Single-cell RNA-seq reveals novel regulators of human embryonic stem cell differentiation to definitive endoderm

BACKGROUND

Human pluripotent stem cells offer the best available model to study the underlying cellular and molecular mechanisms of human embryonic lineage specification. However, it is not fully understood how individual stem cells exit the pluripotent state and transition towards their respective progenitor states.

RESULTS

Here, we analyze the transcriptomes of human embryonic stem cell-derived lineage-specific progenitors by single-cell RNA-sequencing (scRNA-seq). We identify a definitive endoderm (DE) transcriptomic signature that leads us to pinpoint a critical time window when DE differentiation is enhanced by hypoxia. The molecular mechanisms governing the emergence of DE are further examined by time course scRNA-seq experiments, employing two new statistical tools to identify stage-specific genes over time (SCPattern) and to reconstruct the differentiation trajectory from the pluripotent state through mesendoderm to DE (Wave-Crest). Importantly, presumptive DE cells can be detected during the transitory phase from Brachyury (T) (+) mesendoderm toward a CXCR4 (+) DE state. Novel regulators are identified within this time window and are functionally validated on a screening platform with a T-2A-EGFP knock-in reporter engineered by CRISPR/Cas9. Through loss-of-function and gain-of-function experiments, we demonstrate that KLF8 plays a pivotal role modulating mesendoderm to DE differentiation.

CONCLUSIONS

We report the analysis of 1776 cells by scRNA-seq covering distinct human embryonic stem cell-derived progenitor states. By reconstructing a differentiation trajectory at single-cell resolution, novel regulators of the mesendoderm transition to DE are elucidated and validated. Our strategy of combining single-cell analysis and genetic approaches can be applied to uncover novel regulators governing cell fate decisions in a variety of systems.

MiR-135a inhibits migration and invasion and regulates EMT-related marker genes by targeting KLF8 in lung cancer cells

Epithelial-mesenchymal transition (EMT) has been shown to be related to the pathogenesis of various diseases. Recently, microRNAs (miRNA) have been recognized as a new class of genes involved in human tumorigenesis. In this study, we found that the expression levels of miR-135a were dramatically decreased in NSCLC cell lines and clinical NSCLC tissue samples. Then, we demonstrated that miR-135a significantly suppressed the migration and invasion of lung cancer cells in vitro, suggesting that miR-135a may be a novel tumor suppressor. Further studies revealed that the transcription factor KLF8 was a target gene of miR-135a in NSCLC cells, as miR-135a bound directly to the 3'-untranslated region (3'-UTR) of KLF8, thus reducing both the expression of KLF8 at the mRNA and protein levels. In addition, the EMT marker E-cadherin or vimentin was also down-regulated or up-regulated on miR-135a treatment. Moreover, silencing KLF8 was able to inhibit the migration and invasion of lung cancer cells. In conclusion, these findings indicate that miR-135a suppresses the migration and invasion of NSCLC cells through targeting KLF8, which is involved in the EMT process. This finding provides new insight into the mechanism of NSCLC progression.

KLF8 is associated with poor prognosis and regulates glycolysis by targeting GLUT4 in gastric cancer

Krüppel‐like transcription factor (KLF) family is involved in tumorigenesis in different types of cancer. However, the importance of KLF family in gastric cancer is unclear. Here, we examined KLF gene expression in five paired liver metastases and primary gastric cancer tissues by RT‐PCR, and immunohistochemistry was used to study KLF8 expression in 206 gastric cancer samples. The impact of KLF8 expression on glycolysis, an altered energy metabolism that characterizes cancer cells, was evaluated. KLF8 showed the highest up‐regulation in liver metastases compared with primary tumours among all KLF members. Higher KLF8 expression associated with larger tumour size (P < 0.001), advanced T stage (P = 0.003) and N stage (P < 0.001). High KLF8 expression implied shorter survival outcome in both TCGA and validation cohort (P < 0.05). Silencing KLF8 expression impaired the glycolysis rate of gastric cancer cells in vitro. Moreover, high KLF8 expression positively associated with SUVmax in patient samples. KLF8 activated the GLUT4 promoter activity in a dose‐dependent manner (P < 0.05). Importantly, KLF8 and GLUT4 showed consistent expression patterns in gastric cancer tissues. These findings suggest that KLF8 modulates glycolysis by targeting GLUT4 and could serve as a novel biomarker for survival and potential therapeutic target in gastric cancer.

