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Rho GTPase-activating protein 18 (MacGAP) (Rho-type GTPase-activating protein 18)


Stress-Induced Premature Senescence Promotes Proliferation by Activating the [i]SENEX[/i] and p16 /Retinoblastoma (Rb) Pathway in Diffuse Large B-Cell Lymphoma

Cellular senescence has been thought to be an important barrier to tumor formation. Recent studies have shown that stress-induced premature senescence (SIPS) can promote partial tumor invasion, but how SIPS affects diffuse large B-cell lymphoma (DLBCL) remains inconclusive. This study aimed to address that issue. The immunophenotype of the LY8 cell line was measured with flow cytometry. SIPS induced by tert-butyl hydroperoxide (tBHP) was detected by senescence β-galactosidase staining. Cell proliferation was analyzed with CCK8 and expression levels of ARHGAP18 ([i]SENEX[/i] gene-encoding protein), p16/p21, and Rb/pRb were measured with western blot. LY8 cells were transfected with [i]SENEX[/i]-SiRNA/NC and verified by western blot. Our results suggested that the immunophenotype of the LY8 cell line is CD19-, CD20-, and CD10-positive and the immunoglobulin light chain is the kappa type. The cellular senescence model of DLBCL could be successfully induced by 30 μM tBHP. ARHGAP18, p21, p16, and Rb protein levels were significantly increased but the level of pRb expression was decreased in the SIPS group compared with other groups. Meanwhile, the proliferation rate was increased in the SIPS group more than other tBHP groups. Furthermore, the expressions of p21 and p16 were significantly decreased in the [i]SENEX[/i]-SiRNA group compared with the negative control group. SIPS formation activates ARHGAP18 and the p16/Rb pathway and promotes DLBCL cell proliferation. Furthermore, [i]SENEX[/i] activates the p16 pathway in DLBCL. SIPS promotes proliferation by activating [i]SENEX[/i] and the p16/Rb pathway in DLBCL. [i]SENEX[/i]-related SIPS may serve as an important target for relapsed/refractory DLBCL therapy.

MeSH Terms

  • Cell Culture Techniques
  • Cell Line, Tumor
  • Cell Proliferation
  • Cellular Senescence
  • Cyclin-Dependent Kinase Inhibitor p16
  • Humans
  • Lymphoma, Large B-Cell, Diffuse
  • Retinoblastoma
  • Transfection


  • Stress-induced premature senescence
  • Proliferation
  • p16
  • Rb/pRb
  • Diffuse large B-cell lymphoma

Caveolae control the anti-inflammatory phenotype of senescent endothelial cells.

Senescent endothelial cells (EC) have been identified in cardiovascular disease, in angiogenic tumour associated vessels and in aged individuals. We have previously identified a novel anti-inflammatory senescent phenotype of EC. We show here that caveolae are critical in the induction of this anti-inflammatory senescent state. Senescent EC induced by either the overexpression of ARHGAP18/SENEX or by H₂O₂ showed significantly increased numbers of caveolae and associated proteins Caveolin-1, cavin-1 and cavin-2. Depletion of these proteins by RNA interference decreased senescence induced by ARHGAP18 and by H₂O₂. ARHGAP18 overexpression induced a predominantly anti-inflammatory senescent population and depletion of the caveolae-associated proteins resulted in the preferential reduction in this senescent population as measured by neutrophil adhesion and adhesion protein expression after TNFα treatment. In confirmation, EC isolated from the aortas of CAV-1(-/-) mice failed to induce this anti-inflammatory senescent cell population upon expression of ARHGAP18, whereas EC from wild-type mice showed a significant increase. NF-κB is one of the major transcription factors mediating the induction of E-selectin and VCAM-1 expression, adhesion molecules responsible for leucocyte attachment to EC. TNFα-induced activation of NF-κB was suppressed in ARHGAP18-induced senescent EC, and this inhibition was reversed by Caveolin-1 knock-down. Thus, out results demonstrate that an increase in caveolae and its component proteins in senescent ECs is associated with inhibition of the NF-kB signalling pathway and promotion of the anti-inflammatory senescent pathway.

MeSH Terms

  • Animals
  • Anti-Inflammatory Agents
  • Carrier Proteins
  • Caveolae
  • Caveolin 1
  • Cellular Senescence
  • GTPase-Activating Proteins
  • Gene Knockdown Techniques
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Inflammation
  • Mice
  • NF-kappa B
  • Phenotype
  • Phosphate-Binding Proteins
  • RNA-Binding Proteins
  • Transcription Factor AP-1
  • Up-Regulation


  • ARHGAP18
  • caveolae
  • cellular senescence
  • endothelial cells
  • inflammation

Transcript profile of cellular senescence-related genes in Fuchs endothelial corneal dystrophy.

Fuchs endothelial corneal dystrophy (FECD) is a genetically heterogeneous disease. Hypothesizing that cellular senescence may be relevant in FECD pathogenesis, genetically undifferentiated late-onset FECD endothelial samples were analyzed to identify common changes of specific senescence-related transcripts. Total RNA was extracted from 21 FECD endothelial samples retrieved from patients undergoing lamellar keratoplasty due to clinically diagnosed end-stage FECD and from 12 endothelial samples retrieved from normal autopsy eyes. Taqman low density array (TLDA) cards were used to analyze differential expression of 89 cellular senescence-related transcripts. Result validation was performed using individual real-time PCR assays. TLDA-analysis demonstrated differential expression of 31 transcripts (fold-change >1.5; p < 0.05). Thereof, 27 showed significant up-regulation and 4 significant down-regulation. Markedly elevated mRNA-levels of the constitutively active and reactive oxygen species-generating enzyme NOX4 were found in all evaluable FECD samples. In addition, increased expression of CDKN2A and its transcriptional activators ETS1 and ARHGAP18 (SENEX) along with decreased expression of CDKN2A inhibitor ID1 were detected in FECD samples. Consistent over-expression of NOX4 in FECD endothelial samples suggests a role as pathogenic factor and as a potential new treatment target in FECD. Transcriptional up-regulation of the CDKN2A-pathway provides further evidence for increased cellular senescence in FECD endothelium.

MeSH Terms

  • Apoptosis
  • Cellular Senescence
  • Endothelium, Corneal
  • Eye Proteins
  • Fuchs' Endothelial Dystrophy
  • Gene Expression Regulation
  • Humans
  • Oxidative Stress
  • RNA, Messenger
  • Reactive Oxygen Species
  • Real-Time Polymerase Chain Reaction


  • CDKN2A
  • Cellular senescence
  • Corneal endothelium
  • Fuchs endothelial corneal dystrophy
  • NOX4
  • Oxidative stress
  • Pathogenesis