PPAR-γ Ligand Inhibits Nasopharyngeal Carcinoma Cell Proliferation and Metastasis by Regulating E2F2

Thiazolidinedione-based structure modification of ergosterol peroxide provides thiazolidinedione-conjugated derivatives as potent agents against breast cancer cells through a PI3K/AKT/mTOR pathway

Ergosterol peroxide (EP) is a steroidal compound isolated from the traditional Chinese medicine Ganoderma lucidum. However, EP is limited by its solubility and moderate potency in antitumor studies. In the present study, a series of novel ergosterol peroxide-3-thiazolidinedione derivatives were designed and synthesized, by changing the linker between ergosterol peroxide and thiazolidinedione, it is expected to obtain compounds with better antitumor activity. The cytotoxicity screening showed that compound 13o is the most active derivative against the MCF-7 cell line with an IC50 of 3.06 μM, and exhibited stronger antitumor activity compared to the parent EP. Further in vitro and vivo studies showed that compound 13o may reduced the mitochondrial membrane potential, increased the reactive oxygen species level and blocked the cell cycle in G0/G1 phase, and induced apoptosis of tumor cells by inhibiting the PI3K/Akt/mTOR pathway. In vivo 4T1 mouse model of breast cancer showed that 13o not only continued to inhibit tumor proliferation but also had a stronger effect than the marketed drug 5-fluorouracil, compound 13o had a good safety profile in vivo. The results suggest that compound 13o may represent a novel, highly potent and low-toxicity structural lead for the development of new breast cancer chemotherapies.

Deciphering Mechanisms of Adipocyte Differentiation in Abdominal Fat of Broilers

The excessive deposition of abdominal fat tissue (AFT) in broilers has emerged as a major concern in the poultry industry. Despite some progress in recent years, the molecular mechanisms underlying AFT development remain ambiguous. The current study combined RNA-seq with transposase-accessible chromatin sequencing (ATAC-seq) to map the dynamic profiling of chromatin accessibility and transcriptional reprogramming in AFT adipocyte differentiation in broilers at day 3 (D3) and D14. Our results found that the levels of CDK1 and PCNA were down-regulated at D14, D28, and D42 compared to D3, while the levels of C/EBPα and FABP4 were up-regulated at D14 and D42 compared to D3. Meanwhile, PPARγ was significantly up-regulated at D28 and D42. RNA-seq of AFT identified 1705 up-regulated and 1112 down-regulated differential expression genes (DEGs) between D3 and D14. Pathways based on up-regulated DEGs mainly enriched some pathways related to adipocyte differentiation, while down-regulated DEGs pointed to DNA replication, cell cycle, and gap junction. Gene set enrichment analysis (GSEA) revealed that DNA replication and the cell cycle were down-regulated at D14, while the insulin signaling pathway was up-regulated. In the OA-induced immortalized chicken preadipocyte (ICP2) model, protein dynamic changes were consistent with AFT from D3 to D14. Same pathways were enriched in ICP2. In addition, based on overlapped DEGs from AFT and ICP2, enriched pathways related to adipocyte differentiation or proliferation mentioned above were all involved. A total of 1600 gain and 16727 loss differential peaks (DPs) were identified in ICP2 by ATAC-seq. Predicted genes from DPs at the promoter regions were enriched in glycerophospholipid metabolism, TGF-β signaling, FoxO signaling, and ubiquitin-mediated proteolysis. DNA motifs predicted 159 transcription factors (TFs) based on gain and loss peaks from the promoter regions, where 1 and 10 TFs were overlapped with up or down TFs from DEGs. Overall, this study presents a framework for the comprehension of the epigenetic regulatory mechanisms of adipocyte differentiation and identifies candidate genes and potential TFs involved in AFT adipocyte differentiation in broilers.

E2F2 Promotes Wound Healing of Diabetic Foot Ulcer by Regulating CDCA7L Transcription

OBJECTIVE

The E2F2 transcription factor can accelerate cell proliferation and wound healing. However, its mechanism of action in a diabetic foot ulcer (DFU) remains unclear. Therefore, this study explores the influence of E2F2 on wound healing in DFU by examining cell division cycle-associated 7-like (CDCA7L) expression.

METHODS

CDCA7L and E2F2 expression in DFU tissues were analyzed with databases. CDCA7L and E2F2 expression were altered in human umbilical vein endothelial cells (HUVECs) and spontaneously transformed human keratinocyte cell culture (HaCaT) cells. Cell viability, migration, colony formation, and angiogenesis were evaluated. Binding of E2F2 to the CDCA7L promoter was examined. Subsequently, a diabetes mellitus (DM) mouse model was established and treated with full-thickness excision followed by CDCA7L overexpression. Wound healing in these mice was observed and recorded, and vascular endothelial growth factor receptor 2 (VEGFR2) and hematopoietic progenitor cell antigen CD34 (CD34) expression were determined. E2F2 and CDCA7L expression levels in cells and mice were evaluated. The expression of growth factors was tested.

