2-Methoxyestradiol-Mediated Induction of Frzb Contributes to Cell Death and Autophagy in MG63 Osteosarcoma Cells

Construction and Validation of an Autophagy-Related Prognostic Model for Osteosarcoma Patients

While the prognostic value of autophagy-related genes (ARGs) in OS patients remains scarcely known, increasing evidence is indicating that autophagy is closely associated with the development and progression of osteosarcoma (OS). Therefore, we explored the prognostic value of ARGs in OS patients and illuminate associated mechanisms in this study. When the OS patients in the training/validation cohort were stratified into high- and low-risk groups according to the risk model established using least absolute shrinkage and selection operator (LASSO) regression analysis, we observed that patients in the low-risk group possessed better prognosis (P < 0.0001). Univariate/Multivariate COX regression and subgroup analysis demonstrated that the ARGs-based risk model was an independent survival indicator for OS patients. The nomogram incorporating the risk model and clinical features exhibited excellent prognostic accuracy. GO, KEGG, and GSVA analyses collectively indicated that bone development-associated pathway mediated the contribution of ARGs to the malignance of OS. Immune infiltration analysis suggested the potential pivotal role of macrophage in OS. In summary, the risk model based on 12 ARGs possessed potent capacity in predicting the prognosis of OS patients. Our work may assist clinicians to map out more reasonable treatment strategies and facilitate individual-targeted therapy in osteosarcoma.

The apoptotic effects of progesterone on breast cancer (MCF-7) and human osteosarcoma (MG-636) cells

Purpose

Progesterone has been reported to inhibit the proliferation of breast cancer and osteosarcoma cells; however, its inhibitory mechanism has not yet been clarified. The aim of the present study was to clarify the effects of progesterone on apoptosis in breast cancer (MCF-7) and human osteosarcoma (MG-63) cells.

Materials and methods

In this experimental study the cytotoxic effect of progesterone was measured in MCF-7 and MG-63 cells exposed to different concentrations of progesterone using MTT assay, and effective concentrations were identified. The expression levels of the Bax, P53 and Bcl-2 genes were evaluated by real-time PCR, and caspase-3, 8 and 9 activity levels were determined using a colorimetric method. Hoechst staining and flow cytometry were used to confirm apoptosis. The data were statistically analyzed using one-way analysis of variance (ANOVA) and independent-samples t-test.

Results

Compared to the control group, we observed a significant increase in the expression levels of the Bax and P53 genes and the activity levels of caspase-3 and 9, and a significant decrease in the expression level of the Bcl-2 gene in MCF-7 and MG-63 treated with effective concentration of progesterone. The caspase-8 activity level did not change significantly in treated MG-63 but increased in treated MCF-7 cells. Hoechst staining and flow cytometry results confirmed apoptosis in the cells exposed to effective concentration of progesterone.

Conclusions

The cytotoxic effect of progesterone on breast cancer and osteosarcoma cells was mediated by apoptotic pathways. In this context, progesterone triggers the extrinsic and intrinsic apoptotic pathways in MCF-7 cells and induces the intrinsic apoptotic pathway in MG-63 cells.

Secreted Frizzled-related proteins (sFRPs) in osteo-articular diseases: much more than simple antagonists of Wnt signaling?

Osteo-articular diseases are characterized by a dysregulation of joint and/or bone homeostasis. These include diseases affecting the joints originally, such as osteoarthritis and rheumatoid arthritis, or the bone, such as osteoporosis. Inflammation and the involvement of Wingless-related integration site (Wnt) signaling pathways are key pathophysiological features of these diseases resulting in tissue degradation by matrix-degrading enzymes, namely matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases with thrombospondin motifs (ADAMTs), secreted by the joint resident cells and/or by infiltrating immune cells. Activation of Wnt signaling pathways is modulated by different families of proteins, including Dickkopfs and the secreted Frizzled-related proteins (sFRPs). The sFRP family is composed of five secreted glycoproteins in mammals that regulate Wnt signaling in the extracellular compartment. Indeed, sFRPs are able to bind both to the soluble Wnt ligands and to their cell membrane receptors, the Frizzled proteins. Their expression profile is altered in osteo-articular diseases, suggesting that they could account for the abnormal activation of Wnt pathways. In the present article, we review how sFRPs are more than simple antagonists of the Wnt signaling pathways and discuss their pathophysiological relevance in the context of osteo-articular diseases. We detail their Wnt-dependent and their Wnt-independent roles, with a particular emphasis on their ability to modulate the inflammatory response and extracellular matrix (ECM) remodeling. We also discuss their potential therapeutic use with a focus on bone remodeling, osteo-articular cancers, and tissue engineering.

