Role of Krüppel-like factors in cancer stem cells

KLF2 transcription suppresses endometrial cancer cell proliferation, invasion, and migration through the inhibition of NPM1

Endometrial cancer (EC) is the most common gynaecologic malignancy. This study was to explore the role of kruppel-like factor 2 (KLF2) in EC cell behaviours. The expression of KLF2 in EC and its correlation with NPM1 were first predicted on the database. Levels of KLF2 and nucleophosmin 1 (NPM1) in EC cell lines were then determined. After transfection of the overexpression vector of KLF2 or NPM1, cell proliferation, invasion, and migration were evaluated. The binding relationship between KLF2 and the NPM1 promoter was analysed. KLF2 was downregulated while NPM1 was upregulated in EC cells. KLF2 overexpression reduced the proliferation potential of EC cells and the number of invaded and migrated cells. KLF2 was enriched in the NPM1 promoter and inhibited NPM1 transcriptional level. NPM1 overexpression neutralised the effects of KLF2 overexpression on suppressing EC cell growth. Collectively, KLF2 was decreased in EC cells and KLF2 overexpression increased the binding to the NPM1 promoter to inhibit NPM1 transcription, thus suppressing EC cell growth.

Knockdown of KLF7 inhibits the differentiation of both intramuscular and subcutaneous preadipocytes in goat

KLF7 belongs to the Krüppel-like factors (KLFs) family, which function as transcriptional regulators controlling a number of basic cellular processes, involving proliferation, differentiation, and migration. Here, we reveal insights into the differentiated expression of KLF7 in different goat tissues and different stages of growth, and the inhibition role of KLF7 knockdown to differentiation by using goat intramuscular and subcutaneous preadipocytes. We demonstrate that KLF7 expression is obviously changed during the differentiation of preadipocytes into mature adipocytes. Knockdown of KLF7 inhibited lipid droplet accumulation, reduced the expression of adipogenic markers both in intramuscular and subcutaneous preadipocytes in goats, suggesting that KLF7 is a novel regulator of adipogenesis. KLF7 expression changed also up or down-regulation the other KLF family members, but there were differences between these two types of cells. Investigation into the mechanism that KLF7 regulates preadipocyte differentiation revealed that KLF family members KLF1, KLF5, KLF6, KLF8, KLF11, KLF12, KLF16, KLF17 and adipogenic markers C/EBPα and SREBP1 promoter region present KLF7 transcriptional binding sites. Altogether, the data here identify KLF7 as a novel regulator of adipogenesis.

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.

Krüppel-like Factors 4 and 5 in Colorectal Tumorigenesis

Krüppel-like factors (KLFs) are transcription factors regulating various biological processes such as proliferation, differentiation, migration, invasion, and homeostasis. Importantly, they participate in disease development and progression. KLFs are expressed in multiple tissues, and their role is tissue- and context-dependent. KLF4 and KLF5 are two fascinating members of this family that regulate crucial stages of cellular identity from embryogenesis through differentiation and, finally, during tumorigenesis. They maintain homeostasis of various tissues and regulate inflammation, response to injury, regeneration, and development and progression of multiple cancers such as colorectal, breast, ovarian, pancreatic, lung, and prostate, to name a few. Recent studies broaden our understanding of their function and demonstrate their opposing roles in regulating gene expression, cellular function, and tumorigenesis. This review will focus on the roles KLF4 and KLF5 play in colorectal cancer. Understanding the context-dependent functions of KLF4 and KLF5 and the mechanisms through which they exert their effects will be extremely helpful in developing targeted cancer therapy.

Fat mass and obesity associated (FTO)-mediated N6-methyladenosine modification of Krüppel-like factor 3 (KLF3) promotes osteosarcoma progression

N6-methyladenosine (m6A) methylation is the most common and abundant methylation modification of eukaryotic mRNAs, which is involved in tumor initiation and progression. The study aims to explore the potential role and the regulatory mechanism of fat mass and obesity associated (FTO) in osteosarcoma (OS) progression. In this study, we detected the expressions of Krüppel-like factor 3 (KLF3) in OS cells and tissues and found that the mRNA and protein levels of KLF3 were increased in OS cells and tissues and significantly related to tumor size, metastasis, and TNM stage and poor prognosis of OS patients. FTO promoted the proliferation and invasion and suppressed apoptosis of OS cells through cell experiments in vitro. Further mechanism dissection revealed that FTO and YTHDF2 enforced the decay of KLF3 mRNA and decreased its expression. FTO-mediated mRNA demethylation inhibited KLF3 expression in the YTHDF2-dependent manner. Moreover, KLF3 overexpression abrogated FTO-induced oncogenic effects on the proliferation and invasion of OS cells. Overall, our findings showed that FTO-mediated m6A modification of KLF3 promoted OS progression, which may provide a therapeutic target for OS.

