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Spi-1/ PU.1 is a myeloid- and B-cell specific transcription factor which is also involved in Friend virus -induced murine erythroleukemia .
 Spi-1/ PU.1, myeloid- and B-cell specific transcription factor, PU.1, transcription factor
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:
 Spi-1/ PU.1, myeloid- and B-cell specific transcription factor, PU.1, transcription factor