Digalloylresveratrol, a new phenolic acid derivative induces apoptosis and cell cycle arrest in human HT-29 colon cancer cells

A novel EGFR inhibitor, HNPMI, regulates apoptosis and oncogenesis by modulating BCL-2/BAX and p53 in colon cancer

BACKGROUND AND PURPOSE

Colorectal cancer (CRC) is the second most lethal disease, with high mortality due to its heterogeneity and chemo-resistance. Here, we have focused on the epidermal growth factor receptor (EGFR) as an effective therapeutic target in CRC and studied the effects of polyphenols known to modulate several key signalling mechanisms including EGFR signalling, associated with anti-proliferative and anti-metastatic properties.

EXPERIMENTAL APPROACH

Using ligand- and structure-based cheminformatics, we developed three potent, selective alkylaminophenols, 2-[(3,4-dihydroquinolin-1(2H)-yl)(p-tolyl)methyl]phenol (THTMP), 2-[(1,2,3,4-tetrahydroquinolin-1-yl)(4-methoxyphenyl)methyl]phenol (THMPP) and N-[2-hydroxy-5-nitrophenyl(4'-methylphenyl)methyl]indoline (HNPMI). These alkylaminophenols were assessed for EGFR interaction, EGFR-pathway modulation, cytotoxic and apoptosis induction, caspase activation and transcriptional and translational regulation. The lead compound HNPMI was evaluated in mice bearing xenografts of CRC cells.

KEY RESULTS

Of the three alkylaminophenols tested, HNPMI exhibited the lowest IC50 in CRC cells and potential cytotoxic effects on other tumour cells. Modulation of EGFR pathway down-regulated protein levels of osteopontin, survivin and cathepsin S, leading to apoptosis. Cell cycle analysis revealed that HNPMI induced G0/G1 phase arrest in CRC cells. HNPMI altered the mRNA for and protein levels of several apoptosis-related proteins including caspase 3, BCL-2 and p53. HNPMI down-regulated the proteins crucial to oncogenesis in CRC cells. Assays in mice bearing CRC xenografts showed that HNPMI reduced the relative tumour volume.

CONCLUSIONS AND IMPLICATIONS

HNPMI is a promising EGFR inhibitor for clinical translation. HNPMI regulated apoptosis and oncogenesis by modulating BCL-2/BAX and p53 in CRC cell lines, showing potential as a therapeutic agent in the treatment of CRC.

Gallic acid in theabrownin suppresses cell proliferation and migration in non‑small cell lung carcinoma via autophagy inhibition

The bioactive extract of green tea, theabrownin (TB), is known to exhibit pro-apoptotic and antitumor effects on non-small cell lung cancer (NSCLC). Gallic acid (GA) is a crucial component of TB; however, its mechanism of action in NSCLC has been rarely studied. To date, little attention has been paid to the anti-NSCLC activity of GA. Therefore, the present study investigated the effects of GA in vivo and in vitro. Cell Counting Kit (CCK)-8 assay, DAPI staining and flow cytometry, wound-healing assay and western blotting were used to assess cell viability, apoptosis, migration and protein expression, respectively. In addition, a xenograft model was generated, and TUNEL assay and immunohistochemistry analysis were performed. The CCK-8 data showed that the viability of H1299 cells was significantly inhibited by GA in a dose- and time-dependent manner. DAPI staining, Annexin-V/PI staining and wound-healing data showed that GA exerted pro-apoptotic and anti-migratory effects on H1299 cells in a dose-dependent manner. Furthermore, the results of western blotting showed that GA significantly upregulated the levels of pro-apoptotic proteins [cleaved (c-)PARP, c-caspase8, c-caspase-9 and the ratio of γ-H2A.X/H2A.X]. In vivo data confirmed the antitumor effect of GA through apoptosis induction in an autophagy-dependent manner. In conclusion, the present study confirmed the anti-proliferative, pro-apoptotic and anti-migratory effects of GA against NSCLC in vitro and in vivo, providing considerable evidence for its potential as a novel candidate for the treatment of NSCLC.

