Curcumin Induced Cell Cycle Arrest Research Articles

Curcumin inhibits proliferation and promotes apoptosis of breast cancer cells.

Curcumin is a natural compound that appears to be promising for clinical application, as it has been shown in in vitro and in vivo studies to exert antitumor effects by modulating multiple signaling cellular pathways. In the present study, the antitumor effects of curcumin and its mechanism of action were investigated in cultured breast cancer cells. The MTT assay was used to determine the effect of curcumin on breast cancer cell proliferation, flow cytometry was used to detect alterations of the cell cycle, and western blot analysis was used to determine the expression of signaling molecules involved in the cell cycle, proliferation and apoptosis. The results revealed that curcumin significantly inhibited the proliferation of various breast cancer cell lines, such as T47D, MCF7, MDA-MB-231 and MDA-MB-468, with an IC50 at the micromolar level, indicating the potent antitumor activity of curcumin. In-depth study of its mechanism of action revealed that curcumin induced cell cycle arrest at the G2/M phase and decreased the expression of the CDC25 and CDC2 proteins, while increasing the expression of P21. In addition, curcumin inhibited the phosphorylation of protein kinase B (Akt)/mammalian target of rapamycin (mTOR), decreased B-cell lymphoma 2 (BCL2) and promoted BCL-2-associated X protein (BAX) and cleavage of caspase 3, subsequently inducing apoptosis of breast cancer cells. In conclusion, curcumin inhibited the proliferation of breast cancer cells and induced G2/M phase cell cycle arrest and apoptosis, which may be associated with the decrease of CDC25 and CDC2 and increase of P21 protein levels, as well as inhibition of the phosphorylation of Akt/mTOR and induction of the mitochondrial apoptotic pathway. The findings of the present study may provide a basis for the further study of curcumin in the treatment of breast cancer.

Curcumin enhances the anti-cancer effects of Paris Saponin II in lung cancer cells.

To investigate the synergistic mechanisms of Paris Saponin II (PSII) and Curcumin (CUR) in lung cancer. The combination changed the cellular uptake of CUR and PSII, apoptosis, cell cycle arrest and cytokine levels were analysed on different lung cancer cells. The combination displayed a synergistic anti-cancer effect through promoting the cellular uptake of CUR on different lung cancer cells. Hoechst H33258 staining and FACS assay indicated that the combination of PSII and CUR induced cell cycle arrest and apoptosis. Western blot and cytokine antibody microarray suggested that the combination activated death receptors such as DR6, CD40/CD40L, FasL and TNF-α to induce cancer cells apoptosis, and up-regulated IGFBP-1 leading to inhibition of PI3K/Akt pathway and increase of p21 and p27, which therefore induced a G2 phase arrest in NCI-H446 cells. Meanwhile, the combination suppressed PCNA and NF-κB pathway in 4 kinds of lung cancer cells. They activated the phosphorylation of p38 and JNK, and inhibited PI3K in NCI-H460 and NCI-H446 cells, enhanced the phosphorylation of JNK in NCI-H1299 cells, and increased the phosphorylation of p38 and ERK, and suppressed PI3K in NCI-H520 cells. PSII combined with CUR had a synergistic anti-cancer effect on lung cancer cells. These findings provided a rationale for using the combination of curcumin and PSII in the treatment of lung cancer in future.

Curcumin Inhibits Proliferation and Epithelial-Mesenchymal Transition of Retinal Pigment Epithelial Cells Via Multiple Pathways.

