The future of cyclooxygenase-2 inhibitors and other inhibitors of the eicosanoid signal pathway in the prevention and therapy of lung cancer

Shrimp lipids: a source of cancer chemopreventive compounds

Shrimp is one of the most popular seafoods worldwide, and its lipids have been studied for biological activity in both, muscle and exoskeleton. Free fatty acids, triglycerides, carotenoids, and other lipids integrate this fraction, and some of these compounds have been reported with cancer chemopreventive activities. Carotenoids and polyunsaturated fatty acids have been extensively studied for chemopreventive properties, in both in vivo and in vitro studies. Their mechanisms of action depend on the lipid chemical structure and include antioxidant, anti-proliferative, anti-mutagenic, and anti-inflammatory activities, among others. The purpose of this review is to lay groundwork for future research about the properties of the lipid fraction of shrimp.

Beyond DNA binding - a review of the potential mechanisms mediating quinacrine's therapeutic activities in parasitic infections, inflammation, and cancers

This is an in-depth review of the history of quinacrine as well as its pharmacokinetic properties and established record of safety as an FDA-approved drug. The potential uses of quinacrine as an anti-cancer agent are discussed with particular attention to its actions on nuclear proteins, the arachidonic acid pathway, and multi-drug resistance, as well as its actions on signaling proteins in the cytoplasm. In particular, quinacrine's role on the NF-κB, p53, and AKT pathways are summarized.

Combination Therapy of PPARgamma Ligands and Inhibitors of Arachidonic Acid in Lung Cancer

Lung cancer is the leading cause of cancer death in the United States and five-year survival remains low. Numerous studies have shown that chronic inflammation may lead to progression of carcinogenesis. As a result of inflammatory stimulation, arachidonic acid (AA) metabolism produces proliferation mediators through complex and dynamic interactions of the products of the LOX/COX enzymes. One important mediator in the activation of the AA pathways is the nuclear protein PPARgamma. Targeting LOX/COX enzymes and inducing activation of PPARgamma have resulted in significant reduction of cell growth in lung cancer cell lines. However, specific COX-inhibitors have been correlated with an increased cardiovascular risk. Clinical applications are still being explored with a novel generation of dual LOX/COX inhibitors. PPARgamma activation through synthetic ligands (TZDs) has revealed a great mechanistic complexity since effects are produced through PPARgamma-dependent and -independent mechanisms. Furthermore, PPARgamma could also be involved in regulation of COX-2. Overexpression of PPARgamma has reported to play a role in control of invasion and differentiation. Exploring the function of PPARgamma, in this new context, may provide a better mechanistic model of its role in cancer and give an opportunity to design a more efficient therapeutic approach in combination with LOX/COX inhibitors.

Analysis of orthologous gene expression between human pulmonary adenocarcinoma and a carcinogen-induced murine model

Human adenocarcinoma (AC) is the most frequently diagnosed human lung cancer, and its absolute incidence is increasing dramatically. Compared to human lung AC, the A/J mouse-urethane model exhibits similar histological appearance and molecular changes. We examined the gene expression profiles of human and murine lung tissues (normal or AC) and compared the two species' datasets after aligning approximately 7500 orthologous genes. A list of 409 gene classifiers (P value <0.0001), common to both species (joint classifiers), showed significant, positive correlation in expression levels between the two species. A number of previously reported expression changes were recapitulated in both species, such as changes in glycolytic enzymes and cell-cycle proteins. Unexpectedly, joint classifiers in angiogenesis were uniformly down-regulated in tumor tissues. The eicosanoid pathway enzymes prostacyclin synthase (PGIS) and inducible prostaglandin E(2) synthase (PGES) were joint classifiers that showed opposite effects in lung AC (PGIS down-regulated; PGES up-regulated). Finally, tissue microarrays identified the same protein expression pattern for PGIS and PGES in 108 different non-small cell lung cancer biopsies, and the detection of PGIS had statistically significant prognostic value in patient survival. Thus, the A/J mouse-urethane model reflects significant molecular details of human lung AC, and comparison of changes in orthologous gene expression may provide novel insights into lung carcinogenesis.

Modification of eicosanoid profile in human blood treated by dual COX/LOX inhibitors

The arachidonic acid metabolizing enzymes, the cyclooxygenases (COXs) and lipoxygenases (LOXs), have been implicated in the development of a variety of cancers and numerous new therapeutic inhibitors are currently under investigation. However, given the interdependence of the two pathways, the effect of inhibiting one pathway with relatively selective agents can only be appreciated in the in vivo situation. Clearly then, because of their potential beneficial or deleterious effects, it is important to understand the nature and levels of the resulting arachidonic acid metabolites when treating patients with relatively selective inhibitor drugs. In this study, using reference COX-2, 5-LOX and dual COX-2/5-LOX inhibitors, we devised a protocol which permitted the simultaneous quantification of eicosanoid metabolites formed during stimulation of human peripheral venous blood samples with the calcium ionophore, A23187, in the absence and presence of lipopolysaccharide (LPS). Not surprisingly, the end products of both COX and LOX pathways were affected depending on the inhibitor, or combination of inhibitors, used and the concentrations of drug tested. In conclusion, the method described permits the rapid screening of novel compounds for potentially positive and/or negative effects upon the products of arachidonic acid metabolism.

Lung cancer: genetics of risk and advances in chemoprevention

PURPOSE OF REVIEW

The current article reviews recent advances in genetic susceptibility and chemoprevention of lung cancer.

RECENT FINDINGS

Linkage analysis has identified a locus on chromosome 6q23-25 that determines susceptibility to lung cancer in families with multiple members with cancer of the lung, throat, and larynx. Obligate gene carriers are sensitive to even small tobacco smoke exposure in terms of increased lung cancer risk. Variation in other genes, particularly those regulating the activation or inactivation of carcinogens, has been implicated in determining lung cancer risk. Epidemiologic and preclinical studies suggest that chemoprevention of lung cancer is an achievable goal. Early trials with beta-carotene supplementation, however, have revealed a harmful effect. Promising new agents must be evaluated in both preclinical models and in intermediate end point biomarker trials before being taken to large primary prevention trials, and lung cancer chemoprevention should only be attempted within controlled clinical trials.

SUMMARY

We are poised to learn a great deal about the genetic susceptibility to lung cancer, which will not only allow definition of groups with extremely high risk, but may also yield new insights into processes that determine innate susceptibility or resistance to lung carcinogenesis. Chemoprevention of lung cancer is not yet ready for clinical application. As a result of the large number of lung cancer deaths and the large number of at-risk individuals, even modestly effective chemoprevention could save many lives.

Death Receptor Regulation and Celecoxib-Induced Apoptosis in Human Lung Cancer Cells

BACKGROUND

Celecoxib, a cyclooxygenase 2 inhibitor, has chemopreventive and therapeutic activities toward lung cancer and other epithelial malignancies. Celecoxib can induce apoptosis in various cancer cell lines through a mechanism that is independent of its cyclooxygenase 2 inhibitory activity but is otherwise largely uncharacterized. We investigated the mechanism of celecoxib-induced apoptosis further.

METHODS

All experiments were conducted in human non-small-cell lung carcinoma (NSCLC) cell lines; results in celecoxib-treated and untreated cells were compared. Cell survival was assessed with a sulforhodamine B assay. Apoptosis was assessed by DNA fragmentation with an enzyme-linked immunosorbent assay, by terminal deoxynucleotidyltransferase-mediated dUTP nick-end-labeling (TUNEL) assay, and by western blot analysis of caspase activation. Death receptor gene and protein expression was detected by northern and western blot analysis, respectively. Gene silencing was achieved with small interfering RNA (siRNA) technology.

RESULTS

Celecoxib treatment decreased cell survival, activated caspase cascades, and increased DNA fragmentation, all of which were abrogated when caspase 8 expression was silenced with caspase 8 siRNA. Celecoxib treatment induced the expression of death receptors, particularly that of DR5. Overexpression of a dominant negative Fas-associated death domain mutant, but not of BCL2, reduced the level of celecoxib-induced apoptosis, and silencing of DR5 expression by DR5 siRNA suppressed celecoxib-induced caspase 8 activation and apoptosis. Combination treatment with celecoxib and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induced additional apoptosis. For example, survival of A549 cells was decreased with 50 muM celecoxib alone by 38.7% (95% confidence interval [CI] = 35.2% to 42.2%), with TRAIL alone by 29.3% (95% CI = 25.1% to 33.6%), but with their combination by 77.5% (95% CI = 74.5% to 79.5%), a greater than additive effect.

CONCLUSION

Celecoxib appears to induce apoptosis in human NSCLC through the extrinsic death receptor pathway.

Chemoprevention of lung cancer--from biology to clinical reality

Lung cancer is the commonest cause of cancer death in developed countries and throughout the world. Cigarette smoking is the main risk factor for lung cancer and ex-smokers today comprise approximately 50% of all new lung cancer cases. Chemoprevention builds on the concepts of field of cancerization and multistep carcinogenesis and can be defined as the use of natural or chemical compounds to prevent, inhibit or reverse the process of carcinogenesis. So far, chemoprevention studies in lung cancer have failed to reduce lung cancer mortality. New developments in biotechnology have made it possible to define more accurately high-risk populations, make earlier diagnosis possible, and allow more specific targeted therapies to be developed. Both the development and validation of biomarkers, for the selection of high-risk study populations and for response evaluation in chemoprevention studies, are important for the faster turnover of studies evaluating new agents. This article reviews the current status and describes the perspectives for new approaches in the chemoprevention of lung cancer.

Lung cancer chemoprevention: moving from concept to a reality

Vast numbers of individuals who have stopped smoking have already been exposed to critical amounts of tobacco combustion products and are at significant risk of developing lung cancer. If these individuals are diagnosed with regional or distant metastatic disease this condition is not typically curable with existing systemic therapy. The need for more effective tools to detect and intervene with early lung cancer detection is a pressing public health priority. A major challenge in this regard is the development of safe and effective lung cancer chemoprevention. The factors influencing the development of this new clinical tool are reviewed in the context of existing trends for lung cancer care. Existing pharmaceutical efforts have involved evaluation of existing treatments for advanced cancer or other disorders in early lung cancer. The paper describes approaches to tailor chemoprevention development specifically to the biological, pharmacological and anatomical realities of this most lethal cancer.