Up-regulation of Krüppel-like factor 5 in pancreatic cancer is promoted by interleukin-1beta signaling and hypoxia-inducible factor-1alpha

Modulation of Krüppel-like factors (KLFs) interaction with their binding partners in cancers through acetylation and phosphorylation

Post-translational modifications (PTMs) of transcription factors regulate transcriptional activity and play a key role in essentially all biological processes and generate indispensable insight towards biological function including activity state, subcellular localization, protein solubility, protein folding, substrate trafficking, and protein-protein interactions. Amino acids modified chemically via PTMs, function as molecular switches and affect the protein function and characterization and increase the proteome complexity. Krüppel-like transcription factors (KLFs) control essential cellular processes including proliferation, differentiation, migration, programmed cell death and various cancer-relevant processes. We investigated the interactions of KLF group-2 members with their binding partners to assess the role of acetylation and phosphorylation in KLFs on their binding affinity. It was observed that acetylation and phosphorylation at different positions in KLFs have a variable effect on binding with specific partners. KLF2-EP300, KLF4-SP1, KLF6-ATF3, KLF6-JUN, and KLF7-JUN show stabilization upon acetylation or phosphorylation at variable positions. On the other hand, KLF4-CBP, KLF4-EP300, KLF5-CBP, KLF5-WWP1, KLF6-SP1, and KLF7-ATF3 show stabilization or destabilization due to acetylation or phosphorylation at variable positions in KLFs. This provides a molecular explanation of the experimentally observed dual role of KLF group-2 members as a suppressor or activator of cancers in a PTM-dependent manner.

Regulome-wide association study identifies genetically driven accessible regions associated with pancreatic cancer risk

Genome-wide association studies (GWAS) have identified two dozen genetic variants that are associated with the risk of pancreatic ductal adenocarcinoma (PDAC), a deadly malignancy. However, a majority of these variants are located in noncoding regions of the genome, which limits the translation of GWAS findings into clinical applications. The regulome-wide association study (RWAS) is a recently developed method for identifying TF binding-induced accessibility regions for diseases. However, their potential connection to PDAC has yet to be fully explored. We evaluated the associations between genetically predicted levels of chromatin accessibility and risk of PDAC by using pan-cancer chromatin accessibility genetic prediction models. Our analysis included 8275 cases and 6723 controls from the PanScan (I, II, and III) and PanC4 consortia. To further refine our results, we also integrated genes associated to allele-specific accessibility quantitative trait loci (as-aQTL) and TF motifs located in the as-aQTL. We found that 50 chromatin accessibility features were associated with PDAC risk at a false discovery rate (FDR) of less than 0.05. A total of 28 RWAS peaks were identified as conditionally significant. By integrating the results from as-aQTL, motif analysis, and RWAS, we identified candidate causal regulatory elements for two potential chromatin accessibility regions (THCA_89956 and ESCA_89167) that are associated with PDAC risk. Our study identified chromatin accessibility features in noncoding genomic regions that are associated with PDAC risk. We also predicted the associated genes and disrupt motifs. Our findings provide new insights into the regulatory mechanisms of noncoding regions for pancreatic tumorigenesis.

The Role of Krüppel-like Factors in Pancreatic Physiology and Pathophysiology

Krüppel-like factors (KLFs) belong to the family of transcription factors with three highly conserved zinc finger domains in the C-terminus. They regulate homeostasis, development, and disease progression in many tissues. It has been shown that KLFs play an essential role in the endocrine and exocrine compartments of the pancreas. They are necessary to maintain glucose homeostasis and have been implicated in the development of diabetes. Furthermore, they can be a vital tool in enabling pancreas regeneration and disease modeling. Finally, the KLF family contains proteins that act as tumor suppressors and oncogenes. A subset of members has a biphasic function, being upregulated in the early stages of oncogenesis and stimulating its progression and downregulated in the late stages to allow for tumor dissemination. Here, we describe KLFs' function in pancreatic physiology and pathophysiology.

New insights into KLFs and SOXs in cancer pathogenesis, stemness, and therapy

Despite the development of cancer therapies, the success of most treatments has been impeded by drug resistance. The crucial role of tumor cell plasticity has emerged recently in cancer progression, cancer stemness and eventually drug resistance. Cell plasticity drives tumor cells to reversibly convert their cell identity, analogous to differentiation and dedifferentiation, to adapt to drug treatment. This phenotypical switch is driven by alteration of the transcriptome. Several pluripotent factors from the KLF and SOX families are closely associated with cancer pathogenesis and have been revealed to regulate tumor cell plasticity. In this review, we particularly summarize recent studies about KLF4, KLF5 and SOX factors in cancer development and evolution, focusing on their roles in cancer initiation, invasion, tumor hierarchy and heterogeneity, and lineage plasticity. In addition, we discuss the various regulation of these transcription factors and related cutting-edge drug development approaches that could be used to drug "undruggable" transcription factors, such as PROTAC and PPI targeting, for targeted cancer therapy. Advanced knowledge could pave the way for the development of novel drugs that target transcriptional regulation and could improve the outcome of cancer therapy.

YB-1 is a positive regulator of KLF5 transcription factor in basal-like breast cancer

Y-box binding protein 1 (YB-1) is a well-known oncogene highly expressed in various cancers, including basal-like breast cancer (BLBC). Beyond its role as a transcription factor, YB-1 is newly defined as an epigenetic regulator involving RNA 5-methylcytosine. However, its specific targets and pro-cancer functions are poorly defined. Here, based on clinical database, we demonstrate a positive correlation between Kruppel-like factor 5 (KLF5) and YB-1 expression in breast cancer patients, but a negative correlation with that of Dachshund homolog 1 (DACH1). Mechanistically, YB-1 enhances KLF5 expression not only through transcriptional activation that can be inhibited by DACH1, but also by stabilizing KLF5 mRNA in a RNA 5-methylcytosine modification-dependent manner. Additionally, ribosomal S6 kinase 2 (RSK2) mediated YB-1 phosphorylation at Ser102 promotes YB-1/KLF5 transcriptional complex formation, which co-regulates the expression of BLBC specific genes, Keratin 16 (KRT16) and lymphocyte antigen 6 family member D (Ly6D), to promote cancer cell proliferation. The RSK inhibitor, LJH685, suppressed BLBC cell tumourigenesis in vivo by disturbing YB-1-KLF5 axis. Our data suggest that YB-1 positively regulates KLF5 at multiple levels to promote BLBC progression. The novel RSK2-YB-1-KLF5-KRT16/Ly6D axis provides candidate diagnostic markers and therapeutic targets for BLBC.

Hypoxia Promotes Glioma Stem Cell Proliferation by Enhancing the 14-3-3β Expression via the PI3K Pathway

Glioma is a serious fatal type of cancer with the shorter median survival period and poor quality of living. The overall 5-year survival rate remains low due to high recurrence rates. Glioma stem cells (GSCs) play the important roles in the development of gliomas. Examination of the numerous biomarkers or cancer-associated genes involved in the development or prevention of glioma may therefore serve the discovery of novel strategies to treat patients with glioma. Hypoxia induced by using CoCl2 application and 14-3-3β protein knockdown by specific small interfering RNA transfection were performed in GSCs both in vitro and in vivo to observe their role in glioma progression and metastasis occurrence by using western blot analysis and MTT assay. The results demonstrated that CoCl2 application enhanced the 14-3-3β protein expression and mRNA levels via the PI3K pathway in GSCs. Furthermore, hypoxia promoted GSC cell proliferation and activated the expression of proliferating cell nuclear antigen, which was inhibited following 14-3-3β knockdown. In addition, tumor growth in mice was enhanced by CoCl2 application but reversed following 14-3-3β knockdown, which also enhanced GSC cell apoptosis. In conclusion, the present study demonstrated that hypoxia promoted glioma growth both in vitro and in vivo by increasing the 14-3-3β expression via the PI3K signaling pathway. 14-3-3β and HIF-1α may therefore be considered as the potential therapeutic target to treat patients with glioma.

