PTPN5 and neuroblastoma: Interestingly, a distinct pattern of PTPRR, PTPN5, and PTPN7 mRNA expression was observed in human neuroblastoma cell lines upon retinoic acid differentiation, with down-regulation of PTPN5 and up-regulation of PTPN7 and, to a lesser extent, PTPRR (Figure 2).