The oncogenic impact of RNF2 on cell proliferation, invasion and migration through EMT on mammary carcinoma

E3 ubiquitin ligase RNF2 protects polymerase ι from destabilization

Human DNA polymerase ι (Polι) belongs to the Y-family of specialized DNA polymerases engaged in the DNA damage tolerance pathway of translesion DNA synthesis that is crucial to the maintenance of genome integrity. The extreme infidelity of Polι and the fact that both its up- and down-regulation correlate with various cancers indicate that Polι expression and access to the replication fork should be strictly controlled. Here, we identify RNF2, an E3 ubiquitin ligase, as a new interacting partner of Polι that is responsible for Polι stabilization in vivo. Interestingly, while we report that RNF2 does not directly ubiquitinate Polι, inhibition of the E3 ubiquitin ligase activity of RNF2 affects the cellular level of Polι thereby protecting it from destabilization. Additionally, we indicate that this mechanism is more general, as DNA polymerase η, another Y-family polymerase and the closest paralogue of Polι, share similar features.

Targeted Degradation of PRC1 Components, BMI1 and RING1B, via a Novel Protein Complex Degrader Strategy

Polycomb repressive complex 1 (PRC1) is an essential epigenetic regulator that mainly controls histone H2A Lys119 mono-ubiquitination (H2AK119ub). B cell-specific Moloney murine leukemia virus Integration site 1 (BMI1) and really interesting new gene 1B (RING1B) are PRC1 core components and play critical roles in the development of various cancers. However, therapeutic agents targeting PRC1 are very limited. In this study, MS147, the first degrader of PRC1 core components, BMI1 and RING1B, is discovered via a novel protein complex degradation strategy that utilizes the target protein's interacting partner protein (embryonic ectoderm development (EED)). MS147, which comprises an EED small-molecule binder linked to a ligand of the E3 ligase von Hippel-Lindau (VHL), degrades BMI1/RING1B in an EED-, VHL-, ubiquitination-, and time-dependent manner. MS147 preferentially degrades BMI1/RING1B over polycomb repressive complex 2 (PRC2) core components. Consequently, MS147 effectively reduces H2AK119ub, but not histone H3 Lys27 tri-methylation (H3K27me3), which is catalyzed by PRC2. Furthermore, MS147 effectively inhibits the proliferation of cancer cell lines that are insensitive to PRC2 inhibitors/degraders. Overall, this study provides a novel BMI1/RING1B degrader, which is a useful chemical tool to further investigate the roles of PRC1 in cancer, and a novel protein complex degradation strategy, which can potentially expand the degradable human proteome.

The ubiquitin ligase RNF2 stabilizes ERα and modulates breast cancer progression

Estrogen receptor α (ERα) is the most common clinical marker used for breast cancer prognosis and the classification of breast cancer subtypes. Clinically, patients with estrogen receptor-positive breast cancer can receive endocrine therapy. However, resistance to endocrine therapy has become an urgent clinical problem. A large number of previous studies have proven that posttranslational modification of the estrogen receptor is significantly related to endocrine therapy resistance. RNF2 is a member of the RING finger protein family that functions as an E3 ubiquitin ligase. Several studies have clarified that RNF2 is a critical regulator of ERα transcriptional regulation. In our current study, we identified RNF2 as an important posttranslational modification regulator of the estrogen receptor. RNF2 depletion inhibited breast cancer cell progression and ERα signaling activity. TCGA data analysis indicated that RNF2 was elevated in breast malignancies, while RNF2 depletion could drastically inhibit estrogen response gene expression on a whole-genome scale. TCGA data analysis revealed that RNF2 was positively correlated with ERα target gene expression. Further mechanistic studies showed that RNF2 was mainly localized in the nucleus and associated with ERα. The association increased ERα stability by inhibiting ERα K48-linked polyubiquitination. In conclusion, our study implicates nongenomic regulation by RNF2 on ERα protein stability and suggests that targeting RNF2 could be a promising strategy for breast cancer treatments.