Metastatic Transition of Pancreatic Ductal Cell Adenocarcinoma Is Accompanied by the Emergence of Pro-Invasive Cancer-Associated Fibroblasts

Cancer-associated fibroblasts (CAFs) are now appreciated as key regulators of cancer metastasis, particularly in cancers with high stromal content, e.g., pancreatic ductal cell carcinoma (PDAC). However, it is not yet well understood if fibroblasts are always primed to be cooperative in PDAC transition to metastasis, if they undergo transformation which ensures their cooperativity, and if such transformations are cancer-driven or intrinsic to fibroblasts. We performed a fibroblast-centric analysis of PDAC cancer, as it transitioned from the primary site to trespass stromal compartment reaching the lymph node using published single-cell RNA sequencing data by Peng et al. We have characterized the change in fibroblast response to cancer from a normal wound healing response in the initial stages to the emergence of subclasses with myofibroblast and inflammatory fibroblasts such as signatures. We have previously posited "Evolved Levels of Invasibility (ELI)", a framework describing the evolution of stromal invasability as a selected phenotype, which explains the large and correlated reduction in stromal invasion by placental trophoblasts and cancer cells in certain mammals. Within PDAC samples, we found large changes in fibroblast subclasses at succeeding stages of PDAC progression, with the emergence of specific subclasses when cancer trespasses stroma to metastasize to proximal lymph nodes (stage IIA to IIB). Surprisingly, we found that the initial metastatic transition is accompanied by downregulation of ELI-predicted pro-resistive genes, and the emergence of a subclass of fibroblasts with ELI-predicted increased invasibility. Interestingly, this trend was also observed in stellate cells. Using a larger cohort of bulk RNAseq data from The Cancer Genome Atlas for PDAC cancers, we confirmed that genes describing this emergent fibroblast subclass are also correlated with lymph node metastasis of cancer cells. Experimental testing of selected genes characterizing pro-resistive and pro-invasive fibroblast clusters confirmed their contribution in regulating stromal invasability as a phenotype. Our data confirm that the complexity of stromal response to cancer is really a function of stage-wise emergence of distinct fibroblast clusters, characterized by distinct gene sets which confer initially a predominantly pro-resistive and then a pro-invasive property to the stroma. Stromal response therefore transitions from being tumor-limiting to a pro-metastatic state, facilitating stromal trespass and the onset of metastasis.

A New Hypothetical Concept in Metabolic Understanding of Cardiac Fibrosis: Glycolysis Combined with TGF-β and KLF5 Signaling

The accumulation of fibrosis in cardiac tissues is one of the leading causes of heart failure. The principal cellular effectors in cardiac fibrosis are activated fibroblasts and myofibroblasts, which serve as the primary source of matrix proteins. TGF-β signaling pathways play a prominent role in cardiac fibrosis. The control of TGF-β by KLF5 in cardiac fibrosis has been demonstrated for modulating cardiovascular remodeling. Since the expression of KLF5 is reduced, the accumulation of fibrosis diminishes. Because the molecular mechanism of fibrosis is still being explored, there are currently few options for effectively reducing or reversing it. Studying metabolic alterations is considered an essential process that supports the explanation of fibrosis in a variety of organs and especially the glycolysis alteration in the heart. However, the interplay among the main factors involved in fibrosis pathogenesis, namely TGF-β, KLF5, and the metabolic process in glycolysis, is still indistinct. In this review, we explain what we know about cardiac fibroblasts and how they could help with heart repair. Moreover, we hypothesize and summarize the knowledge trend on the molecular mechanism of TGF-β, KLF5, the role of the glycolysis pathway in fibrosis, and present the future therapy of cardiac fibrosis. These studies may target therapies that could become important strategies for fibrosis reduction in the future.

Krüppel-like factor (KLF)5: An emerging foe of cardiovascular health

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors, which regulate various pathways that pertain to development, metabolism and other cellular mechanisms. KLF5 was first cloned in 1993 and by 1999, it was reported as the intestinal-enriched KLF. Beyond findings that have associated KLF5 with normal development and cancer, it has been associated with various types of cardiovascular (CV) complications and regulation of metabolic pathways in the liver, heart, adipose tissue and skeletal muscle. Specifically, increased KLF5 expression has been linked with cardiomyopathy in diabetes, end-stage heart failure, and as well as in vascular atherosclerotic lesions. In this review article, we summarize research findings about transcriptional, post-transcriptional and post-translational regulation of KLF5, as well as the role of KLF5 in the biology of cells and organs that affect cardiovascular health either directly or indirectly. Finally, we propose KLF5 inhibition as an emerging approach for cardiovascular therapeutics.

KLF5, a Novel Therapeutic Target in Squamous Cell Carcinoma

Squamous cell carcinomas (SCCs) are the most common ectodermal cancers, and result in more than 300,000 deaths per year. The Krüppel-like family of transcription factors play a critical role in cancer pathogenesis. The Krüppel-like factor 5 gene (KLF5), which is a member of Krüppel-like family, has been reported to promote cancer cell proliferation and tumorigenesis. In this review, we discuss the roles of KLF5 in different SCCs and the mechanisms by which KLF5 transcriptionally regulates its target gene expression in the pathogenesis and progression of SCCs. Due to its significant functions in cell proliferation and differentiation, KLF5 could be a novel diagnostic biomarker and therapeutic target for the treatment of SCCs.

KLF5-induced lncRNA IGFL2-AS1 promotes basal-like breast cancer cell growth and survival by upregulating the expression of IGFL1

Basal-like breast cancer (BLBC) is the most malignant subtype of breast cancer and has a poor prognosis. Kruppel-like factor 5 (KLF5) is an oncogenic transcription factor in BLBCs. The mechanism by which KLF5 promotes BLBC by regulating the transcription of lncRNAs has not been fully elucidated. In this study, we discovered that lncRNA IGFL2-AS1 is a downstream target gene of KLF5 and that IGFL2-AS1 mediates the pro-proliferation and pro-survival functions of KLF5. Additionally, we demonstrated that IGFL2-AS1 functions by upregulating the transcription of its neighboring gene IGFL1 via two independent mechanisms. On the one hand, nuclear IGFL2-AS1 promotes the formation of a KLF5/TEAD4 transcriptional complex at the IGFL1 gene enhancer. On the other hand, cytoplasmic IGFL2-AS1 inhibits the expression of miR4795-3p, which targets the IGFL1 gene. TNFα induces the expression of IGFL2-AS1 and IGFL1 through KLF5. Taken together, the results of this study indicate that IGFL2-AS1 and IGFL1 may serve as new therapeutic targets for BLBCs.