Circ_0067934 promotes non-small cell lung cancer development by regulating miR-1182/KLF8 axis and activating Wnt/β-catenin pathway

Non-small cell lung cancer (NSCLC) is the primary subtype of lung cancer with high mortality. Circular RNAs (circRNAs) play a crucial role in tumor development and progression. This study aimed to explore the function of circ_0067934 in NSCLC progression and its molecular basis. The levels of circ_0067934, miR-1182 and kruppel like factor 8 (KLF8) were measured by quantitative real-time polymerase chain reaction or western blot assay. Cell viability was detected by Cell Counting Kit-8 (CCK-8) assay. Cell migration and invasion were assessed by transwell assay. Cell apoptosis was monitored by flow cytometry. The protein levels of epithelial-to-mesenchymal transition (EMT)-related markers and Wnt/β-catenin pathway-related proteins were examined by western blot. Dual-luciferase reporter assay, RNA Immunoprecipitation (RIP) assay or RNA pull-down assay was performed to verify the interaction among circ_0067934, miR-1182 and KLF8. Xenograft assay was used to detect tumor growth in vivo. We found that circ_0067934 and KLF8 were up-regulated, while miR-1182 was down-regulated in NSCLC tissues and cells. Circ_0067934 knockdown blocked proliferation, migration, invasion and EMT and induced apoptosis in NSCLC cells. Circ_0067934 regulated NSCLC progression by sponging miR-1182. MiR-1182 targeted KLF8 to hinder NSCLC development. In addition, depletion of circ_0067934 restrained tumor growth in vivo. In conclusion, Circ_0067934 acted as a competing endogenous RNA to facilitate NSCLC progression by regulating the miR-1182/KLF8 axis and activating Wnt/β-catenin pathway.

KLF8 promotes tumorigenesis, invasion and metastasis of colorectal cancer cells by transcriptional activation of FHL2

The transcription factor Krüppel-like factor (KLF)8 plays an important role in the formation of several human tumors, including colorectal cancer. We recently identified four-and-a-half LIM protein 2 (FHL2) as a critical inducer of the epithelial-to-mesenchymal transition (EMT) and invasion. However, the molecular mechanism by which KLF8 affects FHL2-mediated tumor proliferation, EMT and metastasis remains unknown. Here, we showed that KLF8 overexpression promoted EMT and metastatic phenotypes. KLF8 expression was stimulated by transforming growth factor (TGF)-β1. Moreover, KLF8 acted as a potential EMT inducer by stimulating vimentin expression and inducing a loss of E-cadherin in stable KLF8-transfected cells. KLF8 overexpression induced a strong increase in FHL2 expression, and a positive correlation between the expression patterns of KLF8 and FHL2 was observed in CRC cells. Promoter reporter and chromatin immunoprecipitation (ChIP) assays demonstrated that KLF8 directly bound to and activated the human FHL2 gene promoter. However, siRNA-mediated repression of FHL2 in KLF8-overexpressing cells reversed the EMT and the proliferative and metastatic phenotypes. In vivo, KLF8 promoted FHL2-mediated proliferation and metastasis via orthotopic implantation. Taken together, this work identified KLF8-induced FHL2 activation as a novel and critical signaling mechanism underlying human breast/colorectal cancer invasion and metastasis.

LncRNA DANCR promotes the proliferation, migration, and invasion of tongue squamous cell carcinoma cells through miR-135a-5p/KLF8 axis

Background

Tongue squamous cell carcinoma (TSCC) is a most invasive cancer with high mortality and poor prognosis. It is reported that lncRNA DANCR has implications in multiple types of cancers. However, its biological role and underlying mechanism in TSCC progress are not well elucidated.

Methods

Our present study first investigated the function of DANCR on the proliferation, migration and invasion of TSCC cells by silencing or overexpressing DANCR. Further, the miR-135a-5p-Kruppel-like Factor 8 (KLF8) axis was focused on to explore the regulatory mechanism of DANCR on TSCC cell malignant phenotypes. Xenografted tumor growth using nude mice was performed to examine the role of DANCR in vivo.

Results

DANCR knockdown reduced the viability and inhibited the migration and invasion of TSCC cells in vitro, while ectopic expression of DANCR induced opposite effects. In vivo, the tumor growth and the expression of matrix metalloproteinase (MMP)-2/9 and KLF8 were also blocked by DANCR inhibition. In addition, we found that miR-135-5p directly targeted DANCR, which was negatively correlated with DANCR on TSCC progression. Its inhibition reversed the beneficial effects of DANCR silence on TSCC malignancies. Furthermore, the expression of KLF8 evidently altered by both DANCR and miR-135a-5p. Silencing KLF8 using its specific siRNA showed that KLF8 was responsible for the induction of miR-135a-5p inhibitor on TSCC cell malignancies and MMP-2/9 expression.

Conclusions

These findings, for the first time, suggest that DANCR plays an oncogenic role in TSCC progression via targeting miR-135a-5p/KLF8 axis, which provides a promising biomarker and treatment approach for preventing TSCC.

