The cucurbitacins E, D and I: Investigation of their cytotoxicity toward human chondrosarcoma SW 1353 cell line and their biotransformation in man liver

Synergistic effect of cucurbitacin E and myricetin on Anti-Non-Small cell lung cancer: Molecular mechanism and therapeutic potential

BACKGROUND

Non-small cell lung cancer (NSCLC) is associated with extremely high morbidity and mortality rates worldwide. Citrullus colocynthis (L.) Schrad, widely distributed in Asian and African countries, is used to treat cancers in traditional Uyghur medicine.

HYPOTHESIS/PURPOSE

The combination of Cucurbitacin E (CuE) and Myricetin (Myr) of C. colocynthis could treat NSCLC by targeting autophagy.

STUDY DESIGN

The potential anti-cancer components (CuE and Myr) of C. colocynthis were identified using in-silico methods and further in vitro explored the anti-NSCLC properties of the combination of CuE and Myr.

METHODS

Network pharmacology and molecular docking were used to identify potential therapeutic compounds of C. colocynthis for the treatment of NSCLC. In A549 cells, the anti-cancer activities and synergy of CuE and Myr were studied using CompuSyn, their mechanism behind autophagy regulation was determined by western blotting and immunofluorescence staining.

RESULTS

CuMy-12 (CuE: 0.5 µM, Myr: 20 µM), a combination of CuE and Myr from C. colocynthis, inhibited A549 cell proliferation and colony formation, and induced apoptosis and cell cycle arrest in the G0/G1 phase, exhibiting a synergistic effect. Furthermore, CuMy-12 inhibited autophagy and activation of the PI3K/AKT/mTOR signaling pathway, which was characterized by a decrease in Beclin 1, AKT, and phospho-AKT proteins.

CONCLUSION

CuMy-12 can be considered a natural candidate with anticancer activity for autophagy-based regulation, but mechanistic and clinical studies are required to validate its potential.

Pharmacokinetics and Biological Activity of Cucurbitacins

Cucurbitacins are a class of secondary metabolites initially isolated from the Cucurbitaceae family. They are important for their analgesic, anti-inflammatory, antimicrobial, antiviral, and anticancer biological actions. This review addresses pharmacokinetic parameters recently reported, including absorption, metabolism, distribution, and elimination phases of cucurbitacins. It includes recent studies of the molecular mechanisms of the biological activity of the most studied cucurbitacins and some derivatives, especially their anticancer capacity, to propose the integration of the pharmacokinetic profiles of cucurbitacins and the possibilities of their use. The main botanical genera and species of American origin that have been studied, and others whose chemo taxonomy makes them essential sources for the extraction of these metabolites, are summarized.

Cucurbitacin I exhibits anticancer efficacy through induction of apoptosis and modulation of JAK/STAT3, MAPK/ERK, and AKT/mTOR signaling pathways in HepG2 cell line

Hepatocellular carcinoma is a common cancer type, especially among men. Although cucurbitacin I (CuI), widely found in plants belonging to the Ecballium elaterium (E. L) plant family, has been shown to have antitumorigenic properties in many cancer types, its anticancer effect, molecular mechanism, and apoptotic effect mediated by signal pathways on hepatocellular carcinoma have not been fully clarified. In the present study, we investigated the anticancer effect of CuI treated at different doses on the HepG2 cell line and the underlying mechanism in vitro. High-purity CuI was obtained from the E. elaterium plant with the aid of HPLC. The effects of this substance on the viability of cells were studied by the MTT assay. The effects of CuI on cell cycle progression and apoptosis were studied with flow cytometry. DNA breaks were analyzed by the Comet assay method. The proteins and genes involved in the JAK/STAT3, MAPK/ERK, and AKT/mTOR signaling pathways were investigated using Western blot and qRT-PCR, respectively. The results of this study demonstrated that CuI significantly reduced HepG2 cell growth in vitro, induced antiproliferation, and G2/M phase of the cell cycle was interrupted. PRACTICAL APPLICATIONS: CuI administration was shown to downregulate the levels of proteins in the PI3K/AKT/mTOR, MAPK, and JAK2/STAT3 cascades in HepG2 cells. CuI also reduced the expression of MAPK, STAT3, mTOR, JAK2, and Akt genes in different concentrations. DNA breaks are formed as a result of this effect. CuI, by reducing cell proliferation and promoting apoptosis, was found to have potential as a chemotherapeutic agent of hepatocellular carcinoma.

