Abstract 4164: Synergism between NEDD9 overexpression and loss of PTEN and INK4A/ARF in melanoma tumorigenesis
Authors: Hill Kristen S. , Wang Xue , Kim Youngchul , Messina Jane L. , Kim Minjung 
Published: July 2016

Abstract
The fact that melanoma, the most aggressive form of skin cancer, is driven by multiple combinations of genetic lesions has supported the use of genetically engineered mouse (GEM) models in validating the etiological and biological roles of oncogenes and tumor suppressors. Most of the currently studied mouse melanoma models are driven by RAS/RAF/MAPK activation via activating RAS or RAF mutations in combination with loss of INK4A/ARF or PTEN; therefore, BRAF/NRAS wild-type melanoma remains less well characterized and the overall survival of patients with metastatic BRAF/NRAS wild-type melanoma remains poor.
In this study, we investigated the hypothesis that NEDD9 could synergize with the loss of PTEN and INK4A/ARF in melanoma tumorigenesis. This hypothesis is based on our observation of an inverse correlation between PTEN expression and levels of NEDD9 gene expression in human melanoma samples. NEDD9 (neural precursor derived, developmentally downregulated gene 9) was previously identified by us as a target of a recurrent focal amplification, associated with acquisition of metastatic potential in the RAS-Ink/Arf model. We have shown that NEDD9 is up-regulated in 35∼50% of metastatic melanomas and enhances proliferation and invasion. First, we demonstrated that NEDD9 cooperated with PTEN loss in Ink4a/Arf-/- melanocytes to enhance cell proliferation, anchorage independent growth, and invasion in vitro. Additionally, when melanocytes were injected into nude mice either subcutaneously or intravenously, NEDD9 overexpression facilitated increased tumor growth and lung seeding, respectively. Further analysis showed that NEDD9 expression correlated with increased phosphorylation of ERK, SFKs (Src family kinases), AKT2, and STAT3. Of these pathways we have demonstrated through the use of small molecule inhibitors that both ERK and AKT2 signaling are required for the enhanced anchorage independent growth observed in NEDD9 overexpressing melanocytes. In addition, we generated a mouse model based on loss of PTEN and INK4A/ARF with or without NEDD9 upregulation. To do this, we generated a tet-inducible NEDD9 allele that carries a doxycycline-responsive, melanocyte-targeted NEDD9. These mice were crossed with a strain containing floxed PTEN and INK4A/ARF in combination with a melanocyte-targeted CreERT2. The development of cutaneous and ocular melanomas in these mice was enhanced by NEDD9 induction. This study will generate a body of knowledge for the in vivo roles of NEDD9 in melanoma tumorigenesis and identify signaling pathways that could be therapeutically targeted to treat patients with BRAF/NRAS wild-type melanoma
Citation Format: Kristen S. Hill, Xue Wang, Youngchul Kim, Jane L. Messina, Minjung Kim. Synergism between NEDD9 overexpression and loss of PTEN and INK4A/ARF in melanoma tumorigenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4164.