Downregulated Krüppel-like factor 8 is involved in decreased trophoblast invasion under hypoxia-reoxygenation conditions

Krüppel-like factor 8 (KLF8) is a pivotal transcription factor expressed in the human placenta that can regulate cell invasion. The objective of this study was to assess whether a hypoxia-reoxygenation (H/R) environment affects placental KLF8 expression levels and subcellular localization and to evaluate the relationship between KLF8 levels and trophoblast invasion activity. Human first trimester villous tissues from normal pregnancies and third trimester placentas from pregnancies with or without preeclampsia (PE) were used for the detection of KLF8 expression and correlating its levels with metalloproteinase 9 (MMP-9) expression. In addition, HTR8/SVneo cells were used to mimic the effects of an H/R environment on placentas to study KLF8 expression and trophoblast invasion. The KLF8 levels, MMP-9 levels, and trophoblast invasion were similarly altered; the levels peaked at 8 to 10 weeks of gestation and declined thereafter along with oxygen tension increased from hypoxia to normoxia during early pregnancy, decreased in third trimester placentas from PE pregnancies featured by repeated H/R and HTR8/SVneo cells exposed to H/R compared with the control. Moreover, a visible reduction in KLF8 immunoreactivity was present in the nuclei of cytotrophoblast cells in human villous tissues at 11 weeks, and partial cytoplasmic accumulation of KLF8 was observed in HTR8/SVneo cells treated with H/R. In conclusion, these findings strongly suggest that H/R reduces the expression and nuclear localization of KLF8 to inhibit the trophoblast invasion by downregulating MMP-9 levels. The KLF8 may play a vital role in the pathogenesis of PE as a novel oxygen tension sensor.

Serum aberrant expression of miR-24-3p and its diagnostic value in Alzheimer's disease

Aim: This study aimed to evaluate the effect of miR-24-3p in Alzheimer's disease (AD). Materials & methods: A total of 198 participants were recruited in this study, including 104 AD patients and 94 healthy controls. Expression of miR-24-3p was detected using quantitative real-time PCR. Receiver-operating characteristic curve was used to assess the diagnostic value of miR-24-3p. In vitro AD model was established to evaluate the effect of miR-24-3p. The downstream target was detected by luciferase reporter gene assay. Results: Expression of miR-24-3p showed 1.6-fold increase in AD group compared with healthy controls, and a negative correlation of miR-24-3p with mini-mental state examination score was obtained. Receiver-operating characteristic curve showed satisfactory diagnostic accuracy. Downregulation of miR-24-3p promoted cell proliferation and inhibited cell apoptosis. KLF8 is a target gene of miR-24-3p. Conclusion: MiR-24-3p has a certain value in the diagnosis of AD and may be a potential biomarker.

The lncRNA ELF3-AS1 promotes bladder cancer progression by interaction with Krüppel-like factor 8

Accumulating evidence has shown the critical role of long non-coding RNAs (lncRNAs) during cancer progression. However, the involvement of ELF3-AS1 in bladder cancer (BC) remains largely unclear. By lncRNA profiling, we identified ELF3-AS1 as a novel oncogenic lncRNA during bladder cancer development. ELF3-AS1 was highly expressed in bladder cancer and correlated with poor prognosis. ELF3-AS1 could increase viability and migration of bladder cancer cells in vitro and promoted xenograft tumor growth in vivo. Furthermore, ELF3-AS1 could interact with KLF8 to stabilize KLF8 by protecting it from proteasome-mediated degradation. KLF8 in turn could bind ELF3-AS1 promoter and transactivate ELF3-AS1 expression. The positive feedback loop between ELF3-AS1 and KLF8 enhanced KLF8 signaling by increasing MMP9 expression. Collectively, our study has unraveled a novel mechanism of ELF3-AS1-mediated oncogenesis in bladder cancer by reinforcement of ELF3-AS1/KLF8 signaling with potential implications for therapeutic intervention.

Identification of epidermal growth factor receptor and its inhibitory microRNA141 as novel targets of Krüppel-like factor 8 in breast cancer

Krüppel-like factor 8 (KLF8) is a dual transcriptional factor critical for breast cancer progression. Epidermal growth factor receptor (EGFR) is frequently overexpressed in aggressive such as triple-negative breast cancer and associated with poor clinical outcomes. Here we report a novel KLF8-EGFR signaling axis in breast cancer. We identified a highly correlated co-overexpression between KLF8 and EGFR in invasive breast cancer cells and patient tumor samples. Overexpression of KLF8 in the non-tumorigenic MCF-10A cells induced the expression of EGFR, whereas knockdown of KLF8 from the MDA-MB-231 cells decreased it. Promoter activation and binding assays indicated that KLF8 promotes the EGFR expression by directly binding its gene promoter. We also revealed that KLF8 directly represses the promoter of miR141 and miR141 targets the 3′-untranslational region of EGFR transcript to inhibit EGFR translation. Treatment with the EGFR inhibitor AG1478 or overexpression of miR141 blocked the activity of ERK downstream of EGFR and inhibited KLF8-depndent cell invasiveness, proliferation and viability in cell culture and invasive growth and lung metastasis in nude mice. Conversely, overexpression of an inhibitory sponge of miR141 led to the opposite phenotypes. Taken together, these findings demonstrate a novel KLF8 to miR141/EGFR signaling pathway potentially crucial for breast cancer malignancy.