Extraction, phytochemical characterization and anti-cancer mechanism of Haritaki churna: An ayurvedic formulation

Haritaki churna (HC), a single herb ayurvedic formulations is known to be prescribed for various gastro-intestinal disorders in Ayurveda. Haritaki churna aqueous extract (HCAE) has anti-cancer activity against different types of cancer cells with an IC50 in the range of 50-97 μg/ml. Bioavailability of Haritaki Churna is very high in digestive track and treatment of colorectal cancer cells HCT-116, DLD1, HT-29 with HCAE reduces its cellular viability with anti-cancer IC50 70μg/ml. HCAE consumption is safe for human as it didn't affect the cellular viability of primary human PBMCs or non-cancerogenic HEK-293 cells. Haritaki churna was found to be stable in biological gastric fluids and bioactive agents are not losing their anti-cancer activity under such harsh conditions. The HPLC Chromatogram of HCAE is giving 13 major peaks and 11 minor peaks. Exploiting LC-MS, IR and NMR spectroscopic techniques, a total of 13 compounds were identified from HCAE namely Shikimic acid, Chebulic acid, gallic acid, 5-hydroxymethylfurfural, Protocatechuic acid, 4-O-galloyl-shikimic Acid, 5-O-galloyl-shikimic Acid, Methylgallate, corilagin, 1, 2, 6, Tri-O-galloyl β-D-glucose, chebulagic acid, chebulinic acid, and Ellagic acid. Reconstitution and subtraction of phytochemicals from the mixture indicate that Ellagic acid significantly contribute into anti-cancer effect of HCAE. Cancer cells treated with ellagic acid from HCAE were incapable of completing their cell-cycle and halted the cell-cycle at DNA synthesis S-Phase, as demonstrated by decreased cyclin A2 expression levels with increasing ellagic acid concentration. Halting of cells at S-phase causes induction of apoptosis in cancer cells. Cancer cells exhibiting DNA fragmentation, changes in expression of several apoptotic proteins such as Bcl2, cytochrome-c and formation of cleaved products of caspase 3 and PARP-1 suggests ellagic acid induces cell death via mitochondrial pathway of apoptosis.

Applications of resveratrol in the treatment of gastrointestinal cancer

Natural product compounds have lately attracted interest in the scientific community as a possible treatment for gastrointestinal (GI) cancer, due to their anti-inflammatory and anticancer properties. There are many preclinical, clinical, and epidemiological studies, suggesting that the consumption of polyphenol compounds, which are abundant in vegetables, grains, fruits, and pulses, may help to prevent various illnesses and disorders from developing, including several GI cancers. The development of GI malignancies follows a well-known path, in which normal gastrointestinal cells acquire abnormalities in their genetic composition, causing the cells to continuously proliferate, and metastasize to other sites, especially the brain and liver. Natural compounds with the ability to affect oncogenic pathways might be possible treatments for GI malignancies, and could easily be tested in clinical trials. Resveratrol is a non-flavonoid polyphenol and a natural stilbene, acting as a phytoestrogen with anti-cancer, cardioprotective, anti-oxidant, and anti-inflammatory properties. Resveratrol has been shown to overcome resistance mechanisms in cancer cells, and when combined with conventional anticancer drugs, could sensitize cancer cells to chemotherapy. Several new resveratrol analogs and nanostructured delivery vehicles with improved anti-GI cancer efficacy, absorption, and pharmacokinetic profiles have already been developed. This present review focuses on the in vitro and in vivo effects of resveratrol on GI cancers, as well as the underlying molecular mechanisms of action.

Extraction of phenolic compounds from the shells of pecan nuts with cytotoxic activity through apoptosis against the colon cancer cell line HT-29

The water extraction of phenolic compounds from two varieties ("Mahan" and "Marameck") of pecan nutshells (Carya illinoinensis) without and with sonication, varying the solvent/solid ratio (S), the pH, and the refluxing time (t), was studied. Additionally, the in vitro cytotoxicity and the determination of the cell death mechanism of the extracts against the colon cancer cell line HT-29 were investigated. The content of total phenolic compounds (TPC) of "Marameck" nutshells resulted higher than for the "Mahan" variety, and the pH increase resulted in higher TPC contents for both cultivars. The optimized conditions for TPC extraction without and with sonication resulted: S = 33 ml/g, pH = 12, and t = 9.6 min, and yielded ≈ 70 and 90 mg/g of TPC for "Mahan" and "Marameck" nutshells, respectively. The optimized extracts of pecan nutshells without sonication from both cultivars presented similar cytotoxicity against HT-29 colon cancer cells (IC₅₀  ≈ 50 µg/ml), higher than for sonicated extracts (IC₅₀ ≈ 88 and 138 µg/ml for "Mahan" and "Marameck," respectively). Cell death through apoptosis was the main mechanism of cell death induced by the nutshell extracts. PRACTICAL APPLICATION: The extraction of phenolic compounds (TPC) from the residues of two varieties of pecan nutshells ("Mahan" and "Marameck") was studied. An optimal combination of variables within the pH range that minimizes the solvent-to-solid ratio (S) and the time of refluxing (t), saving at the same time, water and energy, was set up. The phenolic compound extracts obtained from the residues of the pecan nuts exhibit cytotoxic effects against colon cancer cells and could be of interest as an alternative treatment of different types of cancer. Additionally, these extracts may be of importance to the food industry as they can be used as antioxidant agents in food formulation. Also, the high levels of anthocyanidins obtained from the pecan nut extracts after proanthocyanidins' strong acid hydrolysis can be purified and employed as natural red dyes.

