Synergism of Temozolomide, Metformin, and Epigallocatechin Gallate Promotes Oxidative Stress-Induced Apoptosis in Glioma Cells

Abstract

Aim: To study the synergistic anti-glioma efficacies of Temozolomide, Metformin and Epigallocatechin Gallate in U87MG and C6 glioma cells. Background: Glioblastoma (GBM) is the most malignant and invasive tumor of the central nervous system. The current standard treatment comprises surgical resection, followed by adjuvant radiotherapy and chemotherapy employing temozolomide (TMZ). Yet the survival rates for GBM patients is very low. Hence there is a need for new treatment regimes Objective: This study was aimed to unravel the synergistic anti-tumor potential of a biguanide drug, Metformin (MET) and a polyphenol, Epigallocatechin gallate (EGCG) to enhance the anti-GBM efficacy of the standard drug. Methods: Anti-proliferative effect of TMZ, MET and EGCG, individually and in combination was elucidated in U87MG (human) and C6 (rat) glioma cells using MTT assay and combination index was used to determine synergism. Cytotoxicity of the drugs was performed in HEK293T noncancerous cells. Apoptotic morphological changes in the cells were observed by AO/EtBr staining. Further, the effect of drugs on antioxidant and apoptotic genes (SOD, CAT, Nrf-2, Caspase-9 and Bcl-2) were evaluated using qRT-PCR and the protein levels of Nrf-2 and Caspase-9 was evaluated using ELISA. Results: The triple-drug combination (TMZ+ MET+ EGCG) synergistically inhibited the proliferation of U87MG and C6 glioma cells in a dose-dependent manner and promoted the apoptosis of glioma cells. The triple-drug combination significantly up-regulated the expression of antioxidant and apoptotic genes and induced oxidative stress suggesting a shift in equilibrium towards apoptosis. Conclusion: MET and EGCG in combination with TMZ synergistically promoted oxidative stress induced apoptosis in glioma cells. Hence, the combination of TMZ, MET and EGCG may be therapeutically exploited for improving the clinical outcomes of patients with GBM.

A combination of metformin and epigallocatechin gallate potentiates glioma chemotherapy in vivo

“…This study was conducted on nine series of experimental groups (n = 48), namely, Group I: Normal rats without tumor induction (Control “C”) (n = 3); Group II: Tumor-control (TC) (n = 3); Group III: T-treated glioma-induced rats “(T)” (n = 6); Group IV: M-treated glioma-induced rats “(M)” (n = 6); Group V: E-treated glioma-induced rats “(E)” (n = 6); Group VI: TM-treated glioma-induced rats (TM) (n = 6); Group VII: TE-treated glioma-induced rats (TE) (n = 6); Group VIII: ME-treated glioma-induced rats (ME) (n = 6) and Group IX: TME-treated glioma-induced rats (TME) (n = 6) as shown in Figure 1A . The dosage of the drugs, either alone or in combination, to be administered to the rats were selected based on our in vitro data and previous studies in glioma ( Fernandes et al, 2017 ; Yu et al, 2017 ; Piwowarczyk et al, 2020 ; Kuduvalli et al, 2021 ).…”

Inhibitory Mechanism of Combined Hydroxychavicol With Epigallocatechin-3-Gallate Against Glioma Cancer Cell Lines: A Transcriptomic Analysis

“…The purpose of combination therapy is to achieve a synergistic therapeutic effect using lower doses to lessen the toxicity of each agent, and to slow down the induction of drug resistance ( Chou, 2010 ; Zhao et al, 2020 ) since multiple signal pathways are targeted during the treatment. Previous research found that EGCG increased the efficacy of temozolomide and metformin in U87MG cells and rat C6 glioma cell lines, indicating that EGCG might be a useful adjuvant for cancer chemoprevention ( Kuduvalli et al, 2021 ). Recent literature suggests that HC synergizes with buthionine sulfoximine (BSO), a glutathione synthesis inhibitor to eliminate chronic myeloid leukemic (CML) cells through the GSH-ROS-JNK-ERK-iNOS mediated pathway ( Chowdhury et al, 2013 ) and reports have suggested that HC may be developed as a single-agent chemotherapeutic drug or as an adjuvant ( Gundala et al, 2014 ).…”

A combination of Metformin and Epigallocatechin Gallate Potentiates Glioma Chemotherapyin vivo

“…In this context, employing drug repurposing approach, we had attempted to trigger apoptosis in glioma via ROS-mediated inactivation of PI3K/AKT/mTOR pathway (Yang et al, 2020). This was on grounds of our previous study, which proved that M and E synergistically enhanced the anti-glioma efficacy of T on C6 murine glioma and U-87 MG human glioblastoma cells by alleviating oxidative stress (Kuduvalli et al, 2021). Underpinning this idea, the current study was carried out to gain insight if the triple-drug combination (TME) could induce oxidative stress-mediated deactivation of PI3K/AKT/mTOR pathway and promote apoptosis in vivo.…”

“…This study was conducted on nine series of experimental groups (n=48), namely Group I: Normal rats without tumor induction (Control C) (n=3); Group II: Tumor-control (TC) (n=3); Group III: T-treated glioma-induced rats (T) (n=6); Group IV: M-treated glioma-induced rats (M) (n=6); Group V: E-treated glioma-induced rats (E) (n=6); Group VI: TM-treated glioma-induced rats (TM) (n=6); Group VII: TE-treated glioma-induced rats (TE) (n=6); Group VIII: ME-treated glioma-induced rats (ME) (n=6) and Group IX: TME-treated glioma-induced rats (TME) (n=6) as shown in Figure 1A . The dosage of the drugs, either alone or in combination, to be administered to the rats were selected based on our in vitro data and previous studies in glioma (Kuduvalli et al, 2021; Fernandes et al, 2017; Yu et al, 2017; Piwowarczyk et al, 2020).…”