BIS targeting induces cellular senescence through the regulation of 14-3-3 zeta/STAT3/SKP2/p27 in glioblastoma cells

Abstract

Cellular senescence is an important mechanism for preventing tumor progression. The elevated expression of Bcl-2-interacting cell death suppressor (BIS), an anti-apoptotic and anti-stress protein, often correlates with poor prognosis in several cancers including glioblastoma; however, the role of BIS in the regulation of senescence has not been well defined. Here, we describe for the first time that the depletion of BIS induces G1 arrest and cellular senescence through the accumulation of p27 that is independent of p53, p21 or p16. The increase in p27 expression in BIS-depleted cells was attributable to an impairment of the ubiquitin-mediated degradation of p27, which was caused by a decrease in S-phase kinase-associated protein 2 (SKP2) at the transcriptional level. As an underlying molecular mechanism, we demonstrate that the loss of activity of signal transducer and activator of transcription 3 (STAT3) was specifically linked to the suppression of SKP2 expression. Despite a reduction in phospho-STAT3 levels, total STAT3 levels were unexpectedly increased by BIS depletion, specifically in the insoluble fraction. Our results show that 14-3-3ζ expression is decreased by BIS knockdown and that 14-3-3ζ depletion per se significantly induced senescence phenotypes. In addition, the ectopic expression of 14-3-3ζ blocked senescence caused by BIS depletion, which was paralleled with a decrease in insoluble STAT3 in A172 glioblastoma cells. These findings indicate that the impairment of the protein quality control conferred by BIS and/or 14-3-3ζ is critical for BIS depletion-induced senescence. Moreover, BIS knockdown also induced senescence along with an accumulation of total STAT3 and p27 in several different cell types as well as embryonic fibroblasts derived from Bis-knock out mice with/without variations in 14-3-3ζ levels. Therefore, our findings suggest that a downregulation of BIS expression could serve as a potential strategy for restricting tumor progression via an induction of senescence through the regulation of STAT3/SKP2/p27 pathway.

BIS-mediated STAT3 stabilization regulates glioblastoma stem cell-like phenotypes

“…Previously, we observed that BIS formed a complex with STAT3 in A172 cells under normal monolayer conditions [36]. Here, to investigate whether BIS and STAT3 interaction is involved in the induction of GSC-like phenotypes, we performed immunoprecipitation with a BIS polyclonal antibody or a STAT3 monoclonal antibody using the lysates from monolayer cells or spheres of A172.…”

“…The si-CTL (5′-CCUACGCCACCAAUUUCGU-3′) and si-BIS (5′-AAGGUUCAGACCAUCUUGGAA-3′) were purchased from Bioneer (Daejeon, Korea). STAT3 overexpression was performed as described previously [36]. …”

Soluble Egg Antigens of Schistosoma japonicum Induce Senescence of Activated Hepatic Stellate Cells by Activation of the FoxO3a/SKP2/P27 Pathway

“…Since P27, the cell cycle inhibitor, plays an important role in cellular senescence and SKP2 could cause a decrease in the level of P27 expression [13, 20], we next verified whether P27 signaling pathway is implicated in the progress of LX-2 senescence. As illustrated in Fig 1, Western blot analysis showed that SEA markedly increased the expression of P27, but decreased the SKP2 protein level.…”

Protein Acyltransferase DHHC3 Regulates Breast Tumor Growth, Oxidative Stress, and Senescence

“…Regarding STAT3, elevated tyrosine phosphorylation is not only oncogenic, but also may be suppressive by multiple potential mechanisms (ref. 31 and references within), including induction of cell senescence (32, 33). …”