From the genes that appeared in multiple expression signatures, we selected two, MAD2L1 (Mitotic Arrest Deficient 2-like 1) and BUB1 (Budding Uninhibited by Benzimidazoles 1), for further validation of their associations with patient survival in our own and other studies, as well as for in vitro evaluation of their biological involvements in breast cancer. Here, MAD2L1 is linked to breast cancer.