Proliferative vitreoretinopathy (PVR) is a disease caused by dedifferentiation, translocation and proliferation of several types of local cells. These cells form fibrocellular membranes resulting in detachment of retinal and vision loss. PVR occurs in 8%-10% of patients undergoing primary retinal detachment (RD) surgery and becomes a major obstacle for successful RD repair. Retinal pigment epithelial (RPE) cells are among the major cells which consist of fibrocellular membranes. Reproliferation and Epithelial-mesenchymal transition (EMT) are the primary pathological alteration of RPE cells in PVR. RPE cells were treated with curcumin at different concentrations for 24, 48 and 72 hours. The viable cells were detected by MTT assay. The apoptosis of RPE was stained by Multicaspase/7-AAD and detected using flow cytometry. Cell cycle analysis was quantified by PI staining. The mRNA levels were detected by real-time PCR. The protein levels were detected by western blot. We found a compound curcumin significantly inhibited proliferation and EMT of RPE cells in vitro. Further study showed curcumin induced cell cycle arrest by activating G2 checkpoint through p53 pathway. Meanwhile, we found that curcumin suppressed the AKT, MAPK and TGF-β pathways in RPE cells which may also affect proliferation and EMT. Our research identified curcumin a potential novel agent for the PVR prevention and treatment. Curcumin induces cell cycle arrest by activating G2 checkpoint. Our results in this study also provide the insights to broaden the application of curcumin in research and probably clinics.

Curcumin induces G2/M cell cycle arrest and apoptosis of head and neck squamous cell carcinoma in vitro and in vivo through ATM/Chk2/p53-dependent pathway.

Studies have demonstrated that curcumin (CUR) exerts its tumor suppressor function in a variety of human cancers including head and neck squamous cell carcinoma (HNSCC). However, the exact underlying molecular mechanisms remain obscure. Here, we aim to test whether CUR affects ATM/Chk2/p53 signaling pathway, leading to the induction of cell cycle arrest, inhibition of angiogenesis of HNSCC in vitro and in vivo. To this end, we conducted multiple methods such as MTT assay, Invasion assay, Flow cytometry, Western blotting, RT-PCR, and transfection to explore the functions and molecular insights of CUR in HNSCC. We observed that CUR significantly induced apoptosis and cell cycle arrest, inhibited angiogenesis in HNSCC. Mechanistically, we demonstrated that CUR markedly up-regulated ATM expression and subsequently down-regulated HIF-1α expression. Blockage of ATM production totally reversed CUR induced cell cycle arrest as well as anti-angiogenesis in HNSCC. Moreover, our results demonstrated that CUR exerts its antitumor activity through targeting ATM/Chk2/p53 signal pathway. In addition, the results of xenograft experiments in mice were highly consistent with in vitro studies. Collectively, our findings suggest that targeting ATM/Chk2/p53 signal pathway by CUR could be a promising therapeutic approach for HNSCC prevention and therapy.

The inhibition of PI3K and NFκB promoted curcumin-induced cell cycle arrest at G2/M via altering polyamine metabolism in Bcl-2 overexpressing MCF-7 breast cancer cells.

Bcl-2 protein has been contributed with number of genes which are involved in oncogenesis. Among the many targets of Bcl-2, NFκB have potential role in induction of cell cycle arrest. Curcumin has potential therapeutic effects against breast cancer through multiple signaling pathways. In this study, we investigated the role of curcumin in induction of cell cycle arrest via regulating of NFκB and polyamine biosynthesis in wt and Bcl-2+ MCF-7 cells. To examine the effect of curcumin on cell cycle regulatory proteins, PI3K/Akt, NFκB pathways and polyamine catabolism, we performed immunoblotting assay. In addition, cell cycle analysis was performed by flow cytometry. The results indicated that curcumin induced cell cycle arrest at G2/M phase by downregulation of cyclin B1 and Cdc2 and inhibited colony formation in MCF-7wt cells. However, Bcl-2 overexpression prevented the inhibition of cell cycle associated proteins after curcumin treatment. The combination of LY294002, PI3K inhibitor, and curcumin induced cell cycle arrest by decreasing CDK4, CDK2 and cyclin E2 in Bcl-2+ MCF-7 cells. Moreover, LY294002 further inhibited the phosphorylation of Akt in Bcl-2+ MCF-7 cells. Curcumin could suppress the nuclear transport of NFκB through decreasing the interaction of P-IκB-NFκB. The combination of wedelolactone, NFκB inhibitor, and curcumin acted different on SSAT expression in wt MCF-7 and Bcl-2+ MCF-7 cells. NFκB inhibition increased the SSAT after curcumin treatment in Bcl-2 overexpressed MCF-7 cells. Inhibition of NFκB activity as well as suppression of ROS generation with NAC resulted in the partial relief of cells from G2/M checkpoint after curcumin treatment in wt MCF-7 cells. In conclusion, the potential role of curcumin in induction of cell cycle arrest is related with NFκB-regulated polyamine biosynthesis.

