The cooked meat carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine activates the extracellular signal regulated kinase mitogen-activated protein kinase pathway

Estrogenic actions of alkaloids: Structural characteristics and molecular mechanisms

This comprehensive review of estrogenic alkaloids reveals that although the number is small, they exhibit a wide range of structures, biosynthesis pathways, mechanisms of action, and applications. Estrogenic alkaloids belong to different classes, different biosynthetic pathways, different estrogenic actions (estrogenic/synergistic, anti-estrogenic/antagonistic, biphasic, and acting as a selective estrogen receptor modulator or SERM), different receptor-initiated signaling pathways, different ways of modulations of estrogen action, and different applications. The future applications of estrogenic alkaloids, such as those for diagnostics, drug development, and therapeutics, are considered with the help of new databases containing comprehensive descriptions of their relationships and more elaborate artificial intelligence-based prediction technologies. Structure-activity studies reveal the significance of the nitrogen atom for their structural and functional diversity, which may help support their broader applications. Based on the summary of previous reports, estrogenic alkaloids have significant potential for future applications.

Dietary meat mutagens intake and cancer risk: A systematic review and meta-analysis

Background

Clinical and preclinical studies suggested that certain mutagens occurring as a reaction of creatine, amino acids, and sugar during the high temperature of cooking meat are involved in the pathogenesis of human cancer. Here we conducted a systematic review and meta-analysis to examine whether meat mutagens [PhIP, MeIQx, DiMeIQx, total HCA, and B(a)P] present a risk factor for human cancer.

Methods

We searched the following databases for relevant articles published from inception to 10 Oct 2021 with no language restrictions: Pubmed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Baidu Academic, Zhejiang Digital Library. Two independent researchers screened all titles and obtained eligible texts for further screening. Independent data extraction was conducted, and meta-analysis was carried out using random-effects models to calculate the risk ratio of the meat mutagens exposure.

Results

A total of 1,786,410 participants and 70,653 cancer cases were identified. Among these, there were 12 different types of cancer at various sites, i.e., breast, bladder, colorectal, colon, rectum, prostate, lung, Non-Hodgkin lymphoma, kidney, gastric, esophagus, pancreatic, hepatocellular carcinoma. Cancer risk was significantly increased by intake of PhIP (OR = 1.13;95% CI 1.07–1.21; p < 0.001), MeIQx (OR = 1.14; 95% CI: 1.07–1.21; p < 0.001), DiMeIQx (OR = 1.07; 95% CI: 1.01–1.13; p = 0.013), total HCA (OR = 1.20; 95% CI: 1.03–1.38; p = 0.016), and cancer risk was not significantly increased by intake of B(a)P (OR = 1.04; 95% CI: 0.98–1.10; p = 0.206).

Conclusion

Meat mutagens of PhIP, MeIQx, DiMeIQx, and total HCA have a positive association with the risk of cancer.

Systematic review registration

[www.crd.york.ac.uk/prospero], identifier [CRD42022148856].

The Cooked Meat Carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine Hair Dosimeter, DNA Adductomics Discovery, and Associations with Prostate Cancer Pathology Biomarkers

Well-done cooked red meat consumption is linked to aggressive prostate cancer (PC) risk. Identifying mutation-inducing DNA adducts in the prostate genome can advance our understanding of chemicals in meat that may contribute to PC. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic aromatic amine (HAA) formed in cooked meat, is a potential human prostate carcinogen. PhIP was measured in the hair of PC patients undergoing prostatectomy, bladder cancer patients under treatment for cystoprostatectomy, and patients treated for benign prostatic hyperplasia (BPH). PhIP hair levels were above the quantification limit in 123 of 205 subjects. When dichotomizing prostate pathology biomarkers, the geometric mean PhIP hair levels were higher in patients with intermediate and elevated-risk prostate-specific antigen values than lower-risk values <4 ng/mL (p = 0.03). PhIP hair levels were also higher in patients with intermediate and high-risk Gleason scores ≥7 compared to lower-risk Gleason score 6 and BPH patients (p = 0.02). PC patients undergoing prostatectomy had higher PhIP hair levels than cystoprostatectomy or BPH patients (p = 0.02). PhIP-DNA adducts were detected in 9.4% of the patients assayed; however, DNA adducts of other carcinogenic HAAs, and benzo[a]pyrene formed in cooked meat, were not detected. Prostate specimens were also screened for 10 oxidative stress-associated lipid peroxidation (LPO) DNA adducts. Acrolein 1,N²-propano-2'-deoxyguanosine adducts were detected in 54.5% of the patients; other LPO adducts were infrequently detected. Acrolein adducts were not associated with prostate pathology biomarkers, although DNA adductomic profiles differed between PC patients with low and high-grade Gleason scores. Many DNA adducts are of unknown origin; however, dG adducts of formaldehyde and a series of purported 4-hydroxy-2-alkenals were detected at higher abundance in a subset of patients with elevated Gleason scores. The PhIP hair biomarker and DNA adductomics data support the paradigm of well-done cooked meat and oxidative stress in aggressive PC risk.

