and, more effectively, by boosting cellular production of NAD

Topics: A549 Cells; Adenocarcinoma, Bronchiolo-Alveolar; Amino Acids, Dicarboxylic; Basic Helix-Loop-Helix Transcription Factors; Carcinoma, Non-Small-Cell Lung; Cell Cycle; Cell Hypoxia; Cell Proliferation; Cytokines; Fibroblasts; Gene Knockdown Techniques; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; L-Lactate Dehydrogenase; Lung Neoplasms; NAD; Nicotinamide Phosphoribosyltransferase; Signal Transduction; Transfection

Prolyl hydroxylase-1 (PHD1), a member of the hypoxia inducible factor (HIF)-PHD family, plays an important role in regulating the stability of HIFs. The nuclear factor-κB (NF-κB) pathway consists of a family of transcription factors that play critical roles in inflammation, immunity, cell proliferation, differentiation, and survival. In this study, we demonstrate that PHD1 can inhibit NF-κB activity and its target genes in lung cancer cells based on both over-expression and RNA interference-mediated knockdown of PHD1 in human A549 lung cancer cells and HEK293 T cells. Of medical importance, PHD1 could induce cell cycle arrest in lung cancer cells, resulting in the suppression of cell proliferation. Xenograft tumor growth assays indicate that PHD1 plays a critical role in suppressing lung cancer growth. These findings reveal a new role of PHD1 in lung cancer and provide new treatment perspectives for cancer therapy by characterizing PHD1 as a potential target.

Topics: Amino Acids, Dicarboxylic; Animals; Cell Line, Tumor; Cell Proliferation; Cyclin D1; HEK293 Cells; Humans; Hypoxia-Inducible Factor-Proline Dioxygenases; Interleukin-1beta; Interleukin-8; Lung Neoplasms; Male; Mice; Mice, Inbred BALB C; Mice, Nude; RNA Interference; RNA, Messenger; S Phase Cell Cycle Checkpoints; Transcription Factor RelA; Tumor Necrosis Factor-alpha; Xenograft Model Antitumor Assays

Hypoxia, through the hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha (HIFs), induces angiogenesis by up-regulating a common set of angiogenic cytokines. Unlike HIF-1alpha, which regulates a unique set of genes, most genes regulated by HIF-2alpha overlap with those induced by HIF-1alpha. Thus, the unique contribution of HIF-2alpha remains largely obscure. By using adenoviral mutant HIF-1alpha and adenoviral mutant HIF-2alpha constructs, where the HIFs are transcriptionally active under normoxic conditions, we show that HIF-2alpha but not HIF-1alpha regulates adenosine A(2A) receptor in primary cultures of human lung endothelial cells. Further, siRNA knockdown of HIF-2alpha completely inhibits hypoxic induction of A(2A) receptor. Promoter studies show a 2.5-fold induction of luciferase activity with HIF-2alpha cotransfection. Analysis of the A(2A) receptor gene promoter revealed a hypoxia-responsive element in the region between -704 and -595 upstream of the transcription start site. By using a ChIP assay, we demonstrate that HIF-2alpha binding to this region is specific. In addition, we demonstrate that A(2A) receptor has angiogenic potential, as assessed by increases in cell proliferation, cell migration, and tube formation. Additional data show increased expression of A(2A) receptor in human lung tumor cancer samples relative to adjacent normal lung tissue. These data also demonstrate that A(2A) receptor is regulated by hypoxia and HIF-2alpha in human lung endothelial cells but not in mouse-derived endothelial cells.

Topics: Amino Acids, Dicarboxylic; Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Hypoxia; Cell Line; Cell Movement; Cell Proliferation; Cells, Cultured; Chromatin Immunoprecipitation; Endothelial Cells; Gene Expression; Humans; Luciferases; Lung; Lung Neoplasms; Mice; Neovascularization, Physiologic; Platelet Endothelial Cell Adhesion Molecule-1; Promoter Regions, Genetic; Receptors, Adenosine A2; Response Elements; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; RNA, Messenger; Vascular Endothelial Growth Factor A