Curcumin & Quercetin

Curcumin is the main active flavonoid derived from the rhizome of Curcuma longa (Jiang huang), with its dry herb weight consisting of up to 3.08% curcumin (Minami et al., 2009). Curcumin has been used to treat cardiovascular disease, inflammation and arthritis (Goel et al., 2008). Epidemiological studies have found that incidence of several cancers is low in India where curcumin is widely consumed, suggesting that curcumin intake plays a role in cancer prevention (Lopez, 2008). Other studies have also indicated that curcumin inhibits cell proliferation and survival in breast cancer, colon cancer, prostate cancer, gastric cancer, leukemia, lymphoma and melanoma (Goel et al., 2008). Curcumin induces cell apoptosis through complex intrinsic and extrinsic pathways. Curcumin binds to more than 30 different protein targets, including transcript factors (NF-kB and activator protein-1), growth factor receptors [epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2)], kinases [mitogen-activated protein kinase (MAPK), PKC and protein kinase A (PKA)], inflammatory cytokines [tumor necrosis factor (TNF) and interleukins], cell cycle-related proteins (p53 and p21), matrix metalloproteinases (MMPs) and urokinase plasminogen activators (u-PA) (Goel et al., 2008; Bhandarkar & Arbiser, 2007; Ravindran et al., 2009). Daily oral administration of curcumin suppresses metastasis in breast, colon, lung and medulloblastoma cancers.

The suppression involves the regulation of metastatic proteins, such as vascular endothelial growth factor (VEGF), MMP-2, MMP-9 and intercellular adhesion molecules (Aggarwal et al., 2005; Binion et l., 2008). Curcumin induces non-apoptotic cell death, such as autophagic cell death, which involves the degradation of the cell’s own components through lysosomal machinery (Ravindran et al., 2009). In vitro and in vivo studies have demonstrated that curcumin induces autophagic cell death, as evidenced by the immunoreactivity of microtubule-associated protein light chain 3 (LC3) in myeloid leukemia cells. The action mechanism is attributed to the inhibition of the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activation of extracellular signal-regulated kinase 1/2 by curcumin in malignant glioma cells (Shinojima et al., 2007; Aoki et al., 2007). In addition, autophagic inhibitor bafilomycin A1 suppresses curcumin-induced cell death (Jia et al., 2009). Another type of non-apoptotic cell death induced by curcumin is paraptosis, which is observed in malignant breast cancer cells but not in normal breast cells. Curcumin induces paraptotic events (eg. the promotion of vacuolation accompanied with mitochondrial and/orendoplasmic reticular swelling and fusion) and decreases the level of paraptotic inhibitor protein AIP-1/Alix (Yoon et al., 2009). These paraptotic events are attributed to superoxide anion and proteasomal dysfunction (Yoon et al., 2009).

Curcumin reduces toxicity induced by anti-cancer agents (Nautiyal et al., 2011), sensitizes chemo-resistant cancer cells and demonstrates synergic effects with different chemotherapeutic agents such as doxorubicin, 5-FU, paclitaxel, vincristine, melphalan, butyrate, cisplatin, celecoxib, vinorelbine, gemcitabine, oxaliplatin, etoposide, sulfinosine, thalidomide, suberoylanilide hydroxamic acid, dasatinib and bortezomib (Nautiyal et al., 2011). Prior administration of curcumin reduces the DNA damage and oxidative stress induced by cyclophosphamide (CXC) (Ibrahim et al., 2007), improves uroprotective efficacy in the CXC hemorrhagic cystitis model (Arafa, 2009) and suppresses early lung damage in CXC-treated rats (Venkatesan & Chandrakasa, 1995). Curcumin alleviates the side effects of mitomycin C, as evidenced by decreased lipid peroxidation and DNA damage (Siddique et al., 2010). Furthermore, curcumin reduces weight loss and improves kidney function and bone marrow suppression in animal studies (Zhou et al., 2009). When combined with oxaliplatin, curcumin decreases the proliferative capacity of oxaliplatin-resistant cell lines and enhances the cytotoxicity of oxaliplatin in an in vitro oxaliplatin-resistant model (Howells et al., 2010). Additionally, curcumin protects healthy cells against radiation and sensitizes tumor cells to radiation therapy (Goel & Aggarwal, 2010; Yallapu et al., 2010). Clinical trials have been or are currently being conducted to evaluate the tolerance, safety, pharmacokinetics and efficiency of curcumin as well as its combination therapy with current anti-cancer drugs (Hatcher et al., 2008). A phase I clinical trial found no dose-limiting toxicity in patients treated with an oral-dose of up to 8g/day of curcumin. The recommendation is seven consecutive doses (6g/day) of curcumin every three weeks in combination with a standard dose of docetaxel (Bayet-Robert et al., 2009). Improvements in biological and clinical responses were observed in most treated patients (Bayet-Robert et al., 2009). A phase II trial of gemcitabine-resistant pancreatic cancer found chemotherapeutic drugs in combined use with curcumin to be sufficiently safe, feasible and efficient. While the bioavailability of most curcumin except 'Heat Soluble' is relatively poor, two out of 21 patients in the phase II trial using standard curcumin, showed clinical biological responses, with one patient exhibiting marked tumor regression coupled with a significant increase in serum cytokine levels (Kanai et al., 2011; Dhillon et al., 2008)

Curcumin induces cell death and restores tamoxifen sensitivity in the antiestrogen-resistant breast cancer cell lines MCF-7/LCC2 and MCF-7/LCC9.

