2333
These p21 - E2F complexes , while present in young G1 cells at very low levels , were elevated in senescent cells .
 GENE: p21; GENE: E2F
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: p21; GENE: E2F