Germacrone exerts anti-cancer effects on gastric cancer through induction of cell cycle arrest and promotion of apoptosis

Background

Germacrone is one of the natural bioactive compounds found in Rhizoma curcuma essential oils. In this study, the potential anti-cancer effect of germacrone in gastric cancer cell line BGC823 was investigated.

Methods

The cell viability and proliferative activity were assessed, and cell cycle analysis was also performed. Hoechst 33258 and Annexin V/PI double staining was used for detection of cell apoptosis. Protein profiles of cell cycle-related and apoptosis-related proteins were assessed.

Results

MTT assay revealed that germacrone had marked cytotoxicity on BGC823 cells. Germacrone induced cell cycle arrest in the G2/M phase via remarkably decreased expression levels of cyclin B1, cdc 2 and cdc 25c. In addition, the treatment with germacrone induced caspase-3 activity and PARP cleavage. These findings demonstrated the effects of germacrone on inhibiting cell proliferation through induction of G2/M phase cell cycle arrest and promotion of cell apoptosis. It also indicated that germacrone functioned through modulations of cell cycle-associated protein expression and mitochondria-mediated apoptosis.

Conclusion

These findings will be valuable as the molecular basis for the germacrone-mediated anti-cancer effect against gastric cancer.

Molecular modeling, simulation and principal component analysis of binding of resveratrol and its analogues with DNA

Structure-based drug designing has become a significant subject of research, and several clinically promising DNA binding compounds were evolved using this technique. The interaction of an octamer DNA sequence d(CCAATTGG)₂ with a natural stilbene, resveratrol and its analogues have been studied using molecular docking method. Out of the ten compounds studied, seven compounds were found to bind to the minor groove of AATT segment of the sequence. Pterostilbene, a natural analogue of resveratrol, showed the lowest binding energy. Rhaponticin, a natural analogue of resveratrol and digalloylresveratrol, a synthetic ester of resveratrol bind to the major groove of the AATT segment while dihydroresveratrol binds to the minor groove of GC terminal base pair. ADMET (Absorption, distribution, metabolism, excretion and toxicity) study showed that all compounds obey Lipinski rule and are accepted as orally active drugs based on different physicochemical descriptors. Molecular dynamics simulations were performed for the complex with lowest binding energy and trajectory analysis were performed. Principal component analysis has been performed to underline the prominent motions in alone DNA and when it is bound to pterostilbene. AbbreviationsADMETAbsorption, distribution, metabolism, excretion and toxicityDIGDigalloyl resveratrolDNADeoxyribonucleic acidELElectrostatic energyENPOLARNonpolar solvation energyESURFSurface areaGBGeneralized BornHBAHydrogen bond acceptorsHBDHydrogen bond donorsLGALamarckian genetic algorithmMDMolecular dynamicsPBPoisson-BoltzmannPCAPrincipal component analysisPTPterostilbeneRMSDRoot mean square deviationSASimulated annealingTLX3T-cell leukemia homeobox 3VDWvan der WaalsCommunicated by Ramaswamy H. Sarma.

Strategies to Improve Resveratrol Systemic and Topical Bioavailability: An Update

In recent years, a great deal of attention has been paid to natural compounds due to their many biological effects. Polyphenols are a class of plant derivatives that have been widely investigated for preventing and treating many oxidative stress-related pathological conditions, such as neurodegenerative and cardiovascular diseases, cancer, diabetes mellitus and inflammation. Among these polyphenols, resveratrol (RSV) has attracted considerable interest owing to its high antioxidant and free radical scavenging activities. However, the poor water solubility and rapid metabolism of RSV lead to low bioavailability, thus limiting its clinical efficacy. After discussing the main biochemical mechanisms involved in RSV biological activities, this review will focus on the strategies attempted to improve RSV effectiveness, both for systemic and for topical administration. In particular, technological approaches involving RSV incorporation into different delivery systems such as liposomes, polymeric and lipid nanoparticles, microemulsions and cyclodextrins will be illustrated, highlighting their potential clinical applications. In addition, chemical modifications of this antioxidant aimed at improving its physicochemical properties will be described along with the results of in vitro and in vivo studies.

