Upregulation of NRF2 through autophagy/ERK 1/2 ameliorates ionizing radiation induced cell death of human osteosarcoma U-2 OS

Nrf2: A promising therapeutic target in bone-related diseases

Nuclear factor erythroid-2-related factor 2 (Nrf2) plays an important role in maintaining cellular homeostasis, as it suppresses cell damage caused by external stimuli by regulating the transcription of intracellular defense-related genes. Accumulating evidence has highlighted the crucial role of reduction-oxidation (REDOX) imbalance in the development of bone-related diseases. Nrf2, a transcription factor linked to nuclear factor-erythrocyte 2, plays a pivotal role in the regulation of oxidative stress and induction of antioxidant defenses. Therefore, further investigation of the mechanism and function of Nrf2 in bone-related diseases is essential. Considerable evidence suggests that increased nuclear transcription of Nrf2 in response to external stimuli promotes the expression of intracellular antioxidant-related genes, which in turn leads to the inhibition of bone remodeling imbalance, improved fracture recovery, reduced occurrence of osteoarthritis, and greater tumor resistance. Certain natural extracts can selectively target Nrf2, potentially offering therapeutic benefits for osteogenic arthropathy. In this article, the biological characteristics of Nrf2 are reviewed, the intricate interplay between Nrf2-regulated REDOX imbalance and bone-related diseases is explored, and the potential preventive and protective effects of natural products targeting Nrf2 in these diseases are elucidated. A comprehensive understanding of the role of Nrf2 in the development of bone-related diseases provides valuable insights into clinical interventions and can facilitate the discovery of novel Nrf2-targeting drugs.

Autophagy Modulation as a Potential Therapeutic Strategy in Osteosarcoma: Current Insights and Future Perspectives

Autophagy, the process that enables the recycling and degradation of cellular components, is essential for homeostasis, which occurs in response to various types of stress. Autophagy plays an important role in the genesis and evolution of osteosarcoma (OS). The conventional treatment of OS has limitations and is not always effective at controlling the disease. Therefore, numerous researchers have analyzed how controlling autophagy could be used as a treatment or strategy to reverse resistance to therapy in OS. They highlight how the inhibition of autophagy improves the efficacy of chemotherapeutic treatments and how the promotion of autophagy could prove positive in OS therapy. The modulation of autophagy can also be directed against OS stem cells, improving treatment efficacy and preventing cancer recurrence. Despite promising findings, future studies are needed to elucidate the molecular mechanisms of autophagy and its relationship to OS, as well as the mechanisms underlying the functioning of autophagic modulators. Careful evaluation is required as autophagy modulation may have adverse effects on normal cells, and the optimization of autophagic modulators for use as drugs in OS is imperative.

Autophagy and its role in osteosarcoma

Osteosarcoma (OS) is the most common bone malignancy and preferably occurs in children and adolescents. Despite significant advances in surgery and chemotherapy for OS over the past few years, overall survival rates of OS have reached a bottleneck. Thus, extensive researches aimed at developing new therapeutic targets for OS are urgently needed. Autophagy, a conserved process which allows cells to recycle altered or unused organelles and cellular components, has been proven to play a critical role in multiple biological processes in OS. In this article, we summarized the association between autophagy and proliferation, metastasis, chemotherapy, radiotherapy, and immunotherapy of OS, revealing that autophagy-related genes and pathways could serve as potential targets for OS therapy.