The roles and regulation of the KLF5 transcription factor in cancers

Krüppel‐like factor 5 (KLF5) is a member of the KLF family. Recent studies have suggested that KLF5 regulates the expression of a large number of new target genes and participates in diverse cellular functions, such as stemness, proliferation, apoptosis, autophagy, and migration. In response to multiple signaling pathways, various transcriptional modulation and posttranslational modifications affect the expression level and activity of KLF5. Several transgenic mouse models have revealed the physiological and pathological functions of KLF5 in different cancers. Studies of KLF5 will provide prognostic biomarkers, therapeutic targets, and potential drugs for cancers.

Pancreatitis initiated pancreatic ductal adenocarcinoma: Pathophysiology explaining clinical evidence

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant lethal disease due to its asymptomatic at its early lesion of the disease and drug resistance. Target therapy associated with molecular pathways so far seems not to produce reasonable outcomes. Understanding of the molecular mechanisms underlying inflammation-initiated tumorigenesis may be helpful for development of an effective therapy of the disease. A line of studies showed that pancreatic tumorigenesis was resulted from pancreatitis, which was caused synergistically by various pancreatic cells. This review focuses on those players and their possible clinic implications, such as exocrine acinar cells, ductal cells, and various stromal cells, including pancreatic stellate cells (PSCs), macrophages, lymphocytes, neutrophils, mast cells, adipocytes and endothelial cells, working together with each other in an inflammation-mediated microenvironment governed by a myriad of cellular signaling networks towards PDAC.

Roles of Krüppel-like factor 5 in kidney disease

Transcription factor Krüppel-like factor 5 (KLF5) is a member of the Krüppel-like factors' (KLFs) family. KLF5 regulates a number of cellular functions, such as apoptosis, proliferation and differentiation. Therefore, KLF5 can play a role in many diseases, including, cancer, cardiovascular disease and gastrointestinal disorders. An important role for KLF5 in the kidney was recently reported, such that KLF5 regulated podocyte apoptosis, renal cell proliferation, tubulointerstitial inflammation and renal fibrosis. In this review, we have summarized the available information in the literature with a brief description on how transcriptional, post-transcriptional and post-translational modifications of KLF5 modulate its function in a variety of organs including the kidney with a focus of its importance on the pathogenesis of various kidney diseases. Furthermore, we also have outlined the current and possible mechanisms of KLF5 activation in kidney diseases. These studies suggest a need for more systemic investigations, particularly for generation of animal models with renal cell-specific deletion or overexpression of KLF5 gene to examine direct contributions of KLF5 to various kidney diseases. This will promote further experimentation in the development of therapies to prevent or treat various kidney diseases.

Prognostic Value and Function of KLF5 in Papillary Thyroid Cancer

Simple Summary

This study was conducted to investigate the clinical significance and prognostic value of KLF5 in a large cohort of Middle Eastern PTC patients and explore its functional role and mechanism in PTC cell lines in vitro and in vivo. We found KLF5 over-expression in PTC patient cases and this was significantly associated with aggressive clinico-pathological parameters and worse outcome. We also found a significant association between KLF5 and HIF-1α in PTC patients and cell lines. Functionally, KLF5 promoted cell growth, stemness, invasion, migration, and angiogenesis, while its inhibition reverses its action in PTC cell lines. Finally, the depletion of KLF5 regressed PTC tumor growth in nude mice. These data suggest that KLF5 may potentially be a suitable therapeutic target in PTC, and pharmacological inhibition of KLF5 might be a viable therapeutic option for the treatment of patients with an aggressive subtype of PTC.

Abstract

The Krüppel-like factor 5 (KLF5), a zinc-finger transcriptional factor, is highly expressed in several solid tumors, but its role in PTC remains unclear. We investigated the expression of KLF5 protein in a large cohort of PTC patient samples and explored its functional role and mechanism in PTC cell lines in vitro and in vivo. KLF5 overexpression was observed in 65.1% of all PTC cases and it was significantly associated with aggressive clinico-pathological parameters and poor outcome. Given the significant association between KLF5 and HIF-1α overexpression in PTC patients, we investigated the functional correlation between KLF5 and HIF-1α in PTC cells. Indeed, the analysis revealed the co-immunoprecipitation of KLF5 with HIF-1α in PTC cells. We also identified KLF5-binding sites in the HIF-1α promoter that specifically bound to KLF5 protein. Mechanistically, KLF5 promoted PTC cell growth, invasion, migration, and angiogenesis, while KLF5 downregulation via specific inhibitor or siRNA reverses its action in vitro. Importantly, the silencing of KLF5 decreases the self-renewal ability of spheroids generated from PTC cells. In addition, the depletion of KLF5 reduces PTC xenograft growth in vivo. These findings suggest KLF5 can be a possible new molecular therapeutic target for a subset of PTC.

Krupple-Like Factor 5 is a Potential Therapeutic Target and Prognostic Marker in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecological malignancy. Despite current therapeutic and surgical options, advanced EOC shows poor prognosis. Identifying novel molecular therapeutic targets is highly needed in the management of EOC. Krupple-like factor 5 (KLF5), a zinc-finger transcriptional factor, is highly expressed in a variety of cancer types. However, its role and expression in EOC is not fully illustrated. Immunohistochemical analysis was performed to assess KLF5 protein expression in 425 primary EOC samples using tissue microarray. We also addressed the function of KLF5 in EOC and its interaction with signal transducer and activator of transcription 3 (STAT3) signaling pathway. We found that KLF5 overexpressed in 53% (229/425) of EOC samples, and is associated with aggressive markers. Forced expression of KLF5 enhanced cell growth in low expressing EOC cell line, MDAH2774. Conversely, knockdown of KLF5 reduced cell growth, migration, invasion and progression of epithelial to mesenchymal transition in KLF5 expressing cell lines, OVISE and OVSAHO. Importantly, silencing of KLF5 decreased the self-renewal ability of spheroids generated from OVISE and OVSAHO cell lines. In addition, downregulation of KLF5 potentiated the effect of cisplatin to induce apoptosis in these cell lines. These data reveals the pro-tumorigenic role of KLF5 in EOC and uncover its role in activation of STAT3 signaling pathway, suggesting the importance of KLF5 as a potential therapeutic target for EOC therapy.

PLA2G16 is a mutant p53/KLF5 transcriptional target and promotes glycolysis of pancreatic cancer

PLA2G16 is a member of the phospholipase family that catalyses the generation of lysophosphatidic acids (LPAs) and free fatty acids (FFAs) from phosphatidic acid. In the current study, we explored the functional role of PLA2G16 in pancreatic adenocarcinoma (PAAD) and the genetic/epigenetic alterations leading to its dysregulation. Bioinformatic analysis was performed using data from The Cancer Genome Atlas (TCGA), Genotype‐Tissue Expression (GTEx) and the Human Protein Atlas (HPA). Then, PANC‐1 and MIA‐PaCa‐2 cells harbouring TP53 mutations were used for cellular and animal studies. Results showed that PL2G16 expression was significantly up‐regulated in PAAD tissue and was associated with unfavourable survival. PLA2G16 inhibition suppressed pancreatic cell growth in vitro and in vivo and also inhibited aerobic glycolysis. Bioinformatic analysis indicated that KLF5 was positively correlated with PLA2G16 expression in PAAD tumours with TP53 mutation. TP53 or KLF5 inhibition significantly reduced PLA2G16 expression at both mRNA and protein levels. Dual‐luciferase and chromatin Immunoprecipitation‐quantitative polymerase chain reaction assays showed that KLF5 directly bound to the PLA2G16 promoter and activated its transcription. Co‐immunoprecipitation assay indicated that mutant p53 had a physical interaction with KLF5. Inhibition of mutant p53 impaired the transcriptional activating effects of KLF5. In PAAD cases in TCGA, PLA2G16 expression was positively correlated with its copy number (Pearson's r = 0.51, P < 0.001), but was strongly and negatively correlated with the methylation level of cg09518969 (Pearson's r = −0.64, P < 0.001), a 5’‐cytosine‐phosphodiester bond‐guanine‐3’ site within its gene locus. In conclusion, this study revealed a novel mutant p53/KLF5‐PLA2G16 regulatory axis on tumour growth and glycolysis in PAAD.

