Debbie E. McDonald

Pterostilbene inhibits breast cancer in vitro through mitochondrial depolarization and induction of caspase-dependent apoptosis.

BACKGROUND Epidemiologic studies suggest that diets high in fruits and vegetables reduce cancer risk. Resveratrol, a compound present in grapes, has been shown to inhibit a variety of primary tumors. Pterostilbene, an analogue of resveratrol found in blueberries, has both antioxidant and antiproliferative properties. We hypothesized that pterostilbene would induce apoptosis and inhibit breast cancer cell growth in vitro. METHODS Breast cancer cells were treated with graduated doses of pterostilbene. Cell viability was measured by MTT assay. Apoptosis was evaluated via DNA fragmentation assay and TUNEL assay. Apo-ONE caspase-3/7 assay was used to evaluate caspase activity. Flow cytometry was used to evaluate mitochondrial depolarization, superoxide formation, and cell cycle. Students t-test and two-way ANOVA with Bonferroni posttests were utilized for statistical analysis. RESULTS Pterostilbene decreased breast cancer cell viability in a concentration- and time-dependent manner. Pterostilbene treatment increased caspase-3/7 activity and apoptosis in both cell lines. Caspase-3/7 inhibitors completely reversed pterostilbenes effects on cell viability. Pterostilbene treatment triggered mitochondrial depolarization, increased superoxide anion, and caused alteration in cell cycle. CONCLUSIONS Pterostilbene treatment inhibits the growth of breast cancer in vitro through caspase-dependent apoptosis. Mitochondrial membrane depolarization and increased superoxide anion may contribute to the activation downstream effector caspases. Caspase inhibition leads to complete reversal of pterostilbenes effect on cell viability. Further in vitro mechanistic studies and in vivo experiments are warranted to determine its potential for the treatment of breast cancer.

Pterostilbene Inhibits Lung Cancer Through Induction of Apoptosis

BACKGROUND Lung cancer remains the leading cause of cancer mortality in the United States. Resveratrol is a potent antioxidant found in grapes that inhibits several types of cancer, including lung cancer. Herein, we investigated the effects of pterostilbene, an analog of resveratrol found in blueberries, on lung cancer, in vitro. We hypothesized that pterostilbene would inhibit lung cancer cell growth in vitro by a pro-apoptotic mechanism. METHODS Two lung cancer cell lines (NCI-H460 and SK-MES-1) were cultured using standard techniques. Cells were treated with increasing doses of pterostilbene (10-100 microM). Cell viability was measured at 24, 48, and 72h using a MTT assay. Apo-ONE Caspase-3/7 assay was used to evaluate caspase activity. T-test and two-way ANOVA were used for statistical analysis. RESULTS Pterostilbene significantly decreased cell viability in lung cancer cells in a concentration- and time-dependent manner (P<0.001). Concentrations greater than 20 microM of pterostilbene produced significant growth inhibition by 72h (P<0.001). Apoptosis and caspase-3/7 activity were significantly increased by pterostilbene treatment (P<0.05). CONCLUSIONS Pterostilbene inhibits growth via apoptosis induction in vitro. Further in vitro mechanistic studies and in vivo experiments are warranted to determine the potential role for pterostilbene in lung cancer treatment or prevention.

Inhibitory effects of (-)-epigallocatechin-3-gallate and pterostilbene on pancreatic cancer growth in vitro

