- SH-SY5Y cells upon siRNA knock-down of PTPN1: ↑ EGF-induced protein tyrosine phosphorylation, ↑ cell proliferation. High expression of PTPN1 protein in neuroblastoma tumors associates with metastasis and poor prognosis (Nunes-Xavier et al., 2019b). This evidence concerns the gene EGF and neuroblastoma.