The possible involvement of 15-lipoxygenase/leukocyte type 12-lipoxygenase in colorectal carcinogenesis

Antisense overlapping long non-coding RNA regulates coding arachidonate 12-lipoxygenase gene by translational interference

The arachidonate 12-lipoxygenase (ALOX12) enzyme catalyzes polyunsaturated fatty acids and facilitates generation of bioactive lipid mediators associated with various biological processes and disease pathologies. The human genome assembly revealed that the ALOX12 gene overlaps an antisense non-coding gene designated as ALOX12-antisense 1 (ALOX12-AS1). This arrangement indicates that the uncharacterized ALOX12-AS1 long non-coding RNA (lncRNA) may bind to the sense coding ALOX12 mRNA to form an antisense-sense duplex providing the basis of a novel ALOX12 regulatory mechanism. Therefore, this study was designed to determine whether the interaction of ALOX12-AS1 with ALOX12 mRNA functions as an anti-sense/sense duplex-mediated regulatory mechanism controlling the cellular content of ALOX12. Our findings indicate that two major isoforms of ALOX12-AS1 lncRNA are ubiquitously expressed in a variety of primary adult human tissues and different transformed cell types. RNA-FISH revealed cell-type-specific cytosolic as well as nuclear and nucleolar localization of the lncRNA. Interestingly, phorbol ester-induced nucleo-cytoplasmic translocation of the lncRNA in monocytic THP-1 cells resulted in a reduction of ALOX12 protein without a concomitant change in its mRNA level. This indicated ALOX12-AS1 operates via an antisense-sense duplex-mediated translational downregulation mechanism. This deduction was validated by demonstrating sense/antisense duplex formation and an association of the duplex with ribosomal proteins in HEK293 cells. Overall, this study revealed a hitherto unknown mechanism of antisense lncRNA-mediated translational downregulation of ALOX12 that adds to the existing regulatory mechanisms for the modulation of potent bioactive lipid mediators that contribute to both health and disease.

Therapeutic potentials of baicalin and its aglycone, baicalein against inflammatory disorders

The flavonoids, baicalin (5,6-dihydroxy-2-phenyl-4H-1-benzopyran-4-one-7-O-d-β-glucuronic acid) 1 and its aglycone, baicalein 2 are found in edible medicinal plants, Scutellaria baicalensis Georgi and Oroxylum indicum (L.) Kurz in abundant quantities. The antioxidant and anti-inflammatory effects of these flavonoids have been demonstrated in various disease models, including diabetes, cardiovascular diseases, inflammatory bowel diseases, gout and rheumatoid arthritis, asthma, neurodegenerative-, liver- and kidney diseases, encephalomyelitis, and carcinogenesis. These flavonoids have almost no toxicity to human normal epithelial, peripheral and myeloid cells. Their antioxidant and anti-inflammatory activities are largely due to their abilities to scavenge the reactive oxygen species (ROS) and improvement of antioxidant status by attenuating the activity of NF-κB and suppressing the expression of several inflammatory cytokines and chemokines including monocyte chemotactic protein-1 (MCP-1), nitric oxide synthase, cyclooxygenases, lipoxygenases, cellular adhesion molecules, tumor necrosis factor and interleukins. In this review, we summarize the antioxidant and anti-inflammatory effects of baicalin and baicalein with molecular mechanisms for their chemopreventive and chemotherapeutic applications in the treatment of inflammatory-related diseases.

The role of lipoxygenases in pathophysiology; new insights and future perspectives

