Prevalence of 5-lipoxygenase expression in canine osteosarcoma and the effects of a dual 5-lipoxygenase/cyclooxygenase inhibitor on osteosarcoma cells in vitro and in vivo

Comparative Cancer Cell Signaling in Muscle-Invasive Urothelial Carcinoma of the Bladder in Dogs and Humans

Muscle-invasive urothelial carcinoma (MIUC) is the most common type of bladder malignancy in humans, but also in dogs that represent a naturally occurring model for this disease. Dogs are immunocompetent animals that share risk factors, pathophysiological features, clinical signs and response to chemotherapeutics with human cancer patients. This review summarizes the fundamental pathways for canine MIUC initiation, progression, and metastasis, emerging therapeutic targets and mechanisms of drug resistance, and proposes new opportunities for potential prognostic and diagnostic biomarkers and therapeutics. Identifying similarities and differences between cancer signaling in dogs and humans is of utmost importance for the efficient translation of in vitro research to successful clinical trials for both species.

Lipoxygenase-5 Expression in Canine Urinary Bladder: Normal Urothelium, Cystitis and Transitional Cell Carcinoma

Transitional cell carcinoma (TCC) is the most common canine urinary tract tumour and mimics human invasive TCC. Human TCCs overexpress lipoxygenase (LOX)-5 and the use of target inhibitors has proven effective in inhibiting neoplastic growth. In this study, we investigated the immunohistochemical expression of LOX-5 in normal canine urinary bladder, cystitis and TCC. The comparative expression of LOX-5, cyclo-oxygenase (COX)-1 and COX-2 among the three tissue groups was also examined. Biopsy samples from cases of cystitis and TCC were reviewed from 2012 to 2016; samples of histologically normal bladder were used as controls. Dogs were excluded if they had received glucocorticoids, non-steroidal anti-inflammatory drugs (NSAIDs) and/or chemotherapy prior to tissue collection. LOX-5 was expressed in 95% of TCCs, 23% of cases of cystitis and 10% of controls. LOX-5 and COX-2 immunohistochemistry scores were significantly (P <0.01) higher in TCCs versus cystitis and normal bladders. Results of this study support the rationale for further investigation of the use of NSAIDs with dual anti COX-2 and LOX-5 effect for the treatment of canine TCC.

Antitumor mechanisms of cyclooxygenase and lipoxygenase

Eicosanoids, as the metabolic product of arachidonic acid, play an important role in tumor development and metastasis. Cyclooxygenase (COX)-2 and lipoxygenase (LOX) are two key enzymes that mediate the metabolism of arachidonic acid. So far, great progress has been made on the research of COX-2 and prostaglandins, and it has been demonstrated that they can induce the imbalance between cell growth and apoptosis as well as tumor angiogenesis. LOX and its metabolites, such as hydroxyeicosatetraenoic acid (HETE) and leukotriene (LT), have received more and more attention for their role in tumor development. Research has proved that LT-B4 and 5-HETE participate in the occurrence and development of multiple tumors. Therefore, COX and LOX dual inhibitors prove a new approach to anti-tumor therapy.

Methyl jasmonate: putative mechanisms of action on cancer cells cycle, metabolism, and apoptosis

Methyl jasmonate (MJ), an oxylipid that induces defense-related mechanisms in plants, has been shown to be active against cancer cells both in vitro and in vivo, without affecting normal cells. Here we review most of the described MJ activities in an attempt to get an integrated view and better understanding of its multifaceted modes of action. MJ (1) arrests cell cycle, inhibiting cell growth and proliferation, (2) causes cell death through the intrinsic/extrinsic proapoptotic, p53-independent apoptotic, and nonapoptotic (necrosis) pathways, (3) detaches hexokinase from the voltage-dependent anion channel, dissociating glycolytic and mitochondrial functions, decreasing the mitochondrial membrane potential, favoring cytochrome c release and ATP depletion, activating pro-apoptotic, and inactivating antiapoptotic proteins, (4) induces reactive oxygen species mediated responses, (5) stimulates MAPK-stress signaling and redifferentiation in leukemia cells, (6) inhibits overexpressed proinflammatory enzymes in cancer cells such as aldo-keto reductase 1 and 5-lipoxygenase, and (7) inhibits cell migration and shows antiangiogenic and antimetastatic activities. Finally, MJ may act as a chemosensitizer to some chemotherapics helping to overcome drug resistant. The complete lack of toxicity to normal cells and the rapidity by which MJ causes damage to cancer cells turn MJ into a promising anticancer agent that can be used alone or in combination with other agents.