NRF2 and the Moirai: Life and Death Decisions on Cell Fates

Significance: The transcription factor NRF2 (NF-E2-related factor 2) plays an important role as a master regulator of the cellular defense system by activating transcriptional programs of NRF2 target genes encoding multiple enzymes related to cellular redox balance and xenobiotic detoxication. Comprehensive transcriptional analyses continue to reveal an ever-broadening range of NRF2 target genes, demonstrating the sophistication and diversification of NRF2 biological signatures beyond its canonical cytoprotective roles. Recent Advances: Accumulating evidence indicates that NRF2 has a strong association with the regulation of cell fates by influencing key processes of cellular transitions in the three major phases of the life cycle of the cell (i.e., cell birth, cell differentiation, and cell death). The molecular integration of NRF2 signaling into this regulatory program occurs through a wide range of NRF2 target genes encompassing canonical functions and those manipulating cell fate pathways. Critical Issues: A singular focus on NRF2 signaling for dissecting its actions limits in-depth understanding of its intersection with the molecular machinery of cell fate determinations. Compensatory responses of downstream pathways governed by NRF2 executed by a variety of transcription factors and multifactorial signaling crosstalk require further exploration. Future Directions: Further investigations using optimized in vivo models and active engagement of overarching approaches to probe the interplay of widespread pathways are needed to study the properties and capabilities of NRF2 signaling as a part of a large network within the cell fate regulatory domain. Antioxid. Redox Signal. 38, 684-708.

Radiosensitization by the Selective Pan-FGFR Inhibitor LY2874455

Ionizing radiation activates cytoprotective pathways in cancer cells. Fibroblast growth factor receptor (FGFR) is a key player in these pathways. Thus, FGFR signaling is a potential target to induce radiosensitization. LY2874455 is an orally administrable selective pan-FGFR inhibitor. However, the radiosensitizing effects of LY2874455 remain unclear. In this study, we addressed this issue by using radioresistant human cancer cell lines H1703 (FGFR1 mutant), A549 (FGFR1–4 wild-type), and H1299 (FGFR1–4 wild-type). At an X-ray dose corresponding to 50%-clonogenic survival as the endpoint, 100 nM LY2874455 increased the sensitivity of H1703, A549, and H1299 cells by 31%, 62%, and 53%, respectively. The combination of X-rays and LY2874455 led to a marked induction of mitotic catastrophe, a hallmark of radiation-induced cell death. Furthermore, combination treatment suppressed the growth of A549 xenografts to a significantly greater extent than either X-rays or the drug alone without noticeable toxicity. This is the first report to show the radiosensitizing effect of a selective pan-FGFR inhibitor. These data suggest the potential efficacy of LY2874455 as a radiosensitizer, warranting clinical validation.

MAFG-driven osteosarcoma cell progression is inhibited by a novel miRNA miR-4660

Osteosarcoma (OS) is the most common primary bone malignancy in the adolescent population. MAFG (v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog G) forms a heterodimer with Nrf2 (NF-E2-related factor 2), binding to antioxidant response element (ARE), which is required for Nrf2 signaling activation. We found that MAFG mRNA and protein expression is significantly elevated in human OS tissues as well as in established and primary human OS cells. In human OS cells, MAGF silencing or knockout (KO) largely inhibited OS cell growth, proliferation, and migration, simultaneously inducing oxidative injury and apoptosis activation. Conversely, ectopic overexpression of MAFG augmented OS cell progression in vitro. MicroRNA-4660 (miR-4660) directly binds the 3′ untranslated region (UTR) of MAFG mRNA in the cytoplasm of OS cells. MAFG 3′ UTR luciferase activity and expression as well as OS cell growth were largely inhibited with forced miR-4660 overexpression but augmented with miR-4660 inhibition. In vivo, MAGF short hairpin RNA (shRNA) or forced overexpression of miR-4660 inhibited subcutaneous OS xenograft growth in severe combined immunodeficient mice. Furthermore, MAFG silencing or miR-4660 overexpression inhibited OS xenograft in situ growth in proximal tibia of the nude mice. In summary, MAFG overexpression-driven OS cell progression is inhibited by miR-4660. The miR-4660-MAFG axis could be novel therapeutic target for human OS.

Recent Insights into Therapy Resistance in Osteosarcoma

Osteosarcoma, the most common bone malignancy of childhood, has been a challenge to treat and cure. Standard chemotherapy regimens work well for many patients, but there remain minimal options for patients with progressive or resistant disease, as clinical trials over recent decades have failed to significantly improve survival. A better understanding of therapy resistance is necessary to improve current treatments and design new strategies for future treatment options. In this review, we discuss known mechanisms and recent scientific advancements regarding osteosarcoma and its patterns of resistance against chemotherapy, radiation, and other newly-introduced therapeutics.

