CRISPR activation screen identifies GNAO1 as a driver of glioblastoma cell differentiation

Inducing tumor cell differentiation is a potential strategy for treating malignant cancers, including glioma. Here we perform a genome-scale CRISPR activation screen and identify that G Protein Subunit Alpha O1 (GNAO1) as a critical regulator of glioma cell differentiation. GNAO1 overexpression in combination with a small molecular inhibitor cocktail, including CHIR99021, SB431542, RepSox, and Y27632, markedly promotes neuronal differentiation of glioblastoma cells. GNAO1 is high expressed in normal neuronal tissues but low expressed in gliomas. High expression of GNAO1 is correlated with a better prognosis. GNAO1 overexpression decreases cell proliferation, cell migration, and orthotopic GBM tumor xenograft growth. GNAO1 overexpression activates neuronal differentiation pathways by down-regulation of transcript factor HES1, a key mediator of neuronal differentiation. GNAO1 recruits TRIM21 and increases TRIM21-mediated ubiquitination and degradation of CREB, leading to decreased p300-mediated H3K27ac levels of HES1 promoter and HES1 downregulation. In addition, GNAO1 mRNA stability is regulated by METTL3-regulated N6-methyladenosine (m6A). Overexpression of GNAO1 enhances glioblastoma response to Temozolomide (TMZ) and extends the survivals of animals bearing orthotopic GBM xenograft tumors. Our finding suggests that inducing neuronal differentiation of glioblastoma cells by engineering GNAO1 overexpression is a potential therapy strategy, which not only reduces tumor cell proliferation but also enhances tumor cell response to chemotherapy.