Curcumin inhibits Ec109 cell growth via an AMPK-mediated metabolic switch.

Glycolytic enzymes are always greatly increased in cancer cells. Whether metabolic reprogramming is involved in curcumin-mediated inhibition of cancer cell growth is unknown. In this study, cell viability was assayed with MTS analysis; cell cycle was measured with flow cytometry analysis. RT-PCR and western blotting were used to analyse the mRNA and protein expression, respectively. Here we demonstrated that curcumin inhibited cancer cell growth, especially for Ec109 cells. Curcumin induced cell cycle arrest at G2/M phase. Curcumin caused a significant down-regulation of glycolytic enzymes expressions in a dose-dependent manner. Our results further indicated that the AMPK was required for curcumin-mediated down-regulation of glycolytic enzymes. AMPK-mediated down-regulation of glycolytic enzymes blocked Ec109 cell growth. Taken together, our results revealed that the AMPK-mediated metabolic switch plays an important role in esophageal cancer cell growth.

Ras/ERK signaling pathway is involved in curcumin-induced cell cycle arrest and apoptosis in human gastric carcinoma AGS cells

Curcumin, the biologically active compound from the rhizome of Curcuma longa, could inhibit cell growth and induce apoptosis in gastric carcinoma. However, the underlying mechanism of curcumin on gastric carcinoma cells still needs further investigation. In this study, morphological observation indicated that curcumin inhibited the proliferation of AGS cells in a dose-dependent manner. According to the flow cytometric analysis, curcumin treatment resulted in G2/M arrest in AGS cells, accompanied with an increased expression of cyclin B1 and a decreased expression of cyclin D1. In addition, DNA ladders were observed by gel electrophoresis. Meanwhile, the activities of caspase-3, -8, and -9 were also enhanced in curcumin-treated AGS cells. Nevertheless, the increased activities could be inhibited by benzyloxycarbonyl-Val-Ala-Asp (OME)-fluoromethylketone (z-VAD-fmk), which suggested that the apoptosis was caspase-dependent. Furthermore, downregulation of rat sarcoma (Ras) and upregulation of extracellular-signal-regulated kinase (ERK) were also observed in AGS cells treated with curcumin by Western blot. U0126, an ERK inhibitor, blocked curcumin-induced apoptosis. The results suggested that curcumin inhibited the growth of the AGS cells and induced apoptosis through the activation of Ras/ERK signaling pathway and downstream caspase cascade, and curcumin might be a potential target for the treatment of gastric carcinoma.

Mechanism Underlying Curcumin-induced Apoptosis and Cell Cycle Arrest on SCC25 Human Tongue Squamous Cell Carcinoma Cell Line

Mechanism Underlying Curcumin-induced Apoptosis and Cell Cycle Arrest on SCC25 Human Tongue Squamous Cell Carcinoma Cell Line

Anaphase-promoting complex/cyclosome protein Cdc27 is a target for curcumin-induced cell cycle arrest and apoptosis

BackgroundCurcumin (diferuloylmethane), the yellow pigment in the Asian spice turmeric, is a hydrophobic polyphenol from the rhizome of Curcuma longa. Because of its chemopreventive and chemotherapeutic potential with no discernable side effects, it has become one of the major natural agents being developed for cancer therapy. Accumulating evidence suggests that curcumin induces cell death through activation of apoptotic pathways and inhibition of cell growth and proliferation. The mitotic checkpoint, or spindle assembly checkpoint (SAC), is the major cell cycle control mechanism to delay the onset of anaphase during mitosis. One of the key regulators of the SAC is the anaphase promoting complex/cyclosome (APC/C) which ubiquitinates cyclin B and securin and targets them for proteolysis. Because APC/C not only ensures cell cycle arrest upon spindle disruption but also promotes cell death in response to prolonged mitotic arrest, it has become an attractive drug target in cancer therapy.MethodsCell cycle profiles were determined in control and curcumin-treated medulloblastoma and various other cancer cell lines. Pull-down assays were used to confirm curcumin binding. APC/C activity was determined using an in vitro APC activity assay.ResultsWe identified Cdc27/APC3, a component of the APC/C, as a novel molecular target of curcumin and showed that curcumin binds to and crosslinks Cdc27 to affect APC/C function. We further provide evidence that curcumin preferably induces apoptosis in cells expressing phosphorylated Cdc27 usually found in highly proliferating cells.ConclusionsWe report that curcumin directly targets the SAC to induce apoptosis preferably in cells with high levels of phosphorylated Cdc27. Our studies provide a possible molecular mechanism why curcumin induces apoptosis preferentially in cancer cells and suggest that phosphorylation of Cdc27 could be used as a biomarker to predict the therapeutic response of cancer cells to curcumin.

