Dietary garcinol inhibits 4-nitroquinoline 1-oxide-induced tongue carcinogenesis in rats

Anti-Inflammatory Effect of Garcinol Extracted from Garcinia dulcis via Modulating NF-κB Signaling Pathway

Garcinia is a significant medicinal plant with many beneficial phytoconstituents, including garcinol. This study investigated the anti-inflammatory effect of garcinol isolated from Garcinia dulcis fruit in LPS-activated THP-1 and Raw 264.7 macrophages. The results demonstrated that the low concentration of garcinol did not alter cell viability. Furthermore, co-incubation of garcinol with LPS inhibited the production of pro-inflammatory cytokines, including TNF-α, IL-8, IL-6, IL-1β, and pro-inflammatory mediators, including iNOS and COX-2 at the mRNA and protein expression levels. Garcinol also decreased the secretion of TNF-α, IL-6, IL-1β, PGE2, and NO. Moreover, the anti-inflammatory effects involved an alteration in the NF-κB signaling pathway. Downregulation of pIKKα/β, pIκBα, and pNF-κB was observed, hence reducing the translocation of pNF-κB from the cytosol into the nucleus, which subsequently decreased the production of pro-inflammatory molecules. Therefore, garcinol isolated from Garcinia dulcis is a potential candidate as an anti-inflammatory agent for inflammation-related disease treatment.

Negative terpinen-4-ol modulate potentially malignant and malignant lingual lesions induced by 4-nitroquinoline-1-oxide in rat model

Our aim was to verify the modulative TP-4-ol capacity in 4-nitroquinoline-1-oxide induced oral rat cancer. The stereoisomers of TP-4-ol were used against the human tongue squamous cell line and the negative stereoisomer showed lower IC50. Thirty-one Holtzman rats (120-130 g) were cancer-induced by 4-nitroquinoline-1-oxide (4-NQO/8 weeks/25 ppm) and 32 Holtzman rats (120-130 g) were used to healthy and TP-4-ol toxicity experiments. Six groups were used, healthy, 0.1nL/g of TP-4-ol, 8nL/g of TP-4-ol, 4-NQO, 4-NQO + 0.1nL/g of TP-4-ol, and 4-NQO + 8nL/g of TP-4-ol. We performed the toxicity analysis by biochemical and histopathological analysis. The biochemistry analysis includes alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate transaminase (AST), urea, and creatinine and the histopathology analysis includes the liver, kidney, lung, and spleen. Specifically, for malign modulation, we performed a macroscopic and microscopic analysis. The group exposed to 0.1nL/g of TP-4-ol demonstrated a reduced risk of malignancy in dysplasia considering the criteria of architecture and cytology. Similarly, a drop of percentual rats with SCC diagnosis was observed in 4-NQO + 0.1nL/g (41.6%) when compared to 4-NQO (87.5%). Moreover, the 4-NQO group presented a median of 2.62 SCC/rat and the 4-NQO + 0.1nL/g demonstrated a median of 0.75 SCC/rat. For toxicity analysis, 4-NQO + 0.1nL/g showed focal necrosis in the kidney and 4-NQO showed lung hemorrhagic areas. The concentration of 0.1nL/g was more effective in reducing the tongue induction of potentially malignant and malignant lesions by 4-NQO. A kidney toxicity was observed in healthy animals exposed to 0.1nL/g of TP-4-ol. The negative isoform of terpinen-4-ol negatively modulates the development of potentially malignant and malignant lesions in rats (Rattus nonverdicts albinos, Holtzman) exposed to 4-NQO. (-)-Terpinen-4-ol reduced the mice percentual with squamous cell carcinoma, 87.5 to 41.6%, and decreased the cancer/rat ratio of 2.62 in 4-NQO to 0.75 in 4-NQO + 0.1nL/g. This represents 52.4% by group and 71.3% in the cancer/rat ratio.

Three-Dimensional Printing of an Apigenin-Loaded Mucoadhesive Film for Tailored Therapy to Oral Leukoplakia and the Chemopreventive Effect on a Rat Model of Oral Carcinogenesis

Oral leukoplakia, which presents as white lesions in the oral cavity, including on the tongue, is precancerous in nature. Conservative treatment is preferable, since surgical removal can markedly reduce the patient’s quality of life. In the present study, we focused on the flavonoid apigenin as a potential compound for preventing carcinogenesis, and an apigenin-loaded mucoadhesive oral film was prepared using a three-dimensional (3D) bioprinter (semi-solid extrusion-type 3D printer). Apigenin-loaded printer inks are composed of pharmaceutical excipients (HPMC, CARBOPOL, and Poloxamer), water, and ethanol to dissolve apigenin, and the appropriate viscosity of printer ink after adjusting the ratios allowed for the successful 3D printing of the film. After drying the 3D-printed object, the resulting film was characterized. The chemopreventive effect of the apigenin-loaded film was evaluated using an experimental rat model that had been exposed to 4-nitroquinoline 1-oxide (4NQO) to induce oral carcinogenesis. Treatment with the apigenin-loaded film showed a remarkable chemopreventive effect based on an analysis of the specimen by immunohistostaining. These results suggest that the apigenin-loaded mucoadhesive film may help prevent carcinogenesis. This successful preparation of apigenin-loaded films by a 3D printer provides useful information for automatically fabricating other tailored films (with individual doses and shapes) for patients with oral leukoplakia in a future clinical setting.

Utility of Indian fruits in cancer prevention and treatment: Time to undertake translational and bedside studies

The World Health Organization predicts a 70% increase in cancer incidents in developing nations over the next decade, and it will be the second leading cause of death worldwide. Traditional plant-based medicine systems play an important role against various diseases and provide health care to a large section of the population in developing countries. Indigenous fruits and their bioactive compounds with beneficial effects like antioxidant, antiproliferative, and immunomodulatory are shown to be useful in preventing the incidence of cancer. India is one of the biodiversity regions and is native to numerous flora and fauna in the world. Of the many fruiting trees indigenous to India, Mango (Mangifera indica), Black plum (Eugenia jambolana or Syzygium jambolana), Indian gooseberry (Emblica officinalis or Phyllanthus emblica), kokum (Garcinia indica or Brindonia indica), stone apple or bael (Aegle marmelos), Jackfruit (Artocarpus heterophyllus), Karaunda (Carissa carandas) and Phalsa (Grewia asiatica), Monkey Jackfruit (Artocarpus lakoocha) and Elephant apple (Dillenia indica) have been shown to be beneficial in preventing cancer and in the treatment of cancer in validated preclinical models of study. In this review, efforts are also made to collate the fruits' anticancer effects and the important phytochemicals. Efforts are also made at emphasizing the underlying mechanism/s responsible for the beneficial effects in cancer prevention and treatment. These fruits have been a part of the diet, are non-toxic, and easily acceptable for human application. The plants and some of their phytochemicals possess diverse medicinal properties. The authors propose that future studies should be directed at detailed studies with various preclinical models of study with both composite fruit extract/juice and the individual phytochemicals. Additionally, translational studies should be planned with the highly beneficial, well-investigated and pharmacologically multifactorial amla to understand its usefulness as a cancer preventive in the high-risk population and as a supportive agent in cancer survivors. The outcome of both preclinical and clinical studies will be useful for patients, the healthcare fraternity, pharmaceutical, and agro-based sectors.

