Abstract 3963: MYCN-dependent expression of sulfatase2 regulates neuroblastoma cell survival

Abstract

Abstract Despite the well-demonstrated role of MYCN in the pathogenesis of neuroblastoma, the mechanisms underlying its oncogenic function are not entirely understood and there is evidence that its function is in part dependent on the tumor microenvironment (TME). Heparan sulfate proteoglycans (HSPG) play a critical role in the interaction between tumor cells and the TME in great part because of their ability to retain cytokines, chemokines and growth factors and to control their bioavailability. This function of HSPG is dependent on the sulfation pattern that itself is controlled by sulfotransferases that add sulfate groups to the repeating disaccharide units and sulfatases (SULF) that selectively remove 6-O-sulfates. An unbiased analysis of the expression of 12 of these enzymes by RT-PCR in 8 human neuroblastoma cell lines revealed higher levels of expression of SULF2 in cell lines with amplification of the MYCN oncogene (MYCN-A), an observation that was confirmed at the protein level by Western blot analysis. We then demonstrated that the knock down (KD) of SULF2 in MYCN-A cells by siRNA resulted in a significant decrease in cell viability caused by a decrease in cell cycle entry and in apoptosis as documented by increase in caspase 3/7 activity, PARP cleavage and annexin-V expression. Evidence was provided that SULF2 is a downstream target of MYCN by demonstrating that overexpression of MYCN in CHLA-255 neuroblastoma cells increased SULF2 expression whereas downregulation of MYCN expression in SHEP-21N cells was followed by a downregulation of SULF2. Underlying the importance of SULF2 in neuroblastoma cell survival independently of MYCN, we demonstrated that overexpression of SULF2 in MYCN-NA cells increased cell viability without increasing MYCN expression. Finally, an analysis of SULF2 protein expression in 65 primary human neuroblastoma tumors indicated a statistically significant higher level of expression in MYCN-A tumors along with an almost complete absence of expression in MYCN-non amplified (NA) tumors, whether they were of favorable or unfavorable histology. The data thus identify SULF2 as a new downstream target of MYCN and a key contributor to its oncogenic function in human neuroblastoma. Citation Format: Valeria Solari, Lucia Borriello, G. Esteban Fernandez, Hiroyuki Shimada, Richard Sposto, Shahab Asgharzadeh, Edwin A. Yates, Jeremy E. Turnbull, Yves A. Declerck. MYCN-dependent expression of sulfatase2 regulates neuroblastoma cell survival. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3963. doi:10.1158/1538-7445.AM2014-3963