Antineoplastic potential of curcumin (cooperative study in Bulgaria and Germany)

The unfavorable safety of existing anticancer medications and the issue of multidrug resistance have fuelled the search for novel plant compounds as potential antineoplastic agents. One of the used approaches for identifying perspective candidates is based on ethnopharmacology. Curcumin is the yellow pigment of curry and has being employed in traditional Indian medicine. Within the EU it has the status of food ingredient (E100) and remains in many food additives. It is isolated from Curcuma longa L. and has been reported as NF-κB inhibitor and apoptosis inducer with antioxidant, cholesterol lowering, anti-inflammatory, anti-parasitic, antibacterial and antitumor potential. Curcumin has been shown to exert a wide spectrum of pleiotropic activities including antitumor effects and protection of the normal bone marrow. It possesses antineoplastic activity in various malignant cell lines in vitro, such as cutaneous T cell lymphoma, acute myeloid leukemia and urinary bladder cancer cells. In lymphoma and leukemia cell lines curcumin induces apoptosis as evidenced by caspase activation, PARP cleavage and oligonucleosomal DNA fragmentation. Expression of the myeloid marker CD13 (aminopeptidase N) is associated with faster apoptosis induction. In addition, curcumin causes concentration-dependent glutathione level increase. Application of curcumin in vivo resulted in protection against cisplatin-induced chromosomal aberrations (anticlastogenic effect). This finding reveals curcumin as preferable partner for combinations with antineoplastic agents in order to potentiate their activity and ameliorate the adverse effects. There is a clear need for new curcumin formulations because of its low bioavailability after oral intake. Cutaneous and intravesical curcumin applications remain a possibility for successful clinical use of curcumin.     

Nonsteroidal anti-inflammatory drugs and oxidative stress in cancer cells

Nonsteroidal antiinflammatory drugs (NSAIDs) induce apoptosis in a variety of cancer cells, including those of colon, prostate, breast and leukemia. In addition, the classical NSAIDs sulindac and aspirin are promising chemopreventive agents against colon cancer. NSAIDs inhibit cyclooxygenases (COX) preventing the formation of prostaglandins, prostacyclin and thromboxane. NSAIDs also exert other biological effects, including generation of reactive oxygen species (ROS) and inhibition of NF-kappaB-mediated signals. Despite many suggested mechanisms for their anticancer effects, it remains uncertain how they induce cell cycle arrest and apoptosis in cancer cells. Furthermore, there is little information on the selectivity of NSAIDs-mediated anticancer effects, although this is one of the most important issues in cancer therapy. Increased understanding of the biological basis for the anticancer activity of NSAIDs and their selectivity is essential for future therapeutic advances. In this paper, we propose that increased ROS generation is one of the key mechanisms for NSAIDs-mediated anticancer effects on various cancer cells.     

Effects and underlying mechanisms of curcumin on the proliferation of vascular smooth muscle cells induced by Chol:MβCD

Proliferation of vascular smooth muscle cells (VSMCs) contributes to the development of various cardiovascular diseases. Curcumin, extracted from Curcumae longae, has been shown a variety of beneficial effects on human health, including anti-atherosclerosis by mechanisms poorly understood. In the present study, we attempted to investigate whether curcumin has any effect on VSMCs proliferation and the potential mechanisms involved. Our data showed curcumin concentration-dependently abrogated the proliferation of primary rat VSMCs induced by Chol:MβCD. To explore the underlying cellular and molecular mechanisms, we found that curcumin was capable of restoring caveolin-1 expression which was reduced by Chol:MβCD treatment. Moreover, curcumin abrogated the increment of phospho-ERK1/2 and nuclear accumulation of ERK1/2 in primary rat VSMCs induced by Chol:MβCD, which led to a suppression of AP-1 promoter activity stimulated by Chol:MβCD. In addition, curcumin was able to reverse cell cycle progression induced by Chol:MβCD, which was further supported by its down-regulation of cyclinD1 and E2F promoter activities in the presence of Chol:MβCD. Taking together, our data suggest curcumin inhibits Chol:MβCD-induced VSMCs proliferation via restoring caveolin-1 expression that leads to the suppression of over-activated ERK signaling and causes cell cycle arrest at G1/S phase. These novel findings support the beneficial potential of curcumin in cardiovascular disease.     