Aqueous extract from pecan nut [Carya illinoinensis (Wangenh) C. Koch] shell show activity against breast cancer cell line MCF-7 and Ehrlich ascites tumor in Balb-C mice

ETHNOPHARMACOLOGICAL RELEVANCE

In Brazil many health disorders are treated with the consumption of different varieties of tea. Shell extracts of pecan nut (Carya illinoinensis), which have significant amounts of phenolic compounds in their composition, are popularly taken as tea to prevent diverse pathologies.

AIM OF THE STUDY

Phenolic compounds from pecan nut shell extract have been associated with diverse biological effects but the effect on tumor cells has not been reported yet. The aim of the current work was to evaluate the relationship between DNA fragmentation, cell cycle arrest and apoptosis induced by pecan nut shell extract and its antitumor activity.

MATERIALS AND METHODS

Cytotoxicity, proliferation, cell death and cell cycle were evaluated in MCF-7 cells by MTT, colony assay, differential coloring and flow cytometry assays, respectively. DNA damage effects were evaluated through intercalation into CT-DNA and plasmid DNA cleavage. Tumor growth inhibition, survival time increase, apoptosis and cell cycle arrest were assessed in Ehrlich ascites tumor in Balb/C mice.

RESULTS

The cytotoxic effect of pecan nut shell extracts, the induction of cell death by apoptosis and also the cell cycle arrest in MCF-7 cells have been demonstrated. The survival time in mice with Ehrlich ascites tumor increased by 67%. DNA damage was observed in the CT-DNA, plasmid DNA and comet assays. The mechanism involved in the antitumor effect of pecan nut shell extracts may be related to the activation of key proteins involved in apoptosis cell death (Bcl-XL, Bax and p53) and on the cell cycle regulation (cyclin A, cyclin B and CDK2).

CONCLUSIONS

These results were attributed to the phenolic profile of the extract, which presented compounds such as gallic, 4-hydroxybenzoic, chlorogenic, vanillic, caffeic and ellagic acid, and catechin, epicatechin, epigallocatechin and epicatechin gallate. The results indicated that pecan nut shell extracts are effective against tumor cells growth and may be considered as an alternative to the treatment of cancer.

Polyphenols in Colorectal Cancer: Current State of Knowledge including Clinical Trials and Molecular Mechanism of Action

Polyphenols have been reported to have wide spectrum of biological activities including major impact on initiation, promotion, and progression of cancer by modulating different signalling pathways. Colorectal cancer is the second most major cause of mortality and morbidity among females and the third among males. The objective of this review is to describe the activity of a variety of polyphenols in colorectal cancer in clinical trials, preclinical studies, and primary research. The molecular mechanisms of major polyphenols related to their beneficial effects on colorectal cancer are also addressed. Synthetic modifications and other future directions towards exploiting of natural polyphenols against colorectal cancer are discussed in the last section.

Solid lipid nanoparticles improve octyl gallate antimetastatic activity and ameliorate its renal and hepatic toxic effects

Metastasis is the main cause of cancer-related death and requires the development of effective treatments with reduced toxicity and effective anticancer activity. Gallic acid derivatives have shown significant biological properties including antitumoral activity as shown in a previous study with octyl gallate (G8) in vitro. Thus, the aim of this work was to evaluate the antimetastatic effect of free and solid lipid nanoparticle-loaded G8 in mice in a lung metastasis model. Animals inoculated with melanoma cells presented metastasis in lungs, which was significantly inhibited by treatment with G8 and solid lipid nanoparticle-loaded G8, named G8-NVM. However, G8-treated mice showed an increase in several toxicological parameters, which were almost completely circumvented by G8-NVM treatment. This study supports the need for pharmacological studies on new potential medicinal plants to treat cancer and can provide new perspectives on using nanotechnology to improve biological activities while decreasing the chemotherapy toxicological effects of anticancer drugs.

