Quantification of Systemic Sex Steroid Hormones in Human Serum
Breast cancer risk is partially determined by several hormone-related factors, and it has long been hypothesized that high levels of endogenous hormones, especially estrogens, may increase breast cancer risk. Aromatase inhibitors, exemestane, anastrozole, letrozole, effectively suppress estrogen levels and are used for the adjuvant treatment of postmenopausal women with hormone receptor positive breast cancer and for the treatment of advanced breast cancer in postmenopausal women. To date, two of the three AIs, exemestane and anastrozole, have demonstrated efficacy in preventing breast cancer among high-risk postmenopausal women. However, the current AI treatment is associated with unfavorable effects which will limit its acceptability for breast cancer prevention in high risk but otherwise healthy women. Finding the lowest effective dose, therefore, would potentially improve the safety profile, allowing increased uptake of AI chemoprevention among high risk women.
An NCI-funded investigator-initiated trial was conducted by the UACC investigators to determine whether lower and intermittent doses of letrozole can effectively suppress estrogen and provide a better safety profile (funded by NCI/DCP N01CN35158). In support of this trial, ACSR adapted a sensitive and specific chromatography-based mass spectrometry assay for the quantification of the serum concentrations of estradiol and estrone.
The figure below shows the percent of estrogen suppression after 24 weeks of letrozole treatment with the lower and intermittent doses (2.5 mg every Monday, Wednesday, and Friday (Q-MWF), 1.0 mg Q-MWF, or 0.25 mg Q-MWF) or with the standard dose (2.5 mg once daily (QD)). The data showed that the lower and intermittent doses of letrozole are not inferior to the standard therapy in estrogen suppression at the end of the 24-wk intervention. This information will help further develop alternative AI dosing to improve the uptake and acceptability of AI for breast cancer prevention.
Quantification of Bile Acid Composition in Human Gastric Fluid
Animal and human studies strongly implicate gastric acid and bile acid, two major components of the gastroesophageal refluxate, in the development of BE and its pathogenesis. Preclinical studies showed that supplementation with a cytoprotective bile acid, ursodeoxycholic acid (UDCA), protected esophageal cells against bile acid and low pH induced oxidative stress and modulated expression of enzymes associated with protection against oxidative stress. A NCI-funded investigator initiated clinical trial was conducted by the UACC investigators to evaluate whether supplementation with UDCA at a daily dose of 13-15 mg/kg/day for six months can modulate markers of carcinogenesis in the Barrett’s epithelium through alteration of the refluxate bile acid composition (funded by NCI/DCP N01CN35158). In support of this trial, ACSR developed a chromatography-based mass spectrometry assay for the quantification of the concentrations of bile acids and glycine- and taurine-conjugated bile acids in gastric fluid. The assay was applied to the analysis of the clinical samples.
The figure below shows the bile acid composition before and after the UDCA intervention. The data showed that UDCA intervention resulted in a significant increase in the proportion of cytoprotective bile acids (such as UDCA and glyco-UDCA) in the gastric fluid. The changes in the gastric bile acid composition will be correlated to the changes in markers of oxidative damage and cell proliferation in Barrett’s epithelium. The data will help evaluate the chemopreventive potential of UDCA for Barrett’s esophagus.
Quantification of Limonene Concentrations in Human Plasma and Breast Tissue (Cancer Prevention Research 6:577-584, 2013)
The bioactive food component, limonene, is a monoterpene found at high concentration in citrus peel oil. It has demonstrated potent anti-cancer effects in pre-clinical models of breast cancer. A NCI-funded investigator initiated clinical trial was conducted by the UACC investigators to determine the breast tissue bioavailability and clinical activity of limonene in breast cancer patients (funded by NIH/NCI R21CA123033). In support of this trial, ACSR developed chromatography-based mass spectrometry assays for the quantification of limonene and perillic acid (a major circulating metabolite of limonene) concentrations in human plasma and breast tissue. These methods were applied to the quantification of limonene and perillic acid concentrations in human plasma and breast tissue collected from this trial. The figure to the left illustrates the plasma and breast tissue concentrations of limonene and perillic acid. The results showed that limonene but not perillic acid is preferentially distributed to the breast tissue. The information is useful in focusing future translational breast cancer research on the bioactivity of limonene instead of perillic acid.