Cell-modified plasmonic interface for the signal-amplified detection of Cucurbitacin E

Cucurbitacin E (CuE) plays an important role in anticancer, antichemical carcinogenesis, and body immunity, etc., and the detection of its concentration is meaningful to pharmacological studies and clinical applications. However, the small molecular weight of CuE makes direct detection difficult through a surface plasmon resonance (SPR) sensor. In this work, we propose a cells-amplified signal strategy at the plasmonic interface, realizing the detection of CuE with ultra-low concentration. The seeded HeLa cells are modified onto the surface of the SPR sensor, and a small amount of CuE can lead to the remarkable morphology change of cells and the release of cell-related substances onto the plamonic interface, thus significantly amplifying the signal. Experimental results show that by using an unmodified SPR sensor with the bulk refractive index sensitivity of 2367.3 nm/RIU (RIU: refractive index unit), there no effective signal can be detected during the CuE concentration range of 0-100 nM; whereas, employing the proposed strategy, the signal for CuE detection can be significantly enhanced, resulting in a high detection sensitivity of 0.6196 nm/nM, corresponding to a limit of detection of 45.2 pM (25.2 pg/mL). The proposed cells-based signal amplifying strategy shows great potential applications in drug screening or bio-sensing to small molecules with low concentration.

Perspectives on natural compounds in chemoprevention and treatment of cancer: an update with new promising compounds

Cancer is the second deadliest disease worldwide. Although recent advances applying precision treatments with targeted (molecular and immune) agents are promising, the histological and molecular heterogeneity of cancer cells and huge mutational burdens (intrinsic or acquired after therapy) leading to drug resistance and treatment failure are posing continuous challenges. These recent advances do not negate the need for alternative approaches such as chemoprevention, the pharmacological approach to reverse, suppress or prevent the initial phases of carcinogenesis or the progression of premalignant cells to invasive disease by using non-toxic agents. Although data are limited, the success of several clinical trials in preventing cancer in high-risk populations suggests that chemoprevention is a rational, appealing and viable strategy to prevent carcinogenesis. Particularly among higher-risk groups, the use of safe, non-toxic agents is the utmost consideration because these individuals have not yet developed invasive disease. Natural dietary compounds present in fruits, vegetables and spices are especially attractive for chemoprevention and treatment because of their easy availability, high margin of safety, relatively low cost and widespread human consumption. Hundreds of such compounds have been widely investigated for chemoprevention and treatment in the last few decades. Previously, we reviewed the most widely studied natural compounds and their molecular mechanisms, which were highly exploited by the cancer research community. In the time since our initial review, many promising new compounds have been identified. In this review, we critically review these promising new natural compounds, their molecular targets and mechanisms of anticancer activity that may create novel opportunities for further design and conduct of preclinical and clinical studies.

Molecular genomic features associated with in vitro response of the NCI-60 cancer cell line panel to natural products

Natural products remain a significant source of anticancer chemotherapeutics. The search for targeted drugs for cancer treatment includes consideration of natural products, which may provide new opportunities for antitumor cytotoxicity as single agents or in combination therapy. We examined the association of molecular genomic features in the well-characterized NCI-60 cancer cell line panel with in vitro response to treatment with 1302 small molecules which included natural products, semisynthetic natural product derivatives, and synthetic compounds based on a natural product pharmacophore from the Developmental Therapeutics Program of the US National Cancer Institute's database. These compounds were obtained from a variety of plant, marine, and microbial species. Molecular information utilized for the analysis included expression measures for 23059 annotated transcripts, lncRNAs, and miRNAs, and data on protein-changing single nucleotide variants in 211 cancer-related genes. We found associations of expression of multiple genes including SLFN11, CYP2J2, EPHX1, GPC1, ELF3, and MGMT involved in DNA damage repair, NOTCH family members, ABC and SLC transporters, and both mutations in tyrosine kinases and BRAF V600E with NCI-60 responses to specific categories of natural products. Hierarchical clustering identified groups of natural products, which correlated with a specific mechanism of action. Specifically, several natural product clusters were associated with SLFN11 gene expression, suggesting that potential action of these compounds may involve DNA damage. The associations between gene expression or genome alterations of functionally relevant genes with the response of cancer cells to natural products provide new information about potential mechanisms of action of these identified clusters of compounds with potentially similar biological effects. This information will assist in future drug discovery and in design of new targeted cancer chemotherapy agents.