Thiosemicarbazone derivatives, thiazolyl hydrazones, effectively inhibit leukemic tumor cell growth: Down-regulation of ribonucleotide reductase activity and synergism with arabinofuranosylcytosine

Cellular growth inhibition exerted by thiosemicarbazones is mainly attributed to down-regulation of ribonucleotide reductase (RNR) activity, with RNR being responsible for the rate-limiting step of de novo DNA synthesis. In this study, we investigated the antineoplastic effects of three newly synthesized thiosemicarbazone derivatives, thiazolyl hydrazones, in human HL-60 promyelocytic leukemia cells. The cytotoxicity of compounds alone and in combination with arabinofuranosylcytosine (AraC) was determined by growth inhibition assays. Effects on deoxyribonucleoside triphosphate (dNTP) concentrations were quantified by HPLC, and the incorporation of radio-labeled ¹⁴C-cytidine into nascent DNA was measured using a beta counter. Cell cycle distribution was analyzed by FACS, and protein levels of RNR subunits and checkpoint kinases were evaluated by Western blotting. VG12, VG19, and VG22 dose-dependently decreased intracellular dNTP concentrations, impaired cell cycle progression and, consequently, inhibited the growth of HL-60 cells. VG19 also lowered the protein levels of RNR subunits R1 and R2 and significantly diminished the incorporation of radio-labeled ¹⁴C-cytidine, being equivalent to an inhibition of DNA synthesis. Combination of thiazolyl hydrazones with AraC synergistically potentiated the antiproliferative effects seen with each drug alone and might therefore improve conventional chemotherapeutic regimens for the treatment of human malignancies such as acute promyelocytic or chronic myelogenous leukemia.

Resveratrol derivatives as a pharmacological tool

Prodrugs of resveratrol are under development. Among the long-term goals, still largely elusive, are (1) modulating physical properties (e.g., water-soluble derivatives bearing polyethylene glycol chains), (2) changing distribution in the body (e.g., galactosyl derivatives restricted to the intestinal lumen), (3) increasing absorption from the gastrointestinal tract (e.g., derivatives imitating the natural substrates of endogenous transporters), and (4) hindering phase II metabolism (e.g., temporarily blocking the hydroxyls), all contributing to (5) increasing bioavailability. The chemical bonds that have been tested for functionalization include carboxyester, acetal, and carbamate groups. A second approach, which can be combined with the first, seeks to reinforce or modify the biochemical activities of resveratrol by concentrating the compound at specific subcellular sites. An example is provided by mitochondria-targeted derivatives. These proved to be pro-oxidant and cytotoxic in vitro, selectively killing fast-growing and tumor cells when supplied in the low micromolar range. This suggests the possibility of anticancer applications.

Enhancement of anticancer potential of polyphenols by covalent modifications

As evidenced by a growing number of respective clinical trials, a promising and increasingly valued approach to cancer prevention is chemoprevention which is based on using synthetic, semisynthetic, or natural compounds with the aim of preventing, delaying, arresting, or reversing carcinogenesis. Research carried out in the last two decades indicates that natural polyphenols isolated from plants (as well as their derivatives and synthetic analogs) exhibit pleiotropic actions toward cancer cells and therefore they could be used in both cancer prevention and therapy. This review discusses selected covalent modifications of polyphenols as a means for increasing their anticancer potential in relation to the parent compounds. The modifications include hydroxylation, methylation, acylation, and galloylation, among others. They were demonstrated to enhance cytotoxic, pro-oxidant, antiproliferative, proapoptotic, proautophagic, and antimigratory activities of phenolics toward various cancer cell lines in vitro. Importantly, some derivatives proved to suppress tumor growth and metastasis in animal models more strongly than the parent compounds. Some of the above-mentioned covalent modifications were also shown to increase absorption and tissue distribution of tested phenolic compounds in vivo. Anticancer clinical trials with polyphenol derivatives therefore seem warranted.

Design and synthesis of pyrrolobenzodiazepine-gallic hybrid agents as p53-dependent and -independent apoptogenic signaling in melanoma cells

A new class of pyrrolo[2,1-c][1,4]benzodiazepine-Gallic hybrid agents (PBD-GA) conjugated through alkyl spacers has been designed and synthesized. The combination of these two core pharmacophores with modification in the C-8 position of the PBD ring with alkyl spacers afforded oxygen-tethered compounds 5a-5d and amide-tethered analogues 11a-11d with improved anticancer activity for two melanoma cell lines, A375 and RPMI7951, differing in their p53 status. The agents 5a-5d were cytotoxic in melanoma compared to agents 11a-11d. In particular, compounds 5b and 5c were found to possess the most potent activity compared with other hybrid agents and were proved with the help of quantitative structure activity relationship studies (QSAR). These PBD conjugates caused S phase arrest for the A375 cell line via increased reactive oxygen species (ROS) generation, deoxyribonucleic acid (DNA) damage, ataxia telangiectasia mutated (ATM)/ATM-Rad3-related (ATR) and checkpoint kinases 1 (Chk1) activation. Moreover, the PBD-GA induced A375 apoptotic cell death followed through p53 (ATM downstream target) increase, B-cell leukemia-xL (Bcl-xL) and mitochondrial membrane potential (ΔΨmt) decrease, cytochrome c release, and caspase-3/Poly Adp Ribose Polymerase (PARP) cleavage. On the other hand, mutant p53 RPMI7951 cell death occurred by PBD-GA-mediated mitochondria- and caspase-dependent pathways via lysosomal membrane permeabilization (LMP), but not through p53 signaling. Finally, compound 5b was shown to reduce murine melanoma size in a mouse model. These results suggest that the PBD-GA could be used as a useful chemotherapeutic agent in melanoma with activated p53 or mutant p53.

