B. Western blot analysis of puromycin (Puro)-labeled fibroblasts (CAF, normal human mammary fibroblasts, WI-38, and NIH3T3) after 2-h starvation and EAA add-back in the presence or absence of cycloheximide (CHX). C. Western blot analysis of Puro-labeled fibroblasts cultured in growth medium. 