Cooperativity of c-MYC with Krüppel-Like Factor 6 Splice Variant 1 induces phenotypic plasticity and promotes prostate cancer progression and metastasis

Metastasis remains a major cause of morbidity and mortality in men with prostate cancer, and the functional impact of the genetic alterations, alone or in combination, driving metastatic disease remains incompletely understood. The proto-oncogene c-MYC, commonly deregulated in prostate cancer. Transgenic expression of c-MYC is sufficient to drive the progression to prostatic intraepithelial neoplasia and ultimately to moderately differentiated localized primary tumors, however, c-MYC-driven tumors are unable to progress through the metastatic cascade, suggesting that a "second-hit" is necessary in the milieu of aberrant c-MYC-driven signaling. Here, we identified cooperativity between c-MYC and KLF6-SV1, an oncogenic splice variant of the KLF6 gene. Transgenic mice that co-expressed KLF6-SV1 and c-MYC developed progressive and metastatic prostate cancer with a histological and molecular phenotype like human prostate cancer. Silencing c-MYC expression significantly reduced tumor burden in these mice supporting the necessity for c-MYC in tumor maintenance. Unbiased global proteomic analysis of tumors from these mice revealed significantly enriched vimentin, a dedifferentiation and pro-metastatic marker, induced by KLF6-SV1. c-MYC-positive tumors were also significantly enriched for KLF6-SV1 in human prostate cancer specimens. Our findings provide evidence that KLF6-SV1 is an enhancer of c-MYC-driven prostate cancer progression and metastasis, and a correlated genetic event in human prostate cancer with potential translational significance.

Machine learning-based classification of deubiquitinase USP26 and its cell proliferation inhibition through stabilizing KLF6 in cervical cancer

OBJECTIVE

We aim to accurately distinguish ubiquitin-specific proteases (USPs) from other members within the deubiquitinating enzyme families based on protein sequences. Additionally, we seek to elucidate the specific regulatory mechanisms through which USP26 modulates Krüppel-like factor 6 (KLF6) and assess the subsequent effects of this regulation on both the proliferation and migration of cervical cancer cells.

METHODS

All the deubiquitinase (DUB) sequences were classified into USPs and non-USPs. Feature vectors, including 188D, n-gram, and 400D dimensions, were extracted from these sequences and subjected to binary classification via the Weka software. Next, thirty human USPs were also analyzed to identify conserved motifs and ascertained evolutionary relationships. Experimentally, more than 90 unique DUB-encoding plasmids were transfected into HeLa cell lines to assess alterations in KLF6 protein levels and to isolate a specific DUB involved in KLF6 regulation. Subsequent experiments utilized both wild-type (WT) USP26 overexpression and shRNA-mediated USP26 knockdown to examine changes in KLF6 protein levels. The half-life experiment was performed to assess the influence of USP26 on KLF6 protein stability. Immunoprecipitation was applied to confirm the USP26-KLF6 interaction, and ubiquitination assays to explore the role of USP26 in KLF6 deubiquitination. Additional cellular assays were conducted to evaluate the effects of USP26 on HeLa cell proliferation and migration.

RESULTS

1. Among the extracted feature vectors of 188D, 400D, and n-gram, all 12 classifiers demonstrated excellent performance. The RandomForest classifier demonstrated superior performance in this assessment. Phylogenetic analysis of 30 human USPs revealed the presence of nine unique motifs, comprising zinc finger and ubiquitin-specific protease domains. 2. Through a systematic screening of the deubiquitinase library, USP26 was identified as the sole DUB associated with KLF6. 3. USP26 positively regulated the protein level of KLF6, as evidenced by the decrease in KLF6 protein expression upon shUSP26 knockdown in both 293T and Hela cell lines. Additionally, half-life experiments demonstrated that USP26 prolonged the stability of KLF6. 4. Immunoprecipitation experiments revealed a strong interaction between USP26 and KLF6. Notably, the functional interaction domain was mapped to amino acids 285-913 of USP26, as opposed to the 1-295 region. 5. WT USP26 was found to attenuate the ubiquitination levels of KLF6. However, the mutant USP26 abrogated its deubiquitination activity. 6. Functional biological assays demonstrated that overexpression of USP26 inhibited both proliferation and migration of HeLa cells. Conversely, knockdown of USP26 was shown to promote these oncogenic properties.

CONCLUSIONS

1. At the protein sequence level, members of the USP family can be effectively differentiated from non-USP proteins. Furthermore, specific functional motifs have been identified within the sequences of human USPs. 2. The deubiquitinating enzyme USP26 has been shown to target KLF6 for deubiquitination, thereby modulating its stability. Importantly, USP26 plays a pivotal role in the modulation of proliferation and migration in cervical cancer cells.

TNF-α stimulated exosome derived from fibroblast-like synoviocytes isolated from rheumatoid arthritis patients promotes HUVEC migration, invasion and angiogenesis by targeting the miR-200a-3p/KLF6/VEGFA axis

The pathogenesis of rheumatoid arthritis (RA) is heavily impacted by the inflammation and activation of fibroblast-like synoviocytes (FLS). The objective of this investigation is to clarify the involvement of exosomes derived from FLS stimulated by tumour necrosis factor α (TNF-α) in angiogenesis and the underlying mechanisms. FLS cells were obtained from synovial fluid of RA patients and exosomes were obtained from FLS cell supernatant with TNF-α stimulation by ultracentrifugation. Exosomes were subsequently analysed using transmission electron microscopy, nanoparticle tracking analysis, and western blotting. The functional effects of exosomes with TNF-α stimulation on human umbilical vein endothelial cells (HUVEC) migration, invasion, and angiogenesis was evaluated using wound scratch healing test, transwell invasion assay, and tube formation assay. DNA nanoball-seq (DNBSEQ) sequencing platform was utilised to analysis different expression miRNA from exosomes, miRNA and mRNA from HUVEC. The expression level of miR-200a-3p was determined through quantitative real-time polymerase chain reaction (qRT-PCR). The quantification of KLF6 and VEGFA expression levels were performed by qRT-PCR and western blot analysis. The validation of the association between miR-200a-3p and KLF6 was established through a fluorescence enzyme reporting assay. In comparison to exosome induced by PBS, exosome induced by TNF-α exhibited a substantial exacerbation of invasion, migration, and angiogenesis in HUVEC. 4 miRNAs in exosomes and HUVEC cells, namely miR-1246, miR-200a-3p, miR-30a-3p, and miR-99b-3p was obtained. MiR-200a-3p maintained high consistency with the sequencing results. We obtained 5 gene symbols, and KLF6 was chose for further investigation. The expression of miR-200a-3p in exosomes induced by TNF-α and in HUVEC treated with these exosomes demonstrated a significantly increase. Additionally, HUVEC cells displayed a notable decrease in KLF6 expression and a significant elevation in VEGFA expression. This was further confirmed by the fluorescence enzyme report assay, which provided evidence of the direct targeting of KLF6 by miR-200a-3p. Exosomes induced by TNF-α have the ability to enhance the migration, invasion, and angiogenesis of HUVEC cells via the miR-200a-3p/KLF6/VEGFA axis.

Exosomal miR-181d-5p Derived from Rapamycin-Conditioned MDSC Alleviated Allograft Rejection by Targeting KLF6

Immune rejection and side effects of long-term administration of immunosuppressants are the two major obstacles to allograft acceptance and tolerance. The immunosuppressive extracellular vesicles (EVs)-based approach has been proven to be effective in treating autoimmune/inflammatory disorders. Herein, the anti-rejection advantage of exosomes (Rapa-Exo) from rapamycin-conditioned myeloid-derived suppressor cells (MDSCs) over exosomes (Exo-Nor) from the untreated MDSCs is shown. The exosomal small RNA sequencing and loss-of-function assays reveal that the anti-rejection effect of Rapa-Exo functionally relies on miR-181d-5p. Through target prediction and double-luciferase reporter assay, Kruppel-like factor (KLF) 6 is identified as a direct target of miR-181d-5p. Finally, KLF6 knockdown markedly resolves inflammation and prolongs the survival of corneal allografts. Taken together, these findings support that Rapa-Exo executes an anti-rejection effect, highlighting the immunosuppressive EVs-based treatment as a promising approach in organ transplantation.

Identification of genetic associations and functional SNPs of bovine KLF6 gene on milk production traits in Chinese holstein

BACKGROUND

Our previous research identified the Kruppel like factor 6 (KLF6) gene as a prospective candidate for milk production traits in dairy cattle. The expression of KLF6 in the livers of Holstein cows during the peak of lactation was significantly higher than that during the dry and early lactation periods. Notably, it plays an essential role in activating peroxisome proliferator-activated receptor α (PPARα) signaling pathways. The primary aim of this study was to further substantiate whether the KLF6 gene has significant genetic effects on milk traits in dairy cattle.

RESULTS

Through direct sequencing of PCR products with pooled DNA, we totally identified 12 single nucleotide polymorphisms (SNPs) within the KLF6 gene. The set of SNPs encompasses 7 located in 5' flanking region, 2 located in exon 2 and 3 located in 3' untranslated region (UTR). Of these, the g.44601035G > A is a missense mutation that resulting in the replacement of arginine (CGG) with glutamine (CAG), consequently leading to alterations in the secondary structure of the KLF6 protein, as predicted by SOPMA. The remaining 7 regulatory SNPs significantly impacted the transcriptional activity of KLF6 following mutation (P < 0.005), manifesting as changes in transcription factor binding sites. Additionally, 4 SNPs located in both the UTR and exons were predicted to influence the secondary structure of KLF6 mRNA using the RNAfold web server. Furthermore, we performed the genotype-phenotype association analysis using SAS 9.2 which found all the 12 SNPs were significantly correlated to milk yield, fat yield, fat percentage, protein yield and protein percentage within both the first and second lactations (P < 0.0001 ~ 0.0441). Also, with Haploview 4.2 software, we found the 12 SNPs linked closely and formed a haplotype block, which was strongly associated with five milk traits (P < 0.0001 ~ 0.0203).

CONCLUSIONS

In summary, our study represented the KLF6 gene has significant impacts on milk yield and composition traits in dairy cattle. Among the identified SNPs, 7 were implicated in modulating milk traits by impacting transcriptional activity, 4 by altering mRNA secondary structure, and 1 by affecting the protein secondary structure of KLF6. These findings provided valuable molecular insights for genomic selection program of dairy cattle.