Chemopreventive and Anti-tumor Potential of Natural Products in Oral Cancer

Oral cancer (OC) is a multifactorial disease caused by isolated or combined risk factors related to tobacco, alcohol consumption, and human papillomavirus infection. It is an aggressive pathology with a low five-year survival rate after surgery, chemotherapy, and/or radiotherapy, frequently associated with severe side effects. Drugs with the highest anti-tumor effect are obtained from natural products with diverse biological and molecular activities and potential chemopreventive and anticancer properties. This review summarizes the natural products reported to have the chemopreventive and anti-tumor potential for OC treatment, showing that several of these compounds are promising candidates as chemopreventive agents, and those with the highest anti-tumor potential induce apoptosis and inhibit proliferation and metastasis-related processes. For this reason, natural products have the potential to be important preventive and therapeutic options for OC in the future.

Garcinol Exhibits Anti-Neoplastic Effects by Targeting Diverse Oncogenic Factors in Tumor Cells

Garcinol, a polyisoprenylated benzophenone, is the medicinal component obtained from fruits and leaves of Garcinia indica (G. indica) and has traditionally been extensively used for its antioxidant and anti-inflammatory properties. In addition, it has been also been experimentally illustrated to elicit anti-cancer properties. Several in vitro and in vivo studies have illustrated the potential therapeutic efficiency of garcinol in management of different malignancies. It mainly acts as an inhibitor of cellular processes via regulation of transcription factors NF-κB and JAK/STAT3 in tumor cells and have been demonstrated to effectively inhibit growth of malignant cell population. Numerous studies have highlighted the anti-neoplastic potential of garcinol in different oncological transformations including colon cancer, breast cancer, prostate cancer, head and neck cancer, hepatocellular carcinoma, etc. However, use of garcinol is still in its pre-clinical stage and this is mainly attributed to the limitations of conclusive evaluation of pharmacological parameters. This necessitates evaluation of garcinol pharmacokinetics to precisely identify an appropriate dose and route of administration, tolerability, and potency under physiological conditions along with characterization of a therapeutic index. Hence, the research is presently ongoing in the dimension of exploring the precise metabolic mechanism of garcinol. Despite various lacunae, garcinol has presented with promising anti-cancer effects. Hence, this review is motivated by the constantly emerging and promising positive anti-cancerous effects of garcinol. This review is the first effort to summarize the mechanism of action of garcinol in modulation of anti-cancer effect via regulation of different cellular processes.

Dietary garcinol supplementation improves diarrhea and intestinal barrier function associated with its modulation of gut microbiota in weaned piglets

Background

The effects of dietary garcinol on diarrhea and intestinal barrier function associated with its modulation of gut microbiota in weaned piglets were investigated.

Method

One hundred forty four weaned piglets (Duroc × Yorkshire × Landrace) from 16 pens (9 piglets per pen) were randomly divided into four treatment groups: controls (CON) or those supplemented with 200 mg/kg (LOW), 400 mg/kg (MID), or 600 mg/kg (HIGH) diet garcinol. After 14-day trial, three piglets per pen were chosen to collect plasma, intestinal tissue and colonic digesta samples.

Results

We demonstrated for the first time that garcinol promoted growth performance, as increased average daily feed intake (ADFI) and decreased feed/gain ratio (F/G); and reduced diarrhea incidence (P < 0.05); and strengthened antioxidant capacity, as an increased antioxidative index (P < 0.05). Additionally, garcinol ameliorated intestinal barrier dysfunction, as an increased villus height to crypt depth ratio, increased zonula occludens protein 1 (ZO-1), occludin and claudin-1 expression in the jejunum and ileum (P < 0.05), and decreased intestinal permeability (P < 0.05); and reduced inflammation, as decreased cytokine interleukin (IL)-6, IL-10, IL-1β and tumor necrosis factor-α (TNF-α) levels in the mucosa of the jejunum and ileum, and NF-κB p65 translocation (P < 0.05). Moreover, garcinol inhibited the growth of most harmful bacteria in the gut, especially Escherichia coli, and increased the growth of the beneficial bacteria Lactobacillus.

Conclusion

This work provides a fundamental basis for the future development of garcinol-functional food use for improving diarrhea and intestinal barrier function in weaned piglets and for understanding the biological effects of garcinol and its potential as a functional feed additive.

Dietary supplementation with garcinol during late gestation and lactation facilitates acid-base balance and improves the performance of sows and newborn piglets1

