Knockdown of RNF2 enhances the radiosensitivity of squamous cell carcinoma in lung

CPT1A promotes anoikis resistance in esophageal squamous cell carcinoma via redox homeostasis

Anoikis resistance was a prominent hallmark of cancer metastasis, and lipo-genic characteristics have been identified as another metabolic alteration during tumorigenesis. However, their crosstalk has not been fully elucidated, especially in advanced esophageal squamous cell carcinoma (ESCC). In this study, we showed, for the first time, that the key enzyme carnitine O-palmitoyl transferase 1 (CPT1A), which is involved in fatty acid oxidation (FAO), was markedly upregulated in ESCC cells upon detached culture via a metabolism PCR array. Overexpression of CPT1A was associated with poor survival of ESCC patients and could protect ESCC cells from apoptosis via maintaining redox homeostasis through supply of GSH and NADPH. Mechanistically, detached culture conditions enhanced the expression of the transcription factor ETV4 and suppressed the expression of the ubiquitin enzyme RNF2, which were responsible for the elevated expression of CPT1A at the mRNA and protein levels, respectively. Moreover, genetic or pharmacologic disruption of CPT1A switched off the NADPH supply and therefore prevented the anchorage-independent growth of ESCC cells in vitro and lung metastases of xenografted tumor models in vivo. Collectively, our results provide novel insights into how ESCC cancer cells exploit metabolic switching to form distant metastases and some evidence for the link between anoikis and FAO.

Irradiation-induced exosomal HMGB1 to confer radioresistance via the PI3K/AKT/FOXO3A signaling pathway in ESCC

Background

Radioresistance is a major cause of treatment failure in esophageal squamous cell carcinoma (ESCC) radiotherapy, and the underlying mechanisms of radioresistance are still unclear. Irradiation (IR) stimulates changes in tumor-derived exosome contents, which can be taken up by recipient cells, playing an important role in the proliferation, cell cycle and apoptosis of recipient cells. This study investigated the effect of IR-induced exosomal high mobility group box 1 (HMGB1) on radioresistance in ESCC cells.

Methods

Plasma exosomes were isolated from 21 ESCC patients and 24 healthy volunteers, and the expression of HMGB1 was examined. Then, the therapeutic effect of radiotherapy was analyzed according to the different expression levels of plasma exosomal HMGB1 in ESCC patients. The uptake of exosomes by recipient cells was verified by immunofluorescence staining, and the localization of exosomes and HMGB1 in cells before and after IR was evaluated. The effects of IR-induced exosomes on cell proliferation, invasion, apoptosis, cell cycle distribution and radioresistance after HMGB1 knockdown were verified. Moreover, western blotting was used to measure changes in the expression of cyclin B1, CDK1, Bax, Bcl2, phosphorylated histone H2AX and the PI3K/AKT/FOXO3A pathway in the HMGB1-knockdown exosome group and the negative control group.

Results

The expression of HMGB1 in ESCC plasma exosomes was significantly increased compared with that in healthy volunteers, and high expression of HMGB1 in plasma exosomes was associated with radioresistance (P = 0.016). IR-induced the release of exosomal HMGB1 and promoted proliferation and radioresistance in recipient cells, with a sensitization enhancement ratio (SER) of 0.906 and 0.919, respectively. In addition, IR-induced exosomal HMGB1 promotes G2/M phase arrest by regulating the proteins cyclin B1 and CDK1, cooperating with the proteins Bax and Bcl2 to reduce the apoptosis rate through the PI3K/AKT/FOXO3A signaling pathway, and participated in IR-induced DNA damage repair through γH2AX.

Conclusion

These findings indicate that high expression of plasma exosomal HMGB1 is associated with an adverse radiotherapy response. IR-induced exosomal HMGB1 enhances the radioresistance of ESCC cells.

