Catherine Cordova

Effects of Repeated Green Tea Catechin Administration on Human Cytochrome P450 Activity

Purpose: Preclinical studies suggested that green tea or green tea catechins can modulate the activities of drug-metabolizing enzymes. We conducted this clinical study to determine the effect of repeated green tea catechin administration on human cytochrome P450 (CYP) enzyme activities. Methods: Forty-two healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, study participants received a cocktail of CYP metabolic probe drugs, including caffeine, dextromethorphan, losartan, and buspirone for assessing the activity of CYP1A2, CYP2D6, CYP2C9, and CYP3A4, respectively. Blood and urine samples before and 8 h after probe drug administration were collected to determine parent drug and metabolite concentrations for measurements of baseline CYP enzyme activities. Following the baseline evaluation, study participants underwent 4 weeks of green tea catechin intervention at a dose that contains 800 mg epigallocatechin gallate (EGCG) daily. The green tea catechin product was taken on an empty stomach to optimize the p.o. bioavailability of EGCG. The EGCG dose given in this study exceeded the amounts provided by average green tea consumption. Upon completion of the green tea catechin intervention, the postintervention CYP enzyme activities were evaluated as described above. Results: There are large between-subject variations in CYP enzyme activities in healthy individuals. Four weeks of green tea catechin intervention did not alter the phenotypic indices of CYP1A2, CYP12D6, and CYP12C9, but resulted in a 20% increase (P = 0.01) in the area under the plasma buspirone concentration-time profile, suggesting a small reduction in CYP3A4 activity. Conclusions: We conclude that repeated green tea catechin administration is not likely to result in clinically significant effects on the disposition of drugs metabolized by CYP enzymes. (Cancer Epidemiol Biomarkers Prev 2006;15(12):2473–6)

Modulation of human glutathione s-transferases by polyphenon e intervention.

Purpose: Green tea consumption has been associated with decreased risk of certain types of cancers in humans. Induction of detoxification enzymes has been suggested as one of the biochemical mechanisms responsible for the cancer-preventive effect of green tea. We conducted this clinical study to determine the effect of repeated green tea polyphenol administration on a major group of detoxification enzymes, glutathione S-transferases (GST). Methods: A total of 42 healthy volunteers underwent a 4-week washout period by refraining from tea or tea-related products. At the end of the washout period, a fasting blood sample was collected, and plasma and lymphocytes were isolated for assessment of GST activity and level. Following the baseline evaluation, study participants underwent 4 weeks of green tea polyphenol intervention in the form of a standardized Polyphenon E preparation at a dose that contains 800 mg epigallocatechin gallate (EGCG) once a day. Polyphenon E was taken on an empty stomach to optimize the oral bioavailability of EGCG. Upon completion of the intervention, samples were collected for postintervention GST assessment. Results: Four weeks of Polyphenon E intervention enhanced the GST activity in blood lymphocytes from 30.7 ± 12.2 to 35.1 ± 14.3 nmol/min/mg protein, P = 0.058. Analysis based on baseline activity showed that a statistically significant increase (80%, P = 0.004) in GST activity was observed in individuals with baseline activity in the lowest tertile, whereas a statistically significant decrease (20%, P = 0.02) in GST activity was observed in the highest tertile. In addition, Polyphenon E intervention significantly increased the GST-π level in blood lymphocytes from 2,252.9 ± 734.2 to 2,634.4 ± 1,138.3 ng/mg protein, P = 0.035. Analysis based on baseline level showed that this increase was only significant (P = 0.003) in individuals with baseline level in the lowest tertile, with a mean increase of 80%. Repeated Polyphenon E administration had minimal effects on lymphocyte GST-μ and plasma GST-α levels. There was a small but statistically significant decrease (8%, P = 0.003) in plasma GST-α levels in the highest tertile. Conclusions: We conclude that 4 weeks of Polyphenon E administration resulted in differential effects on GST activity and level based on baseline enzyme activity/level, with GST activity and GST-π level increased significantly in individuals with low baseline enzyme activity/level. This suggests that green tea polyphenol intervention may enhance the detoxification of carcinogens in individuals with low baseline detoxification capacity. (Cancer Epidemiol Biomarkers Prev 2007;16(8):1662–6)

A Phase I Pharmacokinetic and Pharmacodynamic Study of PX-12, a Novel Inhibitor of Thioredoxin-1, in Patients with Advanced Solid Tumors

