Association between urinary prostaglandin E2 metabolite and breast cancer risk: a prospective, case-cohort study of postmenopausal women

Regulation of inflammation in cancer by dietary eicosanoids

BACKGROUND

Cancer is a major burden of disease worldwide and increasing evidence shows that inflammation contributes to cancer development and progression. Eicosanoids are derived from dietary polyunsaturated fatty acids, such as arachidonic acid (AA), and are mainly produced by a series of enzymatic pathways that include cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P-450 epoxygenase (CYP). Eicosanoids consist of at least several hundred individual molecules and play important roles in the inflammatory response and inflammation-related cancers.

SCOPE AND APPROACH

Dietary sources of AA and biosynthesis of eicosanoids from AA through different metabolic pathways are summarized. The bioactivities of eicosanoids and their potential molecular mechanisms on inflammation and cancer are revealed. Additionally, current challenges and limitations in eicosanoid research on inflammation-related cancer are discussed.

KEY FINDINGS AND CONCLUSIONS

Dietary AA generates a large variety of eicosanoids, including prostaglandins, thromboxane A2, leukotrienes, cysteinyl leukotrienes, lipoxins, hydroxyeicosatetraenoic acids (HETEs), and epoxyeicosatrienoic acids (EETs). Eicosanoids exert different bioactivities and mechanisms involved in the inflammation and related cancer developments. A deeper understanding of eicosanoid biology may be advantageous in cancer treatment and help to define cellular targets for further therapeutic development.

Linking Physical Activity to Breast Cancer via Inflammation, Part 2: The Effect of Inflammation on Breast Cancer Risk

This review synthesized and appraised the evidence for an effect of inflammation on breast cancer risk. Systematic searches identified prospective cohort and Mendelian randomization studies relevant to this review. Meta-analysis of 13 biomarkers of inflammation were conducted to appraise the evidence for an effect breast cancer risk; we examined the dose-response of these associations. Risk of bias was evaluated using the ROBINS-E tool and the quality of evidence was appraised with Grading of Recommendations Assessment, Development, and Evaluation. Thirty-four observational studies and three Mendelian randomization studies were included. Meta-analysis suggested that women with the highest levels of C-reactive protein (CRP) had a higher risk of developing breast cancer [risk ratio (RR) = 1.13; 95% confidence interval (CI), 1.01-1.26] compared with women with the lowest levels. Women with highest levels of adipokines, particularly adiponectin (RR = 0.76; 95% CI, 0.61-0.91) had a reduced breast cancer risk, although this finding was not supported by Mendelian randomization analysis. There was little evidence of an effect of cytokines, including TNFα and IL6, on breast cancer risk. The quality of evidence for each biomarker ranged from very low to moderate. Beyond CRP, the published data do not clearly support the role of inflammation in the development of breast cancer.

Benign Breast Disease, NSAIDs, and Postmenopausal Breast Cancer Risk in the CPS-II Cohort

ABSTRACT

Nonsteroidal anti-inflammatory agents (NSAID) are associated with modest inconsistent reductions in breast cancer risk in population-based cohorts, whereas two focused studies of patients with benign breast disease (BBD) have found lower risk with NSAID use. Given that BBD includes fibroinflammatory lesions linked to elevated breast cancer risk, we assessed whether NSAID use was associated with lower breast cancer risk among patients with BBD.Participants were postmenopausal women in the Cancer Prevention Study-II (CPS-II), a prospective study of cancer incidence and mortality, who completed follow-up surveys in 1997 with follow-up through June 30, 2015. History of BBD, NSAID use, and covariate data were updated biennially. This analysis included 23,615 patients with BBD and 36,751 patients with non-BBD, including 3,896 incident breast cancers over an average of 12.72 years of follow-up among participants. NSAID use, overall and by formulation, recency, duration, and pills per month was analyzed versus breast cancer risk overall and by BBD status using multivariable-adjusted Cox models; BBD status and NSAID use were modeled as time-dependent exposures.Patients with BBD who reported using NSAIDs experienced lower breast cancer risk (HR, 0.87; 95% CI, 0.78-0.97), with similar effects for estrogen receptor (ER)-positive breast cancers [HR, 0.85; 95% confidence interval (CI), 0.74-0.97] and ER-negative breast cancers (HR, 0.87; 95% CI, 0.59-1.29); among women without BBD, NSAID use was unrelated to risk (HR, 1.02; 95% CI, 0.92-1.13; Pinteraction = 0.04). Associations stratified by age, obesity, menopausal hormone use, and cardiovascular disease were similar.Among patients with BBD, NSAID use appears linked to lower breast cancer risk. Further studies to assess the value of NSAID use among patients with BBD are warranted.

PREVENTION RELEVANCE

We examined whether NSAID use, a modifiable exposure, is associated with breast cancer risk in postmenopausal women from the Cancer Prevention Study-II with self-reported benign breast disease, an often inflammatory condition associated with higher rates of breast cancer.

Towards defining morphologic parameters of normal parous and nulliparous breast tissues by artificial intelligence

BACKGROUND

Breast terminal duct lobular units (TDLUs), the source of most breast cancer (BC) precursors, are shaped by age-related involution, a gradual process, and postpartum involution (PPI), a dramatic inflammatory process that restores baseline microanatomy after weaning. Dysregulated PPI is implicated in the pathogenesis of postpartum BCs. We propose that assessment of TDLUs in the postpartum period may have value in risk estimation, but characteristics of these tissues in relation to epidemiological factors are incompletely described.

METHODS

Using validated Artificial Intelligence and morphometric methods, we analyzed digitized images of tissue sections of normal breast tissues stained with hematoxylin and eosin from donors ≤ 45 years from the Komen Tissue Bank (180 parous and 545 nulliparous). Metrics assessed by AI, included: TDLU count; adipose tissue fraction; mean acini count/TDLU; mean dilated acini; mean average acini area; mean "capillary" area; mean epithelial area; mean ratio of epithelial area versus intralobular stroma; mean mononuclear cell count (surrogate of immune cells); mean fat area proximate to TDLUs and TDLU area. We compared epidemiologic characteristics collected via questionnaire by parity status and race, using a Wilcoxon rank sum test or Fisher's exact test. Histologic features were compared between nulliparous and parous women (overall and by time between last birth and donation [recent birth: ≤ 5 years versus remote birth: > 5 years]) using multivariable regression models.

RESULTS

Normal breast tissues of parous women contained significantly higher TDLU counts and acini counts, more frequent dilated acini, higher mononuclear cell counts in TDLUs and smaller acini area per TDLU than nulliparas (all multivariable analyses p < 0.001). Differences in TDLU counts and average acini size persisted for > 5 years postpartum, whereas increases in immune cells were most marked ≤ 5 years of a birth. Relationships were suggestively modified by several other factors, including demographic and reproductive characteristics, ethanol consumption and breastfeeding duration.

CONCLUSIONS

Our study identified sustained expansion of TDLU numbers and reduced average acini area among parous versus nulliparous women and notable increases in immune responses within five years following childbirth. Further, we show that quantitative characteristics of normal breast samples vary with demographic features and BC risk factors.

Predicting Ulcerative Colitis Relapse in Clinical Remission With Fecal Immunochemical Occult Blood Test or Prostaglandin E-Major Urinary Metabolite

INTRODUCTION

The fecal immunochemical occult blood test (FIT) and prostaglandin E-major urinary metabolite (PGE-MUM) have been reported to predict the relapse of ulcerative colitis (UC) during remission. In this study, we directly compared FIT and PGE-MUM in predicting relapse and examined the effect of disease duration on these biomarkers.