Diallyl trisulfide regulates cell apoptosis and invasion in human osteosarcoma U2OS cells through regulating PI3K/AKT/GSK3β signaling pathway

AIMS

To investigate the effects and the mechanisms of action of Diallyl trisulfide (DATS) on the proliferation and metastasis of human osteosarcoma (OS) U2OS.

METHODS

U2OS cells were treated by different concentrations of DATS at different time points. Cell proliferations were measured by MTT assay. DATS induced cell cycle distribution and apoptosis were evaluated by flow cytometry (FCM) with Annexin-V. Cell migration and invasion were detected by wound healing assay and transwell assay. The effects of DATS in U2OS cell growth and metastasis were also detected in a mouse OS xenograft model.

RESULTS

A time- and concentration-dependent cytotoxic effect of DATS was observed in U2OS cells. FCM with PI staining and Annexin-V -FITC indicated that DATS induces apoptosis and a G0/G1 cell cycle arrest of U2OS cells at all concentrations from 25 μmol/l to 100 μmol/l. DATS also inhibits the migration and invasion of U2OS cells. Western blot showed that the expression levels of p-AKT, p-GSK3β, Bcl-2, Vimentin and β-catenin were decreased, while the expression levels of Bad, Bax and E-cadherin were significantly increased in DATS treated U2OS cells. Analysis using a mouse xenograft model indicated that xenografts of DATS treatment group had a significant decrease in tumor volume and weight compared to the control group. Lung metastasis models in mice demonstrated that treatment of DATS inhibits lung metastasis of OS in vivo.

CONCLUSIONS

These data suggested that DATS inhibits OS development and progression through the regulation of PI3K/AKT/GSK3β signaling pathways, accompanied by downregulation of Bcl-2, Vimentin and β-catenin, as well as upregulation of Bad, Bax and E-cadherin. Therefore, our data demonstrated that DATS exerted its anticancer effects by inhibiting cell proliferation, migration and invasion in vitro and in vivo. These results provide evidence for the use of the natural product DATS either alone or in combination with standard therapy for OS.

Dual effects of active ERK in cancer: A potential target for enhancing radiosensitivity

Ionizing radiation (IR) is an important cancer treatment approach. However, radioresistance eventually occurs, resulting in poor outcomes in patients with cancer. Radioresistance is associated with multiple signaling pathways, particularly pro-survival signaling pathways. The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade is an important signaling pathway that initiates several cellular processes and is regulated by various stimuli, including IR. Although numerous studies have demonstrated the pro-survival effects of active ERK, activation of ERK has also been associated with cell death, indicating that radiosensitization may occur by ERK stimulation. In this context, the present review describes the associations between ERK signaling, cancer and IR, and discusses the association between ERK and its pro-survival function in cancer cells, including stimuli, molecular mechanisms, clinical use of inhibitors and underlying limitations. Additionally, the present review introduces the view that active ERK may induce cell death, and describes the potential factors associated with this process. This review describes the various outcomes induced by active ERK to prompt future studies to aim to enhance radiosensitivity in the treatment of cancer.

PLK1 contributes to autophagy by regulating MYC stabilization in osteosarcoma cells

Background

PLK1, a typical PLK protein, is the main driver of cancer cell growth and proliferation. It is an inhibitor of the protein kinases that is currently being investigated in clinical studies. It is often used as a tumor marker, as high PLK1 expression correlates with poor prognosis in cancer. Overexpression of MYC is a hallmark of many human cancers. MYC modulates the transcription of thousands of genes that required to coordinate a series of cellular processes, including those essential for growth, proliferation, differentiation, self-renewal and apoptosis. To date, functions of PLK1 and MYC on tumor are mostly studied in separate researches, and studies on their mutual crosstalk are lacking.

Purpose

To investigate the mechanism of PLK1 and MYC in regulating progress of osteosarcoma.

Methods

Protein level was examined using Western blot. Animal experiments were performed with female FOX CHASE severe combined immunodeficient mice. Mice were randomly divided into experimental or control groups.

