Abstract 3776: Hypoxia-inducible factor 1α (HIF1α) has a prometastatic effect in uveal melanoma .
Authors: Asnaghi Laura , Lin Michael H. , Lim Kah Suan , Lim Kah Jing , Bar Eli E. , Eberhart Charles G. 
Published: August 2014

Abstract
Melanomas arising from the uveal tract of the eye represent the most frequent primary intraocular malignancy in adults and are the second most common type of melanoma. Uveal melanomas are prone to disseminate hematogenously to the liver, and have an overall survival rate of approximately 50%. Hypoxia-inducible factor 1α (HIF1α), a master transcriptional regulator of the hypoxic response, is strongly associated with aggressive uveal melanomas. Elevated expression of one of the HIF target gene lysyl oxidase (LOX) has been found at the invasive front of primary tumors, and is associated with shorter metastasis-free survival. Here we investigated the mechanism responsible for the prometastatic effect of HIF1α in uveal melanoma. Western blot examination of HIF1α and HIF2α proteins in uveal melanoma cell lines grown in normoxia (21% pO2) and in hypoxia (1% pO2) revealed HIF2α to be low. In contrast, HIF1α protein was relatively abundant in the OCM1, OCM3, OMM1, Mel290 and 92.1 uveal melanoma lines grown in normoxia, and was further induced by up to 5 fold in hypoxia. The mRNA levels of VEGF and LOX, two transcriptional targets of HIF1α, were also induced by 2 to 4 fold in hypoxia. Interestingly, while hypoxia reduced the growth of these lines as measured by MTS assay, low oxygen tension increased the ability of uveal melanoma cells to invade Matrigel by 2 to 5 fold. Genetic suppression of HIF1α expression through shRNA in OCM1 and 92.1 cells significantly decreased cellular growth in hypoxia (p&lt;0.0001) and greatly impaired cellular invasion both in normoxia and in hypoxia (p&lt;0.0001), suggesting that HIF1α is necessary for invasion even under normoxic conditions. In order to determine the downstream targets responsible for such profound effect of HIF1α on cellular invasion, we examined expression of Notch pathway members, which we have previously linked to uveal melanoma invasion. Interestingly, hypoxia induced mRNA expression of the Notch ligand Jag2 and target Hey1 by up to 3 fold. We also analyzed the expression of Snail, which is known to promote invasion and metastasis of tumors outside the eye, and which can be regulated by HIF1α. We observed more than 2 fold increase of Snail mRNA levels under hypoxic conditions in OCM1 cells, and this induction was abolished by suppressing HIF1α using shRNA. These data suggest that HIF1α plays a crucial role in promoting metastatic spread in uveal melanoma cells, possibly by regulating Notch activity or expression of the Snail transcription factor.
Citation Format: Laura Asnaghi, Michael H. Lin, Kah Suan Lim, Kah Jing Lim, Eli E. Bar, Charles G. Eberhart. Hypoxia-inducible factor 1α (HIF1α) has a prometastatic effect in uveal melanoma . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3776. doi:10.1158/1538-7445.AM2013-3776