MYCN and neuroblastoma: We analyzed PLK4 expression across five neuroblastoma (NB) cell lines with varying malignant potential: MYCN-amplified, RA-sensitive SK-N-BE(2) and IMR-32; MYCN-non-amplified, RA-sensitive SK-N-SH and SH-SY5Y; and MYCN-non-amplified, RA-insensitive SK-N-AS.