The lipidome as a composite biomarker of the modifiable part of the risk of breast cancer

The potential for dietary fat to prevent breast cancer makes identification of defined molecules a mandatory step. In order to circumvent the limitations and/or bias of dietary exposure assessment tools, we have used the fatty acid composition of white adipose tissue as biomarker of past lipid intake. When considered separately, candidate fatty acids identified as favourable on the basis of their association with breast cancer risk have usually led to inconsistent results in dietary intervention studies carried out in rats. This inconsistency indicates that any approach based on a single fatty acid should be abandoned for an integrated view over the complex lipid interactions, which finally determines the lipidome, the lipid profile that is found in individuals. We reappraised the role of the complete lipid profile through a comprehensive study of adipose tissue fatty acids obtained in patients with benign or malignant breast tumors. Rather than a single fatty acid, a composite indicator combining elevated monounsaturates and low n-6/n-3 fatty acid ratio was associated with decreased breast cancer risk. The lipidome may provide the opportunity to quantify the modifiable part of the risk of breast cancer. The lipidome may be used as a template for designing proper dietary modifications in order to delay the occurrence of breast cancer. Which dietary modifications should be undertaken in order to bring a pertinent change to the lipidome with respect to the risk of breast cancer is currently unknown. The lipidome may allow the individualization of a high risk population of women, who may be targeted for a dietary prevention of breast cancer. The setting and validation of a high-throughput lipidomic station with analytical capabilities fitted to the need of mass screening is required. These two locks must be resolved before a primary prevention of breast cancer by diet could be contemplated.     

The role of cyclooxygenase-2 and prostaglandins in colon cancer

The temporal association between loss of function of the tumor suppressor adenomatous polyposis coli (APC) and overexpression of cyclooxygenase 2 (COX-2) has been demonstrated in vivo and has led to the hypothesis that APC regulates COX-2 expression. This could potentially occur through a variety of mechanisms including the well-characterized ability of APC to negatively regulate Wnt signaling and decrease expression of target genes. However, recent findings suggest that the products of COX-2 elicit effects that occur upstream of the beta-catenin/TCF/LEF pathway. This review will focus on the regulation of COX-2 by APC and the interplay between COX-2 and the Wnt signaling pathway.     

The antiapoptotic role of pregnane X receptor in human colon cancer cells

The orphan nuclear receptor pregnane X receptor (PXR) plays an important role in the detoxification of foreign and endogenous chemicals, including bile acids. PXR promotes bile acid elimination by activating bile acid-detoxifying enzymes and transporters. Certain bile acids are known to promote colonic carcinogenesis by inducing colon cancer cell apoptosis. However, whether and how PXR plays a role in colon cancer apoptosis has not been reported. In this study, we showed that activation of PXR by genetic (using a constitutively activated PXR) or pharmacological (using PXR agonist rifampicin) means protected the PXR-overexpressing colon cancer HCT116 cells from deoxycholic acid-induced apoptosis. Interestingly, activation of PXR also protected HCT116 cells from adriamycin-induced cell death, suggesting that the antiapoptotic effect of PXR was not bile acid specific. Moreover, the antiapoptotic effect of PXR in HCT116 cells appeared to be independent of xenobiotic enzyme regulation, because these cells had little basal and inducible expression of bile acid-detoxifying enzymes. Instead, SuperArray analysis showed that PXR-mediated deoxycholic acid resistance was associated with up-regulation of multiple antiapoptotic genes, including BAG3, BIRC2, and MCL-1, and down-regulation of proapoptotic genes, such as BAK1 and TP53/p53. Treatment with rifampicin in colon cancer LS180 cells, a cell line known to express endogenous PXR, also inhibited apoptosis. Activation of PXR in transgenic mice inhibited bile acid-induced colonic epithelial apoptosis and sensitized mice to dimethylhydrazine-induced colonic carcinogenesis, suggesting that the antiapoptotic effect of PXR is conserved in normal colon epithelium. In summary, our results have established the antiapoptotic role of PXR in both human colon cancer cells and normal mouse colon epithelium.     