The present study was conducted to evaluate the effects of dietary garcinol supplementation during late gestation (from the 90th day of pregnancy; day 90) and lactation on the acid-base balance of the umbilical cord blood and performance of sows and piglets. Sixty sows (Duroc × Yorkshire × Landrace; second- or third-parity; n = 20) were randomly divided into 3 gestation (day 90 of pregnancy) or lactation treatments, control diet (CON; basal diet), basal diet with 200 mg garcinol, and basal diet with 600 mg garcinol per kg of feed. The body weight (BW); backfat thickness and litter size of the sows; and birth weight, weaning weight, and mortality of piglets were recorded. Sows' blood and piglets' umbilical cord blood were collected for the measurements of hematological parameters and antioxidative and immune indexes, and acid-base balance parameters, respectively. The colostrum and milk and fecal samples of the sows were also collected for analysis of milk composition and apparent total tract nutrient digestibility. Garcinol had no effect on the BW and backfat thickness of the sows but significantly increased the birth weight and weaning weight of piglets (P < 0.05) and decreased the mortality (P < 0.05). Moreover, the white blood cell counts and neutrophil count, mean cell hemoglobin, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activity in the plasma of the sows were increased more significantly (P < 0.05) in the garcinol groups than that in the CON group, whereas the malondialdehyde (MDA) content was decreased (P < 0.05). The garcinol treatment significantly increased the pH, HCO3- and base excess values (P < 0.05), whereas it decreased the pCO2 and lactate content (P < 0.05) in the umbilical blood. Dry matter (DM), ash, and ether extract in the colostrum were similar between groups (P > 0.05), whereas the garcinol significantly increased the crude protein (CP) in the milk. In addition, the content of immunoglobulin A (IgA) and immunoglobulin G (IgG) in the plasma of piglets and in colostrum and milk of sows were increased more significantly (P < 0.05) in the garcinol groups than that in the CON group. The apparent total tract nutrient digestibility was similar between treatments. Collectively, this study indicates that sows fed with garcinol in late gestation and lactation showed improved maternal health and antioxidative status, milk protein content, acid-base balance in the umbilical cord blood, and growth performance in piglets, showing promise in natural plant extract nutrition for sows.

The effect of dietary garcinol supplementation on oxidative stability, muscle postmortem glycolysis and meat quality in pigs

The objective of this study was to evaluate the effects of dietary garcinol (0, 200, 400 and 600 mg/kg) on the growth performance, meat quality, postmortem glycolysis and antioxidative capacity of finishing pigs. Dietary garcinol increased pigs' average daily gain, pH _24h, a* and myoglobin content of longissimus dorsi (LM) (P < 0.05), and decreased feed/gain ratio, the L*_24h, glycolytic potential, drip loss, shear force, and backfat depth (P < 0.05). The glutathione peroxidase (GPx), catalase (CAT) and total antioxidative capacity (T-AOC) were significantly increased by garcinol (P < 0.05), while the activity of lactate dehydrogenase (LDH) and malonaldehyde (MDA) content were decreased (P < 0.05). Moreover, garcinol decreased the p300/CBP-associated factor (PCAF) activity, the acetylation level and activities of glycolysis enzymes phosphoglycerate kinase 1 (PGK1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase-3 (PFKFB3) (P < 0.05). The results of this study showed that garcinol decreased postmortem glycolysis, and this may be due to the mechanism of decreasing glycolytic enzyme acetylation induced by PCAF. The present study indicates that garcinol can facilitate the growth performance of pigs and improve pork quality by changing postmortem glycolysis and antioxidative capacity.

Prevention of oral carcinogenesis in rats by Dracaena cinnabari resin extracts

OBJECTIVES

In vivo study was performed to determine the chemopreventive efficacy of the DC resin methanol extract on a 4-nitroquinoline-1-oxide (4NQO) oral cancer animal model.

MATERIALS AND METHODS

This study involves administration of 4NQO solution for 8 weeks alone (cancer induction) or with Dracaena cinnabari (DC) extract at 100, 500, and 1000 mg/kg. DC extract administration started 1 week before exposure until 1 week after the carcinogen exposure was stopped. All rats were sacrificed after 22 weeks, and histological analysis was performed to assess any incidence of pathological changes. Immunohistochemical expressions of selected tumor marker antibodies were analyzed using an image analyzer computer system, and the expression of selected genes involved in apoptosis and proliferative mechanism related to oral cancer were evaluated using RT²-PCR.

RESULTS

The incidence of OSCC decreased with the administration of DC extract at 100, 500, and 1000 mg/kg compared to the induced cancer group. The developed tumor was also observed to be smaller when compared to the induced cancer group. The DC 1000 mg/kg group inhibits the expression of Cyclin D1, Ki-67, Bcl-2, and p53 proteins. It was observed that DC 1000 mg/kg induced apoptosis by upregulation of Bax and Casp3 genes and downregulation of Tp53, Bcl-2, Cox-2, Cyclin D1, and EGFR genes when compared to the induced cancer group.

CONCLUSIONS

The data indicated that systemic administration of the DC resin methanol extract has anticarcinogenic potency on oral carcinogenesis.

CLINICAL RELEVANCE

Chemoprevention with DC resin methanol extract may significantly reduce morbidity and possibly mortality from OSCC.

The epigenetic factor PCAF regulates vascular inflammation and is essential for intimal hyperplasia development

Objective

Genetic P300/CBP-associated factor (PCAF) variation affects restenosis-risk in patients. PCAF has lysine acetyltransferase activity and promotes nuclear factor kappa-beta (NFκB)-mediated inflammation, which drives post-interventional intimal hyperplasia development. We studied the contributing role of PCAF in post-interventional intimal hyperplasia.

Methods and results

PCAF contribution to inflammation and intimal hyperplasia was assessed in leukocytes, macrophages and vascular smooth muscle cells (vSMCs) in vitro and in a mouse model for intimal hyperplasia, in which a cuff is placed around the femoral artery. PCAF deficiency downregulate CCL2, IL-6 and TNF-alpha expression, as demonstrated on cultured vSMCs, leukocytes and macrophages. PCAF KO mice showed a 71.8% reduction of vSMC-rich intimal hyperplasia, a 73.4% reduction of intima/media ratio and a 63.7% reduction of luminal stenosis after femoral artery cuff placement compared to wild type (WT) mice. The association of PCAF and vascular inflammation was further investigated using the potent natural PCAF inhibitor garcinol. Garcinol treatment reduced CCL2 and TNF-alpha expression, as demonstrated on cultured vSMCs and leukocytes.

To assess the effect of garcinol treatment on vascular inflammation we used hypercholesterolemic ApoE*3-Leiden mice. After cuff placement, garcinol treatment resulted in reduced arterial leukocyte and macrophage adherence and infiltration after three days compared to untreated animals.

Conclusions

These results identify a vital role for the lysine acetyltransferase PCAF in the regulation of local inflammation after arterial injury and likely the subsequent vSMC proliferation, responsible for intimal hyperplasia.