Purpose: Thioredoxin-1 (Trx-1) is a cellular redox protein that promotes tumor growth, inhibits apoptosis, and up-regulates hypoxia-inducible factor-1α and vascular endothelial growth factor. Objectives of this study were to determine safety, tolerability, pharmacodynamics, and pharmacokinetics of PX-12, a small-molecule inhibitor of Trx-1. Experimental Design: Thirty-eight patients with advanced solid tumors received PX-12 at doses of 9 to 300 mg/m2, as a 1- or 3-h i.v. infusion on days 1 to 5, repeated every 3 weeks. Results: At the 300 mg/m2 dose level, one patient experienced a reversible episode of pneumonitis during the first cycle, and a second patient developed pneumonitis after the second cycle. Doses up to 226 mg/m2 were well tolerated, and grade 3/4 events were uncommon (<3% of patients). The limiting factor on this dosing schedule was pungent odor caused by expired drug metabolite, 2-butanethiol. The best response was stable disease in seven patients (126-332 days). Whereas PX-12 was not detectable following the infusion, the Cmax of its inactive metabolite, 2-mercaptoimidazole, increased linearly with dose. PX-12 treatment lowered plasma Trx-1 concentrations in a dose-dependent manner. Conclusions: PX-12, the first Trx-1 inhibitor to enter clinical trials, was tolerated up to a dose of 226 mg/m2 by a 3-h infusion. Based on pharmacodynamic and pharmacokinetic data, a trial of prolonged infusion schedule of PX-12 has been initiated.

Human breast tissue disposition and bioactivity of limonene in women with early stage breast cancer

Limonene is a bioactive food component found in citrus peel oil that has shown chemopreventive and chemotherapeutic activities in preclinical studies. We conducted an open-label pilot clinical study to determine the human breast tissue disposition of limonene and its associated bioactivity. We recruited 43 women with newly diagnosed operable breast cancer electing to undergo surgical excision to take 2 grams of limonene daily for two to six weeks before surgery. Blood and breast tissue were collected to determine drug/metabolite concentrations and limonene-induced changes in systemic and tissue biomarkers of breast cancer risk or carcinogenesis. Limonene was found to preferentially concentrate in the breast tissue, reaching high tissue concentration (mean = 41.3 μg/g tissue), whereas the major active circulating metabolite, perillic acid, did not concentrate in the breast tissue. Limonene intervention resulted in a 22% reduction in cyclin D1 expression (P = 0.002) in tumor tissue but minimal changes in tissue Ki67 and cleaved caspase-3 expression. No significant changes in serum leptin, adiponectin, TGF-β1, insulin-like growth factor binding protein-3 (IGFBP-3), and interleukin-6 (IL-6) levels were observed following limonene intervention. There was a small but statistically significant postintervention increase in insulin-like growth factor I (IGF-I) levels. We conclude that limonene distributed extensively to human breast tissue and reduced breast tumor cyclin D1 expression that may lead to cell-cycle arrest and reduced cell proliferation. Furthermore, placebo-controlled clinical trials and translational research are warranted to establish limonenes role for breast cancer prevention or treatment. Cancer Prev Res; 6(6); 577–84. ©2013 AACR.

Gender Difference in Systemic Oxidative Stress and Antioxidant Capacity in Current and Former Heavy Smokers

Background: Several studies suggested that women may be more susceptible to oxidative damage induced by cigarette smoking, but the role of smoking status and antioxidant capacity in gender difference in susceptibility to oxidative damage has not been well studied. Methods: We conducted a cross-sectional analysis of the baseline data from 146 current and former heavy smokers enrolled in a chemoprevention trial to determine the gender difference in oxidative damage and antioxidant capacity. Oxidative DNA and lipid damage were assessed by urinary 8-hydroxy-2′-deoxyguanosine (8OHdG) and 8-isoprostaglandin F2α (8-iso-PGF2α), respectively. The erythrocyte antioxidant enzymes and serum fat-soluble antioxidants were measured to assess antioxidant capacity. Results: Female smokers had significantly greater levels of 8OHdG and 8-iso-PGF2α than males but the gender difference was only significant in current smokers. No gender difference was noted in erythrocyte antioxidant enzymes, although female current smokers had significantly lower or a trend for lower antioxidant enzymes. Female smokers had higher serum β-carotene than males. Biomarkers of oxidative damage did not correlate significantly with the antioxidant enzymes. Urinary 8OHdG did not correlate significantly with fat-soluble antioxidants. Inverse correlations were observed between urinary 8-iso-PGF2α and several serum carotenoids. Conclusion: Female current smokers have a greater extent of oxidative damage despite having higher serum levels of fat-soluble antioxidants. Lower erythrocyte antioxidant enzymes in female current smokers may contribute to the greater extent of oxidative damage. Impact: The study may help identify appropriate high-risk populations for interventions that attenuate oxidative damage and appropriate biomarkers for clinical studies in smokers. Cancer Epidemiol Biomarkers Prev; 21(12); 2193–200. ©2012 AACR.