Abstract 2014: Modulation of DNA methyltransferases in leukemia cells by curcumin and its associated anti-leukemia activities

Abstract Purpose: Curcumin, a natural product of curcuma longa and a safe and widely consumed spice, has been shown to exhibit strong in-vitro and in-vivo anti-tumor activity through the inhibition of NF-κB activity, increase of reactive oxygen species (ROS) levels and decrease of the global DNA methylation levels in leukemia cells. We investigated here the molecular mechanisms of down-regulation of DNA Methyltransferases in leukemia cells by curcumin and its associated anti-leukemia activities. Method: Leukemia cell lines MV4-11, Kasumi-1 and K562 cells and primary leukemia cells from patient with AML were treated with 1-30 μM of curcumin and MV4-11 xenografted nu/nu athymic mice was given i.p. curcumin at 100 mg/kg, and the transcription and protein levels of DNMT1, DNMT3a, DNMT3b, Sp1, p15INK4B and p21 were assessed by either RT-PCR or western blot. The inhibition of NF-κB was determined using Electrophoretic Mobility Shift Assays and the disruption of Sp1-NF-κB/DNMTs promoter complex was investigated by anti-body gel supershifts. The hypomethylating activity of curcumin on the promoter of p15INK4B in MV4-11 cells in-vitro was assessed by a LC-MS/MS method for regional DNA methylation. The anti-proliferative activity of curcumin and cell cycle distribution and apoptosis were evaluated using MTS assay and flow cytometry. Results: In addition to the pre-defined direct inhibition of the enzymatic activity of DNA methyltransferase 1 (DNMT1), curcumin disrupts Sp1/NF-κB complex on DNMT1, DNMT3a and DNMT3b promoter thereby decreasing the transactivation activity of these complexes and down-regulating their mRNA and protein expression levels in AML cells in vitro and in vivo. Consistent with these findings, we showed that promoter hypermethylation of silenced TSGs i.e., p15INK4B decreased while their expression was up-regulated. This results in the increase of protein function, as we showed that in association with p15INK4B re-expression, curcumin induced cell cycle arrest in the S-phase and increase in SubG1 cell fraction, thereby resulting in significant anti-leukemia activity. Conclusion: Different from nucleoside analogs (e.g., azanucleosides), curcumin is an effective S-phase independent DNA methylation inhibitor. Further evaluation of curcumin as a single agent and in combination with other epigenetic targeting compounds in human disease is warranted. Supported by NIH-NCI-R21 CA135478 [ZL], NIH-NCI-RO1 CA102031 [GM], and the BioMedical Mass Spectrometry Laboratory [KC & ZL]. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2014. doi:10.1158/1538-7445.AM2011-2014

Curcumin inhibits the proliferation of human hepatocellular carcinoma J5 cells by inducing endoplasmic reticulum stress and mitochondrial dysfunction