Cucurbitacin E and I target the JAK/STAT pathway and induce apoptosis in Sézary cells

Cutaneous T-cell lymphomas and leukemias (CTCLs) are a heterogeneous group of extranodal non-Hodgkin's lymphomas. These are characterized by an accumulation of malignant CD4⁺ T-lymphocytes in the skin, lymph nodes, and peripheral blood. Novel treatment options are needed for patients who progress to advanced stage disease. Cucurbitacin I has previously shown promising results in Sézary syndrome (Sz). A plethora of cucurbitacins, however, have not yet been tested in CTCL. Herein, we investigated the effect of cucurbitacin E and I in two CTCL cell lines. We show that both cucurbitacins decrease viability and cause apoptosis in these cell lines, although HuT-78 was more affected than SeAx (IC₅₀ of 17.38 versus 22.01 μM for cucurbitacin E and 13.36 versus 24.47 μM for cucurbitacin I). Moreover, both cucurbitacins decrease viability of primary cells of a Sz patient (56.46% for cucurbitacin E and 59.07% for cucurbitacin I). Furthermore, while JAK2 inhibition leads to decreased viability in SeAx cells (IC₅₀ of 9.98 and 29.15 μM for AZD1480 and ruxolitinib respectively), both JAK1 and JAK3 do not. This suggests that JAK2 has a preferential role in promoting survival. Western blotting in SeAx cells revealed that both cucurbitacins inhibit STAT3 activation (P < 0.0001), while only cucurbitacin I inhibits STAT5 activation (P = 0.05). This suggests that STAT3 plays a preferential role in the mechanism of action of these cucurbitacins. Nevertheless, a role of STAT5 and JAK2 cannot be excluded and should be explored further. This knowledge could contribute to the development of effective therapies for CTCL and other malignancies involving dysfunction of the JAK/STAT pathway.

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Cucurbitacin E and I decrease viability and cause apoptosis in Sézary cell lines

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Both cucurbitacins decrease viability of primary cells of a Sézary patient

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STAT3 appears to play a role in the mechanism of action of cucurbitacin E and I

Cytotoxicity of cucurbitacin E from Citrullus colocynthis against multidrug-resistant cancer cells

BACKGROUND

Cucurbitacin E (CuE) is an oxygenated tetracyclic triterpenoid isolated from the fruits of Citrullus colocynthis (L.) Schrad.

PURPOSE

This study outlines CuE's cytotoxic activity against drug-resistant tumor cell lines. Three members of ABC transporters superfamily, P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and ABCB5 were investigated, whose overexpression in tumors is tightly linked to multidrug resistance. Further factors of drug resistance studied were the tumor suppressor TP53 and the epidermal growth factor receptor (EGFR).

METHODS

Cytotoxicity assays (resazurin assays) were used to investigate the activity of Citrullus colocynthis and CuE towards multidrug resistant cancer cells. Molecular docking (In silico) has been carried out to explore the CuE's mode of binding to ABC transporters (P-gp, BCRP and ABCB5). The visualization of doxorubicin uptake was done by a Spinning Disc Confocal Microscope. The assessment of proteins expression was done by western blotting analysis. COMPARE and hierarchical cluster analyses were applied to identify, which genes correlate with sensitivity or resistance to cucurbitacins (CuA, CuB, CuE, CuD, CuI, and CuK).

RESULTS

Multidrug-resistant cells overexpressing P-gp or BCRP were cross-resistant to CuE. By contrast, TP53 knock-out cells were sensitive to CuE. Remarkably, resistant cells transfected with oncogenic ΔEGFR or ABCB5 were hypersensitive (collateral sensitive) to CuE. In silico analyses demonstrated that CuE is a substrate for P-gp and BCRP. Immunoblot analyses highlighted that CuE targeted EGFR and silenced its downstream signaling cascades. The most striking result that emerged from the doxorubicin uptake by ABCB5 overexpressing cells is that CuE is an effective inhibitor for ABCB5 transporter when compared with verapamil. The COMPARE analyses of transcriptome-wide expression profiles of tumor cell lines of the NCI identified common genes involved in cell cycle regulation, cellular adhesion and intracellular communication for different cucurbitacins.

