HIF-1α induced by β-elemene protects human osteosarcoma cells from undergoing apoptosis

Beta-elemene: A phytochemical with promise as a drug candidate for tumor therapy and adjuvant tumor therapy

BACKGROUND

β-Elemene (IUPAC name: (1 S,2 S,4 R)-1-ethenyl-1-methyl-2,4-bis(prop-1-en-2-yl) cyclohexane), is a natural compound found in turmeric root. Studies have demonstrated its diverse biological functions, including its anti-tumor properties, which have been extensively investigated. However, these have not yet been reviewed. The aim of this review was to provide a comprehensive summary of β-elemene research, with respect to disease treatment.

METHODS

β-Elemene-related articles were found in PubMed, ScienceDirect, and Google Scholar databases to systematically summarize its structure, pharmacokinetics, metabolism, and pharmacological activity. We also searched the Traditional Chinese Medicine System Pharmacology database for therapeutic targets of β-elemene. We further combined these targets with the relevant literature for KEGG and GO analyses.

RESULTS

Studies on the molecular mechanisms underlying β-elemene activity indicate that it regulates multiple pathways, including STAT3, MAPKs, Cyclin-dependent kinase 1/cyclin B, Notch, PI3K/AKT, reactive oxygen species, METTL3, PTEN, p53, FAK, MMP, TGF-β/Smad signaling. Through these molecular pathways, β-elemene has been implicated in tumor cell proliferation, apoptosis, migration, and invasion and improving the immune microenvironment. Additionally, β-elemene increases chemotherapeutic drug sensitivity and reverses resistance by inhibiting DNA damage repair and regulating pathways including CTR1, pak1, ERK1/2, ABC transporter protein, Prx-1 and ERCC-1. Nonetheless, owing to its lipophilicity and low bioavailability, additional structural modifications could improve the efficacy of this drug.

CONCLUSION

β-Elemene exhibits low toxicity with good safety, inhibiting various tumor types via diverse mechanisms in vivo and in vitro. When combined with chemotherapeutic drugs, it enhances efficacy, reduces toxicity, and improves tumor killing. Thus, β-elemene has vast potential for research and development.

Network pharmacology and experimental validation to study the potential mechanism of Tongguanteng injection in regulating apoptosis in osteosarcoma

OBJECTIVE

The main objectives of this study were to identify the active components of Tongguanteng injection (TGT) and investigate the preclinical efficacy and mechanism of TGT on osteosarcoma using a combination of network pharmacology and experimental validation.

METHODS

To identify the active constituents and targets of TGT against osteosarcoma using network pharmacology, we constructed a network consisting of an 'active ingredient-disease-target-pathway' and a protein-protein interaction (PPI) network. The target organ network was utilized to investigate the distribution of core targets in tissues. Afterwards, the core targets underwent Gene ontology (GO) functional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The binding energy between receptors and ligands was compared using molecular docking. In addition, SwissADME was employed to forecast the pharmacokinetic characteristics of the substances. Finally, real-time polymerase chain reaction (RT-PCR), cell proliferation assay, morphological analysis, apoptosis assay, mitochondrial membrane potential (MMP) detection, and Western blotting were utilized to confirm the potential mechanisms of TGT treatment in osteosarcoma cell lines 143B and SAOS2.

RESULTS

A total of 54 chemical constituents of TGT and 71 targets associated with osteosarcoma were acquired. Through the molecular docking technology, Tenacigenin B, Marsdekoiside, Taraxasterol, Tenacissoside G, Tenacissoside L, and Tenacissoside J were identified as the primary active components of TGT among the various compounds. Analysis of target organs suggests that TGT may play an anti-osteosarcoma role through immune regulation. The GO and KEGG enrichment analysis revealed that TGT could trigger osteosarcoma cell apoptosis by inhibiting the HIF-1 signalling pathway and modulating PD-1 expression and the PD-1 checkpoint pathway in cancer. SwissADME database predicted that Tenacigenin B and Taraxasterol had the best drug-likeness. In vitro studies also demonstrated that TGT suppressed the activity and induced alterations in the morphology of osteosarcoma cells. It decreased MMP levels, triggered apoptosis by increasing Bax expression and Caspase-3 activity, and decreased Bcl-2 expression, thereby exerting an anti-osteosarcoma effect. In the meantime, RT-PCR tests demonstrated that TGT could control immune response against tumors and hinder the proliferation and spread of cancerous cells by impacting the levels of critical factors, including JUN, HSP90AA1, HDAC1, and CDK1.