METHODS

Measurements of 2 biomarkers and endoscopic examination were performed in 73 patients with UC in remission. The patients were followed up for 12 months, and clinical relapse was evaluated. In addition, we divided the patients into long-term disease duration and short-term disease duration groups for analysis.

RESULTS

Twenty-one patients (28.8%) relapsed within 12 months. FIT and PGE-MUM levels were significantly higher in the relapsed group than in the remission group. Cutoff values of FIT and PGE-MUM for predicting relapse using receiver operating characteristic analysis were 65.0 ng/mL (area under the curve [AUC]: 0.723) and 25.2 μg/g·Cr (AUC: 0.701), respectively. Patients with FIT ≥ 65.0 ng/mL and PGE-MUM ≥ 25.2 μg/g·Cr had a higher risk of clinical relapse. In the short-term disease duration group, the AUCs of FIT were larger than those of PGE-MUM using receiver operating characteristic analysis, in most instances. By contrast, the AUCs of PGE-MUM were larger than those of FIT in most cases in the long-term disease groups.

DISCUSSION

FIT and PEG-MUM were highly accurate in predicting clinical relapse in UC patients with short and long disease durations in remission, respectively.

Role of prostaglandin E2 in the progression of gastrointestinal cancer

Chronic inflammation is a well-established risk factor for several diseases, including cancer. It influences tumor cell biology and the type and density of immune cells in the tumor microenvironment (TME), promoting cancer development. While pro-inflammatory cytokines and chemokines modulate cancer development, emerging evidence has shown that prostaglandin E2 (PGE2) is a known mediator connecting chronic inflammation to cancerization. This review highlights recent advances in our understanding of how the elevation of PGE2 production promotes gastrointestinal cancer initiation, progression, invasion, metastasis, and recurrence, including modulation of immune checkpoint signaling and the type and density of immune cells in the tumor/tissue microenvironment.

Comparison between Prostaglandin E-major urinary metabolite and C-reactive protein levels to reflect endoscopic scores in patients with ulcerative colitis

Prostaglandin E-major urinary metabolite (PGE-MUM) and C-reactive protein (CRP) are useful biomarkers in patients with ulcerative colitis. However, whether changes in endoscopic scores over time are reflected in the values of these biomarkers has not been verified. This prospective observational study aimed to assess the relationship between changes in biomarker levels and endoscopic scores in patients with ulcerative colitis. A total of 100 colonoscopy intervals of patients with ulcerative colitis were enrolled. The relationship between variations in the Mayo endoscopic subscore over time and the accompanying changes in biomarker values were investigated. PGE-MUM levels showed a significant rise in the increased endoscopic score group (P = 0.007) and a decrease with reduced endoscopic score group (P = 0.023). CRP levels showed a significant decline with lower endoscopic values (P < 0.001); however, there was no corresponding increase with higher endoscopic scores (P = 0.141). Biomarker levels remained unchanged with stable endoscopic scores (P = 0.090 and P = 0.705). PGE-MUM levels varied significantly, and corresponded to the mucosal healing state (P = 0.019 and P = 0.009). The correlation between changes in PGE-MUM and the endoscopic score was stronger than that for CRP (r = 0.518, P < 0.001 vs. r = 0.444, P < 0.001, respectively). PGE-MUM reflected changes in endoscopic scores more accurately than CRP.

Metabolic pathways in obesity-related breast cancer

This Review focuses on the mechanistic evidence for a link between obesity, dysregulated cellular metabolism and breast cancer. Strong evidence now links obesity with the development of 13 different types of cancer, including oestrogen receptor-positive breast cancer in postmenopausal women. A number of local and systemic changes are hypothesized to support this relationship, including increased circulating levels of insulin and glucose as well as adipose tissue-derived oestrogens, adipokines and inflammatory mediators. Metabolic pathways of energy production and utilization are dysregulated in tumour cells and this dysregulation is a newly accepted hallmark of cancer. Dysregulated metabolism is also hypothesized to be a feature of non-neoplastic cells in the tumour microenvironment. Obesity-associated factors regulate metabolic pathways in both breast cancer cells and cells in the breast microenvironment, which provides a molecular link between obesity and breast cancer. Consequently, interventions that target these pathways might provide a benefit in postmenopausal women and individuals with obesity, a population at high risk of breast cancer.

Overweight Women with Breast Cancer on Chemotherapy Have More Unfavorable Inflammatory and Oxidative Stress Profiles

Chronic inflammation and redox imbalance are strongly influenced by diet and nutritional status, and both are risk factors for tumor development. This prospective study aimed to explore the associations between inflammatory and antioxidant markers and nutritional status in women with breast cancer undergoing chemotherapy. The women were evaluated at three times: T0, after the infusion of the first cycle; T1, after infusion of the intermediate cycle; and T2, after the infusion of the last chemotherapy cycle. The consumption of antioxidant nutrients and the Total Dietary Antioxidant Capacity reduced between T0 and T2 and the Dietary Inflammatory Index scores increased throughout the chemotherapy. Blood samples taken at the end of the chemotherapy showed lower levels of glutathione reductase and reduced glutathione, with greater quantification of the transcripts for Interleukin-6 and Tumor Necrosis Factor α. It should be emphasized that the Total Dietary Antioxidant Capacity is lower and the Dietary Inflammatory Index is higher in the group of overweight patients at the end of the follow-up, besides showing lower levels of the redox status, especially the plasma levels of glutathione reductase (p = 0.039). In addition, trends towards higher transcriptional levels of cytokines in peripheral blood were observed more often in overweight women than in non-overweight women. In this study of 55 women with breast cancer, nine (16%) with metastases, diet became more pro-inflammatory with fewer antioxidants during the chemotherapy. Briefly, we have shown that chemotherapy is critical for high-risk overweight women due to their reduced intake of antioxidant nutrients, generating greater inflammatory and oxidative stress profiles, suggesting the adoption of healthier dietary practices by women with breast cancer throughout their chemotherapy.

Aspirin in the Prevention of Colorectal Neoplasia

High-quality evidence indicates that regular use of aspirin is effective in reducing the risk for precancerous colorectal neoplasia and colorectal cancer (CRC). This has led to US and international guidelines recommending aspirin for the primary prevention of CRC in specific populations. In this review, we summarize key questions that require addressing prior to broader adoption of aspirin-based chemoprevention, review recent evidence related to the benefits and harms of aspirin use among specific populations, and offer a rationale for precision prevention approaches. We specifically consider the mechanistic implications of evidence showing differences in aspirin's effects according to age, the potential role of modifiable mechanistic biomarkers for personalizing prevention, and emerging evidence that the gut microbiota may offer novel aspirin-associated preventive targets to reduce high-risk neoplasia.

Effect of Low-dose and Standard-dose Aspirin on PGE2 Biosynthesis Among Individuals with Colorectal Adenomas: A Randomized Clinical Trial

Low-dose aspirin is recommended by the U.S. Preventive Services Task Force for primary prevention of colorectal cancer in certain individuals. However, broader implementation will require improved precision prevention approaches to identify those most likely to benefit. The major urinary metabolite of PGE2, 11α-hydroxy-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M), is a biomarker for colorectal cancer risk, but it is unknown whether PGE-M is modifiable by aspirin in individuals at risk for colorectal cancer. Adults (N = 180) who recently underwent adenoma resection and did not regularly use aspirin or NSAIDs were recruited to a double-blind, placebo-controlled, randomized trial of aspirin at 81 or 325 mg/day for 8-12 weeks. The primary outcome was postintervention change in urinary PGE-M as measured by LC/MS. A total of 169 participants provided paired urine samples for analysis. Baseline PGE-M excretion was 15.9 ± 14.6 (mean ± S.D, ng/mg creatinine). Aspirin significantly reduced PGE-M excretion (-4.7 ± 14.8) compared with no decrease (0.8 ± 11.8) in the placebo group (P = 0.015; mean duration of treatment = 68.9 days). Aspirin significantly reduced PGE-M levels in participants receiving either 81 (-15%; P = 0.018) or 325 mg/day (-28%; P < 0.0001) compared with placebo. In 40% and 50% of the individuals randomized to 81 or 325 mg/day aspirin, respectively, PGE-M reduction reached a threshold expected to prevent recurrence in 10% of individuals. These results support that aspirin significantly reduces elevated levels of PGE-M in those at increased colorectal cancer risk to levels consistent with lower risk for recurrent neoplasia and underscore the potential utility of PGE-M as a precision chemoprevention biomarker. The ASPIRED trial is registered as NCT02394769.