The possible role of lipid peroxidation in breast cancer risk

Breast cancer remains the commonest cause of death from cancer in women in most of the Western world. There is considerable evidence that breast cancer risk is influenced by environmental factors and can therefore potentially be modified. In this paper we describe evidence suggesting a relationship of lipid peroxidation to breast cancer risk, and propose that the method used to generate this information might usefully be applied to other disease states, and make some suggestions for further work. We have compared the urinary excretion of the mutagen malonaldehyde (MDA) in premenopausal women at different risks for breast cancer as determined by the appearance of the breast parenchyma on mammography. MDA was measured in 24-h urine samples from both groups and excretion in 30 women with mammographic dysplasia (high risk) was found to be approximately double that of 16 women without these radiological changes (p less than 0.02). These results suggest that mammographic dysplasia may be associated with lipid peroxidation. Further study of environmental factors associated with states that precede the development of breast and other cancers may lead to the identification of factors that can be modified and that may prevent the development of malignant disease.     

The role of lactic acid bacteria in colon cancer prevention: mechanistic considerations

Colorectal cancer is one of the most important causes of cancer morbidity and mortality in Western countries. While a myriad of healthful effects have been attributed to the probiotic lactic acid bacteria, perhaps the most controversial remains that of anticancer activity. It should be pointed out already at this point that there is no direct experimental evidence for cancer suppression in humans as a result of consumption of lactic cultures in fermented or unfermented dairy products. However, there is a wealth of indirect evidence, based largely on laboratory studies, in the literature. The precise mechanisms by which lactic acid bacteria may inhibit colon cancer are presently unknown. However, such mechanisms might include: enhancing the host's immune response; binding and degrading potential carcinogens; quantitative and/or qualitative alterations in the intestinal microflora incriminated in producing putative carcinogen(s) and promoters (e.g. bile acid-degrading bacteria); producing antitumorigenic or antimutagenic compounds in the colon; alteration of the metabolic activities of intestinal microflora; alteration of physicochemical conditions in the colon; effects on physiology of the host. These potential mechanisms are discussed in the present paper.     

The synaptic lipidome in health and disease

Adequate homeostasis of lipid, protein and carbohydrate metabolism is essential for cells to perform highly specific tasks in our organism, and the brain, with its uniquely high energetic requirements, posesses singular characteristics. Some of these are related to its extraordinary dotation of synapses, the specialized subcelluar structures where signal transmission between neurons occurs in the central nervous system. The post-synaptic compartment of excitatory synapses, the dendritic spine, harbors key molecules involved in neurotransmission tightly packed within a minute volume of a few femtoliters. The spine is further compartmentalized into nanodomains that facilitate the execution of temporo-spatially separate functions in the synapse. Lipids play important roles in this structural and functional compartmentalization and in mechanisms that impact on synaptic transmission. This review analyzes the structural and dynamic processes involving lipids at the synapse, highlighting the importance of their homeostatic balance for the physiology of this complex and highly specialized structure, and underscoring the pathologies associated with disbalances of lipid metabolism, particularly in the perinatal and late adulthood periods of life. Although small variations of the lipid profile in the brain take place throughout the adult lifespan, the pathophysiological consequences are clinically manifested mostly during late adulthood. Disturbances in lipid homeostasis in the perinatal period leads to alterations during nervous system development, while in late adulthood they favor the occurrence of neurodegenerative diseases.     

Low serum cholesterol level and the risk of cancer of the colon

The study aimed at assessing a degree of low serum cholesterol relationship to carcinoma of the colon. The study involved 137 patients with carcinoma of the colon and 54 patients serving as a control group. Serum cholesterol and total proteins levels were assayed and nutritional status of the patients was analysed. It was found that serum cholesterol was significantly lower in patients with both advanced and mild cancer of the colon in comparison with a control group. Similar tendency was noted in the group of female patients with cancer of the colon but the difference between the patients with not advanced cancer and control group was statistically insignificant. Serum total proteins did not differ in patients with cancer of the colon and control group. In the group of male patients (with both stages of the cancer) in whom low serum cholesterol was noted (below 5.2 mM/L) a risk of cancer was 3-7 times higher. In female patients relative risk of cancer was significantly higher only in the advanced stages of the disease.     