Krüppel-like Factor 5 Promotes Sonic Hedgehog Signaling and Neoplasia in Barrett's Esophagus and Esophageal Adenocarcinoma

Krüppel-like Factor 5 (KLF5) is a zinc-finger transcription factor associated with cell cycle progression and cell survival. KLF5 plays a key role in mammalian intestinal epithelium development and maintenance, expressed at high levels in basal proliferating cells and low levels in terminally differentiated cells. Considering Barrett's esophagus (BE) and esophageal adenocarcinoma's (EAC) histopathological similarities to intestinal epithelium, we sought to determine KLF5's role in BE and EAC, as well as KLF5's possible connection to the sonic hedgehog (SHH) pathway which is highly active in BE and EAC development. Low levels of KLF5 mRNA were found in BE cell lines and tissue- similar to what has been reported in differentiated intestinal epithelium. In contrast, higher KLF5 levels were observed in EAC cells and tissues. KLF5 knockdown in EAC cells caused significant decreases in cell migration, proliferation, and EAC-associated gene expression. Moreover, KLF5 knockdown led to decreased SHH signaling. These results suggest that KLF5 is connected to the SHH pathway in BE and EAC and may represent a potential drug target in EAC; further studies are now indicated to verify these findings and elucidate underlying mechanisms involved.

Krüpple-like factor 5 is essential for mammary gland development and tumorigenesis

Krüpple-like factor 5 (KLF5) is required for the development of the embryo and multiple organs, such as the lung and intestine. KLF5 plays a pro-proliferative and oncogenic role in several carcinomas, including breast cancer. However, its role in normal mammary gland development and oncogenesis has not been elucidated in vivo. In this study, we used mammary gland-specific Klf5 conditional knockout mice derived by mating Klf5-LoxP and MMTV-Cre mice. The genetic ablation of Klf5 suppresses mammary gland ductal elongation and lobuloalveolar formation. Klf5 deficiency inhibits mammary epithelial cell proliferation, survival, and stem cell maintenance. Klf5 promotes mammary stemness, at least partially, by directly promoting the transcription of Slug. Finally, Klf5 depletion suppressed PyMT-induced mammary gland tumor cell stemness, tumor initiation, and growth in vivo. Slug also mediated these functions of Klf5 in vivo. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The roles of TNFAIP2 in cancers and infectious diseases

TNFα‐induced protein 2 (TNFAIP2) is a primary response gene of TNFα. TNFAIP2 is highly expressed in immune cells and the urinary bladder. The expression of TNFAIP2 is regulated by multiple transcription factors and signalling pathways, including NF‐κB, KLF5 and retinoic acid. Physiologically, TNFAIP2 appears to be a multiple functional mediator not only for inflammation, angiogenesis and tunneling nanotube (TNT) formation but also as a regulator of cell proliferation and migration. The expression of TNFAIP2 is frequently abnormal in human cancers and in infectious diseases. Due to its significant functions in cell proliferation, angiogenesis, migration and invasion, TNFAIP2 could be a potential diagnostic biomarker and therapeutic target for cancer.

KLF15 suppresses cell growth and predicts prognosis in lung adenocarcinoma

Krüppel-like factors (KLFs) are transcription factors containing three different C2H2-type zinc finger domains in their carboxy-terminal regions which have been identified to play important roles in a variety of cancers. However, little is known about KLF15 in lung adenocarcinoma (LAUD). Our study demonstrated that the expression levels of KLF15 were observably down-regulated in LAUD tissues compared to paired adjacent normal tissues. LUAD patients with low expression levels of KLF15 have worse prognosis than those with high expression levels of KLF15. KLF15 could suppress cell growth, which was partly via up-regulating CDKN1 A/p21 and CDKN2A/p15. Our findings suggested that KLF15 showed a significant role in LAUD progression and may shed light on a promising novel therapeutic target for blocking progression of LAUD.

Krüppel-like Factor 5, Increased in Pancreatic Ductal Adenocarcinoma, Promotes Proliferation, Acinar-to-Ductal Metaplasia, Pancreatic Intraepithelial Neoplasia, and Tumor Growth in Mice

BACKGROUND & AIMS

Activating mutations in KRAS are detected in most pancreatic ductal adenocarcinomas (PDACs). Expression of an activated form of KRAS (KrasG12D) in pancreata of mice is sufficient to induce formation of pancreatic intraepithelial neoplasia (PanINs)-a precursor of PDAC. Pancreatitis increases formation of PanINs in mice that express KrasG12D by promoting acinar-to-ductal metaplasia (ADM). We investigated the role of the transcription factor Krüppel-like factor 5 (KLF5) in ADM and KRAS-mediated formation of PanINs.

METHODS

We performed studies in adult mice with conditional disruption of Klf5 (Klf5fl/fl) and/or expression of KrasG12D (LSL-KrasG12D) via CreERTM recombinase regulated by an acinar cell-specific promoter (Ptf1a). Activation of KrasG12D and loss of KLF5 was achieved by administration of tamoxifen. Pancreatitis was induced in mice by administration of cerulein; pancreatic tissues were collected, analyzed by histology and immunohistochemistry, and transcriptomes were compared between mice that did or did not express KLF5. We performed immunohistochemical analyses of human tissue microarrays, comparing levels of KLF5 among 96 human samples of PDAC. UN-KC-6141 cells (pancreatic cancer cells derived from Pdx1-Cre;LSL-KrasG12D mice) were incubated with inhibitors of different kinases and analyzed in proliferation assays and by immunoblots. Expression of KLF5 was knocked down with small hairpin RNAs or CRISPR/Cas9 strategies; cells were analyzed in proliferation and gene expression assays, and compared with cells expressing control vectors. Cells were subcutaneously injected into flanks of syngeneic mice and tumor growth was assessed.

RESULTS

Of the 96 PDAC samples analyzed, 73% were positive for KLF5 (defined as nuclear staining in more than 5% of tumor cells). Pancreata from Ptf1a-CreERTM;LSL-KrasG12D mice contained ADM and PanIN lesions, which contained high levels of nuclear KLF5 within these structures. In contrast, Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice formed fewer PanINs. After cerulein administration, Ptf1a-CreERTM;LSL-KrasG12D mice formed more extensive ADM than Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice. Pancreata from Ptf1a-CreERTM;LSL-KrasG12D;Klf5fl/fl mice had increased expression of the tumor suppressor NDRG2 and reduced phosphorylation (activation) of STAT3, compared with Ptf1a-CreERTM;LSL-KrasG12D mice. In UN-KC-6141 cells, PI3K and MEK signaling increased expression of KLF5; a high level of KLF5 increased proliferation. Cells with knockdown of Klf5 had reduced proliferation, compared with control cells, had reduced expression of ductal markers, and formed smaller tumors (71.61 ± 30.79 mm3 vs 121.44 ± 34.90 mm3 from control cells) in flanks of mice.