Effect of ulcerative colitis duration on the usefulness of immunochemical fecal occult blood test result as a disease activity biomarker

PURPOSE

The effects of ulcerative colitis (UC) duration on biomarker accuracy are unknown. We investigated the effects of UC duration on the predictive accuracy of biomarkers including immunochemical fecal occult blood test (FOBT, also known as FIT), prostaglandin E-major urinary metabolite (PGE-MUM), and C-reactive protein (CRP).

METHODS

We divided 133 samples into groups based on disease duration. Clinical and endoscopic remission was defined as Lichtiger's clinical activity index (CAI) of ≤ 4, Mayo endoscopic subscore (MES) of 0, and UC endoscopic index of severity (UCEIS) of ≤ 1.

RESULTS

FIT results were significantly correlated with all activity scores when the disease duration was < 4 years. When the disease duration was ≥ 4 years, FIT results were significantly correlated with the CAI and MES but not with UCEIS. When the disease duration was ≥ 5 years, FIT and CAI were significantly correlated, whereas FIT and MES or FIT and UCEIS did not show any correlation. When the duration was ≥ 4 years, PGE-MUM and CRP showed a significant correlation with CAI, MES, and UCEIS. Receiver operating characteristic curve analysis of biomarker data for predicting endoscopic remission showed that the accuracy of FIT was superior to that of PGE-MUM and CRP in the < 4-year group.

CONCLUSIONS

FIT is an accurate biomarker reflecting the endoscopic score until 4 years in patients with UC. However, owing to the increased number of false negatives, the usefulness of FIT may decline after 4 years. Hence, evaluation of UC in combination with other biomarkers is recommended.

The Translational Status of Cancer Liquid Biopsies

Abstract

Precision oncology aims to tailor clinical decisions specifically to patients with the objective of improving treatment outcomes. This can be achieved by leveraging omics information for accurate molecular characterization of tumors. Tumor tissue biopsies are currently the main source of information for molecular profiling. However, biopsies are invasive and limited in resolving spatiotemporal heterogeneity in tumor tissues. Alternative non-invasive liquid biopsies can exploit patient’s body fluids to access multiple layers of tumor-specific biological information (genomes, epigenomes, transcriptomes, proteomes, metabolomes, circulating tumor cells, and exosomes). Analysis and integration of these large and diverse datasets using statistical and machine learning approaches can yield important insights into tumor biology and lead to discovery of new diagnostic, predictive, and prognostic biomarkers. Translation of these new diagnostic tools into standard clinical practice could transform oncology, as demonstrated by a number of liquid biopsy assays already entering clinical use. In this review, we highlight successes and challenges facing the rapidly evolving field of cancer biomarker research.

Lay Summary

Precision oncology aims to tailor clinical decisions specifically to patients with the objective of improving treatment outcomes. The discovery of biomarkers for precision oncology has been accelerated by high-throughput experimental and computational methods, which can inform fine-grained characterization of tumors for clinical decision-making. Moreover, advances in the liquid biopsy field allow non-invasive sampling of patient’s body fluids with the aim of analyzing circulating biomarkers, obviating the need for invasive tumor tissue biopsies. In this review, we highlight successes and challenges facing the rapidly evolving field of liquid biopsy cancer biomarker research.

Prediagnostic levels of urinary 8-epi-prostaglandin F2α and prostaglandin E2 metabolite, biomarkers of oxidative damage and inflammation, and risk of hepatocellular carcinoma

Chronic inflammation and oxidative stress play pivotal roles in the pathogenesis of hepatocellular carcinoma (HCC). We conducted a nested case-control study of 347 HCC cases and 691 matched controls within a prospective cohort of 18 244 Chinese men in Shanghai, China. The concentrations of 8-epi-prostaglandin F2α (8-epi-PGF2α), a biomarker of oxidative stress, and prostaglandin E2 (PGE2) metabolite (PGE-M), a biomarker of the inflammation mediator PGE2, were determined in baseline urine samples using validated mass spectrometry assays. 8-epi-PGF2α levels were significantly higher in HCC cases than control subjects (geometric means 0.92 versus 0.80 pmol/mg creatinine, P < 0.001). The relative risks of developing HCC for the highest relative to the lowest quartile of 8-epi-PGF2α were 2.55 (95% confidence interval = 1.62-4.01, Ptrend < 0.001). This positive 8-epi-PGF2α-HCC risk association was independent of smoking status, alcohol consumption and hepatitis B or liver cirrhosis and was present 10 years before the clinical manifestation of HCC. This study did not find any significant association between urinary PEG-M and HCC risk. This study provides direct evidence in support of the critical role of oxidative stress in the development of HCC regardless of its underlying causes.

Urinary PGE-M Levels and Risk of Ovarian Cancer

BACKGROUND

Regular aspirin use may lower ovarian cancer risk by blocking the cyclooxygenase enzymes, resulting in lower expression of prostaglandins, including prostaglandin E2 (PGE2). We evaluated whether higher prediagnosis PGE-M (a urinary biomarker of PGE2) was associated with increased ovarian cancer risk in three prospective cohorts.

METHODS

We conducted a case-control study nested in the Nurses' Health Study (NHS), NHSII, and Shanghai Women's Health Study. Our analyses included 304 cases of epithelial ovarian cancer diagnosed from 1996 to 2015 and 600 matched controls. We measured urinary PGE-M using LC/MS with normalization to creatinine. Measures from each study were recalibrated to a common standard. We estimated ORs and 95% confidence intervals (CI) using conditional logistic regression, with PGE-M levels modeled in quartiles. Multivariable models were adjusted for ovarian cancer risk factors.

RESULTS

There was no evidence of an association between urinary PGE-M levels and ovarian cancer risk for women with PGE-M levels in the top versus bottom quartile (OR = 0.80; 95% CI, 0.51-1.27; P _trend = 0.37). We did not observe heterogeneity by histotype (P = 0.53), and there was no evidence of effect modification by body mass index (P _interaction = 0.82), aspirin use (P _interaction = 0.59), or smoking (P _interaction = 0.14).

CONCLUSIONS

Prediagnosis urinary PGE-M levels were not significantly associated with ovarian cancer risk. Larger sample sizes are needed to consider a more modest association and to evaluate associations for specific tumor subtypes.

IMPACT

Systemic prostaglandin levels do not appear strongly associated with ovarian cancer risk. Future research into aspirin use and ovarian cancer risk should consider local prostaglandins and prostaglandin-independent mechanisms.

Targeting lipid mediators in cancer biology

Bioactive lipids are essential components of human cells and tissues. As discussed in this review, the cancer lipidome is diverse and malleable, with the ability to promote or inhibit cancer pathogenesis. Targeting lipids within the tumor and surrounding microenvironment may be a novel therapeutic approach for treating cancer patients. Additionally, the emergence of a novel super-family of lipid mediators termed specialized pro-resolving mediators (SPMs) has revealed a new role for bioactive lipid mediators in the resolution of inflammation in cancer biology. The role of SPMs in cancer holds great promise in our understanding of cancer pathogenesis and can ultimately be used in future cancer diagnostics and therapy.

