CDKN1A and neuroblastoma: Moreover, analysis of protein lysates of EGFP-positive and EGFP-negative subpopulations from both settings of the three NB cell lines showed that the p21CIP1/WAF1 protein levels were upregulated upon NBPF1 overexpression in NLF and SK-N-AS cells, in line with the observed G1 cell cycle block, but not in SH-SY5Y cells (Fig. 11).