According to their tissue-specific expression, MYB and MYBL1 deregulations have been associated with certain specific cancer entities: MYB was shown to be involved in several types of leukemia, colon and breast cancer,11 whereas MYBL1 has been associated with Burkitt’s lymphoma and several types of leukemia.12 In contrast, MYBL2 deregulations occur in a broad spectrum of cancer entities as it is a central regulator of cell cycle progression, cell survival and cell differentiation in many tissue types (see ‘MYBL2 in cancer’ section). Here, MYBL1 is linked to breast cancer.