Demethoxycurcumin modulates prostate cancer cell proliferation via AMPK-induced down-regulation of HSP70 and EGFR

Effects of curcumin and ursolic acid in prostate cancer: A systematic review

The major barriers to phytonutrients in prostate cancer therapy are non-specific mechanisms and bioavailability issues. Studies have pointed to a synergistic combination of curcumin (CURC) and ursolic acid (UA). We investigate this combination using a systematic review process to assess the most likely mechanistic pathway and human testing in prostate cancer. We used the PRISMA statement to screen titles, abstracts, and the full texts of relevant articles and performed a descriptive analysis of the literature reviewed for study inclusion and consensus of the manuscript. The most common molecular and cellular pathway from articles reporting on the pathways and effects of CURC (n = 173) in prostate cancer was NF-κB (n = 25, 14.5%). The most common molecular and cellular pathway from articles reporting on the pathways and effects of UA (n = 24) in prostate cancer was caspase 3/caspase 9 (n = 10, 41.6%). The three most common molecular and cellular pathway from articles reporting on the pathways and effects of both CURC and UA (n = 193) in prostate cancer was NF-κB (n = 28, 14.2%), Akt (n = 22, 11.2%), and androgen (n = 19, 9.6%). Therefore, we have identified the potential synergistic target pathways of curcumin and ursolic acid to involve NF-κB, Akt, androgen receptors, and apoptosis pathways. Our review highlights the limited human studies and specific effects in prostate cancer.

The efficacy of natural bioactive compounds against prostate cancer: Molecular targets and synergistic activities

Globally, prostate cancer (PCa) is regarded as a challenging health issue, and the number of PCa patients continues to rise despite the availability of effective treatments in recent decades. The current therapy with chemotherapeutic drugs has been largely ineffective due to multidrug resistance and the conventional treatment has restricted drug accessibility to malignant tissues, necessitating a higher dosage resulting in increased cytotoxicity. Plant-derived bioactive compounds have recently attracted a great deal of attention in the field of PCa treatment due to their potent effects on several molecular targets and synergistic effects with anti-PCa drugs. This review emphasizes the molecular mechanism of phytochemicals on PCa cells, the synergistic effects of compound-drug interactions, and stem cell targeting for PCa treatment. Some potential compounds, such as curcumin, phenethyl-isothiocyanate, fisetin, baicalein, berberine, lutein, and many others, exert an anti-PCa effect via inhibiting proliferation, metastasis, cell cycle progression, and normal apoptosis pathways. In addition, multiple studies have demonstrated that the isolated natural compounds: d-limonene, paeonol, lanreotide, artesunate, and bicalutamide have potential synergistic effects. Further, a significant number of natural compounds effectively target PCa stem cells. However, further high-quality studies are needed to firmly establish the clinical efficacy of these phytochemicals against PCa.

Bisdemethoxycurcumin alleviates LPS-induced acute lung injury via activating AMPKα pathway

OBJECTIVE

Inflammation and oxidative stress contribute to the pathogenesis of acute lung injury (ALI), and subsequently result in rapid deterioration in health. Considering the indispensable role of bisdemethoxycurcumin (BDMC) in inflammation and oxidative stress, the present study aims to examine the effect of BDMC on sepsis-related ALI.

METHODS

C57BL/6 mice were administered with BDMC (100 mg/kg) or an equal volume of vehicle, and then injected with lipopolysaccharides (LPS) to induce ALI. We assessed the parameters of lung injury, inflammatory response and oxidative stress in lung tissues. Consistently, the macrophages with or without BDMC treatment were exposed to LPS to verify the effect of BDMC in vitro.

RESULTS

BDMC suppressed LPS-induced lung injury, inflammation and oxidative stress in vivo and in vitro. Mechanistically, BDMC increased the phosphorylation of AMPKα in response to LPS stimulation, and AMPK inhibition with Compound C almost completely blunted the protective effect of BDMC in LPS-treated mice and macrophages. Moreover, we demonstrated that BDMC activated AMPKα via the cAMP/Epac pathway.

CONCLUSION

Our study identifies the protective effect of BDMC against LPS-induced ALI, and the underlying mechanism may be related to the activation of cAMP/Epac/AMPKα signaling pathway.

Novel Anti-Cancer Products Targeting AMPK: Natural Herbal Medicine against Breast Cancer

Breast cancer is a common cancer in women worldwide. The existing clinical treatment strategies have been able to limit the progression of breast cancer and cancer metastasis, but abnormal metabolism, immunosuppression, and multidrug resistance involving multiple regulators remain the major challenges for the treatment of breast cancer. Adenosine 5'-monophosphate (AMP)-Activated Protein Kinase (AMPK) can regulate metabolic reprogramming and reverse the "Warburg effect" via multiple metabolic signaling pathways in breast cancer. Previous studies suggest that the activation of AMPK suppresses the growth and metastasis of breast cancer cells, as well as stimulating the responses of immune cells. However, some other reports claim that the development and poor prognosis of breast cancer are related to the overexpression and aberrant activation of AMPK. Thus, the role of AMPK in the progression of breast cancer is still controversial. In this review, we summarize the current understanding of AMPK, particularly the comprehensive bidirectional functions of AMPK in cancer progression; discuss the pharmacological activators of AMPK and some specific molecules, including the natural products (including berberine, curcumin, (-)-epigallocatechin-3-gallate, ginsenosides, and paclitaxel) that influence the efficacy of these activators in cancer therapy; and elaborate the role of AMPK as a potential therapeutic target for the treatment of breast cancer.

Disorders of cancer metabolism: The therapeutic potential of cannabinoids

Abnormal energy metabolism, as one of the important hallmarks of cancer, was induced by multiple carcinogenic factors and tumor-specific microenvironments. It comprises aerobic glycolysis, de novo lipid biosynthesis, and glutamine-dependent anaplerosis. Considering that metabolic reprogramming provides various nutrients for tumor survival and development, it has been considered a potential target for cancer therapy. Cannabinoids have been shown to exhibit a variety of anticancer activities by unclear mechanisms. This paper first reviews the recent progress of related signaling pathways (reactive oxygen species (ROS), AMP-activated protein kinase (AMPK), mitogen-activated protein kinases (MAPK), phosphoinositide 3-kinase (PI3K), hypoxia-inducible factor-1alpha (HIF-1α), and p53) mediating the reprogramming of cancer metabolism (including glucose metabolism, lipid metabolism, and amino acid metabolism). Then we comprehensively explore the latest discoveries and possible mechanisms of the anticancer effects of cannabinoids through the regulation of the above-mentioned related signaling pathways, to provide new targets and insights for cancer prevention and treatment.