CONCLUSION

CuE represents a potential therapeutic candidate for the treatment of certain types of refractory tumors. To best of our knowledge, this is the first time to identify CuE and verapamil as inhibitors for ABCB5 transporter.

Pharmacokinetics of cucurbitacin B from Trichosanthes cucumerina L. in rats

BACKGROUND

Cucurbitacin B is the major bioactive constituent in Trichosanthes cucumerina L. fruits, which the pharmacological properties have been studied for decades particularly an anti-tumor activity. The pharmacokinetic profile of this compound is still limited and investigation is needed for further phytopharmaceutical product development. This study aimed to investigate the pharmacokinetic profile of cucurbitacin B after administering the compound at different doses and routes to rats.

METHODS

Male Wistar rats (n = 6) were treated by cucurbitacin B extracted from Trichosanthes cucumerina L. The cucurbitacin B was administered at 0.1 mg/kg intravenously or by oral gavage at 2-4 mg/kg. Blood samples and internal organs were collected serially within 24 h after administration. Urine and feces were collected from time 0 to 48 h. The level of cucurbitacin B in biological samples was determined by liquid chromatography-tandem mass spectrometry.

RESULTS

The absolute oral bioavailability of cucurbitacin B was approximately 10%. The maximum concentration in plasma after normalization by dose ranged from 4.85-7.81 μg/L and the time to reach maximum value was approximately within 30 min after oral dosing. The level of cucurbitacin B in plasma increased proportionally to the given dose. After intravenous administration, cucurbitacin B had a large volume of distribution of about 51.65 L/kg and exhibited a high tissue to plasma concentration ratio, approximately 60 to 280-fold in several organs. Negligible amount of unchanged cucurbitacin B could be detected in urine and feces and accounted less than 1% of administered dose.

CONCLUSION

Cucurbitacin B had low oral bioavailability, but could be distributed extensively into internal organs with a high volume of distribution and tissue to plasma ratio. Only negligible amounts of unchanged cucurbitacin B were excreted via urine and feces suggesting that the compound might be biotransformed before undergoing an excretion. Further studies of the metabolic pathway and tissue uptake mechanism are required to strategize the future development of cucurbitacin B into clinical studies.

Colocynthenins A-D, Ring-A seco-Cucurbitane Triterpenoids from the Fruits of Citrullus colocynthis

Four ring-A seco-cucurbitane triterpenoids, colocynthenins A-D (1-4), together with seven known cucurbitane triterpenoids (5-11), were isolated from the fruits of Citrullus colocynthis. Their structures and absolute configurations were elucidated based on spectroscopic analysis and quantum chemical ECD calculations. Compound 1 possesses an unprecedented 2,11-lactone moiety, while compound 2 is the first reported cucurbitane triterpenoid with an unusual cyano group. Compounds 1 and 3 showed acetylcholinesterase inhibitory activities in a standard in vitro assay, with IC₅₀ values of 2.6 and 3.1 μM, respectively.

Cucurbitacins: elucidation of their interactions with the cytoskeleton

Cucurbitacins, a class of toxic tetracyclic triterpenoids in Cucurbitaceae, modulate many molecular targets. Here we investigated the interactions of cucurbitacin B, E and I with cytoskeletal proteins such as microtubule and actin filaments. The effects of cucurbitacin B, E and I on microtubules and actin filaments were studied in living cells (Hela and U2OS) and in vitro using GFP markers, immunofluorescence staining and in vitro tubulin polymerization assay. Cucurbitacin B, E and I apparently affected microtubule structures in living cells and cucurbitacin E inhibited tubulin polymerization in vitro with IC50 value of 566.91 ± 113.5 µM. Cucurbitacin E did not affect the nucleation but inhibited the growth phase and steady state during microtubule assembly in vitro. In addition, cucurbitacin B, E and I all altered mitotic spindles and induced the cell cycle arrest at G2/M phase. Moreover, they all showed potent effects on actin cytoskeleton by affecting actin filaments through the depolymerization and aggregation. The interactions of cucubitacin B, E and I with microtubules and actin filaments present new insights into their modes of action.

