Comprehensive Analysis of E3 Ubiquitin Ligases Reveals Ring Finger Protein 223 as a Novel Oncogene Activated by KLF4 in Pancreatic Cancer

Pancreatic cancer is one of the major malignancies and causes of mortality worldwide. E3 ubiquitin-protein ligases transfer activated ubiquitin from ubiquitin-conjugating enzymes to protein substrates and confer substrate specificity in cancer. In this study, we first downloaded data from The Cancer Genome Atlas pancreatic adenocarcinoma dataset, acquired all 27 differentially expressed genes (DEGs), and identified genomic alterations. Then, the prognostic significance of DEGs was analyzed, and eight DEGs (MECOM, CBLC, MARCHF4, RNF166, TRIM46, LONRF3, RNF39, and RNF223) and two clinical parameters (pathological N stage and T stage) exhibited prognostic significance. RNF223 showed independent significance as an unfavorable prognostic marker and was chosen for subsequent analysis. Next, the function of RNF223 in the pancreatic cancer cell lines ASPC-1 and PANC-1 was investigated, and RNF223 silencing promoted pancreatic cancer growth and migration. To explore the potential targets and pathways of RNF223 in pancreatic cancer, quantitative proteomics was applied to analyze differentially expressed proteins, and metabolism-related pathways were primarily enriched. Finally, the reason for the elevated expression of RNF223 was analyzed, and KLF4 was shown to contribute to the increased expression of RNF233. In conclusion, this study comprehensively analyzed the clinical significance of E3 ligases. Functional assays revealed that RNF223 promotes cancer by regulating cell metabolism. Finally, the elevated expression of RNF223 was attributed to KLF4-mediated transcriptional activation. This study broadens our knowledge regarding E3 ubiquitin ligases and signal transduction and provides novel markers and therapeutic targets in pancreatic cancer.

CRISPR/cas9-mediated overexpression of long non-coding RNA SRY-box transcription factor 21 antisense divergent transcript 1 regulates the proliferation of osteosarcoma by increasing the expression of mechanistic target of rapamycin kinase and Kruppel like factor 4

Osteosarcoma, derived from primitive mesenchymal cells, is the most common primary solid malignant tumor of bone. The cause of osteosarcoma remains unclear. In recent years, the role of non-coding sequences in regulating protein expression in tumors has been paid more and more attention, especially long non-coding RNA (lncRNA). We speculate that SRY-box transcription factor 21 antisense divergent transcript 1 (SOX21-AS1) can regulate the expression of the mechanistic target of rapamycin kinase (mTOR) and Kruppel-like factor 4 (KLF4) through sponging hsa-mir-7-5p and hsa-mir-145-5p. We knocked lncRNA SOX21-AS1 into the genome of 143B cells through CRISPR/Cas9, then screened out a monoclonal cell line. Detect the transcription level and protein expression level of the above-mentioned related genes, and cell proliferation. Then, ginsenoside Rg3 was added to culture the cell line knocked into lncRNA SOX21-AS1, and the expression levels of lncRNA SOX21-AS1, hsa-mir-7-5p, hsa-mir-145-5p, mTOR, and KLF4 were detected by RT-qPCR and Western blot. Cell proliferation method detects cell viability, explores the molecular mechanism of lncRNA SOX21-AS1 in osteosarcoma, and checks whether it can be used as a potential drug target for the treatment of osteosarcoma. Our results demonstrate that the overexpression of lncRNA SOX21-AS1 up-regulates mTOR and KLF4 by sponging hsa-mir-7-5p and hsa-mir-145-5p, and ultimately regulates the proliferation of osteosarcoma. It is proved that ginsenoside Rg3 can inhibit the cell proliferation of osteosarcoma by reducing the expression level of lncRNA SOX21-AS1. It provides an alternative for the treatment of osteosarcoma in the future.

KLF4 Induces Mesenchymal-Epithelial Transition (MET) by Suppressing Multiple EMT-Inducing Transcription Factors

Epithelial-Mesenchymal Plasticity (EMP) refers to reversible dynamic processes where cells can transition from epithelial to mesenchymal (EMT) or from mesenchymal to epithelial (MET) phenotypes. Both these processes are modulated by multiple transcription factors acting in concert. While EMT-inducing transcription factors (TFs)-TWIST1/2, ZEB1/2, SNAIL1/2/3, GSC, and FOXC2-are well-characterized, the MET-inducing TFs are relatively poorly understood (OVOL1/2 and GRHL1/2). Here, using mechanism-based mathematical modeling, we show that transcription factor KLF4 can delay the onset of EMT by suppressing multiple EMT-TFs. Our simulations suggest that KLF4 overexpression can promote a phenotypic shift toward a more epithelial state, an observation suggested by the negative correlation of KLF4 with EMT-TFs and with transcriptomic-based EMT scoring metrics in cancer cell lines. We also show that the influence of KLF4 in modulating the EMT dynamics can be strengthened by its ability to inhibit cell-state transitions at the epigenetic level. Thus, KLF4 can inhibit EMT through multiple parallel paths and can act as a putative MET-TF. KLF4 associates with the patient survival metrics across multiple cancers in a context-specific manner, highlighting the complex association of EMP with patient survival.

