Plants vs. cancer: a review on natural phytochemicals in preventing and treating cancers and their druggability

Appraisals of Bangladeshi Medicinal Plants Used by Folk Medicine Practitioners in the Prevention and Management of Malignant Neoplastic Diseases

Cancer is a group of diseases which is categorized to differentiate into diverse cell types and move around in the body to sites of organogenesis that is key to the process of tumor genesis. All types of cancer fall into the group of malignant neoplastic diseases. In Bangladesh, cancer is now one of the foremost killer diseases and its personal, social, and economic bearing are huge. Plant-derived natural compounds (vincristine, vinblastine, etoposide, paclitaxel, camptothecin, topotecan, and irinotecan) are useful for the treatment of cancer. Since there is no extensive ethnobotanical research study in Bangladesh regarding the traditional uses of medicinal plants against neoplasms, therefore, a randomized ethnopharmacological surveys were carried out in 3 districts of Bangladesh to learn more about the usage of anticancer medicinal plants and their chemical constituents having antineoplastic activity. Comprehensive interviews were conducted to the folk medicine practitioners and medicinal plants as pointed out by them were photographed, collected, deposited, and identified at the Bangladesh National Herbarium. The various plant parts have been used by the healers which included whole plant, leaves, fruits, barks, roots, and seeds. This study evaluated considerable potential for discovery of novel compounds with less side effects in the management and prevention of malignancy in cancer.

Recent trends in nano-based drug delivery systems for efficient delivery of phytochemicals in chemotherapy

The phytochemicals were found to become more soluble when delivered by the nanocarriers and exhibited a remarkable effect on the cancer cells compared to its free form.

Tangeretin derivative, 5-acetyloxy-6,7,8,4'-tetramethoxyflavone induces G2/M arrest, apoptosis and autophagy in human non-small cell lung cancer cells in vitro and in vivo

Tangeretin, a major phytochemicals in tangerine peels--an important Chinese herb, has been found to have anti-carcinogenic properties. To improve bioavailability and increase potency of tangeretin, its derivative, 5-acetyloxy-6,7,8,4'-tetramethoxyflavone (5-AcTMF), has been synthesized and shown potent inhibition of proliferation activity against human breast and leukemia cancer cell lines. In this study, we have further investigated the anticancer effects of 5-AcTMF on CL1-5 non-small cell lung cancer cells (NSCLC) both in vitro and in vivo and demonstrated that 5-AcTMF effectively inhibited cancer cell proliferation, induced G2/M-phase arrest associated with cdc2 and CDC25c and increased in the apoptotic cells associated with caspase activation, down regulation of Bcl-2, XIAP and Survivn, inducing release of cytochrome c into the cytosol and disruption of mitochondrial membrane potential. We also found that 5-AcTMF treatment of CL1-5 activated autophagy, indicated by triggered autophagosome formation and increased LC3-II levels and formation of LC3 puncta. Moreover, we also found that 5-AcTMF lowered phophoatidylinositol 3-kinase/AKT/mTOR signaling pathway. Over-expression of AKT by AKT cDNA transfection decreased 5-AcTMF mediated apoptosis and autophagy, supporting the induction of apoptosis and autophagy by inhibition of AKT pathway. In an animal study, 5-AcTMF effectively delayed tumor growth in a nude mouse model of CL1-5 xenografts without observed adverse effect. Immunohistochemistry Analysis indicated that 5-AcTMF induced CL1-5 cell apoptosis and autophagy in vivo. Taken together, these data demonstrate that 5-AcTMF is a novel small molecule agent that can inhibit NSCLC cell proliferation, and induce G(2)/M phase arrest and via the mitochondrial apoptotic pathway and autophagy.

Antimutagenicity and induction of antioxidant defense by flavonoid rich extract of Myrcia bella Cambess. in normal and tumor gastric cells

ETHNOPHARMACOLOGICAL RELEVANCE

The Brazilian "Cerrado" is an important source of natural products, such as Myrcia bella Cambess (MB, also known as "mercurinho"). MB leaves are popularly used for the treatment of diabetes and gastrointestinal disorders; however, only its hypoglycemic activity has been experimentally described.

