Forkhead box protein O3a promotes glioma cell resistance to temozolomide by regulating matrix metallopeptidase and β‑catenin

Abstract

Glioblastoma multiforme (GBM) is the most common type of malignant brain tumor. GBM is currently treated with temozolomide (TMZ), although patients often exhibit resistance to this agent. Although several mechanisms underlying the resistance of GBM to TMZ have been identified, the combination of these mechanisms is not sufficient to fully account for this phenomenon. Our previous study demonstrated that knocking down the Forkhead box protein O3a (FoxO3a) gene, a member of the FoxO subfamily of transcription factors, resulted in glioma cell sensitization to TMZ, accompanied by reduced levels of nuclear β-catenin. The aim of the present study was to specify how FoxO3a and β-catenin are implicated in glioma cell TMZ resistance. Using the U87 and U251 parental cell lines (also designated as sensitive cell lines) and corresponding resistant cell lines (U87-TR and U251-TR, generated by repeated TMZ treatments), coupled with a combined knockdown/overexpression strategy, it was revealed that FoxO3a or β-catenin overexpression in TMZ-treated U87 and U251 cells markedly increased cellular proliferation; co-expression of both FoxO3a and β-catenin resulted in the highest increase. Knockdown of either FoxO3a or β-catenin in U87-TR and U251-TR cells led to a significant decrease in cell viability, which was rescued by the re-expression of FoxO3a in FoxO3a-knockdown cells. Subsequent experiments demonstrated that, in U87-TR and U251-TR cells, FoxO3a knockdown significantly reduced the protein levels of matrix metallopeptidase (MMP)9, while overexpression of FoxO3a in U87 and U251 cells enhanced the nuclear accumulation of β-catenin, concomitantly with an increase in MMP9 levels. Furthermore, MMP9 knockdown markedly reduced the levels of nuclear β-catenin. Collectively, the findings of the present study suggest that FoxO3a may regulate the nuclear accumulation of β-catenin by modulating MMP9 expression, thereby rendering glioblastoma cells resistant to TMZ, and may provide unique molecular insights into the mechanisms underlying the development of TMZ resistance in GBM.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

“…FOXO proteins (especially FOXO3a) were shown to compete with TCF for binding to β-catenin and suppress TCF transcriptional activity particularly under oxidative stress [ 211 ]. In line with the study conducted by Xu and colleagues [ 212 ], Sun et al demonstrated that in U87 and U251 GBM cells resistant to TMZ, overexpression of FOXO3a positively regulates the amount of nuclear β-catenin via governing MMP9 expression [ 213 ]. In contrast, Lu et al have shown that miR-370 as a downregulated tumor suppressor miRNA by targeting 3′ UTR of β-catenin mRNA, suppresses its expression in astrocytoma and GBM cells and subsequently promoting FOXO3a nuclear accumulation, suppressing cancer cell proliferation [ 214 ].…”

OSI‐027 inhibits the tumorigenesis of colon cancer through mediation of c‐Myc/FOXO3a/PUMA axis

“…In addition, FoxO3a is a member of the FOXO family that plays a vital role in cell growth and cancer progression (Y. Cao, Li, et al, 2021;D. Sun et al, 2021).…”

“…c‐Myc is the important regulator in the cellular process, including the tumorigenesis of cancers (Xia et al, 2022; X. Yang, Yang, et al, 2021). In addition, FoxO3a is a member of the FOXO family that plays a vital role in cell growth and cancer progression (Y. Cao, Li, et al, 2021; D. Sun et al, 2021). Previous studies have found that FOXO3a downregulation and c‐Myc activation could promote the malignant behaviors of colon cancer cells (Karki et al, 2017; Liu et al, 2018).…”