MicroRNA-22-3p in human umbilical cord mesenchymal stem cell-secreted exosomes inhibits granulosa cell apoptosis by targeting KLF6 and ATF4-ATF3-CHOP pathway in POF mice

BACKGROUND

Human umbilical cord mesenchymal stem cells (hUCMSCs)-derived exosomes carrying microRNAs (miRNAs) have promising therapeutic potential in various disorders, including premature ovarian failure (POF). Previous evidence has revealed the low plasma level of miR-22-3p in POF patients. Nevertheless, exosomal miR-22-3p specific functions underlying POF progression are unclarified.

METHODS

A cisplatin induced POF mouse model and in vitro murine ovarian granulosa cell (mOGC) model were established. Exosomes derived from miR-22-3p-overexpressed hUCMSCs (Exos-miR-22-3p) were isolated. CCK-8 assay and flow cytometry were utilized for measuring mOGC cell viability and apoptosis. RT-qPCR and western blotting were utilized for determining RNA and protein levels. The binding ability between exosomal miR-22-3p and Kruppel-like factor 6 (KLF6) was verified using luciferase reporter assay. Hematoxylin-eosin staining, ELISA, and TUNEL staining were performed for examining the alteration of ovarian function in POF mice.

RESULTS

Exos-miR-22-3p enhanced mOGC viability and attenuated mOGC apoptosis under cisplatin treatment. miR-22-3p targeted KLF6 in mOGCs. Overexpressing KLF6 reversed the above effects of Exos-miR-22-3p. Exos-miR-22-3p ameliorated cisplatin-triggered ovarian injury in POF mice. Exos-miR-22-3p repressed ATF4-ATF3-CHOP pathway in POF mice and cisplatin-treated mOGCs.

CONCLUSION

Exosomal miR-22-3p from hUCMSCs alleviates OGC apoptosis and improves ovarian function in POF mouse models by targeting KLF6 and ATF4-ATF3-CHOP pathway.

MiRNA-21-5p Accelerates EMT and Inhibits Apoptosis of Laryngeal Carcinoma via Inhibiting KLF6 Expression

The incidence of laryngeal carcinoma accounts for 1 to 5% of systemic malignancies and ranks second among head and neck malignancies. Screening more effective targets are meaningful for the treatment of laryngeal carcinoma. The purpose was to research the action of miR-21-5p in the occurrence of laryngeal carcinoma. Genecards combined with g:profiler was used for cluster analysis to predict gene-related miRNAs. Q-PCR assay was performed for measuring the level of miR-21-5p and Kruppel-like factor 6 (KLF6). miR-21-5p-mimic, miR-21-5p-inhibitor and sh-KLF6 were transfected using LipofectamineTM 2000. Both CCK-8 and EdU experiments were undertaken to detect cell proliferation ability. Western blot was used to detect apoptosis and epithelial-mesenchymal transition (EMT) related proteins. Wound healing assay and transwell assay were undertaken for migration and invasion, respectively. Three online software (ENCORI, miRWalk, and miRDB) were applied to screen the downstream of miR-21-5p. At the same time, a dual-luciferase reporter experiment was processed to verify the binding. Finally, a rescue experiment was applied to reveal the mediating role of miR-21-5p and KLF6. MiR-21-5p expressed highly in laryngeal carcinoma tissues and cell lines. Knockdown of miR-21-5p reduced the EMT, while enhancing apoptosis of laryngeal carcinoma cell lines. MiR-21-5p targeted KLF6 with negative relationships. The rescue assay results confirmed that sh-KLF6 rescued the action of miR-21-5p knockdown in developing laryngeal carcinoma cells. MiR-21-5p promotes the occurrence and development of laryngeal cancer by targeting KLF6. This finding may provide new insights into miRNA as a biomarker for diagnosing and treating laryngeal carcinoma in the future.

Hypoxia-induced miR-653 enhances colorectal cancer progression by targeting circSETD3/KLF6 axis

The present work focused on exploring the role and underlying molecular mechanism of action of the non-coding RNA (miRNA/circRNA) in colorectal cancer (CRC). Here, we found that miR-653 was dramatically upregulated in CRC tissues and cells. CRC Patients with high miR-653 level possessed poor prognosis. miR-653 elevated proliferation, migration, and invasion, meanwhile suppressed apoptosis of CRC cells. Furthermore, circSETD3 directly sponged miR-653 and negatively regulate miR-653 to affect proliferation, migration, invasion, and apoptosis of CRC cells. Moreover, miR-653 served as carcinoma-promoting gene via targeting KLF6, and circSETD3 knockdown significantly reversed the inhibitory effect of KLF6 overexpression on CRC cells. In addition, hypoxia obviously increased expression of miR-653. Knockdown of miR-653 decreased the effects of hypoxia on CRC cell proliferation, migration and invasion. Taken together, these findings indicated that circSETD3/miR-653/KLF6 axis may be an effective therapeutic target for CRC patients.

MUTYH and KLF6 gene expression fluctuations in tumor tissue and tumor margins tissues of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is one of the most important cancers in the world, and its prevalence varies depending on the geographical area. Genetically, tumor regeneration in CRC as a multi-step process involves activating mutations in protocogenes and losing the function of tumor suppressor genes as well as DNA repair and recovery genes. Occur in this way, our goal was to investigate the expression of KLF6 genes as a tumor suppressor and MUTYH involved in the DNA repair process in colorectal cancer.

METHODS

This research was conducted during the years 2019-2018 in Razi Hospital, Rasht. The subjects included 30 tumoral and 30 non-tumoral tissues of colorectal cancer and 20 healthy controls. The real-time PCR method was used to investigate the gene expression. For data analysis by SPSS, parametric statistical tests ANOVA and T test and regression analysis were used and p value values less than 0.05 were considered significant.

RESULTS

The expression of KLF6 gene in tumoral tissues showed a significant decrease compared to non-tumoral tissues (P = 0.04). Also, the expression of MUTYH gene in tumor tissue showed a significant decrease compared to non-tumoral (P = 0.02) and this decrease in MUTYH gene expression had a significant relationship with increasing tumor stage (P = 0.01).

CONCLUSION

These findings suggest that decreased expression of KLF6 and MUTYH genes in the study population has a significant relationship with colorectal cancer and can be considered as tumor marker in diagnostic purpose.

Deciphering the Key Regulatory Roles of KLF6 and Bta-miR-148a on Milk Fat Metabolism in Bovine Mammary Epithelial Cells

MicroRNAs (miRNAs) are non-coding RNAs that regulate the expression of their target genes involved in many cellular functions at the post-transcriptional level. Previously, bta-miR-148a showed significantly high expression in bovine mammary epithelial cells (BMECs) of Chinese Holstein cows producing high milk fat compared to those with low milk fat content. Here, we investigated the role of bta-miR-148a through targeting Krüppel-like factor 6 (KLF6) and further analyzed the role of KLF6 in regulating fat metabolism through targeting PPARA, AMPK/mTOR/PPARG, and other fat marker genes in BMECs of Chinese Holstein. The bioinformatics analysis showed that the 3’ UTR of KLF6 mRNA possesses the binding sites for bta-miR-148a, which was further verified through dual-luciferase reporter assay. The BMECs were transfected with bta-miR-148a-mimic, inhibitor, and shNC, and the expression of KLF6 was found to be negatively regulated by bta-miR-148a. Moreover, the contents of triglyceride (TG), and cholesterol (CHO) in BMECs transfected with bta-miR-148a-mimic were significantly lower than the contents in BMECs transfected with bta-miR-148a-shNC. Meanwhile, the TG and CHO contents were significantly increased in BMECs transfected with bta-miR-148a-inhibitor than in BMECs transfected with bta-miR-148a-shNC. In addition, the TG and CHO contents were significantly decreased in BMECs upon the down-regulation of KLF6 through transfection with pb7sk-KLF6-siRNA1 compared to the control group. Contrarily, when KLF6 was overexpressed in BMECs through transfection with pBI-CMV3-KLF6, the TG and CHO contents were significantly increased compared to the control group. Whereas, the qPCR and Western blot evaluation of PPARA, AMPK/mTOR/PPARG, and other fat marker genes revealed that all of the genes were considerably down-regulated in the KLF6-KO-BMECs compared to the normal BMECs. Taking advantage of deploying new molecular markers and regulators for increasing the production of better-quality milk with tailored fat contents would be the hallmark in dairy sector. Hence, bta-miR-148a and KLF6 are potential candidates for increased milk synthesis and the production of valuable milk components in dairy cattle through marker-assisted selection in molecular breeding. Furthermore, this study hints at the extrapolation of a myriad of functions of other KLF family members in milk fat synthesis.

Inhibition of KLF6 reduces the inflammation and apoptosis of type II alveolar epithelial cells in acute lung injury

BACKGROUND

The development of acute lung injury (ALI) into a severe stage leads to acute respiratory distress syndrome (ARDS). The morbidity and mortality of ALI and ARDS are very high. Objective: This study is aimed to explore the effect of Krüppel-like factor 6 (KLF6) on lipopolysaccharide (LPS)-induced type II alveolar epithelial cells in ALI by interacting with cysteine-rich angiogenic inducer 61 (CYR61).

MATERIAL AND METHODS

ALI mice model and LPS-induced type II alveolar epithelial cells were conducted to simulate ALI in vivo and in vitro. The messenger RNA (mRNA) and protein expression of KLF6 in lung tissues were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Pathological changes in lung tissues were observed by hematoxylin and eosin (H&E) staining. The viability and KLF6 expression of A549 cells treated with different concentrations of LPS were detected by cell counting kit-8 (CCK-8) assay, RT-qPCR, and Western blot analysis. After indicated treatment, the viability and apoptosis of A549 cells were analyzed by CCK-8 and TUNEL assays, and the inflammation factors of A549 cells were detected by Enzyme-linked-immunosorbent serologic assay, RT-qPCR, and Western blot analysis. The combination of KLF6 and CYR61 was determined by chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase reporter assay.

