We established HT-29 human colorectal cells and MCF-7 breast cancer cells stably transfected with the pcDNA-CSE1L vector, a eukaryotic expression vector carrying the full-length human CSE1L cDNA to study the effect of increased CSE1L expression on cancer cell apoptosis induced by chemotherapeutic drugs [12,13]. This evidence concerns the gene CSE1L and breast cancer.