Krüppel-like factor 8 activates the transcription of C-X-C cytokine receptor type 4 to promote breast cancer cell invasion, transendothelial migration and metastasis

Krüppel-like factor 8 (KLF8) has been strongly implicated in breast cancer metastasis. However, the underlying mechanisms remain largely unknown. Here we report a novel signaling from KLF8 to C-X-C cytokine receptor type 4 (CXCR4) in breast cancer. Overexpression of KLF8 in MCF-10A cells induced CXCR4 expression at both mRNA and protein levels, as determined by quantitative real-time PCR and immunoblotting. This induction was well correlated with increased Boyden chamber migration, matrigel invasion and transendothelial migration (TEM) of the cells towards the ligand CXCL12. On the other hand, knockdown of KLF8 in MDA-MB-231 cells reduced CXCR4 expression associated with decreased cell migration, invasion and TEM towards CXCL12. Histological and database mining analyses of independent cohorts of patient tissue microarrays revealed a correlation of aberrant co-elevation of KLF8 and CXCR4 with metastatic potential. Promoter analysis indicated that KLF8 directly binds and activates the human CXCR4 gene promoter. Interestingly, a CXCR4-dependent activation of focal adhesion kinase (FAK), a known upregulator of KLF8, was highly induced by CXCL12 treatment in KLF8-overexpressing, but not KLF8 deficient cells. This activation of FAK in turn induced a further increase in KLF8 expression. Xenograft studies showed that overexpression of CXCR4, but not a dominant-negative mutant of it, in the MDA-MB-231 cells prevented the invasive growth of primary tumor and lung metastasis from inhibition by knockdown of KLF8. These results collectively suggest a critical role for a previously unidentified feed-forward signaling wheel made of KLF8, CXCR4 and FAK in promoting breast cancer metastasis and shed new light on potentially more effective anti-cancer strategies.

CircRNA PVT1 promotes proliferation and chemoresistance of osteosarcoma cells via the miR-24-3p/KLF8 axis

OBJECTIVE

To investigate the regulatory effect and mechanism of circular RNA PVT1 (circPVT1) in proliferation and chemoresistance of osteosarcoma (OS) cells.

METHODS

The expression of circPVT1 in human OS and adjacent normal tissues was detected. The correlation between circPVT1 expression and clinical features of OS was analyzed. The expressions of circPVT1 and miR-24-3p in OS cells resistant to cisplatin, doxorubicin or methotrexate and parental OS cells were detected after cell transfection. CCK-8 and colony formation assay assessed the viability and proliferative ability of OS cells. qRT-PCR and Western blotting measured the expression of KLF8. Dual-luciferase reporter and RNA pull-down assays verified the targeting relationships of circPVT1/miR-24-3p and miR-24-3p/KLF8.

RESULTS

CircPVT1 was over-expressed in OS tissues and cells, and correlated with clinical features of OS. Over-expressed circPVT1 reduced the survival of OS patients. CircPVT1 was up-regulated in chemoresistant OS cells compared to their parental cells. CircPVT1 inhibition suppressed the proliferation and chemoresistance of OS cells. MiR-24-3p was under-expressed in OS cells and further down-regulated in chemoresistant cells. CircPVT1 could bind and down-regulate miR-24-3p. MiR-24-3p overexpression inhibited the proliferation and chemoresistance of OS cells. KLF8 was over-expressed in OS cells and further up-regulated in chemoresistant cells. MiR-24-3p negatively regulated the expression of KLF8.

CONCLUSION

CircPVT1 mediates proliferation and chemoresistance of OS cells via the miR-24-3p/KLF8 axis. The findings may provide guidance for clinical treatment of OS.

KLF8 overexpression promotes the growth of human lung cancer cells by promoting the expression of JMJD2A

Background

Non-small-cell lung cancer (lung cancer) has become one of the leading causes worldwide and the underlying mechanism is not fully understood. The transcriptional factor Kruppel like factor 8 (KLF8) is involved in the initiation, progression, transformation, and metastasis of diverse cancers. However, the roles of KLF8 in human non-small cell lung cancer remain unknown.

Methods

CCK-8 kit and colony formation assay were performed to determine the cell growth of lung cancer cells. Flow cytometry analysis was used to evaluate apoptosis and cell cycle of lung cancer cells. Luciferase reporter assay was used to examine the activation of JMJD2A promoter by KLF8. Chromatin immunoprecipitation assay was performed to evaluate the binding of KLF8 to JMJD2A promoter. Western blot and polymerase chain reaction were applied to analyze the expression of interested genes.

