ATF4 and N‐Myc coordinate glutamine metabolism in MYCN‐amplified neuroblastoma cells through ASCT2 activation

Abstract Amplification of the MYCN gene in human neuroblastoma predicts poor prognosis and resistance to therapy. We previously showed that MYCN ‐amplified neuroblastoma cells constantly require large amounts of glutamine to support their unabated growth. However, the identity and regulation of the transporter(s) that capture glutamine in MYCN ‐amplified neuroblastoma cells and the clinical significance of the transporter(s) in neuroblastoma diagnosis remain largely unknown. Here, we performed a systemic glutamine influx analysis and identified that MYCN ‐amplified neuroblastoma cells predominantly rely on activation of ASCT2 (solute carrier family 1 member 5, SLC1A5 ) to maintain sufficient levels of glutamine essential for the TCA cycle anaplerosis. Consequently, ASCT2 depletion profoundly inhibited glutaminolysis, concomitant with a substantial decrease in cell proliferation and viability in vitro and inhibition of tumourigenesis in vivo . Mechanistically, we identified ATF4 as a novel regulator which coordinates with N‐Myc to directly activate ASCT2 expression. Of note, ASCT2 expression, which correlates with that of N‐Myc and ATF4 , is markedly elevated in high‐stage neuroblastoma tumour samples compared with low‐stage ones. More importantly, high ASCT2 expression is significantly associated with poor prognosis and survival of neuroblastoma patients. In aggregate, these findings elucidate a novel mechanism depicting how cell autonomous insults ( MYCN amplification) and microenvironmental stresses ( ATF4 induction) in concert coordinate ASCT2 activation to promote aggressive neuroblastoma progression, and establish ASCT2 as a novel biomarker in patient prognosis and stratification. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd