EPH family receptor protein-tyrosine kinases and ephrin ligands play important roles in neural and cardiovasular development. Our recent study has shown that high-level expression of EPHB6, ephrin-B2, and ephrin-B3 predicts favorable disease outcome of neuroblastoma (NB), a common pediatric tumor of neural crest origin. The goal of this study is to elucidate the underlying mechanisms by which EPHB6, ephrin-B2, and ephrin-B3 provide NB cells with favorable phenotype. EPHIB6 lacks its kinase activity due to a mutation at the ATP acceptor site. Ephrin-B ligands are bi-functional molecules in that their extracellular domains promote angiogenesis and their cytoplasmic domains suppress the growth-promoting activity of activated protein-tyrosine kinases. Based on these observations, we hypothesize that EPHB6 restricts growth, angiogenesis and metastasis of NB cells by acting as a dominant negative member among the EPHB receptor family and/or by sequestering ephrin-B ligands from participating in angiogenesis. Cytoplasmic domains of ephrin-B ligands may inhibit NB growth by suppressing the growth stimulatory effect of receptor tyrosine kinases (IGF1R and TrkA) that are highly expressed by favorable NB. To test these hypotheses, we will examine whether EPHB6 restricts growth, angiogenesis and metastasis of NB cells. We will also examine whether extracellular domains of ephrin-B2 and ephrin-B3, in the absence of EPHB6, facilitate angiogenesis and metastasis of NB and whether EPHB6 blocks the action of ephrin-B ligands in facilitating these processes. We will investigate whether cytoplasmic domains of ephrin-B2 and ephrin-B3 suppress the growth promoting activity of IGF1R and TrkA. Lastly, we will examine whether inhibitors of DNA methylation and histone deacetylation increase EPHB6, ephrin-B2, and ephrin-B3 expressions in unfavorable NB cells, and if so, how these changes affect growth, angiogenesis and metastasis of unfavorable NB cells. Results of this study would reveal novel mechanisms by which EPHB6 and ephrin-B ligands restrict growth, angiogenesis and metastasis of NB. Such knowledge may help develop an innovative and effective treatment for unfavorable NB.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
7R01CA085519-04
Application #
6789985
Study Section
Pathology B Study Section (PTHB)
Program Officer
Woodhouse, Elizabeth
Project Start
2001-07-01
Project End
2006-06-30
Budget Start
2004-09-20
Budget End
2005-06-30
Support Year
4
Fiscal Year
2004
Total Cost
$287,701
Indirect Cost
Name
Emory University
Department
Pediatrics
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
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Torres, Jaime; Regan, Paul L; Edo, Robby et al. (2010) Biological effects of induced MYCN hyper-expression in MYCN-amplified neuroblastomas. Int J Oncol 37:983-91
Kung, Bing; Zhao, Huaqing; Hicks, Sakeenah L et al. (2009) Biological significance of EPHA2 expression in neuroblastoma. Int J Oncol 35:845-50
Ikegaki, Naohiko; Gotoh, Takahiro; Kung, Bing et al. (2007) De novo identification of MIZ-1 (ZBTB17) encoding a MYC-interacting zinc-finger protein as a new favorable neuroblastoma gene. Clin Cancer Res 13:6001-9
Tang, Xao X; Robinson, Marjorie E; Riceberg, Justin S et al. (2004) Favorable neuroblastoma genes and molecular therapeutics of neuroblastoma. Clin Cancer Res 10:5837-44