Role of prostanoids in gastrointestinal cancer

Chronic inflammation is a risk factor for gastrointestinal cancer and other diseases. Most studies have focused on cytokines and chemokines as mediators connecting chronic inflammation to cancer, whereas the involvement of lipid mediators, including prostanoids, has not been extensively investigated. Prostanoids are among the earliest signaling molecules released in response to inflammation. Multiple lines of evidence suggest that prostanoids are involved in gastrointestinal cancer. In this Review, we discuss how prostanoids impact gastrointestinal cancer development. In particular, we highlight recent advances in our understanding of how prostaglandin E2 induces the immunosuppressive microenvironment in gastrointestinal cancers.

Postmenopausal breast cancer and oestrogen associations with the IgA-coated and IgA-noncoated faecal microbiota

Background:

The diversity and composition of the gut microbiota may affect breast cancer risk by modulating systemic levels of oestrogens and inflammation. The current investigation tested this hypothesis in postmenopausal women by identifying breast cancer associations with an inflammation marker, oestrogen levels, and faecal microbes that were or were not coated with mucosal immunoglobulin A (IgA).

Methods:

In this population-based study, we compared 48 postmenopausal breast cancer cases (75% stage 0–1, 88% oestrogen-receptor positive) to 48 contemporaneous, postmenopausal, normal-mammogram, age-matched controls. Microbiota metrics employed 16S rRNA gene amplicon sequencing from IgA-coated and -noncoated faecal microbes. High-performance liquid chromatography/mass spectrometry (HPLC/MS) and radioimmunoassay were used to quantify urine prostaglandin E metabolite (PGE-M), a possible marker of inflammation; urine oestrogens and oestrogen metabolites were quantified by HPLC/MS-MS.

Results:

Women with pre-treatment breast cancer had non-significantly elevated oestrogen levels; controls’ (but not cases’) oestrogens were directly correlated with their IgA-negative microbiota alpha diversity (P=0.012). Prostaglandin E metabolite levels were not associated with case status, oestrogen levels, or alpha diversity. Adjusted for oestrogens and other variables, cases had significantly reduced alpha diversity and altered composition of both their IgA-positive and IgA-negative faecal microbiota. Cases’ faecal microbial IgA-positive imputed Immune System Diseases metabolic pathway genes were increased; also, cases’ IgA-positive and IgA-negative imputed Genetic Information Processing pathway genes were decreased (P⩽0.01).

Conclusions:

Compared to controls, breast cancer cases had significant oestrogen-independent associations with the IgA-positive and IgA-negative gut microbiota. These suggest that the gut microbiota may influence breast cancer risk by altered metabolism, oestrogen recycling, and immune pressure.

Regression analysis for secondary response variable in a case-cohort study

Case-cohort study design has been widely used for its cost-effectiveness. In any real study, there are always other important outcomes of interest beside the failure time that the original case-cohort study is based on. How to utilize the available case-cohort data to study the relationship of a secondary outcome with the primary exposure obtained through the case-cohort study is not well studied. In this article, we propose a non-parametric estimated likelihood approach for analyzing a secondary outcome in a case-cohort study. The estimation is based on maximizing a semiparametric likelihood function that is built jointly on both time-to-failure outcome and the secondary outcome. The proposed estimator is shown to be consistent, efficient, and asymptotically normal. Finite sample performance is evaluated via simulation studies. Data from the Sister Study is analyzed to illustrate our method.

ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED): a study protocol for a randomized controlled trial

BACKGROUND

Although aspirin is recommended for the prevention of colorectal cancer, the specific individuals for whom the benefits outweigh the risks are not clearly defined. Moreover, the precise mechanisms by which aspirin reduces the risk of cancer are unclear. We recently launched the ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED) trial to address these uncertainties.

METHODS/DESIGN

ASPIRED is a prospective, double-blind, multidose, placebo-controlled, biomarker clinical trial of aspirin use in individuals previously diagnosed with colorectal adenoma. Individuals (n = 180) will be randomized in a 1:1:1 ratio to low-dose (81 mg/day) or standard-dose (325 mg/day) aspirin or placebo. At two study visits, participants will provide lifestyle, dietary and biometric data in addition to urine, saliva and blood specimens. Stool, grossly normal colorectal mucosal biopsies and cytology brushings will be collected during a flexible sigmoidoscopy without bowel preparation. The study will examine the effect of aspirin on urinary prostaglandin metabolites (PGE-M; primary endpoint), plasma inflammatory markers (macrophage inhibitory cytokine-1 (MIC-1)), colonic expression of transcription factor binding (transcription factor 7-like 2 (TCF7L2)), colonocyte gene expression, including hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) and those that encode Wnt signaling proteins, colonic cellular nanocytology and oral and gut microbial composition and function.

DISCUSSION

Aspirin may prevent colorectal cancer through multiple, interrelated mechanisms. The ASPIRED trial will scrutinize these pathways and investigate putative mechanistically based risk-stratification biomarkers.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02394769 . Registered on 16 March 2015.

Urine Eicosanoids in the Metabolic Abnormalities, Telmisartan, and HIV Infection (MATH) Trial

OBJECTIVES

Arachidonic acid metabolites (eicosanoids) reflect oxidative stress and vascular health and have been associated with anthropometric measures and sex differences in cross-sectional analyses of HIV-infected (HIV+) persons. Telmisartan is an angiotensin receptor blocker and PPAR-γ agonist with potential anti-inflammatory and metabolic benefits. We assessed telmisartan's effects on urine eicosanoids among HIV+ adults with central adiposity on suppressive antiretroviral therapy enrolled in a prospective clinical trial.

METHODS

Thirty-five HIV+ adults (15 women; 20 men) completed 24 weeks of open-label oral telmisartan 40mg daily. Lumbar computed tomography quantified visceral (VAT) and subcutaneous (SAT) abdominal adipose tissue. Urine F2-isoprostane (F2-IsoP), prostaglandin E2 (PGE-M), prostacyclin (PGI-M), and thromboxane B2 (TxB-M) were quantified at baseline and 24 weeks using gas/liquid chromatography-mass spectroscopy. Mann-Whitney-U tests compared sub-group differences; Spearman's rho assessed correlations between clinical factors and eicosanoid levels.

RESULTS

Median PGE-M increased on telmisartan (p<0.01), with greater changes in men (+4.1 [p = 0.03] vs. +1.0 ng/mg cr in women; between-group p = 0.25) and participants losing >5% VAT (+3.7 ng/mg cr, p<0.01) and gaining >5% SAT (+1.7 ng/mg cr, p = 0.04). Median baseline F2-IsoP and TxB-M were slightly higher in women (both between-group p = 0.08) and did not change on telmisartan.

CONCLUSIONS

Urine PGE-M increased with 24 weeks of telmisartan in virally suppressed, HIV+ adults with central adiposity. Associations with favorable fat redistribution suggest increased PGE-M may reflect a beneficial response.

