Effect Of Krüppel-like Factor 4 Research Articles

Krüppel-like factor 4 promotes autophagy in macrophages under high glucose concentration by inhibiting the AKT/mTOR signaling pathway

Background: Diabetic atherosclerosis (AS) is the main cause of disability and death in diabetes. In the progression of AS, autophagic activity plays an important role. Krüppel-like factor 4 (KLF4) is a member of the zinc finger protein transcription factor family and is believed to play a protective role in the pathogenesis of atherosclerosis. This study aimed to explore the role of KLF4 in diabetic atherosclerosis and the autophagic mechanism. Methods: A diabetic mouse model was established and the expression level of KLF4 protein in the aorta of the mice was detected after a high-fat diet. The effects of KLF4 on cholesterol content, apoptosis, autophagy-related proteins, and the AKT/mTOR signaling pathway of THP-1 macrophages were also evaluated. Results: The expression level of KLF4 protein in the aorta of diabetic mice was decreased. Meanwhile, overexpression of KLF4 in THP-1 macrophages significantly decreased cholesterol accumulation, increased beclin-1 expression, decreased P62 expression, enhanced LC3 fluorescence intensity decreased cell apoptosis and p-mTOR and p-AKT expression were decreased under the condition of high glucose. After the reduction of KLF4 expression, the result is reversed. Conclusion: KLF4 induces autophagy by inhibiting the AKT/mTOR pathway and alleviates cholesterol deposition in THP-1 macrophages under high glucose concentration.

Endothelial Krüppel-Like Factor 4 Modulates Pulmonary Arterial Hypertension

Krüppel-like factor 4 (KLF4) is a transcription factor expressed in the vascular endothelium, where it promotes anti-inflammatory and anticoagulant states, and increases endothelial nitric oxide synthase expression. We examined the role of endothelial KLF4 in pulmonary arterial (PA) hypertension (PAH). Mice with endothelial KLF4 knockdown were exposed to hypoxia for 3 weeks, followed by measurement of right ventricular and PA pressures, pulmonary vascular muscularization, and right ventricular hypertrophy. The effect of KLF4 on target gene expression was assessed in lungs from these mice, verified in vitro by small interfering RNA (siRNA) knockdown of KLF4, and further studied at the promoter level with cotransfection experiments. KLF4 expression was measured in lung tissue from patients with PAH and normal control subjects. We found that, after hypoxia, right ventricular and PA pressures were significantly higher in KLF4 knockdown animals than controls. Knockdown animals also had more severe pulmonary vascular muscularization and right ventricular hypertrophy. KLF4 knockdown resulted in increased pulmonary expression of endothelin-1 and decreased expression of endothelial nitric oxide synthase, endothelin receptor subtype B, and prostacyclin synthase. Concordant findings were observed in vitro, both with siRNA knockdown of KLF4 and promoter activity assays. Finally, KLF4 expression was reduced in lungs from patients with PAH. In conclusion, endothelial KLF4 regulates the transcription of genes involved in key pathways implicated in PAH, and its loss exacerbates pulmonary hypertension in response to chronic hypoxia in mice. These results introduce a novel transcriptional modulator of PAH, with the potential of becoming a new therapeutic target.

Epigenetic alterations of Krüppel-like factor 4 and its tumor suppressor function in renal cell carcinoma

Krüppel-like factor 4 (KLF4) is a transcription factor that can have divergent functions in different malignancies. The expression and role of KLF4 in renal cell cancer remain unclear. The purpose of this study is to determine epigenetic alterations and possible roles of KLF4 in renal cell carcinoma. The KLF4 expression in primary renal cell cancer tissues and case-matched normal renal tissues was determined by protein and messenger RNA analyses. The epigenetic alterations were detected by methylation-specific PCR and Sequenom MassARRAY. Kaplan-Meier curves and the log-rank test were used for the survival analysis. The effects of KLF4 on cell growth and epithelial-to-mesenchymal transition (EMT) were determined in renal cancer cell lines after viral-based and RNA activation-mediated overexpression of KLF4. In vivo antitumor activity of KLF4 was evaluated by using stably KLF4-transfected renal cancer cells. KLF4 expression was dramatically decreased in various pathological types of renal cancer and associated with poor survival after nephrectomy. Hypermethylation of KLF4 promoter mainly contributed to its expression suppression. In vitro assays indicated that KLF4 overexpression inhibited renal cancer cell growth and survival. KLF4 overexpression also suppressed renal cancer cell migration and invasion by altering the EMT-related factors. In vivo assay showed that ectopic expression of KLF4 also inhibited tumorigenicity and metastasis of renal cancer. Our results suggest that KLF4 is a putative tumor suppressor gene epigenetically silenced in renal cell cancers by promoter CpG methylation and that it has prognostic value for renal cell progression.

Abstract LB-21: Regulation of Bmi1 by β-catenin and KLF4 and its implication in colon cancer