DNA methyltransferase 3 beta regulates promoter methylation of microRNA-149 to augment esophageal squamous cell carcinoma development through the ring finger protein 2/Wnt/β-catenin axis

Esophageal squamous cell carcinoma (ESCC) is an aggressive form of human squamous cell carcinomas with extremely aggressive pathological features. This study explores the functions of microRNA-149 (miR-149) and its interacted molecules in ESCC. The ESCC-related miRNA and messenger RNA (mRNA) datasets were applied to identify aberrantly expressed genes in ESCC. Forty-two patients with ESCC were included and their tissue samples were collected. miR-149 was poorly expressed whereas DNA methyltransferase 3 beta (DNMT3B) and ring finger protein 2 (RNF2) were abundantly expressed in ESCC tumor samples. Overexpression of miR-149 suppressed growth and invasiveness of ESCC cells in vitro and in vivo. DNMT3B bound to the promoter region of miR-149 to trigger its promoter methylation and downregulation. RNF2 mRNA was a target of miR-149. RNF2 overexpression blocked the inhibitory effect of miR-149 on ESCC cell growth. RNF2 activated the Wnt/β-catenin pathway to promote ESCC development. In conclusion, this study found that DNMT3B downregulates miR-149 level through methylation modification of the miR-149 promoter, while miR-149 suppresses RNF2 expression and inactivates the Wnt/β-catenin pathway to suppress growth of ESCC cells.

In vitro antimetastatic activity of Momordica balsamina crude acetone extract in HT-29 human colon cancer cells

Plant-derived compounds and/or extracts have proven to be beneficial for the treatment of a broad spectrum of cancers with minimal side effects. In this study, we investigated whether a crude acetone extract of Momordica balsamina (MBE) can interfere with the metastatic ability of HT-29 colorectal cancer (CRC) cells. The phytochemical composition of MBE was determined by ultra-performance liquid chromatography and cytotoxic effects by the MTT and acridine orange/ethidium bromide staining assays. The effect of MBE on the formation of reactive oxygen species was assessed using the DCFH₂ -DA assay. Wound healing assay, transwell cell invasion assay, cell adhesion assay, and the extracellular matrix-cell adhesion array were used to assess the antimetastatic effects of MBE. The effect of MBE on the expression of TNF-α, NF-κB, TIMP-3, MMP-2, and MMP-9 was assessed by western blot analysis. Our results showed that MBE consists of a mixture of compounds without a known anticancer activity in CRC and exhibits cytotoxicity against HT-29 cells. MBE also suppressed reactive oxygen species formation, cell invasion, cell migration, and cell adhesion. The reduction of cell invasion was associated with the downregulation of TNF-α, NF-κB, MMP2, and MMP9 and upregulation of TIMP-3 proteins. We concluded that MBE inhibits the metastatic ability of HT-29 CRC cells in vitro.

RNF2 ablation reprograms the tumor-immune microenvironment and stimulates durable NK and CD4+ T-cell-dependent antitumor immunity

Expanding the utility of immune-based cancer treatments is a clinical challenge due to tumor-intrinsic factors that suppress the immune response. Here we report the identification of tumoral ring finger protein 2 (RNF2), the core subunit of polycomb repressor complex 1, as a negative regulator of antitumor immunity in various human cancers, including breast cancer. In syngeneic murine models of triple-negative breast cancer, we found that deleting genes encoding the polycomb repressor complex 1 subunits Rnf2, BMI1 proto-oncogene, polycomb ring finger (Bmi1), or the downstream effector of Rnf2, remodeling and spacing factor 1 (Rsf1), was sufficient by itself to induce durable tumor rejection and establish immune memory by enhancing infiltration and activation of natural killer and CD4⁺ T cells, but not CD8⁺ T cells, into the tumor and enabled their cooperativity. These findings uncover an epigenetic reprogramming of the tumor-immune microenvironment, which fosters durable antitumor immunity and memory.

Distinct Ring1b complexes defined by DEAD-box helicases and EMT transcription factors synergistically enhance E-cadherin silencing in breast cancer

Ring1b is a core subunit of polycomb repressive complex 1 (PRC1) and is essential in several high-risk cancers. However, the epigenetic mechanism of Ring1b underlying breast cancer malignancy is poorly understood. In this study, we showed increased expression of Ring1b promoted metastasis by weakening cell-cell adhesions of breast cancer cells. We confirmed that Ring1b could downregulate E-cadherin and contributed to an epigenetic rewiring via PRC1-dependent function by forming distinct complexes with DEAD-box RNA helicases (DDXs) or epithelial-mesenchymal transition transcription factors (EMT TFs) on site-specific loci of E-cadherin promoter. DDXs-Ring1b complexes moderately inhibited E-cadherin, which resulted in an early hybrid EMT state of epithelial cells, and EMT TFs-Ring1b complexes cooperated with DDXs-Ring1b complexes to further repress E-cadherin in mesenchymal-like cancer cells. Clinically, high expression of Ring1b with DDXs or EMT TFs predicted low levels of E-cadherin, metastatic behavior, and poor prognosis. These findings provide an epigenetic regulation mechanism of Ring1b complexes in E-cadherin expression. Ring1b complexes may be potential therapeutic targets and biomarkers for diagnosis and prognosis in invasion breast cancer.