CONCLUSION

Levels of KLF5 are increased in human PDAC samples and in PanINs of Ptf1a-CreERTM;LSL-KrasG12D mice, compared with controls. KLF5 disruption increases expression of NDRG2 and reduces activation of STAT3 and reduces ADM and PanINs formation in mice. Strategies to reduce KLF5 activity might reduce progression of acinar cells from ADM to PanIN and pancreatic tumorigenesis.

Inherited pancreatic cancer

Pancreatic cancers arise through a series of genetic events both inherited and acquired. Inherited genetic changes, both high penetrance and low penetrance, are an important component of pancreatic cancer risk, and may be used to characterize populations who will benefit from early detection. Furthermore, pancreatic cancer patients with inherited mutations may be particularly sensitive to certain targeted agents, providing an opportunity to personalized treatment. Family history of pancreatic cancer is one of the strongest risk factors for the disease, and is associated with an increased risk of caners at other sites, including but not limited to breast, ovarian and colorectal cancer. The goal of this chapter is to discuss the importance of family history of pancreatic cancer, and the known genes that account for a portion of the familial clustering of pancreatic cancer.

KLF5 promotes cervical cancer proliferation, migration and invasion in a manner partly dependent on TNFRSF11a expression

Although the transcription factor Krüppel-like factor 5 (KLF5) plays important roles in both inflammation and cancer, the mechanism by which this factor promotes cervical carcinogenesis remains unclear. In this study, we demonstrated a potential role for tumour necrosis factor receptor superfamily member 11a (TNFRSF11a), the corresponding gene of which is a direct binding target of KLF5, in tumour cell proliferation and invasiveness. Coexpression of KLF5 and TNFRSF11a correlated significantly with tumorigenesis in cervical tissues (P < 0.05) and manipulation of KLF5 expression positively affected TNFRSF11a mRNA and protein expression. Functionally, KLF5 promoted cancer cell proliferation, migration and invasiveness in a manner dependent partly on TNFRSF11a expression. Moreover, in vivo functional TNFRSF11a-knockdown mouse studies revealed suppression of tumorigenicity and liver metastatic potential. Notably, tumour necrosis factor (TNF)-α induced KLF5 expression by activating the p38 signalling pathway and high KLF5 and TNFRSF11a expression increased the risk of death in patients with cervical squamous cell carcinoma. Our results demonstrate that KLF5 and TNFRSF11a promote cervical cancer cell proliferation, migration and invasiveness.

SP and KLF Transcription Factors in Digestive Physiology and Diseases

Specificity proteins (SPs) and Krüppel-like factors (KLFs) belong to the family of transcription factors that contain conserved zinc finger domains involved in binding to target DNA sequences. Many of these proteins are expressed in different tissues and have distinct tissue-specific activities and functions. Studies have shown that SPs and KLFs regulate not only physiological processes such as growth, development, differentiation, proliferation, and embryogenesis, but pathogenesis of many diseases, including cancer and inflammatory disorders. Consistently, these proteins have been shown to regulate normal functions and pathobiology in the digestive system. We review recent findings on the tissue- and organ-specific functions of SPs and KLFs in the digestive system including the oral cavity, esophagus, stomach, small and large intestines, pancreas, and liver. We provide a list of agents under development to target these proteins.

Comprehensive Dissection of Transcriptome Data and Regulatory Factors in Pancreatic Cancer Cells

Features of pancreatic cancers include high mortality rates caused by rapid tumor progression and a lack of effective therapy. Underpinning the molecular mechanisms involved in the alteration of the gene expression program in the pancreatic cancer remains to be understood. In the current study, we performed a comprehensive analysis using 282 pancreatic tumor and normal samples from seven independent expression data sets to provide a better view on the interactions between different transcription factors (TFs) and the most affected biological pathways in pancreatic cancer. We highlighted common differentially expressed genes (DEGs) and common affected processes within pancreatic cancer samples. We revealed 16 main DE-TFs that regulated gene expression alterations as well as the most significant processes in pancreatic cancer compared to normal cells. For example, we found the upregulated FOXM1 to be a top regulator of pancreatic cellular transformation based on results from different analyses, including from its regulation of gene regulatory networks, its presence in protein complex, its significant regulation of genes related to cancer pathways, and its regulation of most of the identified DE-TFs. Furthermore, we provided a model and assessed the role of different DE-TFs in the regulation of the most affected pancreatic- and cancer-specific processes. In conclusion, our bioinformatics meta-analysis of high throughput expression data sets, besides clarifying common affected genes and pathways, also showed the mechanisms involved in regulating these common profiles. Our results, especially for DE-TFs, could potentially be useful for screening for pancreatic cancer, and for confirming or determining novel pharmacological targets. J. Cell. Biochem. 118: 3976-3985, 2017. © 2017 Wiley Periodicals, Inc.

Inflammatory stimuli promote growth and invasion of pancreatic cancer cells through NF-κB pathway dependent repression of PP2Ac

Previous studies have indicated that inflammatory stimulation represses protein phosphatase 2A (PP2A), a well-known tumor suppressor. However, whether PP2A repression participates in pancreatic cancer progression has not been verified. We used lipopolysaccharide (LPS) and macrophage-conditioned medium (MCM) to establish in vitro inflammation models, and investigated whether inflammatory stimuli affect pancreatic cancer cell growth and invasion PP2A catalytic subunit (PP2Ac)-dependently. Via nude mouse models of orthotopic tumor xenografts and dibutyltin dichloride (DBTC)-induced chronic pancreatitis, we evaluated the effect of an inflammatory microenvironment on PP2Ac expression in vivo. We cloned the PP2Acα and PP2Acβ isoform promoters to investigate the PP2Ac transcriptional regulation mechanisms. MCM accelerated pancreatic cancer cell growth; MCM and LPS promoted cell invasion. DBTC promoted xenograft growth and metastasis, induced tumor-associated macrophage infiltration, promoted angiogenesis, activated the nuclear factor-κB (NF-κB) pathway, and repressed PP2Ac expression. In vitro, LPS and MCM downregulated PP2Ac mRNA and protein. PP2Acα overexpression attenuated JNK, ERK, PKC, and IKK phosphorylation, and impaired LPS/MCM-stimulated cell invasion and MCM-promoted cell growth. LPS and MCM activated the NF-κB pathway in vitro. LPS and MCM induced IKK and IκB phosphorylation, leading to p65/RelA nuclear translocation and transcriptional activation. Overexpression of the dominant negative forms of IKKα attenuated LPS and MCM downregulation of PP2Ac, suggesting inflammatory stimuli repress PP2Ac expression NF-κB pathway-dependently. Luciferase reporter gene assay verified that LPS and MCM downregulated PP2Ac transcription through an NF-κB-dependent pathway. Our study presents a new mechanism in inflammation-driven cancer progression through NF-κB pathway-dependent PP2Ac repression.

Longer warm ischemia can accelerate tumor growth through the induction of HIF-1α and the IL-6-JAK-STAT3 signaling pathway in a rat hepatocellular carcinoma model

BACKGROUND

The present study aimed to investigate the impact of the duration of hepatic pedicle clamping (HPC) on tumor growth after major hepatectomy in a rat model.