AIM OF THE STUDY

Because MB is used to treat gastrointestinal disorders, the present study characterized biological activities of hydroalcoholic MB extract in human normal and tumor gastric cells.

MATERIALS AND METHODS

Cytotoxic, antiproliferative, genotoxic and protective effects were evaluated, as well as the effects of the MB extract on gene expression.

RESULTS

The MB extract induced cytotoxicity in tumor cells at lower concentrations compared with normal cells as assessed by the MTT assay. Moreover, the MB extract induced necrosis based on acridine orange/ethidium bromide staining. An antiproliferative effect was evidenced through an arrest in the G2/M phase detected by flow cytometry and a decrease in the nuclear division index using the cytokinesis-block micronucleus cytome assay. Cells treated with MB extract combined with doxorubicin (DXR) showed increased NUBDs, which may be related to the gene amplification of CCND1. Antimutagenic effects were also observed and may be associated with the antioxidant activities detected using the CM-H2DCFDA probe.

CONCLUSIONS

Our findings showed the following: (a) high concentrations of MB induced cytotoxicity and cell death by necrosis; (b) its antiproliferative effect was associated with G2/M arrest; and (c) its antioxidant activity could be responsible for the observed antimutagenic effects and for protective effects against gastrointestinal disorders previously described to MB. Although these effects are not specific to normal or tumor cells, they provide a panel of biological activities for further exploration.

Evaluation of cytotoxicity of aqueous extract of Graviola leaves on squamous cell carcinoma cell-25 cell lines by 3-(4,5-dimethylthiazol-2-Yl) -2,5-diphenyltetrazolium bromide assay and determination of percentage of cell inhibition at G2M phase of cell cycle by flow cytometry: An in vitro study

Introduction:

Malignancies constitute a wide variety of disorders having high mortality and morbidity rates. Current protocols for management include surgical intervention, chemotherapy, and radiation which possess numerous adverse effects. Many phytochemicals are available with anticancer properties similar to anticancer drugs. Major benefit of these compounds is apparent lack of toxicity to normal tissues. Graviola (botanical name: Annona Muricata) contain bioactive compound “annonaceous acetogenins” known for anticancer activity on cancer cell lines.

Aims:

To determine cytotoxicity of Graviola and percentage cell inhibition at G2M phase of cell cycle.

Settings and Design:

The cytotoxicity of aqueous extract of Graviola leaves on squamous cell carcinoma (SCC-25) cell lines at various concentrations evaluated using 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The percentage of SCC-25 cell inhibition at G2M phase of cell cycle determined using flow cytometry.

Methods:

Graviola Leaves, American Type Culture Collection SCC-25 cell lines were procured from Skanda Laboratories, Bengaluru. The cytotoxicity of aqueous extract of Graviola on SCC-25 cells at various concentrations evaluated using MTT assay. The percentage of SCC-25 cell inhibition at G2M phase of cell cycle determined using flow cytometry.

Statistical Analysis:

Statistical analysis was done using one-way ANOVA.

Results:

MTT assay showed statistically significant (P < 0.001) dose-dependent inhibition of SCC-25 cell lines by Graviola with IC50 value of 12.42 μg/ml. Flow cytometry revealed that Graviola at 25 and 50 g/ml arrested 53.39% and 52.09% cells in G2M phase of cell cycle respectively, which was statistically significant.

Conclusion:

Graviola showed significant cytotoxic activity and percentage of cell inhibition at G2M phase cell cycle against SCC-25 cell lines.

