10456
Therefore, we have constructed a single cDNA that encodes a single-chain protein , called Flexi-12 , which retains all of the biological characteristics of recombinant IL-12 ( rIL-12 ).
 cDNA, IL-12, single-chain protein, rIL-12, Flexi-12
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:
 cDNA, IL-12, single-chain protein, rIL-12, Flexi-12