METHODS

Rats were divided into four groups according to the length of HPC during 70% partial hepatectomy followed by N1S1 tumor cell implantation: group 1, without HPC; group 2, with 5-min HPC; group 3, 10-min HPC; and group 4, 15-min HPC. At three weeks after tumor cell implantation, liver tumor growth and its possible mechanisms were investigated.

RESULTS

The number and largest diameter of liver tumor were significantly greater in group 4. At 6 h after reperfusion, serum levels of inflammatory cytokines including interleukin (IL)-6 were significantly higher in group 4 compared with the other groups. In the tumor tissues, the expression of hypoxia inducible factor (HIF)-1α (P < 0.001 versus group 2, P < 0.001 versus group 3) and that of phospho-signal transducer and activator of transcription 3 (STAT3) (P < 0.001 versus group 2, P = 0.026 versus group 3) were significantly upregulated in group 4.

CONCLUSIONS

Longer HPC followed by reperfusion accelerated hepatocellular carcinoma growth through the induction of HIF-1α and the activation of the IL-6-JAK-STAT3 signaling pathway.

Klf5 regulates muscle differentiation by directly targeting muscle-specific genes in cooperation with MyoD in mice

Krüppel-like factor 5 (Klf5) is a zinc-finger transcription factor that controls various biological processes, including cell proliferation and differentiation. We show that Klf5 is also an essential mediator of skeletal muscle regeneration and myogenic differentiation. During muscle regeneration after injury (cardiotoxin injection), Klf5 was induced in the nuclei of differentiating myoblasts and newly formed myofibers expressing myogenin in vivo. Satellite cell-specific Klf5 deletion severely impaired muscle regeneration, and myotube formation was suppressed in Klf5-deleted cultured C2C12 myoblasts and satellite cells. Klf5 knockdown suppressed induction of muscle differentiation-related genes, including myogenin. Klf5 ChIP-seq revealed that Klf5 binding overlaps that of MyoD and Mef2, and Klf5 physically associates with both MyoD and Mef2. In addition, MyoD recruitment was greatly reduced in the absence of Klf5. These results indicate that Klf5 is an essential regulator of skeletal muscle differentiation, acting in concert with myogenic transcription factors such as MyoD and Mef2.

Resveratrol inhibits hyperglycemia-driven ROS-induced invasion and migration of pancreatic cancer cells via suppression of the ERK and p38 MAPK signaling pathways

Increasing evidence suggests that there is a strong relationship between diabetes mellitus (DM) and pancreatic cancer. Our previous study revealed that hyperglycemia could enhance the invasive and migratory activities of pancreatic cancer cells. Resveratrol, a natural polyphenolic phytoalexin, has many biological and pharmaceutical properties, including antioxidant and anti-tumorigenic capabilities. The aim of the present study was to evaluate whether resveratrol affects hyperglycemia-induced reactive oxygen species (ROS) production as well as the invasion and migration of pancreatic cancer and its underlying mechanisms. Human pancreatic cancer Panc-1 cells were exposed to high glucose condition with or without resveratrol, N-acetylcysteine (NAC, a scavenger of free radicals), PD 98059 (an ERK inhibitor) or SB 203580 (a p38 MAPK inhibitor). The intracellular ROS and hydrogen peroxide (H2O2) were determined using 2,7-dichlorodihydrofluorecein diacetate and H2O2 assay. MTT, wound healing assay and transwell matrigel invasion assay were used to detect the proliferation, migration and invasion potential of cancer cells. The expressions of uPA, E-cadherin and Glut-1 were examined using QT-PCR and western blot analysis at mRNA and protein levels. The activation of p-ERK, p-p38 and p-NF-κB were measured by western blot analysis. The results of the present study showed that resveratrol could significantly decrease high glucose-induced production of ROS and H2O2 in Panc-1 cells. Resveratrol was also able to inhibit high glucose-induced proliferation, migration and invasion of pancreatic cancer cells. High glucose-modulated expression of uPA, E-cadherin and Glut-1 were inhibited by resveratrol. In addition, high glucose-induced activation of ERK and p38 MAPK signaling pathways as well as the transcription factor NF-κB could also be suppressed by resveratrol. Furthermore, resveratrol was able to suppress H2O2-induced migration and invasion abilities of pancreatic cancer cells. Taken together, these data indicate that resveratrol plays an important role in suppressing hyperglycemia-driven ROS-induced pancreatic cancer progression by inhibiting the ERK and p38 MAPK signaling pathways, providing evidence that resveratrol might be a potential candidate for chemoprevention of pancreatic cancer.

Epidemiology and Inherited Predisposition for Sporadic Pancreatic Adenocarcinoma

Given the changing demographics of Western populations, the numbers of pancreatic cancer cases are projected to increase during the next decade. Diabetes, recent cigarette smoking, and excess body weight are the cancer's most consistent risk factors. The search for common and rare germline variants that influence risk of pancreatic cancer through genome-wide association studies and high-throughput-sequencing-based studies is underway and holds the promise of increasing the knowledge of variants and genes that play a role in inherited susceptibility of this disease. Research reported in this review has advanced the understanding of pancreatic cancer.

Pancreatic Cancer Genetics

Although relatively rare, pancreatic tumors are highly lethal [1]. In the United States, an estimated 48,960 individuals will be diagnosed with pancreatic cancer and 40,560 will die from this disease in 2015 [1]. Globally, 337,872 new pancreatic cancer cases and 330,391 deaths were estimated in 2012 [2]. In contrast to most other cancers, mortality rates for pancreatic cancer are not improving; in the US, it is predicted to become the second leading cause of cancer related deaths by 2030 [3, 4]. The vast majority of tumors arise in the exocrine pancreas, with pancreatic ductal adenocarcinoma (PDAC) accounting for approximately 95% of tumors. Tumors arising in the endocrine pancreas (pancreatic neuroendocrine tumors) represent less than 5% of all pancreatic tumors [5]. Smoking, type 2 diabetes mellitus (T2D), obesity and pancreatitis are the most consistent epidemiological risk factors for pancreatic cancer [5]. Family history is also a risk factor for developing pancreatic cancer with odds ratios (OR) ranging from 1.7-2.3 for first-degree relatives in most studies, indicating that shared genetic factors may play a role in the etiology of this disease [6-9]. This review summarizes the current knowledge of germline pancreatic cancer risk variants with a special emphasis on common susceptibility alleles identified through Genome Wide Association Studies (GWAS).

KLF5 mediates vascular remodeling via HIF-1α in hypoxic pulmonary hypertension

Hypoxic pulmonary hypertension (HPH) is characterized by active vasoconstriction and profound vascular remodeling. KLF5, a zinc-finger transcription factor, is involved in the excessive proliferation and apoptotic resistance phenotype associated with monocrotaline-induced pulmonary hypertension. However, the molecular mechanisms of KLF5-mediated pathogenesis of HPH are largely undefined. Adult male Sprague-Dawley rats were exposed to normoxia or hypoxia (10% O2) for 4 wk. Hypoxic rats developed pulmonary arterial remodeling and right ventricular hypertrophy with significantly increased right ventricular systolic pressure. The levels of KLF5 and hypoxia-inducible factor-1α (HIF-1α) were upregulated in distal pulmonary arterial smooth muscle from hypoxic rats. The knockdown of KLF5 via short-hairpin RNA attenuated chronic hypoxia-induced hemodynamic and histological changes in rats. The silencing of either KLF5 or HIF-1α prevented hypoxia-induced (5%) proliferation and migration and promoted apoptosis in human pulmonary artery smooth muscle cells. KLF5 was immunoprecipitated with HIF-1α under hypoxia and acted as an upstream regulator of HIF-1α. The cell cycle regulators cyclin B1 and cyclin D1 and apoptosis-related proteins including bax, bcl-2, survivin, caspase-3, and caspase-9, were involved in the regulation of KLF5/HIF-1α-mediated cell survival. This study demonstrated that KLF5 plays a crucial role in hypoxia-induced vascular remodeling in an HIF-1α-dependent manner and provided a better understanding of the pathogenesis of HPH.

