21104
Previous studies established that stimulation of ErbB receptors in breast cancer cells activates Rac1 and enhances motility via the Rac - guanine nucleotide exchange factor P - Rex1 .
 Chemical: guanine nucleotide
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: guanine nucleotide 
Answer:
 Chemical: guanine nucleotide