Curcumin induces a p53-dependent apoptosis in human basal cell carcinoma cells

Curcumin induces Apaf-1-dependent, p21-mediated caspase activation and apoptosis

Previous studies have demonstrated that curcumin induces mitochondria-mediated apoptosis. However, understanding of the molecular mechanisms underlying curcumin-induced cell death remains limited. In this study, we demonstrate that curcumin treatment of cancer cells caused dose- and time-dependent caspase-3 activation, which is required for apoptosis as confirmed using the pan caspase inhibitor, z-VAD. Knockdown experiments and knockout cells excluded a role of caspase-8 in curcumin-induced caspase-3 activation. In contrast, Apaf-1 deficiency or silencing inhibited the activity of caspase-3, pointing to a requisite role of Apaf-1 in curcumin-induced apoptotic cell death. Curcumin treatment led to Apaf-1 upregulation both at the protein and mRNA levels. Cytochrome c release from mitochondria to the cytosol in curcumin-treated cells was associated with upregulation of proapoptotic proteins such as Bax, Bak, Bid, and Bim. Crosslinking experiments demonstrated Bax oligomerization during curcumin-induced apoptosis, suggesting that induced expression of Bax, Bid, and Bim causes Bax-channel formation on the mitochondrial membrane. The release of cytochrome c was unaltered in p53-deficient cells, whereas absence of p21 blocked cytochrome c release, caspase activation, and apoptosis. Importantly, p21-deficiency resulted in reduced expression of Apaf-1 during curcumin treatment, indicating a requirement of p21 in Apaf-1 dependent caspase activation and apoptosis. Together, our findings demonstrate that Apaf-1, Bax, and p21 as novel potential targets for curcumin or curcumin-based anticancer agents.

2-deoxy-D-glucose combined with ferulic acid enhances radiation response in non-small cell lung carcinoma cells

The present study was undertaken to investigate the radiosensitizing effects of 2-deoxy-D-glucose (2DG), a glycolytic inhibitor, and ferulic acid (FA), a phenolic prooxidant, in relatively radioresistant human non-small cell lung carcinoma cells (NCI-H460). NCI-H460 cells were treated with 4 mM 2DG and/or 53.8 µM FA for 24 h and then exposed to 2 Gy irradiation. Compared to cells that were 2 Gy-irradiated alone (50%), FA and 2DG with radiation (FA+2DG+IR) showed additional decrease in cell viability (15%). This has been further validated by decreased (86%) colony formation in 2DG+FA+IR group compared to 2DG (29%), FA (24%) and IR (37%) group alone. Increased apoptotic cells (84%) in 2DG+FA+IR group further confirm the radiosensitizing property of 2DG or FA. In NCI-H460 cells 2DG decreased NADPH levels (10%) and FA increased ROS levels leading to enhanced oxidative damage in the 2DG+FA+IR group. This was reflected as altered mitochondrial membrane potential, increased lipid peroxidative markers (TBARS), DNA damage and decreased intracellular glutathione (GSH) levels in combined treatment groups when compared to radiation or 2DG or FA treatment alone. The present study suggests that FA and 2DG act by increasing oxidative damage in NCI-H460 cells.

Binding of isoxazole and pyrazole derivatives of curcumin with the activator binding domain of novel protein kinase C

The protein kinase C (PKC) family of serine/threonine kinases is an attractive drug target because of its involvement in the regulation of various cellular functions, including cell growth, differentiation, metabolism, and apoptosis. The endogenous PKC activator diacylglycerol contains two long carbon chains, which are attached to the glycerol moiety via ester linkage. Natural product curcumin (1), the active constituent of Curcuma L., contains two carbonyl and two hydroxyl groups. It modulates PKC activity and binds to the activator binding site (Majhi et al., Bioorg. Med. Chem.2010, 18, 1591). To investigate the role of the carbonyl and hydroxyl groups of curcumin in PKC binding and to develop curcumin derivatives as effective PKC modulators, we synthesized several isoxazole and pyrazole derivatives of curcumin (2-6), characterized their absorption and fluorescence properties, and studied their interaction with the activator-binding second cysteine-rich C1B subdomain of PKCδ, PKCε and PKCθ. The EC(50)s of the curcumin derivatives for protein fluorescence quenching varied in the range of 3-25 μM. All the derivatives showed higher binding with the PKCθC1B compared with PKCδC1B and PKCεC1B. Fluorescence emission maxima of 2-5 were blue shifted in the presence of the C1B domains, confirming their binding to the protein. Molecular docking revealed that hydroxyl, carbonyl and pyrazole ring of curcumin (1), pyrazole (2), and isoxazole (4) derivatives form hydrogen bonds with the protein residues. The present result shows that isoxazole and pyrazole derivatives bind to the activator binding site of novel PKCs and both carbonyl and hydroxy groups of curcumin play roles in the binding process, depending on the nature of curcumin derivative and the PKC isotype used.

A Lipo-PEG-PEI complex for encapsulating curcumin that enhances its antitumor effects on curcumin-sensitive and curcumin-resistance cells

A cationic liposome-PEG-PEI complex (LPPC) was used as a carrier for the encapsulation of hydrophobic curcumin to give curcumin/LPPC. Curcumin/LPPC had an average size less than 270 nm and a zeta potential of approximately 40 mV. The LPPC encapsulation efficiency for curcumin was about 45%. The authors found it surprising that the cytotoxic activity of the curcumin/LPPC was fivefold higher than curcumin when tested on curcumin-sensitive cells and 20-fold more active against curcumin-resistant cells. Curcumin/LPPC treatment caused a cell cycle arrest at G2/M phase, which rapidly resulted in apoptosis. The increased cytotoxic activity of curcumin/LPPC is likely attributable to its rapid accumulation in the cell. In vivo, administration of curcumin/LPPC inhibited about 60 - 90% of tumor growth in mice bearing CT-26 or B16F10 cells. These results demonstrate LPPC encapsulation technology is able to enhance the effects of antitumor drugs. Use of this technology may provide a new tool for cancer therapy, especially for drug-resistant cancer. From the Clinical Editor: This team of investigators used a cationic liposome-PEG-PEI complex (LPPC) to encapsulate curcumin. The different delivery method resulted in the five-fold increase of cytotoxic activity against curcumin-sensitive cells and twenty-fold against curcumin-resistant cells.

Redox modulation of p53: mechanisms and functional significance

The tumor suppressor protein p53 functions as a stress-responsive transcription factor. In response to oxidative, nitrosative, and electrophilic insults, p53 undergoes post-translational modifications, such as oxidation and covalent modification of cysteines, nitration of tyrosines, acetylation of lysines, phosphorylation of serine/threonine residues, etc. Because p53 plays a vital role in the transcriptional regulation of genes encoding proteins involved in a wide spectrum of biochemical processes including DNA repair, cell-cycle regulation, and programmed cell death, the redox-modification of p53 appears to be an important determinant of cell fate. This review highlights the redox regulation of p53 and its consequences on cellular function.

The targets of curcumin

Curcumin (diferuloylmethane), an orange-yellow component of turmeric or curry powder, is a polyphenol natural product isolated from the rhizome of the plant Curcuma longa. For centuries, curcumin has been used in some medicinal preparation or used as a food-coloring agent. In recent years, extensive in vitro and in vivo studies suggested curcumin has anticancer, antiviral, antiarthritic, anti-amyloid, antioxidant, and anti-inflammatory properties. The underlying mechanisms of these effects are diverse and appear to involve the regulation of various molecular targets, including transcription factors (such as nuclear factor-kB), growth factors (such as vascular endothelial cell growth factor), inflammatory cytokines (such as tumor necrosis factor, interleukin 1 and interleukin 6), protein kinases (such as mammalian target of rapamycin, mitogen-activated protein kinases, and Akt) and other enzymes (such as cyclooxygenase 2 and 5 lipoxygenase). Thus, due to its efficacy and regulation of multiple targets, as well as its safety for human use, curcumin has received considerable interest as a potential therapeutic agent for the prevention and/or treatment of various malignant diseases, arthritis, allergies, Alzheimer's disease, and other inflammatory illnesses. This review summarizes various in vitro and in vivo pharmacological aspects of curcumin as well as the underlying action mechanisms. The recently identified molecular targets and signaling pathways modulated by curcumin are also discussed here.