Jiang M, Huang O, Zhang X, Xie Z, Shen A, Liu H, Geng M, Shen K. Molecules. 2013 Jan 8;18(1):701-20. doi: 10.3390/molecules18010701.

Curcumin, a principal component of turmeric (Curcuma longa), has potential therapeutic activities against breast cancer through multiple signaling pathways. Increasing evidence indicates that curcumin reverses chemo-resistance and sensitizes cancer cells to chemotherapy and targeted therapy in breast cancer. To date, few studies have explored its potential anti-proliferation effects and resistance reversal in antiestrogen-resistant breast cancer. In this study, we therefore investigated the efficacy of curcumin alone and in combination with tamoxifen in the established antiestrogen-resistant breast cancer cell lines MCF-7/LCC2 and MCF-7/LCC9. We discovered that curcumin treatment displayed anti-proliferative and pro-apoptotic activities and induced cell cycle arrest at G2/M phase. Of note, the combination of curcumin and tamoxifen resulted in a synergistic survival inhibition in MCF-7/LCC2 and MCF-7/LCC9 cells. Moreover, we found that curcumin targeted multiple signals involved in growth maintenance and resistance acquisition in endocrine resistant cells. In our cell models, curcumin could suppress expression of pro-growth and anti-apoptosis molecules, induce inactivation of NF-kB, Src and Akt/mTOR pathways and downregulate the key epigenetic modifier EZH2. The above findings suggested that curcumin alone and combinations of curcumin with endocrine therapy may be of therapeutic benefit for endocrine-resistant breast cancer.

Chemo-resistant melanoma sensitized by tamoxifen to low dose curcumin treatment through induction of apoptosis and autophagy.

Chatterjee SJ, Pandey S. Cancer Biol Ther. 2011 Jan 15;11(2):216-28. Epub 2011 Jan 15.

Melanoma is the deadliest form of skin cancer, which is notoriously aggressive and chemo-resistant, and for which there is little effective treatment available if it goes undetected. Curcumin from the turmeric spice (Curcuma longa) has long been used in Southeast Asian medicine to alleviate ailments and cure an array of diseases and disorders. It possesses anti-inflammatory, anti-oxidant and most importantly anti-carcinogenic activity. There have been contradictory reports discussing the efficacy of curcumin-induced death on melanoma. In this report, we show that curcumin does induce apoptosis in A375 and the relatively resistant G361 malignant human melanoma cell lines at higher doses. Tamoxifen is an estrogen receptor (ER) blocker that is used for ER positive breast cancer treatment. Recently, tamoxifen has been shown to directly target the mitochondria. Given that curcumin is a pro oxidant and tamoxifen can act on mitochondria, we ask whether the combinatorial treatment could result in synergistic induction of apoptosis in chemo-resistant melanoma. Our results show a corresponding increase in phosphatidyl serine flipping, mitochondria depolarization and reactive oxygen species (ROS) generation by the combined treatment at lower doses. Interestingly, there was significant induction of autophagy along with apoptosis following the combined treatment. Importantly, non-cancerous cells are unaffected by the combination of these non-toxic compounds. However, once exposed to low doses of this co-treatment, melanoma cells still retain signals to commit suicide even after removal of the drugs. This combination provides a non-toxic option for combinatorial chemotherapy with great potential for future use.

Effect of the o-methyl catechols apocynin, curcumin and vanillin on the cytotoxicity activity of tamoxifen.

Pedroso LS, Fvero GM, de Camargo LE, Mainardes RM, Khalil NM. J Enzyme Inhib Med Chem. 2013 Aug;28(4):734-40. doi: 10.3109/14756366.2012.680064. Epub 2012 Apr 23.

Apocynin (APO), curcumin (CUR) and vanillin (VAN) are o-methyl catechols widely studied due their antioxidant and antitumor properties. The effect of treatment with these o-methyl catechols on tamoxifen (TAM)-induced cytotoxicity in normal and tumor cells was studied. The cytotoxicity of TAM on red blood cells (RBC) was performed by hemoglobin or K(+)release and on polymorphonuclear leukocytes (PMNs) by trypan blue dye exclusion method. Cytotoxic activity was assessed in human chronic myeloid leukemia (K562) cell line by (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). According the release of hemoglobin and K(+), the CUR showed a decrease in TAM cytotoxicity on RBC; however, in PMN, APO, CUR and VAN showed increased of these cells viability. VAN presented the highest cytotoxicity on K562 cells, followed by APO and CUR. These results point the potential therapeutic value of these o-methyl catechols with TAM, particularly of CUR, which potentiates the cytotoxic effects of TAM on K562 cells and also decreases TAM-associated cytotoxicity on RBC and PMN.