Isoform-specific effects of transcription factor TCFL5 on the pluripotency-related genes SOX2 and KLF4 in colorectal cancer development

Colorectal cancer (CRC) is a very common life‐threatening malignancy. Transcription factor‐like 5 (TCFL5) has been suggested to be involved in CRC. Here, we describe the expression of four alternative transcripts of TCFL5 and their relevance in CRC. Complete deletion of all isoforms drastically decreased pro‐tumoural properties such as spheroids formation and in vivo tumour growth, although increased migration in CRC cell lines. Overexpression of the two main isoforms, TCFL5_E8 and CHA, had opposite effects: TCFL5_E8 reduced proliferation and spheroids formation, while CHA increased them. TCFL5_E8 reduced in vivo tumour formation, while CHA had no effect. In addition, TCFL5_E8 and CHA have different roles in the regulation of the pluripotency‐related genes SOX2 and KLF4. Both isoforms bind directly to their promoters; however, TCFL5_E8 induced SOX2 and reduced KLF4 mRNA levels, whereas CHA did the opposite. Together, our results show that TCFL5 plays an important role in the development of CRC, being however isoform‐specific. This work also points to the need to analyse separately TCFL5 isoforms in cancer, due to their different and opposite functions.

A Pioneer Transcription Factor and Type I Nuclear Hormone Receptors Synergistically Activate the Bovine Herpesvirus 1 Infected Cell Protein 0 (ICP0) Early Promoter

Following bovine herpesvirus 1 (BoHV-1) acute infection of ocular, oral, or nasal cavities, sensory neurons within trigeminal ganglia are an important site for latency. Stress, as mimicked by the synthetic corticosteroid dexamethasone, consistently induces reactivation from latency. Expression of two key viral transcriptional regulatory proteins, BoHV-1 infected cell protein 0 (bICP0) and bICP4, are regulated by sequences within the immediate early promoter (IEtu1). A separate early promoter also drives bICP0 expression, presumably to ensure sufficient levels of this important transcriptional regulatory protein. Productive infection and bICP0 early promoter activity are cooperatively transactivated by Krüppel-like factor 4 (KLF4) and a type I nuclear hormone receptor (NHR), androgen receptor, glucocorticoid receptor, or progesterone receptor. The bICP0 early promoter contains three separate transcriptional enhancers that mediate cooperative transactivation. In contrast to the IEtu1 promoter, the bICP0 early promoter lacks consensus type I NHR binding sites. Consequently, we hypothesized that KLF4 and Sp1 binding sites are essential for type I NHR and KLF4 to transactivate the bICP0 promoter. Mutating KLF4 and Sp1 binding sites in each enhancer domain significantly reduced transactivation by KLF4 and a type I NHR. Chromatin immunoprecipitation (ChIP) studies demonstrated that occupancy of bICP0 early promoter sequences by KLF4 and type I NHR is significantly reduced when KLF4 and/or Sp1 binding sites are mutated. These studies suggest that cooperative transactivation of the bICP0 E promoter by type I NHRs and a stress-induced pioneer transcription factor (KLF4) promote viral replication and spread in neurons or nonneural cells in reproductive tissue. IMPORTANCE Understanding how stressful stimuli and changes in the cellular milieu mediate viral replication and gene expression in the natural host is important for developing therapeutic strategies that impair virus transmission and disease. For example, bovine herpesvirus 1 (BoHV-1) reactivation from latency is consistently induced by the synthetic corticosteroid dexamethasone, which mimics the effects of stress. Furthermore, BoHV-1 infection increases the incidence of abortion in pregnant cows, suggesting that sex hormones stimulate viral growth in certain tissues. Previous studies revealed that type I nuclear hormone receptors (NHRs) (androgen, glucocorticoid, or progesterone) and a pioneer transcription factor, Krüppel-like factor 4 (KLF4), cooperatively transactivate the BoHV-1 infected cell protein 0 (bICP0) early promoter. Transactivation was mediated by Sp1 and/or KLF4 consensus binding sites within the three transcriptional enhancers. These studies underscore the complexity by which BoHV-1 exploits type I NHR fluctuations to enhance viral gene expression, replication, and transmission in the natural host.

KLF4 transactivates TRIM29 expression and modulates keratin network

The Krüppel-like factor 4 (KLF4) is well known to be a conserved zinc-containing transcription factor that participates in diverse biological processes such as cell proliferation and differentiation. In this study, we found KLF4 can bind specific site in the promoter of TRIM29 to transactivate its transcription, and sumoylation modification on 278 lysine site was not essential for KLF4 to transactivate TRIM29 transcription. It also was showed that KLF4 promoted cell migration when overexpressed, and knockdown of TRIM29 abrogated the migration triggered by KLF4. In addition, overexpression of KLF4 reduced the phosphorylation level of keratin 8 at 432 amino acid site. Our study demonstrated that KLF4 is an important transcription factor on regulating TRIM29 expression and modulates the keratin network.

Deletion of Fam172a accelerates advanced atherosclerosis and induces plaque instability

BACKGROUND AND AIMS

Vascular smooth muscle cells (VSMCs) play a critical role in atherosclerosis. The family with sequence similarity 172, member A (FAM172A) is a novel protein and its role in atherosclerosis has not been explored so far. Therefore, our aim is to investigate whether FAM172A affects atheroprogression through VSMCs and its possible mechanism.