Garcinol and Its Role in Chronic Diseases

The various bioactive compounds isolated from leaves and fruits of Garcinia sps plants, have been characterized and experimentally demonstrated to be anti-oxidant, anti-inflammatory and anti-cancer in nature. Garcinol, a polyisoprenylated benzophenone, obtained from plant Garcinia indica has been found to be an effective inhibitor of several key regulatory pathways (e.g., NF-kB, STAT3 etc.) in cancer cells, thereby being able to control malignant growth of solid tumours in vivo. Despite its high potential as an anti-neoplastic modulator of several cancer types such as head and neck cancer, breast cancer, hepatocellular carcinoma, prostate cancer, colon cancer etc., it is still in preclinical stage due to lack of systematic and conclusive evaluation of pharmacological parameters. While it is promising anti-cancer effects are being positively ascertained for therapeutic development, studies on its effectiveness in ameliorating other chronic diseases such as cardiovascular diseases, diabetes, allergy, neurodegenerative diseases etc., though seem favourable, are very recent and require in depth scientific investigation.

Garcinol loaded vitamin E TPGS emulsified PLGA nanoparticles: preparation, physicochemical characterization, in vitro and in vivo studies

Garcinol (GAR) is a naturally occurring polyisoprenylated phenolic compound. It has been recently investigated for its biological activities such as antioxidant, anti-inflammatory, anti ulcer, and antiproliferative effect on a wide range of human cancer cell lines. Though the outcomes are very promising, its extreme insolubility in water remains the main obstacle for its clinical application. Herein we report the formulation of GAR entrapped PLGA nanoparticles by nanoprecipitation method using vitamin E TPGS as an emulsifier. The nanoparticles were characterized for size, surface morphology, surface charge, encapsulation efficiency and in vitro drug release kinetics. The MTT assay depicted a high amount of cytotoxicity of GAR-NPs in B16F10, HepG2 and KB cells. A considerable amount of cell apoptosis was observed in B16f10 and KB cell lines. In vivo cellular uptake of fluorescent NPs on B16F10 cells was also investigated. Finally the GAR loaded NPs were radiolabeled with technetium-99m with >95% labeling efficiency and administered to B16F10 melanoma tumor bearing mice to investigate the in vivo deposition at the tumor site by biodistribution and scintigraphic imaging study. In vitro cellular uptake studies and biological evaluation confirm the efficacy of the formulation for cancer treatment.

An overview of anticancer activity of Garcinia and Hypericum

Cancer is one of the leading causes of death worldwide (approximately 8.2 million cases/year) and, over the next two decades, a 70% increase in new cancer cases is expected. Through analysis of the available drugs between the years of 1930 and 2014, it was found that 48% were either natural products or their derivatives. This proportion increased to 66% when semi-synthetic products were included. The family Clusiaceae Juss. (Malpighiales) includes approximately 1000 species distributed throughout all tropical and temperate regions. The phytochemical profile of this family includes many chemicals with interesting pharmacological activities, including anticancer activities. This study includes an overview of the in vitro and in vivo anticancer activity of secondary metabolites from Garcinia and Hypericum and the mechanisms involved in this activity. Hypericum no longer belong to Clusiaceae family, but was considered in the past by taxonomists, due to similarities with this family. Research in the area has shown that several compounds belonging to different chemical classes exhibit activity in several tumor cell lines in different experimental models. This review shows the significant antineoplasic activity of these compounds, in particular of these two genera and validates the importance of natural products in the search for anticancer drugs.

Garcinol Upregulates GABAA and GAD65 Expression, Modulates BDNF-TrkB Pathway to Reduce Seizures in Pentylenetetrazole (PTZ)-Induced Epilepsy

BACKGROUND Epilepsy is the most predominant neurological disorder characterized by recurrent seizures. Despite treatment with antiepileptic drugs, epilepsy still is a challenge to treat, due to the associated adverse effects of the drugs. Previous investigations have shown critical roles of BDNF-TrkB signalling and expression of glutamic acid decarboxylase 65 (GAD65) and GABAA in the brain during epilepsy. Thus, drugs that could modulate BDNF-TrkB signal and expression of GAD65 and GABAA could aid in therapy. Recent experimental data have focussed on plant-derived compounds in treatments. Garcinol (camboginol), is a polyisoprenylated benzophenone derived from the fruit of Garcinia indica. We investigated the effects of garcinol in pentylenetetrazole (PTZ)-induced epileptic models. MATERIAL AND METHODS Seizure scores were measured in epilepsy kindled mice. Neuronal degeneration and apoptosis were assessed by Nissl staining, TUNEL assay, and Fluoro-Jade B staining. Immunohistochemistry was performed to evaluate cleaved caspase-3 expressions. Expression of BDNF, TrkB, GABAA, GAD65, Bad, Bcl-2, Bcl-xL, and Bax were determined by western blots. RESULTS Significantly reduced seizure scores and mortality rates were observed with pretreatment with garcinol. Elevated expression of apoptotic proteins and caspase-3 in kindled mice were effectively downregulated by garcinol. Epileptogenic mice presented increased BDNF and TrkB with considerably decreased GABAA and GAD65 expression. Garcinol significantly enhanced GABAA and GAD65 while it suppressed BDNF and TrkB. Garcinol enhanced the performance of mice in Morris water maze tests. CONCLUSIONS Garcinol exerts neuroprotective effects via supressing apoptosis and modulating BDNF-TrkB signalling and GAD65/GABAA expressions and also enhanced cognition and memory of the mice.

Targeting arachidonic acid pathway by natural products for cancer prevention and therapy

Arachidonic acid (AA) pathway, a metabolic process, plays a key role in carcinogenesis. Hence, AA pathway metabolic enzymes phospholipase A₂s (PLA₂s), cyclooxygenases (COXs) and lipoxygenases (LOXs) and their metabolic products, such as prostaglandins and leukotrienes, have been considered novel preventive and therapeutic targets in cancer. Bioactive natural products are a good source for development of novel cancer preventive and therapeutic drugs, which have been widely used in clinical practice due to their safety profiles. AA pathway inhibitory natural products have been developed as chemopreventive and therapeutic agents against several cancers. Curcumin, resveratrol, apigenin, anthocyans, berberine, ellagic acid, eugenol, fisetin, ursolic acid, [6]-gingerol, guggulsteone, lycopene and genistein are well known cancer chemopreventive agents which act by targeting multiple pathways, including COX-2. Nordihydroguaiaretic acid and baicalein can be chemopreventive molecules against various cancers by inhibiting LOXs. Several PLA₂s inhibitory natural products have been identified with chemopreventive and therapeutic potentials against various cancers. In this review, we critically discuss the possible utility of natural products as preventive and therapeutic agents against various oncologic diseases, including prostate, pancreatic, lung, skin, gastric, oral, blood, head and neck, colorectal, liver, cervical and breast cancers, by targeting AA pathway. Further, the current status of clinical studies evaluating AA pathway inhibitory natural products in cancer is reviewed. In addition, various emerging issues, including bioavailability, toxicity and explorability of combination therapy, for the development of AA pathway inhibitory natural products as chemopreventive and therapeutic agents against human malignancy are also discussed.