Resveratrol in the treatment of pancreatic cancer

Pancreatic cancer (PCa), which is now the fourth most frequent cause of cancer-related death, has a median survival of less than 6 months and a 5-year survival rate of <6%. The hallmarks of this cancer include poor outcome, short survival duration, and resistance to therapy. The poor prognosis of PCa is related to its local recurrence, lymph node and liver metastases, and peritoneal dissemination. Recent studies have indicated that resveratrol has cancer-chemopreventive and anticancer activities. In this short review we summarize the chemopreventive and treatment effects of resveratrol in PCa, as follows: resveratrol inhibits the proliferation of pancreatic cancer cells; induces apoptosis and cell cycle arrest; inhibits metastasis and invasion of PCa cells; inhibits the proliferation and viability of PCa stem cells; enhances the chemoradiosensitization of PCa cells; and can affect diabetes mellitus in addition to PCa. On the basis of these data, resveratrol may be considered a potential anticancer agent for the treatment of PCa.

Synthesis, antiproliferative activity and molecular properties predictions of galloyl derivatives

The present study was designed to investigate the in vitro antiproliferative activity against ten human cancer cell lines of a series of galloyl derivatives bearing substituted-1,3,4-oxadiazole and carbohydrazide moieties. The compounds were also assessed in an in silico study of the absorption, distribution, metabolism and excretion (ADME) in the human body using Lipinski’s parameters, the topological polar surface area (TPSA) and percentage of absorption (%ABS). In general, the introduction of N'-(substituted)-arylidene galloyl hydrazides 4–8 showed a moderate antitumor activity, while the 2-methylthio- and 2-thioxo-1,3,4-oxadiazol-5-yl derivatives 9 and 10 led to increased inhibition of cancer cell proliferation. The precursor compound methyl gallate 2 and the intermediary galloyl hydrazide 3 showed greater antiproliferative activity with GI₅₀ values < 5.54 µM against all human tumor cell lines tested. A higher inhibition effect against ovarian cancer (OVCAR-3) (GI₅₀ = 0.05–5.98 µM) was also shown, with compounds 2, 3, 9 and 10 with GI₅₀ ≤ 0.89 µM standing out in this respect. The in silico study revealed that the compounds showed good intestinal absorption.

Antiproliferative and uncoupling effects of delocalized, lipophilic, cationic gallic acid derivatives on cancer cell lines. Validation in vivo in singenic mice

Tumor cells principally exhibit increased mitochondrial transmembrane potential (ΔΨ(m)) and altered metabolic pathways. The therapeutic targeting and delivery of anticancer drugs to the mitochondria might improve treatment efficacy. Gallic acid exhibits a variety of biological activities, and its ester derivatives can induce mitochondrial dysfunction. Four alkyl gallate triphenylphosphonium lipophilic cations were synthesized, each differing in the size of the linker chain at the cationic moiety. These derivatives were selectively cytotoxic toward tumor cells. The better compound (TPP(+)C10) contained 10 carbon atoms within the linker chain and exhibited an IC50 value of approximately 0.4-1.6 μM for tumor cells and a selectivity index of approximately 17-fold for tumor compared with normal cells. Consequently, its antiproliferative effect was also assessed in vivo. The oxygen consumption rate and NAD(P)H oxidation levels increased in the tumor cell lines (uncoupling effect), resulting in a ΔΨ(m) decrease and a consequent decrease in intracellular ATP levels. Moreover, TPP(+)C10 significantly inhibited the growth of TA3/Ha tumors in mice. According to these results, the antineoplastic activity and safety of TPP(+)C10 warrant further comprehensive evaluation.