Amelioration of tamoxifen-induced liver injury in rats by grape seed extract, black seed extract and curcumin.

El-Beshbishy HA, Mohamadin AM, Nagy AA, Abdel-Naim AB. Indian J Exp Biol. 2010 Mar;48(3):280-8.

Liver injury was induced in female rats using tamoxifen (TAM). Grape seeds (Vitis vinifera) extract (GSE), black seed (Nigella sativa) extract (NSE), curcumin (CUR) or silymarin (SYL) were orally administered to TAM-intoxicated rats. Liver histopathology of TAM-intoxicated: rats showed pathological changes. TAM-intoxication elicited declines in liver antioxidant enzymes levels (glutathione peroxidase, glutathione reductase, superoxide dismutase and catalase), reduced glutathione (GSH) and GSH/GSSG ratio plus the hepatic elevations in lipid peroxides, oxidized glutathione (GSSG), tumor necrosis factor-alpha (TNF-alpha) and serum liver enzymes; alanine transaminase, aspartate transaminase, alkaline phosphatase, lactate dehydrogenase and gamma glutamyl transferase levels. Oral intake of NSE, GSE, CUR or SYL to TAM-intoxicated rats, attenuated histopathological changes and corrected all parameters mentioned above. Improvements were prominent in case of NSE (similarly SYL) > CUR > GSE. Data indicated that NSE, GSE or CUR act as free radical’s scavengers and protect TAM-induced liver injury in rats.

Basal levels and patterns of anticancer drug-induced activation of nuclear factor-kappaB (NF-kappaB), and its attenuation by tamoxifen, dexamethasone, and curcumin in carcinoma cells.

Chuang SE, Yeh PY, Lu YS, Lai GM, Liao CM, Gao M, Cheng AL. Biochem Pharmacol. 2002 May 1;63(9):1709-16.

Nuclear factor-kappaB (NF-kappaB) has been implicated in the development of drug resistance in cancer cells. We systematically examined the baseline levels of NF-kappaB activity of representative carcinoma cell lines, and the change of NF-kappaB activity in response to a challenge with four major anticancer drugs (doxorubicin, 5-fluorouracil, cisplatin, and paclitaxel). We found that the basal level of NF-kappaB activity was heterogeneous and roughly correlated with drug resistance. When challenged with various drugs, all the cell lines examined responded with a transient activation of NF-kappaB, which then declined to basal level despite variation in the concentration of the agent, and the timing of the treatment. In contrast to tumor necrosis factor-alpha (TNF-alpha), which activates NF-kappaB in minutes, NF-kappaB activation induced by anticancer drugs usually occurred more than 1hr after stimulation. A gradual increase of total NF-kappaB and its nuclear translocation, and cytoplasmic translocation of nuclear I kappa B alpha and its degradation were involved in this process. In particular, when cells were pre-treated with common biologic modulators such as tamoxifen, dexamethasone, and curcumin, the doxorubicin-induced NF-kappaB activation was attenuated significantly. This inhibition may play a role in sensitizing cancer cells to chemotherapeutic drugs. This study has demonstrated that activation of NF-kappaB is a general cellular response to anticancer drugs, and the mechanism of activation appears to be distinct from that induced by TNF-alpha. These observations may have implications for improving the efficacy of systemic chemotherapy for cancer patients.

The mTOR Signaling Pathway in Cancer and the Potential mTOR Inhibitory Activities of Natural Phytochemicals

The mammalian target of rapamycin (mTOR) kinase plays an important role in regulating cell growth and cell cycle progression in response to cellular signals. It is a key regulator of cell proliferation and many upstream activators and downstream effectors of mTOR are known to be deregulated in various types of cancers.

Since the mTOR signaling pathway is commonly activated in human cancers, many researchers are actively developing inhibitors that target key components in the pathway and some of these drugs are already on the market. Numerous preclinical investigations have also suggested that some herbs and natural phytochemicals, such as curcumin, resveratrol, timosaponin III, gallic acid, diosgenin, pomegranate, epigallocatechin gallate (EGCC), genistein and 3,3’-diindolylmethane inhibit the mTOR pathway either directly or indirectly. Some of these natural compounds are also in the clinical trial stage.

