Objective To explore the effect of open reading frame 66(C12ORF66)located at chromosome 12 on the viability of MYCN amplified NB cell lines.Methods DDatasets GSE16476 and GSE49710 in R2 database were analyzed for expression level of C12ORF66 in MYCN amplified and MYCN non-amplified NB cells and its potential correlation with the prognosis of pediatric patients.C12ORF66 mRNA expression level in normal tissue immortalized cell lines,MYCN amplified and MYCN non-amplified cell lines were detected by RT-qRCR.Transient or stable knockdown of C12ORF66 cell lines were constructed to compare the difference in real time cellular analysis(RTCA),colony formation,Ki67 positive cells between the control group and the C12ORF66 knockdown group.Results By analyzing R2 datasets,C12ORF66 level in MYCN amplified samples was significantly higher than that in MYCN non-amplified samples,and the expression of C12ORF66 was negatively correlated with the prognosis of pediatric patients(P＜0.05).C12ORF66 highly expressed in MYCN-amplified BE(2)-C and SK-N-BE(2)cell lines than in MYCN non-amplified CHLA-255 and SH-SY5Y cell lines(P＜0.001).Transient or stable knockdown of C12ORF66 resulted in significant slow down of proliferation of MYCN amplified NB cells(P＜0.001),the colony formation ability was significantly reduced(P＜0.001),and the proportion of Ki67 positive cells was significantly decreased(P＜0.05).Conclusions C12ORF66 was highly expressed in MYCN amplified clinical NB samples and cell lines which is believed to be correlated with poor prognosis of pediatric patients.C12ORF66 knockdown signifi-cantly inhibits cell viability of NB cells.