Adiponectin deficiency: role in chronic inflammation induced colon cancer

Adiponectin (APN), an adipokine, exerts an anti-inflammatory and anti-cancerous activity with its role in glucose and lipid metabolism and its absence related to several obesity related malignancies including colorectal cancer. The aim of this study is to determine the effect of APN deficiency on the chronic inflammation-induced colon cancer. This was achieved by inducing inflammation and colon cancer in both APN knockout (KO) and C57B1/6 wild type (WT) mice. They were divided into four treatment groups (n=6): 1) control (no treatment); 2) treatment with three cycles of dextran sodium sulfate (DSS); 3) weekly doses of 1,2-dimethylhydrazine (DMH) (20mg/kg of mouse body weight) for twelve weeks; 4) a single dose of DMH followed by 3 cycles of DSS (DMH+DSS). Mice were observed for diarrhea, stool hemoccult, and weight loss and were sacrificed on day 153. Tumor area and number were counted. Colonic tissues were collected for Western blot and immunohistochemistry analyses. APNKO mice were more protected than WT mice from DSS induced colitis during first DSS cycle, but lost this protection during the second and the third DSS cycles. APNKO mice had significantly severe symptoms and showed greater number and larger area of tumors with higher immune cell infiltration and inflammation than WT mice. This result was further confirmed by proteomic study including pSTAT3, pAMPK and Cox-2 by western blot and Immunohistochemistry. Conclusively, APN deficiency contributes to inflammation-induced colon cancer. Hence, APN may play an important role in colorectal cancer prevention by modulating genes involved in chronic inflammation and tumorigenesis.     

A rat model to study the role of STn antigen in colon cancer

Expression of the mucin-associated sialyl-Tn (STn) antigen has been associated with a decreased survival in patients with colorectal, gastric, and ovarian cancer. To better understand the role of STn antigen in tumor biology, we developed STn(+) (called LP) and STn(-) (called LN) clonal cell lines from a parental metastatic rat colon carcinoma cell line (LMCR). Both derivative cell lines exhibited identical proliferation rates in vitro. LP cells strongly expressed STn antigen both in vitro and in vivo, and were poorly tumorigenic when given to syngeneic rats. LN cells did not express STn antigen in vitro, but as in vivo tumors these cells rapidly acquired STn expression, readily formed tumors, and were highly lethal. When rats were given an otherwise lethal inoculum of i.p. LN cells, pre-immunization with synthetic STn antigen conjugated to keyhole limpet hemocyanin (STn-KLH) resulted in a 60% survival rate. When LN cells were injected subcutaneously in the presence of STn-KLH-sensitized lymphocytes, tumor growth was decreased. Distribution of STn antigen in normal organs of host rats is quite similar to that of humans. This model mimics human disease and should facilitate studies of mucin-associated antigens in tumor biology and the development of immunotherapeutic agents based on mucin-related antigens.     

The role of dietary fibre in the human colon.

Several effects of dietary fibre on colonic function have been documented by experiment or deduced from epidemiologic observation. The magnitude of these changes depends on the source and the physical and chemical composition of the fibre used, and on the individual response of the subjects. Three theories of the mode of action of fibre are discussed; they relate to the water-holding capacity of fibre, the production of short-chain fatty acids from fibre in the colon and the alteration by fibre of the colonic microflora.     

The role of melanocortin-1 receptor polymorphism in skin cancer risk phenotypes

We have examined melanocortin-1 receptor (MC1R) variant allele frequencies in the general population and in a collection of adolescent dizygotic and monozygotic twins to determine statistical associations of pigmentation phenotypes with increased skin cancer risk. This included hair and skin color, freckling, mole count and sun exposed skin reflectance. Nine variants were studied and designated as either strong R (OR = 63; 95% CI 32-140) or weak r (OR = 5; 95% CI 3-11) red hair alleles. Penetrance of each MC1R variant allele was consistent with an allelic model where effects were multiplicative for red hair but additive for skin reflectance. To assess the interaction of the brown eye color gene BEY2/OCA2 on the phenotypic effects of variant MC1R alleles we imputed OCA2 genotype in the twin collection. A modifying effect of OCA2 on MC1R variant alleles was seen on constitutive skin color, freckling and mole count. In order to study the individual effects of these variants on pigmentation phenotype we have established a series of human primary melanocyte strains genotyped for the MC1R receptor. These include strains which are MC1R wild-type consensus, variant heterozygotes, and homozygotes for strong R alleles Arg151Cys and Arg160Trp. Ultrastructural analysis demonstrated that only consensus strains contained stage III and IV melanosomes in their terminal dendrites whereas Arg151Cys and Arg160Trp homozygous strains contained only immature stage I and II melanosomes. Such genetic association studies combined with the functional analysis of MC1R variant alleles in melanocytic cells should provide a link in understanding the association between pigmentary phototypes and skin cancer risk.     

