Negative regulation of miR-1275 by H3K27me3 is critical for glial induction of glioblastoma cells.

Jialuo Mai,Zhijie Chen,Yaqian Tan,Longxiang Sheng,Jingyi Wang,Bingzheng Lu,Jing Cai,Xincheng Liu,Wei Yin,Pengxin Qiu,Xingwen Su,Wenbo Zhu,Lin Cao,Jiankai Liang,Cui Guo,Yuan Lin,Ying Liu,Hongjiaqi Sun,Xiaozhi Yang,Jiayu Gu,Ke Sai,Fan Xing,Wanjun Lu,Chuntao Li,Zhu Zhu,Dongdong Xue,Yan Gao ,Ying Ouyang ,Shenghua Sun

doi:10.1002/1878-0261.12525

Abstract

Activation of the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway induces glial differentiation of glioblastoma (GBM) cells, but the mechanism by which microRNA (miRNA) regulate this process remains poorly understood. In this study, by performing miRNA genomics and loss‐ and gain‐of‐function assays in dibutyryl‐cAMP‐treated GBM cells, we identified a critical negative regulator, hsa‐miR‐1275, that modulates a set of genes involved in cancer progression, stem cell maintenance, and cell maturation and differentiation. Additionally, we confirmed that miR‐1275 directly and negatively regulates the protein expression of glial fibrillary acidic protein (GFAP), a marker of mature astrocytes. Of note, tri‐methyl‐histone H3 (Lys27) (H3K27me3), downstream of the PKA/polycomb repressive complex 2 (PRC2) pathway, accounts for the downregulation of miR‐1275. Furthermore, decreased miR‐1275 expression and induction of GFAP expression were also observed in dibutyryl‐cAMP‐treated primary cultured GBM cells. In a patient‐derived glioma stem cell tumor model, a cAMP elevator and an inhibitor of H3K27me3 methyltransferase inhibited tumor growth, induced differentiation, and reduced expression of miR‐1275. In summary, our study shows that epigenetic inhibition of miR‐1275 by the cAMP/PKA/PRC2/H3K27me3 pathway mediates glial induction of GBM cells, providing a new mechanism and novel targets for differentiation‐inducing therapy.

Highlights

Glioblastoma (GBM) is the most common and deadly cancer of the central nervous system (CNS) and is associated with a poor clinical prognosis (Wesseling and Capper, 2017)
Activation of the cyclic adenosine monophosphate (cAMP) signal pathway by cholera toxin or cAMP activator can induce differentiation of rat glioma cells and human glioma cells toward an astrocyte type (He al., 2011; Li al., 2007). dbcAMP, a cAMP analog, was reported to be used to trigger glial induction (Adornetto al., 2013; Hu al., 2008; Xing al., 2017), and we used it as a differentiation inducer in our research
The results showed that dbcAMP increased the activity of H3K27MTase and that inhibiting either protein kinase A (PKA) or EZH1/2 abrogated the H3K27MTase activation induced by dbcAMP (Fig. 5E), suggesting that polycomb repressive complex 2 (PRC2) activation is mediated by PKA

Summary

Introduction

Glioblastoma (GBM) is the most common and deadly cancer of the central nervous system (CNS) and is associated with a poor clinical prognosis (Wesseling and Capper, 2017). The major therapeutic strategy, which includes surgical resection, radiation, and chemical therapy, is usually applied as the standard medical management approach for patients with GBM. Even after this standard regiment, GBM patients have a median survival of only 12–15 s (Stupp al., 2005; Wen and Kesari, 2008). Differentiation therapy is a strategy that involves inducing malignant cells to differentiate toward relatively benign mature cells by applying specific chemicals or signaling agents (Leszczyniecka al., 2001). We reported that activation of the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway by cholera toxin can induce malignant glioma cell differentiation into benign astrocyte-like cells, which are characterized by proliferation arrest and glial fibrillary acidic protein (GFAP) expression (Li al., 2007). Elucidating the molecular mechanisms involved in glial induction may provide valuable insights into the underlying biological features of this disease and possible new therapeutic targets

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Conclusion