Abstract 5120: Direct targeting of the COMPASS complex inhibits neuroblastoma growth by inhibiting cancer stem cells
Authors: Chilamakuri Rameswari , Agarwal Saurabh 
Published: March 2024

Abstract
Epigenetic regulator COMPASS Complex, a histone H3K4 methyltransferase has recently been shown to be involved in multiple cancers and attaining focus as a novel therapeutic target. High-risk neuroblastoma (NB) is a heterogeneous pediatric cancer with high mortality and relapse rates. The relapse of refractory cancer is shown to be driven by cancer stem cells (CSCs), which are maintained by epigenetic malfunctions. In the present study, we determined the effects of inhibiting the COMPASS complex on NB CSCs and overall NB growth. A high-throughput shRNA screening of methyltransferases and demethylases reveals the role of COMPASS complex partners MLL1 and Menin in NB proliferation. We found that both MLL1 and Menin are overexpressed in our previously identified CD114+ NB CSCs. Further, MEN1 (gene coding Menin) expression showed an inverse correlation with overall NB patient survival and cancer progression in a comprehensive analysis of 1235 primary NB patient data. Our ChIP results show that the CSF3R gene which codes for CD114 and maintains CD114+ NB CSCs, is regulated by the presence of high H3K4me3 activating marks. Further, we used MI-503 to inhibit MLL1-Menin interaction and also developed MEN1 stable knockdown and found that both strategies significantly inhibit H3K4me3 activity in NB, particularly at the CSF3R gene promoter. This led to decreased CSF3R expression and NB CSC levels. MI-503 significantly inhibits proliferation in different NB cell lines and primary patient-derived xenograft (PDX) lines, with minimal effect on non-cancerous fibroblasts. MI-503 significantly inhibits NB cell cycle progression at the S phase, induces apoptosis, and inhibits NB 3D spheroid growth and development. Interestingly, we overserved differential selectivity of MI-503 in inducing apoptosis and in blocking the cell cycle in NB CSCs in contrast to non-CSCs. MEN1 knockdown also inhibits NB proliferation and 3D spheroid growth. Furthermore, MI-503 in a dose-dependent manner synergistically sensitizes NB to chemotherapy doxorubicin and significantly inhibits NB proliferation and spheroid growth compared to either agent alone. Further, by using the NB xenograft in vivo tumor model, we established that MI-503 significantly inhibits NB tumor growth and tumor metastasis by directly inhibiting tumor NB CSCs, without any observed toxicities. Similar results of significantly reduced tumor growth, metastasis, and NB CSCs were shown by the MEN1 knockdown in vivo. Overall, our data show that the MLL1-Menin of the COMPASS complex directly activates the CSF3R gene to maintain NB CSCs and drive NB pathogenesis. Our data show that MI-503 or MEN1 knockdown leads to significant inhibition of NB growth by directly inhibiting NB CSCs in both in vitro and in vivo tumor models. Further developing these epigenetic-based therapeutic strategies and combining them with current therapies will pave the way for effectively managing NB.
Citation Format: Rameswari Chilamakuri, Saurabh Agarwal. Direct targeting of the COMPASS complex inhibits neuroblastoma growth by inhibiting cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5120.