Red and processed meat consumption and cancer outcomes: Umbrella review

The purpose of this umbrella review was to evaluate the quality of evidence, validity and biases of the associations between red and processed meat consumption and multiple cancer outcomes according to existing systematic reviews and meta-analyses. The umbrella review identified 72 meta-analyses with 20 unique outcomes for red meat and 19 unique outcomes for processed meat. Red meat consumption was associated with increased risk of overall cancer mortality, non-Hodgkin lymphoma (NHL), bladder, breast, colorectal, endometrial, esophageal, gastric, lung and nasopharyngeal cancer. Processed meat consumption might increase the risk of overall cancer mortality, NHL, bladder, breast, colorectal, esophageal, gastric, nasopharyngeal, oral cavity and oropharynx and prostate cancer. Dose-response analyses revealed that 100 g/d increment of red meat and 50 g/d increment of processed meat consumption were associated with 11%-51% and 8%-72% higher risk of multiple cancer outcomes, respectively, and seemed to be not correlated with any benefit.

Metabolism and biomarkers of heterocyclic aromatic amines in humans

Heterocyclic aromatic amines (HAAs) form during the high-temperature cooking of meats, poultry, and fish. Some HAAs also arise during the combustion of tobacco. HAAs are multisite carcinogens in rodents, inducing cancer of the liver, gastrointestinal tract, pancreas, mammary, and prostate glands. HAAs undergo metabolic activation by N-hydroxylation of the exocyclic amine groups to produce the proposed reactive intermediate, the heteroaryl nitrenium ion, which is the critical metabolite implicated in DNA damage and genotoxicity. Humans efficiently convert HAAs to these reactive intermediates, resulting in HAA protein and DNA adduct formation. Some epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and elevated cancer risk of the colorectum, pancreas, and prostate. However, other studies have reported no associations between cooked meat and these cancer sites. A significant limitation in epidemiology studies assessing the role of HAAs and cooked meat in cancer risk is their reliance on food frequency questionnaires (FFQ) to gauge HAA exposure. FFQs are problematic because of limitations in self-reported dietary history accuracy, and estimating HAA intake formed in cooked meats at the parts-per-billion level is challenging. There is a critical need to establish long-lived biomarkers of HAAs for implementation in molecular epidemiology studies designed to assess the role of HAAs in health risk. This review article highlights the mechanisms of HAA formation, mutagenesis and carcinogenesis, the metabolism of several prominent HAAs, and the impact of critical xenobiotic-metabolizing enzymes on biological effects. The analytical approaches that have successfully biomonitored HAAs and their biomarkers for molecular epidemiology studies are presented.

Dietary Carcinogens and DNA Adducts in Prostate Cancer

Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of cancer-related to death in men. The major risk factors for PC are age, family history, and African American ethnicity. Epidemiological studies have reported large geographical variations in PC incidence and mortality, and thus lifestyle and dietary factors influence PC risk. High fat diet, dairy products, alcohol and red meats, are considered as risk factors for PC. This book chapter provides a comprehensive, literature-based review on dietary factors and their molecular mechanisms of prostate carcinogenesis. A large portion of our knowledge is based on epidemiological studies where dietary factors such as cancer promoting agents, including high-fat, dairy products, alcohol, and cancer-initiating genotoxicants formed in cooked meats have been evaluated for PC risk. However, the precise mechanisms in the etiology of PC development remain uncertain. Additional animal and human cell-based studies are required to further our understandings of risk factors involved in PC etiology. Specific biomarkers of chemical exposures and DNA damage in the prostate can provide evidence of cancer-causing agents in the prostate. Collectively, these studies can improve public health research, nutritional education and chemoprevention strategies.