Lipoxygenases (LOXs) are dioxygenases that catalyze the formation of corresponding hydroperoxides from polyunsaturated fatty acids such as linoleic acid and arachidonic acid. LOX enzymes are expressed in immune, epithelial, and tumor cells that display a variety of physiological functions, including inflammation, skin disorder, and tumorigenesis. In the humans and mice, six LOX isoforms have been known. 15-LOX, a prototypical enzyme originally found in reticulocytes shares the similarity of amino acid sequence as well as the biochemical property to plant LOX enzymes. 15-LOX-2, which is expressed in epithelial cells and leukocytes, has different substrate specificity in the humans and mice, therefore, the role of them in mammals has not been established. 12-LOX is an isoform expressed in epithelial cells and myeloid cells including platelets. Many mutations in this isoform are found in epithelial cancers, suggesting a potential link between 12-LOX and tumorigenesis. 12R-LOX can be found in the epithelial cells of the skin. Defects in this gene result in ichthyosis, a cutaneous disorder characterized by pathophysiologically dried skin due to abnormal loss of water from its epithelial cell layer. Similarly, eLOX-3, which is also expressed in the skin epithelial cells acting downstream 12R-LOX, is another causative factor for ichthyosis. 5-LOX is a distinct isoform playing an important role in asthma and inflammation. This isoform causes the constriction of bronchioles in response to cysteinyl leukotrienes such as LTC4, thus leading to asthma. It also induces neutrophilic inflammation by its recruitment in response to LTB4. Importantly, 5-LOX activity is strictly regulated by 5-LOX activating protein (FLAP) though the distribution of 5-LOX in the nucleus. Currently, pharmacological drugs targeting FLAP are actively developing. This review summarized these functions of LOX enzymes under pathophysiological conditions in mammals.

Polymorphisms in arachidonic acid metabolism-related genes and the risk and prognosis of colorectal cancer

Cyclooxygenase-2 (COX-2), 12-lipoxygenase (12-LOX) and phospholipaseA2 (PLA2) played important roles in the modulation of apoptosis, angiogenesis, carcinogenesis and invasion of colorectal cancer (CRC). The polymorphisms in COX-2, 12-LOX and PLA2 may affect their roles. Therefore, we investigated if COX-2 -1195G > A, 12-LOX 261Arg > Gln and PLA2 c.349 + 191A > G polymorphisms were associated with risk and prognosis of CRC as well as possible interactions with the environmental factors on the risk of CRC in Northeast of China. A case-control study with 451 cases and 631 controls were carried out, a cohort with 386 patients were followed up. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Compared with the 261Arg/Arg genotype, 12-LOX 261Arg/Gln genotype and 261Arg/Gln + Gln/Gln genotypes reduced the risk of rectal cancer by 33% (adjusted OR = 0.67, 95% CI 0.47-0.97, p = 0.03) and 32% (adjusted OR = 0.68, 95% CI 0.49-0.96, p = 0.03), respectively. The adjusted HR for the association between 12-LOX 261Gln/Gln genotype and overall survival in patients with CRC was 1.68 (95% CI 1.06-2.68, p = 0.03). There was also evidence of an interaction between the PLA2 c.349 + 191 A > G genotypes and the overnight food consumption (adjusted ORi = 1.92, 95% CI 1.14-3.25, P(interaction) = 0.01). These observations indicate that 12-LOX 261Arg > Gln polymorphism may affect risk of rectal cancer, and it may be a potential predictive marker for prognosis of CRC.

Synthesis and structure-activity relationship studies of 4-((2-hydroxy-3-methoxybenzyl)amino)benzenesulfonamide derivatives as potent and selective inhibitors of 12-lipoxygenase

Human lipoxygenases (LOXs) are a family of iron-containing enzymes which catalyze the oxidation of polyunsaturated fatty acids to provide the corresponding bioactive hydroxyeicosatetraenoic acid (HETE) metabolites. These eicosanoid signaling molecules are involved in a number of physiologic responses such as platelet aggregation, inflammation, and cell proliferation. Our group has taken a particular interest in platelet-type 12-(S)-LOX (12-LOX) because of its demonstrated role in skin diseases, diabetes, platelet hemostasis, thrombosis, and cancer. Herein, we report the identification and medicinal chemistry optimization of a 4-((2-hydroxy-3-methoxybenzyl)amino)benzenesulfonamide-based scaffold. Top compounds, exemplified by 35 and 36, display nM potency against 12-LOX, excellent selectivity over related lipoxygenases and cyclooxygenases, and possess favorable ADME properties. In addition, both compounds inhibit PAR-4 induced aggregation and calcium mobilization in human platelets and reduce 12-HETE in β-cells.