The mTOR pathway is a key regulator of cell proliferation and several upstream activators and downstream effectors of mTOR are known to be deregulated in some cancers such as renal cell carcinoma, non-small cell lung cancer, breast cancer, sarcomas, colorectal and gastrointestinal tumors (Law, 2005; Tokunaga et al., 2008; Li et al., 2013; Takahashi et al., 2014; Wang and Zhang, 2014). The mTOR signaling is constitutively activated in many tumor types, suggesting that mTOR is an attractive target for cancer drug development and therapy (Yu et al., 2001; Chan, 2004; Shor et al., 2009; Han et al., 2013; Pandurangan, 2013). The mTOR signaling network consists of a number of tumor suppressor genes and proto-oncogenes, thereby explains that aberrant activities of these genes will promote the formation of cancerous cells.

Numerous important anticancer drugs in the market are either obtained from natural sources, by structural modification of natural compounds, or by synthesis of new compounds using natural compound as lead (Cragg et al., 1997; da Rocha et al., 2001). Therefore, sourcing out new drugs and the continuous interest in using natural compounds for cancer therapy is a global effort.

Numerous preclinical investigations have shown that some herbs and natural phytochemicals, such as curcumin, resveratrol, timosaponin III, gallic acid, diosgenin, pomegranate, epigallocatechin gallate (EGCC), genistein, and 3,3’-diindolylmethane inhibit mTOR pathway either directly or indirectly. Some of them are undergoing clinical trials as chemotherapeutic agents, chemopreventive compounds and/or combination therapy to improve the efficacy of the standard chemotherapy. These natural phytochemicals with mTOR inhibitory activities have great potential in cancer prevention. This is in view that higher consumption of fruits and vegetables was associated with lower risk of cancer (Gullett et al., 2010).

Curcumin, a polyphenol natural compound extracted from the plant Curcuma longa L., is commonly used as spice in India and Southeast Asia. It is used as food additive and traditional Indian medicine for the treatment of various diseases such as biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism and sinusitis (Shishodia et al., 2007). Curcumin has shown exceptional chemopreventive and anti-tumor activities in some pre-clinical studies. In HCT116 colorectal cancer cells, curcumin down regulates protein and mRNA expression of mTOR, Raptor and Rictor, suggesting that curcumin exerts its anti-proliferative effects by inhibiting the mTOR signaling pathway and thus may represent a novel class of mTOR inhibitor (Johnson et al., 2009).

In human Rh1 and Rh30 rhabdomyosarcoma cells, DU145 prostate cancer cells, MCF-7 breast cancer cells and Hela cervical cancer cells, curcumin rapidly inhibits the phosphorylation of mTOR and its downstream effector molecules such as p70S6K and 4E-BP1, indicating that curcumin may execute its anticancer activity primarily by blocking mTOR-mediated signaling pathways in these tumor cells (Beevers et al., 2006).

Furthermore, curcumin induces apoptosis, inhibits cell growth and inhibits the basal or type I insulin-like growth factor-induced motility of the Rh1 and Rh30 cells (Beevers et al., 2006). Curcumin is found to dissociate Raptor, at low concentration, and Rictor, at high concentration, from mTOR complex. However, it is unclear if curcumin disrupts the mTOR complex by direct binding to mTOR or to a component of the mTOR complexes (Beevers et al., 2009).

In human PC3 prostate cancer cells, curcumin suppresses murine double minute 2 (MDM2) oncogene expression through the erythroblastosis virus transcription factor 2 (EST2) by modulating PI3K/mTOR/ETS2 signaling pathway (Li et al., 2007a). In both human U87-MG and U373-MG malignant glioma cells, curcumin inhibits the Akt/mTOR/ p70S6K pathway and activates the extracellular signal- regulated kinase (ERK) pathway, resulting in the induction of autophagy.

On the other hand, activation of Akt pathway by recombinant full-length human active Akt1 protein (rAkt1) inhibited curcumin-induced autophagy and decreased curcumin-inhibited phosphorylation of Akt and p70S6K, suggesting that curcumin-induced inactivation of Akt/mTOR/p70S6K pathway plays a role in induction of autophagy (Aoki et al., 2007). As combined treatment, curcumin and dual PI3K/Akt and mTOR inhibitor induce apoptosis through p53-dependent Bcl-2 mRNA down- regulation at the transcriptional level and Mcl-1 protein down-regulation at the post-transcriptional level in human renal carcinoma Caki cells (Seo et al., 2014).

No

Natural compounds

Target

Natural Source

Clinical trial phase

1

Curcumin

Akt and mTOR

Curcuma longa L.

In Phase I-II for pancreatic cancer, colorectal cancer, colon cancer, rectal cancer, advanced cancer. In clinical trial for familial adenomatous polyposis

2

Resveratrol

PI3K, Akt and mTOR

Grapes and red wine

In clinical trial for neuroendocrine tumor

3

Pomegranate

PI3K, Akt and mTOR

Punica granatum L.