METHODS

Fam172a^-/- mice were generated using CRISPR/Cas9 technology. Fam172a^-/- and Apoe^-/- double knockout (Fam172a^-/-/Apoe^-/-) mice and their littermates (Fam172a^+/+/Apoe^-/-) were fed with a Western diet for 18 weeks to induce advanced atherosclerotic lesions. The role and mechanism of Fam172a in phenotypic switching, proliferation and migration of VSMCs were investigated through in vivo and in vitro experiments.

RESULTS

Compared with Fam172a^+/+/Apoe^-/- mice, Fam172a^-/-/Apoe^-/- mice showed increased atherosclerotic lesion size and plaque instability such as increased necrotic core area and decreased fiber deposition. Additionally, knockout of Fam172a promoted expression of CD68 and KLF4 and decreased expression of α-SMA and SM22α in atherosclerotic lesions. Furthermore, overexpression of Fam172a promoted Movas cells proliferation and migration, increased expression of α-SMA and SM22α and decreased expression of KLF4. Meanwhile, knockdown of Fam172a in Movas cells and deletion of Fam172a in VSMCs from Fam172a^-/-/Apoe^-/- mice showed opposite phenotypes. Similar phenotypes were also observed in human aortic smooth muscle cells.

CONCLUSIONS

Our results provide the first direct evidence that Fam172a has a protective role in advanced atherosclerosis by increasing atherosclerotic plaque stability and inhibiting transition of VSMCs from contractile to synthetic phenotype, which may be through KLF4-dependent pathway.

Quantitative analysis of KLF4 and SOX2 expression in oral carcinomas reveals independent association with oral tongue subsite location and histological grade

BACKGROUND

Stemness factors associated with tumorigenesis in different types of cancers have not been specifically studied in oral tongue SCC (OTSSC). Here, we aimed to quantify expression levels and distribution of KLF4 and SOX2, two relevant stemness factors, in oral SCC including OTSCC samples from different subsites.

METHODS AND RESULTS

We determined KLF4 and SOX2 expression levels by immunostaining 35 biopsies of OSCC. Stained wholeslide images were digitized and subjected to automatic cell detection and unbiased quantification using Qupath software. We found statistically significant reduction in KLF4 positive cells density (p= 0.024), and fraction (p= 0.022) in OTSCC from tongue borders compared with other tongue subsites. Instead, quantitative SOX2 analysis did not show differences in expression levels between OTSCC from the borders versus OTSCC developed in others subsites. Notably SOX2 expression was revealed increased in moderately and poorly differentiated OSCC compared with well differentiated ones (positive cells density p= 0.025, fraction p= 0.006). No significant correlation between KLF4 and SOX2 expression was observed, neither in OSCC nor in OTSCC.

CONCLUSIONS

KLF4 and SOX2 exhibit opposite expression profiles regarding subsite localization and differentiation level in OSCC. Our study prompts future OTSCC prospective studies looking for clinical prognosis to incorporate detailed subsite information in the analysis.

KLF4 Inhibits the Differentiation of Goat Intramuscular Preadipocytes Through Targeting C/EBPβ Directly

Intramuscular fat (IMF) deposition is a complicated process, and most of the underlying regulators of this biological process are unknown. Here, we cloned the intact CDS of KLF4 gene, investigated the role of KLF4 by gaining or losing function in vitro and further explored the pathways of KLF4 regulating differentiation of intramuscular preadipocytes in goat. Our results show that goat KLF4 gene consists of 1,536 bp encoding a protein of 486 amino acids. The expression of KLF4 is higher in the lung while lower in the heart and muscle in goat. Knockdown of KLF4 mediated by siRNA technique significantly promotes intramuscular preadipocyte lipid accumulation and upregulates mRNA expression of adipogenic related genes including C/EBPα, C/EBPβ, and PPARγ in vivo cultured cells. Consistently, overexpression of KLF4 inhibits intramuscular adipocyte lipid accumulation and significantly downregulation gene expression of C/EBPβ, PPARγ, aP2, and Pref-1. Further, we found that other members of KLFs were upregulated or downregulated after interference or overexpression of KLF4, including KLF2 and KLF5-7. We also found that C/EBPβ was a potential target of KLF4, because it had an opposite expression pattern with KLF4 during the differentiation of intramuscular preadipocytes and had putative binding sites of KLF4. The dual-luciferase reporter assay indicated that overexpression of KLF4 inhibited the transcriptional activity of C/EBPβ. These results demonstrate that KLF4 inhibits the differentiation of intramuscular preadipocytes in goat by targeting C/EBPβ.

Comprehensive Integrative Analysis Reveals the Association of KLF4 with Macrophage Infiltration and Polarization in Lung Cancer Microenvironment

