Analysis of proliferation and apoptotic induction by 20 steroid glycosides in 143B osteosarcoma cells in vitro

Arenobufagin causes ferroptosis in human gastric cancer cells by increasing rev-erbα expression

Background and aims

Gastric cancer is the fifth most diagnosed malignant tumor worldwide with limited effective chemotherapy. Ferroptosis is a new type of programmed cell death, which is becoming as a novel therapeutic target for tumors. Arenobufagin (ArBu) is a bufadienolide isolated from toad skin and venom, which exhibits broad-spectrum anti-tumor activity. It is unclear whether ArBu causes ferroptosis, thereby exhibiting anti-tumor activity in gastric cancer. We aimed to determine whether ArBu causes ferroptosis in cultured human gastric cancer cells.

Experimental procedure

Different human gastric cancer cells were treated with ArBu (5-20 μM, 48 h). Indicators of apoptosis and ferroptosis were measured. CRISPR/Cas-9 system was employed to delete Nr1d1 gene.

Results

ArBu incubation reduced cell viability in a concentration-dependent manner. ArBu caused ferroptosis but not apoptosis at a lower concentration (10 μM), despite it caused both of them at a higher concentration (20 μM). Cotreatment with a selective ferroptosis inhibitor ferrostatin-1 protected against ArBu (10 μM)-induced reduction in cell viability. ArBu-mediated ferroptosis was associated with abnormal expression of genes involved in iron uptake, lipid peroxidation, and antioxidants. Particularly, Nr1d1 gene expression was most significantly increased after ArBu treatment. Furthermore, activating Rev-erbα encoded by Nr1d1 by a selective agonist GSK4112 (1 and 2 μM, 48 h) caused ferroptosis. In contrast, Rev-erbα knockout using the CRISPR/Cas-9 system diminished ArBu-induced ferroptosis in cultured human gastric cancer cells.

Conclusion

ArBu causes ferroptosis by increasing Rev-erbα expression in human gastric cancer cells. This has implications of ArBu as a promising therapy for gastric cancer.

Section

1. Natural Products.

Taxonomy classification by EVISE

Traditional medicine, pharmacology, gastric cancer, signal pathway.

LncRNA BCRT1 facilitates osteosarcoma progression via regulating miR-1303/FGF7 axis

Growing studies noted that lncRNA was closely related with the initiation and progression of tumors. However, the role of BCRT1 in the progression of osteosarcoma remains unknown. We noted that BCRT1 is significantly upregulated in osteosarcoma specimens and cells. Elevated expression of BCRT1 promotes cell growth and cell cycle in osteosarcoma cell. Moreover, BCRT1 induces EMT and secretion of inflammatory mediators in osteosarcoma cell. We illustrated that elevated expression of BCRT1 decreases miR-1303 expression in MG-63 cell. The expression of miR-1303 is lower in osteosarcoma specimens than in non-tumor specimens. There is an inverse interrelation between miR-1303 levels and BCRT1 levels in osteosarcoma specimens. Furthermore, we identified FGF7 is one direct target gene of miR-1303 in osteosarcoma cell. Ectopic expression of miR-1303 suppresses FGF7 expression and elevated expression of BCRT1 enhanced FGF7 expression in MG-63 cell. Finally, we illustrated that BCRT1 induces osteosarcoma cell cycle and proliferation and promotes EMT progression and inflammatory mediators secretion via modulating FGF7 expression. Our study suggested that BCRT1 acts as one oncogene in osteosarcoma progression.

Circ_0000527 promotes osteosarcoma cell progression through modulating miR-646/ARL2 axis