Curcumin (diferuloylmethane), which is obtained from turmeric, the rhizome of Curcuma longa (L.), inhibits many human cancer cells. However, the molecular mechanisms responsible for curcumin-induced endoplasmic reticulum stress in human hepatic cellular carcinoma J5 cells, are not yet clearly understood. J5 cells were treated with various concentrations of curcumin for different durations. The cell viability was detected by MTT assay. The protein expressions of caspase-12, ATF6, GADD153, Calnexin, Calreticulin, PDI and Ero1-Lα, which are associated with endoplasmic reticulum stress and the unfolding protein response pathway, were examined by Western blot analysis. The cell cycle was analyzed by flow cytometry. The protein expressions of TCTP, Mcl-1, Bcl-2 and Bax, which are related to mitochondrial dysfunction, were detected by Western blot analysis. We also detected the ATF6 protein location by immunocytochemistry. The results showed that curcumin inhibits the proliferation of J5 cells in a time- and dose-dependent manner. Curcumin induced the unfolding protein response by down-regulating the protein expressions of Calnexin, PDI and Ero1-Lα and up-regulating the Calreticulin expression. Curcumin induces the GADD153 expression by cleaving caspase-12 and ATF6, and then by translocating ATF6 to the nucleus. Curcumin also down-regulates the protein expressions of TCTP, Mcl-1 and Bcl-2, in order to induce mitochondrial dysfunction. Curcumin induced cell cycle arrest at the G2/M phase by decreasing the Cdc2 expression. In conclusion, the present study showed that curcumin inhibits the proliferation of J5 cells by inducing endoplasmic reticulum stress and mitochondrial dysfunction.

Curcumin Inhibits the Growth, Induces Apoptosis and Modulates the Function of Pituitary Folliculostellate Cells

The polyphenol curcumin (diferuloylmethane) is the active componenet of the spice plant Curcuma longa and has been shown to exert multiple actions on mammalian cells. We have studied its effect on folliculostellate (FS) TtT/GF mouse pituitary cells, representative of a multifunctional, endocrine inactive cell type of the anterior pituitary. Proliferation of TtT/GF cells was inhibited by curcumin in a monolayer cell culture and in the colony formation assay in soft agar. Fluorescence-activated cell-sorting (FACS) analysis demonstrated curcumin-induced cell cycle arrest at G₂/M accompanied by inhibition of cyclin D₁ protein expression. Curcumin had a small effect on necrosis of TtT/GF cells, but it mainly stimulated apoptosis as demonstrated by FACS analysis (Annexin V-fluorescein isothiocyannate/7-aminoactinomycin D staining). Curcumin-induced apoptosis involved suppression of Bcl-2, stimulation of cleaved caspase-3 and induction of DNA fragmentation. Functional studies on FS cell-derived compounds showed that curcumin inhibited mRNA synthesis and release of angiogenic vascular endothelial growth factor-A (VEGF-A). Immune-like functions of FS cells were impaired since curcumin downregulated Toll-like receptor 4, reduced nuclear factor-ĸB expression and suppressed bacterial endotoxin-induced interleukin-6 (IL-6) secretion. The inhibitory action of curcumin on VEGF-A and IL-6 production was also found in primary rat pituitary cell cultures, in which FS cells are the only source of these proteins. The observed effects of curcumin on FS cell growth, apoptosis and functions may have therapeutic consequences for the intrapituitary regulation of hormone production and release as well as for pituitary tumor pathogenesis.

Curcumin acts as anti-tumorigenic and hormone-suppressive agent in murine and human pituitary tumour cells in vitro and in vivo

Curcumin (diferuloylmethane) is the active ingredient of the spice plant Curcuma longa and has been shown to act anti-tumorigenic in different types of tumours. Therefore, we have studied its effect in pituitary tumour cell lines and adenomas. Proliferation of lactosomatotroph GH3 and somatotroph MtT/S rat pituitary cells as well as of corticotroph AtT20 mouse pituitary cells was inhibited by curcumin in monolayer cell culture and in colony formation assay in soft agar. Fluorescence-activated cell sorting (FACS) analysis demonstrated curcumin-induced cell cycle arrest at G2/M. Analysis of cell cycle proteins by immunoblotting showed reduction in cyclin D(1), cyclin-dependent kinase 4 and no change in p27(kip). FACS analysis with Annexin V-FITC/7-aminoactinomycin D staining demonstrated curcumin-induced early apoptosis after 3, 6, 12 and 24 h treatment and nearly no necrosis. Induction of DNA fragmentation, reduction of Bcl-2 and enhancement of cleaved caspase-3 further confirmed induction of apoptosis by curcumin. Growth of GH3 tumours in athymic nude mice was suppressed by curcumin in vivo. In endocrine pituitary tumour cell lines, GH, ACTH and prolactin production were inhibited by curcumin. Studies in 25 human pituitary adenoma cell cultures have confirmed the anti-tumorigenic and hormone-suppressive effects of curcumin. Altogether, the results described in this report suggest this natural compound as a good candidate for therapeutic use on pituitary tumours.