In vitro exposure of simulated meat-cooking fumes to assess adverse biological effects

The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is considered as a human carcinogenic or mutagenic compound that is produced from the co-condensation of creatinine and amino acids as meats cook at high temperatures. The cooking of meats at high temperatures produces fumes, and these fumes can be suspended as aerosols via the vapor-to-particle (or -droplet) process in a temperature gradient field. Size distributions of the aerosols included a significant portion of nano- and submicron-sized particles, and these can be directly deposited in the lungs and on skin by particle transport phenomena near cooking areas. In this study, for the first time, PhIP-incorporated oleic acid (OA, simulating cooking oil) (PhIP@OA) particles, including individual particulate PhIP as simulated fumes from meat cooking, were constantly produced via collison atomization and subsequent drying processes. The aerosol particles were then dispersed in phosphate-buffered saline for cytotoxicity and senescence-associated β-galactosidase assays, which were compared with dissolved PhIP in dimethyl sulfoxide. PhIP and PhIP@OA did not show significant cytotoxic effects on SHSY5Y, MRC5, and human dermal fibroblast cells compared with the dissolved PhIP but clearly induced premature senescence activities that may be caused by a limited release of PhIP molecules from the particulate PhIP.

Dietary intake alters gene expression in colon tissue: possible underlying mechanism for the influence of diet on disease

Supplemental Digital Content is available in the text.

Background

Although the association between diet and disease is well documented, the biologic mechanisms involved have not been entirely elucidated. In this study, we evaluate how dietary intake influences gene expression to better understand the underlying mechanisms through which diet operates.

Methods

We used data from 144 individuals who had comprehensive dietary intake and gene expression data from RNAseq using normal colonic mucosa. Using the DESeq2 statistical package, we identified genes that showed statistically significant differences in expression between individuals in high-intake and low-intake categories for several dietary variables of interest adjusting for age and sex. We examined total calories, total fats, vegetable protein, animal protein, carbohydrates, trans-fatty acids, mutagen index, red meat, processed meat, whole grains, vegetables, fruits, fiber, folate, dairy products, calcium, and prudent and western dietary patterns.

Results

Using a false discovery rate of less than 0.1, meat-related foods were statistically associated with 68 dysregulated genes, calcium with three dysregulated genes, folate with four dysregulated genes, and nonmeat-related foods with 65 dysregulated genes. With a more stringent false discovery rate of less than 0.05, there were nine meat-related dysregulated genes and 23 nonmeat-related genes. Ingenuity pathway analysis identified three major networks among genes identified as dysregulated with respect to meat-related dietary variables and three networks among genes identified as dysregulated with respect to nonmeat-related variables. The top networks (Ingenuity Pathway Analysis network score >30) associated with meat-related genes were (i) cancer, organismal injury, and abnormalities, tumor morphology, and (ii) cellular function and maintenance, cellular movement, cell death, and survival. Among genes related to nonmeat consumption variables, the top networks were (i) hematological system development and function, nervous system development and function, tissue morphology and (ii) connective tissue disorders, organismal injury, and abnormalities.

Conclusion

Several dietary factors were associated with gene expression in our data. These findings provide insight into the possible mechanisms by which diet may influence disease processes.

A review and meta-analysis of prospective studies of red and processed meat, meat cooking methods, heme iron, heterocyclic amines and prostate cancer