In Vitro Phytochemical Screening, Cytotoxicity Studies of Curcuma longa Extracts with Isolation and Characterisation of Their Isolated Compounds

The Curcuma longa plant is endowed with multiple traditional and therapeutic utilities and is here explored for its phytochemical constituents and cytotoxic potential. Turmeric rhizomes were extracted from three different solvents and screened for the presence of different phytochemical constituents, observation of which indicated that the polar solvents favoured extraction of greater versatile phytochemical constituents. These extracts were investigated for their cytotoxic potential by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on three different of cell lines including SCC-29B (oral cancer cell line), DU-145 (prostate cancer cell line) and the Vero cell line (healthy cell line/non-cancerous cell line). This assay was performed by taking three extracts from isolated curcuminoids and a pure bioactive compound bisdemethoxycurcumin (BD). Bisdemethoxycurcumin was isolated from curcuminoids and purified by column and thin-layer chromatography, and its structural characterisation was performed with different spectroscopic techniques such as FTIR, NMR (¹H Proton and ¹³C Carbon-NMR) and LC-MS. Amongst the extracts, the ethanolic extracts exhibited stronger cytotoxic potential against the oral cancer cell line (SCC-29B) with an IC₅₀value of 11.27 μg/mL, and that this was too low of a cytotoxicity against the Vero cell line. Although, curcuminoids have also shown a comparable cytotoxic potential against SCC-29B (IC₅₀ value 16.79 μg/mL), it was not as potent against the ethanolic extract, and it was even found to be cytotoxic against healthy cell lines at a very low dose. While considering the isolated compound, bisdemethoxycurcumin, it also possessed a cytotoxic potential against the prostate cancer cell line (DU-145) (IC₅₀ value of 93.28 μg/mL), but was quite safe for the healthy cell line in comparison to doxorubicin.

Demethoxycurcumin induces apoptosis in HER2 overexpressing bladder cancer cells through degradation of HER2 and inhibiting the PI3K/Akt pathway

Bladder cancer is the most common malignancy of the urinary tract and arising from the epithelial lining of the urinary bladder. Resistance to cytotoxic therapies is associated with overexpression of oncogenic proteins; including HER2, and Akt in chemotherapy resistance of bladder cancer. Various studies demonstrated that curcuminoids, the most important active phenolic compounds of turmeric (Curcuma longa), have anti-tumor activities in a wide range of human malignant cell lines. The aim of this study is to evaluate whether curcuminoids (curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcumin) could repress the expression of HER2 in HER2-overexpressing bladder cancer cells. Among the test compounds, DMC significantly suppressed the expression of HER2, and preferentially inhibited cell proliferation and induced apoptosis in HER2-overexpressing bladder cancer cells. DMC decreases HER2 level through inhibiting the interaction of HER2 and Hsp90. Our study also indicated that DMC showed additive activity in combination with chemotherapeutic agents, including paclitaxel and cisplatin. These findings show that DMC should be developed further as a new antitumor drug candidate for treatment of HER2-overexpressing bladder cancer.

Phytocompounds Targeting Metabolic Reprogramming in Cancer: An Assessment of Role, Mechanisms, Pathways, and Therapeutic Relevance

The metabolism of cancer is remarkably different from that of normal cells and confers a variety of benefits, including the promotion of other cancer hallmarks. As the rewired metabolism is a near-universal property of cancer cells, efforts are underway to exploit metabolic vulnerabilities for therapeutic benefits. In the continued search for safer and effective ways of cancer treatment, structurally diverse plant-based compounds have gained substantial attention. Here, we present an extensive assessment of the role of phytocompounds in modulating cancer metabolism and attempt to make a case for the use of plant-based compounds in targeting metabolic vulnerabilities of cancer. We discuss the pharmacological interactions of phytocompounds with major metabolic pathways and evaluate the role of phytocompounds in the regulation of growth signaling and transcriptional programs involved in the metabolic transformation of cancer. Lastly, we examine the potential of these compounds in the clinical management of cancer along with limitations and challenges.

Heat Shock Proteins in Lymphoma Immunotherapy

Immunotherapy harnessing the host immune system for tumor destruction revolutionized oncology research and advanced treatment strategies for lymphoma patients. Lymphoma is a heterogeneous group of cancer, where the central roles in pathogenesis play immune evasion and dysregulation of multiple signaling pathways. Immunotherapy-based approaches such as engineered T cells (CAR T), immune checkpoint modulators and NK cell-based therapies are now in the frontline of lymphoma research. Even though emerging immunotherapies showed promising results in treating lymphoma patients, low efficacy and on-target/off-tumor toxicity are of a major concern. To address that issue it is suggested to look into the emerging role of heat shock proteins. Heat shock proteins (HSPs) showed to be highly expressed in lymphoma cells. HSPs are known for their abilities to modulate immune responses and inhibit apoptosis, which made their successful entry into cancer clinical trials. Here, we explore the role of HSPs in Hodgkin and Non-Hodgkin lymphoma and their involvement in CAR T therapy, checkpoint blockade and NK cell- based therapies. Understanding the role of HSPs in lymphoma pathogenesis and the ways how HSPs may enhance anti-tumor responses, may help in the development of more effective, specific and safe immunotherapy.

A combination index and glycoproteomics-based approach revealed synergistic anticancer effects of curcuminoids of turmeric against prostate cancer PC3 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Herbal medicines (HMs) often exert integration effects, including synergistic, additive and antagonistic effects, in such ways that they act on multiple targets and multiple pathways on account of their multiple components. Turmeric, made from the rhizome of Curcuma longa L., is a well-known HM prescribed in the polyherbal formulas for cancer treatment in traditional Chinese medicines (TCMs). However, neither the multiple anticancer compounds of turmeric nor the integration effects of these components are fully known.

AIM OF THE STUDY

This work aims to develop a systematic approach to reveal the integration effect mechanisms of multiple anticancer compounds in turmeric against prostate cancer PC3 cells.

MATERIALS AND METHODS

Combination index and omics technologies were applied to profile the integration effect mechanisms of bioactive compounds in proportions naturally found in turmeric. PC3 cell line (a prostate cancer cell line) fishing and high resolution mass spectrometry were employed to screen and identify the anticancer compounds from turmeric. The combinations which contain different cell-bound compounds in natural proportions were prepared for further evaluation of anti-cancer activity by using cell viability assays, and assessment of cell apoptosis and cell cycle analysis. Combination index analysis was applied to study the integration effects of the anticancer compounds in their natural proportions. Finally, quantitative glycoproteomics/proteomics and Western blot were implemented to reveal the potential synergistic effect mechanisms of the anticancer compounds based on their natural proportions in turmeric.