Garcinol sensitizes human head and neck carcinoma to cisplatin in a xenograft mouse model despite downregulation of proliferative biomarkers

Platinum compounds such as cisplatin and carboplatin are frequently used as the first-line chemotherapy for the treatment of the head and neck squamous cell carcinoma (HNSCC). In the present study, we investigated whether garcinol, a polyisoprenylated benzophenone can chemosensitize HNSCC to cisplatin. We found that garcinol inhibited the viability of a panel of diverse HNSCC cell lines, enhanced the apoptotic effect of cisplatin, suppressed constitutive as well as cisplatin-induced NF-κB activation, and downregulated the expression of various oncogenic gene products (cyclin D1, Bcl-2, survivin and VEGF). In vivo study showed that administration of garcinol alone (0.5 mg/kg body weight, i.p. five times/week) significantly suppressed the growth of the tumor, and this effect was further increased by cisplatin. Both the markers of proliferation index (Ki-67) and microvessel density (CD31) were downregulated in tumor tissues by the combination of cisplatin and garcinol. The pharmacokinetic results of garcinol indicated that good systemic exposure was achievable after i.p. administration of garcinol at 0.5 mg/kg and 2 mg/kg with mean peak concentration (Cmax) of 1825.4 and 6635.7 nM in the mouse serum, respectively. Overall, our results suggest that garcinol can indeed potentiate the effects of cisplatin by negative regulation of various inflammatory and proliferative biomarkers.

Pneumocystis jirovecii Rtt109, a novel drug target for Pneumocystis pneumonia in immunosuppressed humans

Pneumocystis pneumonia (PcP) is a significant cause of morbidity and mortality in immunocompromised patients. In humans, PcP is caused by the opportunistic fungal species Pneumocystis jirovecii. Progress in Pneumocystis research has been hampered by a lack of viable in vitro culture methods, which limits laboratory access to human-derived organisms for drug testing. Consequently, most basic drug discovery research for P. jirovecii is performed using related surrogate organisms such as Pneumocystis carinii, which is derived from immunosuppressed rodents. While these studies provide useful insights, important questions arise about interspecies variations and the relative utility of identified anti-Pneumocystis agents against human P. jirovecii. Our recent work has identified the histone acetyltransferase (HAT) Rtt109 in P. carinii (i.e., PcRtt109) as a potential therapeutic target for PcP, since Rtt109 HATs are widely conserved in fungi but are absent in humans. To further address the potential utility of this target in human disease, we now demonstrate the presence of a functional Rtt109 orthologue in the clinically relevant fungal pathogen P. jirovecii (i.e., PjRtt109). In a fashion similar to that of Pcrtt109, Pjrtt109 restores H3K56 acetylation and genotoxic resistance in rtt109-null yeast. Recombinant PjRtt109 is an active HAT in vitro, with activity comparable to that of PcRtt109 and yeast Rtt109. PjRtt109 HAT activity is also enhanced by the histone chaperone Asf1 in vitro. PjRtt109 and PcRtt109 showed similar low micromolar sensitivities to two reported small-molecule HAT inhibitors in vitro. Together, these results demonstrate that PjRtt109 is a functional Rtt109 HAT, and they support the development of anti-Pneumocystis agents directed at Rtt109-catalyzed histone acetylation as a novel therapeutic target for human PcP.

Direct interaction of garcinol and related polyisoprenylated benzophenones of Garcinia cambogia fruits with the transcription factor STAT-1 as a likely mechanism of their inhibitory effect on cytokine signaling pathways

Garcinol (1), a polyisoprenylated benzophenone occurring in Garcinia species, has been reported to exert anti-inflammatory activity in LPS-stimulated macrophages, through inhibition of NF-κB and/or JAK/STAT-1 activation. In order to provide deeper insight into its effects on the cytokine signaling pathway and to clarify the underlying molecular mechanisms, 1 was isolated from the fruits of Garcinia cambogia along with two other polyisoprenylated benzophenones, guttiferones K (2) and guttiferone M (3), differing from each other in their isoprenyl moieties and their positions on the benzophenone core. The affinities of 1-3 for the STAT-1 protein have been evaluated by surface plasmon resonance and molecular docking studies and resulted in KD values in the micromolar range. Consistent with the observed high affinity toward the STAT-1 protein, garcinol and guttiferones K and M were able to modulate cytokine signaling in different cultured cell lines, mainly by inhibiting STAT-1 nuclear transfer and DNA binding, as assessed by an electrophorectic mobility shift assay.

Inhibition of STAT3 dimerization and acetylation by garcinol suppresses the growth of human hepatocellular carcinoma in vitro and in vivo

Background

Constitutive activation of signal transducer and activator of transcription 3 (STAT3) has been linked with proliferation, survival, invasion and angiogenesis of a variety of human cancer cells, including hepatocellular carcinoma (HCC). Thus, novel agents that can suppress STAT3 activation have potential for both prevention and treatment of HCC. Here we report, garcinol, a polyisoprenylated benzophenone, could suppress STAT3 activation in HCC cell lines and in xenografted tumor of HCC in nude mice model.

Experimental design

Different HCC cell lines have been treated with garcinol and the inhibition of STAT3 activation, dimerization and acetylation have been checked by immunoblotting, immuno-fluorescence, and DNA binding assays. Xenografted tumor model has been generated in nude mice using HCC cell line and effect of garcinol in the inhibition of tumor growth has been investigated.

Results

Garcinol could inhibit both constitutive and interleukin (IL-6) inducible STAT3 activation in HCC cells. Computational modeling showed that garcinol could bind to the SH2 domain of STAT3 and suppress its dimerization in vitro. Being an acetyltransferase inhibitor, garcinol also inhibits STAT3 acetylation and thus impairs its DNA binding ability. The inhibition of STAT3 activation by garcinol led to the suppression of expression of various genes involved in proliferation, survival, and angiogenesis. It also suppressed proliferation and induced substantial apoptosis in HCC cells. Remarkably, garcinol inhibited the growth of human HCC xenograft tumors in athymic nu/nu mice, through the inhibition of STAT3 activation.