姜黄素对肝癌细胞HepG2 的抗癌作用及P21WAF1/CIP1 表达的影响

目的:探讨姜黄素对肝癌HepG2细胞抗癌作用及相关周期蛋白依赖激酶抑制因子P21WAF1/CIP1表达的影响.方法:体外培养肝癌HepG2细胞,用MTT法检测姜黄素对HepG2细胞的抑制作用,以RT-PCR方法检测HepG2细胞中P21WAF1/CIP1mRNA的表达,用免疫细胞化学检测其P21WAF1/CIP1蛋白的表达.结果:姜黄素呈时间剂量性抑制HepG2细胞的生长,并显著上调HepG2细胞中P21WAF1/CIP1mRNA和蛋白的表达.结论:姜黄素能抑制HepG2细胞的生长,并上调其中P21WAF1/CIP1的表达.     

Curcumin as a natural regulator of monocyte chemoattractant protein-1

Monocyte chemoattractant/chemotactic protein-1 (MCP-1), a member of the CC chemokine family, is one of the key chemokines that regulate migration and tissue infiltration of monocytes/macrophages. Its role in the pathophysiology of several inflammatory diseases has been widely recognized, thus making MCP-1 a possible target for anti-inflammatory treatments. Curcumin (diferuloylmethane) is a natural polyphenol derived from the rhizomes of Curcuma Longa L. (turmeric). Anti-inflammatory action underlies numerous pharmacological effects of curcumin in the control and prevention of several diseases. The purpose of this review is to evaluate the effects of curcumin on the regulation of MCP-1 as a key mediator of chemotaxis and inflammation, and the biological consequences thereof. In vitro studies have shown that curcumin can decrease MCP-1 production in various cell lines. Animal studies have also revealed that curcumin can attenuate MCP-1 expression and improve a range of inflammatory diseases through multiple molecular targets and mechanisms of action. There is limited data from human clinical trials showing the decreasing effect of curcumin on MCP-1 concentrations and improvement of the course of inflammatory diseases. Most of the in vitro and animal studies confirm that curcumin exert its MCP-1-lowering and anti-inflammatory effects by down-regulating the mitogen-activated protein kinase (MAPK) and NF-κB signaling pathway. As yet, there is limited data from human clinical trials showing the effect of curcumin on MCP-1 levels and improvement of the course of inflammatory diseases. More evidence, especially from human studies, is needed to better assess the effects of curcumin on circulating MCP-1 in different human diseases and the role of this modulatory effect in the putative anti-inflammatory properties of curcumin.     

Curcumin-induced Aurora-A suppression not only causes mitotic defect and cell cycle arrest but also alters chemosensitivity to anticancer drugs

Overexpression of oncoprotein Aurora-A increases drug resistance and promotes lung metastasis of breast cancer cells. Curcumin is an active anticancer compound in turmeric and curry. Here we observed that Aurora-A protein and kinase activity were reduced in curcumin-treated human breast chemoresistant nonmetastatic MCF-7 and highly metastatic cancer MDA-MB-231 cells. Curcumin acts in a similar manner to Aurora-A small interfering RNA (siRNA), resulting in monopolar spindle formation, S and G2/M arrest, and cell division reduction. Ectopic Aurora-A extinguished the curcumin effects. The anticancer effects of curcumin were enhanced by Aurora-A siRNA and produced additivity and synergism effects in cell division and monopolar phenotype, respectively. Combination treatment with curcumin overrode the chemoresistance to four Food and Drug Administration (FDA)-approved anticancer drugs (ixabepilone, cisplatin, vinorelbine, or everolimus) in MDA-MB-231 cells, which was characterized by a decrease in cell viability and the occurrence of an additivity or synergy effect. Ectopic expression of Aurora-A attenuated curcumin-enhanced chemosensitivity to these four tested drugs. A similar benefit of curcumin was observed in MCF-7 cells treated with ixabepilone, the primary systemic therapy to patients with invasive breast cancer (stages IIA–IIIB) before surgery. Antagonism effect was observed when MCF-7 cells were treated with curcumin plus cisplatin, vinorelbine or everolimus. Curcumin-induced enhancement in chemosensitivity was paralleled by significant increases (additivity or synergy effect) in apoptosis and cell cycle arrest at S and G2/M phases, the consequences of Aurora-A inhibition. These results suggest that a combination of curcumin with FDA-approved anticancer drugs warrants further assessment with a view to developing a novel clinical treatment for breast cancer.     