Macrophage polarization and infiltration to the tumor microenvironment (TME) is a critical determining factor for tumor progression. Macrophages are polarized into two states—M1 (pro-inflammatory, anti-tumorigenic and stimulated by LPS or IFN-γ) and M2 (anti-inflammatory pro-tumorigenic and stimulated by IL-4) phenotypes. Specifically, M2 macrophages enhance tumor cell growth and survival. Recent evidences suggest the pivotal role of microRNAs in macrophage polarization during the development of Non-small cell lung cancer (NSCLC), thus proposing a new therapeutic option to target lung cancer. In silico analysis determined cogent upregulation of KLF4, downregulation of IL-1β and miR-34a-5p in NSCLC tissues, consequently worsening the overall survival of NSCLC patients. We observed a significant association of KLF4 with macrophage infiltration and polarization in NSCLC. We found that KLF4 is critically implicated in M2 polarization of macrophages, which, in turn, promotes tumorigenesis. KLF4 expression correlated with miR-34a-5p and IL-1β in a feed-forward loop (FFL), both of which are implicated in immune regulation. Mechanistic overexpression of miR-34a-5p in macrophages (IL-4 stimulated) inhibits KLF4, along with downregulation of ARG1, REL-1MB (M2 macrophage specific markers), and upregulation of IL-1β, IL-6, (M1 macrophage specific markers), demonstrating macrophage polarization switch from M2 to M1 phenotype. Moreover, co-culture of these macrophages with NSCLC cells reduces their proliferation, wound healing, clonogenic capacity and enhanced NO-mediated apoptosis. Further, transfection of miR-34a-5p in NSCLC cells, also degrades KLF4, but enhances the expression of KLF4 regulated genes—IL-1β, IL-6 (pro-inflammatory mediators), which is further enhanced upon co-culture with IL-4 stimulated macrophages. Additionally, we observed a significant increase in i-NOS/NO content upon co-culture, suggesting polarization reversion of macrophages from M2 to M1, and eventually leading to anti-tumor effects. Our findings thus show a significant role of KLF4 in tumorigenesis and TAM polarization of NSCLC. However, miR-34a-5p mediated targeting of these molecular networks will provide a better therapeutic intervention for NSCLC.

miR-7 regulates the apoptosis of chicken primary myoblasts through the KLF4 gene

1. MicroRNAs (miRNAs) play a vital role in the proliferation, differentiation, and apoptosis of myoblasts. However, the effect of miR-7 on the apoptosis of chicken primary myoblasts (CPMs) and its mechanism is still unclear.2. In this study, the expression of apoptosis marker genes (RAF1, Caspase3, Caspase9, Cytc, Fas) in CPMs was significantly increased after transfection of miR-7 mimic. The expression of the apoptosis marker genes in CPMs was significantly reduced after transfection with miR-7 inhibitor. Flow cytometry showed that the late apoptosis rate of the mimic group was significantly higher than the negative control (NC). The viable cells of the mimic group were significantly lower than the NC. In contrast, inhibition of miR-7 had the opposite effect.3. The dual-luciferase assay showed that the KLF4 was a target gene of miR-7. The rescue experiment showed that the KLF4 gene could attenuate the effect of miR-7 on the expression of apoptosis marker genes in CPMs.4. Determination of the function the KLF4 gene showed that the expression of the apoptosis marker genes in CPMs decreased significantly compared with the NC after its overexpression. Inhibition of KLF4 gene had the opposite effect. Flow cytometry showed that overexpression of the KLF4 gene inhibited early apoptosis of myoblasts (P ≤ 0.01), while interference with the KLF4 gene could promote early apoptosis of myoblasts (P ≤ 0.001).5. The results demonstrated, for the first time, that miR-7 promotes apoptosis in chicken primary myoblasts by regulating the expression of the KLF4 gene.

Divergent roles for KLF4 and TFCP2L1 in naive ground state pluripotency and human primordial germ cell development

During embryo development, human primordial germ cells (hPGCs) express a naive gene expression program with similarities to pre-implantation naive epiblast (EPI) cells and naive human embryonic stem cells (hESCs). Previous studies have shown that TFAP2C is required for establishing naive gene expression in these cell types, however the role of additional naive transcription factors in hPGC biology is not known. Here, we show that unlike TFAP2C, the naive transcription factors KLF4 and TFCP2L1 are not required for induction of hPGC-like cells (hPGCLCs) from hESCs, and they have no role in establishing and maintaining a naive-like gene expression program in hPGCLCs with extended time in culture. Taken together, our results suggest a model whereby the molecular mechanisms that drive naive gene expression in hPGCs/hPGCLCs are distinct from those in the naive EPI/hESCs.

LINC00852 is associated with poor prognosis in non-small cell lung cancer patients and its inhibition suppresses cancer cell proliferation and chemoresistance via the hsa-miR-145-5p/KLF4 axis

BACKGROUND

Emerging evidence shows that long non-coding RNAs (lncRNAs) play important roles in human cancer. In the present study, we examined the expression, prognostic implications and functional roles of a lncRNA, LINC00852 in non-small cell lung cancer (NSCLC).

METHODS

LINC00852 expression was examined by quantitative real-time PCR (qRT-PCR) in both NSCLC clinical samples and in vitro NSCLC cell lines. In patients with NSCLC, postoperative overall survival was estimated according to endogenous LINC00852 expression in their cancerous lung tissues. In NSCLC cell line SW900 and H441 cells, LINC00852 was down-regulated to examine its effects on cancer proliferation, cisplatin chemoresistance and cell-cycle transition in vitro, as well as tumorigenicity in vivo. The potential downstream target of LINC00852, the axis of human microRNA-145-5p (hsa-miR-145-5p) and Kruppel-like factor 4 (KLF4) gene, was investigated in NSCLC, by dual-luciferase assay, qRT-PCR and genetic knockdown functional assays.

