Pomegranate fruit extract derived from the tree Punica granatum possesses strong antioxidant and antiinflammatory properties. Pomegranate fruit was extracted with acetone and analyzed based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and found to contain anthocyanins, ellagitannins and hydrolyzable tannins
Anthocyanin- and hydrolyzable tannin-rich pomegranate fruit extract modulates MAPK and NF-κB pathways and inhibits skin tumorigenesis in CD-1 mice.
Chemoprevention has come of age as an effective cancer control modality; however, the search for novel agent(s) for the armamentarium of cancer chemoprevention continues. We argue that agents capable of intervening at more than one critical pathway in the carcinogenesis process will have greater advantage over other single-target agents. Pomegranate fruit extract (PFE) derived from the tree Punica granatum possesses strong antioxidant and antiinflammatory properties. Pomegranate fruit was extracted with acetone and analyzed based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and found to contain anthocyanins, ellagitannins and hydrolyzable tannins. We evaluated whether PFE possesses antitumor-promoting effects. We first determined the effect of topical application of PFE to CD-1 mice against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced conventional markers and other novel markers of skin tumor promotion. We found that topical application of PFE (2 mg/mouse) 30 min prior to TPA (3.2 nmole/mouse) application on mouse skin afforded significant inhibition, in a time-dependent manner, against TPA-mediated increase in skin edema and hyperplasia, epidermal ornithine decarboxylase (ODC) activity and protein expression of ODC and cyclooxygenase-2. We also found that topical application of PFE resulted in inhibition of TPA-induced phosphorylation of ERK1/2, p38 and JNK1/2, as well as activation of NF-κB and IKKα and phosphorylation and degradation of IκBα. We next assessed the effect of skin application of PFE on TPA-induced skin tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated CD-1 mouse. The animals pretreated with PFE showed substantially reduced tumor incidence and lower tumor body burden when assessed as total number of tumors per group, percent of mice with tumors and number of tumors per animal as compared to animals that did not receive PFE. In TPA-treated group, 100% of the mice developed tumors at 16 weeks on test, whereas at this time in PFE-treated group, only 30% mice exhibited tumors. Skin application of PFE prior to TPA application also resulted in a significant delay in latency period from 9 to 14 weeks and afforded protection when tumor data were considered in terms of tumor incidence and tumor multiplicity. The results of our study provide clear evidence that PFE possesses antiskin-tumor-promoting effects in CD-1 mouse. Because PFE is capable of inhibiting conventional as well as novel biomarkers of TPA-induced tumor promotion, it may possess chemopreventive activity in a wide range of tumor models. Thus, an in-depth study to define active agent(s) in PFE capable of affording antitumor-promoting effect is warranted.
Chemoprevention, the use of naturally occurring and synthetic agents, to slow the growth, delay the onset, or reverse carcinogenesis is increasingly recognized as an important means for cancer control.1, 2, 3, 4 The expanded definition of chemoprevention also encompasses chemotherapy of precancerous lesions, which are called preinvasive neoplasia, dysplasia, or intraepithelial neoplasia, depending on the organ system. It is appreciated that chemoprevention can be targeted for intervention at all stages of carcinogenesis process exemplified by initiation, promotion and progression.2 For many reasons, most notably for human acceptance, dietary substances are desirable chemopreventive agents.5 Thus, in recent years, the search for novel agents and defining novel targets for chemoprevention have become an intense area of investigation. An ideal chemopreventive agent will be one that is acceptable to human population and has the ability to restore all dysregulated cellular and molecular pathways of multistage carcinogenesis.5, 6 This can be achieved through use of multiple agents, which is a complex undertaking. Alternatively, this could be achieved through the use of single dietary agent capable of interfering at multiple pathways in the carcinogenic process, a very desirable goal.
Pomegranate (Punica granatum, Punicaceae), native to Persia, is an edible fruit cultivated in Mediterranean countries, Afghanistan, India, China, Japan, Russia and the United States (California). Edible parts of pomegranate fruit (about 80% of total fruit weight) comprise 80% juice and 20% seed. Pomegranate fruit extract (PFE) is a rich source of 2 types of polyphenolic compounds: anthocyanins (such as delphinidin, cyanidin and pelargonidin), which give the fruit and juice its red color, and hydrolyzable tannins (such as punicalin, pedunculagin, punicalagin, gallagic and ellagic acid esters of glucose), which account for 92% of the antioxidant activity of the whole fruit.7 The soluble polyphenol content in pomegranate juice varies between 0.2% and 1.0%.8
In recent years, health-promoting effects of PFE are being examined. Gil et al.7 demonstrated that antioxidant activity of PFE, though varies depending on the variety, is higher than that of red wine and green tea. PFE has shown potent antioxidant capacity against lipid peroxidation that may be a central link for the antiatherogenic effect of PFE on lipoprotein, macrophages and platelets.9, 10, 11 Studies have demonstrated that pretreatment of the rats with a methanolic extract of pomegranate peel followed by carbon tetrachloride resulted in restoration of catalase, peroxidase and superoxide dismutase enzyme activities.12 Dietary supplementation of polyphenol-rich pomegranate juice to atherosclerotic mice significantly inhibited the development of atheroclerotic lesions and this may be attributed to the protection of low-density lipoprotein against oxidation.13, 14 Fermented pomegranate juice and cold-pressed PFE can reduce prostaglandin and leukotriene formation by inhibition of cyclooxygenase and lipoxygenase activities.15 Recent studies have shown that pomegranate wine may serve as a potent inhibitor of nuclear factor kappa B (NF-κB) in vascular endothelial cells.16
The multistage mouse skin carcinogenesis model, although an artificial one, is an ideal system to study a number of biochemical alterations, changes in cellular functions and histologic changes that take place during the different stages of chemical carcinogenesis.17, 18 This system has also served as a useful model for initial screen for cancer chemopreventive effects of most dietary substances.18, 19 Studies have shown that skin application of tumor-promoting agents results in inflammatory responses, such as development of edema, hyperplasia, induction of proinflammatory cytokine interleukin-1α, induction of epidermal ornithine decarboxylase (ODC) and cyclooxygenase (COX) protein expression and activity, as well as activation of NF-κB.19, 20, 21, 22 Activation of mitogen-activated protein kinases (MAPKs)/NF-κB pathways has been shown to be involved in tumor growth and development.23, 24 In view of the antiinflammatory and antioxidative activities of PFE, as well as its inhibitory potential against COX and lipoxygenase activities,15 in the present study, we show that topical application of PFE to CD-1 mice possesses antitumor-promoting effects and provide a mechanistic basis for such an effect.
