11871
Through two novel mechanisms , Arf inhibits the oncoprotein Hdm2 , a negative regulator of p53 .
 Arf, oncoprotein Hdm2, p53
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 Arf, oncoprotein Hdm2, p53