Hypoxia promotes uveal melanoma invasion through enhanced Notch and MAPK activation.
Publication/Presentation Date
1-1-2014
Abstract
The transcriptional response promoted by hypoxia-inducible factors has been associated with metastatic spread of uveal melanoma. We found expression of hypoxia-inducible factor 1α (HIF-1α) protein in well-vascularized tumor regions as well as in four cell lines grown in normoxia, thus this pathway may be important even in well-oxygenated uveal melanoma cells. HIF-1α protein accumulation in normoxia was inhibited by rapamycin. As expected, hypoxia (1% pO2) further induced HIF-1α protein levels along with its target genes VEGF and LOX. Growth in hypoxia significantly increased cellular invasion of all 5 uveal melanoma lines tested, as did the introduction of an oxygen-insensitive HIF-1α mutant into Mel285 cells with low HIF-1α baseline levels. In contrast, HIF-1α knockdown using shRNA significantly decreased growth in hypoxia, and reduced by more than 50% tumor invasion in four lines with high HIF-1α baseline levels. Pharmacologic blockade of HIF-1α protein expression using digoxin dramatically suppressed cellular invasion both in normoxia and in hypoxia. We found that Notch pathway components, including Jag1-2 ligands, Hes1-Hey1 targets and the intracellular domain of Notch1, were increased in hypoxia, as well as the phosphorylation levels of Erk1-2 and Akt. Pharmacologic and genetic inhibition of Notch largely blocked the hypoxic induction of invasion as did the pharmacologic suppression of Erk1-2 activity. In addition, the increase in Erk1-2 and Akt phosphorylation by hypoxia was partially reduced by inhibiting Notch signaling. Our findings support the functional importance of HIF-1α signaling in promoting the invasive capacity of uveal melanoma cells in both hypoxia and normoxia, and suggest that pharmacologically targeting HIF-1α pathway directly or through blockade of Notch or Erk1-2 pathways can slow tumor spread.
Volume
9
Issue
8
First Page
105372
Last Page
105372
ISSN
1932-6203
Published In/Presented At
Asnaghi, L., Lin, M. H., Lim, K. S., Lim, K. J., Tripathy, A., Wendeborn, M., Merbs, S. L., Handa, J. T., Sodhi, A., Bar, E. E., & Eberhart, C. G. (2014). Hypoxia promotes uveal melanoma invasion through enhanced Notch and MAPK activation. PloS one, 9(8), e105372. https://doi.org/10.1371/journal.pone.0105372
Disciplines
Medicine and Health Sciences
PubMedID
25166211
Department(s)
Administration, Department of Emergency Medicine
Document Type
Article