Metformin treatment reduces temozolomide resistance of glioblastoma cells

Abstract

It has been reported that metformin acts synergistically with temozolomide (TMZ) to inhibit proliferation of glioma cells including glioblastoma multiforme (GBM). However, the molecular mechanism underlying how metformin exerts its anti-cancer effects remains elusive. We used a combined experimental and bioinformatics approach to identify genes and complex regulatory/signal transduction networks that are involved in restoring TMZ sensitivity of GBM cells after metformin treatment. First, we established TMZ resistant GBM cell lines and found that the resistant cells regained TMZ sensitivity after metformin treatment. We further identified that metformin down-regulates SOX2 expression in TMZ-resistant glioma cells, reduces neurosphere formation capacity of glioblastoma cells, and inhibits GBM xenograft growth in vivo. Finally, the global gene expression profiling data reveals that multiple pathways are involved in metformin treatment related gene expression changes, including fatty acid metabolism and RNA binding and splicing pathways. Our work provided insight of the mechanisms on potential synergistic effects of TMZ and metformin in the treatment of glioblastoma, which will in turn yield potentially translational value for clinical applications.

Metformin as Potential Therapy for High-Grade Glioma

“…This effect was visible in both in vitro and in vivo experiments. Similar observations have been made for gliomas [48,49]. This applies to the inhibition of tumor cell proliferation as well as the inhibition of their differentiation and invasiveness [35,39,[50][51][52][53][54][55].…”

Coronarin D Induces Apoptotic Cell Death and Cell Cycle Arrest in Human Glioblastoma Cell Line

“…U-251 cells (1 × 10 6 cells/well) in 6-well plates with complete medium were incubated at 37 • C with 5% CO 2 for 24 h. Then cells were treated with a negative control (DMSO), Coronarin D (40 µM), and TMZ (used as positive control) for 24 h. TMZ was dissolved in DMSO to prepare a stock concentration of 1000 mM, which was further diluted in cell culture medium to working concentrations. The cells were exposed at 3 × IC 50 concentration values of TMZ for 24 h in DMEM (0.5% FBS) [49]. After washing with PBS (1 mL/well, twice), cells were lysed with lysis buffer (70 µL/well); Tris 50 mM pH 7.6-8, NaCl 150 mM, EDTA 5 mM, Na 3 VO 4 1 mM, NaF 10 mM, Na pyrophosphate 10 mM, and 1% NP-40 and supplemented with a cocktail of inhibitors (DTT-Dithiothreitol, leupeptin hemisulfate, aprotinin, PSMF-Phenylmethylsulfonyl fluoride, and EDTA) for 1 h, followed by centrifugation (4 • C, 15 min, 13,000 rpm).…”

Repurposing old drugs in oncology: Opportunities with clinical and regulatory challenges ahead

“…For example, metformin restores crizotinib sensitivity in crizotinib‐resistant human lung cancer cells through inhibition of the IGF‐1R signalling pathway . Metformin has also been reported to reduce temozolomide resistance in glioblastoma cell lines . Paradoxically, a number of TKIs and mTOR inhibitors used in oncology are associated with drug‐induced hyperglycaemia …”

“…36 Metformin has also been reported to reduce temozolomide resistance in glioblastoma cell lines. 37 Paradoxically, a number of TKIs and mTOR inhibitors used in oncology are associated with drug-induced hyperglycaemia. 20 Given their structural and pharmacological similarities, it is not altogether surprising that phenformin, through regulation of IGF-1/ IGF-1R-mediated pathway, has also been shown to have potential anticancer activity.…”