Obesity-associated cancer risk: the role of intestinal microbiota in the etiology of the host proinflammatory state

Obesity increases the risks of many cancers. One important mechanism behind this association is the obesity-associated proinflammatory state. Although the composition of the intestinal microbiome undoubtedly can contribute to the proinflammatory state, perhaps the most important aspect of host-microbiome interactions is host exposure to components of intestinal bacteria that stimulate inflammatory reactions. Systemic exposures to intestinal bacteria can be modulated by dietary factors through altering both the composition of the intestinal microbiota and the absorption of bacterial products from the intestinal lumen. In particular, high-fat and high-energy diets have been shown to facilitate absorption of bacterial lipopolysaccharide (LPS) from intestinal bacteria. Biomarkers of bacterial exposures that have been measured in blood include LPS-binding protein, sCD14, fatty acids characteristic of intestinal bacteria, and immunoglobulins specific for bacterial LPS and flagellin. The optimal strategies to reduce these proinflammatory exposures, whether by altering diet composition, avoiding a positive energy balance, or reducing adipose stores, likely differ in each individual. Biomarkers that assess systemic bacterial exposures therefore should be useful to (1) optimize and personalize preventive approaches for individuals and groups with specific characteristics and to (2) gain insight into the possible mechanisms involved with different preventive approaches.

Systemic Levels of Estrogens and PGE2 Synthesis in Relation to Postmenopausal Breast Cancer Risk

Background: Prostaglandin E₂ (PGE₂) induces aromatase expression in adipose tissue, leading to increased estrogen production that may promote the development and progression of breast cancer. However, few studies have simultaneously investigated systemic levels of PGE₂ and estrogen in relation to postmenopausal breast cancer risk.Methods: Here, we determined urinary estrogen metabolites (EM) using mass spectrometry in a case-cohort study (295 incident breast cancer cases and 294 subcohort members), and using linear regression estimated the effect of urinary levels of a major PGE₂ metabolite (PGE-M) on EMs. HRs for the risk of developing breast cancer in relation to PGE-M and EMs were compared between Cox regression models with and without mutual adjustment.Results: PGE-M was a significant predictor of estrone (E1), but not estradiol (E2) levels in multivariable analysis. Elevated E2 levels were associated with an increased risk of developing breast cancer [HR_Q5vs.Q1, 1.54; 95% confidence interval (CI), 1.01-2.35], and this association remained unchanged after adjustment for PGE-M (HR_Q5vs.Q1, 1.52; 95% CI, 0.99-2.33). Similarly, elevated levels of PGE-M were associated with increased risk of developing breast cancer (HR_Q4vs.Q1, 2.01; 95% CI, 1.01-4.29), and this association was only nominally changed after consideration of E1 or E2 levels.Conclusions: Urinary levels of PGE-M and estrogens were independently associated with future risk of developing breast cancer among these postmenopausal women.Impact: Increased breast cancer risk associated with PGE-M might not be fully explained by the estrogens-breast cancer association alone but also by additional effects related to inflammation. Cancer Epidemiol Biomarkers Prev; 26(3); 383-8. ©2016 AACR.

Obesity and Cancer Mechanisms: Tumor Microenvironment and Inflammation

Purpose There is growing evidence that inflammation is a central and reversible mechanism through which obesity promotes cancer risk and progression. Methods We review recent findings regarding obesity-associated alterations in the microenvironment and the local and systemic mechanisms through which these changes support tumor growth. Results Locally, hyperadiposity is associated with altered adipose tissue function, adipocyte death, and chronic low-grade inflammation. Most individuals who are obese harbor inflamed adipose tissue, which resembles chronically injured tissue, with immune cell infiltration and remodeling. Within this distinctly altered local environment, several pathophysiologic changes are found that may promote breast and other cancers. Consistently, adipose tissue inflammation is associated with a worse prognosis in patients with breast and tongue cancers. Systemically, the metabolic syndrome, including dyslipidemia and insulin resistance, occurs in the setting of adipose inflammation and operates in concert with local mechanisms to sustain the inflamed microenvironment and promote tumor growth. Importantly, adipose inflammation and its protumor consequences can be found in some individuals who are not considered to be obese or overweight by body mass index. Conclusion The tumor-promoting effects of obesity occur at the local level via adipose inflammation and associated alterations in the microenvironment, as well as systemically via circulating metabolic and inflammatory mediators associated with adipose inflammation. Accurately characterizing the obese state and identifying patients at increased risk for cancer development and progression will likely require more precise assessments than body mass index alone. Biomarkers of adipose tissue inflammation would help to identify high-risk populations. Moreover, adipose inflammation is a reversible process and represents a novel therapeutic target that warrants further study to break the obesity-cancer link.

Impacts of smoking on endocrine treatment response in a prospective breast cancer cohort

BACKGROUND

The association between smoking and breast cancer prognosis remains unclear. The purpose of this study was to investigate whether preoperative smoking was associated with prognosis in different treatment groups.

METHODS

This population-based cohort consisted of 1065 breast cancer patients without preoperative treatment included between 2002 and 2012 in Lund, Sweden. Smoking status was examined in relation to patient and tumour characteristics, and prognosis in different treatment groups.

RESULTS

At the preoperative visit, 21.0% smoked. Median follow-up time was 5.1 years. Overall, in the 1016 patients included in the survival analyses, there was no significant association between smoking and risk of breast cancer events (adjusted hazard ratio (adjHR): 1.45; 95% confidence interval (CI): 0.95-2.20). For the 309 aromatase inhibitor (AI)-treated patients ⩾50 years with oestrogen receptor-positive (ER+) tumours, smoking was associated with risk of breast cancer events (adjHR: 2.97; 95% CI: 1.44-6.13), distant metastasis (adjHR: 4.19; 95% CI: 1.81-9.72), and death (adjHR: 3.52; 95% CI: 1.59-7.81). Smoking was not associated with breast cancer events or distant metastasis in other treatment groups.

CONCLUSIONS

Preoperative smoking was only associated with an increased risk for breast cancer events and distant metastasis in AI-treated patients. If confirmed, smoking status should be taken into consideration when selecting an endocrine therapy.

Elevated Levels of Urinary PGE-M Are Found in Tobacco Users and Indicate a Poor Prognosis for Oral Squamous Cell Carcinoma Patients

Cyclooxygenase-2 (COX-2)-derived prostaglandin E2 (PGE2) plays a role in the development and progression of epithelial malignancies. Measurements of urinary PGE-M, a stable metabolite of PGE2, reflect systemic PGE2 levels. Here, we investigated whether urinary PGE-M levels were elevated in healthy tobacco users and in patients with oral squamous cell carcinoma (OSCC). Median urinary PGE-M levels were increased in healthy tobacco quid chewers [21.3 ng/mg creatinine (Cr); n = 33; P = 0.03] and smokers (32.1 ng/mg Cr; n = 31; P < 0.001) compared with never tobacco quid chewers-never smokers (18.8 ng/mg Cr; n = 30). Urinary PGE-M levels were also compared in OSCC patients versus healthy tobacco users. An approximately 1-fold increase in median urinary PGE-M level was found in OSCC patients (48.7 ng/mg Cr, n = 78) versus healthy controls (24.5 ng/mg Cr, n = 64; P < 0.001). We further determined whether baseline urinary PGE-M levels were prognostic in OSCC patients who underwent treatment with curative intent. A nearly 1-fold increase in baseline urinary PGE-M levels (64.7 vs. 33.8 ng/mg Cr, P < 0.001) was found in the group of OSCC patients who progressed (n = 37) compared with the group that remained progression free (n = 41). Patients with high baseline levels of urinary PGE-M had both worse disease-specific survival [HR, 1.01 per unit increase; 95% confidence interval (CI), 1.01-1.02; P < 0.001] and overall survival (HR, 1.01 per unit increase; 95% CI, 1.00-1.02; P = 0.03). Taken together, our findings raise the possibility that NSAIDs, prototypic inhibitors of PGE2 synthesis, may be beneficial for reducing the risk of tobacco-related aerodigestive malignancies or treating OSCC patients with high urinary PGE-M levels. Cancer Prev Res; 9(6); 428-36. ©2016 AACR.