Carcinogen DNA adducts and the risk of colon cancer: case-control study

Colorectal cancer represents 8.5% of all tumours at the King Faisal Specialist Hospital & Research Centre. Environmental and dietary carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs) have long been suspected to play a prominent role in colon cancer aetiology. We designed a case-control study to test the hypothesis of whether or not the presence of DNA adducts can play a role in the aetiology of colon cancer. DNA adducts were measured in 24 cancerous and 20 non-cancerous tissue samples of newly diagnosed colon cancer patients by ³²P-post-labelling technique. Normal tissue from 19 hospital patients served as controls. The mean levels of adducts per 10¹⁰ nucleotides in cancerous and non-cancerous tissue were 151.75±217.27 and 114.81±186.10, respectively; however, only adducts in cancerous tissue were significantly higher than controls (32.78±57.51 per 10¹⁰ nucleotides) with p-values of 0.017. No BPDE-DNA adducts were found. No relationship was found between urinary cotinine as a marker of tobacco smoke and 1-hydroxypyrene as an indicator of an individual's internal dose of PAHs and DNA adducts. In a logistic regression model, only adducts in cancerous tissue were associated with the subsequent risk of colon cancer, with an odds ratio of 3.587 (95% confidence interval 0.833-15.448) after adjustment for age and the duration of living in the current region, but of a borderline significance (p=0.086). Although it is difficult to arrive at a definite conclusion from a small dataset, our preliminary results suggest the potential role of DNA adducts in the colon carcinogenesis process. Additional studies with larger sample sizes are needed to confirm our preliminary finding. It is also important to identify the structural characterization of these unknown DNA adducts in order to have a better understanding of whether or not environmental carcinogens play a role in the aetiology of colon cancer.     

The role of frozen section in surgical staging of low risk endometrial cancer

Background

The role of frozen section (FS) in intraoperative decision making for surgical staging of endometrial cancer is controversial. Objective of this study is to assess the agreement rate between the FS and paraffin section (PS); and the potential impact of the role of FS in the intra-operative decision making for the complete surgical staging in low risk endometrial cancer.

Methods

This is a retrospective analysis of patients diagnosed with intra-operative FS stage I, grade I or II endometrial cancer from 1995–2004. FS results were compared with final pathology results with regard to tumor grade, depth of myometrial invasion, cervical involvement, lymphovascular invasion, and lymph node involvement. Agreement statistic with kappa was calculated using SPSS statistical software. Categorical variables were tested using chi-square test with p value of ≤0.05 being statistically significant.

Results

Of the 457 patients with endometrial cancer, 146 were evaluated by intra-operative FS and met inclusion criteria. FS results were in disagreement with permanent section in 35% for the grade (kappa 0.58, p = 0.003), 28% for depth of myometrial invasion (kappa 0.61, p<0.0001), 13% for cervical involvement (kappa 0.78, p = 0.002), and 32% for lymphovascular invasion (kappa 0.6, p = 0.01). Permanent pathology upstaged 31.9% & 23.2% of FS stage IA, & IB specimen respectively. Lymph node dissection was done in 56.8%. Lymph node metastasis was identified in 8.4%. Use of intraoperative FS would have resulted in suboptimal surgical treatment in 13% stage IA and 6.6% of stage IB patients respectively by foregoing lymphadenectomy.

Conclusion

A significant number of patients with low risk endometrial cancer by FS were upstaged and upgraded on final pathology. Before placing absolute reliance on intraoperative FS to undertake complete surgical staging, the inherent limitation of the same in predicting final stage and grade highlighted by our data need to be carefully considered.     

The developmental lipidome of Haemonchus contortus

Lipids play crucial roles in the biology of organisms, particularly relating to cellular membranes, energy storage, and intra- or inter-cellular signalling. Despite the recent expansion of the lipidomics field, very little is known about the biology of lipids in metzoan pathogens, and, to date, there has been no global lipidomic study of a parasitic nematode. Using Haemonchus contortus (barber's pole worm) as a model, we describe the first known global lipidome for a parasitic nematode via high throughput LC–MS/MS-based lipidomics. We identified a total of 554 lipid species across four lipid categories, and 18 lipid classes exhibited alterations among six developmental stages (eggs; L3 and exsheathed L3 (xL3) and L4 larval stages; female and male adults) of H. contortus. The lipid composition and abundance of H. contortus changed significantly during the transition from free-living (egg, L3 and xL3) to parasitic (L4 and adult) stages. The three main changes observed were: (i) decreased synthesis of triradylglycerols; (ii) increased glycerophospholipids (predominantly glycerophosphoethanolamines and glycerophosphocholines); and (iii) a ‘cooperative’ modulation of ether-linked lipids and saturated fatty acids. These changes suggest specific adaptations, in terms of nutrient acquisition, metabolism and development, as the nematode makes its transition to the parasitic stage inside the host animal. This lipidomic data set serves as a stimulus for studies to understand lipid biology in parasitic worms, and their roles in parasite–host interactions and disease processes.     

PSF3 marks malignant colon cancer and has a role in cancer cell proliferation

PSF3 (partner of Sld five 3) is a member of the tetrameric complex termed GINS, composed of SLD5, PSF1, PSF2, and PSF3, and well-conserved evolutionarily. Previous studies suggested that some GINS complex members are upregulated in cancer, but PSF3 expression in colon carcinoma has not been investigated. Here, we established a mouse anti-PSF3 antibody, and examined PSF3 expression in human colon carcinoma cell lines and colon carcinoma specimens. We found that PSF3 is expressed in the crypt region in normal colonic mucosa and that many PSF3-positive cells co-expressed Ki-67. This suggests that PSF3-positivity of normal mucosa is associated with cell proliferation. Expression of the PSF3 protein was greater in carcinoma compared with the adjacent normal mucosa, and even stronger in high-grade malignancies, suggesting that it may be associated with colon cancer progression. PSF3 gene knock-down in human colon carcinoma cell lines resulted in growth inhibition characterized by delayed S-phase progression. These results suggest that PSF3 is a potential biomarker for diagnosis of progression in colon cancer and could be a new target for cancer therapy.     

The role of short-chain fatty acids in orchestrating two types of programmed cell death in colon cancer

Short-chain fatty acids are the major by-products of bacterial fermentation of undigested fibers in the colon. SCFAs, mostly propionate and butyrate, induce differentiation, growth arrest, and apoptosis in colon cancer cells. The anticancer effect of SCFAs is also supported by epidemiological studies suggesting an inverse relationship between the level of dietary fibers and the incidence of human colon cancer. Dietary components influence the risk of human colon cancer including colon cancer through diverse mechanisms, which include the activation or inhibition of autophagy (type II programmed cell death (PCD)). Herein we demonstrate that propionate and butyrate induce autophagy in human colon cancer cells to dampen apoptosis, whereas inhibition of autophagy potentiates SCFA-induced apoptosis. The propionate-induced autophagy originates from mitochondria defects associated with cellular ATP depletion and ROS generation, both of which contribute to AMPK activation and consequential mTOR inhibition. Remarkably, when autophagy is suppressed through either pharmacological or genetic approaches, the colon cancer cells become sensitized toward propionate-induced apoptotic cell death (type I PCD). Our study is the first report characterizing this novel role of SCFAs in orchestrating two types of programmed cell death. The observed pro-survival effects of autophagy in retarding mitochondria-mediated apoptosis suggest that application of an autophagy inhibitor might improve the therapeutic efficacy of SCFAs in inducing colon cancer suppression.     