RESULTS

KLF6 expression was increased in lung tissues of ALI mice and LPS-induced A549 cells. Interference with KLF6 improved the viability, reduced the inflammatory damage, and promoted the apoptosis of LPS-induced A549 cells. In addition, KLF6 could bind to CYR61. Interference with KLF6 could decrease CYR61 expression in LPS-induced A549 cells. LPS also enhanced the TLR4/MYD88 signaling pathway, which was reversed by KLF6 interference. The above phenomena in LPS-induced A549 cells transfected with Si-KLF6 could be reversed by overexpression of CYR61.

CONCLUSION

Inhibition of KLF6 promoted the viability and reduced the inflammation and apoptosis of LPS-induced A549 cells, which was reversed by CYR61.

Downregulation of krüppel-like factor 6 expression modulates extravillous trophoblast cell behavior by increasing reactive oxygen species

INTRODUCTION

Placental extravillous trophoblasts play a crucial role in the establishment of a healthy pregnancy. Reactive oxygen species (ROS) may contribute to their differentiation and function as mediators in signaling processes or might cause oxidative stress resulting in trophoblast dysfunction. The krüppel-like transcription factor 6 (KLF6) regulates many genes involved in essential cell processes where ROS are also involved. However, whether KLF6 regulates ROS levels has not been previously investigated.

MATERIALS AND METHODS

KLF6 was silenced by siRNAs in HTR8-SV/neo cells, an extravillous trophoblast model. Total and mitochondrial ROS levels, as well as mitochondrial membrane potential and apoptosis were analyzed by flow cytometry. The expression of genes and proteins of interest were analyzed by qRT-PCR and Western blot, respectively. Cell response to oxidative stress, proliferation, viability, morphology, and migration were evaluated.

RESULTS

KLF6 downregulation led to an increase in ROS and NOX4 mRNA levels, accompanied by reduced cell proliferation and increased p21 protein expression. Catalase activity, 2-Cys peroxiredoxin protein levels, Nrf2 cytoplasmic localization and hemoxygenase 1 expression, as well as mitochondrial membrane potential and cell apoptosis were not altered suggesting that ROS increase is not associated with cellular damage. Instead, KLF6 silencing induced cytoskeleton modifications and increased cell migration in a ROS-dependent manner.

DISCUSSION

Present data reveal a novel role of KLF6 on ROS balance and signaling demonstrating that KLF6 downregulation induces an increase in ROS levels that contribute to extravillous trophoblast cell migration.

Decreased expression of miR-204-3p in peripheral blood and wound margin tissue associated with the onset and poor wound healing of diabetic foot ulcers

To investigate the relationship between small non-coding RNA-204-3p (miR-204-3p) and the onset and wound healing of diabetic foot ulcers (DFU) and the underlying molecular mechanism, sixty four newly diagnosed patients with T2DM without DFU (T2DM group), 82 T2DM patients with DFU (DFU group), and 60 controls with normal glucose tolerance (NC group) were included. Quantitative real-time PCR (qRT-PCR) method was used to determine miR-204-3p expression levels in peripheral blood and wound margin tissue of subjects, and to analyse the relationship between the expression of miR-204-3p and wound healing. In vitro experiments were also performed to understand the effect of miR-204-3p on high glucose induced injury of HaCaT cells (human keratinocytes). The results showed that miR-204-3p expression level of peripheral blood in the T2DM group was marked lower than that in the NC group [2.38 (1.31-5.04) vs 3.27 (1.51-6.98)] (P < .05). Similarly, the miR-204-3p expression level of peripheral blood in the DFU group was significantly lower than the T2DM group [1.15 (0.78-2.89) vs 2.38 (1.31-5.04)] (P < .01). The expression level of miR-204-3p in peripheral blood and wound margin tissues of DFU patients was positively correlated with the healing rate of foot ulcers after 8 weeks (P < .05). Multifactorial logistic regression analysis showed that decreased expression of miR-204-3p in peripheral blood was an independent risk factor for DFU (OR = 2.95, P < .05). The results of in vitro experiments showed that miR-204-3p could improve the proliferation and migration of HKC cells and reduce the proportion of apoptosis of HKC cells by targeted regulation of zinc finger protein Kruppel like factor 6 (KLF6) in high glucose environment. Therefore, the decreased expression of miR-204-3p in peripheral blood and wound tissue of T2DM patients is closely related to the occurrence and poor wound healing of DFU. The down-regulated expression of miR-204-3p can reduce its ability to antagonise the functional damage of keratinocytes induced by high-glucose conditions. These results will provide potential targets for the treatment of DFU.

[KLF6 Super-enhancer Regulates Cell Proliferation by Recruiting GATA2 and SOX10 in Human Hepatoma Cells]

Super-enhancer consists of a large cluster of transcription enhancers that regulates the expression of genes playing an important role in the growth and development of malignant tumors. Recently, several attempts for the identification of super-enhancers have been made, but their functional role in tumor cells remains unclear. This paper aims at elucidating the functional properties of KLF6 super-enhancer related to the growth regulation of HepG2 cells, in relation to transcription factors (TFs). First, some TFs specifying KLF6 super enhancer were identified using CRISPR/Cas9 system and siRNA. Then, their effects on the expression of the target gene KLF6 were assessed. Last, their influence on the proliferation of tumor cells was considered using the MTT method. The study shows that the active enhancers of KLF6 super-enhancer recruit GATA2 and SOX10 TFs to control the expression of the target gene, KLF6. Our findings suggest that the activity of KLF6 super-enhancer is regulated by two TFs (GATA2 and SOX10), and its targeting may be a potential therapeutic strategy for the liver cancer therapy.

Association between KLF6 rs3750861 polymorphism and plasma ceramide concentrations in post-menopausal women with type 2 diabetes

BACKGROUND AND AIM

Based on the emerging role of Kruppel-like factor 6 (KLF6) in lipid metabolism, we examined whether there is a relationship between the KLF6 rs3750861 genetic variant and plasma ceramide levels in people with type 2 diabetes mellitus (T2DM).

METHODS AND RESULT

We measured six previously identified plasma ceramides, which have been associated with increased cardiovascular risk [Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/20:0), Cer(d18:1/22:0), Cer(d18:1/24:0) and Cer(d18:1/24:1)] amongst 101 Caucasian post-menopausal women with T2DM, who consecutively attended our diabetes outpatient service during a 3-month period. Plasma ceramides were measured by targeted liquid chromatography-tandem mass spectrometry assay. Genotyping of the KLF6 rs3750861 polymorphism was performed by TaqMan-Based RT-PCR system. Overall, 87 (86.1%) patients had KLF6 rs3750861 C/C genotype and 14 (13.9%) had C/T or T/T genotypes. After adjustment for age, diabetes-related variables, use of lipid-lowering drugs and other potential confounders, patients with C/T or T/T genotypes had higher plasma Cer(d18:1/18:0) (0.159 ± 0.05 vs. 0.120 ± 0.04 μmol/L, p = 0.012), Cer(d18:1/20:0) (0.129 ± 0.04 vs. 0.098 ± 0.03 μmol/L, p = 0.008), and Cer(d18:1/24:1) (1.236 ± 0.38 vs. 0.978 ± 0.36 μmol/L, p = 0.032) compared with those with C/C genotype.

CONCLUSIONS

The C/T or T/T genotypes of rs3750861 in the KLF6 gene were closely associated with higher levels of specific plasma ceramides in post-menopausal women with T2DM.

miR-106a-5p carried by tumor-derived extracellular vesicles promotes the invasion and metastasis of ovarian cancer by targeting KLF6

Tumor-derived extracellular vesicles (EVs) promote ovarian cancer (OC) metastasis by carrying microRNAs (miRs). This study investigated the mechanism of miR-106a-5p carried by OC cell-derived EVs in OC. miR-106a-5p expression in OC tissues and cells was measured. EVs were extracted from SKOV3 cells and normal cells. The internalization of EVs in OC cells was observed. OC cells were treated with SKOV3-EVs or SKOV3-EVs overexpressing miR-106a-5p to detect the proliferation, migration, and invasion. The expression levels of miR-106a-5p, KLF6, and PTTG1 were detected and their binding relationships were identified. Combined experiments were designed to detect the effects of KLF6 and PTTG1 on OC cells. A xenograft tumor experiment was performed to verify the mechanism of EVs-miR-106a-5p and KLF6 in OC metastasis. Consequently, miR-106a-5p was enhanced in OC and correlated with OC metastasis. SKOV3-EVs promoted the proliferation, migration, and invasion of OC cells. Mechanistically, EVs carried miR-106a-5p into other OC cells, inhibited KLF6, reduced the binding of KLF6 to the PTTG1 promoter, and upregulated PTTG1 transcription. Overexpression of KLF6 or silencing of PTTG1 attenuated the promoting effect of EVs-miR-106a-5p on OC cells. EVs-miR-106a-5p facilitated OC metastasis via the KLF6/PTTG1 axis. To conclude, OC cell-derived EVs facilitated the progression and metastasis of OC via the miR-106a-5p/KLF6/PTTG1 axis.

MiR-181 enhances proliferative and migratory potentials of retinal endothelial cells in diabetic retinopathy by targeting KLF6

PURPOSE

We aimed to uncover the role of microRNA-181 (miR-181) in the disease onset of diabetic retinopathy (DR) and its underlying mechanism.

METHODS

MiR-181 levels in plasma and aqueous humor samples of non-proliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR) and healthy subjects were analyzed by microarray and quantitative real-time polymerase chain reaction (qRT-PCR). Proliferative and migrative capacities of human retinal endothelial cells (hRECs) regulated by miR-181 were assessed. The binding between miR-181 and kruppel-like factor 6 (KLF6) was verified by dual-luciferase reporter assay.

RESULTS

MiR-181 was upregulated in plasma and aqueous humor samples of NPDR and PDR patients. Overexpression of miR-181 stimulated hRECs to proliferate and migrate. KLF6 was the downstream gene binding miR-181, which was involved in the regulation of hRECs by miR-181.

CONCLUSIONS

MiR-181 is upregulated in plasma and aqueous humor of DR patients. It enhances proliferative and migratory potentials of retinal endothelial cells by targeting KLF6.