Effect of KLF17 overexpression on epithelial-mesenchymal transition of gastric cancer cells

Objective

To investigate Krüppel-like factor 17 (KLF17) expression in normal and gastric cancer tissues and cell lines.

Methods

Levels of KLF17 mRNA and protein in GES-1 normal gastric mucosal cells, and NCI-N87, SGC-7901, BGC-823 and HGC-27 gastric cancer cells were analysed by quantitative polymerase chain reaction (qPCR) and western blot. Differences in KLF17 expression between gastric cancer and adjacent tissues were analysed by qPCR and immunohistochemistry. Invasion/migration effects of KLF17 overexpression in BGC-823 and HGC-27 cells were analysed by wound-healing and Transwell chamber assays. Changes in expression of KLF17 and epithelial–mesenchymal transition (EMT)-related genes (matrix metalloproteinase [MMP]-9, vimentin and E-cadherin) were analysed in BGC-823 and HGC-27 cells before and after transfection using qPCR and western blot. Transforming growth factor (TGF)-β1, Smad family member (Smad)2/3 and phosphorylated-Smad2/3 levels in BGC-823 and HGC-27 cells were assessed by qPCR and western blot.

Results

KLF17 expression was lower in gastric cancer versus adjacent tissues, and in gastric cancer cell lines versus GES-1 normal gastric mucosal cells, and was positively correlated with degree of cancer-cell differentiation. Wound-healing and Transwell assays showed decreased migration and invasion ability of BGC-823 and HGC-27 cells transfected to overexpress KLF17. KLF17 overexpression was associated with decreased MMP-9 and vimentin in BGC-823 and HGC-27 cancer cells, and increased KLF17 and E-cadherin. KLF17 overexpression also resulted in decreased levels of TGF-β1 and p-Smad2/3 in BGC-823 and HGC-27 cancer cells.

Conclusion

KLF17 is poorly expressed in gastric cancer tissues and cell lines. KLF17 overexpression might inhibit EMT via the TGF-β/Smad pathway, thereby reducing gastric cancer cell invasion and migration. Therefore, KLF17 may become a novel target for treating gastric cancer.

KLF11 Expression Predicts Poor Prognosis in Glioma Patients

Purpose

Glioma is a primary intracranial malignant tumor with high recurrence and mortality rates. It is very important to study the prognostic factors. KLF11 can function as an oncogene or a tumor suppressor, depending on the tumor and tissue types and the cancer stage. In this study, we aimed to determine whether KLF11 expression is related to the overall survival of glioma patients.

Patients and Methods

We investigated KLF11 expression in 116 glioma patients with different grades using Western blot and immunohistochemistry assay. We analyzed the patients with different glioma grades and KLF11 expression levels by Kaplan-Meier survival curves. Independent prognostic factors for poor overall survival were identified by univariate and multivariate analyses.

Results

There were 37 patients in KLF11 low expression group and 79 patients in high expression group. There was no difference in gender, age, tumor diameter or tumor location between two groups. The patients in KLF11 high expression group had higher ECOG score (P =0.025) and higher WHO grades (P =0.029). Western blot and immunohistochemistry assay showed KLF11 expression was significantly upregulated in glioma groups compared with normal brain tissues group (P < 0.05), and the expression in grades III-IV was significantly higher than those in grades I-II (P < 0.05). Kaplan-Meier survival curve analysis showed high KLF11 expression tended to reduce the overall survival (P < 0.05). After univariate and multivariate analyses, KLF11 expression (P =0.003) and age (P =0.007) were independent prognostic factors for poor survival in glioma patients.

Conclusion

KLF11 expression was increased in glioma tissues, and high KLF11 expression was associated with poor prognosis. KLF11 expression was an independent prognostic factor for poor survival in glioma patients. KLF11 may serve as a novel prognostic marker for gliomas and as a novel treatment target.

