Hypoxia upregulates the expression of the NDRG1 gene leading to its overexpression in various human cancers

BACKGROUND: The expression of NDRG1 gene is induced by nickel, a transition metal sharing similar physical properties to cobalt. Nickel may create hypoxia-like conditions in cells and induce hypoxia-responsive genes, as does cobalt. Therefore NDRG1 is likely to be another gene induced by hypoxia. HIF-1 is a transcription factor which has a major role in the regulation of hypoxia-responsive genes, and thus it could be involved in the transcriptional regulation of NDRG1 gene. Hypoxia is such a common feature of solid tumours that it is of interest to investigate the expression of Ndrg1 protein in human cancers. RESULTS: Hypoxia and its mimetics induce in vitro expression of NDRG1 gene and cause the accumulation of Ndrg1 protein. Protein levels remain high even after cells revert to normoxia. Although HIF-1 is involved in the regulation of NDRG1, long term hypoxia induces the gene to some extent in HIF-1 knock-out cells. In the majority of human tissues studied, Ndrg1 protein is overexpressed in cancers compared to normal tissues and also reflects tumour hypoxia better than HIF-1 protein. CONCLUSIONS: Hypoxia is an inducer of the NDRG1 gene, and nickel probably causes the induction of the gene by interacting with the oxygen sensory pathway. Hypoxic induction of NDRG1 is mostly dependent on the HIF-1 transcription factor, but HIF-1 independent pathways are also involved in the regulation of the gene during chronic hypoxia. The determination of Ndrg1 protein levels in cancers may aid the diagnosis of the disease

Enhanced overexpression of an HIF-1/hypoxia-related protein in cancer cells.

Cap43 is a protein whose RNA is induced under conditions of severe hypoxia or prolonged elevations of intracellular calcium. Additionally, Ni and Co also induce Cap43 because they produce a state of hypoxia in cells. Cap43 protein is expressed at low levels in normal tissues; however, in a variety of cancers, including lung, brain, melanoma, liver, prostate, breast, and renal cancers, Cap43 protein is overexpressed in cancer cells. The low level of expression of Cap43 in some normal tissues compared with their cancerous counterparts, combined with the high stability of Cap43 protein and mRNA, makes the Cap43 gene a new, important cancer marker. We hypothesize that the mechanism of Cap43 overexpression in cancer cells involves a state of hypoxia characteristic of cancer cells where the Cap43 protein becomes a signature for this hypoxic state

Homozygous loss-of-function mutations in SLC26A7 cause goitrous congenital hypothyroidism.

Defects in genes mediating thyroid hormone biosynthesis result in dyshormonogenic congenital hypothyroidism (CH). Here, we report homozygous truncating mutations in SLC26A7 in 6 unrelated families with goitrous CH and show that goitrous hypothyroidism also occurs in Slc26a7-null mice. In both species, the gene is expressed predominantly in the thyroid gland, and loss of function is associated with impaired availability of iodine for thyroid hormone synthesis, partially corrected in mice by iodine supplementation. SLC26A7 is a member of the same transporter family as SLC26A4 (pendrin), an anion exchanger with affinity for iodide and chloride (among others), whose gene mutations cause congenital deafness and dyshormonogenic goiter. However, in contrast to pendrin, SLC26A7 does not mediate cellular iodide efflux and hearing in affected individuals is normal. We delineate a hitherto unrecognized role for SLC26A7 in thyroid hormone biosynthesis, for which the mechanism remains unclear

Comprehensive Screening of Eight Known Causative Genes in Congenital Hypothyroidism With Gland-in-Situ.