Digalloylresveratrol, a novel resveratrol analog inhibits the growth of human pancreatic cancer cells

Digalloylresveratrol (DIG) is a recently synthesized substance aimed to combine the effects of the natural polyphenolic compounds gallic acid and resveratrol, which both are excellent free radical scavengers with anticancer activity. In this study, we investigated the effects of DIG in the human AsPC-1 and BxPC-3 pancreatic adenocarcinoma cell lines. Treatment with DIG dose-dependently attenuated cells in the S phase of the cell cycle and led to a significant depletion of the dATP pool in AsPC-1 cells. The incorporation of (14)C-cytidine into nascent DNA of tumor cells was significantly inhibited at all DIG concentrations due to inhibition of ribonucleotide reductase, a key enzyme of DNA synthesis in tumor cells. Furthermore, Erk1/2 became inactivated and moderated p38 phosphorylation reflecting increased replication stress. DIG also activated ATM and Chk2, and induced the phosphorylation and proteasomal degradation of the proto-oncogene Cdc25A, which contributed to cell cycle attenuation. Taken together, DIG is an excellent free radical scavenger, strongly inhibits RR in situ activity, cell cycle progression, and colony formation in AsPC-1 and BxPC-3 cells thus warranting further investigations.

Gallic acid: molecular rival of cancer

Gallic acid, a predominant polyphenol, has been shown to inhibit carcinogenesis in animal models and in vitro cancerous cell lines. The inhibitory effect of gallic acid on cancer cell growth is mediated via the modulation of genes which encodes for cell cycle, metastasis, angiogenesis and apoptosis. Gallic acid inhibits activation of NF-κB and Akt signaling pathways along with the activity of COX, ribonucleotide reductase and GSH. Moreover, gallic acid activates ATM kinase signaling pathways to prevent the processes of carcinogenesis. The data so far available, both from in vivo and in vitro studies, indicate that this dietary polyphenol could be promising agent in the field of cancer chemoprevention.

Combination effects of digalloylresveratrol with arabinofuranosylcytosine and difluorodeoxycytidine in human leukemia and pancreatic cancer cells

Digalloylresveratrol (DIG) is a newly synthesized agent aimed to combine the biological effects of the natural compounds, gallic acid and resveratrol, which both are free radical scavengers exhibiting anticancer activity. In this study, we investigated the effects of DIG on the growth of human HL-60 leukemia cells and on the colony formation of human BxPC-3 and PANC-1 pancreatic cancer cells. DIG was applied alone and in combination with arabinofuranosylcytosine (Ara-C) or difluorodeoxycytidine (dFdC), depending on the cell line employed. All IC(50) values observed were in the low micromolar range rendering DIG a promising antitumor compound in vitro. Considering the combination experiments, DIG yielded additive effects with Ara-C in HL-60 cells and-to a lesser extent-with dFdC in BxPC-3 and PANC-1 cells. Owing to our results, DIG may be further investigated in vitro and in animals.

Evaluation of the effects of the flavonoid apigenin on apoptotic pathway gene expression on the colon cancer cell line (HT29)

Apigenin (4',5,7-trihydroxyflavone) is one of the leading components supporting targeted treatment options. We explored the cytotoxic and apoptotic effects of various doses of apigenin administered alone and together with 5-fluorouracil (5-FU)-a chemotherapeutic agent with high cytotoxicity-for different incubation periods, on morphologic, DNA, RNA (messenger RNA [mRNA]), and protein levels on the p53 mutant HT29 human colon adenocarcinoma cell line. Treatment with apigenin alone for a 72-hour incubation at 90-μM dose resulted in an apoptotic percentage of 24.92% (P=.001). A higher percentage (29.13%) was observed after treatment with the same dose of apigenin plus 5-FU for the same incubation period (P=.001). These results were confirmed as mRNA and protein expression levels of caspase-3 increased 2.567-fold and mRNA expression levels of caspase-8 increased 3.689-fold compared with the control group. On the other hand, mRNA expression levels of mammalian target of rapamycin (mTOR) and cyclin D1 (CCND1) decreased by 0.423-fold and 0.231-fold, respectively. To our knowledge this is the first study showing that treatment with apigenin alone results in cell cycle arrest through activation of caspase cascade and stimulation of apoptosis in HT29 cells. It also shows that use of apigenin plus 5-FU further increases this effect. This study draws attention to the probable clinical effectiveness of apigenin plus a chemotherapeutic agent with high cytotoxicity. It also highlights the induction of desirable apoptotic effects by targeting the caspase cascade pathway through administration of reduced doses for shorter incubation periods.