RESULTS

Three curcuminoids (curcumin, CUR; demethoxycurcumin, DMC; bisdemethoxycurcumin, BDMC) in turmeric were discovered and shown to possess significant synergistic anticancer activities. Combination index analysis revealed an additive effect of CUR combined with DMC or BDMC and a slight synergistic effect of DMC combined with BDMC in natural proportions in turmeric, while a combination of all three curcuminoids (CUR, DMC and BDMC) at a ratio of 1:1:1 yielded superior synergistic effects. Interestingly, the presence of BDMC and DMC are essential for synergistic effect. Glycoproteomics and proteomics demonstrated that different curcuminoids regulate various protein pathways, such as ribosome, glycolysis/gluconeogenesis, biosynthesis of amino acids, and combination of CUR + DMC + BDMC showed the most powerful effects on down-regulation of protein expression.

CONCLUSIONS

Our analytical approach provides a systematic understanding of the holistic activity and integration effects of the anti-cancer compounds in turmeric and three curcuminoids of turmeric showed a synergistic effect on PC3 cells.

Dimethoxycurcumin reduces proliferation and induces apoptosis in renal tumor cells more efficiently than demethoxycurcumin and curcumin

Curcumin (Cur), is a pigment with antiproliferative activity but has some pharmacokinetic limitations, which led researchers to look for more effective structure analogs. This work investigated the effects of Cur and compared them with the two analogs, demethoxycurcumin (DeMC) and dimethoxycurcumin (DiMC), to elucidate their mechanisms of action. The cytotoxic, antiproliferative, and genotoxic effects these compounds were correlated based on gene expression analysis in the human renal adenocarcinoma cells (786-O). Cur decreased CYP2D6 expression and exhibited cytotoxic effects, such as inducing monopolar spindle formation and mitotic arrest mediated by the increase in CDKN1A (p21) mRNA. This dysregulation induced cell death through a caspase-independent pathway but was mediated by decrease in MTOR and BCL2 mRNA expression, suggesting that apoptosis occurred by autophagy. DeMC and DiMC had similar effects in that they induced monopolar spindle and mitotic arrest, were genotoxic, and activated GADD45A, an important molecule in repair mechanisms, and CDKN1A. However, the induction of apoptosis by DeMC was delayed and regulated by the decrease of antiapoptotic mRNA BCL.XL and subsequent activation of caspase 9 and caspase 3/7. DiMC treatment increased the expression of CYP1A2, CYP2C19, and CYP3A4 and exhibited higher cytotoxicity compared with other compounds. It induced apoptosis by increasing mRNA expression of BBC3, MYC, and CASP7 and activation of caspase 9 and caspase 3/7. These data revealed that different gene regulation processes are involved in cell death induced by Cur, DeMC, and DiMC. All three can be considered as promising chemotherapy candidates, with DiMC showing the greatest potency.

Demethoxycurcumin increases the sensitivity of cisplatin-resistant non-small lung cancer cells to cisplatin and induces apoptosis by activating the caspase signaling pathway

Patients with non-small cell lung cancer (NSCLC) can develop strong drug resistance following long-term treatment with platinum-based drugs. Increasing doses of chemotherapeutic drugs fail to obtain better results, and serious complications occur. It has been demonstrated that upregulation of excision repair cross-complementary 1 (ERCC1) in lung cancer cells is closely associated with cell resistance to platinum-based chemotherapy. In addition, curcumin (CMN) enhances antitumor effects in NSCLC by downregulating ERCC1. The aim of the present study was to investigate the effects of demethoxycurcumin (DMC), a curcuminoid, on the reversal of resistance of NSCLC cells in vitro and in vivo. The present study demonstrated that DMC significantly increased the sensitivity of DDP in DDP-resistant A549 (A549/DDP) cells. The results from an MTT assay demonstrated that DMC combined with DDP significantly attenuated the proliferation of A549/DDP cells. Furthermore, DMC exhibited decreased toxicity in normal lung fibroblast MRC-5 cells. In addition, following treatment of A549/DDP cells with a combination of DMC and DDP, the expression of ERCC1 was reduced, the protein levels of Bcl-2 and Bax were decreased and increased, respectively, whereas caspase-3 was activated, according to results from western blotting. Finally, DDP combined with DMC significantly attenuated A549/DDP cell-derived tumor growth in vivo. Taken together, the findings from the present study suggested that DMC in combination with DDP may be considered as a novel combination regimen for restoring DDP sensitivity in DDP-resistant NSCLC cells.

Dual Targeting of the p38 MAPK-HO-1 Axis and cIAP1/XIAP by Demethoxycurcumin Triggers Caspase-Mediated Apoptotic Cell Death in Oral Squamous Cell Carcinoma Cells

Demethoxycurcumin (DMC) is a curcumin analogue with better stability and higher aqueous solubility than curcumin after oral ingestion and has the potential to treat diverse cancers, including oral squamous cell carcinoma (OSCC). The aim of this study was to investigate the anticancer effects and underlying mechanisms of DMC against OSCC. We found that DMC suppressed cell proliferation via simultaneously inducing G2/M-phase arrest and cell apoptosis. Mechanistic investigations found that the downregulation of cellular IAP 1 (cIAP1)/X-chromosome-linked IAP (XIAP) and upregulation of heme oxygenase-1 (HO-1) were critical for DMC-induced caspase-8/-9/-3 activation and apoptotic cell death. Moreover, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK)1/2 were activated by DMC treatment in OSCC cells, and only the inhibition of p38 MAPK significantly abolished DMC-induced HO-1 expression and caspase-8/-9/-3 activation. The analyses of clinical datasets revealed that patients with head and neck cancers expressing high HO-1 and low cIAP1 had the most favorable prognoses. Furthermore, a combinatorial treatment of DMC with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib, significantly enhanced the inhibitory effect of gefitinib on the proliferation of OSCC cells. Overall, the current study supported a role for DCM as part of a therapeutic approach for OSCC through suppressing IAPs and activating the p38-HO-1 axis.