Long non-coding RNA ZFAS1 regulates cell proliferation and invasion in cervical cancer via the miR-190a-3p/KLF6 axis

Long non-coding RNA (lncRNA) ZFAS1 (zinc finger antisense 1) was demonstrated to play critical roles in various cancer progression. However, the functions of ZFAS in cervical cancers (CC) are unclear. Human CC cell lines were used for in vitro experiments. RT-qPCR (Real Time Quantitative PCR) was performed to detect the expression of ZFAS1, microRNA-190a-3p (miR-190a-3p) and Kruppel-like factor 6 (KLF6). Cell proliferation, invasion and migration assays were used to investigate biological behaviors of CC cells related to CC progression. The relationship of KLF6 to ZFAS1 and miR-190a-3p was analyzed by circRIP and luciferase reporter assay. In addition, in vivo experiment was carried out to explore the function of ZFAS1 in tumor growth of CC. The expression levels of ZFAS1 and KLF6 were both significantly elevated, while the expression of miR-190a-3p was inhibited in CC tumor tissues. In addition, ZFAS1 influenced CC tumor growth through miR-190a-3p. KLF6 was a target of miR-190a-3p and inhibited miR-190a-3p-induced CC tumor growth. Furthermore, KLF6 was negatively regulated by miR-190a-3p, but positively regulated by ZFAS1. Overexpression of ZFAS1 and inhibition of miR-190a-3p significantly increased the expression levels of KLF6. Finally, in vitro assays demonstrated that inhibition of ZFAS1 reduced CC tumor growth and the expression levels of KLF6, but increased the expression levels of miR-190a-3p. ZFAS1 could regulate CC pathogenesis via regulating the miR-190a-3p/KLF6 axis, which might be considered as new CC therapeutic targets.

RNA-Seq reveals the potential molecular mechanisms of bovine KLF6 gene in the regulation of adipogenesis

Marbling influences the taste and tenderness of meat and is the main determinant of carcass quality in many countries. This study aims to investigate the influence of KLF6 (Kruppel Like Factor 6) and associated molecular mechanisms on lipid metabolism in bovine adipocytes. In the current study, KLF6 gene expression was down regulated via siRNA (small interfering RNA) in bovine adipocytes in vitro. Subsequently, adipogenic cells were collected from the culture media after 9 days, and subjected to fluorescent imaging and RNA sequencing. After confirming that KLF6 was down regulated in bovine adipocytes by siRNA, differential gene expression analysis was used to characterize the infuence of KLF6 on gene expression profiles in bovine adipocytes. A total of 10,812 genes were characterized as differentially expressed genes (DEGs) of which, 109 were up-regulated and 62 were down-regulated genes. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis identified that the DEGs were associated with lipid metabolism, carbohydrate metabolism, cell growth and death, cancer, and the signaling pathways for calcium, AMPK (Adenosine Monophosphate-Activated Protein Kinase), PI3K-Akt (Phosphatidylinositol 3-kinase), PPAR (Peroxisome proliferator-activated receptors), MAPK (mitogen-activated protein kinase), cAMP (Cyclic adenosine monophosphate), and Wnt (Wingless-related integration site). Similarly, gene ontology analysis indicated that down-regulation of KLF6 gene significantly up regulated the genes that regulate adipogenesis, differentiation and regulation of adipocytes and homeostasis of bovine adipocytes, specifically regulating the cell-type specific apoptotic action, negative regulation of apoptotic pathways, programmed cell death, and growth. Results indicate that KLF6 has a role in regulating lipid metabolism in bovine adipocytes. These findings provide evidence that may inform further investigations into molecular mechanisms that underlie the role of bovine KLF6 gene in regulating adipogenesis.

Apoptotic bodies extracted from adipose mesenchymal stem cells carry microRNA-21-5p to induce M2 polarization of macrophages and augment skin wound healing by targeting KLF6

BACKGROUND

Adipose-derived mesenchymal stem cells (adMSCs) are suggested as potential tools for the treatment of regenerative diseases, including tissue repair. This study aimed to explore the function of adMSC-derived apoptotic bodies in skin wound healing and the molecules of action.

METHODS

The acquired adMSCs and their-derived apoptotic bodies were identified. A murine model of full-thickness skin wounds was treated with apoptotic bodies. The wound healing process of mice and the pathological changes in wound tissues were examined. Ana-1 macrophages were treated with lipopolysaccharide (LPS) and apoptotic bodies for in vitro experiments. Polarization of macrophages was examined by immunofluorescence staining of the specific biomarkers and ELISA kits. Dermal microvascular endothelial cells (DMECs) or dermal fibroblasts (DFs) were co-cultured with apoptotic bodies or the LPS- and apoptotic bodies-treated Ana-1 cells. Downstream molecules mediated by apoptotic bodies were screened by microarray and bioinformatic analyses.

RESULTS

Apoptotic bodies treatment accelerated skin wound healing in mice and promoted formation of granulation tissues and blood vessels in wound tissues. Apoptotic bodies treatment induced M2 polarization of macrophages. The angiogenesis ability of DMECs, and the viability and migration of DFs were increased when co-cultured with the apoptotic bodies-treated Ana-1 cells. MicroRNA (miR)-21-5p was abundantly expressed in ABs, and kruppel like factor 6 (KLF6) mRNA was confirmed as a target of miR-21-5p. Overexpression of KLF6 reduced M2 polarization of macrophages and blocked the promoting effect of apoptotic bodies on wound healing in vitro and in vivo.

CONCLUSION

miR-21-5p carried by adMSC-derived apoptotic bodies targets KLF6 to induce M2 polarization of macrophages and augment skin wound healing.

Krüppel-like factor 6 (KLF6) requires its amino terminal domain to promote villous trophoblast cell fusion

INTRODUCTION

Villous cytotrophoblast (vCTB) cells fuse to generate and maintain the syncytiotrophoblast layer required for placental development and function. Krüppel-like factor 6 (KLF6) is a ubiquitous transcription factor with an N-terminal acidic transactivation domain and a C-terminal zinc finger DNA-binding domain. KLF6 is highly expressed in placenta, and it is required for proper placental development. We have demonstrated that KLF6 is necessary for cell fusion in human primary vCTBs, and in the BeWo cell line.

MATERIALS AND METHODS

Full length KLF6 or a mutant lacking its N-terminal domain were expressed in BeWo cells or in primary vCTB cells isolated from human term placentas. Cell fusion, gene and protein expression, and cell proliferation were analyzed. Moreover, Raman spectroscopy and atomic force microscopy (AFM) were used to identify biochemical, topography, and elasticity cellular modifications.

RESULTS

The increase in KLF6, but not the expression of its deleted mutant, is sufficient to trigger cell fusion and to raise the expression of β-hCG, syncytin-1, the chaperone protein 78 regulated by glucose (GRP78), the ATP Binding Cassette Subfamily G Member 2 (ABCG2), and Galectin-1 (Gal-1), all molecules involved in vCTB differentiation. Raman and AFM analysis revealed that KLF6 reduces NADH level and increases cell Young's modulus. KLF6-induced differentiation correlates with p21 upregulation and decreased cell proliferation. Remarkable, p21 silencing reduces cell fusion triggered by KLF6 and the KLF6 mutant impairs syncytialization and decreases syncytin-1 and β-hCG expression.

DISCUSSION

KLF6 induces syncytialization through a mechanism that involves its regulatory transcriptional domain in a p21-dependent manner.

lncRNA OR3A4 Promotes the Proliferation and Metastasis of Ovarian Cancer Through KLF6 Pathway

Aim: Ovarian cancer is a collaborative malignant tumor of the female reproductive system in clinical research. Some clinical studies have shown that OR3A4, which is a cancer-causing lncRNA, plays a major role in promoting the occurrence and development of a variety of tumors. And we also expressed the view that it expressed in ovarian tissue. However, the function of OR3A4 in ovarian cancer remains unclear. Methods and Results: To further verify the function of lncRNA OR3A4 in ovarian cancer, we established the xenograft model in the zebra fish. In this study, cells transformed with OR3A4 shRNA plasmids were transplanted into the zebra fish, and the cell proliferation and migration ability were significantly reduced compared to the empty vector. While knocking out OR3A4, we further downregulated its expression by siRNA of KLF6. Our study found that the knocked out OR3A4 resulted in a decrease in cell proliferation and migration level, which can be found in the downregulated expression of KLF6. We also verify the relationship between OR3A4 and circulating tumor cells in the zebra fish xenograft model, the results indicate that lncRNA OR3A4 may be involved in the resistance of ovarian cancer to complain. Conclusion: lncRNA OR3A4 promotes the proliferation and metastasis of ovarian cancer through the KLF6 pathway.

miR-152 Regulates Bovine Myoblast Proliferation by Targeting KLF6

Though miRNAs have been reported to regulate bovine myoblast proliferation, but many miRNAs still need to be further explored. Specifically, miR-152 is a highly expressed miRNA in cattle skeletal muscle tissues, but its function in skeletal muscle development is unknown. Herein, we aimed to investigate the role of miR-152 in regulating bovine myoblast proliferation. Functionally, RT-qPCR, Western blotting, EdU assay, and flow cytometry detection results showed that miR-152 inhibited bovine myoblast proliferation. Mechanistically, we demonstrated transcription factor KLF6 was a target gene of miR-152 by means of bioinformatics software prediction and dual-luciferase report analysis, which had been demonstrated to be favorable for myoblast proliferation. Collectively, our research suggested that miR-152 inhibits bovine myoblast proliferation via targeting KLF6.

Long noncoding RNA ZBED3-AS1 restrains breast cancer progression by targeting the microRNA-513a-5p/KLF6 axis

Breast cancer (BC) is the most commonly occurring malignancy in women. This study aimed to investigate the functions of the long noncoding RNA ZBED3‐AS1 (ZBED3‐AS1) in BC and its molecular mechanisms. qRT‐PCR was conducted to access the expression of ZBED3‐AS1, microRNA‐513a‐5p (miR‐513a‐5p), and Kruppel like factor 6 (KLF6) in BC. Additionally, BC cell viability and proliferative capacity were measured by MTT and 5‐Ethynyl‐20‐deoxyuridine (EdU) assays. A transwell assay was used for evaluating BC cell migration and invasion. The interactions among ZBED3‐AS1, miR‐513a‐5p, and KLF6 in BC were confirmed by dual‐luciferase reporter assay. Furthermore, feedback approaches were performed to determine whether ZBED3‐AS1 influences BC cell behaviors by regulating the miR‐513a‐5p/KLF6 axis. The murine xenograft model was established to assess the effect of ZBED3‐AS1 on tumor growth. The expression of ZBED3‐AS1 and KLF6 was reduced, while miR‐513a‐5p expression was elevated in BC. ZBED3‐AS1 elevation attenuated the malignant behaviors of BC cells, including viability, proliferative capacity, migration, and invasion. Mechanical experiments revealed that ZBED3‐AS1 targeted miR‐513a‐5p, and miR‐513a‐5p targeted KLF6 in BC. Feedback approaches validated that miR‐513a‐5p overexpression or KLF6 depletion reversed the inhibitory effects of ZBED3‐AS1 upregulation on viability, proliferative capacity, migration, and invasion of BC cells. Furthermore, ZBED3‐AS1 elevation attenuated the tumor growth in the murine xenograft model. ZBED3‐AS1 hindered the malignant development of BC cells by regulating the miR‐513a‐5p/KLF6 axis, providing a novel therapeutic target in BC.

