Adenosylhomocysteinase plays multiple roles in maintaining the identity and pluripotency of mouse embryonic stem cells†.

Adenosylhomocysteinase (AHCY), a key enzyme in the methionine cycle, is essential for the development of embryos and the maintenance of mouse embryonic stem cells (mESCs). However, the precise underlying mechanism of Ahcy in regulating pluripotency remains unclear. As the only enzyme that can hydrolyze S-adenosylhomocysteine in mammals, AHCY plays a critical role in the metabolic homeostasis, epigenetic remodeling, and transcriptional regulation. Here, we identified Ahcy as a direct target of OCT4 and unveiled that AHCY regulates the self-renewal and differentiation potency of mESCs through multiple mechanisms. Our study demonstrated that AHCY is required for the metabolic homeostasis of mESCs. We revealed the dual role of Ahcy in both transcriptional activation and inhibition, which is accomplished via the maintenance of H3K4me3 and H3K27me3, respectively. We found that Ahcy is required for H3K4me3-dependent transcriptional activation in mESCs. We also demonstrated that AHCY interacts with polycomb repressive complex 2 (PRC2), thereby maintaining the pluripotency of mESCs by sustaining the H3K27me3-regulated transcriptional repression of related genes. These results reveal a previously unrecognized OCT4-AHCY-PRC2 axis in the regulation of mESCs' pluripotency and provide insights into the interplay between transcriptional factors, cellular metabolism, chromatin dynamics and pluripotency regulation.

FKBP11 improves the malignant property of osteosarcoma cells and acts as a prognostic factor of osteosarcoma.

BACKGROUND: Osteosarcoma has become the most common bone malignancy in adolescents. Although the clinical treatment of osteosarcoma has advanced considerably in recent years, the 5-year survival rate has not improved significantly. Recently, many studies have shown that mRNA has unique advantages as a target for drug therapy. Therefore, this study aimed to identify a new prognostic factor and provide a new target for the treatment of osteosarcoma to improve the prognosis of patients. METHODS AND RESULTS: We selected prognostic genes that are closely associated with osteosarcoma clinical features by obtaining osteosarcoma patient information from the GTEx and TARGET databases, and then we developed a risk model. We detected the expression of FKBP11 in osteosarcoma by qRT-PCR, western blotting, and immunohistochemistry and performed CCK-8, Transwell, colony formation, and flow cytometry assays to reveal the regulatory role of FKBP11. We found that FKBP11 was highly expressed in osteosarcoma; silencing FKBP11 expression suppressed the invasion and migration of osteosarcoma cells, slowed cell proliferation, and promoted apoptosis. We also found that silencing the expression of FKBP11 led to inhibition of MEK/ERK phosphorylation. CONCLUSIONS: In conclusion, we validated that the prognostic factor FKBP11 is closely associated with osteosarcoma. Additionally, we identified a novel mechanism by which FKBP11 ameliorates the malignant properties of osteosarcoma cells through the MAPK pathway and serves as a prognostic factor in osteosarcoma. This study provides a new method for the treatment of osteosarcoma.

Stabilization of SAMHD1 by NONO is crucial for Ara-C resistance in AML.

Cytarabine (Ara-C) is the first-line drug for the treatment of acute myelogenous leukemia (AML). However, resistance eventually develops, decreasing the efficacy of Ara-C in AML patients. The expression of SAMHD1, a deoxynucleoside triphosphate (dNTP) triphosphohydrolase, has been reported to be elevated in Ara-C-resistant AML patients and to play a crucial role in mediating Ara-C resistance in AML. However, the mechanism by which SAMHD1 is upregulated in resistant AML remains unknown. In this study, NONO interacted with and stabilized SAMHD1 by inhibiting DCAF1-mediated ubiquitination/degradation of SAMHD1. Overexpression of NONO increased SAMHD1 expression and reduced the sensitivity of AML cells to Ara-C, and downregulation of NONO had the opposite effects. In addition, the DNA-damaging agents DDP and adriamycin (ADM) reduced NONO/SAMHD1 expression and sensitized AML cells to Ara-C. More importantly, NONO was upregulated in Ara-C-resistant AML cells, resulting in increased SAMHD1 expression in resistant AML cells, and DDP and ADM treatment resensitized resistant AML cells to Ara-C. This study revealed the mechanism by which SAMHD1 is upregulated in Ara-C-resistant AML cells and provided novel therapeutic strategies for Ara-C-resistant AML.

