Activation of a prometastatic gene expression program in hypoxic neuroblastoma cells.
Endocr Relat Cancer. 2009 May 7;
Authors: Poomthavorn P, Wong S, Higgins S, Werther G, Russo V
The hypoxia inducible factor-1 alphavarphi(HIF-1varphi) is a key regulator of oxygen homeostasis, modulating cell survival and growth in cells exposed to hypoxia. In this study neuroblastoma (NB) cells SH-SY5Y and SK-N-MC were employed to determine the mechanisms regulating adaptation to hypoxia. NB cells were cultured in serum free medium in the presence or absence of CoCl2 (100muM, hypoxia mimic) for up to 48 hours. SH-SY5Y and SK-N-MC cell number was not affected by CoCl2 treatment, while mitochondrial activity was reduced by ~50% in SH-SY5Y and by ~70% in SK-N-MC cells. Intracellular accumulation of HIF-1varphi protein was detected as early as 30 min post-hypoxia, followed by increases of mRNA for VEGF and nuclear accumulation of the ID1-2 transcription factors by 4 hours. In hypoxic SH-SY5Y NB cells, real-time PCR analysis showed that genes involved in maintenance of cell-cell and cell-matrix interaction (ie. APC, E-cadherin, catenin, EphB2, fibronectin-1, TIP30, TIMP4) were down-regulated by up to 90%, while genes involved in enhancement of metastatic behaviour (integrin a7b1, HGF, TGFB1, VEGF, KiSS1, IL1B) were dramatically up-regulated above 200%. These changes were all consistent with the induction of epithelial-mesenchymal transition (EMT). We have thus demonstrated that NB cell adaptation to hypoxia, in addition to modulation of HIF-1varphiand VEGF expression and nuclear translocation of ID1 and ID2 transcription factors, involves the activation of a gene expression program consistent with pro-metastatic events. These processes are likely to be responsible for the NB cell transition from an adherent phenotype to a highly migratory, invasive and aggressive NB cell type.
PMID: 19423615 [PubMed - as supplied by publisher]