Curcumin inhibits metastatic progression of breast cancer cell through suppression of urokinase-type plasminogen activator by NF-kappa B signaling pathways

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), is extracted from the plant Curcuma longa. It was recently reported for its anticancer effect on several types of cancer cells in vitro however, the molecular mechanisms of this anticancer effect are not fully understood. In the present study, we evaluated the effects of curcumin on human mammary epithelial carcinoma MCF-7 cells. Cells were treated with curcumin and examined for cell viability by MTT assay. The cells invasion was demonstrated by transwell assay. The binding activity of NF-κB to DNA was examined in nuclear extracts using Trans-AM NF-κB ELISA kit. Western blot was performed to detect the effect of curcumin on the expression of uPA. Our results showed that curcumin dose-dependently inhibited (P < 0.05) the proliferation of MCF-7 cells. Meanwhile, the adhesion and invasion ability of MCF-7 cells were sharply inhibited when treated with different concentrations of curcumin. Curcumin also significantly decreased (P < 0.05) the expression of uPA and NF-κB DNA binding activity, respectively. It is concluded that curcumin inhibits the adhesion and invasion of MCF-7 cells through down-regulating the protein expression of uPA via of NF-κB activation. Accordingly, the therapeutic potential of curcumin for breast cancer deserves further study.     

Natural antioxidants synergistically enhance the anticancer potential of AP9-cd, a novel lignan composition from Cedrus deodara in human leukemia HL-60 cells

Antioxidants have been used as adjuvant with anticancer therapy to synergize the potential of the anti-neoplastic therapeutics. Based on the fact, we have studied the effect of three natural antioxidants curcumin, silymarin and acteoside on AP9-cd (standardized lignan composition from Cedrus deodara) induced cytotoxicity in human leukemia HL-60 cells. The antioxidant potential of individual test compounds was first evaluated with ferric reducing antioxidant power (FRAP) test, which revealed that all four molecules behave as antioxidants. The apoptotic potential of AP9-cd was significantly enhanced in HL-60 cells in the presence of curcumin, silymarin and acteoside. It was confirmed by using various models like MTT assay, DNA fragmentation, nuclei condensation, sub-Go DNA population, Annexin-V-FITC binding, ROS depletion and immunoblotting in HL-60 cells. AP9-cd and individual antioxidants alone at low doses (10μg and 10μM, respectively) have meager or no cytotoxicity in HL-60 cells, whereas in mutual combinations, there were 2-3 times enhancement in Annexin-V-FITC and sub-Go DNA population. Moreover, prominent DNA ladders were observed at low doses of AP9-cd in combinations with various antioxidants. The Hoechst staining of the nucleus also revealed the same results for the HL-60 cells treated with AP9-cd and different antioxidants. The molecular diagnostics revealed that the combinations induced a strong antioxidant effect which was correlated with the downregulation of NF-κB expression in the nucleus. Out of the three antioxidants, curcumin was found to be more potent than acteoside and silymarin in terms of enhancing the apoptotic potential of AP9-cd. These results propose an important role of natural antioxidant as adjuvant to enhance the anticancer potential of AP9-cd and more likely other anti-neoplastic therapeutics.     

姜黄素对肝癌细胞HepG2的抗癌作用及P21WAF1/CIP1表达的影响

目的：探讨姜黄素对肝癌HepG2细胞抗癌作用及相关周期蛋白依赖激酶抑制因子P21WAF1/CIP1表达的影响。方法：体外培养肝癌HepG2细胞,用MTT法检测姜黄素对HepG2细胞的抑制作用,以RT-PCR方法检测HepG2细胞中P21WAF1/CIP1mRNA的表达,用免疫细胞化学检测其P21WAF1/CIP1蛋白的表达。结果：姜黄素呈时间剂量性抑制HepG2细胞的生长,并显著上调HepG2细胞中P21WAF1/CIP1mRNA和蛋白的表达。结论：姜黄素能抑制HepG2细胞的生长,并上调其中P21WAF1/CIP1的表达。     

Curcumin protects against thioacetamide-induced hepatic fibrosis by attenuating the inflammatory response and inducing apoptosis of damaged hepatocytes

