MYCN and neuroblastoma: To define optimal spheroid culture conditions for various NB cell lines, we seeded increasing cell numbers from 10 to 1000 cells per well of two MycN-non-amplified (MNN) NB cell lines (SK-N-SH and SK-N-AS) in round-bottom ULA 96-well plates and monitored spheroid growth over time by taking phase-contrast images (Figure 1a); we determined the sizes of NB spheroids by measuring the diameters after 3, 7, 10 and 14 days (Figure 1b).