HSP70 Multi-Functionality in Cancer

The 70-kDa heat shock proteins (HSP70s) are abundantly present in cancer, providing malignant cells selective advantage by suppressing multiple apoptotic pathways, regulating necrosis, bypassing cellular senescence program, interfering with tumor immunity, promoting angiogenesis and supporting metastasis. This direct involvement of HSP70 in most of the cancer hallmarks explains the phenomenon of cancer "addiction" to HSP70, tightly linking tumor survival and growth to the HSP70 expression. HSP70 operates in different states through its catalytic cycle, suggesting that it can multi-function in malignant cells in any of these states. Clinically, tumor cells intensively release HSP70 in extracellular microenvironment, resulting in diverse outcomes for patient survival. Given its clinical significance, small molecule inhibitors were developed to target different sites of the HSP70 machinery. Furthermore, several HSP70-based immunotherapy approaches were assessed in clinical trials. This review will explore different roles of HSP70 on cancer progression and emphasize the importance of understanding the flexibility of HSP70 nature for future development of anti-cancer therapies.

Antitumor effects of curcumin: A lipid perspective

Lipid metabolism plays an important role in cancer development due to the necessities of rapidly dividing cells to increase structural, energetic, and biosynthetic demands for cell proliferation. Basically, obesity, type 2 diabetes, and other related diseases, and cancer are associated with a common hyperactivated "lipogenic state." Recent evidence suggests that metabolic reprogramming and overproduction of enzymes involved in the synthesis of fatty acids are the new hallmarks of cancer, which occur in an early phase of tumorigenesis. As the first evidence to confirm dysregulated lipid metabolism in cancer cells, the overexpression of fatty acid synthase (FAS) was observed in breast cancer patients and demonstrated the role of FAS in cancer. Other enzymes of fatty acid synthesis have recently been found to be dysregulated in cancer, including ATP-dependent citrate lyase and acetyl-CoA carboxylase, which further underscores the connection of these metabolic pathways with cancer cell survival and proliferation. The degree of overexpression of lipogenic enzymes and elevated lipid utilization in tumors is closely associated with cancer progression. The question that arises is whether the progression of cancer can be suppressed, or at least decelerated, by modulating gene expression related to fatty acid metabolism. Curcumin, due to its effects on the regulation of lipogenic enzymes, might be able to suppress, or even cause regression of tumor growth. This review discusses recent evidence concerning the important role of lipogenic enzymes in the metabolism of cancer cells and whether the inhibitory effects of curcumin on lipogenic enzymes is therapeutically efficacious.

Demethoxycurcumin sensitizes the response of non-small cell lung cancer to cisplatin through downregulation of TP and ERCC1-related pathways

BACKGROUND

Excision repair cross-complementary 1 (ERCC1) overexpression in lung cancer cells is strongly correlated with its resistance to platinum-based chemotherapy. Overexpression of thymidine phosphorylase (TP) reverts platinum-induced cancer cell death.

PURPOSE

Curcumin has been reported to enhance antitumor properties through the suppression of TP and ERCC1 in non-small cell lung carcinoma cells (NSCLC). Nevertheless, whether two other curcuminoids, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) from Curcuma longa demonstrate antitumor activity like that of curcumin remain unknown.

METHODS

MTT assay was conducted to determine the cell cytotoxicity. Western blotting was used to determine the protein expressions. Docking is the virtual screening of a database of compounds and predicting the strongest binders based on various scoring functions. BIOVIA Discovery Studio 4.5 (D.S. 4.5) were used for docking.

RESULTS

Firstly, when compared with curcumin and BDMC, DMC exhibited the most potent cytotoxic effect on NSCLC, most importantly, MRC-5, a lung fetal fibroblast, was insensitive to DMC (under 30 µM). Secondly, DMC alone significantly inhibited on-target cisplatin (CDDP) resistance protein, ERCC1, via PI3K-Akt-snail pathways, and TP protein expression in A549 cells. Thirdly, DMC treatment markedly increased post-target CDDP resistance pathway including Bax and cytochrome c. DMC significantly decreased Bcl-2 protein expressions. Finally, MTT assay indicated that DMC significantly increased CDDP-induced cytotoxicity and was confirmed with an increased Bax/Bcl-2 ratio, indicating upregulation of caspase-3.

CONCLUSIONS

We concluded that enhancement of the cytotoxicity to CDDP by coadminstration with DMC was mediated by down-regulation of the expression of TP and ERCC1, regulated by PI3K-Akt-Snail pathway inactivation.

Demethoxycurcumin-Loaded Chitosan Nanoparticle Downregulates DNA Repair Pathway to Improve Cisplatin-Induced Apoptosis in Non-Small Cell Lung Cancer

Demethoxycurcumin (DMC), through a self-assembled amphiphilic carbomethyl-hexanoyl chitosan (CHC) nanomatrix has been successfully developed and used as a therapeutic approach to inhibit cisplatin-induced drug resistance by suppressing excision repair cross-complementary 1 (ERCC1) in non-small cell lung carcinoma cells (NSCLC). Previously, DMC significantly inhibited on-target cisplatin resistance protein, ERCC1, via PI3K-Akt-snail pathways in NSCLC. However, low water solubility and bioavailability of DMC causes systemic elimination and prevents its clinical application. To increase its bioavailability and targeting capacity toward cancer cells, a DMC-polyvinylpyrrolidone core phase was prepared, followed by encapsulating in a CHC shell to form a DMC-loaded core-shell hydrogel nanoparticles (DMC-CHC NPs). We aimed to understand whether DMC-CHC NPs efficiently potentiate cisplatin-induced apoptosis through downregulation of ERCC1 in NSCLC. DMC-CHC NPs displayed good cellular uptake efficiency. Dissolved in water, DMC-CHC NPs showed comparable cytotoxic potency with free DMC (dissolved in DMSO). A sulforhodamine B (SRB) assay indicated that DMC-CHC NPs significantly increased cisplatin-induced cytotoxicity by highly efficient intracellular delivery of the encapsulated DMC. A combination of DMC-CHC NPs and cisplatin significantly inhibited on-target cisplatin resistance protein, ERCC1, via the PI3K-Akt pathway. Also, this combination treatment markedly increased the post-target cisplatin resistance pathway including bax, and cytochrome c expressions. Thymidine phosphorylase (TP), a main role of the pyrimidine salvage pathway, was also highly inhibited by the combination treatment. The results suggested that enhancement of the cytotoxicity to cisplatin via administration of DMC-CHC NPs was mediated by down-regulation of the expression of TP, and ERCC1, regulated via the PI3K-Akt pathway.