Inflammation and hepatic stellate cell (HSC) activation are the most crucial steps in the formation of hepatic fibrosis. Hepatocytes damaged by viral or bacterial infection, alcohol or toxic chemicals initiate an inflammatory response that activates collagen production by HSCs. Recent studies indicate curcumin has liver-protective effects due to its anti-inflammatory, antioxidant and anticancer activities; however, the mechanisms are not well understood. In this study, we show that curcumin protected against hepatic fibrosis in BALB/c mice in vivo by inhibiting HSC activation, inflammatory responses and inducing apoptosis of damaged hepatocytes. Using the thioacetamide (TAA)-induced hepatic fibrosis animal model, we found that curcumin treatment up-regulated P53 protein expression and Bax messenger RNA (mRNA) expression and down-regulated Bcl-2 mRNA expression. Together, these responses increased hepatocyte sensitivity to TAA-induced cytotoxicity and forced the damaged cells to undergo apoptosis. Enhancing the tendency of damaged hepatocytes to undergo apoptosis may be the protective mechanism whereby curcumin suppresses inflammatory responses and hepatic fibrogenesis. These results provide a novel insight into the cause of hepatic fibrosis and the cytoprotective effects curcumin has on hepatic fibrosis suppression.     

Knockdown of Ki-67 by Dicer-Substrate Small Interfering RNA Sensitizes Bladder Cancer Cells to Curcumin-Induced Tumor Inhibition

Transitional cell carcinoma (TCC) of the urinary bladder is the most common cancer of the urinary tract. Most of the TCC cases are of the superficial type and are treated with transurethral resection (TUR). However, the recurrence rate is high and the current treatments have the drawback of inducing strong systemic toxicity or cause painful cystitis. Therefore, it would be of therapeutic value to develop novel concepts and identify novel drugs for the treatment of bladder cancer. Ki-67 is a large nucleolar phosphoprotein whose expression is tightly linked to cell proliferation, and curcumin, a phytochemical derived from the rhizome Curcuma longa, has been shown to possess powerful anticancer properties. In this study, we evaluated the combined efficacy of curcumin and a siRNA against Ki-67 mRNA (Ki-67-7) in rat (AY-27) and human (T-24) bladder cancer cells. The anticancer effects were assessed by the determination of cell viability, apoptosis and cell cycle analysis. Ki-67-7 (10 nM) and curcumin (10 µM), when treated independently, were moderately effective. However, in their combined presence, proliferation of bladder cancer cells was profoundly (>85%) inhibited; the rate of apoptosis in the combined presence of curcumin and Ki-67-7 (36%) was greater than that due to Ki-67-7 (14%) or curcumin (13%) alone. A similar synergy between curcumin and Ki-67-7 in inducing cell cycle arrest was also observed. Western blot analysis suggested that pretreatment with Ki-67-7 sensitized bladder cancer cells to curcumin-mediated apoptosis and cell cycle arrest by p53- and p21-independent mechanisms. These data suggest that a combination of anti-Ki-67 siRNA and curcumin could be a viable treatment against the proliferation of bladder cancer cells.     

Roles of the Akt/mTOR/p70S6K and ERK1/2 signaling pathways in curcumin-induced autophagy

Curcumin has a potent anticancer effect and is a promising new therapeutic strategy. We previously demonstrated that curcumin induced non-apoptotic autophagic cell death in malignant glioma cells in vitro and in vivo. This compound inhibited the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activated the extracellular signal-regulated kinases 1/2 thereby inducing autophagy. Interestingly, activation of the first pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the latter pathway inhibited curcumin-induced autophagy and induced apoptosis, thus augmenting the cytotoxicity of curcumin. These results imply that these two autophagic pathways have opposite effects on curcumin's cytotoxicity. However, inhibition of nuclear factor kappaB, which is the main target of curcumin for its anticancer effect, was not observed in malignant glioma cells. These results suggest that autophagy but not nuclear factor kappaB plays a central role in curcumin anticancer therapy and warrant further investigation toward application in patients with malignant gliomas. Here, we discuss the therapeutic role of two autophagic pathways influenced by curcumin.     

Enhanced anticancer potency of doxorubicin in combination with curcumin in gastric adenocarcinoma

Gastric cancer (GC) is one of the prevalent human malignancies and the third most common cause of cancer‐related death worldwide. The doxorubicin hydrochloride is one of the important chemotherapeutic anticancer agents, with a limited therapeutic efficacy for treatment of GC. Therefore, taking advantage of synergistic effects by strategies like combination therapy seems appropriate and promising in treatment of GC. The aim of this study was to investigate a novel method to enhance the therapeutic efficacy of doxorubicin (as a chemotherapeutic agent) by co‐administration of curcumin (as a bioactive herbal compound) in GC treatment. In the present study, the effects of curcumin, doxorubicin, and their combinations (Dox‐Cur) were evaluated on the viability, morphological features, tumor spheroid formation, migration, invasion, and apoptosis of gastric adenocarcinoma cell line (AGS). Moreover, expression levels of BAX, BCL‐2, and CASP9 genes were assessed among AGS cells treated with curcumin, doxorubicin, and Dox‐Cur. The obtained results showed that all of curcumin, doxorubicin, and Dox‐Cur treatments significantly decreased the viability, tumor spheroid formation, migration, and invasion in the GC model cells. Furthermore, apoptosis rates in AGS cells were increased in a concentration‐ and time‐dependent manner in all of the treatment groups. Moreover, the anticancer activity of the Dox‐Cur combination was significantly more than curcumin and doxorubicin treatments alone. According to the results, Dox‐Cur combination therapy exerts more profound apoptotic and anticancer effects on the AGS cell line than curcumin or doxorubicin monotherapy.     

1,7-Bis(4-hydroxyphenyl)-1,4-heptadien-3-one induces lung cancer cell apoptosis via the PI3K/Akt and ERK1/2 pathways

1,7-Bis(4-hydroxyphenyl)-1,4-heptadien-3-one (EB30) is a diarylheptanoid-like compound isolated from Viscum coloratum. This curcumin analog exhibits significant cytotoxic activity against HeLa, SGC-7901, and MCF-7 cells. However, little is known about the anticancer effects and mechanisms of EB30 in human lung cancer. The current study reports that EB30 significantly reduced the cell viability of A549 and NCI-H292 human lung cancer cells. Further examination revealed that EB30 not only induced cell cycle arrest and promoted the generation of reactive oxygen species (ROS) but also induced cell apoptosis through the intrinsic and extrinsic signaling pathways. Furthermore, EB30 upregulated the expression levels of p-ERK1/2 and p-P90RSK, whereas downregulating the phosphorylation of Akt and P70RSK. Cell viability was further inhibited by the combination of EB30 with LY294002 (a specific PI3K inhibitor) or U0126 (a MEK inhibitor). The current study indicates that EB30 is a potential anticancer agent that induces cell apoptosis via suppression of the PI3K/Akt pathway and activation of the ERK1/2 pathway.     

Augmented sensitivity to methotrexate by curcumin induced overexpression of folate receptor in KG-1 cells

Folate receptors are targets of various strategies aimed at efficient delivery of anti-cancer drugs. Folate receptors also play a role in the uptake of antifolate drugs which are used for therapeutic intervention in leukemia. Therefore, it is important to identify compounds which regulate expression of folate receptors in leukemic cells. The present study examined if curcumin could modulate the uptake and cytotoxicity of the antifolate drug methotrexate, in KG-1 leukemic cells. This is the first report to show that curcumin (10–50 μM) causes a significant, dose-dependent, 2–3 fold increase in uptake of radiolabelled folic acid and methotrexate into KG-1 cells both at 24 h and 48 h of treatment. Interestingly, pre-treatment of KG-1 leukemic cells with curcumin (10 μM and 25 μM) also caused a statistically significant enhancement in the cytotoxicity of methotrexate. We performed Real Time Quantitative RT-PCR to confirm the upregulation of FRβ mRNA in curcumin treated cells. Immunocytochemistry and Western blotting showed that curcumin caused increased expression of folate receptor βin KG-1 cells. Our data show that the mechanism of curcumin action involves up-regulation of folate receptor β mRNA and protein in KG-1 cells. Therefore, combination of non-toxic concentrations of curcumin and methotrexate, may be a viable strategy for therapeutic intervention for leukemias using a folate receptor-targeted drug delivery system.     

Roles of the Akt/mTOR/p70S6K and ERK1/2 Signaling Pathways in Curcumin-Induced Autophagy

Curcumin has a potent anticancer effect and is a promising new therapeutic strategy. We previously demonstrated that curcumin induced non-apoptotic autophagic cell death in malignant glioma cells in vitro and in vivo. This compound inhibited the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activated the extracellular signal-regulated kinases 1/2 thereby inducing autophagy. Interestingly, activation of the first pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the latter pathway inhibited curcumin-induced autophagy and induced apoptosis, thus augmenting the cytotoxicity of curcumin. These results imply that these two autophagic pathways have opposite effects on curcumin’s cytotoxicity. However, inhibition of nuclear factor κB, which is the main target of curcumin for its anticancer effect, was not observed in malignant glioma cells. These results suggest that autophagy but not nuclear factor κB plays a central role in curcumin anticancer therapy and warrant further investigation toward application in patients with malignant gliomas. Here, we discuss the therapeutic role of two autophagic pathways influenced by curcumin.

