Abstract LB-367: New evidence supports the potential use of methotrexate in children with MYCN-amplified neuroblastoma.

Abstract

Abstract Background Folate is essential for cell growth and differentiation. Cancer cells frequently up-regulate folate receptors to increase folate uptake to meet their elevated need for nucleotides to support DNA synthesis and growth. SLC19A1 encodes for a major folate or anti-folate transporter and has been reported to be regulated by oncogenic transcription factors. In childhood neuroblastoma, amplification of the MYCN oncogene is a strong prognostic marker for predicting unfavourable outcome. In light of previous findings showing that overexpression of SLC19A1 increases folate influx and methotrexate (MTX) sensitivity, we aimed to investigate the relationship between SLC19A1 expression, MYCN amplification and expression, to determine if this relationship modified MTX sensitivity in neuroblastoma. Methods Expression levels of SLC19A1 and MYCN were examined in 42 neuroblastoma patient samples and in two independent in vitro MYCN functional systems. The impact of MYCN amplification/expression and SLC19A1 expression on MTX sensitivity were evaluated on 13 neuroblastoma cell lines. SLC19A1 G80A polymorphism was also examined to determine its impact on SLC19A1 gene expression and MTX sensitivity. Results Expression levels of SLC19A1 and MYCN were positively correlated in neuroblastoma tumour samples (p=0.0001). Induction of MYCN in vitro increased the mRNA expression levels of SLC19A1 by 12-fold (p=0.0003) while silencing of MYCN reduced the expression levels of SLC19A1 by 7-fold (p=0.0017). Neuroblastoma cell lines with MYCN overexpression or amplification were at least 2000-fold more sensitive to MTX than those without (expression: p=0.0002; amplification: p<0.0001). However, SLC19A1 G80A polymorphism did not appear to impact on SLC19A1 gene expression or MTX sensitivity. Conclusions Our data indicate a potential functional link between MYCN and the regulation of anti-folate uptake. Our findings suggest that MYCN amplification confers MTX sensitivity through the regulation of the folate receptor; SLC19A1. Targeting SLC19A1 mediated anti-folate uptake in patients with MYCN amplification may provide a new therapeutic approach in children with neuroblastoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-367. doi:10.1158/1538-7445.AM2011-LB-367