Cucurbitacins: A Systematic Review of the Phytochemistry and Anticancer Activity

Cucurbitacins are highly oxidized tetracyclic triterpenoids that are widely present in traditional Chinese medicines (Cucurbitaceae family), possess strong anticancer activity, and are divided into 12 classes from A to T with over 200 derivatives. The eight most active cucurbitacin components against cancer are cucurbitacin B, D, E, I, IIa, L glucoside, Q, and R. Their mechanisms of action include antiproliferation, inhibition of migration and invasion, proapoptosis, and cell cycle arrest promotion. Cucurbitacins are also found to be the inhibitors of JAK-STAT3, Wnt, PI3K/Akt, and MAPK signaling pathways, which play important roles in the apoptosis and survival of cancer cells. Recently, new studies have discovered synergistic anticancer effects by using cucurbitacins together with clinically approved chemotherapeutic drugs, such as docetaxel and methotrexate. This paper provides a summary of recent research progress on the anticancer property of cucurbitacins and the various intracellular signaling pathways involved in the regulation of cancer cell proliferation, death, invasion, and migration. Therefore, cucurbitacins are a class of promising anticancer drugs to be used alone or be intergraded in current chemotherapies and radiotherapies to treat many types of cancers.

Cucurbitacins from the Leaves of Citrullus colocynthis (L.) Schrad

Two new tetracyclic cucurbitane-type triterpene glycosides were isolated from an ethyl acetate extract of Citrullus colocynthis leaves together with four known cucurbitacins. Their structures were established on the basis of their spectroscopic data (mainly NMR and mass spectrometry). Evaluation of the in vitro cytotoxic activity of the isolated compounds against two human colon cancer cell lines (HT29 and Caco-2) and one normal rat intestine epithelial cell line (IEC6), revealed that one of the isolated compounds presented interesting specific cytotoxic activity towards colorectal cell lines.

In vitro and in vivo evaluation of cucurbitacin E on rat hepatic CYP2C11 expression and activity using LC-MS/MS

This study explored the effects of cucurbitacin E (CuE), a bioactive compound from Cucurbitaceae, on the metabolism/pharmacokinetic of tolbutamide, a model CYP2C9/11 probe substrate, and hepatic CYP2C11 expression in rats. Liquid chromatography-(tandem) mass spectrometry (LC-MS/MS) assay was used to detect tolbutamide as well as 4-hydroxytolbutamide, and then successfully applied to the pharmacokinetic study of tolbutamide in rats. The effect of CuE on CYP2C11 expression was determined by western blot. CuE (1.25-100 μmol L^-1) competitively inhibited tolbutamide 4-hydroxylation (CYP2C11) activity only in concentration-dependent manner with a K _i value of 55.5 μmol L^-1 in vitro. In whole animal studies, no significant difference in metabolism/pharmacokinetic of tolbutamide was found for the single pretreatment groups. In contrast, multiple pretreatments of CuE (200 μg kg^-1 d^-1, 3 d, i.p.) significantly decreased tolbutamide clearance (CL) by 25% and prolonged plasma half-time (T _1/2) by 37%. Moreover, CuE treatment (50-200 μg kg^-1 d^-1, i.p.) for 3 d did not affect CYP2C11 expression. These findings demonstrated that CuE competitively inhibited the metabolism of CYP2C11 substrates but had no effect on rat CYP2C11 expression. This study may provide a useful reference for the reasonable and safe use of herbal or natural products containing CuE to avoid unnecessary drug-drug interactions.

Brain-derived neurotrophic factor increases vascular endothelial growth factor expression and enhances angiogenesis in human chondrosarcoma cells

Chondrosarcomas are a type of primary malignant bone cancer, with a potent capacity for local invasion and distant metastasis. Brain-derived neurotrophic factor (BDNF) is commonly upregulated during neurogenesis. The aim of the present study was to examine the mechanism involved in BDNF-mediated vascular endothelial growth factor (VEGF) expression and angiogenesis in human chondrosarcoma cells. Here, we knocked down BDNF expression in chondrosarcoma cells and assessed their capacity to control VEGF expression and angiogenesis in vitro and in vivo. We found knockdown of BDNF decreased VEGF expression and abolished chondrosarcoma conditional medium-mediated angiogenesis in vitro as well as angiogenesis effects in vivo in the chick chorioallantoic membrane and Matrigel plug nude mouse models. In addition, in the xenograft tumor angiogenesis model, the knockdown of BDNF significantly reduced tumor growth and tumor-associated angiogenesis. BDNF increased VEGF expression and angiogenesis through the TrkB receptor, PLCγ, PKCα, and the HIF-1α signaling pathway. Finally, we analyzed samples from chondrosarcoma patients by immunohistochemical staining. The expression of BDNF and VEGF protein in 56 chondrosarcoma patients was significantly higher than in normal cartilage. In addition, the high level of BDNF expression correlated strongly with VEGF expression and tumor stage. Taken together, our results indicate that BDNF increases VEGF expression and enhances angiogenesis through a signal transduction pathway that involves the TrkB receptor, PLCγ, PKCα, and the HIF-1α. Therefore, BDNF may represent a novel target for anti-angiogenic therapy for human chondrosarcoma.