RESULTS

CDCA7L expression was downregulated in DFU tissues and wound tissues from DM mice. Mechanistically, E2F2 bound to the CDCA7L promoter to upregulate CDCA7L expression. E2F2 overexpression enhanced viability, migration, and growth factor expression in HaCaT cells and HUVECs, and augmented HUVEC angiogenesis and HaCaT cell proliferation, which was nullified by silencing CDCA7L. In DM mice, CDCA7L overexpression facilitated wound healing and elevated the expression level of growth factors.

CONCLUSIONS

E2F2 facilitated cell proliferation and migration and fostered wound healing in DFU cells through binding to the CDCA7L promoter.

Leptin Silencing Attenuates Lipid Accumulation through Sterol Regulatory Element-Binding Protein 1 Inhibition in Nasopharyngeal Carcinoma

Leptin is a crucial regulator of metabolism and energy homeostasis in mammals. Many studies have investigated the impacts of leptin on human cancers, such as proliferation and metastasis. However, the mechanisms underlying leptin-mediated regulation of lipid metabolism in nasopharyngeal carcinoma (NPC) remain incompletely understood. In the current study, leptin downregulation ameliorated lipid accumulation, triglyceride, and cholesterol levels. Mechanistically, diminished leptin by siRNA not only inhibited sterol regulatory element-binding protein 1 (SREBP1), a master regulator of lipid metabolism, at the mRNA and protein levels, but also reduced SREBP1 downstream target expressions, such as fatty acid synthase (FASN) and stearoyl-CoA desaturase-1 (SCD1), in NPC cells. In addition, leptin expression could modulate the promoter activity of SREBP1. We also found that pharmacological inhibition of poly-ADP ribose polymerase-γ (PPAR-γ) resulted in increased SREBP1 expression in leptin-depleted NPC cells. Functionally, SREBP1 overexpression overcame the effects of leptin-silencing attenuated triglyceride level, cholesterol level and cell survival in NPC cells. Taken together, our results demonstrate that leptin is an important regulator of lipid metabolism in NPC cells and might could be a potential therapeutic target for treatment of NPC patients.

CDKN2B-AS1 promotes the proliferation, clone formation, and invasion of nasopharyngeal carcinoma cells by regulating miR-98-5p/E2F2 axis

OBJECTIVE

To explore the effect of CDKN2B antisense RNA 1 (CDKN2B-AS1) on the proliferation, clone formation, and invasion of nasopharyngeal carcinoma (NPC) cells by regulating miR-98-5p/E2F transcription factor 2 (E2F2) axis.

METHODS

The expressions of CDKN2B-AS1, miR-98-5p, and E2F2 in NPC tissues and cell lines (SUNE-1, 5-8F, 6-10B, and HK-1) as well as in peritumoral normal tissues and cell line NP69 were determined by qRT-PCR. Subcellular localization of CDKN2B-AS1 was detected using the fluorescence in situ hybridization assay. The targeting relationships between CDKN2B-AS1 and miR-98-5p as well as between miR-98-5p and E2F2 were analyzed by the dual-luciferase reporter assay and RNA binding protein immunoprecipitation assay. The proliferation, clone formation and invasion of 5-8F cells were measured using the CCK-8 assay, Clone formation assay, and transwell assay, respectively.

RESULTS

CDKN2B-AS1 was highly expressed in NPC tissues and cells, whereas the expression of miR-98-5p decreased in the NPC tissues and cells. Silencing of CDKN2B-AS1 inhibited the proliferation, clone formation, and invasion of NPC cells (all P<0.05). CDKN2B-AS1 acted asceRNA of miR-98-5p, and miR-98-5p inhibitor could partially reverse the inhibitory effect of silencing CDKN2B-AS1 on NPC cells (all P<0.05). CDKN2B-AS1 upregulated E2F2 by inhibiting miR-98-5p, and the upregulation of E2F2 partially reversed the inhibitory effect of miR-98-5p overexpression on the NPC cells (all P<0.05).

CONCLUSION

CDKN2B-AS1, as a lncRNA, can regulate E2F2 by sponging miR-98-5p to promote the proliferation, clone formation, and invasion of NPC cells.

