Then, formaldehyde-fixed, paraffin-embedded tissue blocks were prepared from xenograft tissue and cut into serial sections (3 μm) for examining the expression of p-AKT, p-ERK, and PCNA (mouse anti-PCNA anti- body: GeneTex Inc., Irvine, CA, USA) by immunohis- tochemistry with the streptavidin–peroxidase (S–P) kit (Fuzhou Maixin Biotechnology Development Co., Fuzhou, China). Each slice was enumerated under five fields of medium magnification (×400) to determine the proportion of positive cells.