BACKGROUND It has been previously shown that the naturally occurring antioxidant (-)-epigallocatechin-3-gallate (EGCG), found in green tea, and pterostilbene, a stilbenoid derived from blueberries, inhibit pancreatic cancer in vitro when used individually. We hypothesized that the combination of EGCG and pterostilbene would reveal additive effects in vitro. METHODS Using the pancreatic cancer cell lines MIA PaCa-2 and PANC-1, efficacy and synergism were evaluated for cell proliferation and viability (3-(4,5-dimethyltiazol-2-y1)-2,5-diphenltetrazolium bromide assays, cell cycle analysis) and mitochondrial apoptosis (mitochondrial depolarization, cytochrome C release, caspase-3/7 activity, cell death detection using enzyme-linked immunosorbent assay). RESULTS Cell proliferation assays revealed significant additive antiproliferative effects with pterostilbene and EGCG in both cell lines at the later, 72-h, point (P < 0.05). MIA underwent S-phase arrest with the combination (10-12% increase); however, cell cycle arrest was not observed in PANC. The combination induced mitochondrial depolarization and upregulated cytochrome C (P < 0.05) in MIA, but these effects were not observed in PANC. EGCG increased caspase-3/7 in MIA; however, the combination did not significantly increase the activity in either cell line (P < 0.05). Apoptosis was only observed in PANC (P < 0.05). The reduction in proliferation in MIA in the 3-(4,5-dimethyltiazol-2-y1)-2,5-diphenltetrazolium bromide assays with the combination indicated that cell death occurs, possibly through another mechanism. CONCLUSIONS Our results are encouraging regarding the future use of EGCG and pterostilbene to improve traditional pancreatic cancer therapies. In conclusion, EGCG and pterostilbene have additive, antiproliferative effects in vitro and alter the apoptotic mechanisms in both cell lines by modulation at different points in the mechanism.

The antiproliferative effects of pterostilbene on breast cancer in vitro are via inhibition of constitutive and leptin-induced Janus kinase/signal transducer and activator of transcription activation

BACKGROUND The hormone leptin is implicated in breast carcinogenesis in obese women. One mechanism is through its activation of Janus kinase/signal transducer and activator of transcription (JAK/STAT3) and apoptosis dysregulation. We have shown that the antioxidant pterostilbene inhibits proliferation and induces apoptosis in breast cancer. Therefore, the goal of this study was to evaluate the effect of pterostilbene on cell proliferation and JAK/STAT3 signaling in leptin-stimulated breast cancer. METHODS Breast cancer cells were treated with leptin alone or in combination with pterostilbene. Detection of cell proliferation and JAK/STAT3 signaling were performed using enzyme-linked immunosorbent assay protocols. Statistical analysis was performed with analysis of variance and Tukey post hoc analysis. RESULTS Pterostilbene suppresses constitutive as well as leptin-induced JAK/STAT3 activation. Pterostilbene treatment also inhibited leptin-induced cell proliferation. CONCLUSIONS Pterostilbene has an inhibitory effect on leptin-stimulated breast cancer in vitro through reduction of cell proliferation and JAK/STAT3 signaling, a critical regulatory component of tumorigenesis in obesity-related breast cancer.

Honokiol produces anti-neoplastic effects on melanoma cells in vitro.

Melanoma continues to be a therapeutic challenge for the medical community owing to the scarcity of effective agents available to treat the disease. Honokiol, a traditional Chinese herb, has been proven to have anti‐cancer effects in various cell types, therefore we hypothesized it may have similar cytotoxic capabilities against melanoma cells in vitro.

Pterostilbene and tamoxifen show an additive effect against breast cancer in vitro

BACKGROUND Tamoxifen is widely used for the treatment of breast cancer. Pterostilbene, a bioavailable stilbenoid found in blueberries, has been found to inhibit breast cancer growth in vitro. It was hypothesized that combining pterostilbene with tamoxifen would produce additive effects on estrogen receptor-positive breast cancer cells. METHODS Two estrogen receptor-positive breast cancer cell lines, MCF7 and ZR-751, were pretreated with graduated doses of pterostilbene for 24 hours, followed by 5 μmol/L tamoxifen. MTT proliferation assays and Cell Death Detection ELISA(PLUS) tests evaluated cell viability and apoptosis. RESULTS MCF7 cells showed inhibition (10 and 20 μmol/L, P < .001; 30 μmol/L, P < .05) at all time points when combined with tamoxifen. ZR-751 cells showed additive reductions in cell viability (P < .001). Cell Death Detection ELISA(PLUS) indicated increased apoptosis (P < .01). CONCLUSIONS Pterostilbene shows an additive inhibitory effect on breast cancer cells when combined with tamoxifen, most likely from augmented cancer cell apoptosis.

