Ikaros and its interacting partner CtBP target the metalloprotease ADAMTS10 to modulate pituitary cell function

C-terminal of E1A binding protein 1 enhances the migration of gastric epithelial cells and has a clinicopathologic significance in human gastric carcinoma

Background

Recent studies have claimed that the C-terminal of E1A binding proteins (CtBPs) influence tumorigenesis through participating in cell signal transduction in various human tumors. However, the detailed expression profiles of CtBP isoforms in human gastric cancer (GC) and the molecular mechanisms of CtBP involvement in tumor cell phenotypes warrant further investigation.

Materials and methods

The expression of CtBPs in GC cell lines and a human gastric epithelial cell line were explored via RT-qPCR and Western blotting assays. Moreover, the expression profiles of CtBPs in GC and histologically noncancerous tissues were explored by immunohistochemistry. To explore the effects of CtBP1 on the metastatic phenotype in GC, gastric epithelial cells were transfected with a eukaryotic expression plasmid to overexpress CTBP1, and the endogenous CtBP1 or JAK1 in GC cells was silenced through an RNA interference (RNAi) method. These transfections were validated via Western blotting, and the activation state of the JAK1/Stat3 signaling pathway was also explored via Western blotting. Furthermore, the malignant phenotype of GC cells was evaluated via a Cell Counting Kit-8 (CCK8) assay, colony formation assay, transwell assay, and wound-healing experiment.

Results

Our data revealed that the expression of CtBP1, but not CTBP2, was upregulated in 102 GC tissue samples compared with 98 noncancerous tissue samples, and the elevated expression level of CtBP1 was notably associated with distant metastasis. CTBP1 modulated cell migration and invasion through the JAK1/Stat3 signaling pathway in gastric epithelial cells. In addition, genetic silence of CtBP1 expression in GC cells notably constrained cell proliferation, invasion and migration abilities through inhibiting the activation of the JAK1/Stat3 pathway in GC cells.

Conclusion

Our data reveal that the knockout of CtBP1 notably constrains distant metastasis in GC through the JAK1/Stat3 pathway, suggesting that targeting CtBP1 is a practical anti-tumor approach to restrain tumor progression in GC.

C-terminal of E1A binding protein 2 promotes the malignancy of osteosarcoma cells via JAK1/Stat3 signaling

Previous studies have demonstrated that the C-terminal of E1A binding proteins (CtBPs) influences tumorigenesis by participating in cell signal transduction in various human malignancies. However, the detailed expression patterns of CtBP isoforms in human osteosarcoma (OS) and the molecular mechanisms of CtBP involvement in tumor cell phenotypes requires further investigation. In the present study, the expression patterns of CtBP2 in OS cells and tissues were explored by immunohistochemistry. Fetal osteoblast cells were transfected with a eukaryotic expression plasmid to overexpress CtBP2, and the endogenous CtBP2 in OS cells was silenced via a short hairpin RNA. These transfections were validated and the phosphorylation levels of the JAK1/Stat3 signaling pathway were explored via western blotting. Furthermore, the malignant phenotype of OS cells was evaluated via a Cell Counting Kit-8 assay, cell colony formation assay, cell migration assay and scratch wound healing assay. The results revealed that the expression of CtBP2, but not CtBP1, was upregulated in OS tissue samples and the elevated expression level of CtBP2 was notably associated with distant metastasis. CtBP2 was demonstrated to modulate cell migration and invasion via JAK1/Stat3 signaling pathway in fetal osteoblast cells. In addition, genetic silencing of CtBP2 expression in OS cells notably reduced cell migration abilities and the phosphorylation of the JAK1/Stat3 pathway. In summary, the present studies revealed that the loss of CtBP2 constrained distant metastasis through the JAK1/Stat3 pathway in OS, suggesting that targeting CtBP2 may be a practical anti-tumor approach to prevent OS tumor progression.

The retrotransposon gag domain containing protein Rgag4 is an Ikaros target in the pituitary

Previous studies have established the common and critical involvement of the zinc finger protein Ikaros in lymphoid and pituitary cell development and expansion. Key to the assembly of several transcriptional networks, we have demonstrated up-regulation of Ikaros and its interacting partner the C-terminal Binding Protein (CtBP) in response to hypoxia. This prompted us to explore common transcriptional targets using a chromatin immunoprecipitate (ChIP) screen of DNA from pituitary corticotroph cells. This strategy yielded a finite list of targets common to both transcription factors that included the metalloprotease ADAMTS10. In this report, we focus on validation of a second candidate target, the retrotransposon gag domain containing protein Rgag4. We identified the ability of Ikaros to bind the Rgag4 promoter, influence its transcriptional activity, and induce endogenous gene expression. Robust expression of Rgag4 was noted in the anterior lobe of the pituitary gland which was diminished in Ikaros knockout mice. Down-regulation of Rgag4 resulted in profound reduction of hormone gene expression with diminished ACTH secretion, recapitulating the effect of Ikaros deficiency in knockout mice. The results introduce Rgag4 to the repertoire of effectors serving to couple the chromatin remodeler Ikaros with the hormonal stress response.