CONCLUSION

The study accurately anticipated the active components, targets, and pathways of TGT in the management of osteosarcoma. The molecular mechanism of TGT-induced apoptosis in osteosarcoma cells was demonstrated by in vitro experiments. These results provide theoretical and technical support for TGT as a clinical adjuvant drug for osteosarcoma.

β-Elemene Enhances the Sensitivity of Osteosarcoma Cells to Doxorubicin via Downregulation of Peroxiredoxin-1

Background

Doxorubicin (Dox) resistance is a primary obstacle for the treatment of osteosarcoma. Meanwhile, β-Elemene was shown to exhibit an anti-proliferative effect on osteosarcoma cells. However, the role of a combination of Dox with β-Elemene on osteosarcoma cells remains unclear. Thus, this study aimed to investigate the role of the combination of Dox with β-Elemene on the proliferation, apoptosis and oxidative stress of Dox-resistance osteosarcoma cells.

Methods

CKC-8, EdU staining and flow cytometry assays were used to determine the viability, proliferation and apoptosis of Dox-resistance osteosarcoma cells, respectively. Meanwhile, the expression of antioxidant protein peroxiredoxin-1 (Prx-1) in Dox-resistance osteosarcoma cells was detected with Western blot assay.

Results

In this study, the inhibitory effects of Dox on the viability and proliferation of Dox-resistance osteosarcoma cells were significantly enhanced by β-Elemene. In addition, the combination of Dox and β-Elemene markedly induced the apoptosis and oxidative stress in Dox-resistance osteosarcoma cells. Moreover, combination treatment notably downregulated the expression of Prx-1 in Dox-resistance osteosarcoma cells, indicating that combination treatment inhibited the antioxidant capacity of Dox-resistance osteosarcoma cells. In vivo experiments confirmed that β-Elemene could enhance the anti-tumor effect of Dox in Saos-2/Dox xenograft model.

Conclusion

We found that β-Elemene could reverse Dox resistance in Dox-resistance osteosarcoma cells via inhibition of Prx-1. Therefore, combining Dox with β-Elemene might be considered as a therapeutic approach for the treatment of Dox-resistant osteosarcoma.

Terpenoids from Curcumae Rhizoma: Their anticancer effects and clinical uses on combination and versus drug therapies

Cancer is a fatal disease with high mortality and low survival rate worldwide. At present, there is still no known cure for most cancers. Traditional Chinese medicine (TCM) represents a noteworthy reservoir for anticancer agents in drug discovery and development. Curcumae Rhizoma (called Ezhu in Chinese) is widely prescribed in TCM for anticancer therapy owing to its broad-spectrum antineoplastic activities. Especially, the terpenoids isolated from the essential oil of Curcumae Rhizoma form an integral part of cancer research and are well established as a potential anticancer agent. For example, β-elemene has been developed into a new drug for the treatment of solid tumors in China, and is currently undergoing clinical trials in the United States. The review aims to systematically summarize the recent advances on the anticancer effects and related molecular mechanisms of Curcumae Rhizoma, and its terpenoids (β-elemene, Furanodiene, Furanodienone, Germacrone, Curcumol, Curdione). In addition, we evaluated and compared the anticancer efficacy and clinical use of the terpenoids with combination therapies and traditional therapies. Therefore, this review provides sufficient evidence for the anticancer therapeutic potential of Curcumae Rhizoma and its terpenoids, and will contribute to the development of potential anticancer drugs.