SPI1 mediates transcriptional activation of TPX2 and RNF2 to regulate the radiosensitivity of lung squamous cell carcinoma

Radiotherapy acts by damaging DNA and hindering cancer cell proliferation. H2AX is phosphorylated to produce γH2AX that accumulates in a response to DNA double-strand breaks. Non-coding RNA can influence DNA damage response and enhance DNA repair, which show potential for cancer treatment. The study aimed to observe the influence of SPI1 on the radiosensitivity of lung squamous cell carcinoma (LUSC) and to investigate the mechanisms. SPI1, TPX2, and RNF2 were overexpressed in LUSC tissues and radioresistant cells comspared with adjacent tissues and parental cells, respectively. The binding between SPI1 and TPX2 or RNF2 promoter was investigated using ChIP-qPCR and dual-luciferase assays. SPI1 bound to TPX2 and RNF2 promoters and activated their transcription. SPI1 downregulation increased the radiosensitivity of LUSC cells, which was comprised by TPX2 or RNF2 overexpression. Meanwhile, SPI1 downregulation elevated the protein expression of γH2AX at the late stage of DNA damage response and suppressed DNA damage repair in LUSC cells, which were compromised by TPX2 or RNF2. These results indicate that SPI1 silencing potentiates radiosensitivity in LUSC cells by downregulating the transcription of TPX2 and RNF2, which provides a potential target for the radiotherapy in LUSC.

LncRNA KCNQ1OT1 enhances the radioresistance of lung squamous cell carcinoma by targeting the miR-491-5p/TPX2-RNF2 axis

BACKGROUND

Lung cancer, especially lung squamous cell carcinoma (LUSC), is one of the most common malignant tumors worldwide. Currently, radiosensitization research is a vital direction for the improvement of LUSC therapy. Long non-coding RNAs (lncRNAs) can be novel biomarkers due to their multiple functions in cancers. However, the function and mechanism of lncRNA KCNQ1OT1 in the radioresistance of LUSC remain to be elucidated.

METHODS

The clonogenic assay was employed to determine the radioresistance of SK-MES-1R and NCI-H226R cells. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot were conducted for the detection of gene expression. Cell proliferation was determined by the methyl thiazolyl tetrazolium (MTT) assay, colony formation assay, and 5-ethynyl-2'-deoxyuridine (EdU) staining, and cell apoptosis was assessed by flow cytometry. The relationships between genes were also evaluated by applying the luciferase reporter and radioimmunoprecipitation (RIP) assays.

RESULTS

Radioresistant LUSC cells (SK-MES-1R and NCI-H226R) had strong resistance to X-ray irradiation, and lncRNA KCNQ1OT1 was highly expressed in SK-MES-1R and NCI-H226R cells. Moreover, knockdown of lncRNA KCNQ1OT1 prominently suppressed proliferation, attenuated radioresistance, and accelerated the apoptosis of SK-MES-1R and NCI-H226R cells. More importantly, we verified that miR-491-5p was a regulatory target of lncRNA KCNQ1OT1, and Xenopus kinesin-like protein 2 (TPX2) and RING finger protein 2 (RNF2) were the target genes of miR-491-5p. The rescue experiment results also demonstrated that miR-491-5p was involved in the inhibition of cell proliferation and the downregulation of TPX2 and RNF2 expression mediated by lncRNA KCNQ1OT1 knockdown in SK-MES-1R and NCI-H226R cells.

CONCLUSIONS

LncRNA KCNQ1OT1 was associated with the radioresistance of radioresistant LUSC cells, and the lncRNA KCNQ1OT1/miR-491-5p/TPX2-RNF2 axis might be used as a therapeutic target to enhance the radiosensitivity of radioresistant LUSC cells.

RNF2 mediates pulmonary fibroblasts activation and proliferation by regulating mTOR and p16-CDK4-Rb1 signaling pathway

BACKGROUND

Pulmonary fibrosis (PF) is a chronic, progressive interstitial lung disease with unknown etiology, associated with increasing morbidity and pessimistic prognosis. Pulmonary fibroblasts (PFbs) are the key effector cells of PF, in which abnormal activation and proliferation is an important pathogenesis of PF. Ring finger protein 2 (RNF2), is identified as the catalytic subunit of poly-comb repressive complex 1, which is closely related to occurrence and development of lung cancer, but its function in PF has not been revealed. In this paper, we sought to identify the regulatory role of RNF2 in lung fibrogenesis and its underlying mechanisms.

