Importantly, Eg5 was found in a variety of malignant tumors—including cervical cancer (HeLa), hepatocellular carcinoma (HepG2), non-small cell lung cancer (A549), breast cancer (MDA-MB-231), and colorectal cancer (HCT116)—that were are overexpressed in, and barely detectable in, most normal tissues, highlighting their therapeutic potential. This evidence concerns the gene KIF11 and breast cancer.