Relation between expression pattern of p53 and survivin in cutaneous basal cell carcinomas

BACKGROUND

The tumor suppressor gene p53 is a key regulator of cell division and/or apoptosis. Survivin is a multifunctional member of the inhibitor of apoptosis family. Survivin and p53 represent diametrically opposed signals that influence the apoptotic pathway.

MATERIAL/METHODS

To determine the role of p53 and survivin in basal cell carcinoma (BCC), we evaluated the expression pattern of both proteins with regard to the percentage of positively immunostained tumor cells, the intensity of staining, and subcellular localization among 31 subjects with BCC.

RESULTS

Overexpression of p53 protein was found in 28 of 31 cases (90.3%), whereas survivin accumulation was seen in 27 (87.1%). For p53, moderate and/or strong immunoreactivity was seen in 20 of 28 cases (71.4%), and 26 of 28 cases (92.9%) showed more than 25% reactive tumor cells. Nuclear p53 staining was detected in 23 of 28 cases (82.1%), whereas combined nuclear and cytoplasmic localization was found in only 5 of 28 cases (17.9%). Survivin revealed mild intensity of immunoreaction in 22 of 27 cases (71%), and 25 of 27 cases (92.6%) showed less than 25% labeled tumor cells. Combined nuclear and cytoplasmic survivin localization was present in 26 of 27 cases (96.3%). Statistically significant differences were detected in the assessed expression parameters between those proteins.

CONCLUSIONS

Our results suggest that overexpression of wild type p53 protein may suppress the expression of survivin and its antiapoptotic activity in BCC cells.

RNA binding protein CUGBP2/CELF2 mediates curcumin-induced mitotic catastrophe of pancreatic cancer cells

BACKGROUND

Curcumin inhibits the growth of pancreatic cancer tumor xenografts in nude mice; however, the mechanism of action is not well understood. It is becoming increasingly clear that RNA binding proteins regulate posttranscriptional gene expression and play a critical role in RNA stability and translation. Here, we have determined that curcumin modulates the expression of RNA binding protein CUGBP2 to inhibit pancreatic cancer growth.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we show that curcumin treated tumor xenografts have a significant reduction in tumor volume and angiogenesis. Curcumin inhibited the proliferation, while inducing G2-M arrest and apoptosis resulting in mitotic catastrophe of various pancreatic cancer cells. This was further confirmed by increased phosphorylation of checkpoint kinase 2 (Chk2) protein coupled with higher levels of nuclear cyclin B1 and Cdc-2. Curcumin increased the expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) mRNA, but protein levels were lower. Furthermore, curcumin increased the expression of RNA binding proteins CUGBP2/CELF2 and TIA-1. CUGBP2 binding to COX-2 and VEGF mRNA was also enhanced, thereby increasing mRNA stability, the half-life changing from 30 min to 8 h. On the other hand, silencer-mediated knockdown of CUGBP2 partially restored the expression of COX-2 and VEGF even with curcumin treatment. COX-2 and VEGF mRNA levels were reduced to control levels, while proteins levels were higher.

CONCLUSION/SIGNIFICANCE

Curcumin inhibits pancreatic tumor growth through mitotic catastrophe by increasing the expression of RNA binding protein CUGBP2, thereby inhibiting the translation of COX-2 and VEGF mRNA. These data suggest that translation inhibition is a novel mechanism of action for curcumin during the therapeutic intervention of pancreatic cancers.

Novel investigational drugs for basal cell carcinoma

IMPORTANCE OF THE FIELD

In the United States, the annual incidence of basal cell carcinoma (BCC) is close to 1 million. Ultraviolet radiation exposure is the main risk factor; however, the availability of ever more potent sunscreens and education have not prevented the rise in BCC incidence. Therefore, concerted effects to identify novel preventive and therapeutic strategies are necessary.

AREAS COVERED IN THIS REVIEW

This article summarizes our current understanding of the etiology and molecular mechanisms of BCC tumorigenesis and discusses the preclinical and clinical studies to identify agents with anti-BCC efficacy.

WHAT THE READER WILL GAIN

The discovery that hyperactive Hh pathway signaling causes several cancers, including BCC, has spawned the development of many pharmacologic inhibitors of Hh signaling. Early clinical testing of the most advanced, GDC-0449, demonstrated impressive efficacy in patients with advanced BCC. Other promising anti-BCC chemopreventive strategies include drugs that are already FDA-approved for treating other diseases.

TAKE HOME MESSAGE

Preclinical and clinical trials with pre-existing FDA-approved drugs suggest novel uses for BCC chemoprevention and treatment. Also, new chemical entities that inhibit the Hh pathway show promise, and in combination with other drugs may provide a nonsurgical cure for this most common cancer.

Immunomodulatory and therapeutic activity of curcumin

Inflammation is a disease of vigorous uncontrolled activated immune responses. Overwhelming reports have suggested that the modulation of immune responses by curcumin plays a dominant role in the treatment of inflammation and metabolic diseases. Observations from both in-vitro and in-vivo studies have provided strong evidence towards the therapeutic potential of curcumin. These studies have also identified a plethora of biological targets and intricate mechanisms of action that characterize curcumin as a potent 'drug' for numerous ailments. During inflammation the functional influence of lymphocytes and the related cross-talk can be modulated by curcumin to achieve the desired immune status against diseases. This review describes the regulation of immune responses by curcumin and effectiveness of curcumin in treatment of diseases of diverse nature.

Curcumin suppresses constitutive activation of STAT-3 by up-regulating protein inhibitor of activated STAT-3 (PIAS-3) in ovarian and endometrial cancer cells

Signal transducer and activator of transcription-3 (STAT-3) is constitutively activated in ovarian and endometrial cancers and is implicated in uncontrolled cell growth. Thus, its disruption could be an effective approach to control tumorigenesis. Curcumin is a dihydroxyphenolic compound, with proven anti-cancer efficacy in various cancer models. We examined the anti-tumor mechanism of curcumin on STAT-3 and on the negative regulators of STAT-3, including suppressors of cytokine signaling proteins (SOCS-1 and SOCS-3), protein inhibitors of activated STAT (PIAS-1 and PIAS-3), and SH2 domain-containing phosphatases (SHP-1 and SHP-2) in ovarian and endometrial cancer cell lines. Treatment of cancer cells with curcumin induced a dose- and time-dependent decrease of constitutive IL-6 expression and of constitutive and IL-6-induced STAT-3 phosphorylation, which is associated with decreased cell viability and increased cleavage of caspase-3. The inhibition of STAT-3 activation by curcumin was reversible, and phosphorylated STAT-3 levels returned to control levels 24 h after curcumin removal. Compared to normal cells baseline expression of SOCS-3 was high in cancer cells and a marked decrease in SOCS-3 expression was seen following curcumin treatment. Overexpression of SOCS-3 in curcumin-treated cells increased expression of phosphorylated STAT-3 and resulted in increased cell viability. Normal ovarian and endometrial cells exhibited high expression of PIAS-3 protein, whereas in cancer cells the expression was greatly reduced. Curcumin increased PIAS-3 expression in cancer cells. Of significance, siRNA-mediated knockdown of PIAS-3 overcomes the inhibitory effect of curcumin on STAT-3 phosphorylation and cell viability. In conclusion, curcumin suppresses JAK-STAT signaling via activation of PIAS-3, thus attenuating STAT-3 phosphorylation and tumor cell growth.

