Synergistic anticancer effects of combined gamma-tocotrienol and celecoxib treatment are associated with suppression in Akt and NFkappaB signaling

The selective cyclooxygenase (COX)-2 inhibitor, celecoxib, and the vitamin E isoform, gamma-tocotrienol, both display potent anticancer activity. However, high dose clinical use of selective COX-2 inhibitors has been limited by gastrointestinal and cardiovascular toxicity, whereas limited absorption and transport of gamma-tocotrienol by the body has made it difficult to obtain and sustain therapeutic levels in the blood and target tissues. Studies were conducted to characterize the synergistic anticancer antiproliferative effects of combined low dose celecoxib and gamma-tocotrienol treatment on mammary tumor cells in culture. The highly malignant mouse +SA mammary epithelial cells were maintained in culture on serum-free defined control or treatment media. Treatment effects on COX-1, COX-2, Akt, NFkappaB and prostaglandin E(2) (PGE(2)) synthesis were assessed following a 3- or 4-day culture period. Treatment with 3-4 microM gamma-tocotrienol or 7.5-10 microM celecoxib alone significantly inhibited +SA cell growth in a dose-responsive manner. However, combined treatment with subeffective doses of gamma-tocotrienol (0.25 microM) and celecoxib (2.5 microM) resulted in a synergistic antiproliferative effect, as determined by isobologram analysis, and this growth inhibitory effect was associated with a reduction in PGE(2) synthesis, and decrease in COX-2, phospho-Akt (active), and phospho-NFkappaB (active) levels. These results demonstrate that the synergistic anticancer effects of combined celecoxib and gamma-tocotrienol therapy are mediated by COX-2 dependent and independent mechanisms. These findings also suggest that combination therapy with these agents may provide enhanced therapeutic response in breast cancer patients, while avoiding the toxicity associated with high-dose COX-2 inhibitor monotherapy.

Nanoencapsulation of pomegranate bioactive compounds for breast cancer chemoprevention

Pomegranate polyphenols are potent antioxidants and chemopreventive agents but have low bioavailability and a short half-life. For example, punicalagin (PU), the major polyphenol in pomegranates, is not absorbed in its intact form but is hydrolyzed to ellagic acid (EA) moieties and rapidly metabolized into short-lived metabolites of EA. We hypothesized that encapsulation of pomegranate polyphenols into biodegradable sustained release nanoparticles (NPs) may circumvent these limitations. We describe here the development, characterization, and bioactivity assessment of novel formulations of poly(D,L-lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-PEG) NPs loaded with pomegranate extract (PE) or individual polyphenols such as PU or EA. Monodispersed, spherical 150-200 nm average diameter NPs were prepared by the double emulsion-solvent evaporation method. Uptake of Alexa Fluor-488-labeled NPs was evaluated in MCF-7 breast cancer cells over a 24-hour time course. Confocal fluorescent microscopy revealed that PLGA-PEG NPs were efficiently taken up, and the uptake reached the maximum at 24 hours. In addition, we examined the antiproliferative effects of PE-, PU-, and/or EA-loaded NPs in MCF-7 and Hs578T breast cancer cells. We found that PE, PU, and EA nanoprototypes had a 2- to 12-fold enhanced effect on cell growth inhibition compared to their free counterparts, while void NPs did not affect cell growth. PU-NPs were the most potent nanoprototype of pomegranates. Thus, PU may be the polyphenol of choice for further chemoprevention studies with pomegranate nanoprototypes. These data demonstrate that nanotechnology-enabled delivery of pomegranate polyphenols enhances their anticancer effects in breast cancer cells. Thus, pomegranate polyphenols are promising agents for nanochemoprevention of breast cancer.

Semisynthetic and biotransformation studies of (1S,2E,4S,6R,7E,11E)-2,7,11-cembratriene-4,6-diol

Tobacco-derived (1 S,2 E,4 S,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (1) and (1 S,2 E,4 R,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (2) were first shown to display potential antitumor-promoting activity in the mid-1980s. However, very little is currently understood regarding the structural activity relationships of tobacco cembranoids. The aim of this present study was to explore antiproliferative activity of various derivatives of (1 S,2 E,4 S,6 R,7 E,11 E)-2,7,11-cembratriene-4,6-diol (1) using semisynthetic and biotransformation approaches. Derivatives of 1 include esterified, oxidized, halogenated, and nitrogen- and sulfur-containing compounds (3-17). Biotransformation of 1 using Mucor ramannianus ATCC 9628 and Cunninghamella elegans ATCC 7929 afforded the known 10 S,11 S-epoxy analogue of 1 (4) as the main metabolite. Biotransformation of the 6-O-acetyl analogue (3) using the marine symbiotic Bacillus megaterium strain MO31 afforded (1 S,2 E,4 S,6 R,7 E,11 E,10 R)-2,7,11-cembratriene-4,6,10-triol (18). (1 S,2 E,4 S,6 R,7 E,11 E,13 R)-2,7,11-Cembratriene-4,6,13-triol-6-O-acetate (6), (1 S,2 E,4 S,6 R,7 E,11 E,13 S)-2,7,11-cembratriene-4,6,13-triol-6-O-acetate (7), the rearranged alpha-ketol (1 S,2 E,4 S,7 Z,11 E)-2,7,11-cembratrien-4-ol-6-one (11), and the secocembranoid 12 showed antiproliferative activity against highly malignant +SA mammary epithelial cells with an IC50 range of 15-30 microM.