STK38 is a PPARγ-interacting protein promoting adipogenesis

Peroxisome proliferator-activated receptor-γ (PPARγ) is the master regulator of adipogenesis, but knowledge about how PPARγ is regulated at the protein level is very limited. We aimed to identify PPARγ-interacting proteins which modulate PPARγ’s protein levels and transactivating activities in human adipocytes. We expressed Flag-tagged PPARγ in human preadipocytes as bait to capture PPARγ-associated proteins, followed by mass spectroscopy and proteomics analysis, which identified serine/threonine kinase 38 (STK38) as a major PPARγ-associated protein. Protein pulldown studies confirmed this protein–protein interaction in transfected cells, and reporter assays demonstrated that STK38 enhanced PPARγ’s transactivating activities without requiring STK38’s kinase activity. In cell-based assays, STK38 increased PPARγ protein stability, extending PPARγ’s half-life from ~1.08 to 1.95 h. Notably, in human preadipocytes, the overexpression of STK38 enhanced adipogenesis, whereas knockdown impaired the process in a PPARγ-dependent manner. Thus, we discovered that STK38 is a novel PPARγ-cofactor promoting adipogenesis, likely through stabilization of PPARγ

E2F2 drives glioma progression via PI3K/AKT in a PFKFB4-dependent manner

AIMS

The effects of PFKFB4 on glycolysis during the cancer progression has been investigated, while its role in glioma remains unclear. The present study evaluated the molecular mechanism of PFKFB4 in glycolysis of glioma progression.

MATERIALS AND METHODS

The pan-cancer platform SangerBox was inquired to investigate the E2F2 expression in tumors. The E2F2 expression was studied by qRT-PCR and immunohistochemistry in collected glioma and normal brain tissues and by qRT-PCR and western blot in glioma cells. The relationship between the E2F2 expression in glioma tissues and patients' prognosis was analyzed. The cell malignant phenotype, glycolysis, growth and metastasis were examined by CCK-8, EdU, colony formation, flow cytometry, wound healing, Transwell assays, ELISA kits, and tumorigenesis and metastasis assays. Downstream targets of E2F2 were searched in hTFtarget, followed by pathway enrichment analysis. The expression of these targets and their correlation with E2F2 expression in gliomas were investigated through the GEPIA website. After ChIP and luciferase assays, the effect of the target on glioma was investigated.

KEY FINDINGS

E2F2 was overexpressed in glioma patients and predicted poor prognoses. E2F2 promoted cell proliferation, colony formation, DNA synthesis, migration, invasion and glycolysis, and inhibited apoptosis. Meanwhile, inhibition of E2F2 suppressed the growth and metastasis of gliomas. E2F2 elevated the PFKFB4 expression transcriptionally by binding to its promoter and activated PI3K/AKT pathway. The promotion of glioma metastasis and glycolysis by E2F2 was mitigated by PFKFB4 knockdown.

SIGNIFICANCE

E2F2-mediated transcriptional enhancement of PFKFB4 expression regulated the phosphorylation of PI3K/AKT to promote glioma malignancy progression.

miR-22-3p/PGC1β Suppresses Breast Cancer Cell Tumorigenesis via PPARγ

In this study, we found that miR-22-3p expression was decreased in breast cancer (BC) cell lines and tissues. Overexpression of miR-22-3p inhibited the proliferation and migration of BC cells in vitro and in vivo, while depletion of miR-22-3p exhibited the opposite effect. Importantly, miR-22-3p could directly target PGC1β and finally regulate the PPARγ pathway in BC. In conclusion, miR-22-3p/PGC1β suppresses BC cell tumorigenesis via PPARγ, which may become a potential biomarker and therapeutic target.

DOCK4 Is a Platinum-Chemosensitive and Prognostic-Related Biomarker in Ovarian Cancer

Ovarian carcinoma (OV) is a lethal gynecological malignancy. Most OV patients develop resistance to platinum-based chemotherapy and recurrence. Peroxisome proliferator-activated receptors (PPARs) are the ligand activating transcription factor of the nuclear receptor superfamily. PPARs as important transcriptional regulators regulate important physiological processes such as lipid metabolism, inflammation, and wound healing. Several reports point out that PPARs can also have an effect on the sensitivity of tumor cells to platinum-based chemotherapy drugs. However, the role of PPAR-target related genes (PPAR-TRGs) in chemotherapeutic resistance of OV remains unclear. The present study is aimed at optimizing candidate genes by integrating platinum-chemotherapy expression data and PPAR family genes with their targets. The gene expression profiles were obtained from Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) database. A total of 4 genes (AP2A2, DOCK4, HSDL2, and PDK4) were the candidate differentially expressed genes (DEGs) of PPAR-TRGs with platinum chemosensitivity. After conducting numerous survival analyses using different cohorts, we found that only the upexpression of DOCK4 has important significance with the poor prognosis of OV patients. Meanwhile, DOCK4 is detected in plasma and enriched in neutrophil and monocyte cells of the blood. We further found that there were significant correlations between DOCK4 expression and the levels of CD4+ T cell infiltration, dendritic cell infiltration, and neutrophil infiltration in OV. In addition, we verified the expression level of DOCK4 in OV cell lines treated with platinum drugs and found that DOCK4 is potentially responsive to platinum drugs. In conclusion, DOCK4 is potentially associated with immune cell infiltration and represents a valuable prognostic biomarker in ovarian cancer patients.

