To determine if in human cells PKR is also required for the induction of apoptosis in response to 5-FU treatment, PKR was down-regulated using shRNA against PKR in breast MCF-7 cancer cells and then, effectiveness of chemotherapeutic treatment was analyzed and compared to that observed after the treatment of the same cells expressing control dsRNA (Figure 2C). This evidence concerns the gene EIF2AK2 and cancer.