15014
Here , we explore whether APE1 and reactive oxygen species ( ROS ) affect ERK signaling and cell cycle progression following Pb exposure .
 Chemical: oxygen; Chemical: Pb
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: oxygen; Chemical: Pb