The synergistic anticancer effect of the bromodomain inhibitor OTX015 and histone deacetylase 6 inhibitor WT-161 in osteosarcoma.

BACKGROUND: Osteosarcoma (OS) is a tumour with a high malignancy level and a poor prognosis. First-line chemotherapy for OS has not been improved for many decades. Bromodomain and extraterminal domain (BET) and histone deacetylases (HDACs) regulate histone acetylation in tandem, and BET and HDACs have emerged as potential cancer therapeutic targets. METHODS: Cell proliferation, migration, invasion, colony formation, and sphere-forming assays were performed with the two inhibitors alone or in combination to evaluate their suppressive effect on the malignant properties of OS cells. Apoptosis and the cell cycle profile were measured by flow cytometry. The synergistic inhibitory effect of OTX015/WT-161 on tumours was also examined in a nude mouse xenograft model. RESULTS: The combined therapy of OTX015/WT-161 synergistically inhibited growth, migration, and invasion and induced apoptosis, resulting in G1/S arrest of OS cells. Additionally, OTX015/WT-161 inhibited the self-renewal ability of OS stem cells (OSCs) in a synergistic manner. Further mechanistic exploration revealed that the synergistic downregulation of ß-catenin by OTX015-mediated suppression of FZD2 and WT-161-mediated upregulation of PTEN may be critical for the synergistic effect. Finally, the results of an in vivo assay showed that tumour xenografts were significantly decreased after treatment with the OTX015/WT-161 combination compared with OTX015 or WT-161 alone. CONCLUSIONS: Our findings in this study demonstrated that OTX015 and WT-161 had synergistic anticancer efficacy against OS, and their combination might be a promising therapeutic strategy for OS.

Serglycin promotes proliferation, migration, and invasion via the JAK/STAT signaling pathway in osteosarcoma.

BACKGROUND: Osteosarcoma (OS) is a common disease in the world, and its pathogenesis is still unclear. This study aims to identify the key genes that promote the proliferation, invasion, and metastasis of osteosarcoma cells. METHOD: GSE124768 and GSE126209 were downloaded from the Gene Expression Omnibus (GEO) database. The gene ontology and enrichment pathway were analyzed by FunRich software. qPCR and Western blot were used to detect the gene expression. After gene knockdown, Transwell and wound healing assays were conducted on osteosarcoma cells to detect whether the genes were defined before enhancing the invasion of osteosarcoma. RESULTS: Totally, 341 mRNAs were found to be regulated differentially in osteosarcoma cells compared to osteoblasts. In addition, the expression level of Serglycin (SRGN) in osteosarcoma cells was higher than that in human osteoblasts. The invasion and proliferation ability of osteosarcoma cells with upregulated Serglycin was significantly increased, and on the contrary, decreased after Serglycin knockdown. Moreover, we preliminarily found that Serglycin may associate with the JAK/STAT signaling pathway. CONCLUSIONS: By using microarray and bioinformatics analyses, differently expressed mRNAs were identified and a complete gene network was constructed. To our knowledge, we describe for the first time Serglycin as a potential biomarker.

Targeting the p300/NONO axis sensitizes melanoma cells to BRAF inhibitors.

BRAF inhibitors (BRAFi) that target BRAF V600E kinase, a driver mutation found in 50% of melanomas, show a significant antitumor response, but the common emergence of acquired resistance remains a challenge. Abnormal expression of RAF isoforms CRAF and ARAF reactivates pERK1/2, which plays crucial roles in the acquisition of resistance of melanoma cells. However, the mechanisms of dysregulation of RAF isoforms in resistant melanoma cells remain unknown. Here, we identified NONO interacted with and stabilized both CRAF and ARAF in melanoma cells, and that NONO was acetylated at 198K by p300 acetyltransferase, which stabilized NONO via antagonizing its ubiquitination/degradation mediated by RNF8. The upregulation of both p300 and NONO promoted the rebound of pERK1/2 and the subsequent resistance of melanoma cells to BRAFi, and the activation of ERK1/2 in turn induced p300 to form a positive feedback loop in resistant melanoma cells. There was a positive correlation between p300 and NONO in resistant melanoma cells and clinical samples, and p300 inhibitor C646 overcame the resistance of resistant melanoma cells to BRAF inhibitors in vitro and in vivo. Our findings reveal that targeting the positive feedback loop of p300-NONO-CRAF/ARAF-pERK1/2 may be excellent strategies to overcome the resistance of BRAF inhibitors for melanoma patients.