Prostaglandin E2 Promotes Colorectal Cancer Stem Cell Expansion and Metastasis in Mice

BACKGROUND & AIMS

Inflammation may contribute to the formation, maintenance, and expansion of cancer stem cells (CSCs), which have the capacity for self-renewal, differentiation, and resistance to cytotoxic agents. We investigated the effects of the inflammatory mediator prostaglandin E2 (PGE2) on colorectal CSC development and metastasis in mice and the correlation between levels of PGE2 and CSC markers in human colorectal cancer (CRC) specimens.

METHODS

Colorectal carcinoma specimens and matched normal tissues were collected from patients at the Mayo Clinic (Scottsdale, AZ) and analyzed by mass spectrometry and quantitative polymerase chain reaction. Human primary CRC cells and mouse tumor cells were isolated using microbeads or flow cytometry and analyzed for sphere-formation and by flow cytometry assays. LS-174T cells were sorted by flow cytometry (for CD133(+)CD44(+) and CD133(-)CD44(-) cells) and also used in these assays. NOD-scidIL-2Rγ(-/-) (NSG) mice were given cecal or subcutaneous injections of LS-174T or human primary CRC cells. Apc(Min/+) mice and NSG mice with orthotopic cecal tumors were given vehicle (controls), PGE2, celecoxib, and/or Ono-AE3-208. PGE2 downstream signaling pathways were knocked down with small hairpin RNAs, expressed from lentiviral vectors in LS-174T cells, or blocked with inhibitors in human primary CRC cells.

RESULTS

Levels of PGE2 correlated with colonic CSC markers (CD133, CD44, LRG5, and SOX2 messenger RNAs) in human colorectal carcinoma samples. Administration of PGE2 to Apc(Min/+) mice increased tumor stem cells and tumor burden, compared with controls. NSG mice given PGE2 had increased numbers of cecal CSCs and liver metastases compared with controls after intracecal injection of LS-174T or human primary CRC cells. Alternatively, celecoxib, an inhibitor of prostaglandin-endoperoxide synthase 2, reduced polyp numbers in Apc(Min/+) mice, liver metastasis in NSG mice with orthotopic tumors, and numbers of CSCs in Apc(Min/+) and NSG mice. Inhibitors or knockdown of PGE2 receptor 4 (EP4), phosphoinositide 3-kinase (PI3K) p85α, extracellular signal-regulated kinase 1 (ERK1), or nuclear factor (NF)-κB reduced PGE2-induced sphere formation and expansion of LS-174T and/or human primary CRC cells. Knockdown of ERK1 or PI3K p85α also attenuated PGE2-induced activation of NF-κB in LS-174T cells. An EP4 antagonist reduced the ability of PGE2 to induce CSC expansion in orthotopic tumors and to accelerate the formation of liver metastases. Knockdown experiments showed that NF-κB was required for PGE2 induction of CSCs and metastasis in mice.

CONCLUSIONS

PGE2 induces CSC expansion by activating NF-κB, via EP4-PI3K and EP4-mitogen-activated protein kinase signaling, and promotes the formation of liver metastases in mice. The PGE2 signaling pathway therefore might be targeted therapeutically to slow CSC expansion and colorectal cancer progression.

Obesity and cancer: local and systemic mechanisms

Obesity is a leading modifiable risk factor for the development of several epithelial malignancies. In addition to increasing risk, obesity also confers worse prognosis for many cancers. Obesity represents an overall state of energy imbalance frequently associated with systemic effects including insulin resistance, altered hormone signaling, and high circulating levels of proinflammatory mediators. In addition to its systemic effects, obesity causes subclinical white adipose inflammation including increased tissue levels of proinflammatory mediators. Both local and systemic effects are likely to contribute to the development and progression of cancer. An understanding of the interplay between local and systemic alterations involved in the obesity-cancer link provides the basis for developing interventions aimed at mitigating the protumorigenic effects.

Fruit and vegetable intake and urinary levels of prostaglandin E₂ metabolite in postmenopausal women

Prostaglandin E2 (PGE2) is an inflammatory mediator that plays key roles in promoting tumor development and progression. Urinary concentration of a major PGE2 metabolite (PGE-M) has been recently proposed as a promising cancer biomarker. Using dietary intake data from 600 postmenopausal women aged 50-74 years, we examined cross-sectional relationships between fruit and vegetable intake and urinary levels of PGE-M, determined using liquid chromatography/tandem mass spectrometry. After multivariable adjustment, increasing consumption of fruits, but not vegetables, was associated with reduced levels of urinary PGE-M (P for linear trend = 0.02), with geometric means of 5.8 [95% confidence interval (CI): 5.2-6.6] in the lowest quintile versus 4.8 (95% CI: 4.3-5.4) in the highest quintile (Q5) of fruit consumption. A better quality diet, indicated by higher scores on the Healthy Eating Index, was also associated with decreased PGE-M (P for linear trend <0.01). The lack of association with vegetable intake may be related to variation in antioxidant capacities of the major dietary sources of fruits and vegetables for the study participants. Our findings suggest that urinary PGE-M may be modifiable by a healthy diet that follows current national dietary guideline. Further studies are warranted to assess potential utility of urinary PGE-M in assessing cancer prevention efficacy.

Menopause is a determinant of breast adipose inflammation

Chronic inflammation is recognized as a risk factor for the development of several malignancies. Local white adipose tissue (WAT) inflammation, defined by the presence of dead or dying adipocytes encircled by macrophages that form crown-like structures (CLS), occurs in the breasts (CLS-B) of most overweight and obese women. Previously, we showed that the presence of CLS-B is associated with elevated tissue levels of proinflammatory mediators and aromatase, the rate-limiting enzyme for estrogen biosynthesis. The associated increased levels of aromatase in the breast provide a plausible mechanistic link between WAT inflammation and estrogen-dependent breast cancers. Thus, breast WAT inflammation could be relevant for explaining the high incidence of estrogen-dependent tumors with aging despite diminished circulating estrogen levels after menopause. To explore this possibility, we determined whether menopause in addition to body mass index (BMI) is associated with breast WAT inflammation among 237 prospectively enrolled women. The presence of CLS-B and its severity (CLS-B/cm(2)) as indicators of WAT inflammation correlated with menopausal status (P = 0.008 and P < 0.001) and BMI (P < 0.001 for both). In multivariable analyses adjusted for BMI, the postmenopausal state was independently associated with the presence (P = 0.03) and severity of breast WAT inflammation (P = 0.01). Mean adipocyte size increased in association with CLS-B (P < 0.001). Our findings demonstrate that breast WAT inflammation, which is associated with elevated aromatase levels, is increased in association with the postmenopausal state independent of BMI. Breast WAT inflammation, a process that can potentially be targeted, may help to explain the high incidence of estrogen-dependent tumors in postmenopausal women.

Urinary prostaglandin E2 metabolite and pancreatic cancer risk: case-control study in urban Shanghai

Pancreatic cancer has been increasing in importance in Shanghai over the last four decades. The etiology of the disease is still unclear. Evidence suggests that the COX-2 pathway, an important component of inflammation, may be involved in the disease. We aimed to evaluate the association between urinary prostaglandin E₂ metabolite (PGE-M) level and risk of pancreatic cancer. From a recent population-based case-control study in Shanghai, 200 pancreatic ductal adenocarcinoma cases and 200 gender- and age- frequency matched controls were selected for the present analysis. Urinary PGE-M was measured with a liquid chromatography/mass spectrometric assay. Adjusted unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). A positive association was observed between PGE-M leve and pancreatic cancer risk: OR = 1.63 (95% CI 1.01–2.63) for the third tertile compared to the first. Though the interactions were not statistically significant, the associations tended to be stronger among subjects with diabetes history (OR = 3.32; 95% CI 1.20–9.19) and higher meat intake (OR = 2.12; 95% CI 1.10–4.06). The result suggests that higher urinary PGE-M level may be associated with increased risk of pancreatic ductal adenocarcinoma.