In Phase II for prostate cancer

4

Genistein

Akt and mTOR

Glycine max (L.) Merr. and several plants

In Phase I-II for prostate cancer breast cancer, pancreatic cancer, bladder cancer, endometrial cancer

5

3, 3-diindolylmethane

PI3K, Akt and mTOR

Cruciferous vegetables

In Phase II-III for breast cancer and prostate cancer

6

Green tea extract or polyphenon E

Akt and mTOR

Green tea

In Phase I-II for breast cancer, leukemia, monoclonal gammopathy of undetermined significance and/or smoldering multiple myeloma, prostatic hyperplasia, premalignant lesions of the head and neck

7

Epigallocatechin gallate (EGCG)

Akt and mTOR

Green tea

In preclinical study for human hepatoma cells and keloid fibroblast

8

Timosaponin AIII

Akt and mTOR

Anemarrhena asphodeloides Bunge

In pre-clinical study for BT-549 and MDAM231 breast cancer cells

9

Gallic acid

Akt and mTOR

Phaleria macrocarpa (Scheff.) Boerl.

In pre-clinical study for TE-2 esophageal cancer cells

10

Diosgenin

Akt and mTOR

Dioscorea spp.

In pre-clinical study for AU565 breast adenocarcinoma cells

Source: Tan HK, Moad AIH, Tan ML. Asian Pacific Journal of Cancer Prevention, Vol 15, 2014. DOI:http://dx.doi.org/10.7314/APJCP.2014.15.16.6463

Several studies have indicated that curcumin's anti-cancer actions appear to also be enhanced with it is combined with green tea extract (EGCG).

Combination of curcumin and green tea catechins prevents dimethylhydrazine-induced colon carcinogenesis.

Xu G, Ren G, Xu X, Yuan H, Wang Z, Kang L, Yu W, Tian K. Food Chem Toxicol. 2009 Oct 24.

The chemopreventive effects of curcumin and green tea catechins individually and in combination on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis were studied in male Wister rats following 32 weeks of dietary treatment. The incidence, number and size of colorectal cancer were measured. Colorectal aberrant crypt foci (ACF) were analyzed by methylene blue staining. Proliferation indices and apoptotic indices were determined by PCNA immunostaining and TUNEL assay respectively. The results showed that dietary curcumin, catechins and combination administration significantly inhibited the total number of ACF per rat. The combination treatment displayed the most potent inhibitory effect, while there was no difference of inhibition between curcumin and catechins-treated groups. The incidence of colorectal cancer in the treated groups was significantly lower than that of positive control group. Compared with the positive control group, the proliferation index was significantly decreased and the apoptotic index was significantly increased in all treatment groups, while the effect of the combination was the greatest among the treated groups. Our findings suggest that the combination of curcumin and catechins produces a synergistic colon cancer-preventative effect that would be more potent than each of the compounds alone.

Curcumin inhibits prosurvival pathways in chronic lymphocytic leukemia B cells and may overcome their stromal protection in combination with EGCG

Ghosh AK, Kay NE, Secreto CR, Shanafelt TD. Clin Cancer Res. 2009 Feb 15;15(4):1250-8.

The effects of curcumin on the viability of primary CLL B cells and its ability to overcome stromal mediated protection was studies. The in vitro effect of curcumin on primary CLL B cells was evaluated using fluorescence activated cell sorter analysis and Western blotting. For some experiments, CLL B cells were cocultured with human stromal cells to evaluate the effects of curcumin on leukemia cells cultured in their microenvironment. Finally, the effect of curcumin in combination with the green tea extract epigallocatechin-3 gallate (EGCG) was evaluated.

Results: Curcumin induced apoptosis in CLL B cells in a dose-dependent (5-20 micromol/L) manner and inhibited constitutively active prosurvival pathways, including signal transducers and activators of transcription 3 (STAT3), AKT, and nuclear factor kappaB. Moreover, curcumin suppressed expression of the anti-apoptotic proteins Mcl-1 and X-linked inhibitor of apoptosis protein (XIAP), and up-regulated the pro-apoptotic protein BIM. Coculture of CLL B cells with stromal cells resulted in elevated levels of STAT3, increased expression of Mcl-1 and XIAP, and decreased sensitivity to curcumin. When curcumin was administered simultaneously with EGCG, antagonism was observed for most patient samples. In contrast, sequential administration of these agents led to substantial increases in CLL B-cell death and could overcome stromal protection.

Conclusions: Curcumin treatment was able to overcome stromal protection of CLL B cells on in vitro testing and to synergize with EGCG when administered in a sequential fashion.

Curcumin and Green Tea Extract Inhibit Chemo Induced Pulmonary Fibrosis: A Comparison with N-Acetyl Cysteine.

Hamdy MA, El-Maraghy SA, Kortam MA. J Biochem Mol Toxicol. 2012 Nov 6. doi: 10.1002/jbt.21447.