Conclusion

Overall, our results suggest that garcinol exerts its anti-proliferative and pro-apoptotic effects through suppression of STAT3 signaling in HCC both in vitro and in vivo.

Protective effects of garcinol on dimethylnitrosamine-induced liver fibrosis in rats

Garcinol markedly reduced DMN-induced liver fibrosis in rats.

Garcinol, a polyisoprenylated benzophenone modulates multiple proinflammatory signaling cascades leading to the suppression of growth and survival of head and neck carcinoma

Constitutive activation of proinflammatory transcription factors such as STAT3 and NF-κB plays a pivotal role in the proliferation and survival of squamous cell carcinoma of the head and neck (HNSCC). Thus, the agents that can modulate deregulated STAT3 and NF-κB activation have a great potential both for the prevention and treatment of HNSCC. In the present report, we investigated the potential effects of garcinol, an active component of Garcinia indica on various inflammatory mediators involved in HNSCC progression using cell lines and xenograft mouse model. We found that garcinol inhibited constitutively activated STAT3 in HNSCC cells in a time- and dose-dependent manner, which correlated with the suppression of the upstream kinases (c-Src, JAK1, and JAK2) in HNSCC cells. Also, we noticed that the generation of reactive oxygen species is involved in STAT3 inhibitory effect of garcinol. Furthermore, garcinol exhibited an inhibitory effect on the constitutive NF-κB activation, mediated through the suppression of TGF-β-activated kinase 1 (TAK1) and inhibitor of IκB kinase (IKK) activation in HNSCC cells. Garcinol also downregulated the expression of various gene products involved in proliferation, survival, and angiogenesis that led to the reduction of cell viability and induction of apoptosis in HNSCC cells. When administered intraperitoneally, garcinol inhibited the growth of human HNSCC xenograft tumors in male athymic nu/nu mice. Overall, our results suggest for the first time that garcinol mediates its antitumor effects in HNSCC cells and mouse model through the suppression of multiple proinflammatory cascades.

Differential effects of garcinol and curcumin on histone and p53 modifications in tumour cells

Background

Post-translational modifications (PTMs) of histones and other proteins are perturbed in tumours. For example, reduced levels of acetylated H4K16 and trimethylated H4K20 are associated with high tumour grade and poor survival in breast cancer. Drug-like molecules that can reprogram selected histone PTMs in tumour cells are therefore of interest as potential cancer chemopreventive agents. In this study we assessed the effects of the phytocompounds garcinol and curcumin on histone and p53 modification in cancer cells, focussing on the breast tumour cell line MCF7.

Methods

Cell viability/proliferation assays, cell cycle analysis by flow cytometry, immunodetection of specific histone and p53 acetylation marks, western blotting, siRNA and RT-qPCR.

Results

Although treatment with curcumin, garcinol or the garcinol derivative LTK-14 hampered MCF7 cell proliferation, differential effects of these compounds on histone modifications were observed. Garcinol treatment resulted in a strong reduction in H3K18 acetylation, which is required for S phase progression. Similar effects of garcinol on H3K18 acetylation were observed in the osteosarcoma cells lines U2OS and SaOS2. In contrast, global levels of acetylated H4K16 and trimethylated H4K20 in MCF7 cells were elevated after garcinol treatment. This was accompanied by upregulation of DNA damage signalling markers such as γH2A.X, H3K56Ac, p53 and TIP60. In contrast, exposure of MCF7 cells to curcumin resulted in increased global levels of acetylated H3K18 and H4K16, and was less effective in inducing DNA damage markers. In addition to its effects on histone modifications, garcinol was found to block CBP/p300-mediated acetylation of the C-terminal activation domain of p53, but resulted in enhanced acetylation of p53K120, and accumulation of p53 in the cytoplasmic compartment. Finally, we show that the elevation of H4K20Me3 levels by garcinol correlated with increased expression of SUV420H2, and was prevented by siRNA targeting of SUV420H2.

Conclusion

In summary, although garcinol and curcumin can both inhibit histone acetyltransferase activities, our results show that these compounds have differential effects on cancer cells in culture. Garcinol treatment alters expression of chromatin modifying enzymes in MCF7 cells, resulting in reprogramming of key histone and p53 PTMs and growth arrest, underscoring its potential as a cancer chemopreventive agent.

A naturally-occurring histone acetyltransferase inhibitor derived from Garcinia indica impairs newly acquired and reactivated fear memories

The study of the cellular and molecular mechanisms underlying the consolidation and reconsolidation of traumatic fear memories has progressed rapidly in recent years, yet few compounds have emerged that are readily useful in a clinical setting for the treatment of anxiety disorders such as post-traumatic stress disorder (PTSD). Here, we use a combination of biochemical, behavioral, and neurophysiological methods to systematically investigate the ability of garcinol, a naturally-occurring histone acetyltransferase (HAT) inhibitor derived from the rind of the fruit of the Kokum tree (Garcina indica), to disrupt the consolidation and reconsolidation of Pavlovian fear conditioning, a widely studied rodent model of PTSD. We show that local infusion of garcinol into the rat lateral amygdala (LA) impairs the training and retrieval-related acetylation of histone H3 in the LA. Further, we show that either intra-LA or systemic administration of garcinol within a narrow window after either fear conditioning or fear memory retrieval significantly impairs the consolidation and reconsolidation of a Pavlovian fear memory and associated neural plasticity in the LA. Our findings suggest that a naturally-occurring compound derived from the diet that regulates chromatin function may be useful in the treatment of newly acquired or recently reactivated traumatic memories.

Development of a 4-nitroquinoline-1-oxide model of lymph node metastasis in oral squamous cell carcinoma

OBJECTIVES

Lymph node metastasis is one of the most important prognostic factors in oral squamous cell carcinoma. However, regional lymph node metastasis from oral cancer has barely been investigated in 4-nitroquinoline-1-oxide (4NQO) models. In this study, we developed a 4NQO-treated mouse model of oral squamous cell carcinoma that displayed lymph node metastasis and examined the occurrence and timing of the lymph node metastasis.

MATERIALS AND METHODS

BALB/c mice were treated with 200 μg/ml 4NQO in drinking water for 20 weeks and then followed for 4 weeks. Four mice were sacrificed bi-weekly, and oral lesion and regional lymph node metastasis were assessed during the week 25-32 and week 33-40 observation periods.