HDAC6 inhibitor WT161 performs anti-tumor effect on osteosarcoma and synergistically interacts with 5-FU.

BACKGROUND: WT161, as a selective HDAC6 inhibitor, has been shown to play anti-tumor effects on several kinds of cancers. The aim of the present study is to explore the roles of WT161 in osteosarcoma and its underlying mechanisms. METHODS: The anti-proliferative effect of WT161 on osteosarcoma cells was examined using MTT assay and colony formation assay. Cell apoptosis was analyzed using flow cytometer. The synergistic effect was evaluated by isobologram analysis using CompuSyn software. The osteosarcoma xenograft models were established to evaluate the anti-proliferative effect of WT161 in vivo. RESULTS: WT161 suppressed the cell growth and induced apoptosis of osteosarcoma cells in a dose- and time-dependent manner. Mechanistically, we found that WT161 treatment obviously increased the protein level of PTEN and decreased the phosphorylation level of protein kinase-B (AKT). More importantly, WT161 showed synergistic inhibition with 5-FU on osteosarcoma cells in vitro and in vivo. CONCLUSIONS: These results indicate that WT161 inhibits the growth of osteosarcoma through PTEN and has a synergistic efficiency with 5-FU.

Role of LncRNAs in regulating cancer amino acid metabolism.

The metabolic change of tumor cells is an extremely complicated process that involves the intersection and integration of various signal pathways. Compared with normal tissues, cancer cells show distinguished metabolic characteristics called metabolic reprogramming, which has been considered as a sign of cancer occurrence. With the deepening of tumor research in recent years, people gradually found that amino acid metabolism played crucial roles in cancer progression. Long non-coding RNAs (lncRNAs), which are implicated in many important biological processes, were firstly discovered dysregulating in cancer tissues and participating in extensive regulation of tumorigenesis. This review focuses on the reprogramming of amino acid metabolism in cancers and how lncRNAs participate in the regulatory network by interacting with other macromolecular substances. Understanding the functions of lncRNA in amino acid reprogramming in tumors might provide a new vision on the mechanisms of tumorigenesis and the development of new approaches for cancer therapy.

The novel prognostic risk factor STC2 can regulate the occurrence and progression of osteosarcoma via the glycolytic pathway.

Osteosarcoma, a highly aggressive malignant tumor of the bone, usually occurs in children and young adults. However, although the considerable achievement in the clinical treatment of osteosarcoma recent years, the overall survival of osteosarcoma patients has not been obviously improved. Cancer cells preferentially use glycolysis instead of oxidative phosphorylation to meet their increased energetic and biosynthetic demands, a phenomenon known as the Warburg effect. Glycolysis is a driving factor in multiple cancers and is emerging as a new cancer target treatment. In the present study, we established a model to screen for glycolysis-associated genes in osteosarcoma. This risk score of the model were correlated with clinical characteristics osteosarcoma patients. Besides, a functional assay identified that STC2 enhanced the glycolysis of osteosarcoma cells. Modulation of STC2 changes glucose consumption and lactate production as well as GLUT1 expression in osteosarcoma. Furthermore, we identified that change in the expression levels of STC2 affected the proliferation, invasion, and migration of osteosarcoma cells. Our findings showed STC2 as a new tumor-promoting factor of osteosarcoma cells through enhancing glycolysis.

Redox-responsive prodrug for improving oral bioavailability of paclitaxel through bile acid transporter-mediated pathway.

