N-Myc affects apoptosis through caspase-3/caspase-9. SHEP (A and C) and SHEP/MYCN (B and D) cells were transfected with either pcDNA3.1 empty vector or pcDNA3.1 containing MXI1-0-HA, MXI1-HA, or MXIex2-6-HA. Cells were plated and cultured in RPMI-1640 containing either low serum (0.5% FBS—A and B) or normal serum (10% FBS—C and D) with or without inhibitors to caspase-3 (c3-i), caspase-8 (c8-i), or caspase-9 (c9-i) or a caspase inhibitor control (c-i-con). After 48 hours, an MTT assay was performed. *P < .05 when compared to empty vector with caspase inhibitor control. %P < .05 when compared to Mxi1-0 with caspase inhibitor control. #P < .05 when compared to Mxi1 with caspase inhibitor control.