Results

The mRNA and protein levels of KLF8 in human non-small cell lung cancer tissues were overexpressed compared with the non-cancer tissues. KLF8 was knocked down with lentivirus-mediated short-hairpin RNA (shRNA) in human lung cancer cells (A549 and H1299 cells). The phenotypic results showed that KLF8 knockdown decreased the proliferation rate and colony formation of lung cancer cells. By contrast, lentivirus-mediated KLF8 overexpression promoted the growth of lung cancer cells (A549 and H1299 cells) and non-cancerous bronchial epithelial cell line BEAS-2B. Next, we showed that KLF8 regulated cell cycle at the G0 phase but not regulates cellular apoptosis of lung cancer cells. KLF8 regulated the expression of the cell cycle regulators P21 and CDK4 in a JMJD2A-dependent manner and JMJD2A knockdown significantly blocked the functions of KLF8 in regulating cell cycle and proliferation of lung cancer cells. Finally, we observed that KLF8 bound the promoter of JMJD2A and facilitated the expression of JMJD2A.

Conclusions

Our evidence demonstrated that KLF8 upregulation in human lung cancer promotes the cell proliferation and colony formation of lung cancer cells. KLF8 binds to the promoter of JMJD2A and subsequently regulates the expression of P21 and CDK4, which contributes to the regulation of cell cycle by KLF8. KLF8 may serve as a target for the treatment of human lung cancer.

KLF8 is activated by TGF-β1 via Smad2 and contributes to ovarian cancer progression

Krüppel-like factor 8 (KLF8) is a transcription factor expressed abnormally in various cancer types and promotes oncogenic transformation. However, the role of KLF8 in ovarian cancer (OC) progression remains unclear. This study reports that transforming growth factor-β1 (TGF-β1)/Smad2/KLF8 axis regulates epithelial-mesenchymal transition (EMT) and contributes to OC progression. We analyzed the KLF8 expression in OC cells and tissues, wherein a significant overexpression of KLF8 was observed. Increased KLF8 expressions were correlated with higher cell proliferation, EMT, migration, and invasion and conferred poor clinical outcomes in OC patients. Overexpressed KLF8 increases F-actin polymerization and induces cytoskeleton remodeling of OC cells. Furthermore, a dissection of the molecular mechanism defined that TGF-β1 triggers KLF8 through the Smad2 pathway and regulates EMT. Pharmacological and genetic inhibition of Smad2 followed by TGF-β1 treatment failed to activate KLF8 expression and induction of EMT. Using promoter-luciferase reporter assays, we defined that upon TGF-β1 activation, phosphorylated Smad2 binds and promotes the KLF8 promoter activity, and knockdown of Smad2 inhibits KLF8 promoter activation. Together, these results demonstrate that TGF-β1 activates KLF8 expression by the Smad2 pathway, and KLF8 contributes to OC progression and may serve as a potential therapeutic strategy for treating OC patients.

KLF8 is required for bladder cancer cell proliferation and migration

Krüppel-like factor 8 (KLF8) belongs to the Sp/KLF family of transcription factors. Recently, it is affirmed that KLF8 plays an important role in the regulation of epithelial-mesenchymal transition, which is a key process that occurs during cancer metastasis. Although the overexpression of KLF8 has been observed in several types of human cancers, the functional role of KLF8 in human bladder cancer remains unknown. Here, we investigated the effects of KLF8 knockdown on bladder cancer cell proliferation and migration in vitro. Lentivirus-mediated small interfering RNA (siRNA) targeting KLF8 specifically downregulated its expression in T24 and BT5637 bladder cancer cells. Knockdown of KLF8 significantly inhibit cell proliferation and colony formation. Cell cycle analysis showed that knockdown of KLF8 arrested T24 cells in the G0/G1 phase. Moreover, cell migration was attenuated in T24 cells after KLF8 knockdown. Furthermore, knockdown of KLF8 resulted in a reduction in vimentin and N-cadherin expression and an increase in β-catenin expression. These results indicate that KLF8 plays a crucial role in proliferation and migration of bladder cancer cells, and inhibition of KLF8 by siRNA may provide a potential therapeutic approach for gene therapy in bladder cancer.

miR-10a-5p Inhibits the Differentiation of Goat Intramuscular Preadipocytes by Targeting KLF8 in Goats

Intramuscular fat contributes to the improvement of meat quality of goats. MicroRNAs (miRNAs) have been reported to regulate adipocyte differentiation and maturation. The aim of our study was to clarify whether miR-10a-5p regulates goat intramuscular preadipocyte (GIPC) differentiation and its direct downstream signaling pathway. GIPCs were isolated from longissimus dorsi, whose miR-10a-5p level was measured at different time point of differentiation induction. Adipogenic differentiation of the GIPCs was evaluated by Oil Red O and BODIPY staining, and the expression changes of adipogenic genes like ACC, ATGL, CEBPβ, PPARγ, etc. Related mechanisms were verified by qPCR, a bioinformatic analysis, a dual-luciferase reporter assay, overexpression, and siRNA transfection. Oil Red O and BODIPY staining both with adipogenic gene detection showed that miR-10a-5p suppressed the accumulation of lipid droplets in GIPCs and inhibited its differentiation. The dual-luciferase reporter assay experiment revealed that miR-10a-5p regulates GIPC differentiation by directly binding to KLF8 3’UTR to regulate its expression. Thus, the results indicated that miR-10a-5p inhibits GIPC differentiation by targeting KLF8 and supply a new target for fat deposition and meat quality improvement.

