Effect of LY293111 in combination with gemcitabine in colonic cancer

Leukotrienes promote stem cell self-renewal and chemoresistance in acute myeloid leukemia

Acute myeloid leukemia (AML) is characterized by poor clinical outcomes due to high rates of relapse following standard-of-care induction chemotherapy. While many pathogenic drivers have been described in AML, our understanding of the molecular mechanisms mediating chemotherapy resistance remains poor. Therefore, we sought to identify resistance genes to induction therapy in AML and elucidated ALOX5 as a novel mediator of resistance to anthracycline-based therapy. ALOX5 is transcriptionally upregulated in AML patient blasts in comparison to normal hematopoietic stem/progenitor cells (HSPCs) and ALOX5 mRNA, and protein expression is increased in response to induction therapy. In vitro, and in vivo genetic, and pharmacologic perturbation studies confirm that ALOX5 positively regulates the leukemogenic potential of AML LSCs, and its loss does not significantly affect the function of normal HSPCs. ALOX5 mediates resistance to daunorubicin (DNR) and promotes AML cell survival and maintenance through its leukotriene (LT) synthetic capacity, specifically via modulating the synthesis of LTB4 and its binding to LTB receptor (BLTR). Our study reveals a previously unrecognized role of LTs in AML pathogenesis and chemoresistance, whereby inhibition of ALOX5 mediated LTB4 synthesis and function could be combined with standard chemotherapy, to enhance the overall therapeutic efficacy in AML.

Targeting Leukotrienes as a Therapeutic Strategy to Prevent Comorbidities Associated with Metabolic Stress

Leukotrienes (LTs) are potent lipid mediators that exert a variety of functions, ranging from maintaining the tone of the homeostatic immune response to exerting potent proinflammatory effects. Therefore, LTs are essential elements in the development and maintenance of different chronic diseases, such as asthma, arthritis, and atherosclerosis. Due to the pleiotropic effects of LTs in the pathogenesis of inflammatory diseases, studies are needed to discover potent and specific LT synthesis inhibitors and LT receptor antagonists. Even though most clinical trials using LT inhibitors or antagonists have failed due to low efficacy and/or toxicity, new drug development strategies are driving the discovery for LT inhibitors to prevent inflammatory diseases. A newly important detrimental role for LTs in comorbidities associated with metabolic stress has emerged in the last few years and managing LT production and/or actions could represent an exciting new strategy to prevent or treat inflammatory diseases associated with metabolic disorders. This review is intended to shed light on the synthesis and actions of leukotrienes, the most common drugs used in clinical trials, and discuss the therapeutic potential of preventing LT function in obesity, diabetes, and hyperlipidemia.

Frondanol, a Nutraceutical Extract from Cucumaria frondosa, Attenuates Colonic Inflammation in a DSS-Induced Colitis Model in Mice

Frondanol is a nutraceutical lipid extract of the intestine of the edible Atlantic sea cucumber, Cucumaria frondosa, with potent anti-inflammatory effects. In the current study, we investigated Frondanol as a putative anti-inflammatory compound in an experimental model of colonic inflammation. C57BL/6J male black mice (C57BL/6J) were given 3% dextran sodium sulfate (DSS) in drinking water for 7 days to induce colitis. The colitis group received oral Frondanol (100 mg/kg body weight/per day by gavage) and were compared with a control group and the DSS group. Disease activity index (DAI) and colon histology were scored for macroscopic and microscopic changes. Colonic tissue length, myeloperoxidase (MPO) concentration, neutrophil and macrophage marker mRNA, pro-inflammatory cytokine proteins, and their respective mRNAs were measured using ELISA and real-time RT-PCR. The tissue content of leukotriene B4 (LTB4) was also measured using ELISA. Frondanol significantly decreased the DAI and reduced the inflammation-associated changes in colon length as well as macroscopic and microscopic architecture of the colon. Changes in tissue MPO concentrations, neutrophil and macrophage mRNA expression (F4/80 and MIP-2), and pro-inflammatory cytokine content (IL-1β, IL-6 and TNF-α) both at the protein and mRNA level were significantly reduced by Frondanol. The increase in content of the pro-inflammatory mediator leukotriene B4 (LTB4) induced by DSS was also significantly inhibited by Frondanol. It was thus found that Frondanol supplementation attenuates colon inflammation through its potent anti-inflammatory activity.