KLF5 promotes breast cancer proliferation, migration and invasion in part by upregulating the transcription of TNFAIP2

The Kruppel-like factor 5 (KLF5) transcription factor is highly expressed in high-grade and basal-like breast cancers. However, the mechanism by which KLF5 promotes cell migration and invasion is still not completely understood. In this study, we demonstrate that TNFAIP2, a tumor necrosis factor-α (TNFα)-induced gene, is a direct KLF5 target gene. The expression of TNFAIP2 is highly correlated with the expression of KLF5 in breast cancers. The manipulation of KLF5 expression positively alters TNFAIP2 expression levels. KLF5 directly binds to the TNFAIP2 gene promoter and activates its transcription. Functionally, KLF5 promotes cancer cell proliferation, migration and invasion in part through TNFAIP2. TNFAIP2 interacts with the two small GTPases Rac1 and Cdc42, thereby increasing their activities to change actin cytoskeleton and cell morphology. These findings collectively suggest that TNFAIP2 is a direct KLF5 target gene, and both KLF5 and TNFAIP2 promote breast cancer cell proliferation, migration and invasion through Rac1 and Cdc42.

A pivotal role of Krüppel-like factor 5 in regulation of cancer stem-like cells in hepatocellular carcinoma

In hepatocellular carcinoma (HCC), there exists a highly tumorigenic subset of cells defined by high expression of CD44 and CD133 that has been reported to contain cancer stem-like cells (CSCs). Krüppel-like factor 5 (KLF5) regulates many factors involved in cell cycle, migration, inflammation, angiogenesis and stemness and has cancer-promoting effects in some cancers. While some reports have indicated that KLF5 may have important roles in regulation of CSCs, what role, if any, KLF5 plays in regulation of CSCs in HCC remains to be elucidated. Flow cytometric analysis of CD44 and CD133 in HCC cell lines revealed subpopulations of CD44(High)/CD133(High) and CD44(Low)/CD133(Low) cells. We subsequently sorted these subpopulations and identified KLF5 as a gene that is significantly upregulated in CD44(High)/CD44(High) cells via RNA sequencing using next generation sequencing technology. Moreover, KLF5 overexpression enriched the CD44(High)/CD133(High) subpopulation and, consistent with the up-regulation of CD44(High)/CD133(High) cells, KLF5 overexpressing cells were more resistant to anti-cancer drugs and displayed enhanced colony-formation capacity. By contrast, knock-down of KLF5 by siRNA diminished the CD44(High)/CD133(High) subpopulation. When KLF5 was acetylated by TGF-β1, the KLF5-mediated CD44(High)/CD133(High) subpopulation enrichment was abrogated. Oppositely, ectopic expression of an acetylation-deficient KLF5 mutant further increased CD44(High)/CD133(High) subpopulations as compared to cell expressing wild-type KLF5. These findings provide novel mechanistic insight into a pivotal role for KLF5 in the regulation of CSCs in HCC.

Cantharidin represses invasion of pancreatic cancer cells through accelerated degradation of MMP2 mRNA

Cantharidin is an active constituent of mylabris, a traditional Chinese medicine, and is a potent and selective inhibitor of protein phosphatase 2A (PP2A) that plays an important role in cell cycle control, apoptosis, and cell-fate determination. In the present study, we found that cantharidin repressed the invasive ability of pancreatic cancer cells and downregulated matrix metalloproteinase 2 (MMP2) expression through multiple pathways, including ERK, JNK, PKC, NF-κB, and β-catenin. Interestingly, transcriptional activity of the MMP2 promoter increased after treatment with PP2A inhibitors, suggesting the involvement of a posttranscriptional mechanism. By using an mRNA stability assay, we found accelerated degradation of MMP2 mRNA after treatment of cantharidin. Microarray analyses revealed that multiple genes involved in the 3' → 5' decay pathway were upregulated, especially genes participating in cytoplasmic deadenylation. The elevation of these genes were further demonstrated to be executed through ERK, JNK, PKC, NF-κB, and β-catenin pathways. Knockdown of PARN, RHAU, and CNOT7, three critical members involved in cytoplasmic deadenylation, attenuated the downregulation of MMP2. Hence, we present the mechanism of repressed invasion by cantharidin and other PP2A inhibitors through increased degradation of MMP2 mRNA by elevated cytoplasmic deadenylation.

Regulatory crosstalk between lineage-survival oncogenes KLF5, GATA4 and GATA6 cooperatively promotes gastric cancer development

OBJECTIVE

Gastric cancer (GC) is a deadly malignancy for which new therapeutic strategies are needed. Three transcription factors, KLF5, GATA4 and GATA6, have been previously reported to exhibit genomic amplification in GC. We sought to validate these findings, investigate how these factors function to promote GC, and identify potential treatment strategies for GCs harbouring these amplifications.

DESIGN

KLF5, GATA4 and GATA6 copy number and gene expression was examined in multiple GC cohorts. Chromatin immunoprecipitation with DNA sequencing was used to identify KLF5/GATA4/GATA6 genomic binding sites in GC cell lines, and integrated with transcriptomics to highlight direct target genes. Phenotypical assays were conducted to assess the function of these factors in GC cell lines and xenografts in nude mice.

RESULTS

KLF5, GATA4 and GATA6 amplifications were confirmed in independent GC cohorts. Although factor amplifications occurred in distinct sets of GCs, they exhibited significant mRNA coexpression in primary GCs, consistent with KLF5/GATA4/GATA6 cross-regulation. Chromatin immunoprecipitation with DNA sequencing revealed a large number of genomic sites co-occupied by KLF5 and GATA4/GATA6, primarily located at gene promoters and exhibiting higher binding strengths. KLF5 physically interacted with GATA factors, supporting KLF5/GATA4/GATA6 cooperative regulation on co-occupied genes. Depletion and overexpression of these factors, singly or in combination, reduced and promoted cancer proliferation, respectively, in vitro and in vivo. Among the KLF5/GATA4/GATA6 direct target genes relevant for cancer development, one target gene, HNF4α, was also required for GC proliferation and could be targeted by the antidiabetic drug metformin, revealing a therapeutic opportunity for KLF5/GATA4/GATA6 amplified GCs.

CONCLUSIONS

KLF5/GATA4/GATA6 may promote GC development by engaging in mutual crosstalk, collaborating to maintain a pro-oncogenic transcriptional regulatory network in GC cells.