Hazardous effects of curcumin on mouse embryonic development through a mitochondria-dependent apoptotic signaling pathway

In this study, we examined the cytotoxic effects of curcumin, the yellow pigment of Curcuma longa, on the blastocyst stage of mouse embryos, subsequent embryonic attachment, and outgrowth in vitro and in vivo implantation by embryo transfer. Mouse blastocysts were incubated in medium with or without curcumin (6, 12 or 24 μM) for 24 h. Cell proliferation and growth were investigated using dual differential staining, apoptosis was analyzed with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), and implantation and post-implantation development of embryos were measured by in vitro development analysis and in vivo embryo transfer, respectively. Blastocysts treated with 24 μM curcumin displayed significantly increased apoptosis and decreased total cell number. Interestingly, we observed no marked differences in the implantation success rates between curcumin-pretreated and control blastocysts during in vitro embryonic development through implantation with a fibronectin-coated culture dish. However, in vitro treatment with 24 μM curcumin was associated with decreased implantation rate and increased resorption of postimplantation embryos in mouse uterus, as well as decreased fetal weight in the embryo transfer assay. Our results collectively indicate that in vitro exposure to curcumin triggers apoptosis and retards early postimplantation development after transfer to host mice. In addition, curcumin induces apoptotic injury effects on mouse blastocysts through ROS generation, and further promotes mitochondria-dependent apoptotic signaling processes to impair sequent embryonic development.

[Markers expression of cell proliferation and apoptosis in basal cell carcinoma]

BACKGROUND

- Basal cell carcinoma is the most common form of human cancer. Studies employing molecular and genetic biology techniques, associated with histomorphology, lead to the identification of risk factors in the development of more recurring and aggressive lesions. OBJECTIVE - To correlate markers expression of apoptosis (p53 and bcl-2) and cell proliferation (Ki-67 and PCNA) with histological indicators of tumor severity. METHODS - Five samples of the nodular, morpheaform and superficial types of carcinoma were studied, respectively.One control group with three lesion-free patients was also included in the study. The Mann-Whitney test was used to compare these markers expression with the manifestation form of basal cell carcinoma. RESULTS - Bcl-2 expression was significant in basal cell carcinomas said to be aggressive (morpheaform and nodular types). Of the studied tumors, 66.7% (n =10) strongly expressed p53.Our results show a greater expression of Ki-67 in nodular and superficial basal cell carcinoma, with no expression in the controls. PCNA showed a strong expression in all types of tumors and in the controls. CONCLUSION - The findings allow us to conclude that Bcl-2 and p53 show a tendency to indicate the severity of basal cell carcinoma. In contrast, Ki-67, due to its variable behavior, cannot be considered a marker of severity. Also, PCNA was not a good marker of cell proliferation.

Allyl sulfides inhibit cell growth of skin cancer cells through induction of DNA damage mediated G2/M arrest and apoptosis

Diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), extracted from crushed garlic by steam-distillation, have been reported to provide the anticancer activity in several cancer types. However, their mechanisms of effects on skin cancer cells remain unclear. Therefore, we used human melanoma A375 cells and basal cell carcinoma cells as the models to elucidate the effects of these three allyl sulfides. Basal cell carcinoma (BCC) is known to be the most prevalent type of skin cancer, and melanoma is the most lethal form. We found that DATS revealed better growth inhibition of A375 and BCC cells than DADS and DAS did. We further demonstrated that DATS increased intracellular reactive oxygen species (ROS) generation, induced cytosolic Ca(2+) mobilization, and decreased mitochondrial membrane potential (DeltaPsim). Western blot results showed the concordance for the expression of molecules involved in G(2)/M arrest and apoptosis observed by cell cycle and cell viability analysis. Moreover, we detected the activation of p53 pathway in response to the oxidative DNA damage. DATS also displayed selective target of growth inhibition between skin cancer cells and normal keratinocyte HaCaT cells. Taken together, these results suggest that DATS is a potential anticancer compound for skin cancer.

Curcumin causes superoxide anion production and p53-independent apoptosis in human colon cancer cells

Curcumin from the rhizome of theCurcuma longa plant has chemopreventative activity and inhibits the growth of neoplastic cells. Since p53 has been suggested to be important for anticancer activity by curcumin, we investigated curcumin-induced cytotoxicity in cultures of p53(+/+) and p53(-/-) HCT-116 colon cancer cells, as well as mutant p53 HT-29 colon cancer cells. Curcumin killed wild-type p53 HCT-116 cells and mutant p53 HT-29 cells in a dose- and time-dependent manner. In addition, curcumin-treated p53(+/+) HCT-116 cells and mutant p53 HT-29 cells showed upregulation of total and activated p53, as well as increased expression of p53-regulated p21, PUMA (p53 upregulated modulator of apoptosis), and Bax; however, an equivalent cytotoxic effect by curcumin was observed in p53(+/+) and p53(-/-) HCT-116 cells, demonstrating that curcumin-induced cytotoxicity was independent of p53 status. Similar results were obtained when the cytotoxic effect of curcumin was assessed in wild-type p53 HCT-116 cells after siRNA-mediated p53 knockdown. Chromatin condensation, poly (ADP-ribose) polymerase-1 cleavage and reduced pro-caspase-3 levels in curcumin-treated p53(+/+) and p53(-/-) HCT-116 cells suggested that curcumin caused apoptosis. In addition, exposure to curcumin resulted in superoxide anion production and phosphorylation of oxidative stress proteins in p53(+/+) and p53(-/-) HCT-116 cells. Collectively, our results indicate that, despite p53 upregulation and activation, curcumin-induced apoptosis in colon cancer cells was independent of p53 status and involved oxidative stress. Curcumin may therefore have therapeutic potential in the management of colon cancer, especially in tumorsthatare resistant to conventional chemotherapydue todefects inp53 expression or function.

Growth suppression of mouse pituitary corticotroph tumor AtT20 cells by curcumin: a model for treating Cushing's disease

BACKGROUND

Pituitary corticotroph tumors secrete excess adrenocorticotrophic hormone (ACTH) resulting in Cushing's disease (CD). Standard treatment includes surgery and, if not successful, radiotherapy, both of which have undesirable side effects and frequent recurrence of the tumor. Pharmacotherapy using PPARgamma agonists, dopamine receptor agonists, retinoic acid or somatostatin analogs is still experimental. Curcumin, a commonly used food additive in South Asian cooking, has potent growth inhibitory effects on cell proliferation. Our laboratory recently demonstrated that curcumin inhibited growth and induced apoptosis in prolactin- and growth hormone-producing tumor cells. Subsequently, Schaaf et.al. confirmed our findings and also showed the in vivo effectiveness of curcumin to suppress pituitary tumorigenesis. However the molecular mechanism that mediate this effect of curcumin are still unknown.

PRINCIPAL FINDINGS

Using the mouse corticotroph tumor cells, AtT20 cells, we report that curcumin had a robust, irreversible inhibitory effect on cell proliferation and clonogenic property. The curcumin-induced growth inhibition was accompanied by decreased NFkappaB activity. Further, curcumin down-regulated the pro-survival protein Bcl-xL, depolarized the mitochondrial membrane, increased PARP cleavage, which led to apoptotic cell death. Finally, curcumin had a concentration-dependent suppressive effect on ACTH secretion from AtT20 cells.

