4860
In CV - 1 cells , cotransfection of the retinoid and estrogen receptors led to mutual inhibition of the other ' s activity , while an RA - dependent inhibition of ER activity was observed in breast cancer cells .
 retinoid and estrogen receptors, ER
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 retinoid and estrogen receptors, ER