A pathway depicting the alterations in p27 expression in MEN1 and/or MEN4 that lead to tumorigenesis. Menin, encoded by MEN1, regulates the expression of p27 by forming a transcriptional activation complex with methyltransferase (MLL2) and RNA polymerase II (Pol III). Menin inactivation (MEN1 mutation) leads to decreased p27 expression. Mutations in CDKN1B, either solely or with MEN1 as a second germline hit, leads to a greater decrease in expression of p27 protein, triggering neoplasia.