Cysteinyl leukotrienes and their receptors: Bridging inflammation and colorectal cancer

Long-standing inflammation has emerged as a hallmark of neoplastic transformation of epithelial cells and may be a limiting factor of successful conventional tumor therapies. A complex milieu composed of distinct stromal and immune cells, soluble factors and inflammatory mediators plays a crucial role in supporting and promoting various types of cancers. An augmented inflammatory response can predispose a patient to colorectal cancer (CRC). Common risk factors associated with CRC development include diet and lifestyle, altered intestinal microbiota and commensals, and chronic inflammatory bowel diseases. Cysteinyl leukotrienes are potent inflammatory metabolites synthesized from arachidonic acid and have a broad range of functions involved in the etiology of various pathologies. This review discusses the important role of cysteinyl leukotriene signaling in linking inflammation and CRC.

Eicosanoid signalling pathways in the development and progression of colorectal cancer: novel approaches for prevention/intervention

Arachidonic acid metabolism through cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P-450 epoxygenase (EPOX) pathways leads to the generation of biologically active eicosanoids, including prostanoids, leukotrienes, hydroxyeicosatetraenoic acid, epoxyeicosatrienoic acid and hydroperoxyeicosatetraenoic acids. Eicosanoid expression levels vary during tumor development and progression of a range of malignancies, including colorectal cancer. The actions of these autocoids are also directly influenced by diet, as demonstrated by recent evidence for omega-3 fatty acids in colorectal cancer (CRC) prevention and/or treatment. Eicosanoids regulate CRC development and progression, while inhibition of these pathways has generally been shown to inhibit tumor growth/progression. A progressive sequence of colorectal cancer development has been identified, ranging from normal colon, to colitis, dysplasia, and carcinoma. While both COX and LOX inhibition are both promising candidates for colorectal cancer prevention and/or treatment, there is an urgent need to understand the mechanisms through which these signalling pathways mediate their effects on tumorigenesis. This will allow identification of safer, more effective strategies for colorectal cancer prevention and/or treatment. In particular, binding to/signalling through prostanoid receptors have recently been the subject of considerable interest in this area. In this review, we discuss the role of the eicosanoid signalling pathways in the development and progression of colorectal cancer. We discuss the effects of the eicosanoids on tumor cell proliferation, their roles in cell death induction, effects on angiogenesis, migration, invasion and their regulation of the immune response. Signal transduction pathways involved in these processes are also discussed. Finally, novel approaches targeting these arachidonic acid-derived eicosanoids (using pharmacological or natural agents) for chemoprevention and/or treatment of colorectal cancer are outlined.

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.

Up-regulation of BLT2 is critical for the survival of bladder cancer cells

The incidence rates of urinary bladder cancer continue to rise yearly, and thus new therapeutic approaches and early diagnostic markers for bladder cancer are urgently needed. Thus, identifying the key mediators and molecular mechanisms responsible for the survival of bladder cancer has valuable implications for the development of therapy. In this study, the role of BLT2, a receptor for leukotriene B((4)) (LTB((4))) and 12(S)-hydroxyeicosatetraenoic acid (HETE), in the survival of bladder cancer 253J-BV cells was investigated. We found that the expression of BLT2 is highly elevated in bladder cancer cells. Also, we observed that blockade of BLT2 with an antagonist or BLT2 siRNA resulted in cell cycle arrest and apoptotic cell death, suggesting a role of BLT2 in the survival of human bladder cancer 253J-BV cells. Further experiments aimed at elucidating the mechanism by which BLT2 mediates survival revealed that enhanced level of reactive oxygen species (ROS) are generated via a BLT2-dependent up-regulation of NADPH oxidase members NOX1 and NOX4. Additionally, we observed that inhibition of ROS generation by either NOX1/4 siRNAs or treatment with an ROS-scavenging agent results in apoptotic cell death in 253J-BV bladder cancer cells. These results demonstrated that a 'BLT2-NOX1/4-ROS' cascade plays a role in the survival of this aggressive bladder cancer cells, thus pointing to BLT2 as a potential target for anti-bladder cancer therapy.

