EIF2A and breast carcinoma: However, the present study demonstrates that in estrogen-dependent rapamycin-sensitive breast cancer MCF-7 cells as well as in triple negative rapamycin-insensitive MDA-MB-231 cells, inhibition of mTOR by rapamycin and by specific catalytic inhibitor (Ku-0063794) respectively, leads to increased phosphorylation of eIF2α.