7674
Signaling through HLA class I molecules induced cyclin E -associated kinase activity within 4 h in quiescent endothelial cells , and appeared to mediate the inactivation of Rb .
 quiescent endothelial cells, HLA class I molecules, cyclin E, Rb
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:
 quiescent endothelial cells, HLA class I molecules, cyclin E, Rb