Structure based design and synthesis of peptide inhibitor of human LOX-12: in vitro and in vivo analysis of a novel therapeutic agent for breast cancer

Human breast cancer cell proliferation involves a complex interaction between growth factors, steroid hormones and peptide hormones. The interaction of growth factors, such as epidermal growth factor (EGF), with their receptors on breast cancer cells can lead to the hydrolysis of phospholipids and release of fatty acid such as arachidonic acid, which can be further metabolized by cyclooxygenase (COX) and lipoxygenase (LOX) pathways to produce prostaglandins. The high concentration of prostaglandins has been associated with chronic inflammatory diseases and several types of human cancers. This is due to the over expression COX, LOX and other inflammatory enzymes. Ten peptides were designed and synthesized by solid phase peptide synthesis and analyzed in vitro for enzyme inhibition. Out of these peptides, YWCS had shown significant inhibitory effects. The dissociation constant (K_D) was determined by surface plasmon resonance (SPR) analysis and was found to be 3.39×10⁻⁸ M and 8.6×10⁻⁸ M for YWCS and baicalein (positive control), respectively. The kinetic constant Ki was 72.45×10⁻⁷ M as determined by kinetic assay. The peptide significantly reduced the cell viability of estrogen positive MCF-7 and estrogen negative MDA-MB-231 cell line with the half maximal concentration (IC₅₀) of 75 µM and 400 µM, respectively. The peptide also induced 49.8% and 20.8% apoptosis in breast cancer cells MCF-7 and MDA-MB-231, respectively. The YWCS was also found to be least hemolytic at a concentration of 358 µM. In vivo studies had shown that the peptide significantly inhibits tumor growth in mice (p<0.017). This peptide can be used as a lead compound and complement for ongoing efforts to develop differentiation therapies for breast cancer.

Evaluation of human LOX-12 as a serum marker for breast cancer

The high concentration of prostaglandins has been associated with chronic inflammatory diseases and several types of human cancers. This is due to the over expression of inflammatory enzymes like Cyclooxygenase (COX), Lipoxygenase (LOX) etc. The aim of this study was to quantify the LOX-12 with clinicopathological parameter of breast cancer patients and its response after chemotherapy to establish serum LOX-12 as a prognostic marker. This case-controlled study was performed on 86 biopsy proven breast cancer patients. Blood and tissue samples were collected from the patients. Serum LOX-12 of the study group was quantified by Surface Plasmon Resonance (SPR) and ELISA techniques by antibody-antigen interaction strategy. A significant increase in LOX-12 levels was observed in breast cancer patients (Mean ± SD=40.54±13.61 ng/ml) as compared to healthy controls (Mean ± SD=13.42±2.4 ng/ml) (p<0.0001). Serum LOX-12 levels were significantly higher (p<0.002) in patients with lymph node involvement. More than 75% patients had shown significant (p<0.0001) reduction of LOX-12 levels after chemotherapy. This was also confirmed by ELISA. This study for the first time had co-related the quantity of serum LOX-12 with breast cancer and also with the effect of chemotherapy.

Association of a functional polymorphism (Gln261Arg) in 12-lipoxygenase with breast cancer

