Antitumor activity of Raddeanin A is mediated by Jun amino-terminal kinase activation and signal transducer and activator of transcription 3 inhibition in human osteosarcoma

Amicis Omnia Sunt Communia: NF-κB Inhibition as an Alternative to Overcome Osteosarcoma Heterogeneity

Tumor heterogeneity poses a significant challenge in osteosarcoma (OS) treatment. In this regard, the "omics" era has constantly expanded our understanding of biomarkers and altered signaling pathways (i.e., PI3K/AKT/mTOR, WNT/β-catenin, NOTCH, SHH/GLI, among others) involved in OS pathophysiology. Despite different players and complexities, many commonalities have been described, among which the nuclear factor kappa B (NF-κB) stands out. Its altered activation is pervasive in cancer, with pleiotropic action on many disease-relevant traits. Thus, in the scope of this article, we highlight the evidence of NF-κB dysregulation in OS and its integration with other cancer-related pathways while we summarize the repertoire of compounds that have been described to interfere with its action. In silico strategies were used to demonstrate that NF-κB is closely coordinated with other commonly dysregulated signaling pathways not only by functionally interacting with several of their members but also by actively participating in the regulation of their transcription. While existing inhibitors lack selectivity or act indirectly, the therapeutic potential of targeting NF-κB is indisputable, first for its multifunctionality on most cancer hallmarks, and secondly, because, as a common downstream effector of the many dysregulated pathways influencing OS aggressiveness, it turns complex regulatory networks into a simpler picture underneath molecular heterogeneity.

Cytokine receptor-like factor 1 (CRLF1) promotes cardiac fibrosis via ERK1/2 signaling pathway

Cardiac fibrosis is a cause of morbidity and mortality in people with heart disease. Anti-fibrosis treatment is a significant therapy for heart disease, but there is still no thorough understanding of fibrotic mechanisms. This study was carried out to ascertain the functions of cytokine receptor-like factor 1 (CRLF1) in cardiac fibrosis and clarify its regulatory mechanisms. We found that CRLF1 was expressed predominantly in cardiac fibroblasts. Its expression was up-regulated not only in a mouse heart fibrotic model induced by myocardial infarction, but also in mouse and human cardiac fibroblasts provoked by transforming growth factor-‍β1 (TGF‍-‍β1). Gain- and loss-of-function experiments of CRLF1 were carried out in neonatal mice cardiac fibroblasts (NMCFs) with or without TGF-‍β1 stimulation. CRLF1 overexpression increased cell viability, collagen production, cell proliferation capacity, and myofibroblast transformation of NMCFs with or without TGF‍-‍β1 stimulation, while silencing of CRLF1 had the opposite effects. An inhibitor of the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway and different inhibitors of TGF-‍β1 signaling cascades, comprising mothers against decapentaplegic homolog (SMAD)‍-dependent and SMAD-independent pathways, were applied to investigate the mechanisms involved. CRLF1 exerted its functions by activating the ERK1/2 signaling pathway. Furthermore, the SMAD-dependent pathway, not the SMAD-independent pathway, was responsible for CRLF1 up-regulation in NMCFs treated with TGF-‍β1. In summary, activation of the TGF-‍β1/SMAD signaling pathway in cardiac fibrosis increased CRLF1 expression. CRLF1 then aggravated cardiac fibrosis by activating the ERK1/2 signaling pathway. CRLF1 could become a novel potential target for intervention and remedy of cardiac fibrosis.

A Pegylated Liposome Loaded with Raddeanin A for Prostate Cancer Therapy

Introduction

Raddeanin A (RA), a potent triterpenoid extracted from Anemone raddeana Regel, has a moderate therapeutic effect on prostate cancer (PCa), correlating with serious biological toxicity. Therefore, a RA-loaded PEGylated liposome drug delivery system was devised in this study.

Methods

Hydrogenated soybean phospholipids (HSPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-Polyethyleneglycol-2000 (sodium salt) (DSPE-PEG2k), cholesterol (CHO), and RA were utilised to prepare a RA-loaded liposome (LRA) drug delivery system via the thin film hydration technique., The drug loading content was confirmed by high performance liquid chromatography. Dynamic light scattering was employed to evaluate the drug's particle size and stability. Methyl tetrazolium, colony formation, and Western blot (WB) were used in vitro to elucidate the inhibitory effect and mechanism of LRA on prostate cancer cells. Finally, xenograft model was used to confirm the tumor-inhibiting efficacy, clarify the mechanism, and determine the biosafety in mice.