Prostate cancer remains a significant public health concern among men in the U.S. and worldwide. Epidemiologic studies have generally produced inconclusive results for dietary risk factors for prostate cancer, including consumption of red and processed meats. We aimed to update a previous meta-analysis of prospective cohorts of red and processed meats and prostate cancer with the inclusion of new and updated cohort studies, as well as evaluate meat cooking methods, heme iron, and heterocyclic amine (HCA) intake exposure data. A comprehensive literature search was performed and 26 publications from 19 different cohort studies were included. Random effects models were used to calculate summary relative risk estimates (SRREs) for high vs. low exposure categories. Additionally, meta-regression analyses and stratified intake analyses were conducted to evaluate dose-response relationships. The SRREs for total prostate cancer and total red meat consumption, fresh red meat consumption, and processed meat consumption were 1.02 (95% CI: 0.92-1.12), 1.06 (95% CI: 0.97-1.16), and 1.05 (95% CI: 1.01-1.10), respectively. Analyses were also conducted for the outcomes of non-advanced, advanced, and fatal prostate cancer when sufficient data were available, but these analyses did not produce significant results. No significant SRREs were observed for any of the meat cooking methods, HCA, or heme iron analyses. Dose-response analyses did not reveal significant patterns of associations between red or processed meat and prostate cancer. In conclusion, the results from our analyses do not support an association between red meat or processed consumption and prostate cancer, although we observed a weak positive summary estimate for processed meats.

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Interleukin-6 promotes dietary carcinogen-induced DNA damage in colorectal cancer cells

Pro-inflammatory cytokine interleukin-6 promotes dietary carcinogen-mediated DNA damage in 2D and 3D cultured cells by inducingCYP1B1expression through miR27b downregulation.

Newly defined aberrant crypt foci as a marker for dysplasia in the rat colon

Dysplasia represents a preneoplastic status in multistep colon carcinogenesis. Whereas laborious preparation of thin sections is required for its diagnosis, we here show that newly defined aberrant crypt foci (ACF) simply mark the majority of the dysplasia on the whole colon. Specifically, decoloring of the azoxymethane-treated rat colon after scoring classical ACF (cACF) resulted in visualization of a subset of aberrant crypts that remained densely stained. They were morphologically classified into three subtypes, of which two with compressed luminal openings proved highly correlated with dysplasia. Accordingly, we designated those foci harboring either of the two crypt subtypes as dysplasia-associated ACF (dACF). By serially applying different detection methods for known preneoplastic lesions to the same colon, we showed that most dACF had already been identified as cACF, and a few newly identified dACF contained an entire population of more advanced lesions, such as flat ACF and mucin-depleted foci. Consequently, integrative scoring of cACF and dACF enabled capture of all early lesions of the colon. Furthermore, 94% of the dACF showed dysplasia and 90% of the dysplastic lesions proved to be dACF. Thus, dACF is a promising marker for dysplasia, likely facilitating precise identification of the early stages of colon carcinogenesis.

The cooked meat-derived mammary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) elicits estrogenic-like microRNA responses in breast cancer cells

The cooking of meat results in the generation of heterocyclic amines (HCA), the most abundant of which is 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Data from epidemiological, mechanistic, and animal studies indicate that PhIP could be causally linked to breast cancer incidence. Besides the established DNA damaging and mutagenic activities of PhIP, the chemical is reported to have oestrogenic activity that could contribute to its tissue specific carcinogenicity. In this study we investigated the effect of treatment with PhIP and 17-β-estradiol (E2) on global microRNA (miRNA) expression of the oestrogen responsive MCF-7 human breast adenocarcinoma cell line. PhIP and E2 caused widespread and largely over-lapping effects on miRNA expression, with many of the commonly affected miRNA reported to be regulated by oestrogen and have been implicated in the initiation and progression of breast cancer. The regulatory activity of the miRNAs we show here to be responsive to PhIP treatment, are also predicted to mediate cellular phenotypes that are associated with PhIP exposure. Consequently, this study offers further support to the ability of PhIP to induce widespread effects via activation of oestrogen receptor alpha (ERα). Moreover, this study indicates that deregulation of miRNA by PhIP could potentially be an important non-DNA-damaging carcinogenic mechanism in breast cancer.