Randomized double-blind phase II trial comparing gemcitabine plus LY293111 versus gemcitabine plus placebo in advanced adenocarcinoma of the pancreas

BACKGROUND

LY293111 (LY) is a novel oral anticancer agent with leukotriene B4 receptor antagonist and peroxisome proliferator-activated receptor gamma agonist properties, producing promising results alone and in combination with gemcitabine in pancreatic cancer xenograft models. A phase I study proved that the combination (gemcitabine plus LY) is safe and well tolerated.

PATIENTS AND METHODS

Chemotherapy-naive patients with histologically confirmed locally advanced or metastatic adenocarcinoma of the pancreas were randomly assigned to gemcitabine 1000 mg/m on days 1, 8, and 15 of a 28-day cycle and continuously administered LY 600 mg twice daily or gemcitabine 1000 mg/m on days 1, 8, and 15 of a 28-day cycle and daily oral placebo. Arms were balanced for Eastern Cooperative Oncology Group performance status and disease stage. The primary end point was 6-month survival; secondary objectives include response rate (RR), progression-free survival, and overall survival.

RESULTS

Six-month survival was not different between groups (P>0.2, 1-sided); progression-free survival and RR were not different (P>0.05, 2-sided). RR was also not impacted. LY did not increase grades 3-4 hematologic toxicities, but was associated with a trend toward more, grades 3-4 diarrhea.

CONCLUSIONS

These results do not demonstrate any benefit to adding LY to gemcitabine in unpretreated patients with advanced pancreatic carcinoma.

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.

Anti-inflammatory agents as cancer therapeutics

Cancer prevention sometimes referred to as tertiary prevention or chemoprevention makes use of specific xenobiotics or drugs to prevent, delay, or retard the development of cancer. Over the last two decades or so cancer prevention has made significant strides. For example, prevention of lung cancer through smoking cessation; cervical cancer prevention through regular Pap smear tests; colon cancer prevention through screening colonoscopy; and prostate cancer reductions by prostate-specific antigen measurements in conjunction with regular prostate examinations. The seminal epidemiological observation that nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and other cancers has provided the impetus to develop novel chemoprevention approaches against cancer. To that end, a number of "designer drugs" have been synthesized that are in different stages of development, evaluation, and deployment. Some include the cyclooxygenase-2-specific inhibitors (coxibs), nitric oxide-releasing NSAIDs (NO-NSAIDs and NONO-NSAIDs), hydrogen sulfide-releasing NSAIDs, modulators of the lipoxygenase pathway, prostanoid receptor blockers, and chemokine receptor antagonists. In addition to these novel agents, there are also a host of naturally occurring compounds/micronutrients that have chemopreventive properties. This chapter reviews these classes of compounds, their utility and mechanism(s) of action against the background of mediators that link inflammation and cancer.

Chloroquine and its analogs: a new promise of an old drug for effective and safe cancer therapies

Chloroquine (CQ), N'-(7-chloroquinolin-4-yl)-N,N-diethyl-pentane-1,4-diamine, is widely used as an effective and safe anti-malarial and anti-rheumatoid agent. CQ was discovered 1934 as "Resochin" by Andersag and co-workers at the Bayer laboratories. Ironically, CQ was initially ignored for a decade because it was considered too toxic to use in humans. CQ was "re-discovered" during World War II in the United States in the course of anti-malarial drug development. The US government-sponsored clinical trials during this period showed unequivocally that CQ has a significant therapeutic value as an anti-malarial drug. Consequently, CQ was introduced into clinical practice in 1947 for the prophylaxis treatment of malaria (Plasmodium vivax, ovale and malariae). CQ still remains the drug of choice for malaria chemotherapy because it is highly effective and well tolerated by humans. In addition, CQ is widely used as an anti-inflammatory agent for the treatment of rheumatoid arthritis, lupus erythematosus and amoebic hepatitis. More recently, CQ has been studied for its potential as an enhancing agent in cancer therapies. Accumulating lines of evidence now suggest that CQ can effectively sensitize cell-killing effects by ionizing radiation and chemotherapeutic agents in a cancer-specific manner. The lysosomotrophic property of CQ appears to be important for the increase in efficacy and specificity. Although more studies are needed, CQ may be one of the most effective and safe sensitizers for cancer therapies. Taken together, it appears that the efficacy of conventional cancer therapies can be dramatically enhanced if used in combination with CQ and its analogs.