ISG15 is downregulated by KLF12 and implicated in maintenance of cancer stem cell-like features in cisplatin-resistant ovarian cancer

Drug resistance is often developed during clinical chemotherapy of ovarian cancers. The ubiquitin‐like protein interferon‐stimulated gene 15 (ISG15) is possibly dependent on tumour context to promote or suppress progression of various tumours. The ubiquitin‐like protein interferon‐stimulated gene 15 (ISG15) was decreased in cisplatin‐resistant ovarian cancer cells. The current study identified that both ectopic wild type and nonISGylatable mutant ISG15 expression inhibited CSC‐like phenotypes of cisplatin‐resistant ovarian cancer cells. Moreover, ectopic ISG15 expression suppressed tumour formation in nude mice. In addition, ISG15 downregulation promoted CSC‐like features of cisplatin‐sensitive ovarian cancer cells. Furthermore, low ISG15 expression was associated with poor prognosis in patients with ovarian cancer. Transcriptional repressor Krüppel‐like factor 12 (KLF12) downregulated ISG15 in cisplatin‐resistant cells. Our data indicated that downregulating ISG15 expression, via weakening effect of KLF12, might be considered as new therapeutic strategy to inhibit CSC phenotypes in the treatment of cisplatin‐resistant ovarian cancer.

KLF7: a new candidate biomarker and therapeutic target for high-grade serous ovarian cancer

BACKGROUND

In spite of great progress in the surgical and clinical management, until now no significant improvement in overall survival of High-Grade Serous Ovarian Cancer (HGSOC) patients has been achieved. Important aspects for disease control remain unresolved, including unclear pathogenesis, high heterogeneity and relapse resistance after chemotherapy. Therefore, further research on molecular mechanisms involved in cancer progression are needed to find new targets for disease management. The Krüppel-like factors (KLFs) are a family of transcriptional regulators controlling several basic cellular processes, including proliferation, differentiation and migration. They have been shown to play a role in various cancer-relevant processes, in a context-dependent way.

METHODS

To investigate a possible role of KLF family members as prognostic biomarkers, we carried out a bioinformatic meta-analysis of ovarian transcriptome datasets in different cohorts of late-stage HGSOC patients. In vitro cellular models of HGSOC were used for functional studies exploring the role of KLF7 in disease development and progression. Finally, molecular modelling and virtual screening were performed to identify putative KLF7 inhibitors.

RESULTS

Bioinformatic analysis highlighted KLF7 as the most significant prognostic gene, among the 17 family members. Univariate and multivariate analyses identified KLF7 as an unfavourable prognostic marker for overall survival in late-stage TCGA-OV and GSE26712 HGSOC cohorts. Functional in vitro studies demonstrated that KLF7 can play a role as oncogene, driving tumour growth and dissemination. Mechanistic targets of KLF7 included genes involved in epithelial to mesenchymal transition, and in maintaining pluripotency and self-renewal characteristics of cancer stem cells. Finally, in silico analysis provided reliable information for drug-target interaction prediction.

CONCLUSIONS

Results from the present study provide the first evidence for an oncogenic role of KLF7 in HGSOC, suggesting it as a promising prognostic marker and therapeutic target.

Elevated KLF7 levels may serve as a prognostic signature and might contribute to progression of squamous carcinoma

Global efforts have been undertaken to define the genome-wide distribution of epigenetic markers in cancerous tissues, which provide an invaluable opportunity to understand cancer biology and identify predictive signatures. Several studies have focused on the gene expression patterns of squamous carcinoma to identify tumor subtypes and find prognostic and therapeutic targets because squamous carcinoma genomes showed high instability. However, the number of reliable reports referring prognostic significance of genes and their role in squamous carcinoma is still quite limited. Krüppel-like factor 7 (KLF7) is a transcription factor that is widely expressed in numerous human tissues at low levels. Members of the KLF family have established roles in tumor cell fate, stress response, cell survival and the tumor-initiating properties of cancer stem-like cells. Hence to investigate whether KFL7 expression from cancer tissue holds promise as a prognostic and/or therapeutic target, we analyzed gene expression profiles from squamous carcinoma and surgical margin tissues in The Cancer Genome Atlas. We identified significant up-regulation of KLF7 in squamous carcinoma, which was confirmed by immunohistochemical staining. Elevated KLF7 expression was associated with poor squamous carcinoma prognosis before and after correcting for confounding factors by multivariate Cox regression analysis. Several pathways, such as Neurotrophin and GnRH pathways, were activated in KLF7-up-regulated squamous carcinoma samples through Gene Set Enrichment Analysis. In conclusion, we consolidate the potential role(s) of KLF7 in squamous carcinoma carcinogenesis from The Cancer Genome Atlas surgical margin tissue, offering insights into expression signatures that are potentially useful for prognosis modalities.