CONCLUSION

The ability of curcumin to inhibit NFkappaB and induce apoptosis in pituitary corticotroph tumor cells leads us to propose developing it as a novel therapeutic agent for the treatment of CD.

Binding of curcumin and its long chain derivatives to the activator binding domain of novel protein kinase C

Protein kinase C (PKC) is a family of serine/threonine kinases that play a central role in cellular signal transduction. The second messenger diacylglycerol having two long carbon chains acts as the endogenous ligand for the PKCs. Polyphenol curcumin, the active constituent of Curcuma longa is an anti-cancer agent and modulates PKC activity. To develop curcumin derivatives as effective PKC activators, we synthesized several long chain derivatives of curcumin, characterized their absorption and fluorescence properties and studied their interaction with the activator binding second cysteine-rich C1B subdomain of PKCdelta, PKCepsilon and PKCtheta. Curcumin (1) and its C16 long chain analog (4) quenched the intrinsic fluorescence of PKCdeltaC1B, PKCepsilonC1B and PKCthetaC1B in a manner similar to that of PKC activator 12-O-tetradecanoylphorbol 13-acetate (TPA). The EC(50)s of the curcumin derivatives for fluorescence quenching varied in the range of 4-11 microM, whereas, EC(50)s for TPA varied in the range of 3-6 microM. Fluorescence emission maxima of 1 and 4 were blue shifted and the fluorescence anisotropy values were increased in the presence of the C1B domains in a manner similar to that shown by the fluorescent analog of TPA, sapintoxin-D, confirming that they were bound to the proteins. Molecular docking of 1 and 4 with novel PKC C1B revealed that both the molecules form hydrogen bonds with the protein residues. The present result shows that curcumin and its long chain derivatives bind to the C1B subdomain of novel PKCs and can be further modified structurally to improve its binding and activity.

Mechanisms for the activity of heterocyclic cyclohexanone curcumin derivatives in estrogen receptor negative human breast cancer cell lines

Estrogen receptor (ER)-negative breast cancer is an aggressive form that currently requires more drug treatment options. Thus, we have further modified cyclohexanone derivatives of curcumin and examined them for cytotoxicity towards ER-negative human breast cancer cells. Two of the analogs screened elicited increased cytotoxic potency compared to curcumin and other previously studied derivatives. Specifically, 2,6-bis(pyridin-3-ylmethylene)-cyclohexanone (RL90) and 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) elicited EC(50) values of 1.54 and 1.10 µM, respectively, in MDA-MB-231 cells and EC(50) values of 0.51 and 0.23 in SKBr3 cells. All other new compounds examined were less potent than curcumin, which elicited EC(50) values of 7.6 and 2.4 µM in MDA-MB-231 and SKBr3 cells, respectively. Mechanistic analyses demonstrated that RL90 and RL91 significantly induced G(2)/M-phase cell cycle arrest and apoptosis. RL90 and RL91 also modulated the expression of key cell signaling proteins, specifically, in SKBr3 cells, protein levels of Her-2, Akt, and NFκB were decreased in a time-dependent manner, while activity of stress kinases JNK1/2 and P38 MAPK were increased. Signaling events in MDA-MB-231 cells were differently implicated, as EGFR protein levels were decreased and activity of GSK-3β transiently decreased, while β-catenin protein level and activity of P38 MAPK, Akt, and JNK1/2 were transiently increased. In conclusion replacement of the phenyl group of cyclohexanone derived curcumin derivatives with heterocyclic rings forms a class of second-generation analogs that are more potent than both curcumin and other derivatives. These new derivatives provide a platform for the further development of drugs for the treatment of ER-negative breast cancer.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.

Curcumin derivatives: molecular basis of their anti-cancer activity

Curcumin, a phenolic compound from the plant Curcuma longa L., has shown a wide-spectrum of chemopreventive, antioxidant and antitumor properties. Although its promising chemotherapeutic activity, preclinical and clinical studies highlight Curcumin limited therapeutic application due to its instability in physiological conditions. To improve its stability and activity, many derivatives have been synthesized and studied, among which bis-DemethoxyCurcumin (bDMC) and diAcetylCurcumin (DAC). In this report, we show that both bDMC and DAC are more stable than Curcumin in physiological medium. To explore the mechanism of their chemotherapeutic effect, we studied their role in proliferation in the HCT116 human colon cancer cells. We correlated kinetic stability and cellular uptake data to their biological effects. Both bDMC and DAC impair correct spindles formation and induce a p53- and p21(CIP1/WAF1)-independent mitotic arrest, which is more stable and long-lasting for bDMC. A subsequent p53/p21(CIP1/WAF1)-dependent inhibition of G1 to S transition is triggered by Curcumin and DAC as a consequence of the mitotic slippage, preventing post-mitotic cells from re-entering the cell cycle. Conversely, the G1/S arrest induced by bDMC is a direct effect of the drug and concomitant to the mitotic block. Finally, we demonstrate that bDMC induces rapid DNA double-strand breaks, moving for its possible development in anti-cancer clinical applications.

Differential solubility of curcuminoids in serum and albumin solutions: implications for analytical and therapeutic applications

Background

Commercially available curcumin preparations contain a mixture of related polyphenols, collectively referred to as curcuminoids. These encompass the primary component curcumin along with its co-purified derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids have numerous biological activities, including inhibition of cancer related cell proliferation and reduction of amyloid plaque formation associated with Alzheimer disease. Unfortunately, the solubility of curcuminoids in aqueous solutions is exceedingly low. This restricts their systemic availability in orally administered formulations and limits their therapeutic potential.

Results

Methods are described that achieve high concentrations of soluble curcuminoids in serum. Solid curcuminoids were either mixed directly with serum, or they were predissolved in dimethyl sulfoxide and added as aliquots to serum. Both methods resulted in high levels of curcuminoid-solubility in mammalian sera from different species. However, adding aliquots of dimethyl sulfoxide-dissolved curcuminoids to serum proved to be more efficient, producing soluble curcuminoid concentrations of at least 3 mM in human serum. The methods also resulted in the differential solubility of individual curcuminoids in serum. The addition of dimethyl sulfoxide-dissolved curcuminoids to serum preferentially solubilized curcumin, whereas adding solid curcuminoids predominantly solubilized bisdemethoxycurcumin. Either method of solubilization was equally effective in inhibiting dose-dependent HeLa cell proliferation in culture. The maximum concentration of curcuminoids achieved in serum was at least 100-fold higher than that required for inhibiting cell proliferation in culture and 1000-fold higher than the concentration that has been reported to prevent amyloid plaque formation associated with Alzheimer disease. Curcuminoids were also highly soluble in solutions of purified albumin, a major component of serum.

Conclusion

These results suggest the possibility of alternative therapeutic approaches by injection or infusion of relatively small amounts of curcuminoid-enriched serum. They also provide tools to reproducibly solubilize curcuminoids for analysis in cell culture applications. The differential solubility of curcuminoids achieved by different methods of solubilization offers convenient alternatives to assess the diverse biological effects contributed by curcumin and its derivatives.

Anticancer and carcinogenic properties of curcumin: considerations for its clinical development as a cancer chemopreventive and chemotherapeutic agent

A growing body of research suggests that curcumin, the major active constituent of the dietary spice turmeric, has potential for the prevention and therapy of cancer. Preclinical data have shown that curcumin can both inhibit the formation of tumors in animal models of carcinogenesis and act on a variety of molecular targets involved in cancer development. In vitro studies have demonstrated that curcumin is an efficient inducer of apoptosis and some degree of selectivity for cancer cells has been observed. Clinical trials have revealed that curcumin is well tolerated and may produce antitumor effects in people with precancerous lesions or who are at a high risk for developing cancer. This seems to indicate that curcumin is a pharmacologically safe agent that may be used in cancer chemoprevention and therapy. Both in vitro and in vivo studies have shown, however, that curcumin may produce toxic and carcinogenic effects under specific conditions. Curcumin may also alter the effectiveness of radiotherapy and chemotherapy. This review article analyzes the in vitro and in vivo cancer-related activities of curcumin and discusses that they are linked to its known antioxidant and pro-oxidant properties. Several considerations that may help develop curcumin as an anticancer agent are also discussed.

