12842
Consistent with this feedback loop having a functional role in these cell models , pharmacological inhibitors of PI3K and ornithine decarboxylase potentiated each other in inhibiting tumour growth in a xenograft model .
 ornithine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ornithine