Expression of human Krüppel-like factor 3 in peripheral blood as a promising biomarker for acute leukemia

Background

Universal gene targets are in persistent demand by real‐time quantitative polymerase chain reaction (RT‐qPCR)‐based methods in acute leukemia (AL) diagnosis and monitoring. Human Krüppel‐like factor 3 (hKLF3), a newly cloned human transcription factor, has proved to be a regulator of hematopoiesis.

Methods

Sanger sequencing was performed in bone marrow (BM) samples from 17 AL patients for mutations in hKLF3 coding exons. hKLF3 expression in peripheral blood (PB) and BM samples from 45 AL patients was dynamically detected by RT‐qPCR. PB samples from 31 healthy donors were tested as normal controls.

Results

No mutation was sequenced in hKLF3 coding exons. hKLF3 expression in PB of AL was significantly lower than that in healthy donors [0.30 (0.02‐1.07) vs 1.18 (0.62‐3.37), P < .0001]. Primary acute myeloid leukemia (AML) exhibited the least expression values compared with secondary AML and acute lymphoblastic leukemia. Receiver operating characteristic (ROC) analyses suggested that hKLF3 expression in PB was a good marker for AML diagnosis with an AUC of 0.99 (95% CI 0.98‐1.00) and an optimum cutoff value of 0.67 (sensitivity 93.94% and specificity 93.55%). hKLF3 expression was upregulated significantly when AML patients acquired morphological complete remission (CR), and the level of hKLF3 seemed to be higher in patients with deeper CR than in patients with minimal residual disease (MRD). Paired PB and BM samples showed highly consistent alteration in hKLF3 expression (r = .6533, P = .001). Besides, a significantly converse correlation between decreased hKLF3 expression in PB and markers for leukemic load was observed.

Conclusions

hKLF3 expression in PB may act as a potential marker for AL diagnosis and monitoring.

FBXW7 in Cancer: What Has Been Unraveled Thus Far?

: The FBXW7 (F-box with 7 tandem WD40) protein encoded by the gene FBXW7 is one of the crucial components of ubiquitin ligase called Skp1-Cullin1-F-box (SCF) complex that aids in the degradation of many oncoproteins via the ubiquitin-proteasome system (UPS) thus regulating cellular growth. FBXW7 is considered as a potent tumor suppressor as most of its target substrates can function as potential growth promoters, including c-Myc, Notch, cyclin E, c-JUN, and KLF5. Its regulators include p53, C/EBP-δ, Numb, microRNAs, Pin 1, Hes-5, BMI1, Ebp2. Mounting evidence has indicated the involvement of aberrant expression of FBXW7 for tumorigenesis. Moreover, numerous studies have also shown its role in cancer cell chemosensitization, thereby demonstrating the importance of FBXW7 in the development of curative cancer therapy. This comprehensive review emphasizes on the targets, functions, regulators and expression of FBXW7 in different cancers and its involvement in sensitizing cancer cells to chemotherapeutic drugs.

Cancer stem cells (CSCs), cervical CSCs and targeted therapies

Accumulating evidence has shown that cancer stem cells (CSCs) have a tumour-initiating capacity and play crucial roles in tumour metastasis, relapse and chemo/radio-resistance. As tumour propagation initiators, CSCs are considered to be promising targets for obtaining a better therapeutic outcome. Cervical carcinoma is the most common gynaecological malignancy and has a high cancer mortality rate among females. As a result, the investigation of cervical cancer stem cells (CCSCs) is of great value. However, the numbers of cancer cells and corresponding CSCs in malignancy are dynamically balanced, and CSCs may reside in the CSC niche, about which little is known to date. Therefore, due to their complicated molecular phenotypes and biological behaviours, it remains challenging to obtain “purified” CSCs and continuously culture CSCs for further in vitro studies without the cells losing their stem properties. At present, CSC-related markers and functional assays are used to purify, identify and therapeutically target CSCs both in vitro and in vivo. Nevertheless, CSC-related markers are not universal to all tumour types, although some markers may be valid in multiple tumour types. Additionally, functional identifications based on CSC-specific properties are usually limited in in vivo studies. Furthermore, an optimal method for identifying potential CCSCs in CCSC studies has not been previously published, and these techniques are currently of great importance. This article updates our knowledge on CSCs and CCSCs, reviews potential stem cell markers and functional assays for identifying CCSCs, and describes the potential of targeting CCSCs in the treatment of cervical carcinoma.