4074
Chloramphenicol acetyltransferase ( CAT ) activities directed by 5' upstream promoter were detected preferentially in perforin-expressing cell lines .
 CAT, Chloramphenicol acetyltransferase, perforin-expressing cell lines, 5' upstream promoter
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:
 CAT, Chloramphenicol acetyltransferase, perforin-expressing cell lines, 5' upstream promoter