Urinary prostaglandin E2 metabolite and breast cancer risk

BACKGROUND

Levels of the cyclooxygenase 2 (COX2) enzyme are elevated in breast cancer tissue, and most COX2 effects are believed to be mediated through overproduction of prostaglandin E2 (PGE2). We evaluated associations between the primary urinary metabolite of PGE2 (PGE-M) and breast cancer risk.

METHODS

A nested case-control study of 504 cases and 1,082 controls was conducted using data from the Shanghai Women's Health Study, a large population-based prospective cohort study of 74,941 Chinese women. Urinary PGE-M was measured using a liquid chromatography/tandem mass spectrometric method. Logistic regression estimated odds ratios (OR) and 95% confidence intervals (95% CI) with adjustment for potential confounders.

RESULTS

Overall, no association between urinary PGE-M and breast cancer was detected. However, a suggestive positive association was found among postmenopausal women. In particular, a clear dose-response relationship between urinary PGE-M and breast cancer was observed among postmenopausal women with a body mass index (BMI) < 25 kg/m(2) (Plinear trend = 0.005). Among these women, risk of breast cancer increased from 1.00 (reference) to 1.06 (95% CI, 0.56-1.99), 1.50 (95% CI, 0.79-2.83), and 2.32 (95% CI, 1.24-4.41) for the lowest to highest quartiles of PGE-M, and such associations were stronger among those who were diagnosed with cancer within the first four years of sample collection. No apparent association was observed among overweight postmenopausal women (BMI ≥ 25 kg/m(2)).

CONCLUSION

High urinary PGE-M level was associated with elevated risk of breast cancer among normal weight, postmenopausal women.

IMPACT

Urinary PGE-M level may be useful for breast cancer risk assessment among normal weight, postmenopausal women. Cancer Epidemiol Biomarkers Prev; 23(12); 2866-73. ©2014 AACR.

PPARδ and PGE2 signaling pathways communicate and connect inflammation to colorectal cancer

The nuclear hormone receptor peroxisome proliferator-activated receptor δ (PPARδ) is a ligand-dependent transcription factor that is involved in fatty acid metabolism, obesity, wound healing, inflammation, and cancer. Despite decades of research, the role of PPARδ in inflammation and colorectal cancer remains unclear and somewhat controversial. Our recent work presented the first genetic evidence demonstrating that PPARδ is required for chronic colonic inflammation and colitis-associated carcinogenesis. We also found that a PPARδ downstream pathway, namely the COX-2-derived PGE₂ signaling, mediated crosstalk between tumor epithelial cells and macrophages to promote chronic inflammation and colitis-associated tumor genesis. In this brief review, we summarize recent studies on the role of PPARδ in inflammatory bowel disease (IBD) and colorectal cancer (CRC) and highlight recent advances in our understanding of how PPARδ and COX-2-drevided PGE₂ signaling coordinately promote chronic colonic inflammation and colitis-associate tumorigenesis. Elucidating the role of PPARδ in inflammation and CRC may provide a rationale for development of PPARδ antagonists as new therapeutic agents in treatment of IBD and CRC.

An inflammatory mediator, prostaglandin E2, in colorectal cancer

It is widely accepted that intake of dietary fats and chronic inflammation are risk factors for developing colorectal cancer. Arachidonic acid is a major component of animal fats, and the bioactive lipids produced from this substrate play critical roles in a variety of biologic processes, including cancer. Cyclooxygenase-derived prostaglandin E2 is a known proinflammatory lipid mediator that promotes tumor progression. Metabolism of arachidonic acid by the cyclooxygenase pathway provides one mechanism for the contribution of dietary fats and chronic inflammation to carcinogenesis. In this review, we highlight recent advances in our understanding of how a proinflammatory mediator prostaglandin E2 promotes colorectal cancer immune evasion. These findings may provide a rationale for the development of new therapeutic approaches to subvert tumor-induced immunosuppression.

Urinary PGE-M in colorectal cancer: predicting more than risk?

Progress in cancer chemoprevention has been hindered by a lack of validated biomarkers of risk and interventive response. The identification of accurate, reliable, and easily measurable risk and response biomarkers within the field of cancer prevention could dramatically alter our approach to the disease. Colorectal cancer is associated with substantial morbidity and a limited 5-year survival rate for late-stage disease. The identification of biomarkers to predict (i) those most at risk of clinically significant colorectal neoplasia in conjunction with or building upon current risk models and/or (ii) those most likely to respond to potential colorectal chemopreventive agents, such as aspirin and NSAIDs, would significantly advance colorectal cancer risk management. Urinary PGE-M is an established indicator of systemic prostaglandin E2 production and has previously been demonstrated to predict risk of advanced colorectal neoplasia in a handful of studies. In the July 2014 issue, Bezawada and colleagues confirmed those earlier risk associations and demonstrated that PGE-M can also predict responsiveness to aspirin/NSAIDs in a small subset of women undergoing lower endoscopy in the Nurse's Health Study. PGE-M has the potential to define subsets of the population that may derive greater chemopreventive benefit from NSAIDs, as well as the potential to optimize the use of expensive and/or invasive screening tests. Additional larger and more diverse prospective studies meeting the criteria for phase IV biomarker studies are needed to advance the development of PGE-M as a noninvasive biomarker of both risk and chemopreventive response in populations at risk for colorectal cancer.

A review of the application of inflammatory biomarkers in epidemiologic cancer research

Inflammation is a facilitating process for multiple cancer types. It is believed to affect cancer development and progression through several etiologic pathways, including increased levels of DNA adduct formation, increased angiogenesis, and altered antiapoptotic signaling. This review highlights the application of inflammatory biomarkers in epidemiologic studies and discusses the various cellular mediators of inflammation characterizing the innate immune system response to infection and chronic insult from environmental factors. Included is a review of six classes of inflammation-related biomarkers: cytokines/chemokines, immune-related effectors, acute-phase proteins, reactive oxygen and nitrogen species, prostaglandins and cyclooxygenase-related factors, and mediators such as transcription factors and growth factors. For each of these biomarkers, we provide a brief overview of the etiologic role in the inflammation response and how they have been related to cancer etiology and progression within the literature. We provide a discussion of the common techniques available for quantification of each marker, including strengths, weaknesses, and potential pitfalls. Subsequently, we highlight a few under-studied measures to characterize the inflammatory response and their potential utility in epidemiologic studies of cancer. Finally, we suggest integrative methods for future studies to apply multifaceted approaches to examine the relationship between inflammatory markers and their roles in cancer development.

Urinary eicosanoid metabolites in HIV-infected women with central obesity switching to raltegravir: an analysis from the women, integrase, and fat accumulation trial

Chronic inflammation is a hallmark of HIV infection. Eicosanoids reflect inflammation, oxidant stress, and vascular health and vary by sex and metabolic parameters. Raltegravir (RAL) is an HIV-1 integrase inhibitor that may have limited metabolic effects. We assessed urinary F₂-isoprostanes (F₂-IsoPs), prostaglandin E₂ (PGE-M), prostacyclin (PGI-M), and thromboxane B₂ (TxB₂) in HIV-infected women switching to RAL-containing antiretroviral therapy (ART). Thirty-seven women (RAL = 17; PI/NNRTI = 20) with a median age of 43 years and BMI 32 kg/m² completed week 24. TxB₂ increased in the RAL versus PI/NNRTI arm (+0.09 versus −0.02; P = 0.06). Baseline PGI-M was lower in the RAL arm (P = 0.005); no other between-arm cross-sectional differences were observed. In the PI/NNRTI arm, 24-week visceral adipose tissue change correlated with PGI-M (rho = 0.45; P = 0.04) and TxB₂ (rho = 0.44; P = 0.005) changes, with a trend seen for PGE-M (rho = 0.41; P = 0.07). In an adjusted model, age ≥ 50 years (N = 8) was associated with increased PGE-M (P = 0.04). In this randomized trial, a switch to RAL did not significantly affect urinary eicosanoids over 24 weeks. In women continuing PI/NNRTI, increased visceral adipose tissue correlated with increased PGI-M and PGE-M. Older age (≥50) was associated with increased PGE-M. Relationships between aging, adiposity, ART, and eicosanoids during HIV-infection require further study.