Bioactivity and prostate tissue distribution of metformin in a preprostatectomy prostate cancer cohort

Metformin has recently been shown to have potential to reduce prostate cancer risk. We conducted a randomized, double-blind, placebo-controlled trial to determine the modulating effects of metformin on tissue and systemic biomarkers of drug activity and its distribution into the prostate tissue. Twenty patients with prostate cancer scheduled to undergo prostatectomy were randomly assigned to receive either extended-release metformin or placebo for a median of 34 days before surgery. Prostatectomy and serum samples were analyzed for metformin concentrations, serum biomarkers of drug activity (prostate-specific antigen, insulin, insulin-like growth factor-1, insulin-like growth factor binding protein 3, sex hormone-binding globulin, and testosterone) and tissue biomarkers of proliferation, apoptosis, cell cycle regulation, and mTOR inhibition. For participants in the metformin arm, the prostate tissue and serum metformin concentrations ranged from 0.88 to 51.2 &mgr;g/g tissue and from not detectable to 3.6 &mgr;g/ml, respectively. There were no differences between the two groups in either the postintervention tissue biomarker expression in the prostatectomy tissue or pre to postintervention changes in serum biomarkers. We conclude that metformin distributes to human prostate tissue, suggesting that metformin could exert its effects directly on tissue targets. However, there was no difference in tissue and systemic drug effect biomarkers between the two treatment arms. Future studies with longer intervention duration and larger sample size should be considered in order to evaluate the potential of metformin for prostate cancer prevention.

Abstract 3558: A pilot clinical study of limonene in women with early stage breast cancer: Effects of short-term treatment on tissue limonene disposition and serum markers

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: Limonene is a highly lipophilic monoterpene found in citrus peel oil that has demonstrated anticancer properties in preclinical studies. The purpose of this study was to evaluate whether limonene and its primary metabolite perillic acid (PA) would distribute extensively to the breast tissue and reach an effective drug concentration. Secondary endpoints included evaluation of changes in cancer-related biomarkers in plasma and tissue. Methods: Participants (N = 40) with newly diagnosed stage 0 - 2 breast cancer took 2 grams daily of oral limonene for 2 - 6 weeks (21.5 ± 8.8 days) prior to planned surgical tumor resection. Blood was drawn pre/post intervention for measurement of serum concentration of limonene, PA, and protein biomarkers, as well as to assess toxicity profiles. A small piece of breast tissue adjacent to the tumor mass was also collected for analysis of limonene and PA levels. Limonene and PA levels in tissue and serum were analyzed using specific chromatography-based assays. Results: Limonene was found to preferentially concentrate in breast tissue (332.3 + 336.1 uM) versus plasma (0.49 + 0.67 uM) with tissue-to-plasma concentration ratio (TPCR) of 1,667 + 312.5 (P<0.001). PA did not concentrate in breast tissue (5.73 + 10.28 uM) versus plasma (3.89 + 6.81 uM) with TPCR of 1.4 + 0.56. Post-intervention serum levels of leptin, adiponectin, TGF-beta1, IGFBP-3 and IL-6 were unchanged from baseline. There was a small but statistically significant post-intervention increase in IGF-1, however the change was no longer significant after adjustment for number of days on agent. Possibly or probably related adverse events were primarily GI-related and were not dose-limiting. No clinically significant changes in complete blood count, renal, hepatic or other blood chemistry studies were noted. Analysis of the intervention effects on tissue biomarkers of proliferation, apoptosis, and cell cycle regulation is ongoing. Discussion: Oral limonene preferentially concentrates in the breast tissue and has a favorable side effect profile. PA does not readily concentrate in breast tissue when administered as oral limonene. Short-term limonene intervention resulted in minimal changes in systemic biomarkers. Further clinical trials with a longer intervention are necessary to establish limonenes potential role as a chemopreventive agent in breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3558. doi:1538-7445.AM2012-3558