Results

LRA has stable physicochemical properties and a diameter of 173.5 15.3 nm. LRA inhibited the growth of prostate cancer cells in a dose- and time-dependent manner. LRA can substantially reduce the expression of AR and HMGB1, induce apoptosis, regulate the expression of cell cycle-related proteins in vitro and in vivo. The results of the biosafety tests demonstrated that LRA effectively reduced the adverse effects of RA.

Conclusion

As a drug delivery system, LRA could effectively and safely inhibit the progression of prostate cancer.

Enzyme-catalyzed synthesis of selenium-doped manganese phosphate for synergistic therapy of drug-resistant colorectal cancer

BACKGROUND

The development of multidrug resistance (MDR) during postoperative chemotherapy for colorectal cancer substantially reduces therapeutic efficacy. Nanostructured drug delivery systems (NDDSs) with modifiable chemical properties are considered promising candidates as therapies for reversing MDR in colorectal cancer cells. Selenium-doped manganese phosphate (Se-MnP) nanoparticles (NPs) that can reverse drug resistance through sustained release of selenium have the potential to improve the chemotherapy effect of colorectal cancer.

RESULTS

Se-MnP NPs had an organic-inorganic hybrid composition and were assembled from smaller-scale nanoclusters. Se-MnP NPs induced excessive ROS production via Se-mediated activation of the STAT3/JNK pathway and a Fenton-like reaction due to the presence of manganese ions (Mn²⁺). Moreover, in vitro and in vivo studies demonstrated Se-MnP NPs were effective drug carriers of oxaliplatin (OX) and reversed multidrug resistance and induced caspase-mediated apoptosis in colorectal cancer cells. OX@Se-MnP NPs reversed MDR in colorectal cancer by down-regulating the expression of MDR-related ABC (ATP binding cassette) transporters proteins (e.g., ABCB1, ABCC1 and ABCG2). Finally, in vivo studies demonstrated that OX-loaded Se-MnP NPs significantly inhibited proliferation of OX-resistant HCT116 (HCT116/DR) tumor cells in nude mice.

CONCLUSIONS

OX@Se-MnP NPs with simple preparation and biomimetic chemical properties represent promising candidates for the treatment of colorectal cancer with MDR.

Targeting TLR2/Rac1/cdc42/JNK Pathway to Reveal That Ruxolitinib Promotes Thrombocytopoiesis

BACKGROUND

Thrombocytopenia has long been considered an important complication of chemotherapy and radiotherapy, which severely limits the effectiveness of cancer treatment and the overall survival of patients. However, clinical treatment options are extremely limited so far. Ruxolitinib is a potential candidate.

METHODS

The impact of ruxolitinib on the differentiation and maturation of K562 and Meg-01 cells megakaryocytes (MKs) was examined by flow cytometry, Giemsa and Phalloidin staining. A mouse model of radiation-injured thrombocytopenia (RIT) was employed to evaluate the action of ruxolitinib on thrombocytopoiesis. Network pharmacology, molecular docking, drug affinity responsive target stability assay (DARTS), RNA sequencing, protein blotting and immunofluorescence analysis were applied to explore the targets and mechanisms of action of ruxolitinib.

RESULTS

Ruxolitinib can stimulate MK differentiation and maturation in a dose-dependent manner and accelerates recovery of MKs and thrombocytopoiesis in RIT mice. Biological targeting analysis showed that ruxolitinib binds directly to Toll Like Receptor 2 (TLR2) to activate Rac1/cdc42/JNK, and this action was shown to be blocked by C29, a specific inhibitor of TLR2.

CONCLUSIONS

Ruxolitinib was first identified to facilitate MK differentiation and thrombocytopoiesis, which may alleviate RIT. The potential mechanism of ruxolitinib was to promote MK differentiation via activating the Rac1/cdc42/JNK pathway through binding to TLR2.