Anti cancer effects of curcumin: cycle of life and death

Increasing knowledge on the cell cycle deregulations in cancers has promoted the introduction of phytochemicals, which can either modulate signaling pathways leading to cell cycle regulation or directly alter cell cycle regulatory molecules, in cancer therapy. Most human malignancies are driven by chromosomal translocations or other genetic alterations that directly affect the function of critical cell cycle proteins such as cyclins as well as tumor suppressors, e.g., p53. In this respect, cell cycle regulation and its modulation by curcumin are gaining widespread attention in recent years. Extensive research has addressed the chemotherapeutic potential of curcumin (diferuloylmethane), a relatively non-toxic plant derived polyphenol. The mechanisms implicated are diverse and appear to involve a combination of cell signaling pathways at multiple levels. In the present review we discuss how alterations in the cell cycle control contribute to the malignant transformation and provide an overview of how curcumin targets cell cycle regulatory molecules to assert anti-proliferative and/or apoptotic effects in cancer cells. The purpose of the current article is to present an appraisal of the current level of knowledge regarding the potential of curcumin as an agent for the chemoprevention of cancer via an understanding of its mechanism of action at the level of cell cycle regulation. Taken together, this review seeks to summarize the unique properties of curcumin that may be exploited for successful clinical cancer prevention.

Nitric oxide as a target of complementary and alternative medicines to prevent and treat inflammation and cancer

Nitric oxide (NO) and associated reactive nitrogen species (RNS) are involved in many physiological functions. There has been an ongoing debate to whether RNS can inhibit or perpetuate chronic inflammation and associated carcinogenesis. Although the final outcome depends on the genetic make-up of its target, the surrounding microenvironment, the activity and localization of nitric oxide synthase (NOS) isoforms, and overall levels of NO/RNS, evidence is accumulating that in general, RNS drive inflammation and cancers associated with inflammation. To this end, many complementary and alternative medicines (CAMs) that work in chemoprevention associated with chronic inflammation, are inhibitors of excessive NO observed in inflammatory conditions. Here, we review recent literature outlining a role of NO/RNS in chronic inflammation and cancer, and point toward NO as one of several targets for the success of CAMs in treating chronic inflammation and cancer associated with this inflammation.

Modulation of anti-apoptotic and survival pathways by curcumin as a strategy to induce apoptosis in cancer cells

Apoptosis is a highly regulated mechanism by which cells undergo cell death in an active way. As one of the most challenging tasks concerning cancer is to induce apoptosis in malignant cells, researchers increasingly focus on natural products to modulate apoptotic signaling pathways. Curcumin, a natural compound isolated from the plant Curcuma longa, has chemopreventive properties, which are mainly due to its ability to arrest cell cycle and to induce apoptosis. This article reviews the main effects of curcumin on the different apoptotic signaling pathways involved in curcumin-induced apoptosis of cancer cells, including the intrinsic and extrinsic apoptosis pathways, the NF-kappaB-mediated pathway as well as the PI3K/Akt signaling pathway. This review also focuses on the sensitization of cells to TRAIL-induced apoptosis after curcumin treatment and shows that curcumin enhances the capacity to induce cell death of different chemotherapeutical drugs.

Curcumin (diferuloylmethane) inhibits cell proliferation, induces apoptosis, and decreases hormone levels and secretion in pituitary tumor cells

Prolactinomas are the most prevalent functional pituitary adenomas. Dopamine D2 receptor (D2R) agonists, such as bromocriptine are the first line of therapy; however, drug intolerance/resistance to D2R agonists exists. Apart from D2R agonists, there is no established medical therapy for prolactinomas; therefore, identifying novel therapeutics is warranted. Curcumin, a commonly used food additive in South Asian cooking, inhibits proliferation of several tumor cell lines; however, its effect on pituitary tumor cell proliferation has not been determined. Our objectives were to: 1) determine whether curcumin inhibits proliferation of pituitary tumor cell lines; 2) identify the signaling intermediaries that mediate the effect of curcumin; 3) examine whether curcumin inhibited pituitary hormone production and release; and 4) examine whether curcumin could enhance the growth-inhibitory effect of bromocriptine. Using rat lactotroph cell lines, GH3 and MMQ cells, we report that curcumin had a robust dose and time-dependent inhibitory effect on GH3 and MMQ cell proliferation. Inhibitory effects of curcumin persisted, even on removal of curcumin, and curcumin also blocked colony formation ability of pituitary tumor cells. The growth-inhibitory effect of curcumin was accompanied by decreased expression of cyclin D3 and ser 780 phosphorylation of retinoblastoma protein. In addition, curcumin also induced apoptosis in both GH3 and MMQ cells. Furthermore, curcumin suppresses intracellular levels and release of both prolactin and GH. Finally, we show that low concentrations of curcumin enhanced the growth-inhibitory effect of bromocriptine on MMQ cell proliferation. Taken together we demonstrate that curcumin inhibits pituitary tumor cell proliferation, induces apoptosis, and decreases hormone production and release, and thus, we propose developing curcumin as a novel therapeutic tool in the management of prolactinomas.

The nonsteroidal anti-inflammatory drug NS398 reactivates SPARC expression via promoter demethylation to attenuate invasiveness of lung cancer cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to exhibit potent anticancer effects in vitro and in vivo. One of the mechanisms by which NSAIDs suppress tumorigenesis is inhibition of angiogenesis and metastasis. In this study, we used a microarray system to study the change of expression profile of metastasis-related genes regulated by NS398, a NSAID and a cyclooxygenase-2 (COX-2) inhibitor. We found that several negative regulators of cell invasion, including secreted protein acidic and rich in cysteine (SPARC), thrombospondin 1 (TSP-1), thrombospondin 3 (TSP-3), and tissue inhibitors of matrix metalloproteinase-2 (TIMP-2) are upregulated by NS398. In addition, we demonstrated that upregulation of SPARC expression by NS398 in human lung cancer cells is mediated by promoter demethylation and associated with a decrease in DNA methyltransferase (DNMT) expression. This is the first report to show that NS398 can inhibit the expression of DNMT1 and 3b. Functional assay indicated that SPARC is a critical mediator for NS398 to inhibit cell invasion. Our results provide new insights for the understanding of the anticancer actions of NSAIDs.

Curcumin: from ancient medicine to current clinical trials

Curcumin is the active ingredient in the traditional herbal remedy and dietary spice turmeric (Curcuma longa). Curcumin has a surprisingly wide range of beneficial properties, including anti-inflammatory, antioxidant, chemopreventive and chemotherapeutic activity. The pleiotropic activities of curcumin derive from its complex chemistry as well as its ability to influence multiple signaling pathways, including survival pathways such as those regulated by NF-kappaB, Akt, and growth factors; cytoprotective pathways dependent on Nrf2; and metastatic and angiogenic pathways. Curcumin is a free radical scavenger and hydrogen donor, and exhibits both pro- and antioxidant activity. It also binds metals, particularly iron and copper, and can function as an iron chelator. Curcumin is remarkably non-toxic and exhibits limited bioavailability. Curcumin exhibits great promise as a therapeutic agent, and is currently in human clinical trials for a variety of conditions, including multiple myeloma, pancreatic cancer, myelodysplastic syndromes, colon cancer, psoriasis and Alzheimer's disease.

