Direct targeting of epigenetic regulator Menin inhibits neuroblastoma growth

Abstract

Histone modifiers such as methyltransferases and demethylases have recently emerged as an attractive target to treat different cancers. Menin is a tumor suppressor protein and an essential oncogenic co‐factor of MLL1 COMPASS complex. Menin is a highly specific binding partner of the N‐terminus of MLL1 complex that have H3K4 methyltransferase activity. Menin‐MLL1 as an epigenetic regulator regulates the expression of target oncogenes, including HOXA, MEIS1, and AF9. Blocking menin‐MLL1 interaction destabilizes the COMPASS complex and hinders the oncogenic potential of cancer cells and cancer stem cells (CSCs). Neuroblastoma (NB) is an aggressive pediatric solid tumor develops during the early embryonic stage from extracranial sympathetic nervous system, and accounts for 10‐15% of all pediatric cancer‐related deaths. In the present study, we hypothesized that disrupting menin‐MLL1 interaction by using a specific small molecule inhibitor could disrupt COMPASS complex and overall inhibit NB growth, metastasis, and relapse. In the present study, we analyzed 1235 NB patients from different NB patient datasets and found that the upregulation of menin inversely correlate with overall survival of NB patients. We used six NB cell lines, including MYCN‐ amplified and ‐non‐amplified cell lines and performed cytotoxic assays. Results showed that inhibition of menin‐MLL1 interaction by MI‐503 significantly inhibits NB proliferation and colony formation capacity in contract to control treatments. Furthermore, MI‐503 significantly and in a dose‐dependent manner blocked NB cell cycle progression at S phase and enhanced apoptosis in treatment groups compared to controls. Additionally, we developed a 3D spheroidal tumor model for NB to mimic in vivo tumor conditions and tested the ability of MI‐503 in inhibiting tumor growth. Results showed significant inhibition of spheroidal tumor growth by enhancing tumor cell death in response to MI‐503 treatment. To further determine the effect of MI‐503 on inhibition of H3K4me3 levels, a key function of menin‐MLL1 COMPASS complex, we performed Western blot assays and observed a significant and dose dependent inhibition of H3K4me3 levels in response to MI‐503 treatment. Overall, our study highlights the role of menin‐MLL1 interaction in NB. Inhibition of menin‐MLL1 interaction by a specific small‐molecule inhibitor MI‐503 leads to the inhibition of epigenetic regulator functions and inhibits NB growth. Our future efforts will focus on further elucidating the role of menin in NB and to develop effective therapeutic strategies incorporating epigenetic inhibitors for NB patients.