CDKN1B and neoplasm: Since menin forms a transcriptional complex with MLL2 and RNA polymerase II, regulating p27Kip1 expression, inactivation of menin reduces p27-mRNA levels and a second hit event, as the occurrence ofV109G variant, potentially correlated with p27 protein degradation by p38JAB1, a protein promoting the degradation of this cyclin-dependent kinase inhibitor, may trigger exaggerated multiple tumor developments.