Kruppel-like factor 8 regulates triple negative breast cancer stem cell-like activity

Introduction

Breast tumor development is regulated by a sub-population of breast cancer cells, termed cancer stem-like cells (CSC), which are capable of self-renewing and differentiating, and are involved in promoting breast cancer invasion, metastasis, drug resistance and relapse. CSCs are highly adaptable, capable of reprogramming their own metabolism and signaling activity in response to stimuli within the tumor microenvironment. Recently, the nutrient sensor O-GlcNAc transferase (OGT) and O-GlcNAcylation was shown to be enriched in CSC populations, where it promotes the stemness and tumorigenesis of breast cancer cells in vitro and in vivo. This enrichment was associated with upregulation of the transcription factor Kruppel-like-factor 8 (KLF8) suggesting a potential role of KLF8 in regulating CSCs properties.

Methods

Triple-negative breast cancer cells were genetically modified to generate KLF8 overexpressing or KLF8 knock-down cells. Cancer cells, control or with altered KLF8 expression were analyzed to assess mammosphere formation efficiency, CSCs frequency and expression of CSCs factors. Tumor growth in vivo of control or KLF8 knock-down cells was assessed by fat-pad injection of these cell in immunocompromised mice.

Results

Here, we show that KLF8 is required and sufficient for regulating CSC phenotypes and regulating transcription factors SOX2, NANOG, OCT4 and c-MYC. KLF8 levels are associated with chemoresistance in triple negative breast cancer patients and overexpression in breast cancer cells increased paclitaxel resistance. KLF8 and OGT co-regulate each other to form a feed-forward loop to promote CSCs phenotype and mammosphere formation of breast cancer cells.

Discussion

These results suggest a critical role of KLF8 and OGT in promoting CSCs and cancer progression, that may serve as potential targets for developing strategy to target CSCs specifically.

CircSAMD4A contributes to cell doxorubicin resistance in osteosarcoma by regulating the miR-218-5p/KLF8 axis

Circular RNA sterile alpha motif domain containing 4A (circSAMD4A) was found to be differentially expressed in osteosarcoma and contributed to the tumorigenesis of osteosarcoma. However, the role of circSAMD4A in doxorubicin (DXR) resistance of osteosarcoma is yet to be elucidated. Levels of circSAMD4A, microRNA (miR)-218-5p and Krüppel-like factor 8 (KLF8) were detected using quantitative reverse transcription-polymerase chain reaction. Western blot was applied to detect the protein levels of KLF8, cyclin D1 and p21. Cell viability, cell cycle, migration and invasion were analyzed using Cell Counting Kit-8 assay, flow cytometry and transwell assay, respectively. The interaction between miR-218-5p and circSAMD4A or KLF8 was verified using dual-luciferase reporter assay or RNA immunoprecipitation assay. In vivo experiments were performed using murine xenograft models. CircSAMD4A and KLF8 were elevated in osteosarcoma, and knockdown of circSAMD4A or KLF8 sensitized osteosarcoma cells to DXR by mediating resistant cell viability, migration and invasion inhibition, and cell cycle arrest in vitro. miR-218-5p was decreased in osteosarcoma, and miR-218-5p inhibition enhanced DXR resistance. Besides, miR-218-5p was found to bind to circSAMD4A or KLF8, and subsequent rescue experiments indicated that miR-218-5p inhibition reversed the inhibitory effects of circSAMD4A silencing on DXR resistance, and silencing miR-218-5p enhanced DXR resistance by targeting KLF8 in osteosarcoma cells. Moreover, circSAMD4A could indirectly regulate KLF8 via miR-218-5p. Additionally, circSAMD4A knockdown enhanced the cytotoxicity of DXR in osteosarcoma in vivo via regulating miR-218-5p and KLF8. In all, circSAMD4A enhanced cell DXR resistance in osteosarcoma by regulating the miR-218-5p/KLF8 axis, suggesting a novel therapeutic target for therapy-resistant osteosarcoma.