Silencing lncRNA HOTAIR improves the recovery of neurological function in ischemic stroke via the miR-148a-3p/KLF6 axis

Ischemic stroke (IS), caused by a permanent or transient local reduction in blood supply to the brain, is one of the most widespread causes of public health problems in modern society. Long non-coding RNA (LncRNA) has been reported to be related to angiogenesis following IS. In this study, we explored the effect and potential molecular mechanism of lncRNA homeobox antisense non-coding RNA (HOTAIR) in IS. Permanent middle cerebral artery occlusion (pMCAO) model and oxygen and glucose deprivation (OGD) model were established. HOTAIR was increased in vivo and in vitro models post-ischemic. HOTAIR knockdown promoted neurological function recovery, manifesting in decreased modified neurological severity score, cerebral infarcted area, apoptosis and inflammation, and improved balance ability, spatial learning and memory ability. Silencing HOTAIR also improved the viability of OGD-induced N2a cells, and attenuated apoptosis and inflammation. HOTAIR can compete with KLF6 to bind to miR-148a-3p. miR-148a-3p knockdown or KLF6 overexpression partially reversed the effect of sh-HOTAIR on OGD-induced N2a cells. HOTAIR suppressed the activation of STAT3 pathway via the miR-148a-3p/KLF6 axis. To summarize, this study demonstrated that lncRNA HOTAIR absorbed miR-148a-3p and up-regulated KLF6 expression through ceRNA mechanism, and inhibited STAT3 pathway, promoted apoptosis and inflammation, and aggravated neurological injury post-IS.

Tumor-Derived Extracellular Vesicles Promote Activation of Carcinoma-Associated Fibroblasts and Facilitate Invasion and Metastasis of Ovarian Cancer by Carrying miR-630

Ovarian cancer (OC) is a lethal gynecological malignancy. Extracellular vesicles (EVs) are crucial media in cell-to-cell communication by carrying microRNAs (miRs). The current study aims to investigate the underlying mechanism of miR-630 carried by OC cell-derived EVs in regard to invasion and metastasis of OC cells. miRs related to OC metastasis were searched and screened. The expression patterns of screened miRs in human normal fibroblasts (NFs) and carcinoma-associated fibroblasts (CAFs) were detected using RT-qPCR. miR-630 related to OC metastasis and CAFs activation was analyzed further. The levels of FAP and α-SMA were detected using Western blotting and immunofluorescence. The migration of NFs was measured using Transwell assay. OC cell-derived EVs were isolated and identified. Uptake of EVs by NFs was observed using immunofluorescence staining. The culture supernatant of NFs was collected and used to culture the low metastasis cell line OVCAR8. The migration and invasion of OC cells and epithelial mesenchymal transition (EMT) were measured. Moreover, a xenograft model was established by injecting OVCAR8 cells of different groups into nude mice. Lastly, the effect of EV-pretreated NFs on invasion and metastasis of OC cells was observed in vivo. miR-630 was upregulated in OC cells and CAFs, and further associated with CAF activation and OC metastasis. miR-630 overexpression increased the levels of FAP and α-SMA in NFs, resulting in the transformation of NFs into CAFs. EVs carried miR-630 into NFs and EVs promoted CAF activation. miR-630 targeted KLF6. miR-630 inhibition or KLF6 overexpression attenuated EVs-induced CAF activation. EVs activated the NF-κB pathway via the miR-630/KLF6 axis. The conditioned medium of NFs pretreated with EVs promoted the invasion and metastasis of OVCAR8 cells, while downregulating miR-630 in EVs partially inhibited the promotive effect of NFs. EV-pretreated NFs promoted invasion and metastasis of OC in vivo. In conclusion, EVs carried miR-630 into NFs, thereby facilitating CAF activation and promoting invasion and metastasis of OC by inhibiting KLF6 and activating the NF-κB pathway. Our findings might offer a novel mechanism of invasion and metastasis of OC from the perspective of tumor microenvironment.

CircMTO1 Attenuated Acute Kidney Injury Through Regulating miR-337

Acute kidney injury (AKI) is an independent risk factor for the increased risk of death in patients with sepsis. In the current study, we first investigated the expression of circMTO1 in sepsis-induced AKI, and the underlying mechanism was further elucidated. The results showed that circMTO1 expression level was significantly decreased in serums and kidney tissues of US rats and RMCs treated with LPS. Besides, circMTO1 overexpression promoted cell viability, suppressed cell apoptosis and cytokines production of LPS-treated RMCs. Bioinformatics analysis showed that circMTO1 served as a sponge for miR-337. Furthermore, circMTO1 could inhibit the expression of KLF6. Altogether, our study first reported that circMTO1 expression was decreased in sepsis-induced AKI rat models and RMCs treated with LPS. CircMTO1 overexpression could attenuate AKI development by sponging miR-337 and regulating KLF6 expression, which may provide new ideas for evaluation the pathogenesis and the treatment of sepsis-induced AKI.

Predictive value of transcriptional expression of Krüppel-like factor-6 (KLF6) in head and neck carcinoma patients treated with radiotherapy

PURPOSE

To analyse the relationship between the transcriptional expression of Krüppel-like factor-6 (KLF6) and local response to treatment with radiotherapy in patients with head and neck squamous cell carcinoma (HNSCC).

METHODS

We determined the transcriptional expression of KLF6 in tumour biopsies obtained before treatment with radiotherapy in 83 HNSCC patients. The KLF6 expression was categorized according to the local control of the disease with a recursive partitioning analysis.

RESULTS

During the follow-up period, 27 patients (32.5%) had a local recurrence of the tumour. Patients with local recurrence had significantly higher levels of KLF6 expression than patients in which radiotherapy achieved local control of the disease (P = 0.029). Five-year local recurrence-free survival for patients with a high transcriptional expression of KLF6 (n = 46) was 51.1% (95% CI 36.4-66.2%), and for patients with low expression it was 85.6% (95% CI 73.9-97.3%) (P = 0.0001). The results of a multivariate analysis showed that patients with a high KLF6 expression had a 3.8 times higher risk of local recurrence after treatment with radiotherapy (95% CI 1.4-10.5, P = 0.008).

CONCLUSION

Transcriptional expression of KLF6 was significantly related to local control in HNSCC patients treated with radiotherapy. Patients with high levels of KLF6 expression had a significantly higher risk of local recurrence after treatment.

PVT1 knockdown inhibited the biological behavior of LPS-induced cardiac fibroblasts by regulating miR-24

BACKGROUND

The heart is one of the target organs vulnerable to sepsis. About 50% of sepsis patients will suffer from myocardial injury and cardiac dysfunction, which will aggravate the sepsis and affect its prognosis.

OBJECTIVES

Here, we attempt to investigate the function of long non coding RNA PVT1 in LPS-induced cardiac fibroblasts in vitro, and explore its potential mechanism.

METHODS

The expression of PVT1 in LPS-induced cardiac fibroblasts was detected by qRT-PCR. CCK-8 assay, cell migration, qRT-PCR and western blotting analysis were applied to evaluating the effect of PVT1 knockdown on LPS-induced cardiac fibroblasts. The bioinformatics analysis and the rescue experiment were devoted to the underlying mechanism.

RESULTS

PVT1 expression was up-regulated in LPS-induced cardiac fibroblasts. And knockdown of PVT1 inhibited cell viability and migration, alleviated inflammation cytokines production of LPS-treated cardiac fibroblasts. The bioinformatics analysis predicted PVT1 negatively regulates miR-24 and KLF6 is a direct target of miR-24.

CONCLUSIONS

In a word, we observed PVT1 expression level was up-regulated in LPS- treated cardiac fibroblasts. PVT1 knockdown could alleviate LPS-induced biological behavior of cardiac fibroblasts through sponging miR-24 in vitro.

The protective effects of azilsartan against oscillatory shear stress-induced endothelial dysfunction and inflammation are mediated by KLF6

BACKGROUND AND PURPOSE

Atherosclerosis is a common cardiovascular disease with high morbidity and mortality. It is reported to be related to oscillatory shear stress (OSS)-induced endothelial dysfunction and excessive production of inflammatory factors. Azilsartan, a specific antagonist of the angiotensin II receptor, has been approved for the management of hypertensive subjects with diabetes mellitus type II (DMII). The present study will investigate the effects of azilsartan against OSS-induced endothelial dysfunction and inflammation, as well as the underlying mechanism.

MATERIALS AND METHODS

Cell viability was detected using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay were used to determine the expression levels of IL-6, TNF-α, IL-1β, VCAM-1, and ICAM-1 in human aortic endothelial cells (HAECs). Generation of reactive oxygen species (ROS) was measured using 2'-7'dichlorofluorescin diacetate (DCFH-DA) staining, and the level of reduced glutathione (GSH) was evaluated using a commercial kit. The adhesion of THP-1 monocytes to HAECs was evaluated using calcein-AM staining. The expression level of KLF6 was determined using qRT-PCR and Western blot analysis.

RESULTS

According to the result of the MTT assay, 5 and 10 μM azilsartan were considered as the optimized concentrations applied in the present study. The elevated production of IL-6, TNF-α, and IL-1β, increased levels of ROS, decreased levels of reduced GSH, upregulated VCAM-1, ICAM-1, and E-selectin, and the aggravated adhesion of THP-1 cells to HAECs induced by OSS were all reversed by the introduction of azilsartan. The downregulation of KLF6 induced by OSS was significantly reversed by azilsartan. By knocking down the expression of KLF6, the suppressed adhesion of THP-1 cells to the HAECs, and the downregulation of VCAM-1 and ICAM-1 induced by azilsartan in OSS-stimulated HAECs were greatly reversed.

