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• FoxO1 knockdown reduced the expression of IL-7Rα. • Loss of FoxO1 gene suppressed the cell signaling transduction via IL-7Rα. • FoxO1 regulates the expansion of pre-B cells. Forkhead box O1 (FoxO1) has a crucial role in the early B cell development. To understand the functional importance of FoxO1 gene in the early B cell expansion, we established a FoxO1 knockdown model using 70Z/3 pre-B cell line. The FoxO1 knockdown 70Z/3 cells (70Z/3-KD cells) showed the down-regulated expression of interleukin 7 receptor α chain (IL-7Rα). Moreover, the signaling via IL-7Rα was significantly attenuated in the 70Z/3-KD cells, and this alteration was fully rescued by re-expression of FoxO1 gene. Compared to the mock cells, loss of FoxO1 reduced the growth rates in the 70Z/3-KD cells, and was fully rescued by reintroduction of FoxO1 gene. The expansion of pre-B cells (CD45R+CD43− fraction) was also reduced by the knockdown of FoxO1 gene. Indeed, FoxO1 induces accumulation in the p27-mediated G0/G1 phase arrest in 70Z/3 cells. FoxO1 bound to the Il7ra locus specifically and regulate the IL-7Rα transcription. In conclusion, FoxO1 regulates the expansion of pre-B cells by regulating the expression of IL-7Rα and its signal transduction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]