The role of Krüppel-like factor 8 in cancer biology: Current research and its clinical relevance

Cancer is one of the leading causes of mortality worldwide, ranked second after heart disease. Despite recent advancements in diagnosis and treatment, there are still numerous problems associated with cancer progression, disease recurrence, and therapeutic resistance that are partially explored. Several studies have recently revealed that Krüppel-like factor 8 (KLF8) regulates transcription of genes linked with diverse biological processes, including proliferation, epithelial to mesenchymal transition (EMT), migration, invasion, and inflammation. KLF8 is expressed ubiquitously in mammalian cells, and its aberrant expression has been manifested with several cancer types. Earlier studies demonstrated the crucial role of KLF8 in DNA repair and resistance to apoptosis in numerous cancer types. Hence, studying the function of KLF8 from the perspective of cancer progression and therapy resistance would help develop a new therapeutic avenue. In this review, we summarize the clinical relevance of KLF8 expression in various malignancies, focusing on recent updates in EMT, cellular signaling, and cancer stem cells. We also address the contribution of KLF8 in development, DNA repair, chemoresistance, and its clinical utility as a predictive biomarker.

A novel role of Krüppel-like factor 8 as an apoptosis repressor in hepatocellular carcinoma

Background

Krüppel-like factor 8 (KLF8), a cancer-promoting factor that regulates critical gene transcription and cellular cancer-related events, has been implicated in tumor development and progression. However, the functional role of KLF8 in the pathogenesis of hepatocellular carcinoma (HCC) remains largely unknown.

Methods

The gene expression patterns and genome-wide regulatory profiles of HCC cells after KLF8 knockout were analyzed by using RNA sequencing (RNA-seq) and chromatin immunoprecipitation sequencing (ChIP-seq) of histone H3 lysine 27 acetylation (H3K27ac) combined with bioinformatics analysis. Transcription factor-binding motifs that recognized by KLF8 were evaluated by motif analysis. For the predicted target genes, transcriptional changes were examined by ChIP, and loss of function experiments were conducted by siRNA transfection.

Results

KLF8 functioned as a transcription repressor in HCC and mainly regulated apoptotic-related genes directly. A total of 1,816 differentially expressed genes after KLF8 knockout were identified and significantly corresponded to global changes in H3K27ac status. Furthermore, two predicted target genes, high-mobility group AT-hook 2 (HMGA2) and matrix metalloproteinase 7 (MMP7), were identified as important participants in KLF8-mediated anti-apoptotic effect in HCC. Knockout of KLF8 enhanced cell apoptosis process and caused increase in the associated H3K27ac, whereas suppression HMGA2 or MMP7 attenuated these biological effects.

Conclusions

Our work suggests a novel role and mechanism for KLF8 in the regulation of cell apoptosis in HCC and facilitates the discovery of potential therapeutic targets for HCC treatment.

CircSEC24A induces KLF8 expression to promote the malignant progression of non-small cell lung cancer by regulating miR-1253

OBJECTIVES

This study aimed to analyze the role of circSEC24A in non-small cell lung cancer (NSCLC) and its underlying mechanism.

METHODS

RNA levels of circSEC24A, microRNA-1253 (miR-1253), and KLF transcription factor 8 (KLF8) were detected by quantitative real-time polymerase chain reaction. Protein expression was analyzed by western blot or immunohistochemistry assay. Cell proliferation and apoptosis were investigated by colony formation assay, 5-ethynyl-2'-deoxyuridine assay, and flow cytometry analysis. Glycolysis was evaluated by commercial kits. Dual-luciferase reporter assay and RNA immunoprecipitation assay were conducted to identify the associations among circSEC24A, miR-1253, and KLF8. Xenograft mouse model assay was used to evaluate the effect of circSEC24A on tumor tumorigenesis.

RESULTS

CircSEC24A and KLF8 were upregulated, while miR-1253 was downregulated in NSCLC. CircSEC24A knockdown inhibited proliferation and glycolysis but induced the apoptosis of NSCLC cells. CircSEC24A acted as a miR-1253 sponge and regulated NSCLC cell malignancy by targeting miR-1253. KLF8 was identified as a target of miR-1253, and its overexpression attenuated miR-1253-induced effects in NSCLC cells. Besides, circSEC24A upregulated KLF8 by sponging miR-1253. Further, circSEC24A knockdown suppressed NSCLC cell tumorigenesis in vivo.

CONCLUSIONS

CircSEC24A silencing inhibited NSCLC cell malignancy through the miR-1253/KLF8 pathway, providing a potential therapeutic target for NSCLC.

Role of krüppel-like factor 8 for therapeutic drug-resistant multi-organ metastasis of breast cancer