The overexpression of arachidonyl lipoxygenase-12 (ALOX12) in breast cancer has been reported. Hence, we examined whether a non-synonymous polymorphism of ALOX12 (mRNA, A835G; Gln261Arg) is associated with breast cancer in females. The polymorphism was detected in genomic DNA by PCR-RFLP. The association between the A835G polymorphism and breast cancer risk was measured by odds ratio (OR) with 95% confidence intervals (CIs) using Fisher's exact test, and differences were considered significant at p<0.05. The frequencies of AA (wild-type), GG (homozygous variant) and AG (heterozygous variant) were 59.5, 0.9 and 39.6% in the controls, and 39.3, 2.5 and 58.2% in the breast cancer cases, respectively. The frequency of the AG genotype was higher in the patients compared to the controls (p<0.0014). The frequency of the GG variant was 2.5 and 0.9% in the cancer subjects and controls, respectively. The relative risk of breast cancer was 2 times greater (OR=2.227) at 95% CI when compared to the relative risk of the heterozygous variant. For the GG genotype, the risk was 4 times greater (OR=4.125) at 95% CI than that of the controls, suggesting a positive association of the AG genotype with the occurrence of breast cancer. The frequencies of the polymorphism were different in different populations. The Arg/Gln and Arg/Arg variants were associated with an increased risk of breast cancer, and the frequencies of the variants differed considerably among various populations. The identification of a gene with links to breast cancer may impact screening, diagnosis and drug development.

Targeted chiral lipidomics analysis by liquid chromatography electron capture atmospheric pressure chemical ionization mass spectrometry (LC-ECAPCI/MS)

The corona discharge used to generate positive and negative ions under conventional atmospheric pressure chemical ionization (APCI) conditions also provides a source of low-energy gas-phase electrons. This is thought to occur by displacement of electrons from the nitrogen sheath gas. Therefore, suitable analytes can undergo electron capture in the gas phase in a manner similar to that observed for gas chromatography/electron capture negative chemical ionization/mass spectrometry (MS). This technique, which has been named electron-capture APCI (ECAPCI)/MS, mass spectrometry provides an increase in sensitivity of two orders of magnitude when compared with conventional APCI methodology. It is a simple procedure to tag arachidonic acid- and linoleic acid-derived oxidized lipids with an electron-capturing group such as the pentafluorobenzyl (PFB) moiety before analysis. PFB derivatives have previously been used as electron-capturing derivatives because they undergo dissociative electron capture in the gas phase to generate negative ions through the loss of a PFB radical. A similar process occurs under ECAPCI conditions. By monitoring the negative ions that are formed, it is possible to obtain extremely high sensitivity for PFB derivatives of oxidized lipids derived from arachidonic and linoleic acid. A combination of stable isotope dilution methodology and chiral liquid chromatography-ECAPCI/MS makes it possible to resolve and quantify complex mixtures of regioisomeric and enantiomeric oxidized lipids.

Cyclooxygenase-2-mediated metabolism of arachidonic acid to 15-oxo-eicosatetraenoic acid by rat intestinal epithelial cells

Rat intestinal epithelial cells that permanently express the cyclooxygenase-2 (COX-2) gene (RIES cells) were used to investigate COX-2-mediated arachidonic acid (AA) metabolism. A targeted chiral lipidomics approach was employed to quantify AA metabolites that were secreted by the cells into the culture media. When intact RIES cells were treated with calcium ionophore A-23187 (1 microM) for 1 h, 11-(R)-hydroxyeicosatetraenoic acid (HETE) was the most abundant metabolite, followed by prostaglandin (PG) E 2, 15-(S)-HETE, 15-oxo-eicosatetraenoic acid (ETE), and 15-(R)-HETE. Incubation for a further 23 h after the calcium ionophore was removed resulted in a substantial increase in PGE 2 concentrations while HETE and 15-oxo-ETE concentrations decreased to almost undetectable levels. A similar metabolic profile was observed when RIES cells were treated with increasing concentrations of AA for 24 h. Incubation of the RIES cells with 10 microM AA revealed that maximal concentrations of 11-(R)-HETE, 15-(S)-HETE, and 15-oxo-ETE occurred after 10 min of incubation when the 15-( S)-HETE concentrations were approximately twice that of PGE 2. There was a gradual decrease in the concentrations of HETE and 15-oxo-ETE over time, whereas PGE 2 concentrations increased steadily until they reached a maximum after 24 h of incubation. The ratio of PGE 2 to 15-(S)-HETE was then approximately 20:1. 15-(S)-HETE and 15-oxo-ETE concentrations declined in the cell media during prolonged incubations with pseudo-first-order rate constants of 0.0121 and 0.0073 min(-1), respectively. 15-(S)-HETE was shown to undergo metabolism primarily to 15-oxo-ETE, which was further metabolized to a glutathione (GSH) adduct. The GSH adduct of 15-oxo-ETE was further metabolized in the extracellular milieu to a cysteinylglycine adduct. Thus, we have established for the first time that 15-oxo-ETE can be formed biosynthetically from AA, that 15-(S)-HETE is its immediate precursor, and that 15-oxo-ETE forms a GSH adduct. For ionophore-A-23187-stimulated cells and at early time points for AA-stimulated cells, 11-(R)-HETE was the major eicosanoid to be secreted into the media. Adding increasing concentrations of AA to cells in culture made it possible to estimate with surprising accuracy endogenous eicosanoid production using regression analyses. Thus, after 24 h in the absence of added AA, 11-(R)-HETE and 15-(R)-HETE were estimated to be present at concentrations close to the detection limit of our very sensitive assay. These data further highlight the importance of endogenous COX-2-mediated lipid peroxidation and illustrate the necessity to monitor eicosanoid formation from endogenous stores of AA in cell culture experiments.