2-Methoxyestradiol and Its Combination with a Natural Compound, Ferulic Acid, Induces Melanoma Cell Death via Downregulation of Hsp60 and Hsp90

Melanoma is an aggressive type of skin cancer with one of the highest mortality rates. Notably, its incidence in the last few decades has increased faster than any other cancer. Therefore, searching for novel anticancer therapies is of great clinical importance. In the present study, we investigated the anticancer potential of 2-methoxyestradiol, potent chemotherapeutic, in the A375 melanoma cellular model. In order to furthermore evaluate the anticancer efficacy of 2-methoxyestradiol, we have additionally combined the treatment with a naturally occurring polyphenol, ferulic acid. The results were obtained using the melanoma A375 cellular model. In the study, we used MTT assay, flow cytometry, and western blot techniques. Herein, we have evidenced that the molecular mechanism of action of 2-methoxyestradiol and ferulic acid is partly related to the reduction of Hsp60 and Hsp90 levels and the induction of nitric oxide in the A375 melanoma cell model, while no changes were observed in Hsp70 expression after 2-methoxyestradiol and ferulic acid treatment separately or in combination. This is especially important in case of chemoresistance mechanisms because the accumulation of Hsp70 reduces induction of cancer cell death, thus decreasing antitumour efficacy.

STIM1 expression is associated with osteosarcoma cell survival

Objective

To examine the role of store-operated calcium entry (SOCE) and stromal interaction molecule 1 (STIM1) in survival and migration of osteosarcoma cells and investigate what blockade of store-operated Ca²⁺ contributes to the regulation of osteosarcoma cells.

Methods

First, we examined the expression levels of STIM1 in osteosarcoma cell lines by Western analysis and in tissue specimens by immunohistochemistry. Second, we investigated the effect of SOCE and STIM1 on osteosarcoma cell viability using MTS assays and on cell proliferation using colony formation. Third, we investigated the role of SOCE and STIM1 in cell migration using wound healing assays and Boyden chamber assays. Finally, we studied the effect of SOCE on the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) activity by luciferase assays.

Results

STIM1 was overexpressed in osteosarcoma cell lines and tissue specimens and was associated with poor survival of osteosarcoma patients. Also, inhibition of SOCE and STIM1 decreased the cell viability and migration of osteosarcoma cells. Furthermore, our results showed that blockade of store-operated Ca²⁺ channels involved down-regulation of NFATc1 in osteosarcoma cells.

Conclusions

STIM1 is essential for osteosarcoma cell functions, and STIM1 and Ca²⁺ entry pathway could be further explored as molecular targets in the treatment of osteosarcoma.

Inhibition of STAT3 blocks protein synthesis and tumor metastasis in osteosarcoma cells

BACKGROUND

Osteosarcoma is the most common bone cancer. Despite advances, molecular mechanisms associated with osteosarcoma have not been fully understood. Hence, an effective treatment for osteosarcoma has yet to be developed. Even though signal transducer and activator of transcription3 (STAT3) has been implicated, its role in pathogenesis of osteosarcoma is not fully determined. In this study, we investigated the antitumor effect of napabucasin (NP) (BBI608), an inhibitor of STAT3 on osteosarcoma in vitro and in vivo and studied the underlying molecular mechanism.

METHODS

Cell viability, colony formation, apoptosis, tumor growth and metastasis assays were performed to examine the effect of NP on osteosarcoma in vitro and in vivo. Real-time RT-PCR, western analysis, immunofluorescence and reporter assays were used to monitor the expression and activity of proteins and underlying molecular pathways. Protein synthesis, co-immunoprecipitation and CAP binding assays were carried out to understand NP-mediated mechanism of actions in osteosarcoma cells.

RESULTS

Our results show that NP treatment decreases cell viability and induces apoptosis in several osteosarcoma cell lines. NP treatment suppresses both expression and phosphorylation of STAT3 in addition to blocking STAT3-mediated transcription and downstream target proteins in osteosarcoma cells. Furthermore, NP inhibits protein synthesis through regulation of the eukaryotic initiation factor 4E (eIF4E) and eIF4E-binding protein 1 (4E-BP1). NP also inhibits the progression of osteosarcoma tumors and metastasis in vivo in an orthotopic tibial model of osteosarcoma.