Investigation of Antioxidative and Anticancer Potentials of Streptomyces sp. MUM256 Isolated from Malaysia Mangrove Soil

A Streptomyces strain, MUM256 was isolated from Tanjung Lumpur mangrove soil in Malaysia. Characterization of the strain showed that it has properties consistent with those of the members of the genus Streptomyces. In order to explore the potential bioactivities, extract of the fermented broth culture of MUM256 was prepared with organic solvent extraction method. DPPH and SOD activity were utilized to examine the antioxidant capacity and the results have revealed the potency of MUM256 in superoxide anion scavenging activity in dose-dependent manner. The cytotoxicity of MUM256 extract was determined using cell viability assay against 8 different panels of human cancer cell lines. Among all the tested cancer cells, HCT116 was the most sensitive toward the extract treatment. At the highest concentration of tested extract, the result showed 2.3-, 2.0-, and 1.8-folds higher inhibitory effect against HCT116, HT29, and Caco-2 respectively when compared to normal cell line. This result has demonstrated that MUM256 extract was selectively cytotoxic toward colon cancer cell lines. In order to determine the constituents responsible for its bioactivities, the extract was then subjected to chemical analysis using GC-MS. The analysis resulted in the identification of chemical constituents including phenolic and pyrrolopyrazine compounds which may responsible for antioxidant and anticancer activities observed. Based on the findings of this study, the presence of bioactive constituents in MUM256 extract could be a potential source for the development of antioxidative and chemopreventive agents.

Chemical and biological characterisation of Machaerium hirtum (Vell.) Stellfeld: absence of cytotoxicity and mutagenicity and possible chemopreventive potential

Machaerium hirtum (Vell.) Stellfeld (M.hirtum) is a plant known as 'jacarandá-bico-de-pato' whose bark is commonly used against diarrhea, cough and cancer. The aim of this study was to phytochemically characterise the hydroethanolic extract of this plant, investigate its antimutagenic activities using the Ames test and evaluate its effects on cell viability, genomic instability, gene expression and cell protection in human hepatocellular carcinoma cells (HepG2). Antimutagenic activity was assessed by simultaneous pre- and post-treatment with direct and indirect mutagens, such as 4-nitro-o-phenylenediamine (NPD), mitomycin C (MMC), benzo[a]pyrene (B[a]P) and aflatoxin B1 (AFB1), using the Ames test, cytokinesis blocking micronucleus and apoptosis assays. Only 3 of the 10 concentrations evaluated in the MTT assay were cytotoxic in HepG2 cells. Micronucleated or apoptotic cells were not observed with any of the tested concentrations, and there were no mutagenic effects in the bacterial system. However, the Nuclear Division Index and flow cytometry data showed a decrease in cell proliferation. The extract showed an inhibitory effect against direct (NPD) and indirect mutagens (B[a]P and AFB1). Furthermore, pre- and post-treated cells showed significant reduction in the number of apoptotic and micronucleated cells. This effect is not likely to be associated with the modulation of antioxidant genes, as shown by the RT-qPCR results. Six known flavonoids were identified in the hydroethanolic extract of Machaerium hirtum leaves, and their structures were elucidated by spectroscopic and spectrophotometric methods. The presence of the antioxidants apigenin and luteolin may explain these protective effects, because these components can inhibit the formation of reactive species and prevent apoptosis and DNA damage. In conclusion, the M.hirtum extract showed chemopreventive potential and was not hazardous at the tested concentrations in the experiments presented here. Moreover, this extract should be investigated further as a chemopreventive agent.

Phytometabolite Dehydroleucodine Induces Cell Cycle Arrest, Apoptosis, and DNA Damage in Human Astrocytoma Cells through p73/p53 Regulation

Accumulating evidence supports the idea that secondary metabolites obtained from medicinal plants (phytometabolites) may be important contributors in the development of new chemotherapeutic agents to reduce the occurrence or recurrence of cancer. Our study focused on Dehydroleucodine (DhL), a sesquiterpene found in the provinces of Loja and Zamora-Chinchipe. In this study, we showed that DhL displayed cytostatic and cytotoxic activities on the human cerebral astrocytoma D384 cell line. With lactone isolated from Gynoxys verrucosa Wedd, a medicinal plant from Ecuador, we found that DhL induced cell death in D384 cells by triggering cell cycle arrest and inducing apoptosis and DNA damage. We further found that the cell death resulted in the increased expression of CDKN1A and BAX proteins. A marked induction of the levels of total TP73 and phosphorylated TP53, TP73, and γ-H2AX proteins was observed in D384 cells exposed to DhL, but no increase in total TP53 levels was detected. Overall these studies demonstrated the marked effect of DhL on the diminished survival of human astrocytoma cells through the induced expression of TP73 and phosphorylation of TP73 and TP53, suggesting their key roles in the tumor cell response to DhL treatment.