Abstract A34: Curcumin downregulates IL-8 in ER negative DCIS breast cancer model: Correlation between HER-2-induced inflammation and tumorigenecity

Abstract A34 Introduction Overexpression of HER-2 oncogene is reported in more than 60% of ductal carcinoma in situ (DCIS) breast cancer, including 30% estrogen receptor negative chemotherapy resistant high-grade tumors with metastatic phenotype. Recent studies show high correlation between MRI characteristics and lower ER score, higher grade, much higher CD68 count (inflammatory marker) and extensive comedo necrosis of DCIS. The inflammatory cytokine IL-8 is found to be overexpressed in most ER- breast cancers and is recently suggested as a marker of tumor invasion and metastasis. Curcumin (CUR) the active component of the spice turmeric, known for its immunomodulatory, antimutagenic and antitumorigenic properties and was found to inhibit cell proliferation and mitogenic signal transduction pathways in ER negative, HER-2 positive DCIS breast cancer model. Material and Methods Normal 184-B5 breast epithelial cells and transformed 184-B5/HER cells in log phase were exposed to 0, 5, 10 and 20 μM CUR for 24 and 48 hours and analyzed for dose response, cell viability, cell cycle distribution, gene expression and HER-2 signal transduction protein markers. Results 184-B5/HER cells exhibit hyper-proliferation, shorter population doubling time, higher saturation density, reduced rate of apoptosis, higher anchorage independent growth and tumorigenecity compared to the non-tumorigenic ER-, PR-, HER2-, EGFR+ and p53+ parental immortalized 184-B5 cells. Cell cycle analysis of 184-B5/HER cells exposed to 20μM CUR showed cytostatic arrest of growth, 85% inhibition of colony formation, decreased G0/G1: S+G2/M ratio and increased apoptosis. Microarray data showed 557 probes to be modulated in 20μM CUR (24 hrs) treated 185-B5/HER cells (117 upregulated, 380 downregulated). These include reduced expression of cell cycle regulatory genes such as cyclin A (-2.79), cyclin B2 (-3.89), cyclin D1 (-1.50), cdk2 (-1.69) and Cdc25c (-3.80). Decreased levels of Cyclin B2, cdk2 and Cdc25c cell cycle proteins in 184-B5/HER cells, reflect CUR induced cell cycle arrest in S and G2/M phases. Treatment with CUR decreased NFkB (-1.86) in 184-B5/HER cells suggesting modulation of downstream signaling pathways including the inflammatory cascade. We observed a 10 fold higher levels of interleukin-8 (IL-8) gene expression in 184-B5/HER cells compared to 184-B5 cells, while treatment with CUR dramatically reduced the IL-8 gene expression as revealed by both microarray and real-time PCR. Conclusion Treatment of breast epithelial 184-B5/HER cells with CUR show preventive efficacy in this ER negative DCIS model via cytostatic arrest in S and G2/M phases of the cell cycle, by downregulation of ERK pathway and induction of apoptosis, verified at both the gene and protein levels. Moreover, CUR down-regulates key regulatory proteins such as NFkB and IL-8 expression thus preventing the inflammatory cascade and possible progression of DCIS into invasive ductal carcinoma. Reduced expression of metastatic molecular marker IL-8 by CUR in 184-B5/HER cells suggests its preventive/therapeutic potential [Support: NIH-NCI CA122394]. Citation Information: Cancer Prev Res 2008;1(7 Suppl):A34.

