Forced FoxO1:S²⁴⁹V expression suppressed glioma cell proliferation through G2/M cell cycle arrests and increased apoptosis

ABSTRACT

Objective: Forkhead box O1 (FoxO1) plays a crucial role in the development of many tumors. Cyclin D kinase (CDK) 1 could influence the nuclear export and activity of FoxO1 through phosphorylation of serine (S)²⁴⁹. However, the effects of S²⁴⁹ phosphorylation in the development of glioma remain unclear. The aim of the present study is to assess the function of FoxO1:S²⁴⁹V mutant, which was converted S²⁴⁹ phosphorylation site into valine (V) residues in the glioma development.

Methods: FoxO1-knockdown U251 glioma cells (U251-KD cells) were established by infection of retrovirus particles with FoxO1 siRNA and FoxO1 restored cells (FoxO1:S²⁴⁹V) were obtained by re-introduction of FoxO1:S²⁴⁹V cDNA. We detected mRNA expression by real-time PCR, and cell cycle arrest and apoptosis by flow cytometric assay, and cell proliferation by BrdU assay and CCK-8 assay. The protective effects of FoxO1:S²⁴⁹V were detected by the xenograft tumor formation assay.

Results: The FoxO1 mRNA expression was significantly decreased in the glioma specimens (n = 24). The U251-KD cells showed downregulation of p27 and Bim, while the phosphorylation of CDK1 was upregulated. FoxO1:S²⁴⁹V cells inhibited the phosphorylation of S²⁴⁹, and induced G2/M cell cycle arrest, following reduced cell growth and increased apoptosis. Moreover, FoxO1:S²⁴⁹V expression effectively inhibits the glioma growth.

Conclusion: Our findings suggest that the forced FoxO1:S²⁴⁹V suppressed the cell growth through G2/M cell cycle arrests and increased apoptosis in glioma.

KEYWORDS:

• FoxO1
• glioblastoma
• cell proliferation
• cell cycle
• apoptosis

Acknowledgment

We thank Prof. Aiguo Wang (Dalian Medical University) for excellent technical help with flow cytometry analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.

Author contributions

QQ designed research and wrote paper; XP, WL, NZ, HF, DZ performed and analyzed the experimental data; XP, ZL collected clinical samples; WL corrected paper. All authors approved the final version of the manuscript.

Supplementary material

Supplemental data for this article can be acessed here.

Additional information

Funding

This work was supported by the National Nature Science Foundation of China [31570797].