Conclusion Twenty compounds with dinitrobenzoate scaffold

Conclusion Twenty compounds with 3,5-dinitrobenzoate scaffold were synthesized and evaluated using cell-free and HWB assays for their 5-LOX inhibition activities. Compared to the parent compound, six compounds show significantly increased enzyme inhibition activities. The best compound, 3-tolyl 3,5-dinitrobenzoate (3a), showed high potency in cell free assay (IC50=6nM) and in human whole blood assay (IC50=0.5μM). SAR studies gave insights to the design of better 5-LOX inhibitors.
Experiments
Acknowledgments
Introduction Pancreatic ductal adenocarcinoma (PDAC), the fourth leading cause of cancer-related deaths in the United States, is associated with a pronounced fibroinflammatory response, which can contribute to cancer progression at all stages of tumor development [1], [2]. This is further supported by the fact that chronic pancreatitis is associated with an increased risk of developing PDAC [3]. Obesity, which is also associated with an increased risk of developing PDAC, has been identified as a chronic inflammatory state [4]. It is possible that chronic inflammation associated with obesity may be driven by diets that are rich in fat [5]. Omega-6 fatty acids (FAs) provide substrate for the production of inflammatory eicosanoids by the enzymes lipoxygenase and cyclooxygenase [6]. Obese patients have been found to have higher levels of serum FAs as well as serum and urinary leukotrienes [7]. Although cyclooxygenases have been extensively studied [8], [9], the role of lipoxygenases in PDAC remains relatively undefined. 5-lipoxygenase (5LO) is upregulated in multiple cancer types, including human PDAC tumors, and leukotriene B4 (LTB4) receptors (primarily BLT4) are also upregulated in pancreatic cancer [10]. 5LO can metabolize arachidonic acid, generated from omega-6 FAs, to produce the leukotriene LTB4, which is a known chemotactic factor for inflammatory prolyl hydroxylase such as mast cell and neutrophils [11], [12], [13], [14]. Notably, we have previously shown that mast cells are increased in human PDAC tumors compared with adjacent normal tissue, and can also contribute to tumor development [15]. We have also shown that diets rich in omega-6 FAs increase pancreatic lesions and mast cell infiltration in EL-Kras transgenic mice [16]. In this study we evaluated the role of 5LO in mediating lesion development and mast cell infiltration in EL-Kras mice. Initially, we showed that human pancreatic ductal epithelial (HPDE and HPDE-Kras) and cancer (AsPC1 and Panc1) cells treated with omega-6 FAs generate increased LTB4 levels in vitro. We next showed that EL-Kras mice lacking 5LO (EL-Kras/5LO) developed fewer pancreatic lesions and had decreased mast cell infiltration when compared with EL-Kras/5LO mice. Additionally, we showed that human PDAC tumors with increased 5LO expression demonstrated increased mast cell infiltration. Importantly, diets rich in omega-6 FAs failed to increase pancreatic lesion development and mast cell infiltration in EL-Kras/5LO mice. Thus, our findings indicate that 5LO functions downstream of Kras to mediate inflammation and suggest that 5LO may be a potential chemopreventive and therapeutic target in pancreatic cancer.
Materials and methods
Results
Discussion Epidemiologic studies have shown that diets rich in omega-6 FAs are associated with increased rates of breast, prostate, and pancreas cancers [21], [22], [23]. This may be likely mediated in part by an increased inflammatory response induced by conversion of omega-6 FAs to proinflammatory metabolites through 5LO and cyclooxygenase-2. Significantly, 5LO expression is increased in pancreatic cancer cells, and inhibition of 5LO can abolish proliferation of human pancreatic cancer cells [14], [24]. Importantly, LTB4, the downstream metabolite catalyzed by 5LO, has been found to be upregulated in pancreatic tumors compared with normal tissue [12]. In this report, we show that diets rich in omega-6 FAs increase LTB4 production in HPDE cells and pancreatic cancer cells. Furthermore, we show that EL-Kras/5LO mice develop fewer pancreatic lesions and are resistant to the effects of diets rich in omega-6 FA.