HIF-1α-Mediated Mitophagy Determines ZnO Nanoparticle-Induced Human Osteosarcoma Cell Death both In Vitro and In Vivo

Although ZnO nanoparticles (NPs) can kill human osteosarcoma cells, the underlying upstream regulatory mechanisms remain unclear. Since hypoxia inducible factor-1α (HIF-1α) regulates the tumor microenvironment, here we explored the interplay between HIF-1α regulation and mitophagy in ZnO NP-induced osteosarcoma inhibition both in vivo and in vitro. We found that ZnO NPs upregulated HIF-1α protein levels when they killed four common human osteosarcoma cell lines. This finding was consistent with our observations that additional HIF-1α upregulation by a hypoxia inducer CoCl₂ or under a 1% hypoxia environment enhanced NP-induced cell death, but concurrent HIF-1α suppression by a hypoxia inhibitor YC-1 or HIF-1α siRNA inhibited NP-induced cell death. We discovered an interplay between HIF-1α and the autophagy-Zn²⁺-reactive oxygen species (ROS)-autophagy cycle axis and revealed that NP-induced cancer cell killing followed a HIF-1α-BNIP3-LC3B-mediated mitophagy pathway. We confirmed that NP-upregulated HIF-1α protein expression was attributed to prolyl hydroxylase inhibition by both ROS and Zn²⁺. In addition, the in vivo assay confirmed the therapeutic effectiveness and safety of ZnO NPs on a nude mice osteosarcoma model. Collectively, our findings clarified the upstream regulatory mechanism of autophagy induced by the NPs and further demonstrated their antitumor ability in vivo. This work provides new targets and strategies for enhancing NP-based osteosarcoma treatment.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Molecular targets of β-elemene, a herbal extract used in traditional Chinese medicine, and its potential role in cancer therapy: A review

β-Elemene is a sesquiterpene compound extracted from the herb Curcuma Rhizoma and is used in traditional Chinese medicine (TCM) to treat several types of cancer, with no reported severe adverse effects. Recent studies, using in vitro and in vivo studies combined with molecular methods, have shown that β-elemene can inhibit cell proliferation, arrest the cell cycle, and induce cell apoptosis. Recent studies have identified the molecular targets of β-elemene that may have a role in cancer therapy. This review aims to discuss the anticancer potential of β-elemene through its actions on several molecular targets including kinase enzymes, transcription factors, growth factors and their receptors, and proteins. β-Elemene also regulates the expression of several key molecules that are involved in tumor angiogenesis and metastasis including vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs), E-cadherin, N-cadherin, and vimentin. Also, β-elemene has been shown to have regulatory effects on the immune response and increases the sensitivity of cancer cells to chemoradiotherapy and has shown effects on multidrug resistance (MDR) in malignancy. Recent studies have shown that β-elemene can induce autophagy, which prevents cancer cells from undergoing apoptosis. Therefore, the molecular mechanisms for the treatment effects on cancer of the herbal extract, β-elemene, which has been used for centuries in traditional Chinese medicine, are now being studied and identified.

Drug delivery systems for elemene, its main active ingredient β-elemene, and its derivatives in cancer therapy

β-elemene is a noncytotoxic Class II antitumor drug extracted from the traditional Chinese medicine Curcuma wenyujin Y. H. Chen et C. Ling. β-elemene exerts its effects by inhibiting cell proliferation, arresting the cell cycle, inducing cell apoptosis, exerting antiangiogenesis and antimetastasis effects, reversing multiple-drug resistance (MDR), and enhancing the immune system. Elemene injection and oral emulsion have been used to treat various tumors, including cancer of the lung, liver, brain, breast, ovary, gastric, prostate, and other tissues, for >20 years. The safety of both elemene injection and oral emulsion in the clinic has been discussed. Recently, the secondary development of β-elemene has attracted the attention of researchers and made great progress. On the one hand, studies have been carried out on liposome-based systems (including solid lipid nanoparticles [SLNs], nanostructured lipid carriers [NLCs], long-circulating liposomes, active targeting liposomes, and multidrug-loaded liposomes) and emulsion systems (including microemulsions, self-emulsion drug delivery systems [SEDDSs], and active targeting microemulsion) to solve the issues of poor solubility in water, low bioavailability, and severe phlebitis, as well as to improve antitumor efficacy. The pharmacokinetics of different drug delivery systems of β-elemene are also summarized. On the other hand, a number of highly active anticancer β-elemene derivatives have been obtained through modification of the structure of β-elemene. This review focuses on the two drug delivery systems and derivatives of β-elemene for cancer therapy.