Effects of pterostilbene on melanoma alone and in synergy with inositol hexaphosphate

BACKGROUND Pterostilbene and inositol-6-phosphate (IP6) have been shown to inhibit melanoma growth in vitro. However, pterostilbenes mechanism of action has not been clearly demonstrated. We aimed to further investigate the mechanism of action for pterostilbene and to determine whether combination treatment with IP6 produced synergistic growth inhibition. METHODS Melanoma cells were treated with increasing doses of pterostilbene, IP6, or combinations thereof. Cell viability was measured at 24 hours, 48 hours, and 72 hours using a MTT assay. Caspase activity and vascular endothelial growth factor (VEGF) production were measured using enzyme-linked immunosorbent assay (ELISA). Analysis of variance (ANOVA) and t tests were used for statistical analysis. RESULTS Pterostilbene inhibits melanoma growth in vitro in association with increased effector caspase activity. Combination treatment with inositol hexaphosphate produces synergistic growth inhibition, greater than either treatment alone. CONCLUSIONS Pterostilbene produces caspase-dependent apoptosis in melanoma cell lines. Combination treatment with IP6 produces synergistic growth inhibition. Both compounds have significant potential for a therapeutic role in the treatment of melanoma.

Pterostilbene ameliorates tumor necrosis factor alpha–induced pancreatitis in vitro

BACKGROUND We have previously demonstrated that pterostilbene, a compound in blueberries, exerts antiproliferative effects against pancreatic adenocarcinoma. However, little is known about the anti-inflammatory effects of pterostilbene in pancreatitis. Therefore, the aim of this study was to evaluate the effect of pterostilbene on inflammatory markers in an in vitro pancreatitis model. We hypothesized that pterostilbene would ameliorate the immediate inflammatory response in tumor necrosis factor alpha (TNF-α)-induced pancreatitis through downregulation of signal transducer and activator of transcription 3 (STAT3) and inhibition of TNF-α-induced secretion of lipase and proinflammatory cytokines interleukins (ILs) 1β and 6. METHODS AR42J acinar cells were pretreated with TNF-α to induce pancreatitis followed by 25 and 50 μM pterostilbene for 15 and 30 min. Secretion of lipase was quantified using a lipase assay and used as a marker of TNF-α-induced pancreatitis. Detection of STAT3, IL-1β, and IL-6 was performed using enzyme-linked immunosorbent assay. Analysis of variance and Tukey post hoc analysis were used for statistical analysis. RESULTS TNF-α increased the secretion of lipase, IL-1β, and IL-6. Pterostilbene treatment inhibited TNF-α-induced secretion of lipase (P<0.01 and P<0.001), IL-1β (P<0.05), and IL-6 (P<0.05 and P<0.01). Inhibition of STAT3 by pterostilbene occurred with treatment doses of 25 and 50 μM (P<0.001 and P<0.01). CONCLUSIONS The dietary compound pterostilbene exerts an anti-inflammatory effect in pancreatitis through downregulation of STAT3 and decreased the secretion of lipase, IL-1β, and IL-6. Pterostilbenes amelioration of pancreatitis in vitro makes it an advantageous anti-inflammatory agent. Further studies are necessary to determine pterostilbenes role as a protective or therapeutic agent in pancreatitis.

Pterostilbene Induces Mitochondrially-Derived Apoptosis in Pancreatic Cancer Cells by Increasing MnSOD Activity and Release of Cytochrome C and Smac/DIABLO

S A T A b st ra ct s significantly lower than Control Group (p<0.05). A significant reduction on liver MDA content and on mitochondrial dysfunction were observed in Diazoxide Group compared to Control Group (p<0.05). No differences in pulmonary vascular permeability and MPO activity were observed between groups. Twenty four hours after reperfusion Diazoxide Group showed a reduction of AST and ALT serum levels when compared to Control group (p<0.05). Conclusion: Diazoxide attenuates liver ischemia/reperfusion injury probably by a mechanism related to mitochondrial function preservation during liver ischemia.