Eicosanoid pathway in colorectal cancer: Recent updates

Enzymatic metabolism of the 20C polyunsaturated fatty acid (PUFA) arachidonic acid (AA) occurs via the cyclooxygenase (COX) and lipoxygenase (LOX) pathways, and leads to the production of various bioactive lipids termed eicosanoids. These eicosanoids have a variety of functions, including stimulation of homeostatic responses in the cardiovascular system, induction and resolution of inflammation, and modulation of immune responses against diseases associated with chronic inflammation, such as cancer. Because chronic inflammation is essential for the development of colorectal cancer (CRC), it is not surprising that many eicosanoids are implicated in CRC. Oftentimes, these autacoids work in an antagonistic and highly temporal manner in inflammation; therefore, inhibition of the pro-inflammatory COX-2 or 5-LOX enzymes may subsequently inhibit the formation of their essential products, or shunt substrates from one pathway to another, leading to undesirable side-effects. A better understanding of these different enzymes and their products is essential not only for understanding the importance of eicosanoids, but also for designing more effective drugs that solely target the inflammatory molecules found in both chronic inflammation and cancer. In this review, we have evaluated the cancer promoting and anti-cancer roles of different eicosanoids in CRC, and highlighted the most recent literature which describes how those molecules affect not only tumor tissue, but also the tumor microenvironment. Additionally, we have attempted to delineate the roles that eicosanoids with opposing functions play in neoplastic transformation in CRC through their effects on proliferation, apoptosis, motility, metastasis, and angiogenesis

Cadmium inhibits mismatch repair by blocking the ATPase activity of the MSH2–MSH6 complex

Cadmium (Cd(2+)) is a known carcinogen that inactivates the DNA mismatch repair (MMR) pathway. In this study, we have tested the effect of Cd(2+) exposure on the enzymatic activity of the mismatch binding complex MSH2–MSH6. Our results indicate that Cd(2+) is highly inhibitory to the ATP binding and hydrolysis activities of MSH2–MSH6, and less inhibitory to its DNA mismatch binding activity. The inhibition of the ATPase activity appears to be dose and exposure time dependent. However, the inhibition of the ATPase activity by Cd(2+) is prevented by cysteine and histidine, suggesting that these residues are essential for the ATPase activity and are targeted by Cd(2+). A comparison of the mechanism of inhibition with N-ethyl maleimide, a sulfhydryl group inhibitor, indicates that this inhibition does not occur through direct inactivation of sulfhydryl groups. Zinc (Zn(2+)) does not overcome the direct inhibitory effect of Cd(2+) on the MSH2–MSH6 ATPase activity in vitro. However, the increase in the mutator phenotype of yeast cells exposed to Cd(2+) was prevented by excess Zn(2+), probably by blocking the entry of Cd(2+) into the cell. We conclude that the inhibition of MMR by Cd(2+) is through the inactivation of the ATPase activity of the MSH2–MSH6 heterodimer, resulting in a dominant negative effect and causing a mutator phenotype

A pan-cancer transcriptomic study showing tumor specific alterations in central metabolism

© 2021, The Author(s).Recently, there has been a resurgence of interest in metabolic rewiring of tumors to identify clinically relevant genes. However, most of these studies have had either focused on individual tumors, or are too general, providing a broad outlook on overall changes. In this study, we have first curated an extensive list of genes encoding metabolic enzymes and metabolite transporters relevant to carbohydrate, fatty acid and amino acid oxidation and biosynthesis. Next, we have used publicly available transcriptomic data for 20 different tumor types from The Cancer Genome Atlas Network (TCGA) and focused on differential expression of these genes between tumor and adjacent normal tissue. Our study revealed major transcriptional alterations in genes that are involved in central metabolism. Most tumors exhibit upregulation in carbohydrate and amino acid transporters, increased glycolysis and pentose phosphate pathway, and decreased fatty acid and amino acid oxidation. On the other hand, the expression of genes of the tricarboxylic acid cycle, anaplerotic reactions and electron transport chain differed between tumors. Although most transcriptomic alterations were conserved across many tumor types suggesting the initiation of common regulatory programs, expression changes unique to specific tumors were also identified, which can provide gene expression fingerprints as potential biomarkers or drug targets. Our study also emphasizes the value of transcriptomic data in the deeper understanding of metabolic changes in diseases

