To determine whether FOXM1B can be SUMOylated by SUMO1 in mammalian cells, MCF7 breast cancer and H1299 lung cancer cells were transiently transfected with HIS-FLAG tagged FOXM1B expression plasmids with or without HA-tagged SUMO1 (WT or AA mutant) expression plasmids. This evidence concerns the gene SUMO1 and breast cancer.