We demonstrate that a) at least six mitotic kinesins as well as CEP55 and PRC1 are direct targets of MMB in MDA-MB-231 breast cancer cells, b) suppression of KIF23 and PRC1 strongly suppressed proliferation of MDA-MB-231 cells, c) gene expression levels of PRC1 and KIF23 have prognostic value in terms of survival of breast cancer patients. This evidence concerns the gene CEP55 and breast cancer.