Targeting Tumor Metabolism with Plant-Derived Natural Products: Emerging Trends in Cancer Therapy

Recognition of neoplastic metabolic reprogramming as one of cancer's hallmarks has paved the way for developing novel metabolism-targeted therapeutic approaches. The use of plant-derived natural bioactive compounds for this endeavor is especially promising, due to their diverse structures and multiple targets. Hence, over the past decade, a growing number of studies have assessed the impact of phytochemicals on tumor cell metabolism, aiming at improving current knowledge on their mechanisms of action and, at the same time, evaluating their potential as anti-cancer metabolic modulators. In this Review, we focus on three classes of plant-derived compounds with promising anti-cancer activity-phenolic compounds, isoprenoids, and alkaloids-to describe their effects on major energetic and biosynthetic pathways of human tumor cells. Such a comprehensive and integrated account of the ability of these compounds to hit different metabolic targets is expected to contribute to the rational design and critical assessment of novel anti-cancer therapies based on natural-product-mediated metabolic reprogramming.

Demethoxycurcumin: A naturally occurring curcumin analogue with antitumor properties

The eradication of cancer in a patient remains an elusive challenge despite advances in early detection and diagnosis, chemo- and immunotherapy, pinpoint radiation treatments, and expert surgical intervention. Although significant gains have been made in our understanding of cancer cell biology, a definite cure for most cancers does not exist at present. Thus, it is not surprising that the research and medical communities continue to explore the importance and therapeutic potential of natural products in their multimodality cancer treatment approach. Curcuminoids found in turmeric are one such class of natural products that have been extensively investigated for their potential to halt the progression of cancer cell proliferation and, more important, to stop metastasis from occurring. In this review, we examine one curcuminoid (demethoxycurcumin [DMC]) largely because of its increased stability and better aqueous solubility at physiological pH, unlike the more well-known curcuminoid (curcumin), which is largely unabsorbed after oral ingestion. The present review will focus on the signaling pathways that DMC utilizes to modulate the growth, invasion, and metastasis of cancer cells in an effort to provide enhanced mechanistic insight into DMC's action as it pertains to brain, ovarian, breast, lung, skin, and prostate cancer. Additionally, this review will attempt to provide an overview of DMC's mechanism of action by modulating apoptosis, cell cycle, angiogenesis, metastasis, and chemosensitivity. Lastly, it is hoped that increased understanding will be gained concerning DMC's interactive role with microRNA-551a, 5' adenosine monophosphate-activated protein kinase, nuclear factor-κB, Wnt inhibitory factor-1, and heat shock protein 70 to affect the progression of cancer.

Novel Polyphenols That Inhibit Colon Cancer Cell Growth Affecting Cancer Cell Metabolism

New series of polyphenols with a hydrophilic galloyl-based head and a hydrophobic N-acyl tail, linked through a serinol moiety, have been synthesized and tested against colon cancer cell growth. Our structure activity relationship studies revealed that galloyl moieties are essential for growth inhibition. Moreover, the length of the N-acyl chain is crucial for the activity. Introduction of a (Z) double bond in the acyl chain increased the anticancer properties. Our findings demonstrate that 16, the most potent compound within this series, has inhibitory effects on colon cancer cell growth and metabolism (glycolysis and mitochondrial respiration) at the same time that it activates 5'AMP-activated kinase (AMPK) and induces apoptotic cell death. Based on these results, we propose that 16 might reprogram colon cancer cell metabolism through AMPK activation. This might lead to alterations on cancer cell bioenergy compromising cancer cell viability. Importantly, these antiproliferative and proapoptotic effects are selective for cancer cells. Accordingly, these results indicate that 16, with an unsaturated C18 chain, might be a useful prototype for the development of novel colon cancer cell growth inhibitors affecting cell metabolism.

Curcuminoids combined with gefitinib mediated apoptosis and autophagy of human oral cancer SAS cells in vitro and reduced tumor of SAS cell xenograft mice in vivo

Gefitinib has been used for cancer patients and curcumin (CUR), demethoxycurcumin (DMC), or bisdemethoxycurcumin (BDMC) also shown to induce cancer cell apoptosis. However, no report shows the combination of gefitinib with, CUR, DMC, or BDMC induce cell apoptosis and autophagy in human oral cancer cells. In this study, we investigated the effects of gefitinib with or without CUR, DMC, or BDMC co-treatment on the cell viability, apoptotic cell death, autophagy, mitochondria membrane potential (MMP), and caspase-3 activities by flow cytometry assay and autophagy by acridine orange (AO) staining in human oral cancer SAS cells. Results indicated that gefitinib co-treated with CUR, DMC, or BDMC decreased total viable cell number through the induction of cell apoptosis and autophagy and decreased the levels of MMP and increased caspase-3 activities in SAS cells. Western blotting indicated that gefitinib combined with CUR, DMC, or BDMC led to decrease Bcl-2 protein expression which is an antiapoptotic protein and to increase ATG5, Beclin 1, p62/SQSTM1, and LC3 expression that associated with cell autophagy in SAS cells. Gefitinib combined with CUR and DMC led to significantly reduce the tumor weights and volumes in SAS cell xenograft nude mice but did not affect the total body weights. Based on those observations, we suggest that the combination of gefitinib with CUR, DMC, and BDMC can be a potential anticancer agent for human oral cancer in future.

Demethoxycurcumin inhibited human epithelia ovarian cancer cells’ growth via up-regulating miR-551a

Curcumin is a natural agent that has ability to dampen tumor cells’ growth. However, the natural form of curcumin is prone to degrade and unstable in vitro. Here, we demonstrated that demethoxycurcumin (a curcumin-related demethoxy compound) could inhibit cell proliferation and induce apoptosis of ovarian cancer cells. Moreover, IRS2/PI3K/Akt axis was inactivated in cells treated with demethoxycurcumin. Quantitative real-time reverse transcription polymerase chain reaction demonstrated that miR-551a was down-regulated in ovarian cancer tissues and ovarian cancer cell lines. Over-expression of miR-551a inhibited cell proliferation and induced apoptosis of ovarian cancer cells, whereas down-regulation of miR-551a exerted the opposite function. Luciferase assays confirmed that there was a binding site of miR-551a in IRS2, and we found that miR-551a exerted tumor-suppressive function by targeting IRS2 in ovarian cancer cells. Remarkably, miR-551a was up-regulated in the cells treated with demethoxycurcumin, and demethoxycurcumin suppressed IRS2 by restoration of miR-551a. In conclusion, demethoxycurcumin hindered ovarian cancer cells’ malignant progress via up-regulating miR-551a.

Heat Shock Proteins and Cancer

Heat shock proteins (HSPs) constitute a large family of proteins involved in protein folding and maturation whose expression is induced by heat shock or other stressors. The major groups are classified based on their molecular weights and include HSP27, HSP40, HSP60, HSP70, HSP90, and large HSPs. HSPs play a significant role in cellular proliferation, differentiation, and carcinogenesis. In this article we comprehensively review the roles of major HSPs in cancer biology and pharmacology. HSPs are thought to play significant roles in the molecular mechanisms leading to cancer development and metastasis. HSPs may also have potential clinical uses as biomarkers for cancer diagnosis, for assessing disease progression, or as therapeutic targets for cancer therapy.