CONCLUSION

The protective effects of azilsartan against OSS-induced endothelial dysfunction and inflammation might be mediated by KLF6.

Quaking 5 suppresses TGF-β-induced EMT and cell invasion in lung adenocarcinoma

Quaking (QKI) proteins belong to the signal transduction and activation of RNA (STAR) family of RNA-binding proteins that have multiple functions in RNA biology. Here, we show that QKI-5 is dramatically decreased in metastatic lung adenocarcinoma (LUAD). QKI-5 overexpression inhibits TGF-β-induced epithelial-mesenchymal transition (EMT) and invasion, whereas QKI-5 knockdown has the opposite effect. QKI-5 overexpression and silencing suppresses and promotes TGF-β-stimulated metastasis in vivo, respectively. QKI-5 inhibits TGF-β-induced EMT and invasion in a TGFβR1-dependent manner. KLF6 knockdown increases TGFβR1 expression and promotes TGF-β-induced EMT, which is partly abrogated by QKI-5 overexpression. Mechanistically, QKI-5 directly interacts with the TGFβR1 3' UTR and causes post-transcriptional degradation of TGFβR1 mRNA, thereby inhibiting TGF-β-induced SMAD3 phosphorylation and TGF-β/SMAD signaling. QKI-5 is positively regulated by KLF6 at the transcriptional level. In LUAD tissues, KLF6 is lowly expressed and positively correlated with QKI-5 expression, while TGFβR1 expression is up-regulated and inversely correlated with QKI-5 expression. We reveal a novel mechanism by which KLF6 transcriptionally regulates QKI-5 and suggest that targeting the KLF6/QKI-5/TGFβR1 axis is a promising targeting strategy for metastatic LUAD.

Krüppel-Like Factor 6 Splice Variant 1: An Oncogenic Transcription Factor Involved in the Progression of Multiple Malignant Tumors

Krüppel-like factor 6 (KLF6) is one of the most studied members of the specificity protein/Krüppel-like factor (SP/KLF) transcription factor family. It has a typical zinc finger structure and plays a pivotal role in regulating the biological processes of cells. Recently, it has been considered to play a role in combatting cancer. Krüppel-like factor 6 splice variant 1 (KLF6-SV1), being one of the alternative KLF6 splicing isoforms, participates in tumor occurrence and development and has the potential to become a new target for molecular targeted therapy, although its action mechanism remains to be determined. The purpose of this article is to provide a comprehensive and systematic review of the important role of KLF6-SV1 in human malignant tumors to provide novel insights for oncotherapy.

Krüppel-like factor 6 promotes odontoblastic differentiation through regulating the expression of dentine sialophosphoprotein and dentine matrix protein 1 genes

AIM

To investigate the potential role of Krüppel-like factor 6 (KLF6) in the odontoblastic differentiation of immortalized dental papilla mesenchymal cells (iMDP-3) cells.

METHODOLOGY

Alizarin Red S (ARS) and Alkaline phosphatase (ALP) staining was used to examine the mineralization effect of iMDP-3 cells after odontoblastic induction. Real-time PCR and Western blotting were employed to analyse dentine sialophosphoprotein (DSPP), dentine matrix protein 1 (DMP1), RUNX family transcription factor 2 (RUNX2), ALP and KLF6 expression during this process. Co-expression of the KLF6 with DMP1, DSPP and RUNX2 was detected by double immunofluorescence staining to explore their local relationship in the cell. To further investigate KLF6 functions, Klf6 gain- and loss-of-function assays followed by ARS and ALP stainings, real-time PCR and Western blotting were performed using Klf6-overexpression plasmids and Klf6 siRNA to investigate whether changes in Klf6 expression affect the odontoblastic differentiation of iMDP-3 cells. Dual-luciferase reporter assays were used to elucidate the mechanistic regulation of Dspp and Dmp1 expression by Klf6. Means were compared using the unpaired t-test and Kruskal-Wallis one-way anova with P < 0.05 and P < 0.01 defined as statistical significance levels.

RESULTS

The expression levels of Klf6 (P < 0.01), Dspp (P < 0.05), Dmp1 (P < 0.01), Runx2 (P < 0.01) and Alp (P < 0.01) were significantly elevated during odontoblastic differentiation of iMDP-3 cells. KLF6 was co-localized with DSPP, DMP1 and RUNX2 in the cytoplasm and nucleus of iMDP-3 cells. Overexpression of Klf6 promoted the odontoblastic differentiation of iMDP-3, whereas the inhibition of Klf6 prevented this procession. Dual-luciferase assays revealed that Klf6 upregulates Dspp and Dmp1 transcription in iMDP-3 cells during odontoblastic differentiation.

CONCLUSION

Klf6 promoted odontoblastic differentiation by targeting the transcription promoter of Dmp1 and Dspp. This study may offer novel insights into strategies for treating injuries to dental pulp tissue.

Clinical and prognostic significance of Krüppel-like transcription factor 6 expression in 67 patients with cutaneous malignant melanoma in China

Krüppel-like transcription factor 6 (KLF6) is a ubiquitous tumor suppressor gene involved in regulating cell growth, proliferation, differentiation and angiogenesis. The objective of the study was to investigate the clinical and prognostic significance of KLF6 expression in cutaneous malignant melanoma (CMM) patients. A total of CMM 67 patients were enrolled in this study. The specimens were evaluated by immunohistochemistry to detect KLF6. The positive KLF6 expression in CMM tissues was significantly lower than in normal skin tissues (p < 0.01).The presence of KLF6 in CMM was correlated with ulceration (p < 0.01), lymph node metastasis (p < 0.01) and clinical stage (p < 0.01). The overall 5-year survival rate of the 67 patients was 13.4%. The 5-year survival rate of patients with negative KLF6 expression was correlated with KLF6 expression (p < 0.01), ulceration (p < 0.01), lymph node metastasis (p < 0.01), clinical stage (p < 0.01) and operation type (p < 0.01). Ulceration and clinical staging were independent relevant factors. In conclusion, the presence of KLF6 in CMM was correlated with ulceration, lymph node metastasis, clinical stage and poor prognosis.

MicroRNA-2355-5p regulates γ-globin expression in human erythroid cells by inhibiting KLF6

Krüppel-like factors (KLFs) are a highly conserved family of transcription factors. We analysed expression profile data of KLFs and identified KLF6 as a new potential regulator of erythropoiesis. Knocking down the expression of KLF6 significantly raised γ-globin mRNA and protein levels in the erythroid cell line HUDEP-2 and haematopoietic progenitor (CD34⁺ ) cells. We found that overexpression of microRNA (miR)-2355-5p in HUDEP-2 and CD34⁺ cells correlated with increased γ-globin synthesis by suppressing expression of KLF6. Our discovery that the interaction between miR-2355-5p and KLF6 affects the expression of γ-globin may provide more information for the clinical management of β-thalassaemia patients.

MiR-543 regulates myoblast proliferation and differentiation of C2C12 cells by targeting KLF6

MicroRNA-543 (miR-543) has been found to play a suppressive role in various human cancers in many studies, whereas the specific functions of miR-543 in muscle development remain poorly understood. Here, we found that the expression of miR-543 was high in skeletal muscle and increased during the differentiation of C2C12 cells. Overexpression of miR-543 repressed C2C12 cell proliferation and promoted differentiation, while knockdown of miR-543 expression produced the opposite results. During myogenesis, we predicted and verified that Krüppel-like factor 6 (KLF6), a suppressor of multiple tumor cells, was a target gene of miR-543. Then, miR-543 was found to specifically target KLF6 and repress its expression. Besides this, knockdown of KLF6 promoted the differentiation but inhibited the proliferation of C2C12 cells. Si-KLF6 can rescue the influence of miR-543 inhibitor on C2C12 cell differentiation. Our results indicate a new regulatory mechanism of miR-543 on KLF6 expression and suggest the possibility of using the miR-543/KLF6 pathway as a potential target for studying myogenesis.

A Single-Cell Transcriptomic Atlas of Human Skin Aging

Skin undergoes constant self-renewal, and its functional decline is a visible consequence of aging. Understanding human skin aging requires in-depth knowledge of the molecular and functional properties of various skin cell types. We performed single-cell RNA sequencing of human eyelid skin from healthy individuals across different ages and identified eleven canonical cell types, as well as six subpopulations of basal cells. Further analysis revealed progressive accumulation of photoaging-related changes and increased chronic inflammation with age. Transcriptional factors involved in the developmental process underwent early-onset decline during aging. Furthermore, inhibition of key transcription factors HES1 in fibroblasts and KLF6 in keratinocytes not only compromised cell proliferation, but also increased inflammation and cellular senescence during aging. Lastly, we found that genetic activation of HES1 or pharmacological treatment with quercetin alleviated cellular senescence of dermal fibroblasts. These findings provide a single-cell molecular framework of human skin aging, providing a rich resource for developing therapeutic strategies against aging-related skin disorders.

Apremilast ameliorates ox-LDL-induced endothelial dysfunction mediated by KLF6

Apremilast is a phosphodiesterase 4 (PDE4) inhibitor used in the treatment of psoriasis and several other inflammatory diseases. Interest has been expressed in seeking out therapies that address both psoriasis and atherosclerosis. In the present study, we explored the effects of apremilast in human aortic endothelial cells (HAECs) exposed to oxidized low-density lipoprotein (ox-LDL) to simulate the atherosclerotic microenvironment in vitro. Our findings indicate that apremilast may reduce the expression of lectin-like oxidized-low-density-lipoprotein receptor-1 (LOX-1), the main ox-LDL scavenging receptor. Apremilast also inhibited the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8), which are deeply involved in the chronic inflammatory response associated with atherosclerosis. Interestingly, we found that apremilast inhibited the attachment of U937 monocytes to HAECs by reducing the expression of the chemokine monocyte chemotactic protein 1 (MCP-1) and the cellular adhesion molecule vascular cell adhesion molecule-1 (VCAM-1). This effect was found to be mediated through the rescue of Krüppel like factor 6 (KLF6) expression, which was reduced in response to ox-LDL via increased phosphorylation of c-Jun N-terminal kinase (JNK). These findings suggest a potential role for apremilast in the treatment of atherosclerosis.

