Inhibition of Autophagy Increases 2-Methoxyestradiol-Induced Cytotoxicity in SW1353 Chondrosarcoma Cells

Crosstalk Between ROS and Autophagy in Tumorigenesis: Understanding the Multifaceted Paradox

Cancer formation is a highly regulated and complex process, largely dependent on its microenvironment. This complexity highlights the need for developing novel target-based therapies depending on cancer phenotype and genotype. Autophagy, a catabolic process, removes damaged and defective cellular materials through lysosomes. It is activated in response to stress conditions such as nutrient deprivation, hypoxia, and oxidative stress. Oxidative stress is induced by excess reactive oxygen species (ROS) that are multifaceted molecules that drive several pathophysiological conditions, including cancer. Moreover, autophagy also plays a dual role, initially inhibiting tumor formation but promoting tumor progression during advanced stages. Mounting evidence has suggested an intricate crosstalk between autophagy and ROS where they can either suppress cancer formation or promote disease etiology. This review highlights the regulatory roles of autophagy and ROS from tumor induction to metastasis. We also discuss the therapeutic strategies that have been devised so far to combat cancer. Based on the review, we finally present some gap areas that could be targeted and may provide a basis for cancer suppression.

RNA-dependent protein kinase is required for interferon-γ-induced autophagy in MG63 osteosarcoma cells

Osteosarcoma is a bone tumor that mainly affects children and adolescents. Interferons (IFNs) have been shown to exert antitumor effects in osteosarcoma cells, although the molecular mechanisms have not been fully realized. We investigated IFN-γ actions on osteosarcoma cells. Our results show that IFN-γ induces the accumulation of autophagosomes in osteosarcoma cells. IFN-γ treatment leads to the conversion of autophagy marker light chain 3 (LC3)-I to LC3-II in osteosarcoma cells, and this conversion is accompanied by puncta formation. Also, IFN-γ-mediated induction of autophagosome formation and autophagic flux require RNA-dependent protein kinase (PKR) activity. In addition, our findings show that IFN-γ-mediated osteosarcoma cell death is not dependent on PKR. Our study suggests that IFN-γ has differential effects that lead to induction of cell death and autophagy in osteosarcoma cells. Further evaluation of the IFN-γ-mediated molecular mechanism could lead to improved understanding of and targeted treatment strategies for osteosarcoma.

Differential regulation of autophagy by STAU1 in alveolar rhabdomyosarcoma and non-transformed skeletal muscle cells

PURPOSE

Recent work has highlighted the therapeutic potential of targeting autophagy to modulate cell survival in a variety of diseases including cancer. Recently, we found that the RNA-binding protein Staufen1 (STAU1) is highly expressed in alveolar rhabdomyosarcoma (ARMS) and that this abnormal expression promotes tumorigenesis. Here, we asked whether STAU1 is involved in the regulation of autophagy in ARMS cells.

METHODS

We assessed the impact of STAU1 expression modulation in ARMS cell lines (RH30 and RH41), non-transformed skeletal muscle cells (C2C12) and STAU1-transgenic mice using complementary techniques.

RESULTS

We found that STAU1 silencing reduces autophagy in the ARMS cell lines RH30 and RH41, while increasing their apoptosis. Mechanistically, this inhibitory effect was found to be caused by a direct negative impact of STAU1 depletion on the stability of Beclin-1 (BECN1) and ATG16L1 mRNAs, as well as by an indirect inhibition of JNK signaling via increased expression of Dual specificity phosphatase 8 (DUSP8). Pharmacological activation of JNK or expression silencing of DUSP8 was sufficient to restore autophagy in STAU1-depleted cells. By contrast, we found that STAU1 downregulation in non-transformed skeletal muscle cells activates autophagy in a mTOR-dependent manner, without promoting apoptosis. A similar effect was observed in skeletal muscles obtained from STAU1-overexpressing transgenic mice.

