IGF1 and breast cancer: Phosphorylation of eIF2α, a downstream effector of the EnR stress response, was increased in human breast cancer cell lines, HCC70 and MCF7, but not MDA-MB-231 after IGF-1R inhibition (Fig. 2e), while total eIF2α was unchanged, suggesting inhibition of IGF signaling activates EnR stress signaling in breast cell lines with low basal EnR stress.