On the other hand, in a panel of GIST xenograft mouse models, Floris and colleagues [21] illustrated that homozygous PTEN loss was identified in the GIST-PSW (GIST biopsy tumor cell with KIT exon 11 mutation) and GIST882Ly (GIST cell line harboring homozygous KIT exon 13 mutation) xenografts, while heterozygous PTEN loss was observed in a GIST48 (GIST cell line carrying both KIT exon 11 and 17 mutation) xenograft. The gene discussed is KIT; the disease is gastrointestinal stromal tumor.