title: MMP-9 from sublethally irradiated tumor promotes Lewis lung carcinoma cell invasiveness and pulmonary metastasis.
abstract: Matrix metalloproteinases (MMPs) associate with tumor progression and metastasis. We sought to investigate the role of MMP-9 from sublethally irradiated tumor in accelerated pulmonary metastasis of Lewis lung carcinoma (LLC-LM) and the corresponding anti-metastasis strategies in C57BL/6 mice. We used Matrigel-coated Boyden chamber assays and chicken chorioallantoic membrane assays to evaluate the invasion capability of irradiated LLC-LM cells (7.5 Gy), reverse transcription-polymerase chain reaction and the western blot assay to investigate the expression of MMPs by irradiated cells, and small interfering RNA duplexes to inhibit MMP-9 expression. LLC-LM cells differing in MMP-2 or -9 expression were subcutaneously injected into right thighs and the resulting tumors were irradiated (10 Gy × 5) to induce pulmonary metastasis. Radiation significantly enhanced MMP-9 at both the transcriptional and translational levels. MMP-9 siRNA significantly inhibited in vitro radiation-enhanced invasiveness. The number of radiation-accelerated pulmonary metastases was significantly reduced by MMP-9 knockdown and MMP-2/9 knockdown. Reverse transcription-polymerase chain reaction of LLC-LM cells in the blood and lung tissue revealed MMP-9 involvement in radiation-enhanced intravasation. Either higher-dose irradiation (30 Gy × 2) or pretreatment with prototypical MMP-9 inhibitor, zoledronic acid, significantly reduced the number of pulmonary metastases. The viability of irradiated tumor was seen on both positron emission tomography and magnetic resonance imaging, and tumor/serum MMP-9 levels suggested the association of local control of primary tumor and inhibition of time-dependent MMP-9 activities. Our results demonstrate that MMP-9 is crucially involved in radiation-enhanced LLC-LM cell invasiveness in vitro and in pulmonary metastasis from inadequately irradiated primary tumor in vivo.
authors.affiliation: Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: C H
authors.initials: CH
authors.lastname: Chou
authors.forename: C-M
authors.initials: CM
authors.lastname: Teng
authors.forename: K-Y
authors.initials: KY
authors.lastname: Tzen
authors.forename: Y-C
authors.initials: YC
authors.lastname: Chang
authors.forename: J-H
authors.initials: JH
authors.lastname: Chen
authors.forename: J C-H
authors.initials: JC
authors.lastname: Cheng
mesh_terms: D000818:Animals; D018827:Carcinoma, Lewis Lung / Q000473:pathology*; D002642:Chick Embryo; D004164:Diphosphonates / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D008175:Lung Neoplasms / Q000556:secondary*; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness; D000077211:Zoledronic Acid
chemical_list: D004164:Diphosphonates; D007093:Imidazoles; D061965:Matrix Metalloproteinase Inhibitors; D000077211:Zoledronic Acid; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse