A phase II study of the 5-lipoxygenase inhibitor, CV6504, in advanced pancreatic cancer: correlation of clinical data with pharmacokinetic and pharmacodynamic endpoints

Anti-proliferative and pro-apoptotic effects of lichen-derived compound protolichesterinic acid are not mediated by its lipoxygenase-inhibitory activity

Lipoxygenases (LOXs) and their products are involved in several biological functions and have been associated with carcinogenesis. Protolichesterinic acid (PA), a lichen metabolite, inhibits 5- and 12-LOX and has anti-proliferative effects on various cancer cell lines. Here, PA was shown to inhibit proliferation of multiple myeloma cells, RPMI 8226 and U266, and pancreatic cancer cells AsPC-1. Apoptosis was induced only in multiple myeloma cells. Cell-cycle associated changes in expression and sub-cellular localization of 5- and 12-LOX were not affected by PA but increased cytoplasmic localisation was found to accompany morphological changes at later stages. Assessment by mass spectrometry showed that PA entered the pancreatic cancer cells. However, effects on LOX metabolites were only evident after treatment with concentrations exceeding those having anti-proliferative effects and no effects were measurable in the myeloma cells. We conclude that the anti-proliferative and pro-apoptotic effects of PA are not mediated directly through inhibition of LOX activity.

Mechanisms of cancer cachexia

Up to 50% of cancer patients suffer from a progressive atrophy of adipose tissue and skeletal muscle, called cachexia, resulting in weight loss, a reduced quality of life, and a shortened survival time. Anorexia often accompanies cachexia, but appears not to be responsible for the tissue loss, particularly lean body mass. An increased resting energy expenditure is seen, possibly arising from an increased thermogenesis in skeletal muscle due to an increased expression of uncoupling protein, and increased operation of the Cori cycle. Loss of adipose tissue is due to an increased lipolysis by tumor or host products. Loss of skeletal muscle in cachexia results from a depression in protein synthesis combined with an increase in protein degradation. The increase in protein degradation may include both increased activity of the ubiquitin-proteasome pathway and lysosomes. The decrease in protein synthesis is due to a reduced level of the initiation factor 4F, decreased elongation, and decreased binding of methionyl-tRNA to the 40S ribosomal subunit through increased phosphorylation of eIF2 on the alpha-subunit by activation of the dsRNA-dependent protein kinase, which also increases expression of the ubiquitin-proteasome pathway through activation of NFkappaB. Tumor factors such as proteolysis-inducing factor and host factors such as tumor necrosis factor-alpha, angiotensin II, and glucocorticoids can all induce muscle atrophy. Knowledge of the mechanisms of tissue destruction in cachexia should improve methods of treatment.

Differential modulation of leukotriene B4 synthesis and degradation in human bronchoalveolar lavage cells by lipopolysaccharide and tobacco smoke

Leukotrienes have been implicated to play a prominent inductive role in carcinogenesis. We previously reported that bronchoalveolar lavage (BAL) cells from smokers manifested higher levels of leukotriene B4 (LTB4) production than ex-smokers. This study aims to elucidate the underlying mechanism(s). BAL cells from current and former smokers were exposed to lipopolysaccharide (LPS) for up to 7 days. LPS induced the release of LTB4 from BAL cells and down-regulated 5-lipoxygenase (5-LOX) mRNA expression in a dose-dependent manner, followed by a decrease in 5-LOX protein production and normalization of LTB4 levels. Exogenous LTB4 inhibited LPS-induced 5-LOX activity and accentuated the down-regulation of 5-LOX mRNA, whereas suppression of 5-LOX abrogated the LPS-induced changes, suggesting a negative feedback mechanism. LPS concomitantly induced expression and activity of the LTB4 metabolizing enzyme LTB4 omega-hydroxylase (LTB4OH) in ex-smokers' BAL cells, but not in smokers' BAL cells. In vitro smoke exposure of ex-smokers' BAL cells also abrogated the LPS-induced up-regulation of LTB4OH mRNA expression. Furthermore, ex-smokers' BAL cells expressed significantly higher LTB4OH mRNA levels than smokers' BAL cells. Such differential modulation of LTB4 synthesis and degradation by LPS in the setting of tobacco smoke exposure suggests that mechanisms responsible for sustained elevation of LTB4 levels in the lung microenvironment may contribute to the pathogenesis of tobacco-related respiratory diseases such as lung cancer. By regulating the balance of LTB4 in the lung, LTB4OH may function as a suppressor of lung carcinogenesis.

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.

Therapeutic options for 5-lipoxygenase inhibitors

5-Lipoxygenase (5-LO) catalyzes the conversion of arachidonic acid (AA) into leukotriene (LT) A(4) and 5-hydroperoxyeicosatetraenoic acid. LTA(4) can then be converted into LTB(4) by LTA(4) hydrolase or into LTC(4) by LTC(4) synthase and the LTC(4) synthase isoenzymes MGST2 and MGST3. LTB(4) is a potent chemoattractant for neutrophils, eosinophils and monocytes leading to adherence of phagocytes to vessel walls, neutrophil degranulation and release of superoxide anions. LTC(4) and its metabolite, LTD(4), are potent bronchoconstrictors that increase vascular permeability and stimulate mucus secretion from airways. Recent data also suggest that LT have an immunomodulatory role. Due to these properties, the increased biosynthesis of LT in asthma, and based upon clinical data obtained with CysLT(1) receptor antagonists in asthma patients, there is a consensus that CysLT play a prominent role in asthma. In this review, we summarize the knowledge on possible functions of the 5-LO pathway in various diseases like asthma, cancer and cardiovascular events and review the corresponding potential therapeutic roles of 5-LO inhibitors.

Emerging drugs in pancreatic cancer

Improving survival in patients with pancreatic cancer remains a formidable challenge. For the few patients with localised stages of the disease, intra-operative radiotherapy, adjuvant chemoradiotherapy and neo-adjuvant therapies remain non-validated and the survival benefit conferred by 5-fluorouracil-folinic acid adjuvant chemotherapy over radical surgery alone is still a matter of debate. Gemcitabine has recently emerged as the standard single agent in advanced stages of the disease and pharmacokinetic refinements such as the use of a fixed-dose infusion rate may further improve still rather modest result figures. At present, most efforts deal with the development of more effective doublet or triplet therapies, combining gemcitabine with either conventional cytotoxic drugs--the most promising being oxaliplatin--or more innovative, targeted therapeutic agents. Among these agents, matrix metalloprotease inhibitors and farnesyltransferase inhibitors have already undergone Phase III trials, alone or in combination with gemcitabine, with rather disappointing results. However, preclinical and Phase I and II studies of cyclooxygenase-2 or lipoxygenase inhibitors, various immunotherapeutic approaches and several tyrosine kinase inhibitors or monoclonal antibodies against growth factors or their receptors are encouraging and may provide some hope for patients with pancreatic cancer.

Modulation of pulmonary leukotriene B4 production by cyclooxygenase-2 inhibitors and lipopolysaccharide

PURPOSE

Emerging data continue to link carcinogenesis to inflammatory events involving the eicosanoid metabolic pathways. We therefore evaluated the effects of cyclooxygenase (COX)-2 inhibition on leukotriene (LT) B(4) synthesis in the lungs of active smokers, as part of a pilot lung cancer chemoprevention study with celecoxib (Celebrex), an oral COX-2 inhibitor.

EXPERIMENTAL DESIGN

Bronchoalveolar lavage was performed before celecoxib treatment and after 1 month of celecoxib treatment to recover alveolar macrophages (AMs) and lining fluid for study. After harvest, AMs were immediately stimulated in vitro with the calcium ionophore A23187. AMs obtained from smokers before treatment and from ex-smoker control subjects were also cultured overnight with SC58236, a selective COX-2 inhibitor, with or without lipopolysaccharide stimulation.

RESULTS

Treatment with oral celecoxib only modestly increased LTB(4) levels in bronchoalveolar lavage, without increasing the mRNA transcription of 5-lipoxygenase (5-LOX) or 5-LOX-activating protein in AMs, whereas the acute calcium ionophore-stimulated LTB(4) production from smokers' AMs was markedly increased by 10.6-fold. In addition, smokers' AMs were twice as responsive in producing LTB(4) when exposed to lipopolysaccharide compared with ex-smokers' AMs. Concomitant COX-2 inhibition with SC58236, however, did not significantly impact these changes, whereas the 5-LOX inhibitor Zileuton blocked the generation of LTB(4) in a dose-responsive manner. Finally, cycloheximide increased the production of LTB(4) under all conditions, suggesting a shunting phenomenon and/or the presence of pathway inhibitors.

CONCLUSIONS

Our findings suggest that whereas oral celecoxib is capable of modulating LTB(4) production in the lung microenvironment, under physiologic conditions, this effect is probably not functionally significant.

Old and new drugs in systemic therapy of pancreatic cancer

BACKGROUND

The incidence of pancreatic cancer nearly equals its death rate (97%). Two-year survival is about 10%. Chemotherapy treatment is problematic because of the palliative and limited duration of response.

MATERIAL AND METHODS

The article analyzes the objective response and median survival time (MST) for old and new drugs in the treatment of pancreatic cancer.

RESULTS

The most encouraging results to date come from studies of 5-fluorouracil (5FU) as an adjuvant therapy and of gemcitabine in the advanced disease, which is one of the most active and best tolerated drugs in recent years. However, with the introduction of new drugs or with different old drug associations, interesting results are also becoming evident.

CONCLUSIONS

New approaches to CT treatment are necessary. Patient enrollment into rigorous and well conducted clinical trials, either at tumor diagnosis or after tumor recurrence, will generate new information regarding investigational therapies and it will offer improved therapies for patients with this disease.

Review article: chemotherapy for pancreatic cancer

Pancreatic cancer is a common, highly lethal disease that is rising in incidence. Chemotherapy based on 5-fluorouracil (5-FU) has been shown to prolong survival in advanced pancreatic cancer. Gemcitabine improves major symptoms and survival outcomes compared with bolus 5-FU. Many novel small molecules are being widely and actively researched. These compounds are based on classical mechanisms of action as well as biological therapies targeting novel cellular survival pathways, and include fluoropyrimidines, nucleoside cytidine analogues, platinum analogues, topoisomerase-inhibitors, antimicrotubule agents, proteasome inhibitors, vitamin D analogues, arachidonic acid pathway inhibitors, histone deacytylator inhibitors, farnesyltransferase inhibitors and epidermal growth factor receptor therapies. Adjuvant chemotherapy has also demonstrated the best survival outcomes following resection compared to other adjuvant or neo-adjuvant strategies such as radiation-based treatments. These benefits are superimposed on the dramatic increase in resectability rates and reduction in post-operative mortality achieved by centralisation of treatment in high-volume speciality centres. Newer 'small-molecule' drugs as well as the latest 'large-molecule' biological agents hold considerable promise for the future. Real advances are anticipated over the next five years but are dependent on large randomised controlled trials for success.

Adjuvant therapy in pancreatic cancer: historical and current perspectives

The results from pancreatic ductal adenocarcinoma appear to be improving with increased resection rates and reduced postoperative mortality reported by specialist pancreatic cancer teams. Developments with medical oncological treatments have been difficult, however, due to the fundamentally aggressive biological nature of pancreatic cancer and its resistance to chemotherapy coupled with a relative dearth of randomised controlled trials. The European Study Group for Pancreatic Cancer (ESPAC)-1 trial recruited nearly 600 patients and is the largest trial in pancreatic cancer. The results demonstrated that the current best adjuvant treatment is chemotherapy using bolus 5-fluorouracil with folinic acid. The median survival of patients randomly assigned to chemoradiotherapy was 15.5 months and is comparable with many other studies, but the median survival in the chemotherapy arm was 19.7 months and is as good or superior to multimodality treatments including intra-operative radiotherapy, adjuvant chemoradiotherapy and neo-adjuvant therapies. The use of adjuvant 5-fluorouracil with folinic acid may be supplanted by gemcitabine but requires confirmation by ongoing clinical trials, notably ESPAC-3, which plans to recruit 990 patients from Europe, Canada and Australasia. Major trials such as ESPAC-1 and ESPAC-3 have set new standards for the development of adjuvant treatment and it is now clear that such treatment in this field has the potential to significantly improve both patient survival and quality of life after curative resection.

Breast cancer cell-derived EMMPRIN stimulates fibroblast MMP2 release through a phospholipase A(2) and 5-lipoxygenase catalyzed pathway

Metalloproteinases (MMP) produced by both cancer and normal stromal fibroblast cells play a critical role in the metastatic spread of tumours, however little is known of the regulation of their release. In this report we demonstrate that breast cancer cells in culture release apparently full length soluble EMMPRIN that promotes the release of pro-MMP2 from fibroblasts. The generation of MMP2 is mediated by activation of phospholipase A(2) and 5-lipoxygenase. These results suggest that the production of soluble EMMPRIN, phospholipase A(2) and 5-lipoxygenase activities are sites for potential therapeutic intervention.

Cyclooxygenases and lipoxygenases as potential targets for treatment of pancreatic cancer

Pancreatic adenocarcinoma is characterized by poor prognosis, late diagnosis and lack of response to conventional therapies. The incidence of this disease shows no sign of declining in the Western world. Thus, new targets need to be identified for pancreatic cancer treatment. In particular, new chemotherapeutic agents would be extremely beneficial for control of unresectable cancer and metastatic lesions as well as for prevention of this deadly disease. Mounting evidence suggests that both lipoxygenases (LOXs) and cyclooxygenases (COXs), the key enzymes for arachidonic acid metabolism, have a profound influence on the development and progression of several human cancers. Recent evidence suggests that both COX and LOX pathways are important in pancreatic cancer. Results from immunocytochemical, RT-PCR, and Western blotting studies have shown that COX, specifically COX-2, is upregulated in human pancreatic cancer cell lines as well as human pancreatic cancer tissues compared with normal ductal cells and normal pancreas specimens. Agents that block COX enzymes significantly inhibit pancreatic cancer growth both in vitro and in vivo, in parallel with induction of apoptosis. Expression of both 5-LOX and 12-LOX is also seen in pancreatic cancer, although compared to the expression of COX this has not been extensively investigated. Chemical inhibitors or antisense oligonucleotides that block either 5-LOX or 12-LOX cause marked inhibition of pancreatic cancer cell proliferation. On the other hand, LOX metabolites stimulate growth of the tumor cells and reverse LOX-inhibitor-induced growth inhibition, suggesting the specific role of LOX in regulating pancreatic cancer cell proliferation. Although questions still need to be answered, such as the underlying mechanisms for COX and LOX-induced growth inhibition, both COX and LOX pathways are potential targets for pancreatic cancer treatment and chemoprevention. COX and LOX enzyme inhibitors are available and have been shown to be relatively safe in the treatment of other diseases.