Food bioactives, apoptosis, and cancer.

Apoptosis interchangeably referred to as programmed cell death is a key pathway for regulating homeostasis and morphogenesis of mammalian cells and is connected with several diseases, in particular, cancer. It is widely believed that misregulation of this pathway leads to the development of cancer. Reflecting this knowledge, the mechanism of action for many currently used anticancer agents were specifically targeted to regulate the apoptotic pathway further stressing the role of programmed cell death in maintaining normal homeostasis. Another widely accepted concept is the consumption of a variety of colorful foods with strong antioxidant properties. These dietary components also referred to as bioactives would help maintain a healthy body. Although for many of these bioactives exact nutritional benefits are not yet well defined, there is demonstrated scientific evidence suggesting a role for them in cancer prevention. This review summarizes the current knowledge of food bioactives that act through the signaling pathway inducing programmed cell death, thus providing the evidence for these substances in cancer prevention.

Chemopreventive effects of orange peel extract (OPE). I: OPE inhibits intestinal tumor growth in ApcMin/+ mice.

Orange peel is a rich source of flavonoids with polymethoxyflavones as major constituents, compounds associated with potential antioxidant, anti-inflammatory, and antitumor activities. We studied the effect of an orange peel extract (OPE) on intestinal tumor growth in Apc(Min/+) mice, a mouse model for human familial adenomatous polyposis (FAP). The OPE contained 30% polymethoxyflavones, a mixture that included tangeretin (19.0%), heptamethoxyflavone (15.24%), tetramethoxyflavone (13.6%), nobiletin (12.49%), hexamethoxyflavone (11.06%), and sinensitin (9.16%). Apc(Min/+) mice were fed one of four diets: (1) AIN-76A control diet; (2) a new Western-style diet (NWD), i.e., AIN-76A diet modified with decreased calcium, vitamin D, and methyl-donor nutrients and increased lipid content); (3) NWD with 0.25% OPE; and (4) NWD with 0.5% OPE, with all additives premixed in the diet. After 9 weeks of feeding NWD to the Apc(Min/+) mice, tumors increased mainly in the colon, with tumor multiplicity increasing 5.3-fold and tumor volume increasing 6.7-fold. After feeding 0.5% OPE in NWD, the development of tumors markedly decreased, with multiplicity decreasing 49% in the small intestine and 38% in the colon. NWD also led to increased apoptosis in intestinal tumors, and 0.5% OPE in NWD further increased apoptosis in tumors of the small and large intestine. Findings indicated that OPE inhibited tumorigenesis in this preclinical mouse model of FAP, and increased apoptosis may have contributed to this effect.

Chemopreventive effects of orange peel extract (OPE). II: OPE inhibits atypical hyperplastic lesions in rodent mammary gland.

Cancer chemoprevention via the ingestion of natural substances is a current topic of considerable interest. Flavonoids are a family of biologically active phytochemicals having a variety of biological effects. Orange peel extract (OPE) is an abundant source of polymethoxyflavones (PMFs) with potential chemopreventive properties. The OPE used here was a mixture containing tangeretin (19.0%), heptamethoxyflavone (15.24%), tetramethoxyflavone (13.6%), nobiletin (12.49%), hexamethoxyflavone (11.06%), and sinensitin (9.16%). C57Bl/6 mice were fed a new "Western-style" diet (NWD), which had previously induced atypical hyperplasias in mammary gland, and NWD supplemented with a standardized OPE containing 30% PMFs. Mice were fed one of four diets: (1) AIN-76A diet (control); (2) NWD; 0.25% OPE in NWD; or (4) 0.5% OPE in NWD. After 3 months of feeding, atypical hyperplasias developed in mammary glands of mice fed NWD, but not in controls. After feeding OPE in NWD, atypical hyperplasias per mouse decreased in frequency compared to feeding NWD alone (P < .05 in mice fed 0.25% OPE). Apoptosis increased in OPE-treated groups (P < .01) with no inhibition of mitosis. Thus, a standardized preparation of OPE with 30% PMFs decreased development of an atypical hyperplastic lesion and increased apoptosis in ductal epithelial cells of mouse mammary gland.

Inhibitory effects of black tea theaflavin derivatives on 12-O-tetradecanoylphorbol-13-acetate-induced inflammation and arachidonic acid metabolism in mouse ears.