The study was aimed to investigate the protective effect of green tea extract (GTE), curcumin, and N acetyl cysteine (NAC) on experimentally induced pulmonary fibrosis. Curcumin (200 mg/kg b.w), GTE (150 mg/kg b.w), and NAC (490 mg/kg b.w) were administered orally for 14 days with concomitant administration of cyclophosphamide (CP). Lung fibrosis was assessed by measuring hydroxyproline and elastin levels and confirmed by histopathological examination. Oxidative stress was also observed in the CP group. Lung myeloperoxidase activity was significantly decreased in animals of the CP group. N-acetyl-beta-d-glucosaminidase, leukotriene C(4) , and protein were increased in bronchoalveolar lavage fluid (BALF). All modulators markedly attenuated the altered biochemical parameters as compared to CP-treated rats. These results suggest the possibility of using these treatments as protective agents with chemotherapy and as protective agents for lung fibrosis.

The combination of EGCG and curcumin suppresses ER alpha-breast cancer cell growth in vitro and in vivo.

Somers-Edgar TJ, Scandlyn MJ, Stuart EC, Le Nedelec MJ, Valentine SP, Rosengren RJ. Int J Cancer. 2008 May 1;122(9):1966-71.

Both epigallocatechin gallate (EGCG) and curcumin have shown efficacy in various in vivo and in vitro models of cancer. This study was designed to determine the efficacy of these naturally derived polyphenolic compounds in vitro and in vivo, when given in combination. Studies in MDA-MB-231 cells demonstrated that EGCG + curcumin was synergistically cytotoxic and that this correlated with G(2)/M-phase cell cycle arrest. After 12 hr, EGCG (25 microM) + curcumin (3 microM) increased the proportion of cells in G(2)/M-phase to 263 +/- 16% of control and this correlated with a 50 +/- 4% decrease in cell number compared to control. To determine if this in vitro result would translate in vivo, athymic nude female mice were implanted with MDA-MB-231 cells and treated with curcumin (200 mg/kg/day, po), EGCG (25 mg/kg/day, ip), EGCG + curcumin, or vehicle control (5 ml/kg/day, po) for 10 weeks. Tumor volume in the EGCG + curcumin treated mice decreased 49% compared to vehicle control mice (p < 0.05), which correlated with a 78 +/- 6% decrease in levels of VEGFR-1 protein expression in the tumors. Curcumin treatment significantly decreased tumor protein levels of EGFR and Akt, however the expression of these proteins was not further decreased following combination treatment. Therefore, these results demonstrate that the combination of EGCG and curcumin is efficacious in both in vitro and in vivo models of ER alpha-breast cancer and that regulation of VEGFR-1 may play a key role in this effect.

Synergistic anticancer activity of curcumin and catechin: an in vitro study using human cancer cell lines.

Manikandan R, Beulaja M, Arulvasu C, Sellamuthu S, Dinesh D, Prabhu D, Babu G, Vaseeharan B, Prabhu NM. Microsc Res Tech. 2012 Feb;75(2):112-6. doi: 10.1002/jemt.21032. Epub 2011 Jul 21.

The most practical approach to reduce morbidity and mortality of cancer is to delay the process of carcinogenesis by usage of anticancer agents. This necessitates that safer compounds are to be critically examined for anticancer activity especially, those derived from natural sources. A spice commonly found in India and the surrounding regions, is turmeric, derived from the rhizome of Curcuma longa and the major active component is a phytochemical termed curcumin. Green tea is one of the most popular beverages used worldwide, produced from the leaves of evergreen plant Camellia sinensis and the major active ingredients are polyphenolic compounds known as catechins. In this study, synergistic anticancer activity of curcumin and catechin was evaluated in human colon adenocarcinoma HCT 15, HCT 116, and human larynx carcinoma Hep G-2 cell lines. Although, both curcumin or catechin inhibited the growth of above cell lines, interestingly, in combination of both these compounds highest level of growth control was observed. The anticancer activity shown is due to cytotoxicity, nuclear fragmentation as well as condensation, and DNA fragmentation associated with the appearance of apoptosis. These results suggest that curcumin and catechin in combination can inhibit the proliferation of HCT 15, HCT 116, as well as Hep G-2 cells efficiently through induction of apoptosis.

Epigallocatechin-3-gallate potentiates curcumin's ability to suppress uterine leiomyosarcoma cell growth and induce apoptosis.

Kondo A, Takeda T, Li B, Tsuiji K, Kitamura M, Wong TF, Yaegashi N. Int J Clin Oncol. 2012 Feb 15.

Uterine leiomyosarcoma (LMS) has an unfavorable response to standard chemotherapeutic regimens. Two natural occurring compounds, curcumin and epigallocatechin gallate (EGCG), are reported to have anti-cancer activity. We previously reported that curcumin reduced uterine LMS cell proliferation by targeting the AKT-mTOR pathway. However, challenges remain in overcoming curcumin's low bioavailability.