Heterocyclic aromatic amine [HCA] intake and prostate cancer risk: effect modification by genetic variants

The association between heterocyclic aromatic amine (HCA) intake and prostate cancer (PCa) risk may be modified by genetic variation in enzymes involved in HCA metabolism. We examined this question in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition Heidelberg cohort. The study included 204 PCa cases and 360 matched controls. At baseline, participants provided dietary and lifestyle data and blood samples that were used for genotyping. Dietary HCA intake-2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-dimethylimidazo [4,5-f]quinoxaline (DiMeIQx-was estimated using information on meat consumption, cooking methods, and browning degree. Risk estimates for gene × HCA interactions were calculated by unconditional logistic regression. We found inverse associations between PhIP, MeIQx, or DiMeIQx intake and PCa risk when having <2 deletions of the GSTT1 and GSTM1 genes (P(interaction): 0.03, 0.01, and 0.03, respectively), which is supported by analysis of darkly browned meat consumption data. Statistically significant effect modification of both HCA (DiMeIQx) and darkly browned meat intake and PCa risk was observed for allelic variants of MnSOD (rs4880) (P(interaction): 0.02). Despite limitations due to study size, we conclude that the association between HCA intake and PCa risk could be modified by polymorphisms of GSTT1, GSTM1, and MnSOD.

Epigenetics and breast cancers

Several of the active compounds in foods, poisons, drugs, and industrial chemicals may, by epigenetic mechanisms, increase or decrease the risk of breast cancers. Enzymes that are involved in DNA methylation and histone modifications have been shown to be altered in several types of breast and other cancers resulting in abnormal patterns of methylation and/or acetylation. Hypermethylation at the CpG islands found in estrogen response element (ERE) promoters occurs in conjunction with ligand-bonded alpha subunit estrogen receptor (Erα) dimers wherein the ligand ERα dimer complex acts as a transcription factor and binds to the ERE promoter. Ligands could be 17-β-estradiol (E2), phytoestrogens, heterocyclic amines, and many other identified food additives and heavy metals. The dimer recruits DNA methyltransferases which catalyze the transfer of methyl groups from S-adenosyl-L-methionine (SAM) to 5'-cytosine on CpG islands. Other enzymes are recruited to the region by ligand-ERα dimers which activate DNA demethylases to act simultaneously to increase gene expression of protooncogenes and growth-promoting genes. Ligand-ERα dimers also recruit histone acetyltransferase to the ERE promoter region. Histone demethylases such as JMJD2B and histone methyltransferases are enzymes which demethylate lysine residues on histones H3 and/or H4. This makes the chromatin accessible for transcription factors and enzymes.

Intervention of human breast cell carcinogenesis chronically induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

More than 85% of breast cancers are sporadic and attributable to long-term exposure to environmental carcinogens, such as those in the diet, through a multistep disease process progressing from non-cancerous to premalignant and malignant stages. The chemical carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic amines found in high-temperature cooked meats and is recognized as a mammary carcinogen. However, the PhIP's mechanism of action in breast cell carcinogenesis is not clear. Here, we demonstrated, for the first time, that cumulative exposures to PhIP at physiologically achievable, pico to nanomolar concentrations effectively induced progressive carcinogenesis of human breast epithelial MCF10A cells from a non-cancerous stage to premalignant and malignant stages in a dose- and exposure-dependent manner. Progressive carcinogenesis was measured by increasingly- acquired cancer-associated properties of reduced dependence on growth factors, anchorage-independent growth, acinar-conformational disruption, proliferation, migration, invasion, tumorigenicity with metastasis and increased stem-like cell populations. These biological changes were accompanied by biochemical and molecular changes, including upregulated H-Ras gene expression, extracellular signal-regulated kinase (ERK) pathway activation, Nox-1 expression, reactive oxygen species (ROS) elevation, increased HIF-1α, Sp1, tumor necrosis factor-α, matrix metalloproteinase (MMP)-2, MMP-9, aldehyde dehydrogenase activity and reduced E-cadherin. The Ras-ERK-Nox-ROS pathway played an important role in not only initiation but also maintenance of cellular carcinogenesis induced by PhIP. Using biological, biochemical and molecular changes as targeted endpoints, we identified that the green tea catechin components epicatechin-3-gallate and epigallocatechin-3-gallate, at non-cytotoxic doses, were capable of suppressing PhIP-induced cellular carcinogenesis and tumorigenicity.

Patterns of meat intake and risk of prostate cancer among African-Americans in a large prospective study

OBJECTIVE

Given the large racial differences in prostate cancer risk, further investigation of diet and prostate cancer is warranted among high-risk groups. The purpose of this study was to examine the association between type of meat intake and prostate cancer risk among African-American men.