Organotypic culture of breast tumor explants as a multicellular system for the screening of natural compounds with antineoplastic potential

Breast cancer is the leading cause of death in women worldwide. The search for novel compounds with antitumor activity, with less adverse effects and higher efficacy, and the development of methods to evaluate their toxicity is an area of intense research. In this study we implemented the preparation and culture of breast tumor explants, which were obtained from precision-cut breast tumor slices. In order to validate the model we are proposing to screen antineoplastic effect of natural compounds, we selected caffeic acid, ursolic acid, and rosmarinic acid. Using the Krumdieck tissue slicer, precision-cut tissue slices were prepared from breast cancer samples; from these slices, 4 mm explants were obtained and incubated with the selected compounds. Viability was assessed by Alamar Blue assay, LDH release, and histopathological criteria. Results showed that the viability of the explants cultured in the presence of paclitaxel (positive control) decreased significantly (P < 0.05); however, tumor samples responded differently to each compound. When the explants were coincubated with paclitaxel and compounds, a synergic effect was observed. This study shows that ex vivo culture of breast cancer explants offers a suitable alternative model for evaluating natural or synthetic compounds with antitumor properties within the complex microenvironment of the tumor.

Capsaicin induces apoptosis in human small cell lung cancer via the TRPV6 receptor and the calpain pathway

Capsaicin, the pungent ingredient of chili peppers, displays potent anti-neoplastic activity in a wide array of human cancer cells. The present manuscript examines the signaling pathways underlying the apoptotic activity of capsaicin in human small cell lung cancer (SCLC) in vitro and in vivo. Studies in neuronal cells show that capsaicin exerts its biological activity via the transient receptor potential vanilloid (TRPV) superfamily of cation-channel receptors. The TRPV family is comprised of six members (TRPV1-6). Capsaicin is a known agonist of the TRPV1 receptor. We observed that capsaicin-induced apoptosis in human SCLC cells was mediated via the TRPV receptor family; however it was independent of TRPV1. Surprisingly, the apoptotic activity of capsaicin required the TRPV6 receptor. Depletion of TRPV6 receptor by siRNA methodology abolished the apoptotic activity of capsaicin in SCLC cells. Immunostaining and ELISA showed that TRPV6 receptor was robustly expressed on human SCLC tissues (from patients) and SCLC cell lines but almost absent in normal lung tissues. This correlates with our results that capsaicin induced very little apoptosis in normal lung epithelial cells. The pro-apoptotic activity of capsaicin was mediated by the intracellular calcium and calpain pathway. The treatment of human SCLC cells with capsaicin increased the activity of calpain 1 and 2 by threefold relative to untreated SCLC cells. Such calpain activation, in response to capsaicin, was downstream of the TRPV6 receptor. Taken together, our data provide insights into the mechanism underlying the apoptotic activity of capsaicin in human SCLCs.

Dietary Glucosinolates Sulforaphane, Phenethyl Isothiocyanate, Indole-3-Carbinol/3,3'-Diindolylmethane: Anti-Oxidative Stress/Inflammation, Nrf2, Epigenetics/Epigenomics and In Vivo Cancer Chemopreventive Efficacy

Glucosinolates are a group of sulfur-containing glycosides found in many plant species, including cruciferous vegetables such as broccoli, cabbage, brussels sprouts, and cauliflower. Accumulating evidence increasingly supports the beneficial effects of dietary glucosinolates on overall health, including as potential anti-cancer agents, because of their role in the prevention of the initiation of carcinogenesis via the induction of cellular defense detoxifying/antioxidant enzymes and their epigenetic mechanisms, including modification of the CpG methylation of cancer-related genes, histone modification regulation and changes in the expression of miRNAs. In this context, the defense mechanism mediated by Nrf2-antioxidative stress and anti-inflammatory signaling pathways can contribute to cellular protection against oxidative stress and reactive metabolites of carcinogens. In this review, we summarize the cancer chemopreventive role of naturally occurring glucosinolate derivatives as inhibitors of carcinogenesis, with particular emphasis on specific molecular targets and epigenetic alterations in in vitro and in vivo human cancer animal models.