HNF4A (Hepatocyte Nuclear Factor 4 alpha)

Hepatocyte nuclear factor 4 alpha (HNF4A) also known as NR2A1 (Nuclear Receptor Subfamily 2, group A, member 1) is a member of the nuclear receptor (NR) superfamily of ligand-dependent transcription factors. The encoded protein controls the expression of several genes, especially those that play distinct roles in development, differentiation, embryogenesis and organogenesis

Kas özellikleri ve obezite arasındaki ilişkinin genetik ve biyofiziksel yöntemlerle araştırılması

TÜBİTAK SBAG Proje01.04.2012Obesity, which arises from changes in lifestyle and feeding habits in developed and developing countries, is becoming a threat for human health due to its increasing prevelance. Especially, the increase in the consumption of high fat diets is one of the main factors that take role in the generation of obesity. Clinical disorders, such as type 2 diabetes, dislipidemia, cardiovascular diseases and hypertension, are all basic metabolic diseases in close relation with obesity. These metabolic disorders generally trigger each others’ prevalence. The common property shared by obesity and these metabolic disorders is the inability of insulin to exert its action on tissues, even though insulin is produced by the body. Impaired insulin sensitivity in skeletal muscle tissue is one of the most common symptom in pathophysiology of diabetes and obesity. While insulin resistance have not been yet fully established for clarity, in recent studies, more and more evidence reveals that the distribution and types of lipids are the deterministic factors in generation of insulin resistance. Therefore, determination of the distribution and types of lipids accumulated in the skeletal muscle are necessary in order to explain the generation of insulin resistance mechanism in obesity. The aim of this study was to establish the structural and functional changes in longissimus dorsi (LD) and quadriceps (Q) skeletal muscle tissue macromolecules, especially lipid, and determination of the types and distribution of the lipids within these tissues in control (C57BL/6J and DBA/2J), Berlin muscle mouse inbred (BMMI) lines and Berlin fat mouse inbred (BFMI) lines and thus, to do the characterization of these skeletal muscle tissues of inbred mouse models. For this this purpose, attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy was used to determine the properties of macromolecules, FTIR microspectroscopy was used to monitor the distribution of these macromolecules especially lipids within the skeletal muscles, confocal microscopy technique was used to monitor the lipid content of muscle fibers and to determine fibers types that these lipids accumulated more intensely and high performance liquid chromatography (HPLC) technique was used to determine the types and amounts of lipids stored in these muscles. In this study, skeletal muscle tissues of the control (C57BL/6J and DBA/2J), BMMI mice which were fed with standard breeding diet (SBD) and BFMI mice which were fed with either SBD or high-fat diet (HFD) were investigated. 14 In this study, serum levels of glucose, triglyceride and non-esterified fatty acid were found to be increased in BMMI806 among the BMMI lines and BFMI860, BFMI861 within the BFMI lines and these lines showed a slower response to insulin injection than the other lines. These results were the indicators of the development of insulin resistance in these lines. BMMI806, BFMI860 and BFMI861 lines represented different properties in comparison to the other lines. ATR-FTIR spectroscopic results revealed that BMMI806, BFMI860 ve BFMI861 mice possess higher amount of triglyceride, cholesterol ester and saturated lipid content, lower amount of unsaturated lipid content, more methly groups in lipid structure and lipids with shorther hydrocarbon chain lenght in comparison to other groups. The lipid content in skeletal muscles of all BFMI mice fed with a HFD increased, except for BFMI852 line which did not respond to feeding with HFD in terms of lipid content. The highest lipid content was found to be in BFMI860 line among the groups fed with a HFD. It had been demonstrated that the skeletal muscles of BMMI806 line amoung BMMI lines, BFMI860 and BFMI861 lines within BFMI mice had the lowest olefinic band area and unsaturation index; therefore these lines are more prone to lipid peroxidation. Lipids extracted from LD an Q skeletal muscles of control, BFMI and BMMI lines of SBD and also BFMI lines of HFD were separated, characterized and quantified by HPLC-ELSD technique. In BFMI lines, lipids were detected in higher concentrations regarding to BMMI lines. Among BFMI lines, the highest lipid concentrations were seen in BFMI860 and BFMI861 lines, respectively. In BFMI lines, other than BFMI860 and BFMI861, the concentration of detected lipids were low. The effects of HFD on the concentration of lipids were obvious. In BFMI lines which fed with HFD, had more lipid content compared to BFMI mice which fed with SBD. These findings support the ATRFTIR spectroscopic results, which was performed on the same tissues of same lines. In LD and Q muscles BMMI826 and BMMI866 lines, which were characterized as myostatin mutants, were found to have less lipid content. In myostatin wild-type BMMI806 line, the lipid concentration was detected to be higher than the other BMMI lines. These findings are also in agreement with the ATR-FTIR spectroscopic results. Lipid amounts in LD and Q skeletal muscles were also determined and compared with each other. According to the results, lipid concentration was found to be higher in LD skeletal muscle when compared to the lipid concentration in Q muscle. Via imaging techniques, higher amount of neutral lipid accumulation was observed in the cross-sections of skeletal muscle type IIa and intermediate muscle fiber, which do 15 have more oxidative metabolism. In these muscle fibers where high lipid accumulation is present, high lipit/protein distribution, high amount of methylene (CH2) groups, low amount of methyl groups (CH3) in the lipid structure, high amount of triglyceride content (carboynl, C=O) and lipids with longer chain lenght were observed. Furthermore, it was also found that, these fibers display a higher unsaturation index and lower glycogen content. This lipid accumulation was found to be the highest in the skeletal muscles of BFMI860 mice when compared to other obese mouse lines. The effect of HFD on BFMI860 mouse line regarding to the lipid accumulation, was observed to be more dramatic. When all results obtained were evaluated, with their genetically complex background, BFMI860 and BMMI806 were determined to be the most suitable lines for the investigation of spontaneous obesity in humans among all BFMI and BMMI lines. Furthermore, according to the results of this study, in LD muscles which is responsible for the posture and include more type IIa fibers than Q muscle, represented more significant results