LncRNA LUCAT1/miR-181a-5p axis promotes proliferation and invasion of breast cancer via targeting KLF6 and KLF15

BACKGROUND

Long non-coding RNAs (lncRNAs) are novel regulatory molecules in breast cancer development. LncRNA LUCAT1 is a potential tumor promoter in human cancers. In this study, we aimed to explore the role of LUCAT1 in human breast cancer tissues and cells.

METHODS

A total of 31 breast cancer patients who underwent tumor resection, but without chemo- or radiotherapy or acute lung/heart/kidney diseases, provided tumor and adjacent normal tissues. Bioinformatic analysis, qRT-PCR, and luciferase reporter assay were carried out during the study.

RESULTS

qRT-PCR analysis indicated that, compared with the adjacent tissues and MCF-10A normal breast epithelial cells, LUCAT1 was markedly up-regulated in the breast cancer tissues and five BC cell lines, including MDA-MB-231, MDA-MB-468, MDA-MB-435, SKBR3, and MCF-7. The knockdown of LUCAT1, through the transfection of small interfering RNA (siRNA) specific to LUCAT1, resulted in inhibition of proliferation in breast cancer cells. The expression levels of miR-181a-5p were decreased in the breast cancer tissues and five BC cell lines. Bioinformatic analysis and luciferase reporter assay suggested the interaction between miR-181a-5p and LUCAT1. In addition, the effects of LUCAT1 on promoting cell proliferation were attenuated by overexpression of miR-181a-5p through the transfection of miR-181a-5p mimic. Moreover, bioinformatics and luciferase reporter assay confirmed that miR-181a-5p targeted the 3'-UTR region of KLF6 and KLF15 mRNA, which were two tumor suppressor genes. LUCAT1/miR-181a-5p axis regulated the expression of KLF6 and KLF15 both in vitro and in vivo.

CONCLUSIONS

Our data indicate that LUCAT1/miR-181a-5p axis can serve as a novel therapeutic target in breast cancer.

Upregulated miRNA-543 promotes the proliferation and migration of gastric carcinoma by downregulating KLF6

This study aims to uncover the potential function of MicroRNA-543 (miRNA-543) in the pathogenesis of gastric carcinoma and the possible mechanism. MiRNA-543 levels in gastric carcinoma tissues and cell lines were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Regulatory effects of miRNA-543 on proliferative and migratory abilities of AGS and MKN45 cells were assessed. The downstream target of miRNA-543 was predicted by online bioinformatics and verified by dual-luciferase reporter gene assay. At last, rescue experiments were carried out to uncover the interaction between miRNA-543 and Krüppel-like factor 6 (KLF6) in the progression of gastric carcinoma. MiRNA-543 was upregulated in gastric carcinoma tissues and cell lines. Particularly, gastric carcinoma patients with advanced stage or positive metastasis expressed higher abundance of miRNA-543. Overexpression of miRNA-543 promoted proliferative ability in gastric carcinoma, manifesting as increased viability, EdU-positive ratio and migratory cell number in AGS and MKN45 cells. KLF6 was proved to be the downstream target of miRNA-543. Both mRNA and protein levels of KLF6 were negatively regulated by miRNA-543 in gastric carcinoma cells. Silence of KLF6 was able to reverse the regulatory effects of miRNA-543 inhibitor on proliferative and migratory abilities in gastric carcinoma. MiRNA-543 is highly expressed in gastric carcinoma. It accelerates gastric carcinoma cells to proliferate and migrate by negatively regulating KLF6 level.

Hepatocyte KLF6 expression affects FXR signalling and the clinical course of primary sclerosing cholangitis

BACKGROUND & AIMS

Primary sclerosing cholangitis (PSC) is characterized by chronic cholestasis and inflammation, which promotes cirrhosis and an increased risk of cholangiocellular carcinoma (CCA). The transcription factor Krueppel-like-factor-6 (KLF6) is a mediator of liver regeneration, steatosis, and hepatocellular carcinoma (HCC), but no data are yet available on its potential role in cholestasis. Here, we aimed to identify the impact of hepatic KLF6 expression on cholestatic liver injury and PSC and identify potential effects on farnesoid-X-receptor (FXR) signalling.

METHODS

Hepatocellular KLF6 expression was quantified by immunohistochemistry (IHC) in liver biopsies of PSC patients and correlated with serum parameters and clinical outcome. Liver injury was analysed in hepatocyte-specific Klf6-knockout mice following bile duct ligation (BDL). Chromatin-immunoprecipitation-assays (ChIP) and KLF6-overexpressing HepG2 cells were used to analyse the interaction of KLF6 and FXR target genes such as NR0B2.

RESULTS

Based on IHC, PSC patients could be subdivided into two groups showing either low (<80%) or high (>80%) hepatocellular KLF6 expression. In patients with high KLF6 expression, we observed a superior survival in Kaplan-Meier analysis. Klf6-knockout mice showed reduced hepatic necrosis following BDL when compared to controls. KLF6 suppressed NR0B2 expression in HepG2 cells mediated through binding of KLF6 to the NR0B2 promoter region.

CONCLUSION

Here, we show an association between KLF6 expression and the clinical course and overall survival in PSC patients. Mechanistically, we identified a direct interaction of KLF6 with the FXR target gene NR0B2.

lncRNA MIR4435-2HG promoted clear cell renal cell carcinoma malignant progression via miR-513a-5p/KLF6 axis

Long non‐coding RNAs (lncRNAs) take various biological effects in clear cell renal cell carcinoma (ccRCC) mostly through sponging with microRNAs (miRNAs). lncRNA MIR4435‐2HG is found to promote tumour progression in gastric cancer, glioblastoma and hepatocellular carcinoma. However, the role of lncRNA MIR4435‐2HG in ccRCC progression remains unknown. The purpose of this research was to investigate the potential molecular mechanism of lncRNA MIR4435‐2HG regarding the regulation of ccRCC initiation and progression. In this study, we found the up‐regulation of MIR4435‐2HG in ccRCC tissues and cell lines. Functionally, overexpression of MIR4435‐2HG promoted the proliferation as well as the metastasis in ccRCC cell lines, whereas knockdown of MIR4435‐2HG inhibited the above changes. Then, bioinformatic analysis and luciferase reporter assays confirmed the negative regulation effect of MIR4435‐2HG on miR‐513a‐5p. And further investigations showed that KLF6, which collected from the intersection of databases, was the potential conjugated mRNAs of miR‐513a‐5p. Finally, the rescue experiments revealed the relation among MIR4435‐2HG and KLF6, which showed that KLF6 could reverse the promoting effect of MIR4435‐2HG on ccRCC in vitro and in vivo. Therefore, our findings provided insight into the mechanisms of MIR4435‐2HG in ccRCC and revealed an alternative target for the clinical diagnosis and treatment of ccRCC.

mir-22-3p/KLF6/MMP14 axis in fibro-adipogenic progenitors regulates fatty infiltration in muscle degeneration

Fibro/adipogenic progenitors (FAPs) are the main cellular source of fatty degeneration in muscle injury; however, the underlying mechanism of FAP adipogenesis in muscle degeneration needs to be further examined. Matrix metalloproteinase 14 (MMP-14) has been reported to induce the adipogenesis of 3T3-L1 preadipocytes, but whether MMP-14 also regulates the differentiation of FAPs remains unclear. To investigate whether and how MMP-14 regulates FAP adipogenesis and fatty infiltration in muscle degeneration, we examined MMP-14 expression in degenerative muscles and tested the effect of MMP-14 on FAP adipogenesis in vitro and in vivo. As expected, MMP-14 enhanced FAP adipogenesis and fatty infiltration in degenerative muscles; moreover, blocking endogenous MMP-14 in injured muscles facilitated muscle repair. Further investigations revealed that Kruppel-like factor 6 (KLF6) was a transcription factor associated with MMP-14 and acted as an "on-off" switch in the differentiation of FAPs into adipocytes or myofibroblasts. Moreover, KLF6 was the target gene of miR-22-3p, which was downregulated during FAP adipogenesis both in vitro and in vivo, and overexpression of miR-22-3p markedly prevented FAP adipogenesis and attenuated fatty degeneration in muscles. Our study revealed that miR-22-3p/KLF6/MMP-14 is a novel pathway in FAP adipogenesis and that inhibiting KLF6 is a potential strategy for the treatment of muscular degenerative diseases.

Paeonol Inhibits Cell Proliferation, Migration and Invasion and Induces Apoptosis in Hepatocellular Carcinoma by Regulating miR-21-5p/KLF6 Axis

Background

Hepatocellular carcinoma (HCC) is one of the most common tumors with high mortality. MicroRNAs (miRNAs) were reported as crucial markers for the diagnosis of HCC. Paeonol exerted many pharmacological effects on tumor progression. This study aimed to elucidate the underlying molecular mechanism of paeonol in HCC progression.

Methods

Cell viability was determined by Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was examined by flow cytometry. The levels of Cyclin D1, cyclin-dependent kinase 4 (CDK4), B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) were detected by Western blot assay. Cell migration and invasion were assessed by transwell assay. The levels of matrix metalloproteinase-2 (MMP2) and matrix metalloproteinase-9 (MMP9) were measured by Western blot. The expression of miR-21-5p and kruppel-like factor 6 (KLF6) was detected by quantitative real-time PCR (qRT-PCR) or Western blot assay, respectively. Dual-luciferase reporter assay was performed to analyze the interaction between miR-21-5p and KLF6. The enrichment of miR-21-5p was determined by RNA pull-down assay. Xenograft assay was conducted to analyze tumor growth in vivo.

Results

The results demonstrated that cell viability of Hep3B and Huh-7 cells was inhibited, while cell apoptosis was promoted after treatment with paeonol. Transwell assay indicated that cell migration and invasion were blocked in paeonol-treated cells. Moreover, miR-21-5p expression was markedly decreased in paeonol-treated cells and its knockdown suppressed cell viability, migration and invasion, but contributed to cell apoptosis. MiR-21-5p targeted KLF6 and its silencing prominently elevated KLF6 level. Furthermore, the restoration experiment determined that miR-21-5p and KLF6 were antagonisms on cell viability, apoptosis, migration and invasion. Also, paeonol abated the decrease in KLF6 level caused by miR-21-5p up-regulation. Besides, paeonol suppressed tumor growth in vivo.

