30213
On the contrary , the expression of p - Smad2 / 3 , a marker for TGF - beta / Smad signaling , reduced significantly in BMP - 7 - treated groups compared with silica groups ( P < 0 . 05 ) .
 silica
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 silica