CONCLUSIONS

Together, our data indicate an effect of STAU1 on autophagy regulation in ARMS cells and its differential role in non-transformed skeletal muscle cells. Our findings suggest a cancer-specific potential of targeting STAU1 for the treatment of ARMS.

Metabolite profiling of chondrosarcoma cells: A robust GC-MS method for the analysis of endogenous metabolome

Chondrosarcoma is the 2nd most frequent bone sarcoma. In this study, the metabolic profiling of human chondrosarcoma SW-1353 cell line was investigated for the first time. To obtain more precise information about the metabolites from chondrosarcoma cells, pretreatment methods including washing steps/solvents, harvesting conditions, and extraction protocols for chondrosarcoma SW-1353 cells were evaluated in the context of metabolite profiling by GC-MS technique. In addition, a total of 32 representative metabolites (related to amino acid metabolism, TCA cycle, glycolysis, and fatty acid metabolism) were quantitatively determined. We found that a fast water rinse step before metabolic quenching, may reduce the contaminants and improve sensitivity. Trypsin/ethylene diamine tetraacetic acid treatment led to a large amount of metabolite leakage, which was not suitable for metabolomics research. Methanol was selected as a more suitable extraction solvent among four extraction approaches applied to SW-1353 cells. The final protocol can provide a simple, robust, and reproducible method to obtain precise information about the metabolites from chondrosarcoma cells, which is helpful to further understand the chondrosarcoma cell physiology and the mechanism of drug resistance in this disease, from the perspective of metabolomics.

STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy

Schwann cells are the main supportive cells of the peripheral nerves. Schwann cells suffer inhibition of autophagy under hyperglycemia treatment in diabetic peripheral neuropathy (DPN). However, the exact mechanism is still not fully elucidated. We first observed the decrease of autophagy markers (LC3-II/LC3-I, P62) in the sciatic nerves of diabetic mice vs. normal mice, accompanied with the loss of myelinated nerve fibers and abnormal myelin sheath. In line with this, LC3-II/LC3-I and P62 were also significantly reduced in high glucose-treated rat Schwann cell 96 (RSC96) cells compared with normal glucose-treated cells. Furthermore, we found that trichostatin A [an inhibitor of histone deacetylase (HDAC)] evidently improved LC3-II/LC3-I in high glucose-treated RSC96 cells, without an effect on P62 expression. Again, HDAC1 and HDAC5 were revealed to be increased in RSC96 cells stimulated with high glucose. Inhibition of HDAC1 but not HDAC5 by small hairpin RNA vector enhanced LC3-II/LC3-I in high glucose-cultured RSC96 cells. In addition, LC3-II conversion regulators [autophagy-related protein (Atg)3, Atg5, and Atg7] were detected in high glucose-treated and HDAC1-knockdown RSC96 cells, and Atg3 was proven to be the key target of HDAC1. The presuppression of Atg3 offset the improvement of LC3-II/LC3-I resulting from HDAC1 inhibition in high glucose-treated RSC96 cells. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway was activated in RSC96 cells treated with high glucose, which was indicated by increased STAT3 phosphorylation. Blocking STAT3 phosphorylation by chemical inhibitor AG490 induced HDAC1 down-regulation followed by increases in Atg3 and LC3-II/LC3-I. Interestingly, we also found that AG490 treatment enhanced P62 expression in high glucose-stimulated RSC96 cells. Taken together, our findings demonstrate that hyperglycemia inhibits LC3-II/LC3-I in an HDAC1-Atg3-dependent manner and decreases P62 expression in an HDAC-independent manner via the JAK-STAT3 signaling pathway in the Schwann cells of DPN.-Du, W., Wang, N., Li, F. Jia, K., An, J., Liu, Y., Wang, Y., Zhu, L., Zhao, S. Hao, J. STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy.