RESULTS

Tumor formation and local lymph enlargement were observed from 25 weeks onwards. The presence of metastatic tumor cells in the enlarged lymph nodes was confirmed via the detection of tumor infiltration by HE staining and cytokeratin positivity by immunostaining at both 28 and 36 weeks. The incidence rates of oral squamous cell carcinoma and local lymph node metastasis were 68.8% and 12.5% in the week 25-32 observation period, and 100% and 100% in the week 33-40 observation period, respectively.

CONCLUSIONS

A lymph node metastasis model involving mice being subjected to high-dose 4NQO treatment for a long period and then followed for a prolonged period was established. This model might provide a platform for studying the mechanism of lymphatic metastasis in oral carcinoma, leading to the development of new therapies for advanced oral carcinoma.

Chemoprevention of 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster cheek pouch carcinogenesis by a 5-lipoxygenase inhibitor, garcinol

Our previous studies have shown that aberrant arachidonic acid metabolism, especially the 5-lipoxygenase (5-Lox) pathway, is involved in oral carcinogenesis and can be targeted for cancer prevention. To develop potent topical agents for oral cancer chemoprevention, 5 known 5-Lox inhibitors from dietary and synthetic sources (Zileuton, ABT-761, licofelone, curcumin, and garcinol) were evaluated in silico for their potential efficacy. Garcinol, a polyisoprenylated benzophenone from the fruit rind of Garcinia spp., was found to be a promising agent based on the calculation of a theoretical activity index. Computer modeling showed that garcinol well fit the active site of 5-Lox, and potentially inhibited enzyme activity through interactions between the phenolic hydroxyl groups and the non-heme catalytic iron. In a short-term study on 7,12-dimethylbenz[a]anthracene (DMBA)-treated hamster cheek pouch, topical garcinol suppressed leukotriene B4 (LTB4) biosynthesis and inhibited inflammation and cell proliferation in the oral epithelium. In a long-term carcinogenesis study, topical garcinol significantly reduced the size of visible tumors, the number of cancer lesions, cell proliferation, and LTB4 biosynthesis. These results demonstrated that topical application of a 5-Lox inhibitor, garcinol, had chemopreventive effect on DMBA-induced hamster cheek pouch carcinogenesis.

Garcinol regulates EMT and Wnt signaling pathways in vitro and in vivo, leading to anticancer activity against breast cancer cells

Anticancer properties of Garcinia indica-derived garcinol are just beginning to be elucidated. We have earlier reported its cancer cell-specific induction of apoptosis in breast cancer cells, which was mediated through the downregulation of NF-κB signaling pathway. To gain further mechanistic insight, here, we show for the first time that garcinol effectively reverses epithelial-to-mesenchymal transition (EMT), that is, it induces mesenchymal-to-epithelial transition (MET) in aggressive triple-negative MDA-MB-231 and BT-549 breast cancer cells. This was associated with upregulation of epithelial marker E-cadherin and downregulation of mesenchymal markers vimentin, ZEB-1, and ZEB-2. We also found that garcinol upregulates the expression of miR-200 and let-7 family microRNAs (miRNAs), which provides a molecular mechanism for the observed reversal of EMT to MET. Transfection of cells with NF-κB p65 subunit attenuated the effect of garcinol on apoptosis induction through reversal of MET to EMT. Forced transfection of p65 and anti-miR-200s could also reverse the inhibitory effect of garcinol on breast cancer cell invasion. Moreover, treatment with garcinol resulted in increased phosphorylation of β-catenin concomitant with its reduced nuclear localization. The results were also validated in vivo in a xenograft mouse model where garcinol was found to inhibit NF-κB, miRNAs, vimentin, and nuclear β-catenin. These novel findings suggest that the anticancer activity of garcinol against aggressive breast cancer cells is, in part, due to reversal of EMT phenotype, which is mechanistically linked with the deregulation of miR-200s, let-7s, NF-κB, and Wnt signaling pathways.

Potential role of garcinol as an anticancer agent

Garcinol, a polyisoprenylated benzophenone, is extracted from the rind of the fruit of Garcinia indica, a plant found extensively in tropical regions. Although the fruit has been consumed traditionally over centuries, its biological activities, specifically its anticancer potential is a result of recent scientific investigations. The anticarcinogenic properties of garcinol appear to be moderated via its antioxidative, anti-inflammatory, antiangiogenic, and proapoptotic activities. In addition, garcinol displays effective epigenetic influence by inhibiting histone acetyltransferases (HAT 300) and by possible posttranscriptional modulation by mi RNA profiles involved in carcinogenesis. In vitro as well as some in vivo studies have shown the potential of this compound against several cancers types including breast, colon, pancreatic, and leukemia. Although this is a promising molecule in terms of its anticancer properties, investigations in relevant animal models, and subsequent human trials are warranted in order to fully appreciate and confirm its chemopreventative and/or therapeutic potential.

Anticancer drugs from traditional toxic Chinese medicines

Many anticancer drugs are obtained from natural sources. Nature produces a variety of toxic compounds, which are often used as anticancer drugs. Up to now, there are at least 120 species of poisonous botanicals, animals and minerals, of which more than half have been found to possess significant anticancer properties. In spite of their clinical toxicity, they exhibit pharmacological effects and have been used as important traditional Chinese medicines for the different stages of cancer. The article reviews many structures such as alkaloids of Camptotheca acuminata, Catharanthus roseus and Cephalotaxus fortunei, lignans of Dysosma versipellis and Podophyllum emodi, ketones of Garcinia hanburyi, terpenoids of Mylabris and Ginkgo biloba, diterpenoids of Tripterygium wilfordii, Euphorbia fischeriana, Euphorbia lathyris, Euphorbia kansui, Daphne genkwa, Pseudolarix kaempferi and Brucea javanica, triterpenoids of Melia toosendan, steroids of Periploca sepium, Paris polyphylla and Venenum Bufonis, and arsenic compounds including Arsenicum and Realgar. By comparing their related phytochemistry, toxic effects and the recent advances in understanding the mechanisms of action, this review puts forward some ideals and examples about how to increase antitumour activity and/or reduce the side effects experienced with Chinese medicine.