CONCLUSIONS

Taken together, our investigation reveals that NP acts through a novel mechanism and inhibits osteosarcoma growth and metastasis, and could be investigated clinically for treating osteosarcoma patients alone or in combination with other drugs.

How does estrogen work on autophagy?

Macroautophagy/autophagy is vital for intracellular quality control and homeostasis. Therefore, careful regulation of autophagy is very important. In the past 10 years, a number of studies have reported that estrogenic effectors affect autophagy. However, some results, especially those regarding the modulatory effect of 17β-estradiol (E2) on autophagy seem inconsistent. Moreover, several clinical trials are already in place combining both autophagy inducers and autophagy inhibitors with endocrine therapies for breast cancer. Not all patients experience benefit, which further confuses and complicates our understanding of the main effects of autophagy in estrogen-related cancer. In view of the importance of the crosstalk between estrogen signaling and autophagy, this review summarizes the estrogenic effectors reported to affect autophagy, subcellular distribution and translocation of estrogen receptors, autophagy-targeted transcription factors (TFs), miRNAs, and histone modifications regulated by E2. Upon stimulation with estrogen, there will always be opposing functional actions, which might occur between different receptors, receptors on TFs, TFs on autophagy genes, or even histone modifications on transcription. The huge signaling network downstream of estrogen can promote autophagy and reduce overstimulated autophagy at the same time, which allows autophagy to be regulated by estrogen in a restricted range. To help understand how the estrogenic regulation of autophagy affects cell fate, a hypothetical model is presented here. Finally, we discuss some exciting new directions in the field. We hope this might help to better understand the multiple associations between estrogen and autophagy, the pathogenic mechanisms of many estrogen-related diseases, and to design novel and efficacious therapeutics. Abbreviations: AP-1, activator protein-1; HATs, histone acetyltransferases; HDAC, histone deacetylases; HOTAIR, HOX transcript antisense RNA.

2-Methoxyestradiol Reverses the Pro-Carcinogenic Effect of L-Lactate in Osteosarcoma 143B Cells

BACKGROUND/AIM

According to the reverse Warburg effect, tumor cells may metabolize lactate as an energy source and shuttle L-lactate to neighboring cancer cells, adjacent stroma, and vascular endothelial cells, thus inducing metabolic reprogramming. An increased tumor L-lactate level strictly correlates with increased metastasis, tumor recurrence and a poor outcome. A potent anticancer agent that may act on L-lactate activated cells is 2-metoxyestradiol. Thus, the aim of the study was to evaluate whether a potent anticancer agent, 2-methoxyestradiol, is able to reverse L-lactate-induced metabolic reprogramming in osteosarcoma 143B cells.

MATERIALS AND METHODS

We used flow cytometry in order to determine cell death, autophagy, expression of KI-67, mitochondrial membrane depolarization. We performed cell proliferation assay in order to determine cell viability and cell migration assay to determine invasive potential of osteosarcoma cells. While, CalcuSyn software was used in order to evaluate the interaction between 2-methoxyestradiol and L-lactate.

RESULTS

We demonstrated that 2-methoxyestradiol abolished L-lactate-induced migration and proliferation of osteosarcoma cells. Moreover, we observed that this effect was associated with regulation of Ki-67 and induction of autophagy.

CONCLUSION

2-Methoxyestradiol is a potent anticancer agent also under metabolic reprogramming conditions.

Decreased local and systemic levels of sFRP3 protein in osteosarcoma patients

Osteosarcoma is a malignant bone tumor that occurs mainly in children and adolescents. Because Wnt signaling has been implicated in the pathogenesis of osteosarcoma, we have investigated the circulating and local levels of the Wnt antagonist protein, Secreted Frizzled Related Protein (sFRP) 3, in osteosarcoma patients. Enzyme linked immunosorbent assay (ELISA) analysis of 67 osteosarcoma and age-matched non-diseased control sera showed that sFPR3 protein levels were significantly lower in osteosarcoma than in normal. Analysis of tumor and adjacent normal tissues (9 pairs) from osteosarcoma patients showed a decrease in sFRP3 expression in 5 out of 9 tumor samples compared to normal tissues. Furthermore, immunohistochemical analysis of tissue microarray revealed a significant decrease in sFRP3 levels in tumor compared to normal bone. RNA sequencing analysis in osteosarcoma cells shows suppression of sFRP3 and concomitant expression of multiple Wnt family members mediating canonical or non-canonical Wnt signaling. Taken together, our findings show that the systemic and local levels of sFRP3 protein are downregulated in osteosarcoma and sFRP3 levels could be explored further in the diagnosis and the care of osteosarcoma patients.

