Also, because the level of phosphorylated eIF2α is much higher and that of the total amount of the proteins was much lower in normal fibroblasts and breast cells than in MDA-MB-231 cells, the growth and proliferation of normal cells may be more tolerant to increased eIF2α phosphorylation than MDA-MB-231, and drugs that directly to increase phosphorylation of eIF2α [19,39] may differentially affect cancer cells by providing a similar sensitizing effect to that of vorinostat without triggering all of its downstream effectors, thus minimizing potential side effect. Here, EIF2A is linked to cancer.