Silymarin induces cyclin D1 proteasomal degradation via its phosphorylation of threonine-286 in human colorectal cancer cells

Silymarin from milk thistle (Silybum marianum) plant has been reported to show anti-cancer, anti-inflammatory, antioxidant and hepatoprotective effects. For anti-cancer activity, silymarin is known to regulate cell cycle progression through cyclin D1 downregulation. However, the mechanism of silymarin-mediated cyclin D1 downregulation still remains unanswered. The current study was performed to elucidate the molecular mechanism of cyclin D1 downregulation by silymarin in human colorectal cancer cells. The treatment of silymarin suppressed the cell proliferation in HCT116 and SW480 cells and decreased cellular accumulation of exogenously-induced cyclin D1 protein. However, silymarin did not change the level of cyclin D1 mRNA. Inhibition of proteasomal degradation by MG132 attenuated silymarin-mediated cyclin D1 downregulation and the half-life of cyclin D1 was decreased in the cells treated with silymarin. In addition, silymarin increased phosphorylation of cyclin D1 at threonine-286 and a point mutation of threonine-286 to alanine attenuated silymarin-mediated cyclin D1 downregulation. Inhibition of NF-κB by a selective inhibitor, BAY 11-7082 suppressed cyclin D1 phosphorylation and downregulation by silymarin. From these results, we suggest that silymarin-mediated cyclin D1 downregulation may result from proteasomal degradation through its threonine-286 phosphorylation via NF-κB activation. The current study provides new mechanistic link between silymarin, cyclin D1 downregulation and cell growth in human colorectal cancer cells.

Metabolome-genome-wide association study dissects genetic architecture for generating natural variation in rice secondary metabolism

Plants produce structurally diverse secondary (specialized) metabolites to increase their fitness for survival under adverse environments. Several bioactive compounds for new drugs have been identified through screening of plant extracts. In this study, genome-wide association studies (GWAS) were conducted to investigate the genetic architecture behind the natural variation of rice secondary metabolites. GWAS using the metabolome data of 175 rice accessions successfully identified 323 associations among 143 single nucleotide polymorphisms (SNPs) and 89 metabolites. The data analysis highlighted that levels of many metabolites are tightly associated with a small number of strong quantitative trait loci (QTLs). The tight association may be a mechanism generating strains with distinct metabolic composition through the crossing of two different strains. The results indicate that one plant species produces more diverse phytochemicals than previously expected, and plants still contain many useful compounds for human applications.

Anti-cancer activity of Ginger (Zingiber officinale) leaf through the expression of activating transcription factor 3 in human colorectal cancer cells

BACKGROUND

Ginger leaf (GL) has long been used as a vegetable, tea and herbal medicine. However, its pharmacological properties are still poorly understood. Thus, we performed in vitro studies to evaluate anti-cancer properties of ginger leaf and then elucidate the potential mechanisms involved.

METHODS

Cell viability was measured by MTT assay. ATF3 expression level was evaluated by Western blot or RT-PCR and ATF3 transcriptional activity was determined using a dual-luciferase assay kit after the transfection of ATF3 promoter constructs. In addition, ATF3-dependent apoptosis was evaluated by Western blot after ATF3 knockdown using ATF3 siRNA.

RESULTS

Exposure of GL to human colorectal cancer cells (HCT116, SW480 and LoVo cells) reduced the cell viability and induced apoptosis in a dose-dependent manner. In addition, GL reduced cell viability in MCF-7, MDA-MB-231 and HepG-2 cells. ATF3 knockdown attenuated GL-mediated apoptosis. GL increased activating transcription factor 3 (ATF3) expressions in both protein and mRNA level and activated ATF3 promoter activity, indicating transcriptional activation of ATF3 gene by GL. In addition, our data showed that GL-responsible sites might be between -318 and -85 region of the ATF3 promoter. We also observed that ERK1/2 inhibition by PD98059 attenuated GL-mediated ATF3 expression but not p38 inhibition by SB203580, indicating ERK1/2 pathway implicated in GL-induced ATF3 activation.