RESULTS

LINC00852 is up-regulated in both NSCLC tumors and NSCLC cell lines. High LINC00852 expression was significantly correlated with NSCLC patients' short overall survival. In NSCLC cell lines, LINC00852 down-regulation had anti-cancer effects by suppressing cancer cell proliferation, cisplatin chemoresistance and cell-cycle transition in vitro, as well as explant growth in vivo. Moreover, the hsa-miR-145-5p/KLF4 axis was demonstrated to be directly regulated by LINC00852 in NSCLC. Inhibiting hsa-miR-145-5p or overexpressing KLF4 could reverse the LINC00852-down-regulation-induced anti-cancer effects on NSCLC cancer cell proliferation and chemoresistance.

CONCLUSIONS

LINC00852 may be a prognostic biomarker for NSCLC. The epigenetic signaling pathway of LINC00852/hsa-miR-145-5p/KLF4 may be considered as a novel molecular target for fighting NSCLC.

Magnesium favors the capacity of vitamin D3 to induce the monocyte differentiation of U937 cells

The hematopoietic U937 cells are able to differentiate into monocytes, macrophages, or osteoclasts when stimulated, respectively, with vitamin D3 (VD3), phorbol 12-myristate 13-acetate (PMA) or PMA plus VD3. We have previously demonstrated that magnesium (Mg) strongly potentiates the osteoclastic differentiation of U937 cells. In this study, we investigated whether such an effect may be ascribed to a capacity of Mg to modulate the monocyte differentiation of U937 cells and/or to an ability of Mg and VD3 to act directly and independently on the early phases of the osteoclastic differentiation. To address this issue, we subjected U937 cells to an individual and combined treatment with Mg and VD3 and then we analyzed, by flow cytometry and quantitative real-time polymerase chain reaction, the expression of a number of genes related to the early phases of the differentiation pathways under consideration. The results obtained indicated that Mg favors the monocyte differentiation of U937 cells induced by VD3 and at the same time, Mg contrasts the inhibitory effect that VD3 exerts on the osteoclastic differentiation in the absence of PMA. The crucial and articulated role played by Mg in diverse pathways of the osteoclastic differentiation of U973 cells is emphasized.

Clinical Characteristics and Magnetic Resonance Imaging-Based Prediction of the KLF4K409Q Mutation in Meningioma

BACKGROUND

Meningioma is the most common primary brain tumor in adults. In recent years, several non-neurofibromin 2 mutations, i.e., AKT1, SMO, TRAF7, and KLF4 mutations, specific for meningioma have been identified. This study aims to analyze the clinical impact and imaging characteristics of the KLF4^K409Q mutation in meningioma.

METHODS

Clinical, neuropathologic, and imaging data of 170 patients who underwent meningioma resection between 2013 and 2018 were retrospectively collected and tumors were analyzed for the presence of the KLF4^K409Q mutation. We collected imaging characteristics, performed volumetric analysis of tumor size and peritumoral edema (PTBE), and calculated the edema index (EI, i.e., ratio of PTBE to tumor volume). Receiver operating characteristic curve analysis was performed to identify cut-off EI values to predict the mutational status of KLF4.

RESULTS

Eighteen (10.6%) of the meningiomas carried the KLF4^K409Q mutation; these were significantly associated with a secretory subtype (P < 0.001) and sphenoid wing location (P = 0.029). Smaller tumor size (P = 0.007), an increased PTBE (P = 0.012), and an increased EI (P = 0.001) proved to be significantly associated with the KLF4^K409Q mutation. In receiver operating characteristic curve analysis, EI predicted the KLF4^K409Q mutation with an area under the curve of 0.728 (P = 0.0016).

CONCLUSIONS

The KLF4^K409Q mutation is associated with a distinct small tumor subtype, prone to substantial PTBE. EI is a reliable parameter to predict the KLF4^K409Q mutation in meningioma, thus providing a tool for improvement of pre- and perioperative medical management.

USP11 degrades KLF4 via its deubiquitinase activity in liver diseases

Krüppel‐like factor 4 (KLF4) is a zinc‐finger containing DNA‐binding transcription factor involved in tumorigenesis and acts as a tumour suppressor or an oncogene depending on the tissue. In hepatocellular carcinoma (HCC), KLF4 has been considered as a tumour suppressor, although the mechanism underlying its action remains largely unknown. In this study, we identified the ubiquitin‐specific peptidase USP11 as a KLF4‐interacting deubiquitinating enzyme using a proteomic approach. USP11 destabilizes KLF4 through the removal of K63‐dependent polyubiquitination, thereby inhibiting KLF4 expression. We also provide mechanistic insights into KLF4 degradation and show that USP11 depletion inhibits growth and chemoresistance of HCC cells by enhancing KLF4 stability. Importantly, lipid content was reduced and genes involved in fatty acid metabolism were down‐regulated in an in vitro steatosis conditions upon USP11 knockout. Finally, elevated USP11 and reduced KLF4 levels were detected both in a hepatic steatosis in vitro model and in public clinical data of non‐alcoholic fatty liver disease and HCC patients. Collectively, these findings suggest that USP11, as KLF4‐binding partner, is an important mediator of hepatic tumorigenesis that functions via degradation of KLF4 and is a potential treatment target for liver diseases.

