title: Downregulation of hnRNP A2/B1 expression in tumor cells under prolonged hypoxia.
abstract: Heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 has been previously shown to be overexpressed in breast and lung tumors. Because hypoxia is a feature inherent in solid tumors, the regulation of hnRNP A2/B1 expression and subcellular localization under hypoxic conditions was studied on human lung and breast carcinoma cell lines. We found that sustained hypoxic treatment downregulated hnRNP A2/B1 expression in MCF7 and H157 cell lines. Northern blot analysis showed that this decay: (i) was observed as a marked diminution of transcript levels after 24-48 h of exposure to low oxygen tension; (ii) is not mediated by the transcription factor, hypoxia inducible factor-1; and (iii) is partially dependent on a higher hnRNP A2/B1 messenger RNA turnover under hypoxic than normoxic conditions. Immunocytochemical staining also showed a significant diminution of hnRNP A2/B1 staining in these cell lines after 24-48 h of hypoxia, together with a predominant loss of cytoplasmic staining. Further investigations are warranted to evaluate the relevance of modulation of hnRNP A2/B1 in hypoxic environments relative to its previously reported utility as a marker of early lung carcinogenesis.
authors.affiliation: Cell and Cancer Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Garayoa
authors.forename: Yan-Gao
authors.initials: YG
authors.lastname: Man
authors.forename: Alfredo
authors.initials: A
authors.lastname: Martínez
authors.forename: Frank
authors.initials: F
authors.lastname: Cuttitta
authors.forename: James L
authors.initials: JL
authors.lastname: Mulshine
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D015687:Cell Hypoxia; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007150:Immunohistochemistry; D009687:Nuclear Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C439768:hnRNP A2