Accumulating evidence shows that circRNAs play critical roles in the development of human tumors. We observed that circ_0000527 was overexpressed in osteosarcoma cells (SAOS-2, HOS, MG-63 and U2OS) compared in hFOB1.19 cells. We demonstrated that the circ_0000527 level was higher in osteosarcoma specimens than in non-tumor specimens. The ectopic expression of circ_0000527 was shown to induce cell growth, cell cycle progression and the secretion of inflammatory mediators, including IL-1β, IL-6, IL-8 and TNF-α. We demonstrated that circ_0000527 sponges miR-646 in osteosarcoma cells and that ARL2 is a target gene of miR-646. MiR-646 expression was decreased and ARL2 was overexpressed in osteosarcoma cells (SAOS-2, HOS, MG-63 and U2OS) compared to hFOB1.19 cells. Overexpression of circ_0000527 was demonstrated to induce ARL2 expression in MG-63 cells. We showed that miR-646 was downregulated in osteosarcoma specimens compared to that of non-tumor specimens and that the level of circ_0000527 was negatively correlated with miR-646 expression in osteosarcoma specimens. The elevated expression of circ_0000527 was shown to promote cell growth and cell cycle progression by modulating miR-646 expression. The ectopic expression of circ_0000527 was shown to promote cell growth, cell cycle progression and the secretion of inflammatory mediators by modulating ARL2. The present study suggested that the circ_0000527/miR-646/ARL2 axis may be a potential treatment target for osteosarcoma.

Ouabain-Induced Cell Death and Survival. Role of α1-Na,K-ATPase-Mediated Signaling and [Na+]i/[K+]i-Dependent Gene Expression

Ouabain is of cardiotonic steroids (CTS) family that is plant-derived compounds and is known for many years as therapeutic and cytotoxic agents. They are specific inhibitors of Na,K-ATPase, the enzyme, which pumps Na+ and K+ across plasma membrane of animal cells. Treatment of cells by CTS affects various cellular functions connected with the maintenance of the transmembrane gradient of Na+ and K+. Numerous studies demonstrated that binding of CTS to Na,K-ATPase not only suppresses its activity but also induces some signal pathways. This review is focused on different mechanisms of two ouabain effects: their ability (1) to protect rodent cells from apoptosis through the expression of [Na+]i-sensitive genes and (2) to trigger death of non-rodents cells (so-called «oncosis»), possessing combined markers of «classic» necrosis and «classic» apoptosis. Detailed study of oncosis demonstrated that the elevation of the [Na+]i/[K+]i ratio is not a sufficient for its triggering. Non-rodent cell death is determined by the characteristic property of "sensitive" to ouabain α1-subunit of Na,K-ATPase. In this case, ouabain binding leads to enzyme conformational changes triggering the activation of p38 mitogen-activated protein kinases (MAPK) signaling. The survival of rodent cells with ouabain-«resistant» α1-subunit is connected with another conformational transition induced by ouabain binding that results in the activation of ERK 1/2 signaling pathway.

Molecular mechanisms of bufadienolides and their novel strategies for cancer treatment

Bufadienolides are cardioactive C24 steroids with an α-pyrone ring at position C17. In the last ten years, accumulating studies have revealed the anticancer activities of bufadienolides and their underlying mechanisms, such as induction of autophagy and apoptosis, cell cycle disruption, inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and stemness, and multidrug resistance reversal. As Na⁺/K⁺-ATPase inhibitors, bufadienolides have inevitable cardiotoxicity. Short half-lives, poor stability, low plasma concentration and oral bioavailability in vivo are obstacles for their applications as drugs. To improve the drug potency of bufadienolides and reduce their side effects, prodrug strategies and drug delivery systems such as liposomes and nanoparticles have been applied. Therefore, systematic and recapitulated information about the antitumor activity of bufadienolides, with special emphasis on the molecular or cellular mechanisms, prodrug strategies and drug delivery systems, is of high interest. Here, we systematically review the anticancer effects of bufadienolides and the molecular or cellular mechanisms of action. Research advancements regarding bufadienolide prodrugs and their tumor-targeting delivery strategies are critically summarized. This work highlights recent scientific advances regarding bufadienolides as effective anticancer agents from 2011 to 2019, which will help researchers to understand the molecular pathways involving bufadienolides, resulting in a selective and safe new lead compound or therapeutic strategy with improved therapeutic applications of bufadienolides for cancer therapy.