Anticancer Activity of Curcumin and Its Analogues: Preclinical and Clinical Studies

Curcumin has been shown to have a wide variety of therapeutic effects, ranging from anti-inflammatory, chemopreventive, anti-proliferative, and anti-metastatic. This review provides an overview of the recent research conducted to overcome the problems with the bioavailability of curcumin, and of the preclinical and clinical studies that have reported success in combinatorial strategies coupling curcumin with other treatments. Research on the signaling pathways that curcumin treatment targets shows that it potently acts on major intracellular components involved in key processes such as genomic modulations, cell invasion and cell death pathways. Curcumin is a promising molecule for the prevention and treatment of cancer.

Enhanced Cognitive Effects of Demethoxycurcumin, a Natural Derivative of Curcumin on Scopolamine-Induced Memory Impairment in Mice

In the present study, we examined the ameliorating effects of demethoxycurcumin (DMC) on memory impairment induced by scopolamine using passive avoidance and Morris water maze tests in mice. Moreover, to determine the neurobiological effects underlying the ameliorating effects of the DMC, choline acetyltransferase (ChAT) immunoreactivity was evaluated in mice exposed to scopolamine. Our results demonstrated that chronic oral administration (28 days) of DMC (10 mg/kg) improved scopolamine-induced learning impairment in the passive avoidance task and memory impairment in the Morris water maze. Moreover, Choline acetyltransferase (ChAT) activity in the DMC-treated group was significantly increased to 33.03% compared with the control group. Our present finding suggests that DMC ameliorates memory impairments induced by scopolamine treatment through reversing the reduction of hippocampal ChAT expression in mice.

Curcumin Attenuated Bupivacaine-Induced Neurotoxicity in SH-SY5Y Cells Via Activation of the Akt Signaling Pathway

Bupivacaine is widely used for regional anesthesia, spinal anesthesia, and pain management. However, bupivacaine could cause neuronal injury. Curcumin, a low molecular weight polyphenol, has a variety of bioactivities and may exert neuroprotective effects against damage induced by some stimuli. In the present study, we tested whether curcumin could attenuate bupivacaine-induced neurotoxicity in SH-SY5Y cells. Cell injury was evaluated by examining cell viability, mitochondrial damage and apoptosis. We also investigated the levels of activation of the Akt signaling pathway and the effect of Akt inhibition by triciribine on cell injury following bupivacaine and curcumin treatment. Our findings showed that the bupivacaine treatment could induce neurotoxicity. Pretreatment of the SH-SY5Y cells with curcumin significantly attenuated bupivacaine-induced neurotoxicity. Interestingly, the curcumin treatment increased the levels of Akt phosphorylation. More significantly, the pharmacological inhibition of Akt abolished the cytoprotective effect of curcumin against bupivacaine-induced cell injury. Our data suggest that pretreating SH-SY5Y cells with curcumin provides a protective effect on bupivacaine-induced neuronal injury via activation of the Akt signaling pathway.

Mechanism of dihydroartemisinin-induced apoptosis in prostate cancer PC3 cells: An iTRAQ-based proteomic analysis

AIMS

Prostate cancer (PCa) is one of the most common cancers in men in the world. Advanced PCa, especially castration-resistant PCa (CRPC), is difficult to cure. There is an urgent need to develop novel agents for CPRC. Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin and is a well-known antimalarial drug. DHA has been documented to be a potential anticancer agent for PCa. However, the mechanisms underlying the anticancer activity of DHA are still unknown.

MAIN METHODS

Proteomics analysis based on iTRAQ technology was performed to determine the protein profile changes in human prostate cancer PC3 cells treated by DHA, and apoptosis was detected by flow cytometry and transmission electron microscopy.

KEY FINDINGS

DHA induced obvious apoptosis in PC3 cells. Using iTRAQ technology, we found 86 differentially expressed proteins linked to the cytotoxicity of DHA in PC3 cells. Gene ontology analysis showed the differentially expressed proteins were mainly associated with the protein synthesis and translation. Protein interaction network analysis and KEGG pathway analysis revealed altered aminoacyl-tRNA biosynthesis and metabolic pathways. Moreover, one candidate protein, heat shock protein HSP70 (HSPA1A), was identified by western blot analysis.

SIGNIFICANCE

Our results indicate that multiple mechanisms involved in the anticancer activity of DHA in PC3 cells. Decreased HSP70 expression may have an important role in DHA-induced apoptosis in PC3 cells. Our data also provide novel insights into the anticancer mechanisms of DHA.

Growth factors mediated cell signalling in prostate cancer progression: Implications in discovery of anti-prostate cancer agents

Cancer is one of the leading causes of mortality amongst world's population, in which prostate cancer is one of the most encountered malignancies among men. Globally, it is the sixth leading cause of cancer-related death in men. Prostate cancer is more prevalent in the developed world and is increasing at alarming rates in the developing countries. Prostate cancer is mostly a very sluggish progressing disease, caused by the overproduction of steroidal hormones like dihydrotestosterone or due to over-expression of enzymes such as 5-α-reductase. Various studies have revealed that growth factors play a crucial role in the progression of prostate cancer as they act either by directly elevating the level of steroidal hormones or upregulating enzyme efficacy by the active feedback mechanism. Presently, treatment options for prostate cancer include radiotherapy, surgery and chemotherapy. If treatment is done with prevailing traditional chemotherapy; it leads to resistance and development of androgen-independent prostate cancer that further complicates the situation with no cure option left. The current review article is an attempt to cover and establish an understanding of some major signalling pathways intervened through survival factors (IGF-1R), growth factors (TGF-α, EGF), Wnt, Hedgehog, interleukin, cytokinins and death factor receptor which are frequently dysregulated in prostate cancer. This will enable the researchers to design and develop better therapeutic strategies targeting growth factors and their cross talks mediated prostate cancer cell signalling.