Platelet 12-lipoxygenase Arg261Gln polymorphism: functional characterization and association with risk of esophageal squamous cell carcinoma in combination with COX-2 polymorphisms

BACKGROUND

Aberrant arachidonic acid metabolism by 12-lipoxygenase (12-LOX) and cyclooxygenase-2 (COX-2) has been implicated in human carcinogenesis. Inherited polymorphisms in 12-LOX and COX-2 contributed to differential expression or activity of these enzymes might confer interindividual susceptibility to cancer.

OBJECTIVE

To examine the functional significance of 12-LOX 261 Arg> Gln polymorphism and its association, alone and in combination with COX-2 -1195G > A and -765G > C polymorphisms, with risk of developing esophageal squamous cell carcinoma (ESCC).

METHODS

The platelet 12-LOX activity was measured by quantifying 12-HETE in the lipoxygenation reaction. Genotypes of 12-LOX261Arg>Gln and COX-2 -1195G>A and -765G>C polymorphisms were determined in a case-control study consisting of 1026 patients and 1270 controls. Associations with the risk of ESCC were estimated by logistic regression.

RESULTS

Subjects with the 12-LOX Gln/Gln genotype had higher platelet 12-LOX activity (mean+/-SEM nmol/mg/min) than those with the Arg/Arg genotype (0.405+/-0.047 [n=10] versus 0.136+/-0.022 [n=6]; P=0.001). Genotyping data showed that the 12-LOX Gln/Gln genotype was associated with increased risk of developing ESCC (odds ratio [OR]=1.42, 95% confidence interval [CI]=1.12-1.81), compared with the Arg/Arg genotype adjusted for sex, age, and smoking. An increased risk of ESCC was also associated with the COX-2 -1195GA (OR=1.34, 95% CI=1.08-1.68; P=0.008), -1195AA (OR=1.72, 95% CI=1.35-2.20; P=<0.001), and -765GC (OR=2.24, 95% CI=1.59-3.16; P<0.001) genotypes. Furthermore, a multiplicative interaction between the 12-LOX Gln/Gln and COX-2 -1195AA or -765GC genotype in intensifying risk of ESCC was observed, with the ORs for the presence of both 12-LOX Gln/Gln and COX-2 -1195AA or -765GC genotypes being 3.21 (95% CI=1.93-5.34) and 3.33 (95% CI=1.59-6.98). A multiplicative interaction between the -765GC genotype and smoking was also evident (OR=4.45, 95% CI=2.71-7.29).

CONCLUSION

These observations suggest that inherited polymorphisms in arachidonic acid-metabolizing enzymes, which result in heightened gene expression or enzymatic activity, may confer host susceptibility to ESCC.

