Abstract 3128: Mxd3 is required for proliferation of human neuroblastoma cells.

Abstract

Abstract Neuroblastoma (NB) is the most common extracranial solid tumor in children. Up to 45% of the cases are high risk at diagnosis, representing very aggressive, usually metastasized tumors that are refractory or recurrent after all available therapies. Prognosis for these patients is very poor with only 30% survival. MXD3 is a transcription factor previously shown in our lab to be a novel member of the Hedgehog (Hh) pathway (Yun, Rust, Ishimaru, Diaz, Mol Cell Biol, 2007) in granule neuron precursors. In these cells, overexpression of MXD3 results in higher MYCN expression, suggesting a functional interaction between the two transcription factors. MXD3 phenocopies MYCN expression in mouse models of medulloblastoma; we have also shown that it is expressed in human medulloblastoma and that its knockdown reduces proliferation of human medulloblastoma cell lines (Barisone et al., PLoS One, 2012). More than 20% of NBs have MYCN amplification, which is considered a marker of poor prognosis. In the current study, we investigated a possible role for MXD3 in NB cell proliferation. Using qRT-PCR we observed high levels of MXD3 mRNA expression in 5 NB cell lines: SK-N-DZ, IMR-32, SH-SY5Y, SK-N-BE and SK-N-SH. Immunoblot analysis with anti-MXD3 monoclonal antibodies confirmed that the protein was present in these cells. Furthermore, immunohistochemistry analysis showed strong immunoreactivity in a cohort of 16 primary NB tissue specimens. We investigated the role of MXD3 in NB cell proliferation by silencing MXD3 in the SK-N-DZ cell line. We used lentiviral delivery to knockdown MXD3 using an RNA interference approach. Upon transduction by the viral vector, MXD3 knockdown was confirmed at both the RNA and protein level. Within 48 hours, MXD3 protein levels were reduced >90% in cells infected with the shMXD3 virus but not with the control virus. MXD3 knockdown resulted in decreased proliferation in NB cells, supporting our hypothesis that it may be involved in the maintenance of NB. We analyzed cell cycle progression after knockdown using flow cytometry. We observed no significant differences in the G0/G1, S or G2/M populations between experimental and control samples. Our results suggest that MXD3 is important for NB cell proliferation, possibly by acting as an anti-apoptotic factor. Therefore, MXD3 is a potential candidate for targeted therapies against neuroblastoma. Citation Format: Gustavo Barisone, Noriko Satake, Carly Lewis, Connie Duong, Cathy Chan, Kit Lam, Jan Nolta, Elva Diaz. Mxd3 is required for proliferation of human neuroblastoma cells. [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 3128. doi:10.1158/1538-7445.AM2013-3128