METHODS

The expression of RNF2 in lung fibrosis tissue (human and Bleomycin-induced mouse) and cell model (TGF-β1-induced HFL1 cells) was examined by immunoblotting analysis and immunofluorescence. Western blot, qRT-PCR were performed to evaluate the expression of pro-fibrogenic cytokines (including α-SMA, ECM and MMPs/ TIMPs) induced by TGF-β1 in HFL1 cells. Cell proliferation, cycle progression and apoptosis were examined by fow cytometric. Molecular interactions were tested by Co-IP assays.

RESULTS

RNF2 expression was elevated in PF tissues compared to normal adjacent tissues and in PFbs (HFL1) induced by TGF-β1. Furthermore, knockdown of RNF2 could evidently inhibit the abnormal expression of pro-fibrogenic cytokines (including α-SMA, ECM and MMPs/TIMPs) induced by TGF-β1 in HFL1 cells. Functionally, RNF2 silencing could significantly suppress TGF-β1-induced anomalous proliferation, cell cycle progression, apoptosis and autophagy in HFL1 cells. Mechanistically, RNF2 deficiency could effectively inhibit the abnormal activation of mTOR signaling pathway in TGF-β1-induced HFL1 cells, and mTOR pathway had feedback regulation on the expression of RNF2. Further studies RNF2 could regulate the phosphorylation level of RB1 through interacting with p16 to destroy the binding of p16 and CDK4 competitively. Simultaneously, overexpression of RNF2 could show the opposite results.

CONCLUSIONS

These results indicated that RNF2 is a potent pro-fibrogenic molecule for PFbs activation and proliferation through mTOR and p16-CDK4-Rb signaling pathways, and RNF2 inhibition will be a potential therapeutic avenue for treating PF.

Emerging role of RNF2 in cancer: From bench to bedside

RNF2 (also known as ding, Ring1B or Ring2) is a member of the Ring finger protein family, which functions as E3 ubiquitin ligase for monoubiquitination of histone H2A at lysine 119 (H2AK119ub). RNF2 gene is located at the 1q25.3 site of human chromosome and the coding region is composed of 9 exons, encoding 336 amino acids in total. Many studies have demonstrated that overexpressed RNF2 was involved in the pathological progression of multiple cancers and has an impact on their clinical features. For instance, the upregulated expression level of RNF2 is positively correlated with the occurrence and progression of hepatocellular carcinoma, melanoma, prostate cancer, breast cancer, pancreatic cancer, gastric cancer, and bladder urothelial carcinoma, as well as with the radioresistance of lung cancer and chemoresistance of ovarian cancer. This review provides an up-to-date perspective on the relationship between RNF2 and several cancers and highlights recent studies on RNF2 regulation. In particular, the relevant cellular signaling pathways and potential clinical value of RNF2 in cancers are also discussed, suggesting its potential as an epigenetic biomarker and therapeutic target for these cancers.

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.

Long non-coding RNA LINC00665 gastric cancer tumorigenesis by regulation miR-149-3p/RNF2 axis

Background

Recently, LINC00665 has been reported to be a pivotal regulator in kinds of malignancy, such as lung cancer and liver cancer. However, the functions and underlying mechanisms of LINC00665 in gastric cancer (GC) remain unclear.

Materials and methods

We recruited 49 paired GC tissue to explore LINC00665 expression by qRT-PCR. In vitro function assays were used to explore the roles of LINC00665 in GC progression. Moreover, the interaction among LINC00665, miR-149-3p and RNF2 was explored by bioinformatics analysis and luciferase reporter assay.

Results

In the present study, we found that LINC00665 expression was significantly elevated in GC tissues and cell lines. High LINC00665 expression was associated with TNM stage, histological grade, and poor prognosis of GC patients. Function assays showed that LINC00665 suppression significantly reduced GC cells viability and invasion ability in vitro. Mechanistic analysis showed that LINC00665 might serve as a ceRNA for miR-149-3p to regulate the expression of RNF2.

Conclusion

Our current study revealed the LINC00665/miR-149-3p/RNF2 axis was involved in GC progression, providing novel insights into the treatment for GC.