Apigenin Alleviates Liver Fibrosis by Inhibiting Hepatic Stellate Cell Activation and Autophagy via TGF-β1/Smad3 and p38/PPARα Pathways

OBJECTIVE

The aim of this study is to confirm the hepatocellular protective functions of apigenin and the molecular mechanism on liver fibrosis in mice.

METHODS

Carbon tetrachloride (CCl4) and bile duct ligature (BDL) mouse fibrosis models were used to investigate the effects of apigenin on liver fibrosis. Sixty-six male C57 mice were randomly divided into eight groups, including the vehicle group, CCl4 group, CCl4+L-apigenin (20 mg/kg) group, CCl4+H-apigenin (40 mg/kg) group, sham group, BDL group, BDL+L-apigenin(20 mg/kg) group, and BDL+H-apigenin(40 mg/kg) group. Serum liver enzymes (ALT and AST), proteins associated with autophagy, and indicators linked with the TGF-β1/Smad3 and p38/PPARα pathways were detected using qRT-PCR, immunohistochemical staining, and western blotting.

RESULTS

Our findings confirmed that apigenin could decrease the levels of ALT and AST, suppress the generation of ECM, inhibit the activation of HSCs, regulate the balance of MMP2 and TIMP1, reduce the expression of autophagy-linked protein, and restrain the TGF-β1/Smad3 and p38/PPARα pathways.

CONCLUSION

Apigenin could alleviate liver fibrosis by inhibiting hepatic stellate cell activation and autophagy via TGF-β1/Smad3 and p38/PPARα pathways.

Meta-Analysis of Transcriptome Data Detected New Potential Players in Response to Dioxin Exposure in Humans

Dioxins are one of the most potent anthropogenic poisons, causing systemic disorders in embryonic development and pathologies in adults. The mechanism of dioxin action requires an aryl hydrocarbon receptor (AhR), but the downstream mechanisms are not yet precisely clear. Here, we performed a meta-analysis of all available transcriptome datasets taken from human cell cultures exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Differentially expressed genes from different experiments overlapped partially, but there were a number of those genes that were systematically affected by TCDD. Some of them have been linked to toxic dioxin effects, but we also identified other attractive targets. Among the genes that were affected by TCDD, there are functionally related gene groups that suggest an interplay between retinoic acid, AhR, and Wnt signaling pathways. Next, we analyzed the upstream regions of differentially expressed genes and identified potential transcription factor (TF) binding sites overrepresented in the genes responding to TCDD. Intriguingly, the dioxin-responsive element (DRE), the binding site of AhR, was not overrepresented as much as other cis-elements were. Bioinformatics analysis of the AhR binding profile unveils potential cooperation of AhR with E2F2, CTCFL, and ZBT14 TFs in the dioxin response. We discuss the potential implication of these predictions for further dioxin studies.

The role and function of PPARγ in bladder cancer

Peroxisome proliferator-activated receptor gamma (PPARγ), a member of the nuclear receptor superfamily, participates in multiple physiological and pathological processes. Extensive studies have revealed the relationship between PPARγ and various tumors. However, the expression and function of PPARγ in bladder cancer seem to be controversial. It has been demonstrated that PPARγ affects the occurrence and progression of bladder cancer by regulating proliferation, apoptosis, metastasis, and reactive oxygen species (ROS) and lipid metabolism, probably through PPARγ-SIRT1 feedback loops, the PI3K-Akt signaling pathway, and the WNT/β-catenin signaling pathway. Considering the frequent relapses after chemotherapy, some researchers have focused on the relationship between PPARγ and chemotherapy sensitivity in bladder cancer. Moreover, the feasibility of PPARγ ligands as potential therapeutic targets for bladder cancer has been uncovered. Taken together, this review summarizes the relevant literature and our findings to explore the complicated role and function of PPARγ in bladder cancer.

A significant role of transcription factors E2F in inflammation and tumorigenesis of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor from head and neck with characteristics in remarkable geographic and racial distribution worldwide, which has the important features of vigorous proliferation and inflammatory cells infiltration. By analyzing the expression profile data of NPC, we found that the E2F-related gene sets were highly enriched in NPC tissues. E2F transcription factor family is an important cycle regulator, which can promote the malignant proliferation and tumorigenesis. Here, we showed that E2Fs accelerated malignant phenotypes of NPC cells. RNA sequencing revealed that E2Fs can significantly up-regulate the inflammatory pathways in NPC cells. E2F1, as a transcription factor, can active the transcription activity of IL-6 promoter, and modulate macrophage function through a microenvironment manner. Thus, this study characterized a significant role of E2Fs in inflammation and tumorigenesis of NPC, which provided a promising anti-tumor target in NPC, since E2Fs are highly expressed and activated in NPC.