Theaflavin-3,3 ′ -Digallate Plays a ROS-Mediated Dual Role in Ferroptosis and Apoptosis via the MAPK Pathway in Human Osteosarcoma Cell Lines and Xenografts

Globally, osteosarcoma (OS) is the most prevalent form of primary bone cancer in children and adolescents. Traditional neoadjuvant chemotherapy regimens have reached a bottleneck; thus, OS survivors have unsatisfactory outcomes. Theaflavin-3,3′-digallate (TF3) exhibits potent anticancer properties against many human cancers. Nevertheless, the biological effects and the underlying molecular mechanism of TF3 in human OS remain unclear. The objective of this study was to investigate the effects of TF3 on human OS cell lines and mouse xenograft models. The results showed that TF3 reduced cell viability, suppressed cell proliferation, and caused G0/G1 cell cycle arrest in both MG63 and HOS cell lines in a concentration-dependent manner. TF3 also altered the homeostatic mechanisms for iron storage in the examined cell lines, resulting in an excess of labile iron. Unsurprisingly, TF3 caused oxidative stress through reduced glutathione (GSH) exhaustion, reactive oxygen species (ROS) accumulation, and the Fenton reaction, which triggered ferroptosis and apoptosis in the cells. TF3 also induced MAPK signalling pathways, including the ERK, JNK, and p38 MAPK pathways. Furthermore, oxidative stress was shown to be the primary reason for TF3-induced proliferation inhibition, programmed cell death, and MAPK pathway activation in vitro. Moreover, TF3 exhibited markedly strong antitumour efficacy in vivo in mouse models. In summary, this study demonstrates that TF3 concomitantly plays dual roles in apoptotic and ferroptotic cell death by triggering the ROS and MAPK signalling pathways in both in vitro and in vivo models.

Curculigoside Represses the Proliferation and Metastasis of Osteosarcoma via the JAK/STAT and NF-κB Signaling Pathways

Curculigoside (Cur) is a natural component from Curculigo orchioides Gaertn, with various bioactivities. The function of Cur in the nervous system and osteoarthritis has been reported. However, its role in osteosarcoma (OS) needs to be investigated. Hence, we focus on probing the impact of Cur on OS. In vitro, cell counting kit 8 (CCK-8), flow cytometry and Transwell assay were used to investigate the effects of Cur on OS cell proliferation, apoptosis, migration and invasion. In vivo, we developed a xenograft model to figure out the effect of Cur on tumor growth in nude mice. Western blotting (WB) was conducted to compare the levels of Cur on apoptosis-related proteins (C-caspase-3, Bax, and Bcl-2), epithelial-mesenchymal transition (EMT)-related proteins (N-cadherin, Snail, and E-cadherin) and the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and nuclear factor-κB (NF-κB) pathways in vitro and in vivo. In-vitro data testified that Cur treatment markedly hampered OS cells' growth, migration and invasion and intensified their apoptosis compared to that of the control group. In vivo, Cur treatment notably hampered the growth of OS tumors in mice. In addition, both in vitro and in vivo experiments demonstrated that the phosphorylation of JAK2, STAT3, and NF-κB were inhibited through Cur treatment. Furthermore, the inhibition of Cur in OS cells was demonstrated by up-regulating the expression of JAK/STAT and NF-κB pathways protein levels. In summary, the data suggest that Cur curbs OS growth by down-regulating the JAK/STAT and NF-κB pathways, which is an underlying therapeutic option for OS treatment.

Construction of IL-13 Receptor α2-Targeting Resveratrol Nanoparticles against Glioblastoma Cells: Therapeutic Efficacy and Molecular Effects

Glioblastoma multiforme (GBM) is the most common lethal primary brain malignancy without reliable therapeutic drugs. IL-13Rα2 is frequently expressed in GBMs as a molecular marker. Resveratrol (Res) effectively inhibits GBM cell growth but has not been applied in vivo because of its low brain bioavailability when administered systemically. A sustained-release and GBM-targeting resveratrol form may overcome this therapeutic dilemma. To achieve this goal, encapsulated Res 30 ± 4.8 nm IL-13Rα2-targeting nanoparticles (Pep-PP@Res) were constructed. Ultraviolet spectrophotometry revealed prolonged Res release (about 25%) from Pep-PP@Res in 48 h and fluorescent confocal microscopy showed the prolonged intracellular Res retention time of Pep-PP@Res (>24 h) in comparison with that of free Res (<4 h) and PP@Res (<4 h). MTT and EdU cell proliferation assays showed stronger suppressive effects of Pep-PP@Res on rat C6 GBM cells than that of PP@Res (p = 0.024) and Res (p = 0.009) when used twice for 4 h/day. Pep-PP@Res had little toxic effect on normal rat brain cells. The in vivo anti-glioblastoma effects of Res can be distinctly improved in the form of Pep-PP@Res nanoparticles via activating JNK signaling, upregulating proapoptosis gene expression and, finally, resulting in extensive apoptosis. Pep-PP@Res with sustained release and GBM-targeting properties would be suitable for in vivo management of GBMs.