Radiosensitizing effects of miR-18a-5p on lung cancer stem-like cells via downregulating both ATM and HIF-1α

Lung cancer is one of the main causes of cancer mortality globally. Most patients received radiotherapy during the course of disease. However, radioresistance generally occurs in the majority of these patients, leading to poor curative effect, and the underlying mechanism remains unclear. In the present study, miR-18a-5p expression was downregulated in irradiated lung cancer cells. Overexpression of miR-18a-5p increased the radiosensitivity of lung cancer cells and inhibited the growth of A549 xenografts after radiation exposure. Dual luciferase report system and miR-18a-5p overexpression identified ataxia telangiectasia mutated (ATM) and hypoxia inducible factor 1 alpha (HIF-1α) as the targets of miR-18a-5p. The mRNA and protein expressions of ATM and HIF-1α were dramatically downregulated by miR-18a-5p in vitro and in vivo. Clinically, plasma miR-18a-5p expression was significantly higher in radiosensitive than in radioresistant group (P < .001). The cutoff value of miR-18a-5p >2.28 was obtained from receiver operating characteristic (ROC) curve. The objective response rate (ORR) was significantly higher in miR-18a-5p-high group than in miR-18a-5p-low group (P < .001). A tendency demonstrated that the median local progression-free survival (PFS) from radiotherapy was longer in miR-18a-5p-high than in miR-18a-5p-low group (P = .082). The median overall survival (OS) from radiotherapy was numerically longer in miR-18a-5p-high than in miR-18a-5p-low group (P = .281). The sensitivity and specificity of plasma miR-18a-5p to predict radiosensitivity was 87% and 95%, respectively. Collectively, these results indicate that miR-18a-5p increases the radiosensitivity in lung cancer cells and CD133+ stem-like cells via downregulating ATM and HIF-1α expressions. Plasma miR-18a-5p would be an available indicator of radiosensitivity in lung cancer patients.

mTOR: An attractive therapeutic target for osteosarcoma?

Osteosarcoma (OS) is a common primary malignant bone tumor with high morbidity and mortality in children and young adults. How to improve poor prognosis of OS due to resistance to chemotherapy remains a challenge. Recently, growing findings show activation of mammalian target of rapamycin (mTOR), is associated with OS cell growth, proliferation, metastasis. Targeting mTOR may be a promising therapeutic approach for treating OS. This review summarizes the roles of mTOR pathway in OS and present research status of mTOR inhibitors in the context of OS. In addition, we have attempted to discuss how to design a better treatment project for OS by combining mTOR inhibitor with other drugs.

Therapeutic effects of β-elemene via attenuation of the Wnt/β-catenin signaling pathway in cervical cancer cells

Concurrent radio chemotherapy treatment prolongs the survival rate of patients with advanced cervical cancer; however, it has adverse side-effects. β-elemene, an active component of the traditional Chinese medicinal herb Curcuma zedoaria, is a promising alternative therapeutic drug for the treatment of advanced cervical cancer. The aim of the present study was to investigate the antitumor effects of β-elemene in human cervical cancer SiHa cells and to determine its underlying therapeutic molecular mechanisms. Cell viability, cell cycle progression and apoptosis were detected using an MTT assay and flow cytometry analysis. Furthermore, the levels of cell migration and cell invasion were investigated using Transwell and wound healing assays. The expression levels of Cyclin-dependent kinase inhibitor 2B (P15), Cyclin D1, cellular tumor antigen p53, apoptosis regulator Bcl-2 (Bcl-2), apoptosis regulator BAX (Bax), 72 kDa type IV collagenase (MMP-2), matrix metalloproteinase-9 (MMP-9), β-catenin, transcription factor 7 (TCF7), and Myc proto-oncogene protein (c-Myc) were analyzed via western blotting. The results revealed that β-elemene inhibited the proliferation of SiHa cells in a dose and time-dependent manner. Administration of β-elemene induced G1 phase cell-cycle arrest, as demonstrated by the upregulation of P15 expression and the downregulation of Cyclin D1 expression. Furthermore, the present study revealed that β-elemene induced apoptosis in SiHa cells by enhancing the expression of p53 and Bax, and suppressing the expression of Bcl-2. In addition, treatment with β-elemene inhibited cell migration and invasion via downregulation of MMP-2 and MMP-9 expression levels. Western blotting demonstrated that β-elemene reduced the expression levels of β-catenin and its downstream target molecule TCF7, thus resulting in reduced levels of their target proteins, including c-Myc, Cyclin D1, Bax and MMP-2 in cervical cancer cells. The results of the present study suggested that β-elemene may inhibit cell proliferation and invasion, in addition to inducing apoptosis, via attenuation of the Wnt/β-catenin signaling pathway in cervical cancer cells.

Elemene inhibits osteosarcoma growth by suppressing the renin‑angiotensin system signaling pathway

Osteosarcoma remains the most prevalent primary malignant bone tumor in children and young adults globally. Therefore, novel and highly effective antitumor agents are urgently required. Elemene is a natural plant compound extracted from the medicinal Chinese herb, Rhizomazedoariae, which has been employed as an antitumor agent for the treatment of a number of tumors, including osteosarcoma. However, the mechanisms underlying its antitumor effect are currently unclear. The human osteosarcoma cell lines, MG‑63 and U2OS, were employed in the present study. MTT, migration, transwell invasion and terminal deoxynucleotidyltransferase‑mediated deoxy‑UTP‑fluorescein nick end‑labeling assays were performed to evaluate cell viability, migration, invasion and apoptosis, respectively. Western blotting and immunohistochemistry analyses were performed to measure the levels of renin‑angiotensin system (RAS) components. In order to evaluate the effect of elemene on tumor weight and volume, MG‑63 and U2OS cells were injected into mice. Treatment of osteosarcoma cell lines, MG‑63 and U2OS, with elemene led to the inhibition of cell viability, migration and invasion, as well as induction of cell apoptosis. In addition, elemene treatment downregulated the expression of a number of RAS components. The growth of osteosarcoma cell‑transplanted tumors in nude mice and angiotensin II expression were inhibited by elemene treatment. The results of the present study indicate that the antitumor effects of elemene may partly be due to downregulation of the RAS signaling pathway, and that RAS may be a putative pharmacological target for osteosarcoma therapy.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

MicroRNA-20b Downregulates HIF-1α and Inhibits the Proliferation and Invasion of Osteosarcoma Cells

Osteosarcoma (OS) is the most common malignant primary bone tumor disease. HIF-1α was predicted to be the target gene of microRNA-20b (miR-20b). The present study was designed to illustrate the effect of miR-20b in regulating osteosarcoma via targeting HIF-1α. In this study, we found that the expression of HIF-1α was significantly increased, while miR-20b obviously decreased in OS patients and OS cell lines compared with healthy controls. Moreover, the luciferase report confirmed the targeting reaction between miR-20b and HIF-1α. Additionally, the overexpression of miR-20b suppressed the invasion and growth of both MG63 and U2OS cells, and inhibited the expressions of HIF-1α and VEGF pathway proteins, while the inhibition of miR-20b led to the reverse results. Furthermore, the overexpression of HIF-1α affected the suppression effect of miR-20b in MG63 cells, indicating that miR-20b suppresses the tumor cell process via inhibiting the expression of HIF-1α. Taken together, our results suggest that the upregulation of miR-20b affects the expression of HIF-1α, downregulates the VEGF pathway proteins, and suppresses cell invasion and proliferation rate. These results provide a potential therapeutic strategy for osteosarcoma.

