The hypoxia inducible factor-1α (HIF1α) 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 a serum-free medium in the presence or absence of CoCl2 (100 μM, hypoxia mimic) for up to 48 h. SH-SY5Y and SK-N-MC cell numbers were not affected by CoCl2 treatment, while mitochondrial activity was reduced by ∼50% in SH-SY5Y cells and by ∼70% in SK-N-MC cells. Intracellular accumulation of HIF1α protein was detected as early as 30 min of post-hypoxia, followed by the increase of mRNA for vascular endothelial growth factor (VEGF) and nuclear accumulation of the ID1–2 transcription factors by 4 h. In hypoxic SH-SY5Y NB cells, real-time PCR analysis showed that the genes involved in maintenance of cell–cell and cell–matrix interactions (i.e. adenomatosis polyposis coli, E-cadherin, catenin, EphB2, fibronectin-1, HTATIP2, tissue inhibitor of metalloprotease-4) were down-regulated by up to 90%, while genes involved in enhancement of metastatic behavior (integrin a7b1, hepatocyte growth factor receptor, transforming growth factor-β1, VEGF, kisspeptin, interleukin-1β) were dramatically up-regulated above 200%. These changes were all consistent with the induction of epithelial–mesenchymal transition. We have thus demonstrated that NB cell adaptation to hypoxia, in addition to the modulation of HIF1α and VEGF expression and nuclear translocation of ID1 and ID2 transcription factors, involve in the activation of a gene expression program consistent with the pro-metastatic events. These processes are probably responsible for the NB cell transition from an adherent phenotype to a highly migratory, invasive and aggressive NB cell type.
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Preamrudee Poomthavorn, Sheena H X Wong, Sandra Higgins, George A Werther, and Vincenzo C Russo
K-M Fung, E N S Samara, C Wong, A Metwalli, R Krlin, B Bane, C Z Liu, J T Yang, J V Pitha, D J Culkin, B P Kropp, T M Penning, and Hsueh-Kung Lin
Type 2 3α-hydroxysteroid dehydrogenase (3α-HSD) is a multi-functional enzyme that possesses 3α-, 17β- and 20α-HSD, as well as prostaglandin (PG) F synthase activities and catalyzes androgen, estrogen, progestin and PG metabolism. Type 2 3α-HSD was cloned from human prostate, is a member of the aldo-keto reductase (AKR) superfamily and was named AKR1C3. In androgen target tissues such as the prostate, AKR1C3 catalyzes the conversion of Δ4-androstene-3,17-dione to testosterone, 5α-dihydrotestosterone to 5α-androstane-3α,17β-diol (3α-diol), and 3α-diol to androsterone. Thus AKR1C3 may regulate the balance of androgens and hence trans-activation of the androgen receptor in these tissues. Tissue distribution studies indicate that AKR1C3 transcripts are highly expressed in human prostate. To measure AKR1C3 protein expression and its distribution in the prostate, we raised a monoclonal antibody specifically recognizing AKR1C3. This antibody allowed us to distinguish AKR1C3 from other AKR1C family members in human tissues. Immunoblot analysis showed that this monoclonal antibody binds to one species of protein in primary cultures of prostate epithelial cells and in LNCaP prostate cancer cells. Immunohistochemistry with this antibody on human prostate detected strong nuclear immunoreactivity in normal stromal and smooth muscle cells, perineurial cells, urothelial (transitional) cells, and endothelial cells. Normal prostate epithelial cells were only faintly immunoreactive or negative. Positive immunoreactivity was demonstrated in primary prostatic adenocarcinoma in 9 of 11 cases. Variable increases in immunoreactivity for AKR1C3 was also demonstrated in non-neoplastic changes in the prostate including chronic inflammation, atrophy and urothelial (transitional) cell metaplasia. We conclude that elevated expression of AKR1C3 is highly associated with prostate carcinoma. Although the biological significance of elevated AKR1C3 in prostatic carcinoma is uncertain, AKR1C3 may be responsible for the trophic effects of androgens and/or PGs on prostatic epithelial cells.