Abstract B lymphoma Mo-MLV insertion region 1 (Bmi1) is a Polycomb Group (PcG) protein that is important in gene silencing. It is a component of Polycomb Repressive Complex 1 (PRC1), which is required to maintain the transcriptionally repressive state of many genes. Bmi1 was initially identified as an oncogene that regulates cell proliferation and transformation, and is important in hematopoiesis and development of nervous systems. Recently, great attention is drawn upon the role of Bmi1 in stem cell regulation and cancer. It was reported that Bmi1 is a potential marker for the intestinal stem cells. Since Wnt signaling plays a key role in the intestinal stem cells, we analyzed the effects of Wnt signaling on Bmi1 expression in colon cancer cell lines. Krüppel-like factor 4 (KLF4) is a zinc finger protein that is highly expressed in the gut and skin. We recently found that KLF4 crosstalks with Wnt/[[Unsupported Character - Symbol Font ]]-catenin in regulating intestinal homeostasis. In addition, KLF4 is one of the four factors that induce pluripotent stem cells, thus playing a crucial role in stem cell regulation. In this study, the effects of KLF4 on Bmi1 expression were analyzed as well. These studies will provide novel insights into the mechanisms of Bmi1 function and regulation in the intestinal stem cells and colorectal cancers. Since Bmi1 is a stem cell or progenitor cell marker, we analyzed Bmi1 expression in human colorectal cancers tissues by IHC. Bmi1 levels are significantly increased in the tumor tissues from colon cancer patients compared with adjacent normal tissues; and expression of Bmi1 is significantly associated with nuclear [[Unsupported Character - Symbol Font ]]-catenin. Bmi1 knockdown by lentivirus-mediated Bmi1-shRNA repressed growth of different colon cancer cell lines, inhibited xenograft tumor growth, and increased differentiation of colon cancer cells in mouse xenograft. We found that dominant negative TCF (DnTCF), which blocks Wnt signaling, only marginally inhibits Bmi1 expression. However, both Western blot and RT-PCR results demonstrated that the expression of Bmi1 was inhibited by KLF4 in LS174T colon cancer cells. Using luciferase reporter assay, we found that repression of Bmi1 promoter by KLF4 is independent of c-myc. Using ChIP assay, we confirmed that KLF4 binds the endogenous Bmi1 promoter in colon cancer cells. Finally, we found that KLF4 inhibits Bmi1-mediated histone ubiquitination but by regulating more than one protein in the Polycomb complex. We found that Bmi1 is required for colon cancer cell proliferation and tumor growth, and it is up-regulated in colon cancer. Wnt signaling weakly regulates Bmi1; KLF4 inhibits Bmi1 by directly binding to Bmi1 promoter, thus inhibiting Bmi1-mediated H2A ubiquitination. It is of great interest to further study the mechanisms of Bmi1 regulation and the function of Bmi1 in normal intestine and in colon tumorigenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-21. doi:1538-7445.AM2012-LB-21

Kruppel-like factor 4 promotes differentiation of endothelial progenitor cells into endothelial cells by up-regulating endothelial nitric oxide synthase

ObjectiveThe differentiated function of Endothelial progenitor cells (EPCs) may play a pivotal roles in endothelial repair and reendothelialisation replacement of postinjury endothelium. However, the mechanism of differentiation of EPCs remains...

Putative Tumor-Suppressive Function of Krüppel-Like Factor 4 in Primary Lung Carcinoma

Krüppel-like factor 4 (KLF4) is a zinc-finger protein that plays important roles in stem cells and the development of gastric cancers. However, the role of KLF4 in primary lung cancer is unknown. The purpose of this study is to determine possible roles of KLF4 in lung cancer. The KLF4 expression in primary lung cancer tissues and case-matched normal lung tissues were determined by protein and mRNA analyses. The effects of KLF4 on cell proliferation, clonogenic formation, and cell cycle progression were determined in cultured lung cancer cells or bronchial epithelial cells after enforced KLF4 overexpression or small interfering RNA knockdown. The in vivo antitumor activity of KLF4 was evaluated by using stably transfected lung cancer cells and by adenovector-mediated gene delivery. The effect of KLF4 in regulating p21 and cyclin D1 was also evaluated. KLF4 protein and mRNA levels were dramatically decreased in most primary lung tumors compared with in case-matched normal lung tissues. Enforced expression of KLF4 resulted in marked inhibition of cell growth and clonogenic formation. The tumor-suppressive effect of KLF4 was associated with its role in up-regulating p21 and down-regulating cyclin D1, leading to cell cycle arrest at the G(1)-S checkpoint. Knockdown of KLF4 promoted cell growth in immortalized human bronchial epithelial cells. The enforced expression of KLF4 gene to lung cancer cells by ex vivo transfection or adenovector-mediated gene transfer suppressed tumor growth in vivo. Our results suggest that KLF4 plays an important role in suppressing the growth of lung carcinoma.

Upregulation of the constitutively expressed HSC70 by KLF4

Krüppel-like factor 4 (KLF4) is a transcription factor that is abundantly expressed in various organisms from bacteria to mammals. It has been demonstrated that KLF4 regulates the expression of a wide range of genes. Analysis of KLF4 target genes reveals its diverse regulatory functions in cell growth, proliferation, differentiation, embryogenesis, and inflammation. However, the regulation of the expression of inducible heat shock protein 70 (HSP72) and heat shock cognate 70 (HSP73) by KLF4 is not defined. In our previous study, a complementary deoxyribonucleic acid microarray assay showed that KLF4 overexpression led to dramatic upregulation of HSP73 messenger ribonucleic acid (mRNA) in murine C2C12 myoblast cells, suggesting that HSP73 is a potential target gene regulated by KLF4. The effect of KLF4 on the expression of HSP72 and HSP73 was further examined by reverse transcriptase polymerase chain reaction and Western blot in KLF4-overexpressing or KLF4-deficient cells. The results showed the upregulation of the HSP73 constitutive expression by KLF4 overexpression in both C2C12 cells and murine RAW264.7 macrophages; in response to heat stress, however, few changes were observed in the levels of HSP73 by KLF4 overexpression. In addition, knockdown of endogenous KLF4 expression by morpholino antisense oligonucleotides significantly decreased both HSP73 mRNA and protein levels under normal conditions. Conversely, KLF4 had no effect on the expression of HSP72. Taken together, these findings suggest an important role for KLF4 as a novel regulator of the constitutive expression of HSP73.