Tyrosine kinase receptor RON in human pancreatic cancer: expression, function, and validation as a target.
BACKGROUND
Specific tyrosine kinase receptors such as c-MET mediate epithelial-mesenchymal (EMT) transition, leading to phenotypic alterations associated with increased cell motility. It was hypothesized that RON, a tyrosine kinase receptor related to c-MET, would be expressed in human pancreatic cancer cells, induce EMT, and would thus serve as a target for therapy in a preclinical model.


METHODS
RON expression in human pancreatic cancer specimens was assessed by immunohistochemistry. In pancreatic cancer cell lines, RON expression was assessed by reverse-transcriptase polymerase chain reaction (PCR) and Western blot analysis. The human pancreatic cancer cell line L3.6pl, with high RON expression, was exposed to macrophage stimulating protein (MSP), the RON ligand, and assessed for cell migration, invasion, and changes associated with EMT. Western blot analysis and immunofluorescent staining were used to assess alterations in protein expression and cellular location, respectively. A RON monoclonal antibody (MoAb) was used to block ligand-induced activation of RON.


RESULTS
Immunohistochemical staining revealed RON overexpression in 93% of human pancreatic cancer specimens relative to nonmalignant ductal tissue. RON mRNA and protein was expressed in 9 of 9 human pancreatic cancer cell lines. Treatment of L3.6pl cells with MSP increased Erk phosphorylation, cell migration, and invasion (P < .001). RON activation led to a decrease in membrane-bound E-cadherin in association with nuclear translocation of beta-catenin. RON MoAb inhibited downstream signaling as well as cell migration and invasion. In nude mice, RON MoAb inhibited subcutaneous and orthotopic tumor growth by about 60%.


CONCLUSIONS
RON activation induced molecular and cellular alterations consistent with EMT. Inhibition of RON activation inhibited tumor growth in vivo. Novel antineoplastic therapies designed to inhibit RON activity may hinder mechanisms critical for pancreatic tumor progression.
Camp
E Ramsay
ER
Department of Surgical Oncology, University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA.
Yang
Anthony
A
Gray
Mike J
MJ
Fan
Fan
F
Hamilton
Stanley R
SR
Evans
Douglas B
DB
Hooper
Andrea T
AT
Pereira
Daniel S
DS
Hicklin
Daniel J
DJ
Ellis
Lee M
LM
D021581:Active Transport, Cell Nucleus; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D004848:Epithelium / Q000473:pathology; D006801:Humans; D008648:Mesoderm / Q000473:pathology; D009361:Neoplasm Invasiveness; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology*; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D015820:Cadherins; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases