The Natural Flavonoid Galangin Elicits Apoptosis, Pyroptosis, and Autophagy in Glioblastoma

Yang Kong; Zichao Feng; Anjing Chen; Qichao Qi; Mingzhi Han; Shuai Wang; Yulin Zhang; Xin Zhang; Ning Yang; Jiwei Wang; Bin Huang; Qing Zhang; Guo Xiang; Wenjie Li; Di Zhang; Jian Wang; Xingang Li

doi:10.3389/fonc.2019.00942

The Natural Flavonoid Galangin Elicits Apoptosis, Pyroptosis, and Autophagy in Glioblastoma

Front Oncol. 2019 Sep 27:9:942. doi: 10.3389/fonc.2019.00942. eCollection 2019.

Authors

Yang Kong^{1

2}, Zichao Feng^{1

2

3}, Anjing Chen^{1

2}, Qichao Qi^{1

2}, Mingzhi Han^{1

2

3}, Shuai Wang^{1

2}, Yulin Zhang^{1

2}, Xin Zhang¹, Ning Yang^{1

2}, Jiwei Wang^{1

2}, Bin Huang^{1

2}, Qing Zhang^{1

2}, Guo Xiang^{1

2}, Wenjie Li^{1

2}, Di Zhang^{1

2}, Jian Wang^{1

2

3}, Xingang Li^{1

2}

Affiliations

¹ Department of Neurosurgery, Qilu Hospital of Shandong University and Institute of Brain and Brain-Inspired Science, Shandong University, Jinan, China.
² Shandong Key Laboratory of Brain Function Remodeling, Jinan, China.
³ Department of Biomedicine, University of Bergen, Bergen, Norway.

Abstract

Galangin (GG), a flavonoid, elicits a potent antitumor activity in diverse cancers. Here, we evaluated the efficacy of GG in the treatment of human glioblastoma multiforme (GBM) and investigated the molecular basis for its inhibitory effects in the disease. GG inhibited viability and proliferation of GBM cells (U251, U87MG, and A172) in a dose-dependent manner (IC₅₀ = 221.8, 262.5, 273.9 μM, respectively; P < 0.001; EdU, ~40% decrease at 150 μM, P < 0.001), and the number of colonies formed was significantly reduced (at 50 μM, P < 0.001). However, normal human astrocytes were more resistant to its cytotoxic effects (IC₅₀ >450 μM). Annexin-V/PI staining was increased indicating that GG induced apoptosis in GBM cells (26.67 and 30.42%, U87MG and U251, respectively) and associated proteins including BAX and cleaved PARP-1 were increased (~3×). Cells also underwent pyroptosis as determined under phase-contrast microscopy. Knockdown of gasdermin E (GSDME), a protein involved in pyroptosis, alleviated pyroptosis induced by GG through aggravating nuclear DNA damage in GBM cells. Meanwhile, fluorescent GFP-RFP-MAP1LC3B puncta associated with autophagy increased under GG treatment, and transmission electron microscopy confirmed the formation of autophagic vesicles. Inhibition of autophagy enhanced GG-induced apoptosis and pyroptosis in GBM cells. Finally, in an orthotopic xenograft model in nude mice derived from U87MG cells, treatment with GG in combination with an inhibitor of autophagy, chloroquine, suppressed tumor growth, and enhanced survival compared to GG monotherapy (P < 0.05). Our results demonstrated that GG simultaneously induces apoptosis, pytoptosis, and protective autophagy in GBM cells, indicating that combination treatment of GG with autophagy inhibitors may be an effective therapeutic strategy for GBM.

Keywords: apoptosis; autophagy; galangin; glioblastoma; pyroptosis.