The human LMS cell line SKN was used. The effect of EGCG, curcumin or their combination on cell growth was detected by MTS assay. Their effect on AKT, mTOR, and S6 was detected by Western blotting. The induction of apoptosis was determined by Western blotting using cleaved-PARP specific antibody, caspase-3 activity and TUNEL assay. Intracellular curcumin level was determined by a spectrophotometric method. Antibody against EGCG cell surface receptor, 67-kDa laminin receptor (67LR), was used to investigate the role of the receptor in curcumin's increased potency by EGCG.

In this study, we showed that the combination of EGCG and curcumin significantly reduced SKN cell proliferation more than either drug alone. The combination inhibited AKT, mTOR, and S6 phosphorylation, and induced apoptosis at a much lower curcumin concentration than previously reported. EGCG enhanced the incorporation of curcumin. 67LR antibody partially rescued cell proliferation suppression by the combination treatment, but was not involved in the EGCG-enhanced intracellular incorporation of curcumin. EGCG significantly lowered the concentration of curcumin required to inhibit the AKT-mTOR pathway, reduce cell proliferation and induce apoptosis in uterine LMS cells by enhancing intracellular incorporation of curcumin, but the process was independent of 67LR.

Synergism from sequenced combinations of curcumin and epigallocatechin-3-gallate with cisplatin in the killing of human ovarian cancer cells.

Yunos NM, Beale P, Yu JQ, Huq F. Anticancer Res. 2011 Apr;31(4):1131-40.

Drug resistance remains an on-going challenge in ovarian cancer chemotherapy. The objective of this study was to determine the effect on synergism in activity from the sequenced combinations of cisplatin (Cis) with curcumin (Cur) and epigallocatechin-3-gallate (EGCG) in the human ovarian cancer cell lines. The drugs were added in binary combinations: Cis combined with Cur, and Cis combined with EGCG to the human ovarian A2780 and A2780(cisR) cancer cell lines, using five different sequences of administration: 0/0 h, 4/0 h, 0/4 h, 24/0 h and 0/24 h. The combination index (CI) was used to assess the combined action of the drugs. CIs <1, =1 and >1 indicated synergism, additiveness and antagonism respectively. Cellular accumulation of platinum and platinum-DNA binding levels from Cis and its combination with the phytochemicals were determined using graphite furnace atomic absorption spectrometry. Addition of Cis 4 h before Cur and EGCG (0/4 h combination) produced the most synergistic outcomes in both the A2780 and A2780(cisR) cell lines. The cellular accumulations of platinum and platinum-DNA binding resulting from the 0/4 h combinations were greater as compared to the values using Cis alone, thus providing an explanation for the synergistic action. When sequenced combinations of Cis with Cur and with EGCG are applied to human ovarian A2780 and A2780(cisR) cancer cell lines, lower concentrations and shorter time gap between the two additions seem to produce a higher cytotoxic effect.

Curcumin Suppresses Lipopolysaccharide-Induced Cyclooxygenase-2 Expression by Inhibiting Activator Protein 1 and Nuclear Factor ?B Bindings in BV2 Microglial Cells.

Kang G, Kong P-J, uh Y-J, Lim S-Y, et al. Journal of Pharmacological Sciences. Vol. 94 (2004) , No. 3 Pp.325-8

Inflammation is a significant component of chronic neurodegenerative diseases. Cyclooxygenase-2 (COX-2) is expressed in activated microglial cells and appears to be an important source of prostaglandins during inflammatory conditions. To investigate the effect of curcumin on COX-2 gene expression in microglial cells, we treated lipopolysaccharide (LPS)-challenged BV2 microglial cells with various concentrations of curcumin. Curcumin significantly inhibited LPS-mediated induction of COX-2 expression in both mRNA and protein levels in a concentration-dependent manner. COX-2 enzyme activity was also inhibited in accordance with mRNA and protein levels. Furthermore, curcumin markedly inhibited LPS-induced nuclear factor ?B (NF-?B) and activator protein 1 (AP-1) DNA bindings. These data suggest that curcumin suppresses LPS-induced COX-2 gene expression by inhibiting NF-?B and AP-1 DNA bindings in BV2 microglial cells.

Dietary Curcumin Significantly Improves Obesity-Associated Inflammation and Diabetes in Mouse Models of Diabesity.

Weisberg SP, Leibel R & Tortoriello DV. Endocrinology July 1, 2008 vol. 149 no. 7 Pp.3549-58. doi: 10.1210/en.2008-0262

Obesity is a major risk factor for the development of type 2 diabetes, and both conditions are now recognized to possess significant inflammatory components underlying their pathophysiology’s. We tested the hypothesis that the plant polyphenolic compound curcumin, which is known to exert potent anti-inflammatory and antioxidant effects, would ameliorate diabetes and inflammation in murine models of insulin-resistant obesity. We found that dietary curcumin admixture ameliorated diabetes in high-fat diet-induced obese and leptin-deficient ob/ob male C57BL/6J mice as determined by glucose and insulin tolerance testing and hemoglobin A1c percentages. Curcumin treatment also significantly reduced macrophage infiltration of white adipose tissue, increased adipose tissue adiponectin production, and decreased hepatic nuclear factor-?B activity, hepatomegaly, and markers of hepatic inflammation. We therefore conclude that orally ingested curcumin reverses many of the inflammatory and metabolic derangements associated with obesity and improves glycemic control in mouse models of type 2 diabetes. This or related compounds warrant further investigation as novel adjunctive therapies for type 2 diabetes in man.