Most anticancer drugs are not orally bioavailable due to their undesirable physicochemical properties and inherent physiological barriers. In this study, a polymeric prodrug strategy was presented to enhance the oral bioavailability of BCS class IV drugs using paclitaxel (PTX) as the model drug. PTX was covalently conjugated with cholic acid-functionalized PEG by a redox-sensitive disulfide bond. Cholic acid-functionalized PEGylated PTX (CPP) achieved remarkably improved PTX solubility (>30,000-fold), as well as favorable stability under the physiological environment and controlled drug release in the tumor. Meanwhile, CPP could self-assemble into nanoparticles with an average size of 56.18 ± 2.06 nm and drug loading up to 17.6% (w/w). Then, permeability study on Caco-2 cell monolayers demonstrated that CPP obtained an approximately 4-fold increase by apical sodium-dependent bile acid transporter (ASBT) mediated transport, compared with Taxol®. Pharmacokinetic studies carried out in rats confirmed that the oral bioavailability of CPP was 10-fold higher than that of Taxol®. Finally, significant improvement in the antitumor efficacy of CPP against breast cancer was confirmed on MDA-MB-231 cells. In summary, this prodrug-based cascade strategy offers new ways for chemotherapeutic drugs whose oral delivery is limited by solubility and permeability, also endows drugs with the capacity of tumor-specific release.

LncRNA GSEC promotes the proliferation, migration and invasion by sponging miR-588/ EIF5A2 axis in osteosarcoma.

BACKGROUND: Long noncoding RNAs (LncRNAs) show dysregulation in a variety of cancers. However, the function and specific mechanism of LncRNA GSEC in the progression of osteosarcoma remain mostly unknown. In this study, we sought to elucidate the role and mechanism of LncRNA GSEC in the occurrence and progression of osteosarcoma. METHODS: we examined the expression of LncRNA GSEC in osteosarcoma cell lines by quantitative real time PCR. In vitro experiments, including transwell assays, cck8 assays, and flow cytometry analysis have biologically demonstrated the effect of LncRNA GSEC on the proliferation and migration of osteosarcoma cell lines. Furthermore, the regulation of miR-588 by LncRNA GSEC was determined by luciferase reporter assay and quantitative real time PCR. What's more, subcutaneous tumor formation was performed in nude mice to monitor the growth of the tumor in vivo. RESULTS: We found that the expression of LncRNA GSEC was up-regulated in osteosarcoma cell lines. Overexpression of LncRNA GSEC promoted the proliferating and migratory capacity, and inhibited the apoptosis of osteosarcoma cells. Conversely, knockdown of LncRNA GSEC resulted in the opposite effect. Mechanistically, we identified LncRNA GSEC functioned as the sponge of miR-588, thus inhibiting the miR-588/EIF5A2 signal pathway. In addition, the expression of miR-588 was negatively correlated with LncRNA GSEC, and the effect by silencing or overexpressing LncRNA GSEC could be rescued by the introduction of miR-588 mimics or inhibitors, respectively. CONCLUSIONS: In summary, this study shows that LncRNA GSEC promotes the proliferation and invasion of OS through the regulation of miR-588/EIF5A2 pathway, which might provide a new strategy for the treatment of osteosarcoma in the future.

Identification of BRMS1L as Metastasis Suppressing Gene in Esophageal Squamous Cell Carcinoma.

INTRODUCTION: Breast cancer metastasis suppressor 1 like (BRMS1-like)was first reported to be a component of the Sin3-HDAC complex, but the role in the progression of cancers was largely unknown. Our previous study reported that BRMS1L promoted the metastasis of breast cancer through facilitating the recruitment of HDAC complex to the promoter FZD10, and hence suppressing the transcription of FZD10. METHODS: In this study, we detected the expression level of BRMS1L in esophageal squamous cell carcinoma (ESCC). The effect of BRMS1L in TE-1D (knockdown) and ECA-109 (overexpression) cell lines was explored by transwell assays, wound healing assays, and cell adhesion assays. Quantitative real­time PCR, Western blot analysis, and luciferase assays were used to detect the interaction of the CBP/P300-BRMS1L-ITGA7 axis. RESULTS: In the present study, we found that knockdown of BRMS1L promoted the migration, invasion, and epithelial-mesenchymal transition (EMT). Conversely, overexpression of BRMS1L inhibited the migration and invasion of ESCC. Mechanistically, BRMS1L exerted their metastasis-suppressing role via transcriptionally repress ITGA7 expression. Moreover, we revealed that CBP/p 300 regulated the expression of BRMS1L and might be responsible for the down-regulation of BRMS1L in ESCC. CONCLUSION: Collectively, we identified the role of CBP/p300-BRMS1L-ITGA7 axis in the metastasis of ESCC.