IRF1 and neuroblastoma: To obtain direct evidence for this, the three NB cell lines SH-SY5Y, SK-N-BE(2) and SK-N-BE(2)c, which are particularly depressed in MHC-I expression, were single-transfected and double-transfected with expression vectors encoding IRF1, IRF2, and the NF-kB p65 cDNAs (Fig. 4A).