Tocotrienol combination therapy results in synergistic anticancer response

Vitamin E represents a family of compounds that is divided into two subgroups called tocopherols and tocotrienols, which act as important antioxidants that regulate peroxidation reactions and control free-radical production within the body. However, many of the biological effects of vitamin E are mediated independently of its antioxidant activity. Although tocopherols and tocotrienols have the same basic chemical structure characterized by a long phytyl chain attached to a chromane ring, only tocotrienols display potent anticancer activity, by modulating multiple intracellular signaling pathways associated with tumor cell proliferation and survival, and combination therapy with other chemotherapeutic agents result in a synergistic anticancer response. Combination therapy is most effective when tocotrienols are combined with agents that have complementary anticancer mechanisms of action. These findings strongly suggest that the synergistic antiproliferative and apoptotic effects demonstrated by combined low dose treatment of γ-tocotrienol with other chemotherapeutic agents may provide significant health benefits in the prevention and/or treatment of breast cancer in women, while at the same time avoiding tumor resistance and toxic side effects associated with high dose monotherapy.

Mechanisms Mediating the Synergistic Anticancer Effects of Combined γ-Tocotrienol and Celecoxib Treatment

AIM: To characterize the intracellular signaling mechanisms mediating the synergistic anticancer effects of combined γ-tocotrienol and celecoxib treatment in neoplastic +SA mouse mammary epithelial cells in vitro. METHODS: +SA mammary tumor cells in different treatment groups were maintained in serum-free defined media containing 10ng/ml EGF as a mitogen and exposed to various doses of γ-tocotrienol and celecoxib alone or in combination. After a 96 hr culture period, cells were collected and whole cell lysates were subjected to Western blot analysis to determine treatment effects on intracellular signaling proteins associated with EGF-dependent mitogenesis and survival, and prostaglandin synthesis and responsiveness. RESULTS: Treatment with high doses of γ-tocotrienol or celecoxib alone inhibited Akt activation and downstream signaling and NFκB activation. Similar treatment with γ-tocotrienol also decreased concentration and activation of ErbB2-4 receptors, whereas celecoxib only inhibited ErbB2-4 receptor activation. In contrast, combined treatment with subeffective doses of γ-tocotrienol and celecoxib resulted in a large decrease ErbB2-4 receptor levels and activation, a decrease in PGE(2) levels, and a corresponding increase in prostaglandin EP2 and EP4 receptor levels. Combined treatment also induced an increase in the prostaglandin catabolizing enzyme, PGDH. CONCLUSION: The synergistic anticancer effects of combined low dose γ-tocotrienol and celecoxib treatment in +SA mammary tumor cells are mediated by COX-2-dependent mechanisms associated with a suppression in PGE(2) levels, as well as, COX-2-independent mechanisms associated with a reduction in ErbB2-4 receptor levels, activation, and subsequent reduction in downstream Akt and NFκB mitogenic signaling.

Pomegranate Intake Protects Against Genomic Instability Induced by Medical X-rays In Vivo in Mice

Ionizing radiation (IR) is a well-documented human carcinogen. The increased use of IR in medical procedures has doubled the annual radiation dose and may increase cancer risk. Genomic instability is an intermediate lesion in IR-induced cancer. We examined whether pomegranate extract (PE) suppresses genomic instability induced by x-rays. Mice were treated orally with PE and exposed to an x-ray dose of 2 Gy. PE intake suppressed x-ray-induced DNA double-strand breaks (DSBs) in peripheral blood and chromosomal damage in bone marrow. We hypothesized that PE-mediated protection against x-ray-induced damage may be due to the upregulation of DSB repair and antioxidant enzymes and/or increase in glutathione (GSH) levels. We found that expression of DSB repair genes was not altered (Nbs1 and Rad50) or was reduced (Mre11, DNA-PKcs, Ku80, Rad51, Rad52 and Brca2) in the liver of PE-treated mice. Likewise, mRNA levels of antioxidant enzymes were reduced (Gpx1, Cat, and Sod2) or were not altered (HO-1 and Sod1) as a function of PE treatment. In contrast, PE-treated mice with and without IR exposure displayed higher hepatic GSH concentrations than controls. Thus, ingestion of pomegranate polyphenols is associated with inhibition of x-ray-induced genomic instability and elevated GSH, which may reduce cancer risk.