Diphenyl difluoroketone: a curcumin derivative with potent in vivo anticancer activity

Diphenyl difluoroketone (EF24), a molecule having structural similarity to curcumin, was reported to inhibit proliferation of a variety of cancer cells in vitro. However, the efficacy and in vivo mechanism of action of EF24 in gastrointestinal cancer cells have not been investigated. Here, we assessed the in vivo therapeutic effects of EF24 on colon cancer cells. Using hexosaminidase assay, we determined that EF24 inhibits proliferation of HCT-116 and HT-29 colon and AGS gastric adenocarcinoma cells but not of mouse embryo fibroblasts. Furthermore, the cancer cells showed increased levels of activated caspase-3 and increased Bax to Bcl-2 and Bax to Bcl-xL ratios, suggesting that the cells were undergoing apoptosis. At the same time, cell cycle analysis showed that there was an increased number of cells in the G(2)-M phase. To determine the effects of EF24 in vivo, HCT-116 colon cancer xenografts were established in nude mice and EF24 was given i.p. EF24 significantly suppressed the growth of colon cancer tumor xenografts. Immunostaining for CD31 showed that there was a lower number of microvessels in the EF24-treated animals coupled with decreased cyclooxygenase-2, interleukin-8, and vascular endothelial growth factor mRNA and protein expression. Western blot analyses also showed decreased AKT and extracellular signal-regulated kinase activation in the tumors. Taken together, these data suggest that the novel curcumin-related compound EF24 is a potent antitumor agent that induces caspase-mediated apoptosis during mitosis and has significant therapeutic potential for gastrointestinal cancers.

Curcumin induces apoptosis in HCT-116 human colon cancer cells in a p21-independent manner

Several micronutrients present in fruits and vegetables exhibit anticancer activity as a result of their actions on molecular targets involved in carcinogenesis and tumor progression. Curcumin, a phenolic phytochemical derived from the rhizome of Curcuma longa, exhibits both cancer-preventative activity and growth inhibitory effects on neoplastic cells. Several studies report that curcumin inhibits cancer cell proliferation and induces apoptosis in cancer cells through p21-mediated cell cycle arrest. Cancer cells that are deficient in p21 are also reported to be more prone to undergo apoptosis in response to a variety of cytotoxic agents. In this study, we determined whether curcumin-induced cytotoxicity in cultures of HCT-116 human colon cancer cells was dependent on p21 status. Curcumin killed wild-type HCT-116 cells in a dose- and time-dependent manner, as measured in an MTT cell viability assay. Moreover, an equivalent cytotoxic effect by curcumin was observed in both p21(+/+) and p21(-/-)HCT-116 cells, indicating that curcumin-induced cytotoxicity was p21-independent. Primary cultures of human dermal fibroblasts were less sensitive than HCT-116 colon cancer cells to lower doses of curcumin, suggesting a degree of selectivity for neoplastic cells. Western blot analysis showed that cell death in curcumin-treated cultures of p21(+/+) and p21(-/-) HCT-116 cells was associated with a reduction in pro-caspase-3 and PARP-1 cleavage, which are indicative of apoptosis. We conclude that curcumin-induced apoptosis in HCT-116 colon cancer cells does not depend on p21 status.

Antitumor, anti-invasion, and antimetastatic effects of curcumin

Curcumin was found to be cytotoxic in nature to a wide variety of tumor cell lines of different tissue origin. The action of curcumin is dependent on with the cell type, the concentration of curcumin (IC50: 2-40 microg/mL), and the time of the treatment. The major mechanism by which curcumin induces cytotoxicity is the induction of apoptosis. Curcumin decreased the expression of antiapoptotic members of the Bcl-2 family and elevated the expression of p53, Bax, procaspases 3, 8, and 9. Curcumin prevents the entry of nuclear factor KB (NF-KB) into the nucleus there by decreasing the expression of cell cycle regulatory proteins and survival factors such as Bcl-2 and survivin. Curcumin arrested the cell cycle by preventing the expression of cyclin D1, cdk-1 and cdc-25. Curcumin inhibited the growth of transplantable tumors in different animal models and increased the life span of tumor-harboring animals. Curcumin inhibits metastasis of tumor cells as shown in in vitro as well as in vivo models, and the possible mechanism is the inhibition of matrix metalloproteases. Curcumin was found to suppress the expression of cyclooxygenase-2, vascular endothelial growth factor, and intercellular adhesion molecule- and elevated the expression of antimetastatic proteins, the tissue inhibitor of metalloproteases-2, nonmetastatic gene 23, and Ecadherin. These results indicate that curcumin acts at various stages of tumor cell progression.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

The potentiation of curcumin on insulin-like growth factor-1 action in MCF-7 human breast carcinoma cells

Curcumin has anticarcinogenic and chemopreventive properties in a variety of experimental cancer models. Our in vitro studies have shown that curcumin inhibits cell growth and induces apoptosis in MCF-7, a human breast carcinoma cell line. The insulin-like growth factor-1 (IGF-1) system, including IGFs (IGF-1 and IGF-2), IGF-1R (IGF-1 receptor) and IGFBPs (IGF binding proteins), has been implicated to play a critical role in the development of breast cancer. The aim of the present study was to investigate whether the growth inhibitory effects of curcumin were related to changes of the IGF-1 system in MCF-7 cells. IGF-1 at 50 microg/l in serum-free medium produced maximum proliferation and minimized apoptosis. However, curcumin exhibited a potent ability to blunt IGF-1-stimulated MCF-7 cell growth and reverse the IGF-1-induced apoptosis resistance. To determine whether curcumin intervenes in IGF-1 or IGFBP-3 secretion, MCF-7 cells were incubated in serum-free medium in the presence of various concentrations of curcumin for indicated time periods. Curcumin decreased the secretion of IGF-1 with a concomitant increase of IGFBP-3 in a dose-dependent manner. Receptor tyrosine kinase assays revealed that IGF-1-stimulated IGF-1R tyrosine kinase activation was also abrogated by curcumin in a dose-dependent manner. Real-time fluorescence quantitative reverse transcriptase-polymerase chain reaction (RFQ-RT-PCR) further revealed that curcumin suppressed IGF-1R gene expression at transcriptional level. In conclusion, the inhibition of cell growth and induction of apoptosis by curcumin in MCF-7 cells might be mediated, at least partially, by its ability to down-regulate the IGF-1 axis.

Curcumin induced suicidal erythrocyte death

The natural nutrient component Curcumin with anti-inflammatory and antitumor activity has previously been shown to stimulate apoptosis of several nucleated cell types. The present study has been performed to explore whether Curcumin could similarly induce suicidal death of erythrocytes or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the erythrocyte surface. Phosphatidylserine exposing cells are phagocytosed and thus rapidly cleared from circulating blood. Erythrocyte membrane scrambling may be triggered by increase of cytosolic Ca(2+) activity or formation of ceramide. To test for eryptosis, erythrocyte phosphatidylserine exposure has been estimated from annexin V binding, and erythrocyte volume from forward scatter in FACS analysis. Exposure of erythrocytes to Curcumin (= 1 microM) increased annexin V binding and decreased forward scatter, pointing to phosphatidylserine exposure at the cell surface and cell shrinkage. According to Fluo3 fluorescence Curcumin increased cytosolic Ca(2+) activity and according to immunofluorescence Curcumin increased ceramide formation. As shown previously, hypertonic shock (addition of 550mM sucrose), chloride removal and glucose depletion decreased the forward scatter and increased annexin V binding. The effects on annexin binding were enhanced in the presence of Curcumin. Exposure to Curcumin did, however, not significantly enhance the shrinking effect of hypertonic shock or Cl(-) removal and reversed the shrinking effect of glucose withdrawal. The present observations disclose a proeryptotic effect of Curcumin which may affect the life span of circulating erythrocytes.