Conclusion

Paeonol impeded cell viability, migration and invasion and triggered apoptosis by regulating miR-21-5p/KLF6 axis in HCC cells. Xenograft assay confirmed that paeonol inhibited tumor growth through miR-21-5p/KLF6 axis in HCC in vivo.

KLF6 Acetylation Promotes Sublytic C5b-9-Induced Production of MCP-1 and RANTES in Experimental Mesangial Proliferative Glomerulonephritis

Rat Thy-1 nephritis (Thy-1N) is an experimental mesangial proliferative glomerulonephritis (MsPGN) for studying human MsPGN. Although sublytic C5b-9 complex formation on glomerular mesangial cells (GMCs) and renal MCP-1 and RANTES production in rats with Thy-1N have been proved, the role and mechanism of MCP-1 or RANTES synthesis in GMCs induced by sublytic C5b-9 are poorly elucidated. In this study, we first found the expression of transcription factor (KLF6), co-activator (KAT7) and chemokines (MCP-1 and RANTES) was all up-regulated both in renal tissue of Thy-1N rats (in vivo) and in sublytic C5b-9-induced GMCs (in vitro). Further in vitro experiments revealed that KLF6 bound to MCP-1 promoter (-297 to -123 nt) and RANTES promoter (-343 to -191 nt), leading to MCP-1 and RANTES gene transcription. Meanwhile, KAT7 also bound to the same region of MCP-1 and RANTES promoter in a KLF6-dependent manner, and KLF6 was acetylated by KAT7 at lysine residue 100, which finally promoted MCP-1 and RANTES expression. Moreover, our in vivo experiments discovered that knockdown of renal KAT7 or KLF6 gene obviously reduced MCP-1 and RANTES production, GMCs proliferation, ECM accumulation, and proteinuria secretion in Thy-1N rats. Collectively, our study indicates that sublytic C5b-9-induced MCP-1 and RANTES synthesis is associated with KAT7-mediated KLF6 acetylation and elevated KLF6 transcriptional activity, which might provide a new insight into the pathogenesis of rat Thy-1N and human MsPGN.

MiR-4262 inhibits the development of esophageal cancer by negatively regulating KLF6 level

OBJECTIVE

To uncover the expression pattern and the prognosis of miR-4262 in these patients with esophageal cancer, and its potential mechanism.

METHODS

MiR-4262 levels in 57 esophageal cancer and paracancerous specimens were detected. The relationship between miR-4262 level and clinical features of esophageal cancer was analyzed. After overexpression of miR-4262 in OE19 and EC-109 cells, changes in proliferative potential and apoptosis were examined. The interaction between miR-4262 and KLF6 was explored by dual-luciferase reporter assay. Their involvement in the development of esophageal cancer was finally determined.

RESULTS

MiR-4262 was downregulated in esophageal cancer specimens and cell lines. Low level of miR-4262 predicted advanced pathological staging and poor prognosis in esophageal cancer patients. Overexpression of miR-4262 reduced proliferative potential and enhanced apoptosis in esophageal cancer cells. KLF6 was the downstream gene binding to miR-4262. The interaction between miR-4262 and KLF6 was responsible for alleviating the malignant development of esophageal cancer.

CONCLUSIONS

MiR-4262 is downregulated in esophageal cancer and linked to its pathological staging and prognosis. MiR-4262 inhibits the malignant development of esophageal cancer by down-regulating KLF6.

MiR-181d-5p Targets KLF6 to Improve Ischemia/Reperfusion-Induced AKI Through Effects on Renal Function, Apoptosis, and Inflammation

Renal tubular epithelial cell (RTEC) death and renal interstitial inflammation are the most crucial pathophysiological changes in acute kidney ischemia/reperfusion injury (IRI). The microRNA (miR)-181d family plays diverse roles in cell proliferation, apoptosis and inflammation, but its renal target and potential role in IRI are unknown. Here, we showed that the expression of miR-181d-5p decreased and Krueppel-like factor 6 (KLF6) increased in a renal cell (HK-2) model of hypoxia/reoxygenation (H/R) injury and a mouse model of renal IRI. They were mainly distributed in the renal tubules. After renal IRI, miR-181d-5p overexpression significantly inhibited inflammatory mediators, reduced apoptosis and further improved renal function. KLF6 exacerbated RTEC damage and acted as a NF-κB co-activator to aggravate the renal IRI inflammatory response. Mechanistically, KLF6 was predicted as a new potential target gene of miR-181d-5p through bioinformatic analysis and luciferase reporter assay verification. After overexpressing miR-181d-5p and inhibiting KLF6, the role of miR-181d-5p was weakened on the renal damage improvement. In conclusion, miR-181d-5p upregulation produced protective antiapoptotic and anti-inflammatory effects against IRI in kidneys in vivo and H/R injury in HK-2 cells in vitro, and these effects were achieved by targeted inhibition of KLF6. Thus, our results provide novel insights into the molecular mechanisms associated with IRI and a potential novel therapeutic target.

KLF6 Induces Apoptosis in Human Lens Epithelial Cells Through the ATF4-ATF3-CHOP Axis

Background

Many studies have confirmed that high myopia is related to the high prevalence of cataracts, which results from apoptosis of lens epithelial cells (LECs) due to endoplasmic reticulum stress. Krüppel-like factor 6 (KLF6) is a tumor suppressor that is involved in the regulation of cell proliferation and apoptosis.

Purpose

In this study, our purpose was to find the relationship between KLF6-induced apoptosis in LECs and ATF4 (activating transcription factor 4)-ATF3 (activating transcription factor 3)-CHOP (C/EBP homologous protein) signaling pathway.

Methods

KLF6, ATF4, ATF3, and CHOP were ectopically expressed using cDNAs subcloned into the pCDNA3.1+ vector. ATF4, ATF3, and CHOP knockdown were performed by small interfering RNA (siRNA). Expression of relative gene was tested using QT-PCR and western-blot. Then, accompanied by UVB stimulation, cell viability was measured by CCK-8 assay; The cell damage was examined by live & dead staining; The apoptotic markers Bax and Bcl-2 were detected by immunoblotting; Quantitative apoptotic levels were measured with the Apoptosis Detection Kit; The expression level of reactive oxygen-free radical (ROS) was analyzed by DCFH-DA` probe.

Results

Ectopically expressed ATF4, ATF3, and CHOP-induced apoptosis in cells, whereas ATF4, ATF3, and CHOP knockdown by small interfering RNA (siRNA) blocked KLF6-induced apoptosis. In addition, we determined that ATF4 regulates ATF3 and CHOP expression and that ATF3 silencing reduces CHOP upregulation without changing ATF4 levels; however, ATF4 and ATF3 expression was unaffected by blockade of CHOP, suggesting that KLF6 triggers endoplasmic reticulum stress in LECs by mediating the ATF4-ATF3/CHOP axis. Besides, KLF6 overexpression significantly induced LEC apoptosis under UV radiation, as demonstrated by the elevated Bax/Bcl-2 ratio.

Conclusion

The ATF4-ATF3-CHOP pathway plays an important role in KLF6-induced apoptosis in HLECs. Our results increase our understanding of the mechanisms that regulate LEC apoptosis and contribute to the development of a new preventative strategy for cataract.

CBX4 transcriptionally suppresses KLF6 via interaction with HDAC1 to exert oncogenic activities in clear cell renal cell carcinoma

Background

Dysregulation of polycomb chromobox (CBX) proteins that mediate epigenetic gene silencing contributes to the progression of human cancers. Yet their roles in clear cell renal cell carcinoma (ccRCC) remain to be explored.

Methods

The expression of CBX4 and its clinical significance were determined by qRT-PCR, western blot, immunohistochemistry and statistical analyses. The biological function of CBX4 in ccRCC tumor growth and metastasis and the underlying mechanism were investigated using in vitro and in vivo models.

Findings

CBX4 exerts oncogenic activities in ccRCC via interaction with HDAC1 to transcriptionally suppress tumor suppressor KLF6. CBX4 expression is increased in ccRCC and correlated with poor prognosis in two independent cohorts containing 840 patients. High CBX4 expression is significantly associated with Fuhrman grade and tumor lymph node invasion. CBX4 overexpression promotes tumor growth and metastasis, whereas CBX4 knockdown results in the opposite phenotypes. Mechanistically, CBX4 downregulates KLF6 via repressing the transcriptional activity of its promoter. Further studies show that CBX4 physically binds to HDAC1 to maintain its localization on the KLF6 promoter. Ectopic expression of KLF6 or disruption of CBX4-HDAC1 interaction attenuates CBX4-mediated cell growth and migration. Furthermore, CBX4 depletion markedly enhances the histone deacetylase inhibitor (HDACi)-induced cell apoptosis and suppression of tumor growth.

Interpretation

Our data suggest CBX4 as an oncogene with prognostic potential in ccRCC. The newly identified CBX4/HDAC1/KLF6 axis may represent a potential therapeutic target for the clinical intervention of ccRCC.

Kruppel-like factor 6 promotes macrophage inflammatory and hypoxia response

Macrophages are the professional phagocytes that protect the host from infection or injury. Tissue microenvironment at the site of injury and inflammation is characterized by low oxygen concentration and poor supply of nutrients. The responding macrophages have to advance against oxygen and nutrient gradients to reach the site of inflammation to perform host protection, and tissue repair functions. Thus, evolution has fashioned macrophages to orchestrate a coordinated inflammatory and hypoxic gene program to mount an effective immune response. Here, we discovered that Kruppel‐like factor 6 (KLF6) governs macrophage functions by promoting inflammatory and hypoxic response gene programming. Our in vivo studies revealed that myeloid‐KLF6‐deficient mice were highly resistant to endotoxin‐induced systemic inflammatory response syndrome symptomatology and mortality. Using complementary gain‐ and loss‐of‐function studies, we observed that KLF6 overexpression elevate and KLF6 deficiency attenuate inducible HIF1α expression in macrophages. Our integrated transcriptomics and gene set enrichment analysis studies uncovered that KLF6 deficiency attenuates broad inflammatory and glycolytic gene expression in macrophages. More importantly, overexpression of oxygen stable HIF1α reversed attenuated proinflammatory and glycolytic gene expression in KLF6‐deficient macrophages. Collectively, our studies uncovered that KLF6 govern inflammatory and hypoxic response by regulating HIF1α expression in macrophage.