Tubeimoside-I sensitizes temozolomide-resistant glioblastoma cells to chemotherapy by reducing MGMT expression and suppressing EGFR induced PI3K/Akt/mTOR/NF-κB-mediated signaling pathway

• Published in: Phytomedicine (Stuttgart) 2022-05, Vol.99, p.154016-154016, Article 154016
• Main Authors: Tang, Qingfa, Cao, Haihong, Tong, Ni, Liu, Yuanliang, Wang, Wanyu, Zou, Yuheng, Xu, Lanyang, Zeng, Zhiyun, Xu, Wei, Yin, Zhixin, Ma, Wenjuan, Wang, Qirui
• Format: Article
• Language: English
• Subjects: EGFR induced PI3K/Akt/mTOR/NF-κB signaling pathway; Genotoxicant; Glioblastoma multiforme; MGMT; Temozolomide resistance; Tubeimoside-I
• ISSN: 0944-7113; 1618-095X
• DOI: 10.1016/j.phymed.2022.154016

•Co-treatment of TBMS1 and TMZ synergistically induced apoptosis of TMZ-resistant glioblastoma cells.•TBMS1 sensitizes MGMT+ GBM cells to TMZ through diminishing MGMT expression and restraining EGFR induced PI3K/Akt/mTOR/NF-κB mediated pathway. Glioblastoma multiforme (GBM, World Health Organization [WHO] grade IV) is one of the malignant Central Nerve System (CNS) tumors with high incidence rate and poor prognosis. The use of alkylating agents, such as temozolomide (TMZ), has been the main method of cytotoxic therapy for glioma patients for decades. However, TMZ resistance may be one of the major reasons for treatment failure, so far. In searching for effective agents to reverse TMZ resistance, we found that Tubeimoside-I (TBMS1), a saponin from traditional Chinese medicine, Bolbostemma paniculatum (Maxim.) Franquet, showed activities of reversing TMZ resistance of GBM. However, the ability of TBMS1 enhancing the chemosensitivity of GBM has been rarely studied, and its underlying mechanisms remain unclear. This study purposes to reveal the synergistic effects and mechanism of TBMS1 and TMZ against TMZ-resistant GBM cells. CCK8 assay was used to investigate the anti-proliferative effects on grade IV glioblastoma human T98G and U118 MG cells. Cell proliferation was determined by EdU assay and clonogenic assay after TMZ plus TBMS1 treatment. Apoptosis was analyzed by flow cytometry. DNA damage and DNA Double Strand Break (DSB) were assessed by cleaved Poly (ADP-ribose) polymerase (PARP), γH2AX Foci Assay and Comet Assay, respectively. Expression of proteins associated with apoptosis and DNA repair enzymes were measured by Western blot analysis. The prognostic significance of key proteins of the epidermal growth factor receptor (EGFR) induced PI3K/Akt/mTOR/NF-κB signaling pathway was analyzed using GEPIA (http://gepia.cancer-pku.cn) and validated by Western blotting. Here we demonstrated that TBMS1 sensitized TMZ-resistant T98G and U118 MG glioblastoma cells to chemotherapy and exhibited promotion of apoptosis and inhibition on cell viability, proliferation and clone formation. Coefficient of drug in interaction (CDI) values showed a notable synergistic effect between TBMS1 and TMZ. Moreover, we observed that combination of TBMS1 and TMZ induced apoptosis was accompanied by robust DSB, γH2AX Foci formation and increasing cleaved PARP, as well as the heightened ratio of Bax/Bcl-2, cleavages of caspase-3 and caspase-9. In addition, the synergistic anti-glioma e