Hsa_circRNA_100146 Acts as a Sponge of miR-149-5p in Promoting Bladder Cancer Progression via Regulating RNF2

Background

Mounting evidence has demonstrated that circular RNAs (circRNAs) play indispensable roles in the progression of bladder cancer. Public database mining showed that hsa_circRNA_100146 (circRNA_100146) was highly expressed in bladder cancer. This study aimed to characterize the biological role of circRNA_100146 and clarify the underlying mechanism in bladder cancer.

Methods

We evaluated the relationship between circRNA_100146 expression and clinicopathological features. Furthermore, gain- and loss-of-function studies were conducted in bladder cancer cells via transfection with gene-carrying plasmids (over-expression) or specific short hairpin RNAs (knockdown). Moreover, computational algorithms and dual-luciferase reporter assays were performed to explore the possible mechanisms of action. Additionally, in vivo xenograft experiments were performed to further analyze the effect of circRNA_100146 on tumor growth.

Results

Our data showed that circRNA_100146 expression was increased in bladder cancer tissues and cell lines, and that high expression of circRNA_100146 was correlated with poor patient prognosis. Upregulation of circRNA_100146 promoted cell proliferation, migration, and invasion, and inhibited cell apoptosis, whereas knockdown of circRNA_100146 displayed opposite effects on bladder cancer cells. Notably, circRNA_100146 could combine with miR-149-5p and promote ring finger protein 2 (RNF2) expression, thereby facilitating the progression of bladder cancer. Furthermore, overexpression of RNF2 reversed the effects of circRNA_100146 knockdown on the biological behaviors of bladder cancer cells. The in vivo experiments revealed that downregulation of circRNA_100146 dramatically delayed tumor growth.

Conclusion

Our findings indicate that circRNA_100146 functions as a sponge of miR-149-5p in promoting bladder cancer progression by regulating RNF2 expression and that circRNA_100146 may serve as a novel biomarker in human bladder cancer.

Clinical significance of ring finger protein 2 high expression in skin squamous cell carcinoma

Although ring finger protein 2 (RNF2) serves an important role in the occurrence, development and regulation of various types of cancer, RNF2 expression in skin squamous cell carcinoma (SCC) remains unknown. The aim of the present study was to investigate the role of RNF2 expression in SCC and adjacent tissues from patients. The protein and gene expression levels of RNF2 in SCC and adjacent tissues were detected by immunohistochemistry (IHC), western blot analysis and semi-quantitative reverse transcription (RT) PCR. Single factor analysis was used to study the association between RNF2 expression level and the clinicopathological characteristics of patients with SCC. Multifactor Cox survival analysis was used to examine the association between RNF2 expression and the overall survival rate of postoperative patients with SCC. The results from IHC staining demonstrated that the positive expression rate of RNF2 was 84.68% (210/248) and 56.05% (139/248) in SCC and in adjacent tissues, respectively. Furthermore, results from western blot analysis demonstrated that RNF2 protein expression in SCC tissues was significantly higher compared with that in the adjacent tissues (P<0.05). The positive rate of RNF2 mRNA in SCC was 81.05% (201/248), which was significantly higher compared with that in the adjacent tissues 54.44% (135/248; P<0.05). Furthermore, RNF2 protein and gene expression levels were associated with tumor diameter, tumor stage, tumor metastasis and the degree of tumor differentiation in patients with SCC. Patients exhibiting higher RNF2 protein expression in SCC tissues had a significantly shorter disease-specific survival rate compared with patients with low RNF2 expression. In addition, RNF2 protein expression, tumor diameter, tumors site and tumor stage were independent factors affecting the overall survival rate of postoperative patients. High protein and gene expression levels of RNF2 in SCC tissues may be associated with the occurrence and development of SCC and prognosis of patients. The results form this study may serve the development of novel therapeutic options and diagnostic strategies for patients with SCC.