CONCLUSIONS

These findings suggest that the reduction of cell viability and apoptosis by GL may be a result of ATF3 promoter activation and subsequent increase of ATF3 expression through ERK1/2 activation in human colorectal cancer cells.

The contribution of activating transcription factor 3 to apoptosis of human colorectal cancer cells by protocatechualdehyde, a naturally occurring phenolic compound

Protocatechualdehyde (PCA) is one of the important compounds found in barley, green cavendish bananas and grapevine leaves. PCA shows anti-cancer activities in breast, leukemia and colorectal cancer cells. Previous study reported that PCA exerts anti-cancer activity through down-regulating cyclin D1 and HDAC2 in human colorectal cancer cells. However, the underlying mechanisms for the expression of activating transcription factor 3 (ATF3) by PCA has not been studied. Thus, we performed in vitro study to investigate if treatment of PCA affects ATF3 expression and ATF3-mediated apoptosis in human colorectal cancer cells. PCA decreased cell viability in a dose-dependent manner in HCT116 and SW480 cells. In addition, PCA reduced cell viability in MCF-7, MDA-MB-231 and HepG-2 cells. Exposure of PCA activated the levels of ATF3 protein and mRNA in HCT116 and SW480 cells. Inhibition of ERK1/2/ by PD98059 and p38 by SB203580 inhibited PCA-induced ATF3 expression and transcriptional activation. ATF3-knockdown inhibited PCA-induced apoptosis and cell viability. In addition, ATF3 overexpression enhanced PCA-mediated cleavage of PARP. These findings suggest that inhibition of cell viability and apoptosis by PCA may be result of ATF3 expression through ERK1/2 and p38-mediated transcriptional activation.

Cancer chemoprevention by traditional chinese herbal medicine and dietary phytochemicals: targeting nrf2-mediated oxidative stress/anti-inflammatory responses, epigenetics, and cancer stem cells

Excessive oxidative stress induced by reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive metabolites of carcinogens alters cellular homeostasis, leading to genetic/epigenetic changes, genomic instability, neoplastic transformation, and cancer initiation/progression. As a protective mechanism against oxidative stress, antioxidant/detoxifying enzymes reduce these reactive species and protect normal cells from endo-/exogenous oxidative damage. The transcription factor nuclear factor-erythroid 2 p45 (NF-E2)-related factor 2 (Nrf2), a master regulator of the antioxidative stress response, plays a critical role in the expression of many cytoprotective enzymes, including NAD(P)H:quinine oxidoreductase (NQO1), heme oxygenase-1 (HO-1), UDP-glucuronosyltransferase (UGT), and glutathione S-transferase (GST). Recent studies demonstrated that many dietary phytochemicals derived from various vegetables, fruits, spices, and herbal medicines induce Nrf2-mediated antioxidant/detoxifying enzymes, restore aberrant epigenetic alterations, and eliminate cancer stem cells (CSCs). The Nrf2-mediated antioxidant response prevents many age-related diseases, including cancer. Owing to their fundamental contribution to carcinogenesis, epigenetic modifications and CSCs are novel targets of dietary phytochemicals and traditional Chinese herbal medicine (TCHM). In this review, we summarize cancer chemoprevention by dietary phytochemicals, including TCHM, which have great potential as a safer and more effective strategy for preventing cancer.