Common polymorphisms in 5-lipoxygenase and 12-lipoxygenase genes and the risk of incident, sporadic colorectal adenoma

BACKGROUND

Lipoxygenases (LOX) are major enzymes that metabolize arachidonic acid to hydroxyl-eicosatetraenoic acids and leukotrienes, which have been implicated in inflammation and colorectal cancer risk. Polymorphisms in LOX genes may influence their function and/or expression and, thus, may modify the risk for colorectal adenoma. The authors investigated the associations of 3 polymorphisms (2 in 5-LOX, -1708 guanine-->adenine and 21 cytosine-->thymine; and 1 in 12-LOX, arginine 261 glutamine [Arg261Gln]) in LOX genes with the risk of colorectal adenoma and also explored possible interactions of these polymorphisms with several inflammation-pathway or arachidonic acid metabolism-pathway related factors with the risk of colorectal adenoma.

METHODS

By using data from a community-based, case-control study of incident, sporadic colorectal adenoma that included 162 cases and 211 controls, the authors constructed multiple logistic regression models to estimate the odds ratios (OR) and 95% confidence intervals (95% CI) of colorectal adenoma after adjusting for potential confounders.

RESULTS

Overall, there were no significant associations of the 2 5-LOX polymorphisms with the risk of colorectal adenoma. However, there was an inverse association between the Arg261Gln polymorphism in 12-LOX and colorectal adenoma (OR, 0.63; 95% CI, 0.40-1.00). A significant interaction also was observed between the 12-LOX polymorphism (Arg261Gln) and the use of nonsteroidal anti-inflammatory drugs (P(interaction) = .02).

CONCLUSIONS

The current results suggested that polymorphisms of LOX genes may act independently or with other factors to affect the risk of colorectal adenoma. Further studies will be needed to confirm these findings. Cancer 2007 (c) 2007 American Cancer Society.

Targeted chiral lipidomics analysis

Genomics, transcriptomics, and proteomics are proving to be very useful techniques, which have impacted significantly on our understanding mechanisms of human disease. However, this systems biology approach has several drawbacks than can be overcome by the integration of metabonomics and lipidomics. We have developed a targeted lipidomics approach that makes it possible to directly analyze chiral lipids generated in cellular systems. Bioactive lipids are usually present in trace amounts as enanatiomers and regioisomers that require separation before they can be analyzed by mass spectrometry. Normal phase chiral chromatography is generally used to resolve bioactive lipid enanatiomers. However, conventional electrospray and atmospheric pressure chemical ionization/tandem mass spectrometry have limited sensitivity when normal phase solvents are used, which makes it difficult to conduct studies when only trace amounts of the bioactive lipids are present. The use of electron capture atmospheric pressure chemical ionization/tandem mass spectrometry overcomes this problem. Enantiomers and regioisomers of targeted bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal phase chiral chromatography and electron capture atmospheric chemical ionization/tandem mass spectrometry. A targeted lipidomics profile from rat epithelial cells transfected with cyclooxygenase-2 and maintained in culture was obtained. Inhibition with the non-selective cyclooxygenase inhibitor aspirin increased the formation of 15(R)-hydroxyeicosatetraenoic acid in the cells although it completely inhibited formation of the 15(S)-enantiomer and prostaglandin E2. New mass spectrometry instrumentation with an improved atmospheric pressure chemical ionization source was found to be an order of magnitude more sensitive than existing instruments for analysis of bioactive lipids using electron capture methodology. This type of mass spectrometer will permit a more detailed analysis of cellular bioactive lipid production than has been possible previously. It will also permit in vivo targeted lipidomics studies to be conducted using biological fluids derived from animal models and human subjects.

Expression of Lipoxygenase in Human Bladder Carcinoma and Growth Inhibition by Its Inhibitors

PURPOSE

The metabolism of arachidonic acid by the cyclooxygenase or lipoxygenase pathway generates eicosanoids, which have been implicated in the pathogenesis of various human diseases, including cancer. They are now believed to have important roles in tumor promotion, progression and metastasis. The involvement of lipoxygenase expression and function in tumor growth and metastasis has been reported in human tumor cell lines.