3,3'-Diindolylmethane Enhances Paclitaxel Sensitivity by Suppressing DNMT1-Mediated KLF4 Methylation in Breast Cancer

Paclitaxel (PTX) is a first-line chemotherapeutic drug for the treatment of breast cancer, but drug resistance seriously limits its clinical use. The aim of the present work was to explore the effect of 3,3’-diindolylmethane (DIM) on PTX sensitivity and its possible mechanism in breast cancer. The expression of Krüppel-like factor 4 (KLF4) and DNA-methyltransferase 1 (DNMT1) in breast cancer tissues were assessed by immunohistochemistry and Western blotting. The methylation of KLF4 was evaluated by the MassARRAY platform. The lentivirus carrying KLF4 and DNMT1 gene or shRNA targeting DNMT1 were used to overexpress KLF4 or knockdown DNMT1 in MCF-7 and T47D breast cancer cells and the role of KLF4 and DNMT1 in regulation of PTX sensitivity was investigated. The effect of PTX on inhibiting the proliferation of MCF-7 and T47D cells was measured by CCK-8 assay. Flow cytometry was used to examine cell apoptosis. The expression of mRNA and protein was evaluated by qRT-PCR and Western blotting analysis, respectively. Our data showed that the expression of DNMT1 was increased, and the methylation level of CpG sites (−148 bp) in the KLF4 promoter was increased while the KLF4 expression was significantly decreased in breast cancer tissues. Overexpression of KLF4 increased the sensitivity of MCF-7 and T47D cells to PTX. DNMT1 increased the methylation of the KLF4 promoter and decrease the expression of KLF4. Knockdown of DNMT1 increased the sensitivity of MCF-7 and T47D cells to PTX. DIM enhanced the PTX sensitivity of MCF-7 and T47D cells, decreased the expression of DNMT1 and the methylation level of KLF4 promoter, thus increasing the level of KLF4. Furthermore, overexpression of DNMT1 attenuated the effect of DIM on the regulation of PTX sensitivity. Collectively, our data indicated that DNMT1-mediated hypermethylation of KLF4 promoter leads to downregulation of KLF4 in breast cancer. The level of KLF4 is correlated with the sensitivity of MCF-7 and T47D cells to PTX. DIM could enhance the antitumor efficacy of PTX on MCF-7 and T47D cells by regulating DNMT1 and KLF4.

Smooth muscle cell-specific knockout of interferon gamma (IFN-γ) receptor attenuates intimal hyperplasia via STAT1-KLF4 activation

BACKGROUND

Intimal hyperplasia is a main contributor to in-stent restenosis. Previous researches have shown that interferon-gamma (IFN-γ), a pleiotropic pro-inflammatory factor, plays a pathological role in intimal hyperplasia. However, the specific role and molecular mechanism of vascular smooth muscle cells (VSMCs)-derived IFN-γ receptor in intimal hyperplasia remains unknown.

METHODS

We examined the distribution of IFN-γ receptor in human restenosis arteries. Then, the role of IFN-γ receptor in intimal hyperplasia was detected using VSMC-specific IFN-γ receptor-knock out carotid ligation injury models. We performed immunostaining, transwell assay and EdU staining to identify the role of IFN-γ in VSMCs proliferation and migration. The effect of IFN-γ on VSMCs phenotype switching was also investigated. Finally, we evaluated whether the mechanism of IFN-γ on intimal hyperplasia is STAT1-KLF4 dependent.

RESULTS

The distribution of IFN-γ receptor in human restenosis arteries with VSMC-rich neointima is eventually upregulated. Specific deletion of IFN-γ receptor exhibits thinner intima and lesser proliferating VSMCs. In vitro, treatment with IFN-γ promotes human aortic VSMC (HAVSMCs) proliferation and migration, whereas specifically knock out IFN-γ receptor results in the opposite effect. Deficiency of IFN-γ receptor regulates VSMCs phenotypic switching, such as upregulated contractile markers and downregulated proliferation markers. Mechanistic studies suggest that ablation of IFN-γ receptor prevents VSMCs proliferation, migration and dedifferentiation via STAT1-KLF4 activation.

CONCLUSION

These results reveal that knockout of VSMC-derived IFN-γ receptor potentiates neointimal hyperplasia by preventing VSMCs proliferation, migration and dedifferentiation. Our finding implies that targeting IFN-γ-STAT1-KLF4 signaling could provide a new therapeutic strategy to attenuate vessel restenosis.

Identification of calmodulin-like protein 5 as tumor-suppressor gene silenced during early stage of carcinogenesis in squamous cell carcinoma of uterine cervix

In the course of identifying the molecular mechanism that is related to strong cell-cell adhesion in stratified structures of the squamous epithelium, calmodulin-like protein 5 (CALML5) was identified as a spinous structure-associated protein by producing monoclonal antibodies with the use of the crude intercellular portion of squamous tissue as an immunogen and by subsequent morphologic screening. By electrophoretic mobility shift assay (EMSA) and a series of mutagenesis studies, two transcription factors, ZNF750 and KLF4, by binding in line to the CALML5 gene promoter, were found to play a central role in CALML5 transcription. Knockdown of CALML5 by siRNA in the A431 cell line that expresses high levels of CALML5 resulted in the acceleration of wound confluence in a scratch assay, indicating that CALML5 functions as a tumor-suppressor in uterine cervical cancer. Immunohistochemical evaluation of squamous intraepithelial lesions, carcinoma in situ (CIS) and invasive uterine cancer, revealed a reduction in CALML5 expression during the stages of CIS through various molecular pathways including the blockage of the nuclear translocation of KLF4. Conversely, restoration of the nuclear translocation of KLF4 by inhibiting ERK-signaling reactivated CALML5 expression in ME180 cells expressing low levels of CALML5. Thus, alteration of the p63-ZNF750-KLF4 axis may result in critical functional loss of CALM-related genes during cancer progression. Although the morphological association of CALML5 with the spiny-structure in relation to cell motility is not clear, evaluation of CALML5 expression provides a useful diagnostic indicator of differentiating dysplasia, preinvasive and invasive cervical cancers.