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.

The Role of PPARgamma Receptors and Leukotriene B(4) Receptors in Mediating the Effects of LY293111 in Pancreatic Cancer

Pancreatic cancer is a devastating disease in which current therapies are inadequate. Separate lines of research have identified the 5-lipoxygenase/leukotriene B(4) receptor pathway and the PPARgamma pathway as potential targets for prevention or treatment of this disease. LY293111 was originally designed as a potent leukotriene B(4) receptor antagonist for treatment of inflammatory conditions. LY293111 was also known to have inhibitory effects on 5-lipoxygenase, which is upstream of the production of leukotrienes. LY293111 was shown to have potent anticancer effects in pancreatic cancer and several other solid malignancies, where it caused cell cycle arrest and marked apoptosis. Subsequently, it came to light that LY293111 exhibited PPARgamma agonist activity in addition to its effects on the 5-lipoxygenase pathway. This raises the question of which of the two targets is of greatest importance with regard to the anticancer effects of this agent. The evidence to date is not conclusive, but suggests that the effects of LY293111 may be mediated by both LTB(4) receptors and PPARgamma.

Expression of enzymes and receptors of the leukotriene pathway in human neuroblastoma promotes tumor survival and provides a target for therapy

The metabolism of arachidonic acid by the cyclooxygenase (COX) or lipoxygenase (LO) pathways generates eicosanoids that have been implicated in the pathogenesis of a variety of human diseases, including cancer. In this study, we examined the expression and significance of components within the 5-LO pathway in human neuroblastoma, an embryonal tumor of the sympathetic nervous system. High expression of 5-LO, 5-LO-activating protein (FLAP), leukotriene A(4) hydrolase, leukotriene C(4) synthase, and leukotriene receptors was detected in a majority of primary neuroblastoma tumors and all cell lines investigated. Expression of 5-LO and FLAP was evident in tumor cells but not in nonmalignant adrenal medulla where neuroblastomas typically arise. Moreover, neuroblastoma cells produce leukotrienes, and stimulation of neuroblastoma cells with leukotrienes increased neuroblastoma cell viability. Inhibitors of 5-LO (AA-861), FLAP (MK-886), or the leukotriene receptor antagonist montelukast inhibited neuroblastoma cell growth by induction of G(1)-cell cycle arrest and apoptosis. Similarly, specific 5-LO and leukotriene receptor silencing by small interfering RNA decreased neuroblastoma cell growth. These findings provide new insights into the pathobiology of neuroblastoma, and the use of leukotriene pathway inhibitors as a novel adjuvant therapy for children with neuroblastoma warrants further consideration.

Lipoxygenase metabolism: roles in tumor progression and survival

The metabolism of arachidonic acid through lipoxygenase pathways leads to the generation of various biologically active eicosanoids. The expression of these enzymes vary throughout the progression of various cancers, and thereby they have been shown to regulate aspects of tumor development. Substantial evidence supports a functional role for lipoxygenase-catalyzed arachidonic and linoleic acid metabolism in cancer development. Pharmacologic and natural inhibitors of lipoxygenases have been shown to suppress carcinogenesis and tumor growth in a number of experimental models. Signaling of hydro[peroxy]fatty acids following arachidonic or linoleic acid metabolism potentially effect diverse biological phenomenon regulating processes such as cell growth, cell survival, angiogenesis, cell invasion, metastatic potential and immunomodulation. However, the effects of distinct LOX isoforms differ considerably with respect to their effects on both the individual mechanisms described and the tumor being examined. 5-LOX and platelet type 12-LOX are generally considered pro-carcinogenic, with the role of 15-LOX-1 remaining controversial, while 15-LOX-2 suppresses carcinogenesis. In this review, we focus on the molecular mechanisms regulated by LOX metabolism in some of the major cancers. We discuss the effects of LOXs on tumor cell proliferation, their roles in cell cycle control and cell death induction, effects on angiogenesis, migration and the immune response, as well as the signal transduction pathways involved in these processes. Understanding the molecular mechanisms underlying the anti-tumor effect of specific, or general, LOX inhibitors may lead to the design of biologically and pharmacologically targeted therapeutic strategies inhibiting LOX isoforms and/or their biologically active metabolites, that may ultimately prove useful in the treatment of cancer, either alone or in combination with conventional therapies.