Addendum to:

Evidence That Curcumin Suppresses the Growth of Malignant Gliomas in Vitro and in Vivo through Induction of Autophagy: Role of Akt and Extracellular Signal-Regulated Kinase Signaling Pathways

H. Aoki, Y. Takada, S. Kondo, R. Sawaya, B. B. Aggarwal and Y. Kondo

Mol Pharmacol 2007; 72:29-39     

Synthesis,characterization and fluorescent properties of water-soluble glycopolymer bearing curcumin pendant residues

Curcumin is a potential natural anticancer drug with low oral bioavailability because of poor water solubility. The aqueous solubility of curcumin is enhanced by means of modification with the carbohydrate units. Polymerization of the curcumin-containing monomer with carbohydrate-containing monomer gives the water-soluble glycopolymer bearing curcumin pendant residues. The obtained copolymers (P1 and P2) having desirable water solubility were well-characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), UV–Vis absorption spectroscopy, and photoluminescence spectroscopy. The copolymer P2 with a molar ratio of 1:6 (curcumin/carbohydrate) calculated from the proton NMR results exhibits a similar anticancer activity compared to original curcumin, which may serve as a potential chemotherapeutic agent in the field of anticancer medicine.     

Curcumin potentiates the anti-leukemia effects of imatinib by downregulation of the AKT/mTOR pathway and BCR/ABL gene expression in Ph+ acute lymphoblastic leukemia

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is triggered by BCR/ABL and SRC family tyrosine kinases. They interact with each other and subsequently activate downstream growth-signaling pathways, including Raf/MEK/ERK, Akt/mTOR, and STAT5 pathways. Although imatinib is the standard treatment for Ph+ leukemia, response rate of Ph+ ALL to imatinib is low, relapse is frequent and quick. Studies have documented the potential anti-tumor activities of curcumin. However, whether curcumin can be used in the therapy for Ph+ ALL remains obscure. Here, we reported that curcumin induced apoptosis by inhibition of AKT/mTOR and ABL/STAT5 signaling, down-regulation of BCR/ABL expression, and induction of the BCL2/BAX imbalance. Curcumin exerted synergetic anti-leukemia effects with imatinib by inhibition of the imatinib-mediated overactivation of AKT/mTOR signaling and down-regulation of BCR/ABL gene expression. In primary samples from Ph+ ALL patients, curcumin inhibited cellular proliferation and down-regulated constitutive activation of growth-signaling pathways not only in newly diagnosed patients but also in imatinib-resistant patients. In Ph+ ALL mouse models, curcumin exhibited synergetic anti-leukemia effects with imatinib. These results demonstrated that curcumin might be a promising agent for Ph+ ALL patients.     

Stronger proteasomal inhibition and higher CHOP induction are responsible for more effective induction of paraptosis by dimethoxycurcumin than curcumin

Although curcumin suppresses the growth of a variety of cancer cells, its poor absorption and low systemic bioavailability have limited its translation into clinics as an anticancer agent. In this study, we show that dimethoxycurcumin (DMC), a methylated, more stable analog of curcumin, is significantly more potent than curcumin in inducing cell death and reducing the clonogenicity of malignant breast cancer cells. Furthermore, DMC reduces the tumor growth of xenografted MDA-MB 435S cells more strongly than curcumin. We found that DMC induces paraptosis accompanied by excessive dilation of mitochondria and the endoplasmic reticulum (ER); this is similar to curcumin, but a much lower concentration of DMC is required to induce this process. DMC inhibits the proteasomal activity more strongly than curcumin, possibly causing severe ER stress and contributing to the observed dilation. DMC treatment upregulates the protein levels of CCAAT-enhancer-binding protein homologous protein (CHOP) and Noxa, and the small interfering RNA-mediated suppression of CHOP, but not Noxa, markedly attenuates DMC-induced ER dilation and cell death. Interestingly, DMC does not affect the viability, proteasomal activity or CHOP protein levels of human mammary epithelial cells, suggesting that DMC effectively induces paraptosis selectively in breast cancer cells, while sparing normal cells. Taken together, these results suggest that DMC triggers a stronger proteasome inhibition and higher induction of CHOP compared with curcumin, giving it more potent anticancer effects on malignant breast cancer cells.