Chondrosarcoma: An overview of clinical behavior, molecular mechanisms mediated drug resistance and potential therapeutic targets

Sarcomas are known as a heterogeneous class of cancers arisen in the connective tissues and demonstrated various histological subtypes including both soft tissue and bone origin. Chondrosarcoma is one of the main types of bone sarcoma that shows a considerable deficiency in response to chemotherapy and radiotherapy. While conventional treatment based on surgery, chemo-and radiotherapy are used in this tumor, high rate of death especially among children and adolescents are reported. Due to high resistance to current conventional therapies in chondrosarcoma, there is an urgent requirement to recognize factors causing resistance and discover new strategies for optimal treatment. In the past decade, dysregulation of genes associated with tumor development and therapy resistance has been studied to find potential therapeutic targets to overcome resistance. In this review, clinical aspects of chondrosarcoma are summarized. Moreover, it gives a summary of gene dysregulation, mutation, histone modifications and non-coding RNAs associated with tumor development and therapeutic response modulation. Finally, the probable role of tumor microenvironment in chondrosarcoma drug resistance and targeted therapies as a promising molecular therapeutic approach are summarized.

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.

22-oxacalcitriol prevents acute kidney injury via inhibition of apoptosis and enhancement of autophagy

BACKGROUND

The pathophysiology of ischemic acute kidney injury (AKI) is thought to include a complex interplay between tubular cell damage and regeneration. Several lines of evidences suggest a potential renoprotective effect of vitamin D. In this study, we investigated the effect of 22-oxacalcitriol (OCT), a synthetic vitamin D analogue, on renal fate in a rat model of ischemia reperfusion injury (IRI) induced acute kidney injury (AKI).

METHODS

22-oxacalcitriol (OCT) was administered via intraperitoneal (IP) injection before ischemia, and continued after IRI that was performed through bilateral clamping of the renal pedicles. 96 h after reperfusion, rats were sacrificed for the evaluation of autophagy, apoptosis, and cell cycle arrest. Additionally, assessments of toll-like receptors (TLR), interferon gamma (IFN-g) and sodium-hydrogen exchanger-1 (NHE-1) were also performed to examine their relations to OCT-mediated cell response.

RESULTS

Treatment with OCT-attenuated functional deterioration and histological damage in IRI induced AKI, and significantly decreased cell apoptosis and fibrosis. In comparison with IRI rats, OCT + IRI rats manifested a significant exacerbation of autophagy as well as reduced cell cycle arrest. Moreover, the administration of OCT decreased IRI-induced upregulation of TLR4, IFN-g and NHE-1.

CONCLUSION

These results demonstrate that treatment with OCT has a renoprotective effect in ischemic AKI, possibly by suppressing cell loss. Changes in the expression of IFN-g and NHE-1 could partially link OCT to the cell survival-promoted effects.

Modes of cell death induced by tetrahydroisoquinoline-based analogs in MDA-MB-231 breast and A549 lung cancer cell lines

Background

A and B rings of the steroidal microtubule disruptor, 2-methoxyestradiol, and its analogs can be mimicked with a tetrahydroisoquinoline (THIQ) core. THIQs are cytotoxic agents with potential anticancer activities. The aim of this in vitro study was to investigate the modes of cell death induced by four nonsteroidal THIQ-based analogs, such as STX 2895, STX 3329, STX 3451 and STX 3450, on MDA-MB-231 metastatic breast and A549 epithelial lung carcinoma cells.

Materials and methods

Cytotoxicity studies determined the half-maximal growth inhibitory concentration of the analogs to be at nanomolar concentrations without the induction of necrosis. Light and fluorescent microscopy determined that compounds caused microtubule depolymerization and displayed morphological hallmarks of apoptosis.

Results

Flow cytometric analyses confirmed apoptosis induction as well as an increased G₂/M phase on cell cycle analysis. Furthermore, intrinsic pathway signaling was implicated due to increased cytochrome c release and a decrease in mitochondrial transmembrane potential. Potential involvement of autophagy was observed due to increased acidic vacuole formation and increased aggresome activation factor.

Conclusion

Thus, it can be concluded that these four THIQ-based analogs exert anti-proliferative and antimitotic effects, induce apoptosis and involve autophagic processes. Further investigation into the efficacy of these potential anticancer drugs will be conducted in vitro and in vivo.