Dietary phytochemicals alter epigenetic events and signaling pathways for inhibition of metastasis cascade: phytoblockers of metastasis cascade

Cancer metastasis is a multistep process in which a cancer cell spreads from the site of the primary lesion, passes through the circulatory system, and establishes a secondary tumor at a new nonadjacent organ or part. Inhibition of cancer progression by dietary phytochemicals (DPs) offers significant promise for reducing the incidence and mortality of cancer. Consumption of DPs in the diet has been linked to a decrease in the rate of metastatic cancer in a number of preclinical animal models and human epidemiological studies. DPs have been reported to modulate the numerous biological events including epigenetic events (noncoding micro-RNAs, histone modification, and DNA methylation) and multiple signaling transduction pathways (Wnt/β-catenin, Notch, Sonic hedgehog, COX-2, EGFR, MAPK-ERK, JAK-STAT, Akt/PI3K/mTOR, NF-κB, AP-1, etc.), which can play a key role in regulation of metastasis cascade. Extensive studies have also been performed to determine the molecular mechanisms underlying antimetastatic activity of DPs, with results indicating that these DPs have significant inhibitory activity at nearly every step of the metastatic cascade. DPs have anticancer effects by inducing apoptosis and by inhibiting cell growth, migration, invasion, and angiogenesis. Growing evidence has also shown that these natural agents potentiate the efficacy of chemotherapy and radiotherapy through the regulation of multiple signaling pathways. In this review, we discuss the variety of molecular mechanisms by which DPs regulate metastatic cascade and highlight the potentials of these DPs as promising therapeutic inhibitors of cancer.

Activation of the Tumor Suppressor PP2A Emerges as a Potential Therapeutic Strategy for Treating Prostate Cancer

Protein phosphatase 2A (PP2A) is a tumor suppressor complex that has recently been reported as a novel and highly relevant molecular target in prostate cancer (PCa). However, its potential therapeutic value remains to be fully clarified. We treated PC-3 and LNCaP cell lines with the PP2A activators forskolin and FTY720 alone or combined with the PP2A inhibitor okadaic acid. We examined PP2A activity, cell growth, prostasphere formation, levels of PP2A phosphorylation, CIP2A and SET expression, and AKT and ERK activation. Interestingly, both forskolin and FTY720 dephosphorylated and activated PP2A, impairing proliferation and prostasphere formation and inducing changes in AKT and ERK phosphorylation. Moreover, FTY720 led to reduced CIP2A levels. Treatment with okadaic acid impaired PP2A activation thus demonstrating the antitumoral PP2A-dependent mechanism of action of both forskolin and FTY720. Levels of PP2A phosphorylation together with SET and CIP2A protein expression were studied in 24 PCa patients and both were associated with high Gleason scores and presence of metastatic disease. Altogether, our results suggest that PP2A inhibition could be involved in PCa progression, and the use of PP2A-activating drugs might represent a novel alternative therapeutic strategy for treating PCa patients.

Dietary polyphenols in prevention and treatment of prostate cancer

Prostate cancer is the most prevalent disease affecting males in many Western countries, with an estimated 29,480 deaths in 2014 in the US alone. Incidence rates for prostate cancer deaths have been decreasing since the early 1990s in men of all races/ethnicities, though they remain about 60% higher in African Americans than in any other group. The relationship between dietary polyphenols and the prevention of prostate cancer has been examined previously. Although results are sometimes inconsistent and variable, there is a general agreement that polyphenols hold great promise for the future management of prostate cancer. Various dietary components, including polyphenols, have been shown to possess anti-cancer properties. Generally considered as non-toxic, dietary polyphenols act as key modulators of signaling pathways and are therefore considered ideal chemopreventive agents. Besides possessing various anti-tumor properties, dietary polyphenols also contribute to epigenetic changes associated with the fate of cancer cells and have emerged as potential drugs for therapeutic intervention. Polyphenols have also been shown to affect post-translational modifications and microRNA expressions. This article provides a systematic review of the health benefits of selected dietary polyphenols in prostate cancer, especially focusing on the subclasses of polyphenols, which have a great effect on disease prevention and treatment.

Demethoxycurcumin modulates human P-glycoprotein function via uncompetitive inhibition of ATPase hydrolysis activity

Curcuminoids are major components of Curcuma longa L., which is widely used as spice in food. This study aimed at identifying whether curcumin, demethoxycurcumin, and bisdemethoxycurcumin could modulate efflux function of human P-glycoprotein and be used as chemosensitizers in cancer treatments. Without altering P-glycoprotein expression levels and conformation, the purified curcuminoids significantly inhibited P-glycoprotein efflux function. In rhodamine 123 efflux and calcein-AM accumulation assays, demethoxycurcumin demonstrated the highest inhibition potency (inhibitory IC50 = 1.56 ± 0.13 μM) among the purified curcuminoids, as well as in the fold of reversal assays. Demethoxycurcumin inhibited P-glycoprotein-mediated ATP hydrolysis under concentrations of <1 μM and efficiently inhibited 200 μM verapamil-stimulated ATPase activity, indicating a high affinity of demethoxycurcumin for P-glycoprotein. These results suggested that demethoxycurcumin may be a potential additive natural product in combination with chemotherapeutic agents in drug-resistant cancers.

Metformin Induced AMPK Activation, G0/G1 Phase Cell Cycle Arrest and the Inhibition of Growth of Esophageal Squamous Cell Carcinomas In Vitro and In Vivo

Esophageal squamous cell carcinomas (ESCC) have become a severe threat to health and the current treatments for ESCC are frequently not effective. Recent epidemiological studies suggest that the anti-hyperglycemic agent metformin may reduce the risk of developing cancer, including ESCC, among diabetic patients. However, the antitumor effects of metformin on ESCC and the mechanisms underlying its cell cycle regulation remain elusive. The findings reported herein show that the anti-proliferative action of metformin on ESCC cell lines is partially mediated by AMPK. Moreover, we observed that metformin induced G0/G1 phase arrest accompanied by the up-regulation of p21CIP1 and p27KIP1. In vivo experiments further showed that metformin inhibited tumor growth in a ESCC xenograft model. Most importantly, the up-regulation of AMPK, p53, p21CIP1, p27KIP1 and the down-regulation of cyclinD1 are involved in the anti-tumor action of metformin in vivo. In conclusion, metformin inhibits the growth of ESCC cells both in cell cultures and in an animal model. AMPK, p53, p21CIP1, p27KIP1 and cyclinD1 are involved in the inhibition of tumor growth that is induced by metformin and cell cycle arrest in ESCC. These findings indicate that metformin has the potential for use in the treatment of ESCC.

Curcuminoids and acetylacetone: iron complexes as studied by electrospray ionization mass spectrometry

Curcumin complexes with iron ions were investigated by electrospray ionization mass spectrometry. It was shown that in methanol solutions of curcumin and iron(III) ions, complexes are formed with a stoichiometry of 1 : 1, 2 : or 3 : 1. Curcumi-iron(II) complexes were created only with the 1 : 1 stoichiometry. Abundances of the 1 : 1 ions depend on the source of iron [(II) or (III)] and the reduction process of iron(III) by higher cone- voltage values. A counter-ion for the iron cation does not affect the types of formed complexes. For comparison, methanol solutions of acetylacetone (acac) and mixtures of acac and curcumin with iron salts were also investigated.

