1521
Recent studies have demonstrated that tumor cells treated with antibodies specific for beta ( 2 ) - microglobulin ( beta ( 2 ) M ) or major histocompatibility complex ( MHC ) class I molecules undergo apoptosis in vitro and in vivo ( mouse models ) .
 Anatomy: tumor cells
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Anatomy 
Text: {0} 
Answer:
 Anatomy: tumor cells