c-Abl kinase regulates curcumin-induced cell death through activation of c-Jun N-terminal kinase

Curcumin, a natural phenolic compound found in turmeric (Curcuma longa) exhibits anticancer properties, attributed to its antiproliferative and apoptosis-inducing activity. The ubiquitously expressed nonreceptor tyrosine kinase c-Abl regulates stress responses induced by oxidative agents such as ionizing radiation and H2O2. In this study, we show that c-Abl is an important component of the cell death response activated by curcumin and that Abl mediates this response partly through activation of c-Jun N-terminal kinase (JNK). Therefore, inhibition of Abl by STI571 [imatinib (Gleevec)] treatment or down-regulation of Abl expression through Abl-specific short-hairpin RNA (shRNA) diminished cell death induction and JNK activation. Highlighting the interdependent nature of the Abl and JNK signaling in the curcumin-induced cell death response, a JNK inhibitor [anthra(1,9-cd)pyrazol-6(2H)-one-1,9-pyrazoloanthrone (SP600125)] caused very little cell death inhibition in STI571-pretreated cells and in Abl shRNA-expressing cells. Moreover, treatment with Abl and JNK inhibitor alone or together caused similar levels of cell death inhibition. Although p53 induction in response to curcumin treatment is dependent on Abl, we found that Abl-->p53 signaling is not necessary for curcumin-induced cell death. Taken together, the results demonstrate the differential roles played by Abl-->p53 and Abl-->JNK signaling events in modulating the cell death response to curcumin.

Dietary antioxidant curcumin inhibits microtubule assembly through tubulin binding

Curcumin, a component of turmeric, has potent antitumor activity against several tumor types. However, its molecular target and mechanism of antiproliferative activity are not clear. Here, we identified curcumin as a novel antimicrotubule agent. We have examined the effects of curcumin on cellular microtubules and on reconstituted microtubules in vitro. Curcumin inhibited HeLa and MCF-7 cell proliferation in a concentration-dependent manner with IC(50) of 13.8 +/- 0.7 microm and 12 +/- 0.6 microm, respectively. At higher inhibitory concentrations (> 10 microm), curcumin induced significant depolymerization of interphase microtubules and mitotic spindle microtubules of HeLa and MCF-7 cells. However, at low inhibitory concentrations there were minimal effects on cellular microtubules. It disrupted microtubule assembly in vitro, reduced GTPase activity, and induced tubulin aggregation. Curcumin bound to tubulin at a single site with a dissociation constant of 2.4 +/- 0.4 microm and the binding of curcumin to tubulin induced conformational changes in tubulin. Colchicine and podophyllotoxin partly inhibited the binding of curcumin to tubulin, while vinblastine had no effect on the curcumin-tubulin interactions. The data together suggested that curcumin may inhibit cancer cells proliferation by perturbing microtubule assembly dynamics and may be used to develop efficacious curcumin analogues for cancer chemotherapy.

Protective effects of curcumin on methylglyoxal-induced oxidative DNA damage and cell injury in human mononuclear cells

AIM

To examine the effect of curcumin on oxidative DNA damage and cell apoptosis and injury caused by the reaction of methylglyoxal(MG) with amino acids.

METHODS

We used DNA strand breaks to examine the effect of curcumin on oxidative DNA damage. In addition, reactive oxygen species(ROS) formation occurs in MG-treated mononuclear cells, so the effect of curcumin on ROS generation was measured using 2',7'-dichlorofluorescin diacetate(DCF-DA) as the detection reagent. Moreover, the impact effects of curcumin on MG-induced cell apoptosis and ROS injury were analyzed by TUNEL and ELISA assay. The collagen I attachment ability of mononuclear cells was examined by trypan blue staining.

RESULTS

Our results revealed that curcumin prevented MG/lysine-induced oxidative stress and DNA damage. Curcumin also inhibited MG-induced apoptosis and generation of ROS in mononuclear cells. MG-treated mononuclear cells displayed a lower degree of attachment to collagen (the major component of the vessel wall subendo-thelium), whereas cells pretreated with curcumin before MG treatment exhibited restored affinities for collagen.

CONCLUSION

These results demonstrated that oxidative stress plays a role in MG-induced cell injury and alterations in attachment ability, and that curcumin blocks these effects by virtue of its antioxidant properties.

Curcumin inhibits the mammalian target of rapamycin-mediated signaling pathways in cancer cells

Curcumin (diferuloylmethane), a polyphenol natural product of the plant Curcuma longa, is undergoing early clinical trials as a novel anticancer agent. However, the anticancer mechanism of curcumin remains to be elucidated. Here we show that curcumin inhibited growth of rhabdomyosarcoma cells (Rh1 and Rh30) (IC50 = 2-5 microM) and arrested cells in G1 phase of the cell cycle. Curcumin also induced apoptosis and inhibited the basal or type I insulin-like growth factor-induced motility of the cells. At physiological concentrations (2.5 microM), curcumin rapidly inhibited phosphorylation of the mammalian target of rapamycin (mTOR) and its downstream effector molecules, p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1), in a panel of cell lines (Rh1, Rh30, DU145, MCF-7 and Hela). Curcumin also inhibited phosphorylation of Akt in the cells, but only at high concentrations (>40 microM). The data suggest that curcumin may execute its anticancer activity primarily by blocking mTOR-mediated signaling pathways in the tumor cells.

Chemoprevention of nonmelanoma skin cancer

Skin cancer is the most common cancer in human beings. The increased incidence of skin cancer has brought much attention to the process by which these tumors develop and how they can be prevented. Efforts have been made to educate the public about the importance of protecting skin from excessive ultraviolet light. Despite this work, the incidence of skin cancer continues to increase. Available compounds may be useful in the chemoprevention of skin cancer. Chemoprevention is defined as oral or topical use of dietary or pharmacologic agents to inhibit or reverse the development of cancer. Potential agents included are the retinoids; difluoromethylornithine; T4 endonuclease V; polyphenolic antioxidants, such as (-)-epigallocatechin gallate, found in green tea and grape seed extract; silymarin; isoflavone genestein; nonsteroidal anti-inflammatory drugs; curcumin; lycopene; vitamin E; beta-carotene; and selenium. Many of these agents are available over the counter as topical or oral preparations.

LEARNING OBJECTIVE

At the conclusion of this activity, participants should be familiar with the chemopreventive agents and their efficacy, as well as any significant side effects associated with them.

Modulation of nuclear factor E2-related factor 2-mediated gene expression in mice liver and small intestine by cancer chemopreventive agent curcumin

Curcumin has been shown to prevent and inhibit carcinogen-induced tumorigenesis in different organs of rodent carcinogenesis models. Our objective is to study global gene expression profiles elicited by curcumin in mouse liver and small intestine as well as to identify curcumin-regulated nuclear factor E2-related factor 2 (Nrf2)-dependent genes. Wild-type C57BL/6J and Nrf2 knockout C57BL/6J/Nrf2(-/-) mice were given a single oral dose of curcumin at 1,000 mg/kg. Liver and small intestine were collected at 3 and 12 hours after treatments. Total RNA was extracted and analyzed using Affymetrix (Santa Clara, CA) mouse genome 430 array (45K) and GeneSpring 6.1 software (Silicon Genetics, Redwood City, CA). Genes that were induced or suppressed >2-fold by curcumin treatments compared with vehicle in wild-type mice but not in knockout mice were filtered using GeneSpring software and regarded as Nrf2-dependent genes. Among those well-defined genes, 822 (664 induced and 158 suppressed) and 222 (154 induced and 68 suppressed) were curcumin-regulated Nrf2-dependent genes identified in the liver and small intestine, respectively. Based on their biological functions, these genes can be classified into the category of ubiquitination and proteolysis, electron transport, detoxification, transport, apoptosis and cell cycle control, cell adhesion, kinase and phosphatase, and transcription factor. Many phase II detoxification/antioxidant enzyme genes, which are regulated by Nrf2, are among the identified genes. The identification of curcumin-regulated Nrf2-dependent genes not only provides potential novel insights into the biological effects of curcumin on global gene expression and chemoprevention but also points to the potential role of Nrf2 in these processes.