Results

PLK1 or MYC promoted the proliferation of osteosarcoma cells through the autophagy pathway. PLK1 contributed to MYC protein stabilization. PLK1 inhibition enhanced MYC degradation in osteosarcoma cells. PLK1 inhibition led to a marked decline in MYC protein abundance. The representative MYC target genes were deregulated by PLK1 inhibitors. BI2536 treatment caused a significant delay in xenograft tumor growth in mice injected with U-2 OS cells subcutaneously, with lower mean tumor weight compared to the control group.

Conclusion

PLK1 is crucial for MYC stabilization. It promotes cell proliferation by autophagy pathway in osteosarcoma cells. Data validate PLK1 as a potential therapeutic target in osteosarcoma caused by MYC-amplified.

A novel role for NFIA in restoring radiosensitivity in radioresistant NSCLC cells by downregulating the AKT and ERK pathways

Radioresistance remains the most challenging issue leading to radiotherapy failure in the treatment of non-small cell lung cancer (NSCLC). The nuclear factor IA (NFIA) is associated with tumor response to treatments in many cancers, but its role in NSCLC radioresistance remains unclear. Here, we established two radioresistant NSCLC cell lines, H226R and H460R, by dose-gradient irradiation to investigate the function of NFIA in NSCLC radioresistance. The results showed a dramatically reduced expression of NFIA in radioresistant cells accompanied with elevated phosphorylation of AKT and ERK, when compared with their parental cells. Overexpression of NFIA restored the sensitivity of radioresistant cells to radiation through increased ionizing radiation (IR)-induced apoptosis and DNA damage by downregulating p-AKT and p-ERK, whereas knockdown of NFIA promoted radioresistance of the parental cells. Our findings suggested that NFIA enhanced cell radiosensitivity by downregulating p-AKT and p-ERK in NSCLC. Our study fills a gap in the field of NFIA and radioresistance, and establishes a mechanistic foundation to improve radiotherapy efficiency in NSCLC patients.

Nuclear factor (erythroid-derived 2)-like 2 antioxidative response mitigates cytoplasmic radiation-induced DNA double-strand breaks

It has been reported that DNA double-strand breaks (DSB) can be induced by cytoplasm irradiation, and that both reactive free radicals and mitochondria are involved in DSB formation. However, the cellular antioxidative responses that are stimulated and the biological consequences of cytoplasmic irradiation remain unknown. Using the Single Particle Irradiation system to Cell (SPICE) proton microbeam facility at the National Institute of Radiological Sciences ([NIRS] Japan), the response of nuclear factor (erythroid-derived 2)-like 2 (NRF2) antioxidative signaling to cytoplasmic irradiation was studied in normal human lung fibroblast WI-38 cells. Cytoplasmic irradiation stimulated the localization of NRF2 to the nucleus and the expression of its target protein, heme oxygenase 1. Activation of NRF2 by tert-butylhydroquinone mitigated the levels of DSB induced by cytoplasmic irradiation. Mitochondrial fragmentation was also promoted by cytoplasmic irradiation, and treatment with mitochondrial division inhibitor 1 (Mdivi-1) suppressed cytoplasmic irradiation-induced NRF2 activation and aggravated DSB formation. Furthermore, p53 contributed to the induction of mitochondrial fragmentation and activation of NRF2, although the expression of p53 was significantly downregulated by cytoplasmic irradiation. Finally, mitochondrial superoxide (MitoSOX) production was enhanced under cytoplasmic irradiation, and use of the MitoSOX scavenger mitoTEMPOL indicated that MitoSOX caused alterations in p53 expression, mitochondrial dynamics, and NRF2 activation. Overall, NRF2 antioxidative response is suggested to play a key role against genomic DNA damage under cytoplasmic irradiation. Additionally, the upstream regulators of NRF2 provide new clues on cytoplasmic irradiation-induced biological processes and prevention of radiation risks.