Mechanistic perspectives on cancer chemoprevention/chemotherapeutic effects of thymoquinone

The bioactive natural products (plant secondary metabolites) are widely known to possess therapeutic value for the prevention and treatment of various chronic diseases including cancer. Thymoquinone (2-methyl-5-isopropyl-1,4-benzoquinone; TQ), a monoterpene present in black cumin seeds, exhibits pleiotropic pharmacological activities including antioxidant, anti-inflammatory, antidiabetic and antitumor effects. TQ inhibits experimental carcinogenesis in a wide range of animal models and has been shown to arrest the growth of various cancer cells in culture as well as xenograft tumors in vivo. The mechanistic basis of anticancer effects of TQ includes the inhibition of carcinogen metabolizing enzyme activity and oxidative damage of cellular macromolecules, attenuation of inflammation, induction of cell cycle arrest and apoptosis in tumor cells, blockade of tumor angiogenesis, and suppression of migration, invasion and metastasis of cancer cells. TQ shows synergistic and/or potentiating anticancer effects when combined with clinically used chemotherapeutic agents. At the molecular level, TQ targets various components of intracellular signaling pathways, particularly a variety of upstream kinases and transcription factors, which are aberrantly activated during the course of tumorigenesis.

Methanolic extract of white asparagus shoots activates TRAIL apoptotic death pathway in human cancer cells and inhibits colon carcinogenesis in a preclinical model

Shoots of white asparagus are a popular vegetable dish, known to be rich in many bioactive phytochemicals reported to possess antioxidant, and anti-inflammatory and antitumor activities. We evaluated the anticancer mechanisms of a methanolic extract of Asparagus officinalis L. shoots (Asp) on human colon carcinoma cells (SW480) and their derived metastatic cells (SW620), and Asp chemopreventive properties were also assessed in a model of colon carcinogenesis. SW480 and SW620 cell proliferation was inhibited by 80% after exposure to Asp (80 µg/ml). We demonstrated that Asp induced cell death through the activation of TRAIL DR4/DR5 death receptors leading to the activation of caspase-8 and caspase-3 and to cell apoptosis. By specific blocking agents of DR4/DR5 receptors we were able to prevent Asp-triggered cell death confirming the key role of DR4/DR5 receptors. We found also that Asp (80 µg/ml) was able to potentiate the effects of the cytokine TRAIL on cell death even in the TRAIL-resistant metastatic SW620 cells. Colon carcinogenesis was initiated in Wistar rats by intraperitoneal injections of azoxymethane (AOM), once a week for two weeks. One week after (post-initiation) rats received daily Asp (0.01%, 14 mg/kg body weight) in drinking water. After 7 weeks of Asp-treatment the colon of rats exhibited a 50% reduction of the number of preneoplastic lesions (aberrant crypt foci). In addition Asp induced inhibition of several pro-inflammatory mediators, in association with an increased expression of host-defense mediators. In the colonic mucosa of Asp-treated rats we also confirmed the pro-apoptotic effects observed in vitro including the activation of the TRAIL death‑receptor signaling pathway. Taken together, our data highlight the chemopreventive effects of Asp on colon carcinogenesis and its ability to promote normal cellular homeostasis.

Protocatechualdehyde possesses anti-cancer activity through downregulating cyclin D1 and HDAC2 in human colorectal cancer cells

Protocatechualdehyde (PCA) is a naturally occurring polyphenol found in barley, green cavendish bananas, and grapevine leaves. Although a few studies reported growth-inhibitory activity of PCA in breast and leukemia cancer cells, the underlying mechanisms are still poorly understood. Thus, we performed in vitro study to investigate if treatment of PCA affects cell proliferation and apoptosis in human colorectal cancer cells and define potential mechanisms by which PCA mediates growth arrest and apoptosis of cancer cells. Exposure of PCA to human colorectal cancer cells (HCT116 and SW480 cells) suppressed cell growth and induced apoptosis in dose-dependent manner. PCA decreased cyclin D1 expression in protein and mRNA level and suppressed luciferase activity of cyclin D1 promoter, indicating transcriptional downregulation of cyclin D1 gene by PCA. We also observed that PCA treatment attenuated enzyme activity of histone deacetylase (HDAC) and reduced expression of HDAC2, but not HDAC1. These findings suggest that cell growth inhibition and apoptosis by PCA may be a result of HDAC2-mediated cyclin D1 suppression.