Dosage effects of curcumin on cell death types in a human osteoblast cell line

Curcumin, the yellow pigment of Curcuma longa, is known to have antioxidant and anti-inflammatory properties, as well as their ability to either induce or prevent cell apoptosis. However, the precise molecular mechanisms of these effects are unknown. Here, we demonstrate that curcumin can induce apoptotic changes, including JNK activation, caspase-3 activation, and cleavage of PARP and PAK2, at treatment concentrations lower than 25 microM in human osteoblast cells. In contrast, treatment with 50-200 microM of curcumin does not induce apoptosis, but rather triggers necrotic cell death in human osteoblasts. Using the cell permeable dye 2',7'-dichlorofluorescin diacetate (DCF-DA) as an indicator of reactive oxygen species (ROS) generation, we found that while treatment with 12.5-25 microM curcumin directly increased intracellular oxidative stress, 50-200 microM curcumin had far less effect. Pretreatment of cells with N-acetyl cysteine or alpha-tocopherol, two well known ROS scavengers, attenuated the intracellular ROS levels increases and converted the apoptosis to necrosis induced by 12.5-25 microM curcumin. Moreover, we observed a dose-dependent decrease in intracellular ATP levels after treatment of osteoblast cells with curcumin and pretreatment of cells with antimycin or 2-deoxyglucose to cause ATP depletion significantly converted 12.5-25 microM curcumin-induced apoptosis to necrosis, indicating that ATP (a known mediator of apoptotic versus necrotic death) is most likely involved in the switching mechanism. Overall, our results signify that curcumin dosage treatment determines the possible effect on ROS generation, intracellular ATP levels, and cell apoptosis or necrosis in osteoblast cells.

Curcumin Inhibits ROS Formation and Apoptosis in Methylglyoxal-Treated Human Hepatoma G2 Cells

Methylglyoxal (MG) is a reactive dicarbonyl compound endogenously produced mainly from glycolytic intermediates. Elevated MG levels in diabetes patients are believed to contribute to diabetic complications. MG is cytotoxic through induction of apoptosis. Curcumin, the yellow pigment of Curcuma longa, is known to have antioxidant and anti-inflammatory properties. In the present study, we investigated the effect of curcumin on MG-induced apoptotic events in human hepatoma G2 cells. We report that curcumin prevented MG-induced cell death and apoptotic biochemical changes such as mitochondrial release of cytochrome c, caspase-3 activation, and cleavage of PARP (poly [ADP-ribose] polymerase). Using the cell permeable dye 2',7'-dichlorofluorescein diacetate (DCF-DA) as an indicator of reactive oxygen species (ROS) generation, we found that curcumin abolished MG-stimulated intracellular oxidative stress. The results demonstrate that curcumin significantly attenuates MG-induced ROS formation, and suggest that ROS triggers cytochrome c release, caspase activation, and subsequent apoptotic biochemical changes.

Chemoprevention of photocarcinogenesis by selected dietary botanicals

Epidemiological, clinical and laboratory studies have implicated solar ultraviolet (UV) radiation as a tumor initiator, tumor promoter and complete carcinogen, and their excessive exposure can lead to the development of various skin disorders including melanoma and nonmelanoma skin cancers. Sunscreens are useful, but their protection is not adequate to prevent the risk of UV-induced skin cancer. It may be because of inadequate use, incomplete spectral protection and toxicity. Therefore new chemopreventive methods are necessary to protect the skin from photodamaging effects of solar UV radiation. Chemoprevention refers to the use of agents that can inhibit, reverse or retard the process of skin carcinogenesis. In recent years, considerable interest has been focused on identifying naturally occurring botanicals, specifically dietary, for the prevention of photocarcinogenesis. A wide variety of botanicals, mostly dietary flavonoids or phenolic substances, have been reported to possess substantial anticarcinogenic and antimutagenic activities because of their antioxidant and antiinflammatory properties. This review summarizes chemopreventive effects of some selected botanicals, such as apigenin, curcumin, grape seed proanthocyanidins, resveratrol, silymarin, and green tea polyphenols, against photocarcinogenesis in in vitro and in vivo systems. Attention has also been focused on highlighting the mechanism of chemopreventive action of these dietary botanicals. We suggest that in addition to the use of these botanicals as dietary supplements for the protection of photocarcinogenesis, these botanicals may favorably supplement sunscreens protection and may provide additional antiphotocarcinogenic protection including the protection against other skin disorders caused by solar UV radiation.

Induction of apoptosis in human leukemia cells by black tea and its polyphenol theaflavin

Treatment of human leukemic cell lines HL-60 and K-562 with extracts of green and black tea and their polyphenols epigallocatechin gallate and theaflavins, respectively, showed a dose dependent inhibition of growth as a result of cytotoxicity and suppression of cell proliferation. Based on the IC50 values obtained from cytotoxicity data it was clearly evident that black tea was as efficient as green tea. Analysis of polyphenol contents of tea extracts revealed that not only epigallocatechin gallate, which is a predominant polyphenol of green tea, but also theaflavin that is abundantly present in black tea affords significant chemotherapeutic action by imparting cytotoxicity to human leukemic cells. Electrophoretic analysis of fragmented DNA from treated cells displayed characteristic ladder pattern. Flow cytometric analysis revealed the dose dependent increase in sub-G1 peak. These criteria confirmed that cytotoxic activity of green and black tea was due to induction of apoptosis. Such induction was found to be mediated through activation of caspases 3 and 8, particularly caspase 3 and by altering apoptosis related genes as evident by down-regulation of Bcl-2 and up-regulation of Bax proteins.

Curcumin Suppresses Growth of Head and Neck Squamous Cell Carcinoma

PURPOSE

The purpose of this study was to determine whether curcumin would trigger cell death in the head and neck squamous cell carcinoma (HNSCC) cell lines CCL 23, CAL 27, and UM-SCC1 in a dose-dependent fashion.

EXPERIMENTAL DESIGN

HNSCC cells were treated with curcumin and assayed for in vitro growth suppression using 3-(4,5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide and fluorescence-activated cell sorting analyses. Expression of p16, cyclin D1, phospho-Ikappabeta, and nuclear factor-kappabeta (NF-kappabeta) were measured by Western blotting, gel shift, and immunofluorescence.

RESULTS

Addition of curcumin resulted in a dose-dependent growth inhibition of all three cell lines. Curcumin treatment resulted in reduced nuclear expression of NF-kappabeta. This effect on NF-kappabeta was further reflected in the decreased expression of phospho-Ikappabeta-alpha. Whereas the expression of cyclin D1, an NF-kappabeta-activated protein, was also reduced, there was no difference in the expression of p16 at the initial times after curcumin treatment. In vivo growth studies were done using nude mice xenograft tumors. Curcumin was applied as a noninvasive topical paste to the tumors and inhibition of tumor growth was observed in xenografts from the CAL27 cell line.

CONCLUSIONS

Curcumin treatment resulted in suppression of HNSCC growth both in vitro and in vivo. Our data support further investigation into the potential use for curcumin as an adjuvant or chemopreventive agent in head and neck cancer.