Nobiletin Alleviates Non-alcoholic Steatohepatitis in MCD-Induced Mice by Regulating Macrophage Polarization

Non-alcoholic steatohepatitis (NASH) is an inflammatory disorder that is characterized by chronic activation of the hepatic inflammatory response and subsequent liver damage. The regulation of macrophage polarization in liver is closely related to the progression of NASH. The orphan nuclear receptor retinoic-acid-related orphan receptor α (RORα) and Krüppel-like factor 4 (KLF4) are key regulators which promote hepatic macrophages toward M2 phenotype and protect against NASH in mice. Nobiletin (NOB), a natural polymethoxylated flavone, is previously reported as a RORα regulator in diet-induced obese mice. However, it is still unclear whether NOB has the protective effect on NASH. In this study, we investigated the role of NOB in NASH using a methionine and choline deficient (MCD)-induced NASH mouse model. Our results showed that NOB ameliorated hepatic damage and fibrosis in MCD fed mice. NOB treatment reduced the infiltration of macrophages and neutrophils in the liver in MCD-fed mice. Of importance, NOB significantly increased the proportion of M2 macrophages and the expression of anti-inflammatory factors in vivo and in vitro. Meanwhile, NOB also decreased the population of M1 macrophages and the expression of proinflammatory cytokines. Mechanistically, NOB elevated KLF4 expression in macrophages. Inhibition of KLF4 abolished NOB regulated macrophage polarization. Furthermore, the regulation of NOB in KLF4 expression was dependent on RORα.

Polyphyllin Ⅲ-Induced Ferroptosis in MDA-MB-231 Triple-Negative Breast Cancer Cells can Be Protected Against by KLF4-Mediated Upregulation of xCT

Ferroptosis, which is characterized by the accumulation of intracellular iron and subsequent lipid peroxidation, is a newly discovered form of regulated cell death and plays an important role in tumor suppression. Herein, we showed that Polyphyllin III, which is a major saponin extracted from Paris polyphylla rhizomes, exerted its proliferation-inhibitory effect on MDA-MB-231 triple-negative breast cancer cells mainly through ACSL4-mediated lipid peroxidation elevation and ferroptosis induction. ACSL4 deletion partly attenuated Polyphyllin III-induced ferroptosis. Polyphyllin III treatment also induced KLF4-mediated protective upregulation of xCT, which is the negative regulator of ferroptosis. Interestingly, combination with the xCT inhibitor sulfasalazine (SAS) or downregulation of KLF4 sensitized MDA-MB-231 cells to Polyphyllin III. Furthermore, in vivo xenograft models, SAS significantly sensitized MDA-MB-231 breast cancer cells to Polyphyllin III, likely by enhancing intracellular lipid peroxidation and ferroptosis. The results of this study collectively demonstrated that Polyphyllin III exerts its anticancer effect by inducing ferroptosis via ACSL4 in MDA-MB-231 breast cancer cells. More importantly, we observed for the first time that KLF4-mediated xCT upregulation serves as negative feedback during ferroptosis progression, which might contribute to drug resistance in cancer treatment.

Inhibition of the HEG1-KRIT1 interaction increases KLF4 and KLF2 expression in endothelial cells

The transmembrane protein heart of glass1 (HEG1) directly binds to and recruits Krev interaction trapped protein 1 (KRIT1) to endothelial junctions to form the HEG1-KRIT1 protein complex that establishes and maintains junctional integrity. Genetic inactivation or knockdown of endothelial HEG1 or KRIT1 leads to the upregulation of transcription factors Krüppel-like factors 4 and 2 (KLF4 and KLF2), which are implicated in endothelial vascular homeostasis; however, the effect of acute inhibition of the HEG1-KRIT1 interaction remains incompletely understood. Here, we report a high-throughput screening assay and molecular design of a small-molecule HEG1-KRIT1 inhibitor to uncover acute changes in signaling pathways downstream of the HEG1-KRIT1 protein complex disruption. The small-molecule HEG1-KRIT1 inhibitor 2 (HKi2) was demonstrated to be a bona fide inhibitor of the interaction between HEG1 and KRIT1 proteins, by competing orthosterically with HEG1 through covalent reversible interactions with the FERM (4.1, ezrin, radixin, and moesin) domain of KRIT1. The crystal structure of HKi2 bound to KRIT1 FERM revealed that it occupies the same binding pocket on KRIT1 as the HEG1 cytoplasmic tail. In human endothelial cells (ECs), acute inhibition of the HEG1-KRIT1 interaction by HKi2 increased KLF4 and KLF2 mRNA and protein levels, whereas a structurally similar inactive compound failed to do so. In zebrafish, HKi2 induced expression of klf2a in arterial and venous endothelium. Furthermore, genome-wide RNA transcriptome analysis of HKi2-treated ECs under static conditions revealed that, in addition to elevating KLF4 and KLF2 expression, inhibition of the HEG1-KRIT1 interaction mimics many of the transcriptional effects of laminar blood flow. Furthermore, HKi2-treated ECs also triggered Akt signaling in a phosphoinositide 3-kinase (PI3K)-dependent manner, as blocking PI3K activity blunted the Akt phosphorylation induced by HKi2. Finally, using an in vitro colocalization assay, we show that HKi6, an improved derivative of HKi2 with higher affinity for KRIT1, significantly impedes recruitment of KRIT1 to mitochondria-localized HEG1 in CHO cells, indicating a direct inhibition of the HEG1-KRIT1 interaction. Thus, our results demonstrate that early events of the acute inhibition of HEG1-KRIT1 interaction with HKi small-molecule inhibitors lead to: (i) elevated KLF4 and KLF2 gene expression; and (ii) increased Akt phosphorylation. Thus, HKi's provide new pharmacologic tools to study acute inhibition of the HEG1-KRIT1 protein complex and may provide insights to dissect early signaling events that regulate vascular homeostasis.