Gallic acid induces G2/M phase arrest of breast cancer cell MCF-7 through stabilization of p27(Kip1) attributed to disruption of p27(Kip1)/Skp2 complex

Gallic acid (GA), 3,4,5-trihydroxybenzoic acid, is a natural polyphenolic acid and widely found in gallnuts, tea leaves and various fruits. Previous studies have shown that GA possesses anti-inflammatory, antiallergic and anticarcinogenic activity. In the present study, we aim to investigate the antitumor effects of GA on breast cancer cell. Our results revealed that GA treatment significantly reduced the cell growth of human breast cancer cell MCF-7 in a dose-dependent manner. Further flow cytometric analysis showed that GA induced significant G2/M phase arrest but slightly affected the population of sub-G1MCF-7 cells. Therefore, levels of cyclins, cyclin-dependent kinases (CDKs), and their regulatory proteins involved in S-G2/M transition were investigated. Our findings revealed that levels of cyclin A, CDK2, cyclin B1 and cdc2/CDK1 were diminished; in contrast, levels of the negative regulators p27(Kip1) and p21(Cip1) were increased by GA treatment. Additionally, Skp2, a specific ubiquitin E3 ligase for polyubiquitination of p27(Kip1) was reduced by GA treatment. Further investigation showed that GA attenuated Skp2-p27(Kip1) association and diminished polyubiquitination of p27(Kip1) in MCF-7 cells. Moreover, knockdown of p27(Kip1) but not p21(Cip1) significantly alleviated GA-induced accumulation of G2/M phase. These findings indicate that GA may upregulate p27(Kip1) level via disruption of p27(Kip1)/Skp2 association and the consequent degradation of p27(Kip1) by proteosome, leading to G2/M phase arrest of MCF-7 cell. It is suggested that GA should be beneficial to treatment of breast cancer and p27(Kip1)-deficient carcinomas.

Multifactorial anticancer effects of digalloyl-resveratrol encompass apoptosis, cell-cycle arrest, and inhibition of lymphendothelial gap formation in vitro

Background:

Digalloyl-resveratrol (di-GA) is a synthetic compound aimed to combine the biological effects of the plant polyhydroxy phenols gallic acid and resveratrol, which are both radical scavengers and cyclooxygenase inhibitors exhibiting anticancer activity. Their broad spectrum of activities may probably be due to adjacent free hydroxyl groups.

Methods:

Protein activation and expression were analysed by western blotting, deoxyribonucleoside triphosphate levels by HPLC, ribonucleotide reductase activity by ¹⁴C-cytidine incorporation into nascent DNA and cell-cycle distribution by FACS. Apoptosis was measured by Hoechst 33258/propidium iodide double staining of nuclear chromatin and the formation of gaps into the lymphendothelial barrier in a three-dimensional co-culture model consisting of MCF-7 tumour cell spheroids and human lymphendothelial monolayers.

Results:

In HL-60 leukaemia cells, di-GA activated caspase 3 and dose-dependently induced apoptosis. It further inhibited cell-cycle progression in the G1 phase by four different mechanisms: rapid downregulation of cyclin D1, induction of Chk2 with simultaneous downregulation of Cdc25A, induction of the Cdk-inhibitor p21^Cip/Waf and inhibition of ribonucleotide reductase activity resulting in reduced dCTP and dTTP levels. Furthermore, di-GA inhibited the generation of lymphendothelial gaps by cancer cell spheroid-secreted lipoxygenase metabolites. Lymphendothelial gaps, adjacent to tumour bulks, can be considered as gates facilitating metastatic spread.

Conclusion:

These data show that di-GA exhibits three distinct anticancer activities: induction of apoptosis, cell-cycle arrest and disruption of cancer cell-induced lymphendothelial disintegration.

Resveratrol and resveratrol analogues--structure-activity relationship

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a compound found in wine and is held responsible for a number of beneficial effects of red wine. Besides the prevention of heart disease and significant anti-inflammatory effects, resveratrol might inhibit tumor cell growth and even play a role in the aging process. We here describe the structure-activity relationship of resveratrol and analogues of resveratrol regarding the free radical scavenging and antitumor effects of this exciting natural compound. In addition, we have synthesized a number of analogues of resveratrol with the aim to further improve the beneficial effects of resveratrol. Our studies were based on the analysis of structural properties, which were responsible for the most important effects of this compound. Striking in vivo effects can be observed with hexahydroxystilbene (M8), the most effective synthetic analogue of resveratrol. We could show that M8 inhibits tumor as well as metastasis growth of human melanoma in two different animal models, alone and in combination with dacarbacine.