METHODS

In the large, prospective NIH-AARP Diet and Health Study, we analyzed baseline (1995-1996) data from African-American participants, aged 50-71 years. Incident prostate cancer cases (n = 1,089) were identified through 2006. Dietary and risk factor data were ascertained by questionnaires administered at baseline. Cox models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) within intake quantiles.

RESULTS

Neither white nor processed meat intake was associated with prostate cancer, regardless of meat-cooking method. Red meats cooked at high temperatures were associated with an increased risk of prostate cancer (HR = 1.18, 95% CI = 1.00-1.38 and HR = 1.22, 95% CI = 1.03-1.44, for the upper two intake tertiles). Intake of the heterocyclic amine (HCA), 2-amino-3,4,8-trimethylimidazo[4,5-f] quinoxaline (DiMeIQx) was positively associated with prostate cancer (HR = 1.30; 95% CI = 1.05-1.61, p = 0.02). No associations were observed for intake of other HCAs.

CONCLUSION

Red meats cooked at high temperatures were positively associated with prostate cancer risk among African-American men. Further studies are needed to replicate these findings.

Delphinidin Inhibits HER2 and Erk1/2 Signaling and Suppresses Growth of HER2-Overexpressing and Triple Negative Breast Cancer Cell Lines

Delphinidin is a polyphenolic compound found in many brightly colored fruits and vegetables. Delphinidin is also the major bioactive component found in many dietary supplements that are currently consumed as complementary cancer medicine including pomegranate extract. The purpose of the current study was to determine the in vitro biological effects of delphinidin on established breast cancer cell lines of varying molecular subtypes in comparison to non-transformed breast epithelial cells. We examined cell proliferation, apoptosis, and growth inhibition in response to delphinidin using a tetrazolium salt-based assay, DNA fragmentation assay, and anchorage-independent growth assay. In comparison to vehicle control, delphinidin inhibited proliferation (P < 0.05), blocked anchorage-independent growth (P < 0.05), and induced apoptosis (P < 0.05) of ER-positive, triple negative, and HER2-overexpressing breast cancer cell lines with limited toxicity to non-transformed breast epithelial cells. MAPK signaling was partially reduced in triple negative cells and ER-negative chemically transformed MCF10A cells after treatment with delphinidin. In addition, delphinidin induced a significant level of apoptosis in HER2-overexpressing cells in association with reduced HER2 and MAPK signaling. Since delphinidin is often consumed as a complementary cancer medicine, the effect of delphinidin on response to specific HER2-targeted breast cancer therapies was examined by proliferation assay. Results of these drug combination studies suggested potential antagonism between delphinidin and HER2-directed treatments. In summary, the data presented here suggest that single agent delphinidin exhibits growth inhibitory activity in breast cancer cells of various molecular subtypes, but raise concerns regarding potential drug antagonism when used in combination with existing targeted therapies in HER2-overexpressing breast cancer.

The cooked meat-derived mammary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine promotes invasive behaviour of breast cancer cells

The cooked meat derived genotoxic carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces cancer of the colon, prostate and mammary gland when fed to rats. Epidemiology studies link these tumours to a Western diet and exposure to heterocyclic amines such as PhIP. We have shown that PhIP is also potently estrogenic and have proposed that this hormonal activity contributes to its target site carcinogenicity. We now postulate that the estrogenic properties of PhIP influence metastatic potential. We have used an in vitro assay for cell invasion based upon digestion and migration through a reconstituted basement membrane model. Zymography and immunoblotting were used to confirm PhIP-mediated changes associated with induction of the invasive phenotype. Treatment of the mammary cancer cell lines MCF-7 and T47D with PhIP induces cells to digest and migrate through a reconstituted basement membrane. The response was dose dependent, observed at sub-nanomolar concentrations of PhIP and was inhibited by the antiestrogen ICI 182,780. The PhIP-induced invasive phenotype was associated with expression of cathepsin D, cyclooxygenase-2 and matrix metalloproteinase activity. These findings emphasise the range and potency of the biological activities associated with this cooked meat product and mechanistically support the tissue-specific carcinogenicity of the chemical.