Quantification of Concentrations of Sulindac and Metabolites in Human Plasma and Nevus Samples (Cancer 118:5848-5856, 2012)
Reduced melanoma risk has been reported with regular use of nonsteroidal anti-inflammatory drugs (NSAIDs). However, the ability of NSAIDs to reach melanocytes in vivo and modulate key biomarkers in preneoplastic lesions such as atypical nevi has not been validated. A NCI-funded investigator initiated clinical trial was conducted by the UACC investigators to determine the potential chemopreventive activity of sulindac in individuals at increased risk for melanoma (funded by NCI/DCP N01CN35158). In support of this trial, ACSR developed a sensitive liquid chromatography tandem mass spectrometry assay for the quantification of sulindac and sulindac metabolites in human plasma and nevus samples.
The figure to the right shows the sulindac and sulindac metabolite concentrations in nevi and plasma samples after eight weeks of sulindac intervention (150 mg BID). The results showed that while sulindac metabolites are bioavailable in the nevi, sulindac sulfone, the pro-apoptotic metabolite, reached the target tissue concentrations similar to the respective plasma concentrations. The nevus distribution of sulindac sulfide, the metabolite responsible for COX inhibition, seems limited. The target tissue drug concentration analysis suggested that the pro-apoptotic pathway may be more biologically relevant to the activity of sulindac in melanocytic nevi.
Clinical Pharmacokinetic Evaluation of Pemetrexed (Clinical Cancer Research 18:2668-2678, 2012)
Pemetrexed (Alimta®) is broadly active in a wide variety of solid tumors. An investigator initiated Phase I, open-label clinical trial was conducted by the UACC investigators to determine the safety and tolerability of the combination of IP Alimta® plus IP cisplatin and IP paclitaxel for women with Stage III ovarian cancer. In support of this trial, ACSR adapted a sensitive liquid chromatography tandem mass spectrometry assay for the quantification of pemetrexed concentrations in human plasma and peritoneal fluid. This method was applied to the quantification of pemetrexed concentrations in plasma and IP fluid samples collected from the trial. The following figure shows the plasma and intraperitoneal concentrations of pemetrexed from two patients after intraperitoneal administration of 1000 mg/m2.
The data showed that IP administration of pemetrexed resulted in high IP fluid concentrations, 4-13 times higher than the respective plasma concentration. In addition, plasma and IP fluid concentrations sustained at elevated levels at 4 hrs after initiation of dosing. Furthermore, the resulting peak plasma concentrations were 5-6 times lower than those achieved from IV dosing at equivalent doses. The data suggested that IP dosing provided a localized high dose therapy for ovarian cancer patients.
Assessment of Markers of Oxidative Stress and Antioxidant Capacity in Current and Former Heavy Smokers (Cancer Epidemiol Biomarkers Prev 21:2193-2200, 2012)
ACSR has provided support in the quantification of markers of oxidative damage and antioxidant capacity in 146 current and former heavy smokers enrolled in a chemoprevention trial (funded by DOD PR023104) to determine the gender difference in oxidative damage and antioxidant capacity. The study showed that female smokers had significantly greater levels of 8-hydroxy-2’-deoxyguanosine (8OHdG, a marker of oxidative DNA damage) and 8-isoprostaglandin F2α (8-iso-PGF2α, a marker of oxidative lipid damage) than males but the gender difference was only significant in current smokers (CS). No gender difference was noted in erythrocyte antioxidant enzymes, although female CS 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 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. The information generated from the study may help identify appropriate high risk populations for interventions that attenuate oxidative damage, and appropriate biomarkers for clinical studies in smokers.
Assessment of Plasma Selenium Levels in Participants in Phase III Trials of Selenium for Colorectal Adenoma Prevention and Prostate Cancer Prevention (Cancer Prev Res 5:1381-93, 2012; Prostate 73:328-335, 2013)
ACSS has supported the quantification of plasma selenium levels for ongoing Phase III trials of selenium for colorectal adenoma prevention (NIH/NCI 1R01 CA151708-01A1) and prostate cancer prevention (NIH/NCI 5R01 CA077789). The design and baseline characteristics of participants in the colorectal adenoma trial has been published recently (Cancer Prev Res 5:1381-93, 2012). The median baseline plasma selenium levels from 1,824 participants were 135.3 ng/ml, suggesting that the study population in the current trial is in the replete range. The study will allow us to determine whether selenized yeast intervention prevents the development of premalignant colorectal adenomas. Modification of the effects of the selenium intervention by baseline plasma selenium level will also be analyzed. Similarly, the results of changes in plasma selenium levels in the prostate cancer prevention trial were published recently (Prostate 73:328-335, 2013).