Gene commander in the trash heap: Transcriptional regulation and ubiquitination modification mediated by RNF6 in carcinogenesis

RNF6 promotes gastric cancer progression by regulating CCNA1/CREBBP transcription

Ring finger protein 6 (RNF6) is a member of the E3 ubiquitin ligase family. Previous studies have reported the involvement of RNF6 as a ubiquitin ligase in the progression of gastric cancer (GC). However, this study found that RNF6 has a clear localization in the nucleus of GC, indicating a role other than ubiquitin ligase. Further chromatin immunoprecipitation sequencing (ChIP-seq) analysis revealed that RNF6 has DNA binding and transcriptional regulatory effects and is involved in important pathways such as tumor cell cycle and apoptosis. Cyclin A1 (CCNA1) and CREB binding protein (CREBBP) are downstream targets for RNF6 transcription regulation in GC. RNF6 binds to the promoter region of CCNA1/CREBBP and is actively regulating their expression in GC cells. Silencing CCNA1/CREBBP partially reversed the promoting effect of RNF6 overexpression on the biological function of GC cells. Our study suggests that RNF6 promotes the progression of GC by regulating CCNA1/CREBBP transcription.

RNF6 activates TGF-β1/c-Myb pathway to promote EMT in esophageal squamous cell carcinoma

Objective

This study aimed to investigate RING-Finger Protein 6 (RNF6) expression in esophageal squamous cell carcinoma (ESCC) cells and whether it affects cell proliferation, invasion, and migration by regulating the TGF-β1/c-Myb pathway.

Methods

TCGA database was used to analyze RNF6 expression in normal tissues and esophageal cancer tissues. Kaplan-Meier method was used to examine the correlation between RNF6 expression and patient prognosis. SiRNA interference vector and RNF6 overexpression plasmid were constructed, and RNF6 was transfected into Eca-109 and KYSE-150 esophageal cancer cell line. In vitro scratch assay and Transwell assay were conducted to investigate the effects of RNF6 on the migration and invasion of Eca-109 and KYSE-150 cells. RT-PCR detected the expression of Snail, E-cadherin, and N-cadherin, and TUNEL detected the apoptosis of cells.

Results

RNF6 up-regulation promoted the progression of esophageal cancer and predicted poor prognosis. RNF6 also enhanced the migration and invasion of ESCC cells in vitro. RNF6 silencing inhibited the migration and invasion of ESCC cells. TGF-β inhibitors reversed the oncogenic effects of RNF6. RNF6 regulated the migration and invasion of ESCC cells by activating the TGF-β pathway. RNF6/TGF-β1 promoted esophageal cancer progression through c-Myb.

Conclusion

RNF6 promotes the proliferation, invasion, and migration of ESCC cells possibly by activating the TGF-β1/c-Myb pathway and affects the progression of ESCC.

Glaucocalyxin A Inhibits the Malignancies of Gastric Cancer Cells by Downregulating MDM2 and RNF6 via MiR-3658 and the SMG1-UPF mRNA Decay Pathway

Gastric cancer (GC) ranks as the most common gastrointestinal cancer and is among the leading causes of cancer death worldwide. Glaucocalyxin A (GLA), an entkauranoid diterpene isolated from Rab-dosia japonica var., possesses various bioactivities. To date, the data on the effect of GLA on GC are still minimal, and the molecular mechanisms remain largely unknown. Herein, we found that GLA could significantly inhibit the proliferation, cell adhesion, and invasion of HGT-1, SNU-1, SNU-6, and NCI-N87 GC cells in a dose-dependent manner. GLA enhanced the apoptosis of the GC cells as evidenced by the increased caspase-3 activity and the elevated levels of cleaved caspase-3 and cleaved PARP in GC cells in the presence of GLA. We then showed that the downregulation of Murine Double Minute Clone 2 (MDM2) and Ring Finger Protein 6 (RNF6) by GLA was implicated in the GLA-induced inhibition of the GC cells. Furthermore, MDM2 and RNF6 were identified as the targets of miR-3658 that was downregulated in the GC cells and upregulated by GLA. Moreover, it was shown that miR-3658 was hypermethylated in the GC cells, and GLA could rescue the expression of miR-3658 via demethylation by abrogating EZH2-mediated epigenetic silencing. In addition to the miR-3658-MDM2/RNF6 regulatory axis, activation of the SMG1-UPF mRNA decay pathway contributed to the downregulation of MDM2 and RNF6 by GLA in the GC cells. The inhibitory effect of GLA on gastric cancer and the expression of MDM2 and RNF6 was also validated in in vivo study. Our findings suggest that has the therapeutic potential for GC by downregulating oncogenes via posttranscriptional regulation.

RNF6 promotes colorectal cancer invasion and migration via the Wnt/β-catenin pathway by inhibiting GSK3β activity

BACKGROUND

The purpose of this study was to explore the molecular mechanism underlying the interaction between ring finger protein 6 (RNF6) and glycogen synthase kinase 3β (GSK3β) in colorectal cancer (CRC).

METHODS

In this study, cell models of overexpressed or silenced RNF6 were established by liposome transfection, and IM-12 was used as the inhibitor of GSK3β. Real-time quantitative PCR and western blots were used to detect the expression of RNF6, p-GSK3β, GSK3β, and β-catenin, and MTT assays were used to quantify cell proliferation. The tumorigenicity of cells was observed by plate clonal formation assay; the invasiveness of cells was examined in Transwell Boyden chambers, and the migratory capacity of cells was tested by scratch wound assays. The rat CRC model was induced by AOM/DSS, in which we verified activity in the Wnt/β-catenin pathway by examining GSK3β phosphorylation.

RESULTS

RNF6 was upregulated in CRC samples and cell lines. Silencing or overexpressing RNF6 in colorectal cancer cells inhibited or promoted, respectively, the proliferation, tumorigenicity, invasion and migration of CRC cells, as well as expression of p-GSK3β, GSK3β and β-catenin. IM-12 reversed the Wnt/β-catenin-activated state change induced by RNF6 silencing and the inhibition of cell proliferation, tumorigenicity, invasion and migration. The same results were observed in vivo in the rat CRC model.

CONCLUSIONS

Overexpression of RNF6 in CRC increased the GSK3β phosphorylation level, which led to activation of the Wnt/β-catenin pathway and promoted the invasion and migration of CRC cells, suggesting that RNF6 may be a novel target for the treatment of CRC.