Tea has been shown to possess several health beneficial properties primarily due to its polyphenolic content. The major polyphenolic compounds in black tea leaves are theaflavins (TFs) formed by oxidative coupling of catechins in tea leaves during its processing. In this paper, we report the characterization of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear inflammatory model and the inhibitory effects of major black tea TFs derivatives on this inflammation. In addition, the effect on inflammatory biomarkers, such as proinflammatory cytokines and arachidonic acid metabolites, are reported as well. A single topical application of TPA to ears of CD-1 mice induced a time- and dose-dependent increase in edema as well as formation of proinflammatory cytokine proteins interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) in mouse ears. A single topical application of equimolar of black tea constituents (TF, theaflavin-3-gallate, theaflavin-3'-gallate, and theaflavin-3,3'-digallate) strongly inhibited TPA-induced edema of mouse ears. Application of TFs mixture to mouse ears 20 min prior to each TPA application once a day for 4 days inhibited TPA-induced persistent inflammation, as well as TPA-induced increase in IL-1beta and IL-6 protein levels. TFs also inhibited arachidonic acid (AA) metabolism via both cyclooxygenase (COX) and lipoxygenase pathways. This observation was substantiated by decreased amounts of AA metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels. Combined application of TF and sulindac, a nonsteroidal anti-inflammatory drug resulted a significant synergetic anti-inflammatory effect. Oral administration of TFs or the hot water extract of black tea leaves also significantly inhibited TPA-induced edema in mouse ears. In conclusion, proinflammatory cytokines, IL-1beta and IL-6, as well as the intermediated metabolites of AA, PGE2, and LTB4 are good biomarkers for inflammation. Black tea constituents, TF and its derivatives, had strongly anti-inflammatory activity in vivo which may be due to their ability to inhibit AA metabolism via lipoxygenase and COX pathways.

Novel polyphenol molecule isolated from licorice root (Glycrrhiza glabra) induces apoptosis, G2/M cell cycle arrest, and Bcl-2 phosphorylation in tumor cell lines.

Herbal therapies are commonly used by patients with cancer, despite little understanding about biologically active chemical derivatives. We recently demonstrated that the herbal combination PC-SPES, which contains licorice root, had anti-prostate cancer activity attributable to estrogen(s) that produced a chemical castration. A recent study also demonstrated that licorice root alone decreased circulating testosterone in men. Other studies demonstrated antitumor activity of PC-SPES in vitro associated with decreased expression of the anti-apoptotic protein Bcl-2 and in patients independent of chemical castration, suggesting that other mechanisms of antitumor activity exist separate from chemical castration. In the present study, we assessed licorice root extract for effects on Bcl-2 to identify novel cytotoxic derivatives. Licorice root extract induced Bcl-2 phosphorylation as demonstrated by immunoblot and G2/M cell cycle arrest, similarly to clinically used antimicrotubule agents such as paclitaxel. Bioassay-directed fractionations resulted in a biologically active fraction for Bcl-2 phosphorylation. HPLC separation followed by mass spectrometry and NMR identified 6 compounds. Only one molecule was responsible for Bcl-2 phosphorylation; it was identified as 1-(2,4-dihydroxyphenyl)-3-hydroxy-3-(4'-hydroxyphenyl) 1-propanone (beta-hydroxy-DHP). The effect on Bcl-2 was structure specific, because alpha-hydroxy-DHP, 1-(2,4-dihydroxyphenyl)-2-hydroxy-3-(4'-hydroxyphenyl) 1-propanone, in contrast to beta-hydroxy-DHP, was not capable of Bcl-2 phosphorylation. Pure beta-hydroxy-DHP induced Bcl-2 phosphorylation in breast and prostate tumor cells, G2/M cell cycle arrest, apoptosis demonstrated by Annexin V and TUNEL assay, decreased cell viability demonstrated by a tetrazolium (MTT) assay, and altered microtubule structure. Therefore, these data demonstrate that licorice root contains beta-hydroxy-DHP, which induced Bcl-2 phosphorylation, apoptosis, and G2/M cell cycle arrest, in breast and prostate tumor cells, similarly to the action of more complex (MW >800) antimicrotubule agents used clinically.