Metastasis and drug resistance are intertwined processes that are responsible for the vast majority of patient deaths from breast cancer. The underlying mechanisms remain incompletely understood. We previously demonstrated that KLF8 activates CXCR4 transcription in metastatic breast cancer. Here, we report a novel role of KLF8-CXCR4 signaling for converting single organ metastasis into multiple organ metastasis associated with chemotherapeutic resistance. We show that KLF8 expression in metastatic breast cancer cells can be over-induced by chemotherapeutic drugs. Analysis of data from large-cohorts of patients indicates that post-chemotherapy there is a close correlation between the aberrant high levels of KLF8 and CXCR4 and that this correlation is well associated with drug resistance, metastasis, and poor prognosis. To mimic their aberrant high levels, we overexpressed KLF8 or CXCR4 in a human breast cancer cell line known to metastasize only to the lungs after intravenous injection in nude mice. As expected, these cells become more resistant to chemotherapeutic drugs. Surprisingly, these KLF8 or CXCR4 overexpressing cells, even implanted orthotopically, metastasized extensively to multiple organs particularly the CXCL12-rich organs. Tube formation assay, Ki67 staining and Western blotting revealed that KLF8 or CXCR4 overexpression enhanced angiogenesis involving increased expression and secretion of VEGF protein. We also found that KLF8 or CXCR4 overexpression strongly enhanced formation of filopodium-like protrusions and proliferation via CXCR4 stimulation in a 3D culture model mimicking the colonization step of metastasis. Taken together, these results suggest that the chemo-induction of KLF8 upregulation be critical for drug resistance and systemic metastasis through enhanced tumor angiogenesis and colonization via CXCR4 over-activation and that KLF8-CXCR4 signaling axis may be a new therapeutic target for drug-resistant breast cancer metastasis.

Regulation of Krüppel-like factor 8 by the NEDD4 E3 ubiquitin ligase

Krüppel-like factor 8 (KLF8) plays many important roles in various diseases, especially cancer. Previous studies have shown that KLF8 is regulated by ubiquitylation. The molecular mechanism underlying this posttranslational modification of KLF8, however, has not been investigated. Reported here is our identification of the neural precursor cell expressed, developmentally down-regulated 4 (NEDD4) as the E3 ubiquitin ligase for this modification. By co-immunoprecipitation and ubiquitylation assays, we determined that KLF8 interacts with NEDD4 and is ubiquitylated by NEDD4. By site-directed mutagenesis and pharmacological inhibition of MEK, we found that the ubiquitylation of KLF8 by NEDD4 depends upon the phosphorylation of KLF8 at serine 48 by ERK. Cycloheximide chase analysis, target gene promoter reporter assay and fluorescent staining indicated that NEDD4 plays a critical role in promoting the stability and transcriptional activity of KLF8 in the nucleus. Taken together, this work identified NEDD4 as a novel E3 ubiquitin ligase for KLF8 that provides insights into targeting the KLF8-NEDD4 axis to treat various types of cancer associated with overexpression of both proteins.

ERK2 phosphorylates Krüppel-like factor 8 protein at serine 48 to maintain its stability

Krüppel-like factor 8 (KLF8) plays important roles in cancer and is strictly regulated by various post-translational modifications such as sumoylation, acetylation, ubiquitylation and PARylation. Here we report a novel phosphorylation of KLF8 by ERK2 responsible and critical for the stability of KLF8 protein. The full-length KLF8 protein displays a doublet in SDS-PAGE gel. The upper band of the doublet, however, disappeared when the N-terminal 50 amino acids were deleted. In its full-length the upper band disappeared upon phosphatase treatment or mutation of the serine 48 (S48) to alanine whereas the lower band was lost when the S48 was mutated to aspartic acid that mimics phosphorylated S48. These results suggest that S48 phosphorylation is responsible for the motility up-shift of KLF8 protein. Pharmacological and genetic manipulations of various potential kinases identified ERK2 as the likely one that phosphorylates KLF8 at S48. Functional studies indicated that this phosphorylation is crucial for protecting KLF8 protein from degradation in the nucleus and promoting cell migration. Taken together, this study identifies a novel mechanism of phosphorylation critical for KLF8 protein stabilization and function.

KLF8 Promotes the Survival of Lung Adenocarcinoma During Nutrient Deprivation by Regulating the Pentose Phosphate Pathway through SIRT2

BACKGROUND

The pentose phosphate pathway (PPP) is a critical metabolic pathway that generates NADPH and ribose-5-phosphate for nucleotide biosynthesis and redox homeostasis. In this study, we investigated a potential regulatory role for Krüppel-like factor 8 (KLF8) in the control of PPP in lung adenocarcinoma (LUAD) cells.

METHODS

Based on a comprehensive set of experimental approaches, including cell culture, molecular techniques, and functional assays, we revealed a novel mechanism by which KLF8 promotes the activation of glucose-6-phosphate dehydrogenase (G6PD), a component enzyme in the PPP.

RESULTS

Our findings demonstrate that KLF8 inhibits the acetylation of G6PD, leading to its increased enzymatic activity. Additionally, we observed that KLF8 activates the transcription of SIRT2, which has been implicated in regulating G6PD acetylation. These results highlight the interplay between KLF8, G6PD, and protein acetylation in the regulation of PPP in LUAD.

CONCLUSIONS

Understanding the intricate molecular mechanisms underlying the metabolic reprogramming driven by KLF8 in lung cancer provides valuable insights into potential therapeutic strategies targeting the PPP. This study emphasizes the significance of KLF8 as a key modulator of metabolic pathways and indicates the potential of targeting the KLF8-G6PD axis for lung cancer treatment.