Responses of PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in MCF-7 cells are culture condition dependent

To compare the effects of the food toxin 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and estradiol in hormone-responsive MCF-7 cells, the cells were exposed to different concentrations of either PhIP or estradiol. The effect of various culture conditions (e.g. phenol red, FBS, vehicle (DMSO/EtOH) and seeding density) on responses was studied. Cells were continuously grown with steroid-containing or -deprived medium, or switched from steroid-containing to -deprived medium for the experiments to minimize the effect of background estrogenicity. Effects of PhIP and estradiol on cell viability and proliferation were determined by ATP analysis and Ki-67 immunocytochemistry. Expression of estrogen receptor alpha, cell stress markers (p53 and ERK) and estrogen responsive proteins (c-myc and ERK) were immunoblotted. All concentrations of estradiol induced cell proliferation, viability and changes in protein expression, typical for estrogenic responses. PhIP, however, increased viability only at low concentrations and depending on culture conditions. No changes in protein expressions by PhIP were noted, not even when switching cells from steroid-containing to -deprived medium which down-regulated the expression of proteins at basal level. Vehicle affected significantly viability, especially after exposure to PhIP, but not protein expression while medium changes affected both. In conclusion, the effects of PhIP and estradiol in MCF-7 cells are dependent on culture conditions. The detected PhIP-induced changes are weaker compared to those induced by estradiol.

Detection of PhIP in grilled chicken entrées at popular chain restaurants throughout California

Heterocyclic amines (HCAs), compounds formed when meat is cooked at high temperatures particularly through pan frying, grilling, or barbequing, pose a potential carcinogenic risk to the public. It is unclear whether there is any level at which consumption of HCAs can be considered safe. Efforts to measure these compounds mainly include cooking studies under laboratory conditions and some measurement of home-cooked foods, but analysis of commercially cooked foods has been minimal. Attempts to estimate exposure of the public to these compounds must take into consideration dining outside the home, which could result in significant exposure for some individuals. We surveyed at least 9 locations each of 7 popular chain restaurants (McDonald's, Burger King, Chick-fil-A, Chili's, TGI Friday's, Outback Steakhouse, and Applebee's) in California, collecting one or two entrees from each location. Entrees were analyzed for 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using high-performance liquid chromatography tandem mass spectrometry. All 100 samples contained PhIP. Concentrations were variable within and between entrees and ranged from 0.08 to 43.2 ng/g. When factoring in the weight of the entrees, absolute levels of PhIP reached over 1,000 ng for some entrees. Potential strategies for reducing exposure include the avoidance of meats cooked using methods that are known to form PhIP.

Xenobiotic metabolizing gene variants, dietary heterocyclic amine intake, and risk of prostate cancer

We recently reported that heterocyclic amines (HCA) are associated with prostate cancer risk in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. We now use extensive genetic data from this resource to determine if risks associated with dietary HCAs {2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP); 2-amino-3,8-dimethylimidazo[4,5-b]quinoxaline (MeIQx); and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx)} from cooked meat are modified by single nucleotide polymorphisms (SNP) in genes involved in HCA metabolism (CYP1A1, CYP1A2, CYP1B1, GSTA1, GSTM1, GSTM3, GSTP1, NAT1, NAT2, SULT1A1, SULT1A2, and UGT1A locus). We conducted a nested case-control study that included 1,126 prostate cancer cases and 1,127 controls selected for a genome-wide association study for prostate cancer. Unconditional logistic regression was used to estimate odds ratios (OR), 95% confidence intervals (95% CI), and P values for the interaction between SNPs, HCA intake, and risk of prostate cancer. The strongest evidence for an interaction was noted between DiMeIQx and MeIQx and the polymorphism rs11102001 downstream of the GSTM3 locus (P(interaction) = 0.001 for both HCAs; statistically significant after correction for multiple testing). Among men carrying the A variant, the risk of prostate cancer associated with high DiMeIQx intake was 2-fold greater than that with low intake (OR, 2.3; 95% CI, 1.2-4.7). The SNP rs11102001, which encodes a nonsynonymous amino acid change P356S in EPS8L3, is a potential candidate modifier of the effect of HCAs on prostate cancer risk. The observed effect provides evidence to support the hypothesis that HCAs may act as promoters of malignant transformation by altering mitogenic signaling.