Enoxacin inhibits proliferation and invasion of human osteosarcoma cells and reduces bone tumour volume in a murine xenograft model

Osteosarcoma is the most prevalent primary bone malignancy in children and adolescents. Neoadjuvant chemotherapy combined with surgical resection, the current standard treatment of osteosarcoma, is associated with a 5-year survival rate of only ~70%. Therefore, it is necessary to identify new, more effective treatment strategies for patients with this lethal disease. Enoxacin is a highly effective broad-spectrum fluoroquinolone antibiotic with low toxicity. The drug inhibits the growth and metastasis of numerous tumour types, but its efficacy has not been studied in osteosarcoma. This study assessed the antitumour effects of enoxacin in osteosarcoma 143B cells and in a murine tumour xenograft model. Enoxacin inhibited the proliferation, invasion and migration of 143B cells, as well as inducing their apoptosis. These effects were thought to be mediated by downregulation of Bcl-xL, Bxl-2, matrix metalloproteinase (MMP)2 and MMP9 expression. Enoxacin also significantly impaired the growth of bone tumours in nude mice without affecting their liver or kidney function, or blood cell count. Collectively, these results indicate that enoxacin is a promising new drug for osteosarcoma that warrants further evaluation in clinical studies.

LncRNA HIF1A-AS2 promotes osteosarcoma progression by acting as a sponge of miR-129-5p

Increasing studies have demonstrated that long noncoding RNAs (lncRNAs) play vital roles in tumor development and progression. However, the relationship between osteosarcoma and HIF1AAS2 remains unknown. The expression of HIF1AAS2 and miR-129-5p was detected in osteosarcoma cell lines and samples via qRT-PCR. Cell Counting Kit-8 (CCK-8) and invasion assays were performed to determine cell proliferation and invasion ability, and a dual luciferase reporter assay was performed to determine the interaction between HIF1AAS2 and miR-129-5p. We showed that the expression of HIF1A-AS2 was upregulated in the osteosarcoma samples compared with the expression in noncancerous samples. Moreover, patients with high HIF1A-AS2 expression had a shorter overall survival. Ectopic expression of HIF1A-AS2 enhanced osteosarcoma cell proliferation, cell cycle progression and invasion. We found that overexpression of miR-129-5p decreased the luciferase activity of wild-type (WT) HIF1A-AS2 but not mutant HIF1A-AS2. Ectopic expression of HIF1A-AS2 suppressed miR-129-5p expression in MG-63 cells. We demonstrated that miR-129-5p was downregulated in osteosarcoma and was negatively associated with HIF1A-AS2 expression. Furthermore, ectopic expression of miR-129-5p suppressed osteosarcoma cell proliferation, cell cycle progression and invasion. In addition, overexpression of HIF1A-AS2 promoted cell proliferation, cell cycle progression and invasion of osteosarcoma cells through the modulation of miR-129-5p. These results indicated that HIF1A-AS2 might be a potential therapeutic target for osteosarcoma.

LncRNA Linc00511 promotes osteosarcoma cell proliferation and migration through sponging miR-765

Long noncoding RNA (lncRNA) Linc00511 is a novel lncRNA, and it was reported to play important roles in the progression and carcinogenesis of several tumors. However, the expression and biological roles of Linc00511 in osteosarcoma were still unknown. In this research, we showed that the expression of Linc00511 was upregulated in osteosarcoma samples and cell lines. Ectopic expression of Linc00511 promoted osteosarcoma cell growth, colony formation, and migration. Moreover, overexpression of Linc00511 enhanced the epithelial-mesenchymal transition progression in osteosarcoma cell. In addition, we showed that elevated expression of Linc00511 suppressed microRNA-765 (miR-765) expression and promoted apurinic/apyrimidinic endonuclease 1 (APE1) expression in osteosarcoma cell. The expression of miR-765 was downregulated in osteosarcoma cells and samples and was negatively related to Linc00511 expression in osteosarcoma tissues. Ectopic expression of miR-765 inhibited osteosarcoma cell growth and migration. Furthermore, we showed that Linc00511 overexpression promoted MG-63 cells proliferation, colony formation, and migration via downregulation of miR-765. These results suggested that Linc00511 played as an oncogene in the development of osteosarcoma.

A novel three-dimensional high-throughput screening approach identifies inducers of a mutant KRAS selective lethal phenotype

The RAS proteins are the most frequently mutated oncogenes in cancer, with highest frequency found in pancreatic, lung, and colon tumors. Moreover, the activity of RAS is required for the proliferation and/or survival of these tumor cells and thus represents a high-value target for therapeutic development. Direct targeting of RAS has proven challenging for multiple reasons stemming from the biology of the protein, the complexity of downstream effector pathways and upstream regulatory networks. Thus, significant efforts have been directed at identifying downstream targets on which RAS is dependent. These efforts have proven challenging, in part due to confounding factors such as reliance on two-dimensional adherent monolayer cell cultures that inadequately recapitulate the physiologic context to which cells are exposed in vivo.  To overcome these issues, we implemented a High Throughput Screening (HTS) approach using a spheroid-based 3-dimensional culture format, thought to more closely reflect conditions experienced by cells in vivo. Using isogenic cell pairs, differing in the status of KRAS, we identified Proscillaridin A as a selective inhibitor of cells harboring the oncogenic KRas^G12V allele. Significantly, the identification of Proscillaridin A was facilitated by the 3D screening platform and would not have been discovered employing standard 2D culturing methods.

