Protein-Tyrosine-Phosphatase article 8 priority journal 8 1-Phosphatidylinositol 3-Kinase 6 Phosphorylation 6 controlled study 6 enzyme activity 6 human 6 protein expression 6 signal transduction 6 4 nitrophenylphosphatase 4 Cell Line 4 Cell Survival 4 Down-Regulation 4 Erythropoietin 4 Gene Expression Regulation, Enzymologic 4 Janus Kinase 2 4 Janus kinase 2 4 Protein Tyrosine Phosphatase 1B 4 Signal Transduction 4 Tyrphostins 4 UT-7 cell line 4 Western blotting 4 enzyme phosphorylation 4 erythropoietin 4 feedback system 4 human cell 4 hydrolysis 4 phosphatidylinositol 3 kinase 4 protein function 4