107906
Levonorgestrel stimulates the proliferation of MCF-7 breast cancer cells " in vitro " , an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 ( PGRMC1 ) .
 breast cancer
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 breast cancer