DUSP10 regulates intestinal epithelial cell growth and colorectal tumorigenesis

Dual specificity phosphatase 10 (DUSP10), also known as MAP kinase phosphatase 5 (MKP5), negatively regulates the activation of MAP kinases. Genetic polymorphisms and aberrant expression of this gene are associated with colorectal cancer (CRC) in humans. However, the role of DUSP10 in intestinal epithelial tumorigenesis is not clear. Here, we showed that DUSP10 knockout (KO) mice had increased intestinal epithelial cell (IEC) proliferation and migration and developed less severe colitis than wild-type (WT) mice in response to dextran sodium sulphate (DSS) treatment, which is associated with increased ERK1/2 activation and Krüppel-like factor 5 (KLF5) expression in IEC. In line with increased IEC proliferation, DUSP10 KO mice developed more colon tumours with increased severity compared with WT mice in response to administration of DSS and azoxymethane (AOM). Furthermore, survival analysis of CRC patients demonstrated that high DUSP10 expression in tumours was associated with significant improvement in survival probability. Overexpression of DUSP10 in Caco-2 and RCM-1 cells inhibited cell proliferation. Our study showed that DUSP10 negatively regulates IEC growth and acts as a suppressor for CRC. Therefore, it could be targeted for the development of therapies for colitis and CRC.

Krüppel-like factors in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a disease with a high incidence and mortality rate worldwide. However, the mechanisms underlying its pathogenesis are still elusive. In recent years, studies on functions of Krüppel-like factors (KLFs) in HCC have shed new light on this field. To date, five members (KLF4, KLF6, KLF8, KLF9, and KLF17) in the KLF family have been reported to function in the pathogenesis of HCC in multiple ways, which hold the potential of deepening and widening our understanding in the initiation and progression of HCC. In this review, we focus on the functions, roles, and regulatory networks of these five KLFs in HCC, summarize key pathways, and propose areas for further investigation, with the hope that this review will provide a reliable and concise reference for readers interested in this area.

Role of Krüppel-like factors in cancer stem cells

Cancer stem cells (CSCs), or cancer cells with stem cell properties, are a rare population of tumor bulk and are recognized to be responsible for cancer recurrence, drug resistance, and metastasis. However, the molecular mechanisms of how to regulate the differentiation and self-renewing of CSCs are poorly understood. Krüppel-like factors (KLFs) are essential DNA-binding transcriptional regulators with diverse functions in various cellular processes, including differentiation, proliferation, inflammation, migration, and pluripotency. Recent progress has highlighted the significance of KLFs in tumor progression and CSCs. The regulatory functions of KLFs in the development of cancer and CSCs have become a burgeoning area of intense research. In this review, we summarize the current understanding and progress of the transcriptional regulation of KLFs in CSCs and discuss the functional implications of targeting CSCs by KLFs for cancer therapeutics.

A comprehensive analysis of candidate genes and pathways in pancreatic cancer

The study aimed to dissect the molecular mechanism of pancreatic cancer by a range of bioinformatics approaches. Three microarray datasets (GSE32676, GSE21654, and GSE14245) were downloaded from Gene Expression Omnibus database. Differentially expressed genes (DEGs) with logarithm of fold change (|logFC|) >0.585 and p value <0.05 were identified between pancreatic cancer samples and normal controls. Transcription factors (TFs) were selected from the DEGs based on TRASFAC database. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed for the DEGs using The Database for Annotation, Visualization and Integrated Discovery (p value <0.05), followed by construction of protein-protein interaction (PPI) network using Search Tool for the Retrieval of Interacting Genes software. Latent pathway identification analysis was applied to analyze the DEGs-related pathways crosstalk and the pathways with high weight value were included in the pathway crosstalk network using Cytoscape. Sixty-five DEGs were screened out. CCAAT/enhancer-binding protein delta (CEBPD), FBJ osteosarcoma oncogene B (FOSB), Stratifin (SFN), Krüppel-like factor 5 (KLF5), Pentraxin 3 (PTX3), and nuclear receptor subfamily 4, group A, member 3 (NR4A3) were important TFs. Interleukin-6 (IL-6) was the hub node of the PPI network. DEGs were significantly enriched in NOD-like receptor signaling pathway which was primarily interacted with inflammation and immune related pathways (cytosolic DNA-sensing, hematopoietic cell lineage, intestinal immune network for IgA production and chemokine pathways). The study suggested CEBPD, FOSB, SFN, KLF5, PTX3, NR4A3, IL-6, and NOD-like receptor pathways were involved in pancreatic cancer.

Molecular mechanisms of the suppression of axon regeneration by KLF transcription factors

Molecular mechanisms of the Krüppel-like family of transcription factors (KLFs) have been studied more in proliferating cells than in post-mitotic cells such as neurons. We recently found that KLFs regulate intrinsic axon growth ability in central nervous system (CNS) neurons including retinal ganglion cells, and hippocampal and cortical neurons. With at least 15 of 17 KLF family members expressed in neurons and at least 5 structurally unique subfamilies, it is important to determine how this complex family functions in neurons to regulate the intricate genetic programs of axon growth and regeneration. By characterizing the molecular mechanisms of the KLF family in the nervous system, including binding partners and gene targets, and comparing them to defined mechanisms defined outside the nervous system, we may better understand how KLFs regulate neurite growth and axon regeneration.

Krüppel-like factor 9 inhibits glioma cell proliferation and tumorigenicity via downregulation of miR-21

Krüppel-like factors (KLFs) are zinc finger-containing transcription factors that play key roles in the regulation of differentiation and development as well as biological processes central to the development of malignancies. Increasing evidence indicates that Krüppel-like factor 9 (KLF9) plays a critical role in regulating tumorigenesis. However, the biological role and molecular mechanism of KLF9 in glioma progression remain unclear. Herein, we found that KLF9 expression was strongly reduced in gliomas. Reduced KLF9 expression promoted glioma cell proliferation. Importantly, re-constitution of KLF9 expression inhibited glioma cell proliferation and tumor growth in vivo. Furthermore, we determined that KLF9 interacted with the miR-21 promoter, leading to suppression of miR-21 expression and cell cycle arrest. Taken together, our findings indicate a novel mechanism for KLF function in tumorigenesis and may also suggest new targets for clinical intervention in human cancer.

KLF5 promotes hypoxia-induced survival and inhibits apoptosis in non-small cell lung cancer cells via HIF-1α

Transcription factor Krüppel-like factors 5 (KLF5) is overexpressed in a wide range of tumor tissues and acts as a prognostic factor in cancer. However, the role of KLF5 in non-small cell lung cancer is not clear. Hypoxia plays a vital part in the development of cancer via hypoxia-inducible factor 1 (HIF-1). Our study showed that hypoxia (1% O2) increased cell viability, clonality and proliferation and inhibited cell apoptosis in A549 cells. The expression of HIF-1α and KLF5 was increased time-dependently in hypoxia. Using small interfering RNA (siRNA) targeting KLF5 or HIF-1α, we demonstrated that KLF5 or HIF-1α knockdown inhibited hypoxia-induced cell survival and promoted cell apoptosis by actively downregulating cyclin B1, survivin and upregulating caspase-3. Given the similar effect of KLF5 and HIF-1α on cell survival, an attempt was made to investigate the putative interaction of them in hypoxia. KLF5 was revealed to co-immunoprecipitate with HIF-1α and hypoxia increased the amount of KLF5 and HIF-1α complex. Moreover, silencing of KLF5 decreased HIF-1α expression while KLF5 was not affected by HIF-1α inhibition in hypoxia, confirming the effect of KLF5 on upregulation of HIF-1α. In conclusion, this study identified hypoxia as a tumor promoter by triggering KLF5 → HIF-1α → cyclin B1/survivin/caspase-3 in lung cancer cells.