MATERIALS AND METHODS

The expression of 5 and 12-lipoxygenase in patients with bladder tumor and chronic cystitis, and in normal bladder tissues was examined. We also examined the effects of their inhibitors on cell proliferation in a bladder cancer cell line. The expression of 5 and 12-lipoxygenase protein was detected by immunohistochemistry. The effects of lipoxygenase inhibitors on bladder cancer cell growth were examined by MTT (3-[4,5-dimethylthiazol-2-thiazolyl]-2,5-diphenyltetrazolium bromide) assay, while Hoechst (Sigma Chemical Co., St. Louis, Missouri) staining was used to determine whether lipoxygenase inhibitors induce apoptosis.

RESULTS

While slight 5 and 12-lipoxygenase expression was detected in chronic cystitis and normal bladder tissues, marked 5 and 12-lipoxygenase expression was detected in bladder cancer tissues. Lipoxygenase inhibitors caused marked inhibition of bladder cancer cells in a concentration and time dependent manner. Cells treated with lipoxygenase inhibitors showed chromatin condensation, cellular shrinkage, small membrane bound bodies (apoptotic bodies) and cytoplasmic condensation.

CONCLUSIONS

Lipoxygenase is induced in bladder cancer. Results suggest that lipoxygenase inhibitors may mediate potent antiproliferative effects against bladder cancer cells. Thus, lipoxygenase may become a new target in the treatment of bladder tumors.

Overexpression of leukocyte-type 12-lipoxygenase promotes W256 tumor cell survival by enhancing alphavbeta5 expression

The metabolism of arachidonic acid (AA) leads to the generation of biologically active metabolites that have been implicated in cell growth and proliferation, as well as survival and apoptosis. We have previously demonstrated that rat Walker 256 (W256) carcinosarcoma cells express the platelet-type 12-lipoxygenase (12-LOX) and synthesize 12(S)- and 15(S)-HETE as their major LOX metabolites. Here we show that Walker 256 cells also express leukocyte-type 12-LOX and that its overexpression in these cells significantly extends their survival and delays apoptosis when cells are cultured under serum-free conditions. Under serum-free conditions, the expression of leukocyte-type 12-LOX is upregulated. 12-LOX-transfected W256 cells had a more spread morphology in culture compared with wild-type or mock-transfected cells. Examination of W256 cells showed that the cells expressed a number of integrins on their surface. Overexpression of 12-LOX enhanced the surface expression and focal adhesion localization of integrin alphavbeta5, while not affecting other integrins. Also, the 12-LOX-transfected W256 cells exhibited higher levels of microfilament content. Treatment of cells with monoclonal antibody to alphavbeta5 or cytochalasin B (a microfilament-disrupting agent), but not antibodies to other integrin receptors, resulted in significant apoptosis, characterized by rapid rounding up and detachment from the substratum. These results show that the 12-LOX pathway is a regulator of cell survival and apoptosis, by affecting the expression and localization of the alphavbeta5 integrin and actin microfilaments in Walker 256 cells.

The Potential Contributions of Chronic Inflammation to Lung Carcinogenesis

A number of lines of evidence suggests that chronic inflammation contributes to the process of carcinogenesis. In this article, this theme is explored with particular emphasis on the involvement of inflammation in the development of lung cancer. A number of molecular pathways activated in chronic inflammation may contribute to lung carcinogenesis. The challenge is to conceptualize a cohesive picture of this complex biology that allows for effective pharmaceutical intervention. Initial therapeutic efforts involve strategies to block single pathways, such as with cyclooxygenase (COX) activity. However, the more that is learned about the consequences of COX activity, the more evident are the relationships of this enzyme to other classes of regulatory molecules such as the potent nuclear factor-kB. In light of this emerging picture, more global intervention strategies, such as with drug combinations, may be essential for success. Further basic study is essential to sort out possible molecular relationships and to permit elucidation of the most critical regulatory circuits. Given the complexity of these molecular interactions, well-designed clinical trials that specifically evaluate the precise effects of particular antiinflammatory drugs on lung carcinogenesis will also be critical to sort out the complexity and to validate successful approaches to arresting lung carcinogenesis.