title: Phospholipase D signaling pathway is involved in lung cancer-derived IL-8 increased osteoclastogenesis.
abstract: Bone is a frequent target of lung cancer metastasis, which is associated with significant morbidity and a dismal prognosis. This study analyzed the soluble factors secreted by lung cancer cells, which are responsible for increasing osteoclast differentiation. Addition of recombinant human interleukin-8 (rhIL-8), present in large amounts in A549-conditioned medium (CM) and NCI-H460-CM, mimicked the inductive effect of A549-CM and NCI-H460-CM on osteoclastogenesis. In contrast, depletion of interleukin-8 (IL-8) from A549-CM and NCI-H460-CM decreased the osteoclastogenesis-inductive properties of A549-CM and NCI-H460-CM. Induction of osteoclast differentiation by lung cancer-derived-CM and rhIL-8 was associated with increased phospholipase D (PLD) activation, and the activations of protein kinase C (PKC) alpha/betaII, extracellular signal-regulated kinase (ERK) 1/2 and AKT/the mammalian target of rapamycin (mTOR). Blocking PLD by a specific inhibitor significantly decreased osteoclast formation by inhibiting PKCs activation and subsequently attenuating the phosphorylation of ERK1/2. PLD inhibitor also completely decreased AKT and mTOR phosphorylation, whereas phosphatidylinositol-3-kinase (PI3K) inhibitor only partially decreased mTOR phosphorylation, suggesting that mTOR activation by PLD is through both PI3K/AKT-dependent and PI3K/AKT-independent manner. In addition, blocking AKT and ERK1/2 by a specific inhibitor also suppressed lung cancer-derived-CM and rhIL-8-induced osteoclast differentiation. Moreover, treatment of peripheral blood mononuclear cells with sera from invasive lung cancer patients increased the formation of osteoclasts. Our study suggests that IL-8 or IL-8-mediated PLD/PKC/ERK1/2 or PLD/AKT signaling is an attractive therapeutic target for osteolytic bone metastases in lung cancer patients.
authors.affiliation: Graduate Institute of Medicine, Schoolof Medicine, College of Medicine, Kaohsiung Medical University, 807 Kaohsiung, Taiwan.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Hsu
authors.forename: Jen-Yu
authors.initials: JY
authors.lastname: Hung
authors.forename: Ying-Chin
authors.initials: YC
authors.lastname: Ko
authors.forename: Chih-Hsing
authors.initials: CH
authors.lastname: Hung
authors.forename: Ming-Shyan
authors.initials: MS
authors.lastname: Huang
authors.forename: Po-Lin
authors.initials: PL
authors.lastname: Kuo
mesh_terms: D001859:Bone Neoplasms / Q000556:secondary; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D006801:Humans; D016209:Interleukin-8 / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D008175:Lung Neoplasms / Q000473:pathology*; D020935:MAP Kinase Signaling System; D010010:Osteoclasts / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010739:Phospholipase D / Q000502:physiology*; D051571:Protein Kinase C-alpha / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D053245:RANK Ligand / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases
chemical_list: D048049:Extracellular Signal-Regulated MAP Kinases; D016209:Interleukin-8; D047908:Intracellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D010739:Phospholipase D; D051571:Protein Kinase C-alpha; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D053245:RANK Ligand; D058570:TOR Serine-Threonine Kinases; C505688:TNFSF11 protein, human; C546842:MTOR protein, human