Urinary PGE-M levels are associated with risk of colorectal adenomas and chemopreventive response to anti-inflammatory drugs

Prostaglandin E2 (PGE2) promotes colorectal carcinogenesis. Overall, systemic PGE2 production can be assessed by measuring its major metabolite, PGE-M, in urine. We examined the potential role of PGE-M as a biomarker for colorectal adenoma risk and chemopreventive response to anti-inflammatory drugs. We conducted a prospective case-control study nested within the Nurses' Health Study. Among women who previously provided a urine sample, we identified 420 cases diagnosed with colorectal adenoma during follow-up and matched them to 420 endoscopy-negative controls. We measured urinary PGE-M using an LC/MS assay. Compared with women in the lowest quartile of urinary PGE-M, women in the highest quartile had a multivariate OR of 1.40 (95% confidence interval (CI), 0.92-2.14) for any adenoma; 0.91 (95% CI, 0.48-1.72) for low-risk adenoma (solitary adenoma <1 cm in greatest diameter with tubular/unspecified histology); and 1.66 (95% CI, 1.04-2.67) for high-risk adenoma (adenoma ≥1 cm in greatest diameter and/or tubulovillous, villous or high-grade dysplasia histology or multiple adenomas of any size or histology). Regular use of anti-inflammatory drugs (≥2 standard tablets of aspirin/NSAIDs per week) was associated with a significant reduction in adenoma risk (multivariate OR, 0.61; 95% CI, 0.43-0.87) in women with high baseline PGE-M (quartiles 2-4), but not low PGE-M (quartile 1).Urinary PGE-M is associated with an increased risk of high-risk adenoma. Anti-inflammatory drugs seem to reduce adenoma risk among women with high, but not low PGE-M. Urinary PGE-M may serve as a biomarker to define subsets of the population who may obtain differential chemopreventive benefit from anti-inflammatory drugs.

Role of inflammation and inflammatory mediators in colorectal cancer

Chronic inflammation is a risk factor for several different cancers including colorectal cancer (CRC). However, the mechanisms underlying the contribution of inflammation to cancer remain elusive. Pro-inflammatory mediators such as cyclooxygenase 2 (COX-2) and prostaglandin E2 (PGE2) contribute to cancer progression. Here, we show that COX-2 is an immediate-early response gene induced by growth factors and pro-inflammatory cytokines and its levels are elevated in human CRCs. Furthermore, we show that COX-2-derived PGE2 promotes colonic tumor growth via silencing certain tumor suppressors and DNA repair genes by DNA methylation in colonic epithelial tumor cells. We also report that C-X-C motif chemokine receptor 2 accelerates colonic inflammation and colitis-associated tumorigenesis by mediating myeloid-derived suppressor cell recruitment to the tumor microenvironment. These findings not only support a rationale to target these pro-inflammatory pathways for cancer prevention and treatment but also provide support for developing new therapeutic approaches to subvert chronic inflammation- and tumor-induced immunosuppression.

The obesity-inflammation-eicosanoid axis in breast cancer

Inflammation of the adipose tissues occurs in association with obesity. This inflammatory process leads to the induction of cyclooxygenase-2 (COX-2) expression and a consequent elevation in prostaglandin (PG) production, which, together with proinflammatory cytokines, induce aromatase expression and estrogen synthesis. Infiltrating macrophages support the growth of breast epithelial cells and vascular endothelial cells by producing a milieu of cytokines and growth factors. This scenario creates a microenvironment favorable to breast cancer growth and invasion. The eicosanoids promote further development and growth of breast cancers indirectly by the induction of aromatase, particularly in estrogen positive breast cancers, or by direct stimulatory effect of PGE2 and lipoxygenase (LOX) products on the more aggressive, estrogen-independent tumors. Beyond this, the local production of estrogens and proinflammatory cytokines which occurs in association with breast adipose tissue inflammation, and consequent activation of the estrogen receptor and nuclear factor-κB, provides a mechanism by which breast cancers develop resistance to selective estrogen receptor modulation and aromatase inhibitor therapy. The obesity-inflammation-eicosanoid axis in breast cancer does offer a therapeutic target for the prevention of relapse in breast cancer by improving the efficacy of antiaromatase therapy using COX/LOX inhibitors; however, careful consideration of menopausal status and obesity in patients is warranted.

Molecular pathways: adipose inflammation as a mediator of obesity-associated cancer

The increasing rate of obesity worldwide is predicted to be associated with a surge in diseases. Notably, obesity has been linked to approximately 20% of cancer cases in the United States; obesity is associated with both increased risk and worse outcomes after diagnosis. Altered levels of circulating factors are strongly implicated, including insulin, insulin-like growth factor 1, leptin, adiponectin, and interleukin-6 (IL-6). In addition, increasing attention has focused on the consequences of local adipose inflammation. Inflammatory foci characterized by crown-like structures consisting of dead adipocytes encircled by macrophages occur in white adipose depots, including the breast tissue, of most overweight and obese women. Saturated fatty acids, released as a consequence of obesity-associated lipolysis, induce macrophage activation via Toll-like receptor 4, thereby stimulating NF-κB signaling. This, in turn, activates transcription of proinflammatory genes including COX-2, IL-6, IL-1β, and TNFα. Elevated levels of proinflammatory mediators cause both local and systemic effects. Of particular relevance with regard to breast cancer is increased transcription of the CYP19 gene encoding aromatase, the rate-limiting enzyme for estrogen synthesis. Notably, this obesity-inflammation-aromatase axis provides a plausible explanation for increased rates of postmenopausal, hormone receptor-positive breast cancer associated with obesity and hence may offer targets for interventions to attenuate risk or improve prognosis. Potential approaches include weight reduction, exercise, and suppression of obesity-driven signaling pathways using pharmaceutical or dietary agents. A key future goal is to identify biomarkers that accurately report adipose inflammation, both for identification of at-risk individuals and to assess the efficacy of interventions. Clin Cancer Res; 19(22); 6074-83. ©2013 AACR.

Urinary PGE-M: a promising cancer biomarker

Cancer prevention, early diagnosis, and targeted therapies are the keys to success in better cancer control and treatment. A big challenge remains to identify biomarkers for predicting who may have higher cancer risk and are able to respond to certain chemopreventive agents as well as for assessing a patient's response during treatment. Although a large body of evidence indicates that chronic inflammation is a risk factor for cancer, it is unclear whether inflammatory biomarkers can be used to predict cancer risk, progression, and death. Considering the importance of the proinflammatory COX-2-derived prostaglandin E2 (PGE2) in inflammation and cancer, Morris and colleagues found that urinary PGE-M is positively associated with obesity, smoking, and lung metastases in patients with breast cancer (4). Along the same lines, Kim and colleagues showed a potential association between urinary PGE-M and breast cancer risk in postmenopausal women (beginning on page 511). In agreement with previous reports, their findings indicate that urinary PGE-M may serve as a promising biomarker for prognosticating cancer risk and disease progression.