CXXC5 and leukemia: In primary leukaemia cells, CXXC5 not only promotes differentiation, as mentioned above, but it also contributes to retinoid‐induced cell cycle arrest and cell death.3 CXXC5 is capable of promoting cell cycle arrest, DNA repair or apoptosis by activating the ATM‐p53 signaling axis.12 In addition, CXXC5 associates with FoxL2 to enhance its pro‐apoptotic activity in mammalian cells,70 and may mediate TNF‐α‐induced apoptosis of primary cortical neurons by associating with Smad proteins.49