Leukotriene B4 receptor 2 (BLT2), a member of G-protein-coupled receptor (GPCR) family, plays a critical role in the pathogenesis of several diseases, including airway inflammation and cancer. Despite the importance of single-nucleotide polymorphism (SNP) of GPCR in physiopathology, no studies on BLT2 SNP effects have been reported to date. In my study, I demonstrate that the BLT2 SNP (rs1950504, Asp196Gly), a Gly-196 variant of BLT2 (BLT2 D196G), causes enhanced cell motility under low-dose stimulation of its ligands. I demonstrated that Akt activation and subsequent production of reactive oxygen species (ROS), and the ligand binding affinity are increased by BLT2 D196G in response to low-dose ligand stimulation. Through homology modeling analysis, it was predicted that BLT2 D196G loses ionic interaction with R197, potentially resulting in increased ligand-receptor interaction. To the best of my knowledge, this report is the first to describe a SNP study on BLT2 and shows that BLT2 D196G enhances ligand sensitivity, thereby increasing cell motility in response to low-dose ligand stimulation.
Next, I explored the role of BLT2 in human airway inflammatory diseases, especially lung cancer. Lung cancer is the leading cause of cancer deaths worldwide and KRAS is the most frequently mutated oncogene among lung cancer cases, the signaling mechanism responsible for KRAS-driven lung cancer is still incompletely elucidated. Here, I observed that the expression levels of BLT2 and its ligand-producing enzymes (5-LOX, 12-LOX) were highly increased by mutant KRAS and that BLT2 blockade attenuated cell proliferation and interleukin-6 production. I demonstrate that blockade of BLT2 effectively attenuate the lung cancer progression both in transgenic mice with lung-specific expression of mutant KRAS (KrasG12D), and KrasG12D/BLT2 knock-out double-mutant mouse model. Additionally, I observed high BLT2 expression in patient-derived tissue samples of KrasG12D-expressing lung adenocarcinoma, supporting the role of BLT2 in KRAS-driven human lung cancer. Collectively, my study is the first to describe the role of BLT2 as a potential contributor to KRAS-driven lung cancer.
Lastly, I examined weather the BLT2 related to metastasis in human lung cancer cells. I found that expression of BLT2 was significantly elevated in primary tumor of lung cancer patients, by analysis of TCGA Lung Cancer database. I observed that the motility and the invasive potential of human lung cancer cell lines (A549, SK-LU-1) were significantly dependent on BLT2. Moreover, the BLT2-mediated migration and invasion in human lung cancer cells were mediated through the stimulation of epithelial-mesenchymal transition (EMT). To my knowledge, this is the first report describing the role of BLT2 in lung cancer migration and invasion, and these results may contribute to the identification of an attractive therapeutic target for lung cancer.