DNA damage and endoplasmic reticulum stress mediated curcumin-induced cell cycle arrest and apoptosis in human lung carcinoma A-549 cells through the activation caspases cascade- and mitochondrial-dependent pathway

Curcumin, a major component of the Curcuma species, is known to have antioxidant, anti-inflammatory properties and induce apoptosis of cancer cells, however, the precise molecular mechanisms of apoptosis in vitro are unclear. In this study, we showed that curcumin, a plant product containing the phenolic phytochemical, caused DNA damage and endoplasmic reticulum (ER) stress and mitochondrial-dependent-induced apoptosis through the activation of caspase-3 at a treatment concentration of 30μM in human lung cancer A-549 cells. In contrast, treatment with 5–10μM of curcumin did not induce significant apoptosis, but rather induced G2/M-phase arrest in A-549 cells. Flow cytometric analysis indicated that curcumin directly increased intracellular oxidative stress based on the cell permeable dye, 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) acting as an indicator of reactive oxygen species (ROS) generation. GADD153 and GRP78 were increased by curcumin which was indicative of ER stress. Curcumin increased Ca2+ levels and the mitochondrial membrane potential (ΔΨm), was decreased in A-549 cells. Overall, our results demonstrated that curcumin treatment causes cell death by activating pathways inducing G2/M-phase arrest and apoptosis.

Reactive oxygen species and imbalance of calcium homeostasis contributes to curcumin induced programmed cell death in Leishmania donovani

Curcumin, a polyphenol compound, has been recognized as a promising anti-cancer drug. The purpose of the present study was to investigate the cytotoxicity of curcumin to Leishmania donovani, the causative agent for visceral leishmaniasis. Flow cytometric analysis revealed that curcumin induced cell cycle arrest at G2/M phase. Incubation of Leishmania promastigotes with curcumin caused exposure of phosphatidylserine to the outer leaflet of plasma membrane. This event is preceded by curcumin-induced formation of reactive oxygen species (ROS) and elevation of cytosolic calcium through the release of calcium ions from intracellular stores as well as by influx of extracellular calcium. Elevation of cytosolic calcium is responsible for depolarization of mitochondrial membrane potential (DeltaPsim), release of Cytochrome c into the cytosol and concomitant nuclear alterations that included deoxynucleotidyltransferase-mediated dUTP end labeling (TUNEL) and DNA fragmentation. Taken together, these data indicate that curcumin has promising antileishmanial activity that is mediated by programmed cell death and, accordingly, merits further investigation as a therapeutic option for the treatment of leishmaniasis.

Abrogation of U266 Multiple Myeloma Cell Proliferation Via Inhibition of NF-κB Activation by Curcumin

Background: Curcumin is a naturally occurring biologically active compound, and it has been shown to possess potent anti-inflammatory, anti-tumor and anti-oxidative properties. It is known for its anti-pro- liferative and proapoptotic effects in several cancer cells. Curcumin's effects on the mechanisms of cell survival and the expression of various cytokines were investigated in U266 cells and the in vivo effects of curcumin were examined using an animal model. Methods: Cell proliferation assay and flow cytometry were used to examine cell proliferation, along with cell cycle analysis. The protein expressions were analyzed by Western blotting and the expressed levels of cytokines were analyzed by the ELISA method. Results: Curcumin inhibited U266 cell growth in a dose-dependent and time-dependent manner. Cell cycle analysis showed an increased sub-G1 phase, a down regulated cyclinD1 expression and an induced p21 expression. Apoptosis induced a down regulated procaspase 3 expression and it induced cleaved PARP. Curcumin inhibited the IL (interleukin)-6 induced cell signal pathway via decreasing the STAT1 an 3, Erk cyclinD1 and c-myc expressions. Also, administration of 25mg/kg curcumin to a U266 animal model inhibited cancer cell engraftment in the bone marrow and it decreased the IL-6, sIL-6R and IL-8 ex- pression levels. Conclusion: Curcumin induced cell cycle arrest and apoptosis and it inhibited the IL-6 mediated signal transduction pathways in U266 cells. Similar to the in vitro results, curcumin inhibited cancer cell pro- liferation and the expression of cytokine in vivo. (Korean J Hematol 2008;43:19-27.)

