tokens: To this end , SH - SY5Y cells were cotransfected with constructs encoding the luciferase gene driven by either the p21 / Waf1 or BAX p53RE and the constructs expressing the various p53s cloned from IGR - NB8 , SK - N - BE ( 2 ) , IGR - N - 91 , SK - N - AS and IGR - NB8 NB cells or p53DD , a dominant negative mutant of wt p53 ( 24 ) .