PRKAA1 (protein kinase AMP-activated catalytic subunit alpha 1)

Protein kinase AMP-activated catalytic subunit alpha 1 (PRKAA1), also known as AMPK α1, is an energy sensor that plays a key role in the regulation of cellular energy metabolism. AMPK α1 is the catalytic subunit of the heterotrimeric AMPK protein with a length of 548 amino acids. A key switch to activate this protein is an alteration in the AMP/ATP ratio. The protein is dysregulated in several human diseases including diabetes and metabolic syndrome, cardiovascular diseases, neurodegenerative diseases and many cancer types (Steinberg and Kemp, 2009). Two isoforms of AMPK exist including AMPK α1 and AMPK α2; however, discrimination between these isoforms for their involvement in certain diseases is currently not possible

15-Lipoxygenase-1 re-expression in colorectal cancer alters endothelial cell features through enhanced expression of TSP-1 and ICAM-1

15-lipoxygenase-1 (15-LOX-1) oxygenates linoleic acid to 13(S)-hydroxyoctadecadienoic acid (RODE). The enzyme is widely suppressed in different cancers and its re-expression has tumor suppressive effects. 15-LOX-1 has been shown to inhibit neoangiogenesis in colorectal cancer (CRC); in the present study we confirm this phenomenon and describe the mechanistic basis. We show that re-expression of 15-LOX-1 in CRC cell lines resulted in decreased transcriptional activity of HIF1 alpha and reduced the expression and secretion of VEGF in both normoxic and hypoxic conditions. Conditioned medium (CM) was obtained from CRC or prostate cancer cell lines re-expressing 15-LOX-1 (15-LOX-1CM). 15-LOX-1CM treated aortic rings from 6-week old C57BL/6 mice showed significantly less vessel sprouting and more organized structure of vascular network. Human umbilical vein endothelial cells (HUVECs) incubated with 15-LOX-1CM showed reduced motility, enhanced expression of intercellular cell adhesion molecule (ICAM-1) and reduced tube formation but no change in proliferation or cell cycle distribution. HUVECs incubated with 13(S)-HODE partially phenocopied the effects of 15-LOX-1CM, showed reduced motility and enhanced expression of ICAM-1, but did not reduce tube formation, implying the importance of additional factors. Therefore, a Proteome Profiler Angiogenesis Array was carried out, which showed that Thrombospondin-1 (TSP-1), a matrix glycoprotein known to strongly inhibit neovascularization, was expressed significantly more in HUVECs incubated with 15-LOX-1CM. TSP-1 blockage in HUVECs reduced the expression of ICAM-1 and enhanced cell motility, thereby providing a mechanism for reduced angiogenesis. The anti-angiogenic effects of 15-LOX-1 through enhanced expressions of ICAM-1 and TSP-1 are novel findings and should be explored further to develop therapeutic options

Controlling complexity: the clinical relevance of mouse complex genetics.

Experimental animal models are essential to obtain basic knowledge of the underlying biological mechanisms in human diseases. Here, we review major contributions to biomedical research and discoveries that were obtained in the mouse model by using forward genetics approaches and that provided key insights into the biology of human diseases and paved the way for the development of novel therapeutic approaches

Inhibition of mackerel (Scomber scombrus) muscle lipoxygenase by green tea polyphenols

The high polyunsaturated fatty acid content of oily fish such as mackerel (Scomber scombrus) makes it particularly susceptible to oxidative degradation. We have shown previously the presence of lipoxygenase (LOX), a lipid oxygenase, in mackerel muscle. In the current study, commercially available green tea polyphenols were shown to effectively inhibit the LOX activity of mackerel muscle. EGCG (epigallocatechin gallate) was the strongest inhibitor tested with an IC50 (concentration for half maximal inhibition) value of 0.13 nM. All the tea catechins showed a nfived non-competitive type inhibition. In addition, antioxidants such as BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), esculetin, caffeic acid, ascorbic acid, and ethylene diamine tetraacetic acid (EDTA) were effective to varying degrees (IC50 values between 0.02 and >50 mu M) in the inhibition of mackerel muscle LOX. Nordihydroguaiaretic acid (NDGA), a classical LOX inhibitor and potassium cyanide (KCN), a heme protein inhibitor were assayed for their inhibitory activities for comparison

Functional Application Of İmmununoliposomes Encapsulating Celecoxib On Colon Cancer Cell Lines.

Long term regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been correlated with reduced risk of variety of cancers. Celecoxib is a new generation NSAID that can selectively inhibit activity of cyclooxygenase-2 (COX-2) Celecoxib serves as a chemopreventive agent in colorectal cancer. Therefore there is growing interest in developing drug delivery systems for celecoxib, Targeting will be carried out by conjugation of a chimeric monoclonal antibody (Cetuximab) against the Epidermal Growth Factor Receptor (EGFR). EGFR, which binds to epidermal growth factor, is essential in the normal maintenance of cellular growth and function. However, the receptor is known to be dysregulated in 25-77% of colorectal cancers and 85% of metastatic colorectal cancers. In this project we propose to prepare PEGylated liposomes encapsulating celecoxib, which will be converted immunoliposomes by conjugating to an anti-EGFR antibody. The combined inhibition of COX-2 by celecoxib and EGFR by cetuximab has been previously shown to synergistically reduce the metastatic potential of breast cancer in in vivo models (Gupta et al., 2007). Preliminary studies carried out in our laboratory indicate successful liposomal encapsulation and release of celecoxib (Deniz, Sade, Severcan, Keskin, Tezcaner & Banerjee, 2009). We therefore propose that the immunoliposomal preparation for the targeted delivery of celecoxib may hold promise for future therapeutic opportunities in colon cancer