Acetyl oxygen benzoate engeletin ester promotes KLF4 degradation leading to the attenuation of pulmonary fibrosis via inhibiting TGFβ1-smad/p38MAPK-lnc865/lnc556-miR-29b-2-5p-STAT3 signal pathway

Pulmonary fibrosis is a common pulmonary interstitial disease of pathogenesis without effective drugs for treatment. Therefore, discovering new and effective drugs is urgently needed. In the present study, we prepared a novel compound named acetyl oxygen benzoate engeletin ester (AOBEE), investigated its effect on experimental pulmonary fibrosis, and proposed a long non-coding RNA (lncRNA)-mediated mechanism of its action. Bleomycin-induced pulmonary fibrosis in mice exhibited that AOBEE improved forced vital capacity (FVC) and alveolar structure and inhibited α-SMA, vimentin, and collagen expression. TGFβ1-stimulated fibroblast L929 cells showed that AOBEE reduced these fibrotic proteins expression and inhibited the activated-fibroblast proliferation and migration. Whole transcriptome sequencing was performed to screen out lncRNA-lnc865 and lnc556 with high expression under bleomycin treatment, but AOBEE caused a considerable decrease in lnc865 and lnc556. Mechanistic study elucidated that AOBEE alleviated pulmonary fibrosis through lnc865- and lnc556-mediated mechanism, in which both lnc865 and lnc556 sponged miR-29b-2-5p to target signal transducer and activator of transcription 3 (STAT3). Further signal pathway inhibitors and the Cignal Finder 45-pathway reporter array illustrated that the up- and downstream pathways were TGFβ1-smad2/3 and p38MAPK, and Krüppel-like factor 4 (KLF4), respectively. In conclusion, AOBEE promoted KLF4 degradation leading to the attenuation of pulmonary fibrosis by inhibiting TGFβ1-smad/p38MAPK-lnc865/lnc556-miR-29b-2-5p-STAT3 signal pathway. We hope this work will provide valuable information to design new drugs and therapeutic targets of lncRNAs for pulmonary fibrosis treatment.

Ghrelin Alleviates Intestinal Dysfunction in Sepsis Through the KLF4/MMP2 Regulatory Axis by Activating SIRT1

Intestinal barrier dysfunction is an important contributor to morbidity caused by sepsis. This study investigates the molecular mechanism by which Ghrelin affects intestinal dysfunction in rat model of sepsis. A rat model of sepsis was established by cecal ligation and puncture (CLP), revealing that Ghrelin was downregulated when sepsis occurs. Increases in the levels of inflammatory factors tumor necrosis factor α (TNF-α), interleukin-1 (IL-1β), IL-6, gastrin, γ-H2AX and 8-OHdG was also detected in this model system, as was an overall increase in oxidative stress. Introduction of exogenous Ghrelin inhibited these increases in inflammatory response and oxidative stress, leading to a reduction of overall sepsis-induced intestinal dysfunction. Ghrelin was then shown to activate SIRT1 expression in vitro, while SIRT1 was found to co-express with KLF4, which in turn was predicted to bind to matrix metalloproteinase 2 (MMP2) promoter. Finally, gain- and loss-of-function experiment demonstrated that SIRT1 upregulated the expression of KLF4 to downregulate MMP2. Collectively, Ghrelin inhibits the oxidative stress and intestinal dysfunction to attenuate sepsis by activating SIRT1 and regulating a KLF4/MMP2 regulatory axis.

CDR1as regulated by hnRNPM maintains stemness of periodontal ligament stem cells via miR-7/KLF4

CDR1as is a well‐identified circular RNA with regulatory roles in a variety of physiological processes. However, the effects of CDR1as on stemness of periodontal ligament stem cells (PDLSCs) and the underlying mechanisms remain unclear. In this study, we detect CDR1as in human PDLSCs, and subsequently demonstrate that CDR1as maintains PDLSC stemness. Knockdown of CDR1as decreases the expression levels of stemness‐related genes and impairs the cell's multi‐differentiation and cell migration abilities, while overexpression of CDR1as increases the expression levels of stemness‐related genes and enhances these abilities. Furthermore, our results indicate that the RNA‐binding protein hnRNPM directly interacts with CDR1as and regulates its expression in PDLSCs. In addition, we show that CDR1as promotes the expression of stemness‐related genes in PDLSCs by inhibiting miR‐7‐mediated suppression of KLF4 expression. Collectively, our results demonstrate that CDR1as participates in the molecular circuitry that regulates PDLSC stemness.