Spheroid-based 3D cell cultures identify salinomycin as a promising drug for the treatment of chondrosarcoma

Chondrosarcoma (CS) is a cartilage malignancy of adulthood that is treated by surgery alone, since chemotherapy is considered ineffective. Unfortunately, a large proportion of patients with CS develop lung metastases, and several die of the disease. In this study, we compared 3D-spheroid cultures and conventional cell monolayer models in order to identify the best way to select anticancer agents that could be effective for the systemic control of CS. Using SW1353 cells, we developed a three-dimensional (3D) in vitro culture model to mimic in vivo features of CS microenvironment and evaluated the efficacy of different drugs to modulate CS cell proliferation and survival in 2D versus 3D-cultures. Doxorubicin (DXR) and cisplatin, that are widely employed in sarcomas, were less effective on 3D-CS spheroids when compared to standard monolayer models, whereas treatment with the ionophore salinomycin (SAL) had a strong cytotoxic effect both on 2D and 3D-cultures. Furthermore, as demonstrated by the reduced viability and the enhanced DXR nuclear localization, SAL enhanced DXR cytotoxicity in 3D-CS spheroids also at sub-lethal doses. SAL activity on 3D-CS spheroids was mediated by a significant induction of apoptosis via caspase activation. This study demonstrates that preclinical tests significantly differ in monolayer and 3D cultures of CS cells. Using this approach, SAL, alone or, at sub-lethal concentrations, in combination with DXR, represents a promising agent for the systemic treatment of CS. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Autophagy as a potential target for sarcoma treatment

Autophagy is a constitutively active, evolutionary conserved, catabolic process for maintaining homeostasis in cellular stress responses and cell survival. Although its mechanism has not been fully illustrated, recent work on autophagy in various types of sarcomas has demonstrated that autophagy exerts an important role in sarcoma cell growth and proliferation, in pro-survival response to therapies and stresses, and in therapeutic resistance of sarcoma. Thus, the autophagic process is being seen as a possibly novel therapeutic target of sarcoma. Additionally, some co-regulators of autophagy have also been investigated as promising biomarkers for the diagnosis and prognosis of sarcoma. In this review, we summarize contemporary advances in the role of autophagy in sarcoma and discuss the potential of autophagy as a new target for sarcoma treatment.

Autophagy activation protects shock wave induced renal tubular epithelial cell apoptosis may through modulation of Akt/ GSK-3β pathway

Purpose: Extracorporeal shock wave lithotripsy (ESWL) is well documented to exert destructive effect to renal cells and its mechanism is not clear. Autophagy is one of cell basic response for stressful conditions and it is important to determine cell's fate. The aim of this study is to elucidate the role of autophagy in the process of shock wave-induced renal cells injury.

Methods: NRK-52E cell, a rat renal tubular epithelial cell, was exposed to shock wave at the voltage of 14KV. GFP-LC3 puncta was used to monitor Autophagy flux in the process of shock wave injury. Autophagic relative proteins, such as light chain 3 (LC3), beclin-1 and p62, were also examined. Cell variability and apoptosis were detected when inhibition autophagy with 3-methyladenine (3MA) or stimulating its activity with rapamycin during the process of shock wave injury. The role of Akt/ GSK-3β and its connection with autophagy in the process of shock wave injury were also investigated.

Results: Shock wave was confirmed to activate autophagy in renal cells, which was manifested in LC3-II turnover, beclin-1 induction and degradation of p62. Inhibition autophagy enhanced cell damage or apoptosis, whereas its stimulating was able to exert protection from shock wave injury. Akt/ GSK-3β, a cell-survival signaling pathway, can also be activated during the process. And its activation could be suppressed by blockade autophagy.

Conclusion: Autophagy is a self-protective response for renal cells from shock wave injury. The cyto-protection of autophagy may be connected with modulation Akt/ GSK-3β pathway.