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Protein kinase B ( c-Akt ), phosphatidylinositol 3-kinase , and STAT5 are activated by erythropoietin ( EPO ) in HCD57 erythroid cells but are constitutively active in an EPO -independent, apoptosis -resistant subclone ( HCD57-SREI cells ).
 EPO, HCD57-SREI cells, phosphatidylinositol 3-kinase, c-Akt, erythropoietin, HCD57 erythroid cells, EPO -independent, apoptosis -resistant subclone, STAT5, EPO, Protein kinase B
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 EPO, HCD57-SREI cells, phosphatidylinositol 3-kinase, c-Akt, erythropoietin, HCD57 erythroid cells, EPO -independent, apoptosis -resistant subclone, STAT5, EPO, Protein kinase B