CONTEXT: Lower TSH screening cutoffs have doubled the ascertainment of congenital hypothyroidism (CH), particularly cases with a eutopically located gland-in-situ (GIS). Although mutations in known dyshormonogenesis genes or TSHR underlie some cases of CH with GIS, systematic screening of these eight genes has not previously been undertaken. OBJECTIVE: Our objective was to evaluate the contribution and molecular spectrum of mutations in eight known causative genes (TG, TPO, DUOX2, DUOXA2, SLC5A5, SLC26A4, IYD, and TSHR) in CH cases with GIS. Patients, Design, and Setting: We screened 49 CH cases with GIS from 34 ethnically diverse families, using next-generation sequencing. Pathogenicity of novel mutations was assessed in silico. PATIENTS, DESIGN, AND SETTING: We screened 49 CH cases with GIS from 34 ethnically diverse families, using next-generation sequencing. Pathogenicity of novel mutations was assessed in silico. RESULTS: Twenty-nine cases harbored likely disease-causing mutations. Monogenic defects (19 cases) most commonly involved TG (12), TPO (four), DUOX2 (two), and TSHR (one). Ten cases harbored triallelic (digenic) mutations: TG and TPO (one); SLC26A4 and TPO (three), and DUOX2 and TG (six cases). Novel variants overall included 15 TG, six TPO, and three DUOX2 mutations. Genetic basis was not ascertained in 20 patients, including 14 familial cases. CONCLUSIONS: The etiology of CH with GIS remains elusive, with only 59% attributable to mutations in TSHR or known dyshormonogenesis-associated genes in a cohort enriched for familial cases. Biallelic TG or TPO mutations most commonly underlie severe CH. Triallelic defects are frequent, mandating future segregation studies in larger kindreds to assess their contribution to variable phenotype. A high proportion (∼41%) of unsolved or ambiguous cases suggests novel genetic etiologies that remain to be elucidated.This study made use of data generated by the UK10K Project and we acknowledge the contribution of the UK10K Consortium. This work was supported by Wellcome Trust Grants 100585/Z/12/Z (to N.S.), and 095564/Z/11/Z (to V.K.C.) and the National Institute for Health Research Cambridge Biomedical Research Center (to V.K.C., N.S.). E.G.S and C.A.A. are supported by the Wellcome Trust (098051). Funding for the UK10K Project was provided by the Wellcome Trust under award WT091310

Homozygous loss-of-function mutations in SLC26A7 cause goitrous congenital hypothyroidism

Defects in genes mediating thyroid hormone biosynthesis result in dyshormonogenic congenital hypothyroidism (CH). Here, we report homozygous truncating mutations in SLC26A7 in 6 unrelated families with goitrous CH and show that goitrous hypothyroidism also occurs in Slc26a7-null mice. In both species, the gene is expressed predominantly in the thyroid gland, and loss of function is associated with impaired availability of iodine for thyroid hormone synthesis, partially corrected in mice by iodine supplementation. SLC26A7 is a member of the same transporter family as SLC26A4 (pendrin), an anion exchanger with affinity for iodide and chloride (among others), whose gene mutations cause congenital deafness and dyshormonogenic goiter. However, in contrast to pendrin, SLC26A7 does not mediate cellular iodide efflux and hearing in affected individuals is normal. We delineate a hitherto unrecognized role for SLC26A7 in thyroid hormone biosynthesis, for which the mechanism remains unclear

Mutations in SLC29A3, Encoding an Equilibrative Nucleoside Transporter ENT3, Cause a Familial Histiocytosis Syndrome (Faisalabad Histiocytosis) and Familial Rosai-Dorfman Disease

The histiocytoses are a heterogeneous group of disorders characterised by an excessive number of histiocytes. In most cases the pathophysiology is unclear and treatment is nonspecific. Faisalabad histiocytosis (FHC) (MIM 602782) has been classed as an autosomal recessively inherited form of histiocytosis with similarities to Rosai-Dorfman disease (RDD) (also known as sinus histiocytosis with massive lymphadenopathy (SHML)). To elucidate the molecular basis of FHC, we performed autozygosity mapping studies in a large consanguineous family and identified a novel locus at chromosome 10q22.1. Mutation analysis of candidate genes within the target interval identified biallelic germline mutations in SLC29A3 in the FHC kindred and in two families reported to have familial RDD. Analysis of SLC29A3 expression during mouse embryogenesis revealed widespread expression by e14.5 with prominent expression in the central nervous system, eye, inner ear, and epithelial tissues including the gastrointestinal tract. SLC29A3 encodes an intracellular equilibrative nucleoside transporter (hENT3) with affinity for adenosine. Recently germline mutations in SLC29A3 were also described in two rare autosomal recessive disorders with overlapping phenotypes: (a) H syndrome (MIM 612391) that is characterised by cutaneous hyperpigmentation and hypertrichosis, hepatomegaly, heart anomalies, hearing loss, and hypogonadism; and (b) PHID (pigmented hypertrichosis with insulin-dependent diabetes mellitus) syndrome. Our findings suggest that a variety of clinical diagnoses (H and PHID syndromes, FHC, and familial RDD) can be included in a new diagnostic category of SLC29A3 spectrum disorder