Quercetin transiently increases energy expenditure but persistently decreases circulating markers of inflammation in C57BL/6J mice fed a high-fat diet

Stewart LK, Soileau JL, Ribnicky D, Zhong Q. Wang Zq, et al. Metabolism - Clinical and Experimental. Volume 57, Supplement 1 , Pages S39-S46, July 2008

Quercetin has anti-inflammatory properties and has been postulated to enhance energy expenditure (EE), and was effective in reducing circulating markers of inflammation in animals on a high fat diet

The Antiproliferative Effect of Quercetin in Cancer Cells is mediated via Inhibition of the PI3K-Akt/PKB Pathway

Gullati N, Laudet B, Zohrabian VM, et al. Anticancer Research March-April 2006 vol. 26 no. 2A Pp. 1177-81

Background: The tumor suppressor gene PTEN, mutated in 40-50% of patients with brain tumors, especially those with glioblastomas, maps to chromosome 10q23.3 and encodes a dual-specificity phosphatase. PTEN exerts its effects partly via inhibition of protein tyrosine kinase B (Akt/Protein Kinase B), which is involved in the phosphatidylinositol (PtdIns) 3-kinase (PI3K)-mediated cell-survival pathway. The naturally occurring bioflavonoid Quercetin (Qu) shares structural homology with the commercially available selective PI3K inhibitor, LY 294002 (LY). Here, the effects of Qu on the Akt/PKB pathway were evaluated. Materials and Methods: The human breast carcinoma cell lines, HCC1937, with homozygous deletion of the PTEN gene, and T47D, with intact PTEN, were time-treated with Qu or LY and analyzed for activated levels of Akt by measuring phospho-Akt (p-Akt) levels using immunoblotting analysis. To detect p-Akt, the T47D cells were treated with EGF prior to treatment with or without Qu or LY. Cell proliferation after 24-h treatment with Qu or LY was quantified by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Results: Treatment with Qu (25 ?M) for 0.5, 1 and 3 h completely suppressed constitutively activated Akt/PKB phosphorylation at Ser-473 in HCC1937 cells. Pre-exposing T47D cells to Qu (25 ?M) or LY (10 ?M) abrogated EGF-induced Akt/PKB phosphorylation at Ser-473. Both Qu (100 ?M) and LY (50 ?M) treatments for 24 h significantly decreased cell proliferation, as shown by the MTT assay. Conclusion: Pharmacologically safe doses of the naturally occurring bioflavonoid Qu inhibit the PI3K-Akt/PKB pathway, in a manner similar to that of the commercially available LY. Overall, our results indicated that Qu inhibited the constitutively activated-Akt/PKB pathway in PTEN-null cancer cells, and suggest that this compound may have therapeutic benefit against tumorigenesis and cancer progression.

Induction of cell cycle arrest and apoptosis in human breast cancer cells by quercetin

Choi J-A, Kim J-Y, Lee J-Y, et al. International journal of oncology. 2001, vol. 19, no4, Pp. 837-44

Quercetin, a widely distributed bioflavonoid, has been shown to induce growth inhibition in certain cancer cell types. In the present study, we have pursued the mechanism of growth inhibition in MCF-7 human breast cancer cells. Quercetin treatment resulted in the accumulation of cells specifically at G2/M phase of the cell cycle. Mitotic index measured by MPM2 staining clearly showed that cells were transiently accumulated in M phase, 24 h after treatment. The transient M phase accumulation was accompanied by a transient increase in the levels of cyclin B 1 and Cdc2 kinase activity. However, 24 h or longer treatment caused a marked accumulation of cells in G2 instead of M phase. Levels of cyclin Bl and cyclin B1-associated Cdc2 kinase activity were also decreased. We also found that quercetin markedly increased Cdk-inhibitor p21CIP1/WAF1 protein level after treatment for 48 h or longer, and the induction of p21CIP1/WAF1 increased its association with Cdc2-cyclin B1 complex, however, up-regulation of p53 by quercetin was not observed. Quercetin also induced significant apoptosis in MCF-7 cells in addition to cell cycle arrest, and the induction of apoptosis was markedly blocked by antisense p21CIP1/WAF1 expression. The present data, therefore, demonstrate that a flavonoid quercetin induces growth inhibition in the human breast carcinoma cell line MCF-7 through at least two different mechanisms; by inhibiting cell cycle progression through transient M phase accumulation and subsequent G2 arrest, and by inducing apoptosis.

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