Chemotaxonomic characterisation of the thaumarchaeal lipidome

Thaumarchaeota are globally distributed and abundant microorganisms occurring in diverse habitats and thus represent a major source of archaeal lipids. The scope of lipids as taxonomic markers in microbial ecological studies is limited by the scarcity of comparative data on the membrane lipid composition of cultivated representatives, including the phylum Thaumarchaeota. Here, we comprehensively describe the core and intact polar lipid (IPL) inventory of ten ammonia‐oxidising thaumarchaeal cultures representing all four characterized phylogenetic clades. IPLs of these thaumarchaeal strains are generally similar and consist of membrane‐spanning, glycerol dibiphytanyl glycerol tetraethers with monoglycosyl, diglycosyl, phosphohexose and hexose‐phosphohexose headgroups. However, the relative abundances of these IPLs and their core lipid compositions differ systematically between the phylogenetic subgroups, indicating high potential for chemotaxonomic distinction of thaumarchaeal clades. Comparative lipidomic analyses of 19 euryarchaeal and crenarchaeal strains suggested that the lipid methoxy archaeol is synthesized exclusively by Thaumarchaeota and may thus represent a diagnostic lipid biomarker for this phylum. The unprecedented diversity of the thaumarchaeal lipidome with 118 different lipids suggests that membrane lipid composition and adaptation mechanisms in Thaumarchaeota are more complex than previously thought and include unique lipids with as yet unresolved properties.     

Micronutrient intake and risk of colon and rectal cancer in a Danish cohort

Background: Micronutrients may protect against colorectal cancer. Especially folate has been considered potentially preventive. However, studies on folate and colorectal cancer have found contradicting results; dietary folate seems preventive, whereas folic acid in supplements and fortification may increase the risk. Objective: To evaluate the association between intake of vitamins C, E, folate and beta-carotene and colorectal cancer risk, focusing on possibly different effects of dietary, supplemental and total intake, and on potential effect modification by lifestyle factors. Design: In a prospective cohort study of 56,332 participants aged 50–64 years, information on diet, supplements and lifestyle was collected through questionnaires. 465 Colon and 283 rectal cancer cases were identified during follow-up. Incidence rate ratios of colon and rectal cancers related to micronutrient intake were calculated using Cox proportional hazard analyses. Results: The present study found a protective effect of dietary but not supplemental folate on colon cancer. No association with any other micronutrient was found. Rectal cancer did not seem associated with any micronutrient. For both colon and rectal cancer, we found an interaction between dietary folate and alcohol intake, with a significant, preventive effect among those consuming above 10 g alcohol/day only. Conclusions: This study adds further weight to the evidence that dietary folate protects against colon cancer, and specifies that there is a source-specific effect, with no preventive effect of supplemental folic acid. Further studies should thus take source into account. Vitamins C, E and beta-carotene showed no relation with colorectal cancer.     

The possible role of contact current in cancer risk associated with residential magnetic fields

Residential electrical wiring safety practices in the US result in the possibility of a small voltage (up to a few tenths of a volt) on appliance surfaces with respect to water pipes or other grounded surfaces. This "open circuit voltage" (V(OC)) will cause "contact current" to flow in a person who touches the appliance and completes an electrical circuit to ground. This paper presents data suggesting that contact current due to V(OC) is an exposure that may explain the reported associations of residential magnetic fields with childhood leukemia. Our analysis is based on a computer model of a 40 house (single-unit, detached dwelling) neighborhood with electrical service that is representative of US grounding practices. The analysis was motivated by recent research suggesting that the physical location of power lines in the backyard, in contrast to the street, may be relevant to a relationship of power lines with childhood leukemia. In the model, the highest magnetic field levels and V(OC)s were both associated with backyard lines, and the highest V(OC)s were also associated with long ground paths in the residence. Across the entire neighborhood, magnetic field exposure was highly correlated with V(OC) (r = 0.93). Dosimetric modeling indicates that, compared to a very high residential level of a uniform horizontal magnetic field (10 mu T) or a vertical electric field (100 V/m), a modest level of contact current (approximately 18 mu A) leads to considerably greater induced electric fields (> 1 mV/m) averaged across tissue, such as bone marrow and heart. The correlation of V(OC) with magnetic fields in the model, combined with the dose estimates, lead us to conclude that V(OC) is a potentially important exposure with respect to childhood leukemia risks associated with residential magnetic fields. These findings, nonetheless, may not apply to residential service used in several European countries or to the Scandinavian studies concerned with populations exposed to magnetic fields from overhead transmission lines.