Haploinsufficient and predominant expression of multiple endocrine neoplasia type 1 (MEN1)-related genes, MLL, p27Kip1 and p18Ink4C in endocrine organs

► MEN1 is a autosomal dominantly inherited syndrome characterized by endocrine tumors. ► However, the mechanisms underlying the selectivity of tumors remain unclear. ► MEN1-related genes, MLL and p27, were predominantly expressed in the endocrine organs. ► Tissue-specific haploinsuffiency of MLL may lead to decreases in levels of p27 and p18.