MicroRNA-33b Inhibits the Proliferation and Migration of Osteosarcoma Cells via Targeting Hypoxia-Inducible Factor-1α

Recently, microRNA (miR)-33b has been demonstrated to act as a tumor suppressor in osteosarcoma. However, the regulatory mechanism of miR-33b in osteosarcoma cell proliferation and migration remains largely unknown. In this study, real-time PCR showed that miR-33b was significantly downregulated in osteosarcoma tissues compared to their matched adjacent nontumor tissues. Its expression was also decreased in several common osteosarcoma cell lines, including Saos-2, MG63, U2OS, and SW1353, when compared to normal osteoblast cell line hFOB. Overexpression of miR-33b suppressed U2OS cell proliferation and migration. HIF-1α was further identified as a target of miR-33b, and its protein levels were reduced after overexpression of miR-33b in U2OS cells. Moreover, overexpression of HIF-1α significantly reversed the suppressive effect of miR-33b on U2OS cell proliferation and migration. In addition, HIF-1α was found to be significantly upregulated in osteosarcoma tissues compared to adjacent nontumor tissues, and their expression levels were inversely correlated to the miR-33b levels in osteosarcoma tissues. According to these findings, miR-33b plays a suppressive role in the regulation of osteosarcoma cell proliferation and migration via directly targeting HIF-1α. Therefore, we suggest that the miR-33b/HIF-1α axis may become a promising therapeutic target for osteosarcoma.

Inhibition of hypoxia-inducible factor-1 alpha radiosensitized MG-63 human osteosarcoma cells in vitro

AIMS AND BACKGROUND

Hypoxia is a fundamental microenvironmental component of osteosarcoma which induces activation of the hypoxia-inducible factor-1 (HIF-1) pathway. Overexpression of HIF-1α has been linked to tumor resistance to radio- or chemotherapy. However, little is known about the effects of HIF-1α inhibition on hypoxic radioresistance of human osteosarcoma cells. Here, we investigated the effects of HIF-1α inhibition on cell survival and radiosensitivity in the MG-63 human osteosarcoma cell line.

METHODS

HIF-1α inhibition was achieved by small interfering RNA (siRNA) targeting of HIF-1α or via chetomin. Inhibition of the HIF-1 pathway was determined by monitoring the expression levels of HIF-1α, carbonic anhydrase 9 (CA9) and vascular endothelial growth factor (VEGF) using quantitative real-time PCR and Western blot analyses. Clonogenic assay was performed after irradiation (2-10 Gy) to investigate the effect of HIF-1α inhibition on the radiosensitivity of human osteosarcoma cells under normoxic and hypoxic conditions.

RESULTS

Compared to the control groups, treatment with HIF-1α siRNA or chetomin significantly reduced the hypoxia-inducible radioresistance of MG-63 cells. However, siRNA and chetomin showed different effects on the radiosensitivity under normoxic conditions.

CONCLUSIONS

Our results indicate that inhibition of HIF-1α effectively decreases hypoxia-induced transcription and radiosensitizes hypoxic MG-63 human osteosarcoma cells in vitro.

Antiproliferative and apoptotic effects of β-elemene on human hepatoma HepG2 cells

Background

β-elemene, a natural sesquiterpene extracted from the essential oils of Curcuma aromatica Salisb, has been shown to be effective against a wide range of tumors. In this study, the antitumor effect of β-elemene on a human hepatoma cell line, HepG2, and the mechanism involved have been investigated.

Methods

MTT assay was used to determine the growth inhibition of hepatoma HepG2 cells in vitro. Apoptosis of HepG2 cells were demonstrated by fluorescence microscope with Hoechst 33258 staining and flow cytometry with Annexin V-FITC/PI double staining. Flow cytometry was performed to analyze the cell cycle distribution of HepG2 cells. The mRNA and protein expression of Fas and FasL were measured by RT-PCR and Western blot analysis.

Results

MTT results showed that β-elemene could inhibit the proliferation of HepG2 cells in a time- and dose- dependent manner. Our results showed β-elemene had positive effect on apoptosis through fluorescence microscope and flow cytometry assay. Furthermore, β-elemene could induce the cell cycle arrest of the HepG2 cells in the G₂/M phase. Fas and FasL expression were obviously increased after β-elemene treatment in both mRNA and protein level.

Conclusion

The present study indicates that β-elemene can effectively inhibit proliferation and induce apoptosis in hepatoma HepG2 cells, and the apoptosis induction is related with up-regulating of Fas/FasL expression.