Oral carcinogenesis and oral cancer chemoprevention: a review

Oral cancer is one of the major global threats to public health. The development of oral cancer is a tobacco-related multistep and multifocal process involving field cancerization and carcinogenesis. The rationale for molecular-targeted prevention of oral cancer is promising. Biomarkers of genomic instability, including aneuploidy and allelic imbalance, are possible to measure the cancer risk of oral premalignancies. Understanding of the biology of oral carcinogenesis will yield important advances for detecting high-risk patients, monitoring preventive interventions, and assessing cancer risk and pharmacogenomics. In addition, novel chemopreventive agents based on molecular mechanisms and targets against oral cancers will be derived from studies using appropriate animal carcinogenesis models. New approaches, such as molecular-targeted agents and agent combinations in high-risk oral individuals, are undoubtedly needed to reduce the devastating worldwide consequences of oral malignancy.

Understanding carcinogenesis for fighting oral cancer

Oral cancer is one of the major global threats to public health. Oral cancer development is a tobacco-related multistep and multifocal process involving field cancerization and carcinogenesis. The rationale for molecular-targeted prevention of oral cancer is promising. Biomarkers of genomic instability, including aneuploidy and allelic imbalance, are able to measure the cancer risk of oral premalignancies. Understanding of the biology of oral carcinogenesis will give us important advances for detecting high-risk patients, monitoring preventive interventions, assessing cancer risk, and pharmacogenomics. In addition, novel chemopreventive agents based on molecular mechanisms and targets against oral cancers will be derived from research using appropriate animal carcinogenesis models. New approaches, such as interventions with molecular-targeted agents and agent combinations in high-risk oral individuals, are undoubtedly needed to reduce the devastating worldwide consequences of oral malignancy.

The anti-cancer agent guttiferone-A permeabilizes mitochondrial membrane: ensuing energetic and oxidative stress implications

Guttiferone-A (GA) is a natural occurring polyisoprenylated benzophenone with cytotoxic action in vitro and anti-tumor action in rodent models. We addressed a potential involvement of mitochondria in GA toxicity (1-25 μM) toward cancer cells by employing both hepatic carcinoma (HepG2) cells and succinate-energized mitochondria, isolated from rat liver. In HepG2 cells GA decreased viability, dissipated mitochondrial membrane potential, depleted ATP and increased reactive oxygen species (ROS) levels. In isolated rat-liver mitochondria GA promoted membrane fluidity increase, cyclosporine A/EGTA-insensitive membrane permeabilization, uncoupling (membrane potential dissipation/state 4 respiration rate increase), Ca²⁺ efflux, ATP depletion, NAD(P)H depletion/oxidation and ROS levels increase. All effects in cells, except mitochondrial membrane potential dissipation, as well as NADPH depletion/oxidation and permeabilization in isolated mitochondria, were partly prevented by the a NAD(P)H regenerating substrate isocitrate. The results suggest the following sequence of events: 1) GA interaction with mitochondrial membrane promoting its permeabilization; 2) mitochondrial membrane potential dissipation; 3) NAD(P)H oxidation/depletion due to inability of membrane potential-sensitive NADP+ transhydrogenase of sustaining its reduced state; 4) ROS accumulation inside mitochondria and cells; 5) additional mitochondrial membrane permeabilization due to ROS; and 6) ATP depletion. These GA actions are potentially implicated in the well-documented anti-cancer property of GA/structure related compounds.

Apoptosis-inducing effect of garcinol is mediated by NF-kappaB signaling in breast cancer cells

Garcinol, obtained from Garcinia indica in tropical regions, is used for its numerous biological effects. Its anti-cancer activity has been suggested but the mechanism of action has not been studied in-detail, especially there is no report on its action against breast cancer cells. Here we tested our hypothesis that garcinol may act as an anti-proliferative and apoptosis-inducing agent against breast cancer cell lines. Using multiple techniques such as MTT, Histone-DNA ELISA, Annexin V-PI staining, Western blot for activated caspases and cleaved PARP, homogenous caspase-3/7 fluorometric assay and EMSA, we investigated the mechanism of apoptosis-inducing effect of garcinol in ER-positive MCF-7 and ER-negative MDA-MB-231 cells. We found that garcinol exhibits dose-dependent cancer cell-specific growth inhibition in both the cell lines with a concomitant induction of apoptosis, and has no effect on non-tumorigenic MCF-10A cells. Our results suggested induction of caspase-mediated apoptosis in highly metastatic MDA-MB-231 cells by garcinol. Down-regulation of NF-kappaB signaling pathway was observed to be the mechanism of apoptosis-induction. Garcinol inhibited constitutive NF-kappaB activity, which was consistent with down-regulation of NF-kappaB-regulated genes. This is the first report on anti-proliferative and apoptosis-inducing action of garcinol against human breast cancer cells and the results suggest that this natural compound merits investigation as a potential chemo-preventive/-therapeutic agent, especially against breast cancer.

Garcinol potentiates TRAIL-induced apoptosis through modulation of death receptors and antiapoptotic proteins

Whether garcinol, the active component of Garcinia indica, can modulate the sensitivity of cancer cells to TRAIL, a cytokine currently in phase II clinical trial, was investigated. We found that garcinol potentiated TRAIL-induced apoptosis of cancer cells as indicated by intracellular esterase activity, DNA strand breaks, accumulation of the membrane phospholipid phosphatidylserine, mitochondrial activity, and activation of caspase-8, -9, and -3. We found that garcinol, independent of the cell type, induced both of the TRAIL receptors, death receptor 4 (DR4) and DR5. Garcinol neither induced the receptors on normal cells nor sensitized them to TRAIL. Deletion of DR5 or DR4 by small interfering RNA significantly reduced the apoptosis induced by TRAIL and garcinol. In addition, garcinol downregulated various cell survival proteins including survivin, bcl-2, XIAP, and cFLIP, and induced bid cleavage, bax, and cytochrome c release. Induction of death receptors by garcinol was found to be independent of modulation of CCAAT/enhancer-binding protein-homologous protein, p53, bax, extracellular signal-regulated kinase, or c-Jun-NH(2)-kinase. The effect of garcinol was mediated through the generation of reactive oxygen species, in as much as induction of both death receptors, modulation of antiapoptotic and proapoptotic proteins, and potentiation of TRAIL-induced apoptosis were abolished by N-acetyl cysteine and glutathione. Interestingly, garcinol also converted TRAIL-resistant cells into TRAIL-sensitive cells. Overall, our results indicate that garcinol can potentiate TRAIL-induced apoptosis through upregulation of death receptors and downregulation of antiapoptotic proteins. Mol Cancer Ther; 9(4); 856-68. (c)2010 AACR.