Effects of Celebrex and Zyflo on liver metastasis and lipidperoxidation in pancreatic cancer in Syrian hamsters

Leukotrienes in Tumor-Associated Inflammation

Leukotrienes are biologically active eicosanoid lipid mediators that originate from oxidative metabolism of arachidonic acid. Biosynthesis of leukotrienes involves a set of soluble and membrane-bound enzymes that constitute a machinery complex primarily expressed by cells of myeloid origin. Leukotrienes and their synthetic enzymes are critical immune modulators for leukocyte migration. Increased concentrations of leukotrienes are implicated in a number of inflammatory disorders. More recent work indicates that leukotrienes may also interact with a variety of tissue cells, contributing to the low-grade inflammation of cardiovascular, neurodegenerative, and metabolic conditions, as well as that of cancer. Leukotriene signaling contributes to the active tumor microenvironment, promoting tumor growth and resistance to immunotherapy. This review summarizes recent insights into the intricate roles of leukotrienes in promoting tumor growth and metastasis through shaping the tumor microenvironment. The emerging possibilities for pharmacological targeting of leukotriene signaling in tumor metastasis are considered.

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

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

Inhibition of 5-lipoxygenase triggers apoptosis in pancreatic cancer cells

The 5-lipoxygenase (5-LOX) pathway has been associated with a variety of inflammatory diseases including asthma, atherosclerosis, rheumatoid arthritis, cancer and liver fibrosis. Several classes of 5-LOX inhibitors have been identified, but only one drug, zileuton, a redox inhibitor of 5-LOX, has been approved for clinical use. In the present study, 5-LOX was found to be overexpressed not only in pancreatic cancer cell lines but also in tissue samples of patients suffering from pancreatic adenocarcinoma. There was a close correlation between the tumor expression levels of 5-LOX mRNA and protein and the clinicopathological patient characteristics including lymph node metastasis and TNM stage. Zileuton suppressed the proliferation of SW1990 cells in a concentration- and time‑dependent manner. In addition, zileuton induced SW1990 cells to undergo apoptosis and significantly decreased 5-LOX expression. The number of apoptotic cells, estimated by flow cytometry, Annexin V/PI assay, TUNEL staining and sub‑diploid population was significantly higher than that of the control. These results suggest that the level of 5-LOX expression was increased in pancreatic cancer tissues and may be related to lymph node metastasis and TNM stage.

Regulation of inflammation in cancer by eicosanoids

Inflammation in the tumor microenvironment is now recognized as one of the hallmarks of cancer. Endogenously produced lipid autacoids, locally acting small molecule lipid mediators, play a central role in inflammation and tissue homeostasis, and have recently been implicated in cancer. A well-studied group of autacoid mediators that are the products of arachidonic acid metabolism include: the prostaglandins, leukotrienes, lipoxins and cytochrome P450 (CYP) derived bioactive products. These lipid mediators are collectively referred to as eicosanoids and are generated by distinct enzymatic systems initiated by cyclooxygenases (COX 1 and 2), lipoxygenases (5-LOX, 12-LOX, 15-LOXa, 15-LOXb), and cytochrome P450s, respectively. These pathways are the target of approved drugs for the treatment of inflammation, pain, asthma, allergies, and cardiovascular disorders. Beyond their potent anti-inflammatory and anti-cancer effects, non-steroidal anti-inflammatory drugs (NSAIDs) and COX-2 specific inhibitors have been evaluated in both preclinical tumor models and clinical trials. Eicosanoid biosynthesis and actions can also be directly influenced by nutrients in the diet, as evidenced by the emerging role of omega-3 fatty acids in cancer prevention and treatment. Most research dedicated to using eicosanoids to inhibit tumor-associated inflammation has focused on the COX and LOX pathways. Novel experimental approaches that demonstrate the anti-tumor effects of inhibiting cancer-associated inflammation currently include: eicosanoid receptor antagonism, overexpression of eicosanoid metabolizing enzymes, and the use of endogenous anti-inflammatory lipid mediators. Here we review the actions of eicosanoids on inflammation in the context of tumorigenesis. Eicosanoids may represent a missing link between inflammation and cancer and thus could serve as therapeutic target(s) for inhibiting tumor growth.

Experimental animal models of pancreatic carcinogenesis for prevention studies and their relevance to human disease

Pancreatic cancer is difficult to cure, so its prevention is very important. For this purpose, animal model studies are necessary to develop effective methods. Injection of N-nitrosobis(2-oxopropyl)amine (BOP) into Syrian golden hamsters is known to induce pancreatic ductal adenocarcinomas, the histology of which is similar to human tumors. Moreover, K-ras activation by point mutations and p16 inactivation by aberrant methylation of 5' CpG islands or by homozygous deletions have been frequently observed in common in both the hamster and humans. Thus, this chemical carcinogenesis model has an advantage of histopathological and genetic similarity to human pancreatic cancer, and it is useful to study promotive and suppressive factors. Syrian golden hamsters are in a hyperlipidemic state even under normal dietary conditions, and a ligand of peroxizome proliferator-activated receptor gamma was found to improve the hyperlipidemia and suppress pancreatic carcinogenesis. Chronic inflammation is a known important risk factor, and selective inhibitors of inducible nitric oxide synthase and cyclooxygenase-2 also have protective effects against pancreatic cancer development. Anti-inflammatory and anti-hyperlipidemic agents can thus be considered candidate chemopreventive agents deserving more attention.

Eicosanoids and cancer

Eicosanoids, including prostaglandins and leukotrienes, are biologically active lipids that have been implicated in various pathological processes, such as inflammation and cancer. This Review highlights our understanding of the intricate roles of eicosanoids in epithelial-derived tumours and their microenvironment. The knowledge of how these lipids orchestrate the complex interactions between transformed epithelial cells and the surrounding stromal cells is crucial for understanding tumour evolution, progression and metastasis. Understanding the molecular mechanisms underlying the role of prostaglandins and other eicosanoids in cancer progression will help to develop more effective cancer chemopreventive and/or therapeutic agents.

Action of Celecoxib on Hepatic Metabolic Changes Induced by the Walker-256 Tumour in Rats

The purpose of the present work was to investigate the influence of celecoxib on some hepatic metabolic parameters affected by the Walker-256 tumour in rats. Celecoxib was administered daily (5-50 mg/kg body weight) beginning at the day in which the tumour cells were inocculated. At day 14, the liver was isolated and perfused in order to measure alanine transformation, glycolysis and arginine transformation. Maximal reduction of tumour growth (75%), accompanied by an almost normal weight gain, was attained with a celecoxib dose of 12.5 mg/kg. Diminution of glucose utilization (glycolysis) and inhibition of gluconeogenesis and ureogenesis from alanine caused by the tumor were totally reversed by celecoxib. Oxygen uptake by the liver was also normalized by the drug. Hepatic arginine transformation, which is normally enhanced in rats bearing the Walker-256 tumour, remained elevated in celecoxib-treated animals. It was concluded that preservation of gluconeogenesis and normalization of hepatic glucose utilization can explain, partly at least, the clinical improvement of cancer patients treated with the drug. The lack of action of celecoxib on arginine hydrolysis might indicate that reduction in polyamine synthesis is not a factor contributing to the diminished tumour growth.

A novel copper complex induces ROS generation in doxorubicin resistant Ehrlich ascitis carcinoma cells and increases activity of antioxidant enzymes in vital organs in vivo

Background

In search of a suitable GSH-depleting agent, a novel copper complex viz., copper N-(2-hydroxyacetophenone) glycinate (CuNG) has been synthesized, which was initially found to be a potential resistance modifying agent and later found to be an immunomodulator in mice model in different doses. The objective of the present work was to decipher the effect of CuNG on reactive oxygen species (ROS) generation and antioxidant enzymes in normal and doxorubicin-resistant Ehrlich ascites carcinoma (EAC/Dox)-bearing Swiss albino mice.

Methods

The effect of CuNG has been studied on ROS generation, multidrug resistance-associated protein1 (MRP1) expression and on activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx).

Results

CuNG increased ROS generation and reduced MRP1 expression in EAC/Dox cells while only temporarily depleted glutathione (GSH) within 2 h in heart, kidney, liver and lung of EAC/Dox bearing mice, which were restored within 24 h. The level of liver Cu was observed to be inversely proportional to the level of GSH. Moreover, CuNG modulated SOD, CAT and GPx in different organs and thereby reduced oxidative stress. Thus nontoxic dose of CuNG may be utilized to reduce MRP1 expression and thus sensitize EAC/Dox cells to standard chemotherapy. Moreover, CuNG modulated SOD, CAT and and GPx activities to reduce oxidative stress in some vital organs of EAC/Dox bearing mice. CuNG treatment also helped to recover liver and renal function in EAC/Dox bearing mice.

Conclusion

Based on our studies, we conclude that CuNG may be a promising candidate to sensitize drug resistant cancers in the clinic.

Chemoprevention of pancreatic cancer: a review of the molecular pathways involved, and evidence for the potential for chemoprevention

BACKGROUND

Pancreatic cancer has a poor prognosis. The use of drugs or natural agents which inhibit or slow down tumour growth therefore has important potential in the development of future therapies.

METHODS

A literature search of the PubMed and ISI Web of Science databases was undertaken to review the current data available on the alterations in signalling pathways found in pancreatic carcinogenesis, in order to identify sites that could be targeted by chemopreventive agents. Several agents of particular relevance to pancreatic cancer were identified, and their possible mechanisms of action reviewed.

RESULTS

Chemopreventive agents such as non-steroidal anti-inflammatory drugs, green tea constituents, and antioxidants have been shown to target various steps in intracellular signalling pathways, particularly those controlling cell proliferation and survival. Work on cell lines and animal models has shown that some of these agents may be able to modulate the growth of pancreatic tumours. Initial clinical trials of some chemopreventives in pancreatic cancer have been undertaken, and have yielded mixed results, prompting the need for further studies.

CONCLUSION

As the molecular pathology of pancreatic cancer becomes better understood, sites of action of chemopreventive substances have been uncovered. Several agents have shown promising results by their ability to inhibit pancreatic carcinogenesis in laboratory studies. If these effects can be successfully translated into human studies then these agents may prove to be valuable adjuvant therapies in the future.

Role of inflammation in pancreatic carcinogenesis and the implications for future therapy

BACKGROUND

The link between inflammation and pancreatic cancer has been observed for a number of gastrointestinal neoplasms. This review examines the role of inflammation in pancreatic carcinogenesis and how it can be utilised to develop new therapies against pancreatic cancer.

METHODS

A literature review of Pubmed, Medline and Web of Science databases was undertaken using the key words, pancreatic cancer, inflammation, inducible nitric oxide, interleukins, pro-inflammatory cytokines, cyclooxygenase-2, NF-kappa B, reactive oxygen species, DNA adducts, lipoxygenases, chemoprevention.

RESULTS

Epidemiological evidence and molecular studies both in vitro and in vivo all support the hypothesis that inflammation plays an important in the initiation and progression of pancreatic tumours.

CONCLUSION

Sustained damage caused by chronic inflammation may precede the onset of frank malignancy by a significant interval. As such, suppression of inflammatory changes and oxidative damage, may help delay or even prevent the inception of pancreatic neoplasia.

Celecoxib: a potent cyclooxygenase-2 inhibitor in cancer prevention

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used therapeutic agents in the treatment of pain, inflammation and fever. They may also have a role in the management of cancer prevention, Alzheimer's disease and prophylaxis against cardiovascular disease. These drugs act primarily by inhibiting cyclooxygenase enzyme, which has two isoforms, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Selective COX-2 inhibitors provide potent anti-inflammatory and analgesic effects without the side effects of gastric and renal toxicity and inhibition of platelet function. Celecoxib is a potent COX-2 inhibitor being developed for the treatment of rheumatoid arthritis and osteoarthritis. Chemoprevention is the use of pharmacological or natural agents to prevent, suppress, interrupt or reverse the process of carcinogenesis. For this purpose, celecoxib is being used for different cancer types. The effects of NSAIDs on tumor growth remain unclear, but are most likely to be multifocal. In this article, we reviewed COX-2 selectivity, the pharmacological properties of celecoxib, the use of celecoxib for cancer prevention and the mechanisms of chemoprevention.

Regulation of cell growth by selective COX-2 inhibitors in oral carcinoma cell lines

Evidence indicates that NSAIDs that inhibit prostaglandin (PG) synthesis can reduce the incidence of colorectal cancers and that inhibition of cyclooxygenase-2 (COX-2) may be the underlying mechanism. The objective of this study was to investigate this putative mechanism by examining the effect of selective COX-2 inhibitors (Celebrex, DFU, NS-398) and COX-1 inhibitors (Aspirin) on the growth of two human oral carcinoma cell lines (OEC-M1 and KB) and one normal fibroblast cell line (NF). We found that the growth of OEC-M1 cells could be significantly inhibited by DFU concentrations above 30 microM (31%) after 4 days, and above 50 microM (35%) after 2 days in culture; by Celebrex at concentrations above 20 microM (52%) after 6 days, above 30 microM (36%) after 5 days, and above 40 microM (33%) after 4 days in culture; and by NS-398 above 1 microM (30%) after 6 days, and above 10 microM (35%) after 5 days in culture. The growth of KB cells could be significantly inhibited by DFU concentrations above 10 microM (33%) after 6 days, above 20 microM (35%) after 4 days in culture; and by Celebrex at concentrations above 10 microM (33%) after 5 days, and above 50 microM (30%) after 4 days in culture; and by NS-398 above 1 microM (45%) after 5 days, above 20 microM (36%) after 4 days in culture. The growth of NF cells could be significantly inhibited by DFU above 30 microM (45%) after 6 days, and above 40 microM (32%) after 3 days in culture, and by Celebrex at concentrations above 10 microM (42%) after 6 days, above 30 microM (31%) after 4 days, above 50 microM (32%) after 3 days in culture, and by NS-398 above 0.1 microM (35%) after 4 days, and above 1 microM (32%) after 3 days in culture. The growth-inhibitory concentration (IC50) values for DFU on OEC-M1, KB, and NF cells were about 39.1, 14.8, and 42.9 microM at 144 h, respectively, and on KB was about 45.2 microM at 120 h. The IC50 values for Celebrex on OEC-M1, KB, and NF cells were about 19.1, 8.6, and 15.8 microM at 144 h, respectively, and on KB and NF were about 27.7 and 35.3 microM, respectively, at 120 h. The IC50 values for NS-398 on OEC-M1, KB, and NF were about 18.9, 0.7 and 1 microM, respectively, at 144 h; on KB and NF values were about 10.8 and 1.4 microM, respectively, at 120 h and on KB and NF were about 26.6 and 4.1 microM, respectively, at 96 h. The results show that the growth of these cell lines is inhibited by three COX-2 selective inhibitors but not by any COX-1 selective inhibitors. These findings suggest that COX-2 may play an important role in the generation of biochemical mediators that stimulate the growth of human oral cancer and normal fibroblast cell lines.