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In this paper we describe results using mRNA differential display reverse transcriptase PCR ( DDPCR ) to identify and isolate short cDNA sequence tags from thymocyte and prostate cells under various hormone conditions .
 prostate cells, reverse transcriptase, thymocyte, mRNA
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:
 prostate cells, reverse transcriptase, thymocyte, mRNA