Linkage of Curcumin-Induced Cell Cycle Arrest and Apoptosis by Cyclin-Dependent Kinase Inhibitor p21/WAF1/CIP1

We have recently shown that curcumin induces apoptosis in prostate cancer cells through Bax translocation to mitochondria and caspase activation, and enhances the therapeutic potential of TRAIL. However, the molecular mechanisms by which it causes growth arrest are not well-understood. We studied the molecular mechanism of curcumin-induced cell cycle arrest in prostate cancer androgen-sensitive LNCaP and androgen-insensitive PC-3 cells. Treatment of both cell lines with curcumin resulted in cell cycle arrest at G1/S phase and that this cell cycle arrest is followed by the induction of apoptosis. Curcumin induced the expression of cyclin-dependent kinase (CDK) inhibitors p16/INK4a, p21/WAF1/CIP1 and p27/KIP1, and inhibited the expression of cyclin E and cyclin D1, and hyperphosphorylation of retinoblastoma (Rb) protein. Lactacystin, an inhibitor of 26 proteasome, blocks curcumin-induced down-regulation of cyclin D1 and cyclin E proteins, suggesting their regulation at level of posttranslation. The suppression of cyclin D1 and cyclin E by curcumin may inhibit CDK-mediated phosphorylation of pRb protein. The inhibition of p21/WAF1/CIP1 by siRNA blocks curcumin-induced apoptosis, thus establishing a link between cell cycle and apoptosis. These effects of curcumin result in the proliferation arrest and disruption of cell cycle control leading to apoptosis. Our study suggests that curcumin can be developed as a chemopreventive agent for human prostate cancer.

Retracted: Curcumin (diferuloylmethane) inhibits constitutive active NF‐κB, leading to suppression of cell growth of human T‐cell leukemia virus type I‐infected T‐cell lines and primary adult T‐cell leukemia cells

Adult T-cell leukemia (ATL) is a fatal malignancy of T lymphocytes caused by infection with human T-cell leukemia virus type I (HTLV-I) and remains incurable. Curcumin (diferuloylmethane), the major pigment of the spice turmeric, can be potentially effective by promoting cell apoptosis. Here we examined whether curcumin is effective in the treatment of ATL. Curcumin prevented cell growth of HTLV-I-infected T-cell lines and primary ATL cells but not of normal peripheral blood mononuclear cells. Curcumin induced cell cycle arrest by reducing the expression of cyclin D1, Cdk1 and Cdc25C and apoptosis by reducing the expression of XIAP and survivin. Most of these genes are known to be regulated by NF-kappaB, which plays a critical role in oncogenesis by HTLV-I. Curcumin suppressed constitutive active NF-kappaB of HTLV-I-infected T-cell lines and primary ATL cells by inhibiting phosphorylation of IkappaBalpha. Curcumin also inhibited Tax-induced NF-kappaB transcriptional activity. However, curcumin-induced suppression of cell growth did not correlate with Tax expression level. Curcumin inhibited the growth of HTLV-I-infected T-cell tumors implanted subcutaneously in SCID mice. Our results indicate that curcumin has tumor-suppressive activity against ATL.

Apoptosis Induction by Curcumin in Human Myelogenous Leukemia Cell Lines

Background: Curcumin, a naturally occurring biologically active compound extracted from rhizomes of Curcuma species, has been shown to possess potent anti-inflammatory, anti-tumor and anti-oxidative properties. The effects and possible mechanism of this agent were investigated on 2 human myelogenous leukemic cell lines. Methods: K562 and KG-1 cells were the two cell lines selected. The MTT assay and flow cytometry were used to assess the cytotoxicity and for cell cycle analysis, respectively. The protein expressions were analyzed by Western blotting; the caspase activity was also checked. Results: Both cell lines showed dose-dependent susceptibility to curcumin, and the cell cycle analysis showed an increased sub-G1 phase in the KG-1 cells. In the K562 cell, curcumin down regulated the expressions of PCNA (proliferating cell nuclear antigen) and cyclins D1 and B1. The expression of Akt was also down-regulated, but caspase-3 was activated to induce cleaved PARP (polyadenosine ribose polymerase) and apoptosis. However, the expression of phospho-Erk was unaffected. Co-treatment of cyclosporin A (CsA) with curcumin resulted in an attenuation of apoptosis in the K562 cells, implying curcumin-induced apoptosis is dependent on the release of cytochrome c from the mitochondria. Conclusion: Curcumin induced cell cycle arrest and apoptosis in both human myelogenous leukemic cell lines, with the apoptosis appearing to be dependent on the release of cytochrome c from the mitochondria. (Korean J Hematol 2005;40:75-81.)