Treatment of Saos-2 osteosarcoma cells with diallyl trisulfide is associated with an increase in calreticulin expression

Diallyl trisulfide (DATS) is a natural organic sulfur compound that may be isolated from garlic and has strong anticancer activity. DATS has been demonstrated to upregulate the expression of calreticulin (CRT) in various types of human cancers, which is associated with the prognosis of cancer and its response to therapy. However, whether DATS has the same effect on human osteosarcoma cells is not known. Therefore, in the present study, Saos-2 human osteosarcoma cells were cultured with different concentrations of DATS (0, 25, 50 and 100 µmol/l) for 24 h, or with 50 µmol/l DATS for different time periods (0, 12, 24 and 36 h). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blotting and immunofluorescent staining were used to detect CRT mRNA and protein in the Saos-2 cells. Exposure to DATS changed the morphology and inhibited the growth of the Saos-2 cells, and its effects appeared to be concentration- and exposure time-dependent. The optimum concentration and exposure time of DATS were 50 µmol/l and 24 h, respectively. The levels of CRT mRNA and protein in the Saos-2 cells were significantly upregulated following exposure to DATS. The upregulation of CRT expression by DATS may be a mechanism underlying the ability of DATS to inhibit the growth of human osteosarcoma Saos-2 cells.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

A combination of resveratrol and 3,3'-diindolylmethane, a potent radioprotector

PURPOSE

Exposure to ionizing radiation causes damage to the genomic integrity and stability of the cell. Though a large number of molecules have been studied for their radioprotective capability, no single agent is available today that meets all the requirements of a good radiprotector. In this study, we have investigated a combination of Resveratrol (RSV) and 3,3'-Diindolyl methane (DIM) for its efficacy for radioprotection. It is our hypothesis that this combination that possesses less toxicity than synthetic compounds, free radical scavenging potential, and the capacity to interfere with the several of the signaling cascades that trigger damage to cell by ionizing radiation may possess good radioprotective capability.

MATERIALS AND METHODS

Mice were pre-treated with a combination of RSV and DIM and the 30-day mortality assay, endogenous antioxidant levels in intestinal mucosa, metaphase chromosomal aberrations, and micronuclei formation were assessed after exposed to ionizing radiation.

RESULTS

The dose modifying factor (DRF) obtained for RSV, DIM, and the combination is 1.15, 1.17, and 1.3, respectively. Pre-treatment of mice with the combination results in significant (***p = .001) protection of the endogenous antioxidant levels, chromosomal aberrations, micronuclei formation, after exposure to ionizing radiation.

CONCLUSIONS

Our findings suggest that pre-treatment with the combination of RSV and DIM protects effectively from the ionizing radiation-induced damage at the molecular, cellular, and tissue levels by counteracting both the direct and indirect effects.

Bioengineered NRF2-siRNA Is Effective to Interfere with NRF2 Pathways and Improve Chemosensitivity of Human Cancer Cells

The nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a transcription factor in the regulation of many oxidative enzymes and efflux transporters critical for oxidative stress and cellular defense against xenobiotics. NRF2 is dysregulated in patient osteosarcoma (OS) tissues and correlates with therapeutic outcomes. Nevertheless, research on the NRF2 regulatory pathways and its potential as a therapeutic target is limited to the use of synthetic small interfering RNA (siRNA) carrying extensive artificial modifications. Herein, we report successful high-level expression of recombinant siRNA against NRF2 in Escherichia coli using our newly established noncoding RNA bioengineering technology, which was purified to >99% homogeneity using an anion-exchange fast protein liquid chromatography method. Bioengineered NRF2-siRNA was able to significantly knock down NRF2 mRNA and protein levels in human OS 143B and MG63 cells, and subsequently suppressed the expression of NRF2-regulated oxidative enzymes [heme oxygenase-1 and NAD(P)H:quinone oxidoreductase 1] and elevated intracellular levels of reactive oxygen species. In addition, recombinant NRF2-siRNA was effective to sensitize both 143B and MG63 cells to doxorubicin, cisplatin, and sorafenib, which was associated with significant downregulation of NRF2-targeted ATP-binding cassette (ABC) efflux transporters (ABCC3, ABCC4, and ABCG2). These findings support that targeting NRF2 signaling pathways may improve the sensitivity of cancer cells to chemotherapy, and bioengineered siRNA molecules should be added to current tools for related research.