Inducement of mitosis delay by cucurbitacin E, a novel tetracyclic triterpene from climbing stem of Cucumis melo L., through GADD45γ in human brain malignant glioma (GBM) 8401 cells

Cucurbitacin E (CuE) is a natural compound previously shown to have anti-feedant, antioxidant and antitumor activities as well as a potent chemo-preventive action against cancer. The present study investigates its anti-proliferative property using MTT assay; CuE demonstrated cytotoxic activity against malignant glioma GBM 8401 cells and induced cell cycle G₂/M arrest in these cells. CuE-treated cells accumulated in metaphase (CuE 2.5–10 μM) as determined using MPM-2 by flow cytometry. We attempted to characterize the molecular pathways responsible for cytotoxic effects of CuE in GBM 8401 cells. We studied the genome-wide gene expression profile on microarrays and molecular networks by using pathway analysis tools of bioinformatics. The CuE reduced the expression of 558 genes and elevated the levels of 1354 genes, suggesting an existence of the common pathways involved in induction of G₂/M arrest. We identified the RB (GADD45β and GADD45γ) and the p53 (GADD45α) signaling pathways as the common pathways, serving as key molecules that regulate cell cycle. Results indicate that CuE produced G₂/M arrest as well as the upregulation of GADD45 γ and binding with CDC2. Both effects increased proportionally with the dose of CuE, suggesting that the CuE-induced mitosis delay is regulated by GADD45γ overexpression. Our findings suggest that, in addition to the known effects on cancer prevention, CuE may have antitumor activity in glioma therapy.

Morphological and physicochemical characterization of liposomes loading cucurbitacin E, an anti-proliferative natural tetracyclic triterpene

Cucurbitacin E (Cuc E), an oxygenated triterpene molecule, has demonstrated anti-proliferative effect on various cancer cells. Here, we examined the effect of Cuc E on the membrane morphology and properties using differential scanning calorimetry, transmission electron microscopy and atomic force microscopy techniques. Dipalmitoylphosphatidylcholine vesicles were prepared by the thin film hydration method in the absence and presence of Cuc E at molar ratios 100:12 and 100:20. The loading efficiency of Cuc E was found to be higher than 98% upon HPLC analysis. The thermodynamic parameters suggest that Cuc E does not penetrate into the bilayers and interacts with the polar/apolar interface of the lipid membranes. Blank and Cuc E loaded liposomes prepared from a mixture of DPPC/DPPE/DPPG/Cho were imaged by TEM and AFM. Images obtained by TEM revealed unilamellar liposomes for blank and Cuc E loaded liposomes. AFM images showed that the size and the height of Cuc E loaded liposomes were respectively smaller and higher than blank ones. Results suggest that Cuc E produces modifications in the lipid membrane structures.

Cucurbitacin E as inducer of cell death and apoptosis in human oral squamous cell carcinoma cell line SAS

Human oral squamous cell carcinoma (OSCC) is a common form of malignant cancer, for which radiotherapy or chemotherapy are the main treatment methods. Cucurbitacin E (CuE) is a natural compound previously shown to be an antifeedant as well as a potent chemopreventive agent against several types of cancer. The present study investigates anti-proliferation (using MTT assay, CuE demonstrated cytotoxic activity against SAS cell with IC50 values at 3.69 µM) and induced apoptosis of human oral squamous cell carcinoma SAS cells after 24 h treatment with CuE. Mitochondrial membrane potential (MMP) and caspase activity were studied and our results indicate that CuE inhibits cell proliferation as well as the activation of apoptois in SAS cells. Both effects increased in proportion to the dosage of CuE and apoptosis was induced via mitochondria- and caspase-dependent pathways. CuE can induce cell death by a mechanism that is not dependent on apoptosis induction, and thus represents a promising anticancer agent for prevention and treatment of OSCC.