Deciphering the roles of the constitutive androstane receptor in energy metabolism

The constitutive androstane receptor (CAR) is initially defined as a xenobiotic nuclear receptor that protects the liver from injury. Detoxification of damaging chemicals is achieved by CAR-mediated induction of drug-metabolizing enzymes and transporters. More recent research has implicated CAR in energy metabolism, suggesting a therapeutic potential for CAR in metabolic diseases, such as type 2 diabetes and obesity. A better understanding of the mechanisms by which CAR regulates energy metabolism will allow us to take advantage of its effectiveness while avoiding its side effects. This review summarizes the current progress on the regulation of CAR nuclear translocation, upstream modulators of CAR activity, and the crosstalk between CAR and other transcriptional factors, with the aim of elucidating how CAR regulates glucose and lipid metabolism.

Small molecule adenosine 5'-monophosphate activated protein kinase (AMPK) modulators and human diseases

Adenosine 5'-monophosphate activated protein kinase (AMPK) is a master sensor of cellular energy status that plays a key role in the regulation of whole-body energy homeostasis. AMPK is a serine/threonine kinase that is activated by upstream kinases LKB1, CaMKKβ, and Tak1, among others. AMPK exists as αβγ trimeric complexes that are allosterically regulated by AMP, ADP, and ATP. Dysregulation of AMPK has been implicated in a number of metabolic diseases including type 2 diabetes mellitus and obesity. Recent studies have associated roles of AMPK with the development of cancer and neurological disorders, making it a potential therapeutic target to treat human diseases. This review focuses on the structure and function of AMPK, its role in human diseases, and its direct substrates and provides a brief synopsis of key AMPK modulators and their relevance in human diseases.

Demethoxycurcumin inhibits energy metabolic and oncogenic signaling pathways through AMPK activation in triple-negative breast cancer cells

Demethoxycurcumin (DMC), curcumin (Cur), and bisdemethoxycurcumin (BDMC) are major forms of curcuminoids found in the rhizomes of turmeric. This study examined the effects of three curcuminoid analogues on breast cancer cells. The results revealed that DMC demonstrated the most potent cytotoxic effects on breast cancer MDA-MB-231 cells. Compared with estrogen receptor (ER)-positive or HER2-overexpressing breast cancer cells, DMC demonstrated the most efficient cytotoxic effects on triple-negative breast cancer (TNBC) cells. However, nonmalignant MCF-10A cells were unaffected by DMC treatment. The study showed that DMC activated AMPK in TNBC cells. Once activated, AMPK inhibited eukaryotic initiation factor 4E-binding protein-1 (4E-BP1) signaling and mRNA translation via mammalian target of rapamycin (mTOR) and decreased the activity and/or expression of lipogenic enzymes, such as fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACC). DMC also targeted multiple AMPK downstream pathways. Among these, the dephosphorylation of Akt is noteworthy because it circumvents the feedback activation of Akt that results from mTOR inhibition. Moreover, DMC suppressed LPS-induced IL-6 production, thereby blocking subsequent Stat3 activation. In addition, DMC also sustained epidermal growth factor receptor (EGFR) activation by suppressing the phosphatases, PP2a and SHP-2. These results suggest that DMC is a potent AMPK activator that acts through a broad spectrum of anti-TNBC activities.

Natural compounds as regulators of the cancer cell metabolism

Even though altered metabolism is an "old" physiological mechanism, only recently its targeting became a therapeutically interesting strategy and by now it is considered an emerging hallmark of cancer. Nevertheless, a very poor number of compounds are under investigation as potential modulators of cell metabolism. Candidate agents should display selectivity of action towards cancer cells without side effects. This ideal favorable profile would perfectly overlap the requisites of new anticancer therapies and chemopreventive strategies as well. Nature represents a still largely unexplored source of bioactive molecules with a therapeutic potential. Many of these compounds have already been characterized for their multiple anticancer activities. Many of them are absorbed with the diet and therefore possess a known profile in terms of tolerability and bioavailability compared to newly synthetized chemical compounds. The discovery of important cross-talks between mediators of the most therapeutically targeted aberrancies in cancer (i.e., cell proliferation, survival, and migration) and the metabolic machinery allows to predict the possibility that many anticancer activities ascribed to a number of natural compounds may be due, in part, to their ability of modulating metabolic pathways. In this review, we attempt an overview of what is currently known about the potential of natural compounds as modulators of cancer cell metabolism.

Cytotoxic effects of curcumin in human retinal pigment epithelial cells

BACKGROUND

Curcumin from turmeric is an ingredient in curry powders. Due to its antiinflammatory, antioxidant and anticarcinogenic effects, curcumin is a promising drug for the treatment of cancer and retinal diseases. We investigated whether curcumin alters the viability and physiological properties of human retinal pigment epithelial (RPE) cells in vitro.

METHODOLOGY/PRINCIPAL FINDINGS

Cellular proliferation was investigated with a bromodeoxy-uridine immunoassay, and chemotaxis was investigated with a Boyden chamber assay. Cell viability was determined by trypan blue exclusion. Apoptosis and necrosis rates were determined with a DNA fragmentation ELISA. Gene expression was determined by real-time PCR, and secretion of VEGF and bFGF was examined with ELISA. The phosphorylation level of proteins was revealed by Western blotting. The proliferation of RPE cells was slightly increased by curcumin at 10 µM and strongly reduced by curcumin above 50 µM. Curcumin at 50 µM increased slightly the chemotaxis of the cells. Curcumin reduced the expression and secretion of VEGF under control conditions and abolished the VEGF secretion induced by PDGF and chemical hypoxia. Whereas low concentrations of curcumin stimulated the expression of bFGF and HGF, high concentrations caused downregulation of both factors. Curcumin decreased dose-dependently the viability of RPE cells via induction of early necrosis (above 10 µM) and delayed apoptosis (above 1 µM). The cytotoxic effect of curcumin involved activation of caspase-3 and calpain, intracellular calcium signaling, mitochondrial permeability, oxidative stress, increased phosphorylation of p38 MAPK and decreased phosphorylation of Akt protein.

CONCLUSION

It is concluded that curcumin at concentrations described to be effective in the treatment of tumor cells and in inhibiting death of retinal neurons (∼10 µM) has adverse effects on RPE cells. It is suggested that, during the intake of curcumin as concomitant therapy of cancer or in the treatment of eye diseases, retinal function should be monitored carefully.