21635
In addition to known obstacles to beta cell proliferation , cytoplasmic - to - nuclear trafficking of G1 / S molecules may represent both an obstacle , as well as a therapeutic opportunity , for human beta cell expansion .
 None
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:  
Answer:
 None