Repression of ARNT2 Maintains Stemness and Limits Differentiation of Glioblastoma Cells
To facilitate tumor growth, cancer cells activate pathways that enhance cell proliferation and suppress pathways responsible for cell differentiation. While the pathways involved in metabolic reprogramming and cell cycle progression in tumors have been extensively studied and understood, knowledge regarding the pathways that influence the differentiation status of cancer cells is limited. Our  study  characterizes  a  new  mechanism  regulating  the  balance  between  proliferation  and differentiation involving the repression of the neuronal-specific transcription factor ARNT2 by the MYC oncogene.  We found that MYC represses the transcription of ARNT2 via the activity of the polycomb complex 2. ARNT2 is reduced in glioblastoma and its levels are inversely correlated with patient survival. Using in vitro and in vivo models, we demonstrate that knocking out ARNT2 has no effect on the growth of glioblastoma cells in vitro, but dramatically increases glioblastoma cell growth in vivo, and overexpression of ARNT2 blunts the growth of fully transformed glioblastoma cells in vivo, with no effects in vitro. Mechanistically, we also confirmed that ARNT2 is required for neuronal differentiation including of human pluripotent stem cells. Our findings provide new insights into the complex mechanisms used by oncogenes to limit differentiation in cancer cells and define ARNT2 as a potential tumor suppressor gene in glioblastoma. Overall design: To investigate the functions of ARNT2 in glioblastoma proliferation and differentiation, we established LN229 cell lines with ARNT2 knocked out by CRISPR.