7956
Cellular damage from ionizing radiation ( IR ) is in part due to DNA damage and reactive oxygen species , which activate DNA damage response ( DDR ) and cytokine signaling pathways , including the ataxia telangiectasia mutated ( ATM ) and transforming growth factor ( TGF ) beta / Smad pathways .
 Chemical: oxygen
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: oxygen 
Answer:
 Chemical: oxygen