Effects of 17β-Estradiol on Mitophagy in the Murine MC3T3-E1 Osteoblast Cell Line is Mediated via G Protein-Coupled Estrogen Receptor and the ERK1/2 Signaling Pathway

Background

Osteoporosis is associated with 17β-estradiol deficiency. The G protein-coupled receptor 30 (GPR30) is known to be an estrogen-responsive receptor, but its role in the degradation of mitochondria in osteoblasts by autophagy, or mitophagy, remains unclear. The aim of this in vitro study was to evaluate the effects of 17β-estradiol, GPR30, and its signaling pathway, on mitophagy in the murine MC3T3-E1 osteoblast cell line.

Material/Methods

In the murine MC3T3-E1 osteoblast cell line, cells were treated with 17β-estradiol, or G15, a selective GPR30 antagonist, or U0126, a mitogen-activated protein (MAP) kinase (ERK1/2) inhibitor, or with vehicle as control. The expression of GPR30 was determined by Western blot, reverse transcription-polymerase chain reaction (RT-PCR), and confocal immunofluorescence imaging. Cell morphology and mitochondrial autophagosomes were identified using transmission electron microscopy (TEM). Phosphorylation of the mitophagy markers, heat shock protein 60 (Hsp60), translocase of outer membrane (Tom)20, and microtubule-associated protein 1A/1B-light chain 3 (LC3) were determined by Western blot, and cell proliferation was determined using the bromodeoxyuridine (BrdU) assay.

Results

The optimum concentration of 17β-estradiol that resulted in GPR30 expression in MC3T3-E1 cells was 10⁻⁷ M, which led to the accumulation of mitochondrial autophagosomes and increased protein phosphorylation levels of Hsp60, Tom20, and LC3. In cells pretreated with G15 or U0126, 17β-estradiol treatment did not increase mitophagy in MC3T3-E1 cells.

Conclusions

In murine osteoblasts cultured in vitro, treatment with 17β-estradiol resulted in the expression of GPR30 and enhanced mitophagy through the GPR30 and ERK1/2 signaling pathway.

Interplay Between Long Noncoding RNA ZEB1-AS1 and miR-200s Regulates Osteosarcoma Cell Proliferation and Migration

In our previous study, we found long noncoding RNA ZEB1-AS1 is upregulated and functions as an oncogene in osteosarcoma. MiR-200 family (miR-200s) functions as tumor suppressor via directly targeting ZEB1 in various cancers. In this study, we further investigate the potential interplay between ZEB1-AS1, miR-200s, and ZEB1 in osteosarcoma. Our results showed that ZEB1-AS1 functions as a molecular sponge for miR-200s and relieves the inhibition of ZEB1 caused by miR-200s. ZEB1-AS1 and miR-200s reciprocally negatively regulate each other. MiR-200s are downregulated in osteosarcoma tissues, and negatively correlated with ZEB1-AS1 and ZEB1 expression levels in osteosarcoma. Functional experiments showed that consistent with ZEB1-AS1 depletion, miR-200s overexpression and ZEB1 depletion both inhibit osteosarcoma cell proliferation and migration. Overexpression of miR-200s partially abolished the effects of ZEB1-AS1 on osteosarcoma cell proliferation and migration. Moreover, the combination of ZEB1-AS1 depletion and miR-200s overexpression significantly inhibits osteosarcoma cell proliferation and migration. In conclusion, this study revealed a novel regulatory mechanism between ZEB1-AS1, miR-200s, and ZEB1. The interplay between ZEB1-AS1 and miR-200s contributes to osteosarcoma cell proliferation and migration, and targeting this interplay could be a promising strategy for osteosarcoma treatment. J. Cell. Biochem. 118: 2250-2260, 2017. © 2017 Wiley Periodicals, Inc.