Expression and function of hypoxia inducible factor-1 alpha in human melanoma under non-hypoxic conditions
Open Access
- 17 November 2009
- journal article
- Published by Springer Science and Business Media LLC in Molecular Cancer
- Vol. 8 (1), 104
- https://doi.org/10.1186/1476-4598-8-104
Abstract
Background Hypoxia inducible factor-1 alpha (HIF-1α) protein is rapidly degraded under normoxic conditions. When oxygen tensions fall HIF-1α protein stabilizes and transactivates genes involved in adaptation to hypoxic conditions. We have examined the normoxic expression of HIF-1α RNA and protein in normal human melanocytes and a series of human melanoma cell lines isolated from radial growth phase (RGP), vertical growth phase (VGP) and metastatic (MET) melanomas. Results HIF-1α mRNA and protein was increased in RGP vs melanocytes, VGP vs RGP and MET vs VGP melanoma cell lines. We also detected expression of a HIF-1α mRNA splice variant that lacks part of the oxygen-dependent regulation domain in WM1366 and WM9 melanoma cells. Over-expression of HIF-1α and its splice variant in the RGP cell line SbCl2 resulted in a small increase in soft agar colony formation and a large increase in matrigel invasion relative to control transfected cells. Knockdown of HIF-1α expression by siRNA in the MET WM9 melanoma cell line resulted in a large decrease in both soft agar colony formation and matrigel invasion relative to cells treated with non-specific siRNA. There is a high level of ERK1/2 phosphorylation in WM9 cells, indicating an activated Ras-Raf-MEK-ERK1/2 MAPK pathway. Treatment of WM9 cells with 30 μM U0126 MEK inhibitor, decreased ERK1/2 phosphorylation and resulted in a decrease in HIF-1α expression. However, a 24 h treatment with 10 μM U0126 totally eliminated Erk1/2 phosphorylation, but did not change HIF-1alpha levels. Furthermore, siRNA knockdown of MEK siRNA did not change HIF-1alpha levels. Conclusion We speculate that metabolic products of U0126 decrease HIF-1alpha expression through "off target" effects. Overall our data suggest that increased HIF-1α expression under normoxic conditions contributes to some of the malignant phenotypes exhibited by human melanoma cells. The expanded role of HIF-1α in melanoma biology increases its importance as a therapeutic target.Keywords
This publication has 37 references indexed in Scilit:
- Notch1 is an effector of Akt and hypoxia in melanoma developmentJCI Insight, 2008
- Signal Transducer and Activator of Transcription 3 Is Required for Hypoxia-Inducible Factor-1α RNA Expression in Both Tumor Cells and Tumor-Associated Myeloid CellsMolecular Cancer Research, 2008
- Hypoxia-Independent Overexpression of Hypoxia-Inducible Factor 1α as an Early Change in Mouse HepatocarcinogenesisCancer Research, 2006
- Ras-dependent induction of HIF-1α785 via the Raf/MEK/ERK pathway: a novel mechanism of Ras-mediated tumor promotionOncogene, 2004
- Cancer genes and the pathways they controlNature Medicine, 2004
- Inhibition of prostate tumor growth by overexpression of NudC, a microtubule motor-associated proteinOncogene, 2003
- Standardized determination of real-time PCR efficiency from a single reaction set-upNucleic Acids Research, 2003
- Apoptosis and melanoma chemoresistanceOncogene, 2003
- Normoxic induction of the hypoxia‐inducible factor 1α by insulin and interleukin‐1β involves the phosphatidylinositol 3‐kinase pathwayFEBS Letters, 2002
- Hypoxia — a key regulatory factor in tumour growthNature Reviews Cancer, 2002