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SIX1 represses senescence and promotes SOX2-mediated cellular plasticity during tumorigenesis.

ABSTRACT: Six1 is a developmental transcriptional regulator frequently overexpressed in human tumors. Recent results show that SIX1 also acts as a repressor of cell senescence, an antiproliferative response with a key role in tumor suppression, among other physiological and pathological settings. Here, we set to study the impact of SIX1 gain of function in transformation and tumorigenesis of fibroblasts, in connection with senescence. Using transcriptomic, histological, and functional analyses in murine tumors and cells of fibroblast origin, we show that SIX1 has a strong pro-tumorigenic action in this model, linked to the repression of a senescence-related gene signature and the induction of an undifferentiated phenotype mediated, at least in part, by the regulation of the stemness factor Sox2. Moreover, functional analyses with human glioma cell lines also show that SIX1 controls SOX2 expression, senescence and self-renewal in this model. Collectively, our results support a general link of SIX1 with senescence and SOX2-mediated cell plasticity in tumors.

SUBMITTER: De Lope C

PROVIDER: S-EPMC6363751 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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SIX1 represses senescence and promotes SOX2-mediated cellular plasticity during tumorigenesis.

De Lope Cristina C Martín-Alonso Samara S Auzmendi-Iriarte Jaione J Escudero Carmen C Mulet Isabel I Larrasa-Alonso Javier J López-Antona Irene I Matheu Ander A Palmero Ignacio I

Scientific reports 20190205 1

Six1 is a developmental transcriptional regulator frequently overexpressed in human tumors. Recent results show that SIX1 also acts as a repressor of cell senescence, an antiproliferative response with a key role in tumor suppression, among other physiological and pathological settings. Here, we set to study the impact of SIX1 gain of function in transformation and tumorigenesis of fibroblasts, in connection with senescence. Using transcriptomic, histological, and functional analyses in murine t ...[more]

PMID: 30723235

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Project description:BackgroundNuclear factor-κB is a multi-subunit transcription factor that plays a central role in cellular senescence. We previously reported that an increase in the p52 subunit is seen in senescent cells and aged tissue. In the current work, we examined the mechanism by which p52 is activated and whether the increase in p52 promotes senescence.ResultsUsing both primary mouse embryonic fibroblasts (MEFs) and WI-38 human lung fibroblasts, we examined cells after serial passage and following prolonged culture. An increase in p52 was found in the nucleus relative to pre-senescent cells. The increase in p52 protein was not reflected by an increase in NFKB2 mRNA or by an increase in the abundance of upstream activating kinases, IKKα and NIK. To examine whether p52 promotes senescence, we over-expressed mature p52 in primary MEFs. Significantly more senescence was seen compared to control, a finding not seen with p52 mutated at critical DNA binding residues. In addition, blocking p52 nuclear translocation with the peptide inhibitor, SN52, decreased β-galactosidase (β-gal) formation. Subsequent filtration studies demonstrated that proteins in conditioned media (CM) were necessary for the increase in p52 and mass spectrometry identified S100A4 and cyclophilin A (CYPA) as potential factors in CM necessary for induction of p52. The requirement of these proteins in CM for induction of p52 was confirmed using depletion and supplementation studies. In addition, we found that activation of STAT3 signaling was required for the increase in p52. Finally, genome wide ChIP-sequencing analysis confirmed that there is an increase in p52 chromatin enrichment with senescence and identified several downstream factors whose expression is regulated by increased p52 binding.ConclusionsThese results demonstrate that p52 nuclear translocation is increased in senescent cells by factors in conditioned media and that mature p52 induces cellular senescence. The data are consistent with the prior observation that p52 is elevated in aged tissue and support the hypothesis that p52 contributes to organismal aging.

Project description:Making use of a previously described isogenic cancer stem cells and serum differentiated cultures we show that Sox2 controls developmental stated specific programs in glioblastoma. Glioblastoma cells were cultured as control and with SOX2 knockdown to identify the scope of SOX2 interactions. The SOX2 knockdown were accomplished using two knockdown technologies. The knockdown cells were compared to controls, early passage, and scrambled controls. For Sox2 knockdown in low passage 10% FBS cells, the following oligonucleotides targeting human SOX2 coding sequence, or non-silencing control sequence, were cloned into BLOCK-iT Pol II miR RNAi expression vectors (Invitrogen), before cell transfection into GBM monolayer cells using Lipofectamine-2000 (Invitrogen): Sox2miRNA1R:5’CCTGTGCATGGGCTGTCTGCGCTGTCAGTCAGTGGCCAAAACAGCGCAGATGCAGCCCATGCAC Sox2miRNA1F:5’TGCTGTGCATGGGCTGCATCTGCGCTGTTTTGGCCACTGACTGACAGCGCAGACAGCC Sox2miRNA2R:5’CCTGAACCCATGGAGAAGAGCCAGTCAGTCAGTGGCCAAAACTGGCTCTTGGCTCCATGGGTTC Sox2miRNA2F:5’TGCTGAACCCATGGAGCCAAGAGCCAGTTTTGGCCACTGACTGACTGGCTCTTCTCCATGGGTT miRNAnegative:5’GAAATGTACTGCGCGTGGAGACGTTTTGGCCACTGACTGACGTCTCCACGCAGTACATTT Sox2 knockdown in neurospheres: GIPZ Lentiviral shRNAmir constructs targeting human Sox2 (clones V3LHS_404430 and V3LHS_404432) and non-silencing control (RHS4346) were obtained (Thermo Scientific Open Biosystems) and lentivirus were prepared according to the manufacturer’s instructions. Sox2 ectopic expression: Sox2 cDNA was subcloned from pCMV6-XL5-NM_002106.2 (Origene) into pcDNA 3.1 mammalian expression vector (Invitrogen), under control of constitutive CMV promoter. Plasmid DNA constructs were stably transfected into GBM monolayer cells using Lipofectamine-2000 (Invitrogen). Control Glioblastoma cells cultured as neurospheres and monolayer early passage are compared to multiple shRNA SOX2 knockdown and multiple miR knockdown cell cultures. A total of 8 samples are analyzed for significant fold change genes identifying gene-gene interactions associated with the SOX2 knockdown. High fold change genes are grouped in lists to be analyzed for network-pathway enrichment. Overlap of significant gene list for each method were analyzed.

Dataset Information

SIX1 represses senescence and promotes SOX2-mediated cellular plasticity during tumorigenesis.

Publications

SIX1 represses senescence and promotes SOX2-mediated cellular plasticity during tumorigenesis.

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