LncRNA CCAT2 promoted osteosarcoma cell proliferation and invasion

Long non‐coding RNA (lncRNA) plays important roles in tumour progression. Accumulating studies demonstrated that lncRNA colon cancer‐associated transcript 2 (CCAT2) acted as an oncogene in many tumours. However, the role of CCAT2 in the development of osteosarcoma has not been elucidated. In our study, we indicated that CCAT2 expression was up‐regulated in osteosarcoma tissues and cell lines (SOSP‐9607, MG‐63, U2OS and SAOS‐2). In addition, osteosarcoma cases with higher CCAT2 expression had a poorer disease‐free survival and shorter the overall survival time compared to those with lower expression. Overexpression of CCAT2 promoted osteosarcoma cell proliferation, invasion and cell cycle. Furthermore, ectopic expression of CCAT2 increased the expression of mesenchymal markers N‐cadherin, vimentin and snail and reduced the expression of N‐cadherin marker E‐cadherin. CCAT2 overexpression promoted the LATS2 and c‐Myc expression in osteosarcoma cell. These data indicated that CCAT2 served as an oncogene in osteosarcoma and promoted osteosarcoma cell proliferation, cell cycle and invasion.

NOVA1 acts as an oncogene in osteosarcoma

Osteosarcoma is one of the most common bone tumors in young patients. NOVA1 (neuro-oncological ventral antigen 1) is a neuron-specific RNA binding-protein and belongs to the Nova family. Previous studies showed that NOVA1 played crucial roles in the development of several tumors. The objective of our study was to study the role of NOVA1 in the osteosarcoma. In our study, we showed that NOVA1 expression was upregulated in osteosarcoma cell lines and tissues. The expression of NOVA1 was upregulated in 22 (22/30; 73%) osteosarcoma cases compared to that in the adjacent tissues. Overexpression of NOVA1 promoted osteosarcoma cell viability, colony formation and invasion. Furthermore, knockdown of NOVA1 suppressed osteosarcoma cell viability, colony formation and invasion. These data suggested that NOVA1 acted as an oncogene in the development of osteosarcoma.

Suppression of mRNA Nanoparticle Transfection in Human Fibroblasts by Selected Interferon Inhibiting Small Molecule Compounds

In vitro transcribed (IVT) mRNA is increasingly applied in lieu of DNA to deliver reprogramming genes to fibroblasts for stem cell derivation. However, IVT mRNA induces interferon (IFN) responses from mammalian cells that reduces transfection efficiency. It has been previously suggested that small molecule inhibitors of IFN are a viable strategy to enhance mRNA transfection efficiency. Herein, we screen a list of commercially available small molecules, including published IFN inhibitors, for their potential to enhance mRNA transfection in BJ fibroblasts. Transfection enhancement is quantified by relative mean fluorescence intensity of translated green fluorescent protein (GFP) in treated cells compared to dimethyl sulfoxide treated controls. Within toxicological constrains, all tested small molecules did not enhance mRNA transfection in BJ fibroblasts while a third of the tested compounds unexpectedly inhibited GFP expression even though IFN-β production is inhibited. Based on the results of our study, we conclude that small molecule inhibitors, including IFN inhibitors, tested in this study do not enhance in vitro mRNA transfection efficiency in human fibroblasts.

