title: A spontaneous metastasis model reveals the significance of claudin-9 overexpression in lung cancer metastasis.
abstract: Metastasis causes most cancer related mortality but the mechanisms governing metastatic dissemination are poorly defined. Metastasis involves egression of cancer cells from the primary tumors, their survival in circulation and colonization at the secondary sites. Cancer cell egression from the primary tumor is the least defined process of metastasis as experimental metastasis models directly seed cancer cells in circulation, thus bypassing this crucial step. Here, we developed a spontaneous metastasis model that retains the egression step of metastasis. By repeated in vivo passaging of the poorly metastatic Lewis lung carcinoma (3LL) cells, we generated a cell line (p-3LL) that readily metastasizes to lungs and liver from subcutaneous (s.c.) tumors. Interestingly, when injected intravenously, 3LL and p-3LL cells showed a similar frequency of metastasis. This suggests enhanced egression of p-3LL cells may underlie the enhanced metastatic spread from primary tumors. Microarray analysis of 3LL and p-3LL cells as well as the primary tumors derived from these cells revealed altered expression of several genes including significant upregulation of a tight junction protein, claudin-9. Increased expression of claudin-9 was confirmed in both p-3LL cells and tumors derived from these cells. Knockdown of claudin-9 expression in p-3LL cells by si-RNA significantly reduced their motility, invasiveness in vitro and metastasis in vivo. Conversely, transient overexpression of claudin-9 in 3LL cells enhanced their motility. These results suggest an essential role for claudin-9 in promoting lung cancer metastasis.
authors.affiliation: James Graham Brown Cancer Center, University of Louisville, Louisville, KY, 40202, USA. rkshar01@louisville.edu.|Department of Medicine, University of Louisville, Louisville, KY, 40202, USA. rkshar01@louisville.edu.|Department of Microbiology and Immunology, University of Louisville, Louisville, KY, 40202, USA. rkshar01@louisville.edu.
authors.forename: Rajesh K
authors.initials: RK
authors.lastname: Sharma
authors.affiliation: Department of Microbiology and Immunology, University of Louisville, Louisville, KY, 40202, USA.
authors.forename: Zinal S
authors.initials: ZS
authors.lastname: Chheda
authors.affiliation: James Graham Brown Cancer Center, University of Louisville, Louisville, KY, 40202, USA.
authors.forename: Biswa Pratim
authors.initials: BP
authors.lastname: Das Purkayastha
authors.affiliation: The Hiram C. Polk Jr, MD, Department of Surgery, University of Louisville, Louisville, KY, 40202, USA.
authors.forename: Jorge G
authors.initials: JG
authors.lastname: Gomez-Gutierrez
authors.affiliation: James Graham Brown Cancer Center, University of Louisville, Louisville, KY, 40202, USA.|Department of Microbiology and Immunology, University of Louisville, Louisville, KY, 40202, USA.
authors.forename: Venkatakrishna R
authors.initials: VR
authors.lastname: Jala
authors.affiliation: James Graham Brown Cancer Center, University of Louisville, Louisville, KY, 40202, USA. h0bodd01@louisville.edu.|Department of Microbiology and Immunology, University of Louisville, Louisville, KY, 40202, USA. h0bodd01@louisville.edu.
authors.forename: Bodduluri
authors.initials: B
authors.lastname: Haribabu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018827:Carcinoma, Lewis Lung / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D057167:Claudins / Q000235:genetics / Q000378:metabolism*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D051379:Mice; D008810:Mice, Inbred C57BL; D009361:Neoplasm Invasiveness / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D059467:Transcriptome; D014162:Transfection
chemical_list: D057167:Claudins; C515808:Cldn9 protein, mouse; D034741:RNA, Small Interfering
keywords: Biomarker; Claudin-9; Lung Cancer; Metastasis; Migration