HETEs enhance IL-1-mediated COX-2 expression via augmentation of message stability in human colonic myofibroblasts

Proinflammatory cytokines and eicosanoids are central players in intestinal inflammation. IL-1, a key cytokine associated with intestinal mucosal inflammation, induces COX-2 expression in human colonic myofibroblasts (CMF) and increased prostaglandin E(2) secretion is associated with inflammatory bowel disease (IBD) and colorectal cancer (CRC). We have previously demonstrated that IL-1alpha-induced cyclooxygenase-2 (COX-2) expression is the result of NF-kappaB- and ERK-mediated transcription, as well as COX-2 message stabilization, which depends on p38, MAPKAPK-2 (MK-2) and human antigen R (HuR) RNA binding protein activation. Lipoxygenase (LOX)-derived hydroxyeicosatetraenoic acids (HETEs) are elevated in IBD and colonic adenomas and "cross talk" has been observed between the COX and LOX pathways. Since COX-2 expression is primarily in CMFs in colonic adenomas, we examined the impact of LOX metabolites, particularly HETEs, on IL-1alpha-induced COX-2 expression in human CMFs. Although 5(S)-, 12(R)-, and 15(S)-HETEs alone had little to no effect on COX-2 expression, they enhanced IL-1-mediated COX-2 expression 3.6 +/- 0.5-fold. Studies utilizing heterogeneous nuclear RNA amplification and 5,6-dichloro-beta-d-ribofuranosylbenzimidazole treatment were undertaken to measure COX-2 transcription and message stabilization, respectively. We found that HETEs enhanced IL-1-induced COX-2 mRNA levels in CMF as the result of increased p38, MK-2, and HuR activity, increasing message stability greater than that observed with IL-1 alone. Thus HETEs can act synergistically with IL-1alpha to induce COX-2 expression in human CMFs. HETEs may play a role in both colonic inflammation and in increasing the risk of CRC in IBD independently and via induction of COX-2-mediated prostaglandin secretion.

Blockade of leukotriene B4 signaling pathway induces apoptosis and suppresses cell proliferation in colon cancer

We investigated whether leukotriene B(4) (LTB(4)) and its signaling pathway play an important role in the progression of human colon cancer via a direct stimulation of cancer cell proliferation. Remarkable expression of LTB(4) receptor 1 (BLT1) in human colon cancer tissues was detected by immunohistochemistry, and Western blot analysis revealed the BLT1 expression in cultured human colon cancer cell lines, Caco2 and HT29. The 5-lipoxygenase inhibitor AA-861 and LTB(4)-receptor antagonist U75302 showed negative effects on survival and proliferation of both Caco2 and HT-29 cells. The inhibition of cell proliferation is due to the apoptosis because nuclear condensation and increased annexin V expression were observed in the cells treated with AA-861 and U75302. Knockdown of BLT1 by small interfering RNA caused the suppression of BLT1 protein, resulting in the inhibition of cancer cell proliferation. Blockade of BLT1 by the receptor antagonist significantly suppresses the LTB(4)-stimulated extracellular signal-regulated kinase (ERK) activation in colon cancer cells. These results indicate that the blockade of the LTB(4)-signaling pathway induces apoptosis via the inhibition of ERK activation in colon cancer cells. The LTB(4)-signaling pathway might be a new therapeutic target for colon cancer.

A phase I study of oral LY293111 given daily in combination with irinotecan in patients with solid tumours

BACKGROUND

LY293111 is an oral agent known to be a leukotriene B4 (LTB4) receptor antagonist and a 5-lipoxygenase inhibitor resulting in selective inhibition of the lipoxygenase pathway. Lipoxygenases metabolize arachidonic acid and have been involved in cancer cell proliferation and survival. In addition, LY293111 has been found to be a peroxisome proliferator activated receptor-gamma (PPAR-gamma) agonist. Antineoplastic activity of LY293111 has been identified in preclinical models both alone and in combination with chemotherapy agents including irinotecan. The NCIC Clinical Trials Group studied LY293111 in combination with irinotecan to determine the recommended dose of the combination and to describe its tolerability and pharmacokinetic interaction. In addition the anti-tumour activity of LY293111 in combination with irinotecan was documented.

PATIENTS AND METHODS

Twenty-eight patients with advanced solid tumours were treated on seven dose levels with the combination of irinotecan and LY293111. Irinotecan was administered intravenously every 21-days as a single dose. LY293111 was administered twice daily continuously by mouth.

RESULTS

Dose limiting toxicity (DLT) of grade 3 diarrhea was seen in two patients with doses of irinotecan 300 mg/m(2) IV every 21-days in combination with LY293111 300 mg BID. Subsequently the dose of irinotecan was decreased to 250 mg/m(2) IV every 21-days with escalating doses of LY293111. A DLT of grade 3 abdominal pain was seen at dose 600 mg BID of LY293111 with irinotecan 250 mg/m(2). The pharmacokinetics (PK) indicated that the administration of LY293111 did not have an effect on the PK of irinotecan or its metabolite SN-38. No responses were seen; seven patients had stable disease of a median duration of 4.4 months (range 2.8-13 months).

CONCLUSION

The recommended phase II dose of LY293111 is 600 mg orally BID in combination with irinotecan 250 mg/m(2) IV every 21-days. Gastrointestinal adverse effects were common but could be well managed.

Endogenous production of leukotriene D4 mediates autocrine survival and proliferation via CysLT1 receptor signalling in intestinal epithelial cells

The cysteinyl leukotriene1 (CysLT1) receptor (CysLT1R) enhances survival and proliferation of intestinal cells via distinct pathways. Here, we have demonstrated that there is significant endogenous production of CysLTs from both non-tumour- and tumour-derived intestinal epithelial cells. Treatment of two non-tumour cell lines, Int 407 and IEC-6, with CysLT1R antagonists led to shrinkage and detachment of cells, confirmed as apoptotic cell death, and a dose-dependent reduction in proliferation. However, in the tumour intestinal cell lines Caco-2, SW480, HCT-116 and HT-29, treatment with CysLT1R antagonists significantly reduced proliferation, but had no effect on apoptosis. A unique characteristic of intestinal cancer cells is the presence of nuclear CysLT1Rs, which are inaccessible to receptor antagonists. In these cells, inhibition of the endogenous production of CysLTs indirectly, by 5-lipoxygenase inhibition, impaired CysLT1R signalling throughout the cell, and resulted in apoptosis of the tumour cells. These data reveal the existence of constitutive CysLT1R signalling that mediates both survival and proliferation in intestinal cells. Importantly, we propose that tumour-derived intestinal cells are resistant to CysLT1R antagonist-induced apoptosis, a phenomena that could be explained by nuclear CysLT1R signalling.

Leukotriene B4 receptor inhibitor LY293111 induces cell cycle arrest and apoptosis in human anaplastic large-cell lymphoma cells via JNK phosphorylation

Anaplastic large-cell lymphoma (ALCL) is a heterogeneous lymphoma category in which a subset of cases carry the t(2;5)(p23;q35) or variant translocations resulting in overexpression of anaplastic lymphoma kinase (ALK). LY293111 (2-[2-propyl-3-[3-[2-ethyl-4-(4-fluorophenyl)-5-hydroxyphenoxy]-propoxy]-phenoxy] benzoic acid sodium salt) is a leukotriene B4 receptor antagonist, which was found to be safe and tolerable in Phase I clinical trials. In this study, we investigated the potential therapeutic effects and mechanisms of action of LY293111 in ALCL cell lines. LY293111 inhibited proliferation of both ALK(+) and ALK(-) ALCL cell in a dose-dependent fashion and induced complete G(1)-S cell cycle arrest, which was accompanied by upregulation of p27 and downregulation of cyclin E. Pretreatment with LY293111 for 4 h resulted in profound inhibition of serum-induced phosphorylation of extracellular-regulated kinases-1 and 2 and Akt and a concomitant increase in the phosphorylation of the stress-activated kinase c-jun N-terminal kinases (JNK). Simultaneously, LY293111 induced caspase-dependent apoptosis via activation of the intrinsic pathway, including early loss of mitochondrial inner transmembrane potential and the production of reactive oxygen species (ROS), cleavage of caspases-9, -3, poly ADP-ribose polymerase (PARP) and X-linked inhibitor of apoptosis. The phospho-JNK inhibitor SP600125 partially protected Sup-M2 cells from LY293111-induced apoptosis, PARP cleavage and ROS generation, suggesting a role for JNK in LY293111-induced cell death. These results warrant further studies of LY293111 in ALCL.

LTB4 stimulates growth of human pancreatic cancer cells via MAPK and PI-3 kinase pathways

We have previously shown the importance of LTB4 in human pancreatic cancer. LTB4 receptor antagonists block growth and induce apoptosis in pancreatic cancer cells both in vitro and in vivo. Therefore, we investigated the effect of LTB4 on proliferation of human pancreatic cancer cells and the mechanisms involved. LTB4 stimulated DNA synthesis and proliferation of both PANC-1 and AsPC-1 human pancreatic cancer cells, as measured by thymidine incorporation and cell number. LTB4 stimulated rapid and transient activation of MEK and ERK1/2 kinases. The MEK inhibitors, PD98059 and U0126, blocked LTB4-stimulated ERK1/2 activation and cell proliferation. LTB4 also stimulated phosphorylation of p38 MAPK; however, the p38 MAPK inhibitor, SB203580, failed to block LTB4-stimulated growth. The activity of JNK/SAPK was not affected by LTB4 treatment. Phosphorylation of Akt was also induced by LTB4 and this effect was blocked by the PI-3 kinase inhibitor wortmannin, which also partially blocked LTB4-stimulated cell proliferation. In conclusion, LTB4 stimulates proliferation of human pancreatic cancer cells through MEK/ERK and PI-3 kinase/Akt pathways, while p38 MPAK and JNK/SAPK are not involved.

Phase I and pharmacokinetic study of LY293111, an orally bioavailable LTB4 receptor antagonist, in patients with advanced solid tumors

PURPOSE

LY293111, a novel diaryl ether carboxylic acid derivative, is a potent and selective inhibitor of the lipoxygenase pathway either directly through 5'-lipoxygenase or via antagonism of the leukotriene B4 (LTB4) receptor. More recently it has been determined to have peroxisome proliferator activated receptor-gamma agonist (PPARgamma) activity. LY293111 has antineoplastic activity in a variety of preclinical models. The tolerability and pharmacokinetics of LY293111 administered continuously, by mouth, BID for repeat cycles of 21 days was evaluated.

PATIENTS AND METHODS

Thirty-eight patients with advanced solid tumors were treated at five dose levels (200 to 800 mg BID) for a total of 102 cycles.

RESULTS

The most common toxicity was diarrhea (76%). One patient at 600 mg BID (n = 11) and two at 800 mg BID (n = 8), experienced dose-limiting grade 3 diarrhea. Dose reductions and/or delays were infrequent. Increases in steady-state maximum plasma concentration (Cmax,ss) and area under the steady-state plasma concentration time curve 0 to 12 hours (AUCtau,ss) on day 8 could be considered to be dose-proportional over the four-fold-dose range. Interpatient variability in Cmax,ss and AUCtau,ss was estimated to be 65% and 71% respectively. There was a small increase in AUC (1.37; 90% CI, 0.85 to 2.21) between single and multiple doses. Two patients with progressive chondrosarcoma and melanoma had stable disease lasting approximately 336 and 168 days, respectively.

CONCLUSION

LY293111 can be administered safely by continuous oral therapy with mild toxicities. Diarrhea is dose-limiting. The recommended phase II dose will be 600 mg BID. The steady-state concentrations in humans exceed relevant levels observed in preclinical models.