MicroRNA-448 suppresses osteosarcoma cell proliferation and invasion through targeting EPHA7

Osteosarcoma is the most common type of malignant bone tumor, often affecting adolescents and children. MicroRNAs (miRNAs) are a group of small, non-protein coding, endogenous RNAs that play critical roles in osteosarcoma tumorigenesis. In our study, we demonstrated that miR-448 expression was downregulated in osteosarcoma tissues and cell lines. Overexpression of miR-448 suppressed osteosarcoma cell proliferation, colony formation and migration. Moreover, we found that EPHA7 was a direct target gene of miR-448 in osteosarcoma cells. We further demonstrated that the EPHA7 expression level was upregulated in osteosarcoma tissues. Interestingly, the expression level of EPHA7 was inversely correlated with the expression level of miR-448 in osteosarcoma tissues. In addition, elevated expression of miR-448 suppressed osteosarcoma cell proliferation and invasion through targeting EPHA7. Taken together, these findings suggest that miR-448 functioned as a tumor suppressor gene in the development of osteosarcoma through targeting EPHA7.

MicroRNA-610 suppresses osteosarcoma oncogenicity via targeting TWIST1 expression

Osteosarcoma is the most frequent primary bone tumor affects adolescents and young adults. Recently, microRNAs (miRNAs) are short, non-coding and endogenous RNAs that played as important roles in the initiation and progression of tumors. In this study, we try to explore the biological function and expression of miR-610 in the osteosarcoma. We showed that miR-610 expression was downregulated in the osteosarcoma tissues and cell lines. Elevated expression of miR-610 suppressed the osteosarcoma cell proliferation, cell cycle, invasion and EMT program. Moreover, overexpression of miR-610 increased sensitivity of MG-63 and U2OS cells to cisplatin. Twist1 was identified as a direct target gene of miR-610 in the osteosarcoma cell. Furthermore, we demonstrated that Twist1 was upregulated in the osteosarcoma tissues and cell lines. The expression of Twist1 was negatively associated with the expression of miR-610 expression in the osteosarcoma tissues. Ectopic expression of Twist1 inhibited the sensitivity of miR-610-overexpressing MG-63 cells to cisplatin. We also showed that overexpression of Twist1 increased the proliferation and invasion of miR-610-overexpressing MG-63 cells. These data indicated that ectopic expression of miR-610 suppressed the osteosarcoma cell proliferation, cell cylce, invasion and increased the sensitivity of osteosarcoma cells to cisplatin through targeting the Twist1 expression.

MicroRNA-665 suppressed the invasion and metastasis of osteosarcoma by directly inhibiting RAB23

MicroRNAs (miRNAs) are small, short and noncoding RNAs that regulate gene expression posttranscriptionally. Increasing evidences have demonstrated that deregulated expression of miRNAs is found in osteosarcoma. In this study, we demonstrated that miR-665 was downregulated in osteosarcoma tissues compared to non-tumorous tissues. The overall survival (OS) of osteosarcoma patients with low miR-665 expression was lower than that of these patients with high miR-665 expression. Ectopic expression of miR-665 suppressed the osteosarcoma cell proliferation, EMT and invasion. We identified Rab23 as a direct target gene of miR-665. Rab23 was downregulated in osteosarcoma tissues and cell lines. The expression of miR-665 was inversely associated with the expression of Rab23 in the osteosarcoma tissues. These results suggested that miR-665 acted as a tumor suppressor gene in the development of osteosarcoma.

Antiplasmodial and Cytotoxic Activities of Toad Venoms from Southern Amazon, Brazil

The drug-resistance of malaria parasites is the main problem in the disease control. The huge Brazilian biodiversity promotes the search for new compounds, where the animal kingdom is proving to be a promising source of bioactive compounds. The main objective of this study was to evaluate the antiplasmodial and cytotoxic activity of the compounds obtained from the toad venoms of Brazilian Amazon. Toad venoms were collected from the secretion of Rhinella marina and Rhaebo guttatus in Mato Grosso State, Brazil. The powder was extracted at room temperature, yielding 2 extracts (RG and RM) and a substance ('1') identified as a bufadienolide, named telocinobufagin. Growth inhibition, intraerythrocytic development, and parasite morphology were evaluated in culture by microscopic observations of Giemsa-stained thin blood films. Cytotoxicity was determined against HepG2 and BGM cells by MTT and neutral red assays. The 2 extracts and the pure substance ('1') tested were active against chloroquine-resistant Plasmodium falciparum strain, demonstrating lower IC50 values. In cytotoxic tests, the 2 extracts and substance '1' showed pronounced lethal effects on chloroquine-resistant P. faciparum strain and low cytotoxic effect, highlighting toad parotoid gland secretions as a promising source of novel lead antiplasmodial compounds.