Raddeanin A induced apoptosis of non-small cell lung cancer cells by promoting ROS-mediated STAT3 inactivation

PURPOSE

Non-small cell lung cancer (NSCLC) is a high-risk type of lung cancer. Raddeanin A exerts anti-tumor activity by regulating cell proliferation and apoptosis, but its role in NSCLC remains to be elucidated. This study was to investigate the effect of raddeanin A in NSCLC and its mechanism.

METHODS

The effect of raddeanin A (2, 4, 8, 10 μmol/L) on the viability, proliferation and apoptosis of A549 and H1299 cells was determined by cell counting kit-8, colony formation and flow cytometry assays, respectively. Next, western blot was performed to examine the protein expressions of cleaved caspase-3, Bax, phosphorylated signal transducer and activator of transcription 3 (p-STAT3) and STAT3. Subsequently, the intracellular reactive oxygen species (ROS) generation and mitochondrial membrane potential of NSCLC cells were detected by 2', 7'-dichlorofluorescein-diacetate (DCFH-DA) and JC-1 assay. Lastly, the effect of N-acetylcysteine (NAC) on the apoptosis, ROS generation, and STAT3 was evaluated by the above-mentioned assays again.

RESULTS

Raddeanin A treatment had no obvious effect on 16HBE cells viability, but it inhibited viability and proliferation of A549 and H1299 cells, promoted the apoptosis, increased the protein expressions of cleaved caspase-3 and Bax, generated intracellular ROS, as well as decreased mitochondrial membrane potential and the expressions of p-STAT3 and STAT3 in A549 and H1299 cells. After cells treated with NAC, the effect of raddeanin A was reversed, as evidenced by the apoptosis and ROS generation were suppressed, and the expression of p-STAT3 was promoted.

CONCLUSION

Raddeanin A suppressed the proliferation and induced apoptosis of NSCLC cells via promoting the ROS-mediated STAT3 inactivation.

Synthesis and antitumor activity evaluation of oleanolic acid saponins bearing an acetylated l-arabinose moiety

A series of oleanolic acid derivatives bearing acetyl-substituted l-arabinose moiety has been synthesized and screened in vitro for cytotoxicity against ten cancer cell lines and four normal cell lines. The antiproliferative evaluation indicated that synthetic derivatives showed excellent selectivity, as they were toxic against only A431 cell line. Among them, the compound 6 possesses the best inhibitory activity. A series of pharmacology experiments showed that compound 6 significantly induced A431 cells apoptosis and cell cycle arrest, which could serve as a promising lead candidate for further study.

Wogonin Influences Osteosarcoma Stem Cell Stemness Through ROS-dependent Signaling

Backgorund/Aim: Wogonin, a flavonoid-like compound extracted from the root of Scutellaria baicalensis Georgi, has been shown to have anticancer effects against cancer cells. Osteosarcoma is the most malignant type of bone cancer and can appear in any bone, with a high propensity for relapse and metastasis. The present study aimed to assess the anticancer effects of wogonin on osteosarcoma stem cells.

MATERIALS AND METHODS

The cytotoxic effects of wogonin on CD133⁺ Cal72 osteosarcoma stem cells were assessed through in vitro experiments by MTT assay, transwell assay, sphere-formation assay, flow cytometry, immunocytochemistry and western blotting.

RESULTS

Wogonin suppressed stem cell characteristics and the expression of stem cell-related genes by regulating reactive oxygen species (ROS) levels and ROS-related signaling of CD133⁺ Cal72 cells, effects which were reversed by ROS scavenger N-acetylcysteine.

CONCLUSION

Wogonin may be a promising candidate for successful clinical management of osteosarcoma by regulating ROS-related mechanisms and stem cell-related genes.

Anti-breast cancer and toxicity studies of total secondary saponin from Anemone raddeana Rhizome on MCF-7 cells via ROS generation and PI3K/AKT/mTOR inactivation

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizome of Anemone raddeana Regel (A. raddeana) is a famous traditional Chinese medicine (TCM) recorded in Chinese Pharmacopoeia for the treatment of carbuncle and swelling. Carbuncle swollen is an explanation of tumor in the theory of TCM and softening and resolving hard mass effects are one of the important pharmacological activities of A. raddeana.

AIM OF THE STUDY

We investigated the potential anti-breast cancer effect and toxicological properties of alkali-ethanol extract from A. raddeana, namely total secondary saponin (TSS).

MATERIALS AND METHODS

Anti-proliferative effect of total saponin of A. raddeana (ATS) and TSS were tested using MTT assay. Hoechst staining, flow cytometry analysis, DCFH-DA fluorescence microscopy and western blot were carried out to evaluate the mechanisms of action of TSS. The potential anti-breast cancer activity and toxicological properties of TSS were tested in vivo.

RESULTS

ATS and TSS could inhibit the proliferation of A549, HepG2, MCF-7, MDA-MB-231 and SKBr-3 cells, especially for MCF-7 cells. Flow cytometry analysis revealed that TSS (10, 12 and 15 μg/ml) could induce cell cycle arrest on G0/G1 phase and promote apoptosis of MCF-7 cells. TSS could increase Bax/Bcl-2 ratio, elevate cytochrome c levels in cytosol and activate caspase-3/9. In addition, TSS also induced ROS generation and inactivated PI3K/AKT/mTOR pathway which may involved in the mitochondrial dysfunction of MCF-7 cells. TSS showed slight toxic at the dosage of 100 and 200 mg/kg by oral administration without any toxic potential for 28 days. TSS (50, 100 and 200 mg/kg) showed significant inhibitory effect on growth of transplanted tumor in mice. At last, twenty-three C-3 monosaccharide oleanane-type triterpene saponins were tentatively identified, which may contributed to the anti-cancer activity of TSS.

CONCLUSION

This study demonstrated that TSS exhibited anti-proliferative and pro-apoptosis activities on MCF-7 cells via ROS-mediated activation of mitochondrial apoptosis pathway. TSS might be used as chemotherapeutic agent for the treatment of breast cancer with relatively low toxicity.

Downregulation of miR-19a inhibits the proliferation and promotes the apoptosis of osteosarcoma cells by regulating the JAK2/STAT3 pathway

Osteosarcoma is a malignant tumor derived from the skeletal system, often occurring in bone tissues, and it is the most common malignant tumor in the skeletal system, with more than 90% of cases being highly malignant. The present study was designed to explore the regulatory effects of microRNA (miR)-19a on the proliferation and apoptosis of osteosarcoma cells, and its influence on the activation of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. The expression of miR-19a in adult SaOS-2 osteosarcoma cells was downregulated via lentiviral transfection, and the cells were divided into a control group, NC-inhibitor group and miR-19a-inhibitor group. The expression of miR-19a in each group was detected via quantitative polymerase Chain reaction (qPCR). Next, the cell proliferation and apoptosis levels in each group were detected via methyl thiazolyl tetrazolium (MTT) assay and flow cytometry, respectively, and the level of reactive oxygen species (ROS) in cells was further determined. Moreover, the expression levels of apoptosis-related proteins and JAK2/STAT3 signaling pathway-related proteins were detected through western blotting. The expression level of miR-19a in the miR-19a-inhibitor group was significantly lower than that in the control group and NC-inhibitor group (P<0.01). Downregulation of miR-19a significantly reduced the proliferation ability (P<0.01), increased the apoptosis level of SaOS-2 cells (P<0.01), and significantly increased the ROS level in cells (P<0.01). Downregulation of miR-19a also promote cleaved caspase-3/caspase-3 expression in the OS cells (P<0.01) and inhibited Bcl-2/Bax expression (P<0.01). Additionally, downregulation of miR-19a markedly lowered the protein expression levels of phosphorylated (p-)JAK2, p-STAT3 and myeloid cell leukemia-1 (Mcl-1) in the cells (P<0.01). To conclude, downregulation of miR-19a can inhibit the JAK2/STAT3 signaling pathway in SaOS-2 cells, promote the expression of apoptosis-related proteins, and increase the ROS level in cells, thereby promoting apoptosis and inhibiting cell proliferation.

Anticancer Potential of Raddeanin A, a Natural Triterpenoid Isolated from Anemone raddeana Regel

Natural compounds extracted from plants have gained immense importance in the fight against cancer cells due to their lesser toxicity and potential therapeutic effects. Raddeanin A (RA), an oleanane type triterpenoid is a major compound isolated from Anemone raddeana Regel. As an anticancer agent, RA induces apoptosis, cell cycle arrest, inhibits invasion, migration and angiogenesis in malignant cell lines as well as in preclinical models. In this systemic review, the pharmacological effects of RA and its underlying molecular mechanisms were carefully analyzed and potential molecular targets have been highlighted. The apoptotic potential of RA can be mediated through the modulation of Bcl-2, Bax, caspase-3, caspase-8, caspase-9, cytochrome c and poly-ADP ribose polymerase (PARP) cleavage. PI3K/Akt signaling pathway serves as the major molecular target affected by RA. Furthermore, RA can block cell proliferation through inhibition of canonical Wnt/β-catenin signaling pathway in colorectal cancer cells. RA can also alter the activation of NF-κB and STAT3 signaling pathways to suppress invasion and metastasis. RA has also exhibited promising anticancer potential against drug resistant cancer cells and can enhance the anticancer effects of several chemotherapeutic agents. Overall, RA may function as a promising compound in combating cancer, although further in-depth study is required under clinical settings to validate its efficacy in cancer patients.

Degradation of long non-coding RNA-CIR decelerates proliferation, invasion and migration, but promotes apoptosis of osteosarcoma cells

Background

Over the years, long non-coding RNAs (lncRNAs) have been clarified in malignancies, this research was focused on the role of lncRNA cartilage injury-related (lncRNA-CIR) in osteosarcoma cells.

Methods

LncRNA-CIR expression in osteosarcoma tissues and cells, and adjacent normal tissues and normal osteoblasts was determined, then the relations between lncRNA-CIR expression and the clinicopathological features, and between lncRNA-CIR expression and the prognosis of osteosarcoma patients were analyzed. Moreover, the MG63 and 143B cells were treated with silenced or overexpressed lncRNA-CIR, and then the proliferation, invasion, migration and apoptosis of the cells were evaluated by gain- and loss-of-function approaches. The tumor growth, and proliferation and apoptosis of osteosarcoma cells in vivo were observed by subcutaneous tumorigenesis in nude mice.

Results

We have found that lncRNA-CIR was up-regulated in osteosarcoma tissues and cells, which was respectively relative to adjacent normal tissues and normal osteoblasts. The expression of lncRNA-CIR was evidently correlated with disease stages, distant metastasis and differentiation of osteosarcoma patients, and the high expression of lncRNA-CIR indicated a poor prognosis. Furthermore, the reduction of lncRNA-CIR could restrict proliferation, invasion and migration, but promote apoptosis of osteosarcoma cells in vitro. Meanwhile, inhibited lncRNA-CIR also restrained tumor growth and osteosarcoma cell proliferation, whereas accelerated apoptosis of osteosarcoma cells in vivo.

Conclusion

We have found in this study that the inhibited lncRNA-CIR could decelerate proliferation, invasion and migration, but accelerate apoptosis of osteosarcoma cells, which may provide a novel target for osteosarcoma treatment.

Antitumor activity of Raddeanin A is mediated by Jun amino-terminal kinase activation and signal transducer and activator of transcription 3 inhibition in human osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor. Raddeanin A (RA) is an active oleanane‐type triterpenoid saponin extracted from the traditional Chinese herb Anemone raddeana Regel that exerts antitumor activity against several cancer types. However, the effect of RA on osteosarcoma remains unclear. In the present study, we showed that RA inhibited proliferation and induced apoptosis of osteosarcoma cells in a dose‐ and time‐dependent way in vitro and in vivo. RA treatment resulted in excessive reactive oxygen species (ROS) generation and JNK and ERK1/2 activation. Apoptosis induction was evaluated by the activation of caspase‐3, caspase‐8, and caspase‐9 and poly‐ADP ribose polymerase (PARP) cleavage. RA‐induced cell death was significantly restored by the ROS scavenger glutathione (GSH), the pharmacological inhibitor of JNK SP600125, or specific JNK knockdown by shRNA. Additionally, signal transducer and activator of transcription 3 (STAT3) activation was suppressed by RA in human osteosarcoma, and this suppression was restored by GSH, SP600125, and JNK‐shRNA. Further investigation showed that STAT3 phosphorylation was increased after JNK knockdown. In a tibial xenograft tumor model, RA induced osteosarcoma apoptosis and notably inhibited tumor growth. Taken together, our results show that RA suppresses proliferation and induces apoptosis by modulating the JNK/c‐Jun and STAT3 signaling pathways in human osteosarcoma. Therefore, RA may be a promising candidate antitumor drug for osteosarcoma intervention.