Lung cancer osteopontin isoforms exhibit angiogenic functional heterogeneity
Received 1 May 2009; received in revised form 24 July 2009; accepted 17 August 2009. published online 12 October 2009.
Objective
Osteopontin is a multifunctional phosphoprotein with an important but poorly understood role in non–small cell lung cancer pathogenesis. We hypothesize that osteopontin isoforms (OPNa, OPNb, and OPNc) have divergent roles in non–small-cell lung cancer angiogenesis and divergent impact on vascular endothelial growth factor secretion.
Methods
We examined mRNA expression using reverse transcriptase-polymerase chain reaction primers for 3 osteopontin isoforms in non–small-cell lung cancer and immortalized bronchial epithelial cell lines, and correlated expression with osteopontin secretion into media detected by enzyme-linked immunosorbent assay. Angiogenic properties conferred by osteopontin isoforms were evaluated by transfecting cDNA plasmids specific to each isoform and controls into non–small-cell lung cancer cell lines, H153 and H358 (low endogenous osteopontin) and A549 and H460 (high endogenous osteopontin), analyzing conditioned media on a bovine capillary endothelial platform, and measuring vascular endothelial growth factor levels by enzyme-linked immunosorbent assay.
Results
OPNa mRNA expression correlated with osteopontin secretion in cell lines (r = 0.912, P = .0006). OPNa overexpression significantly increased tubule length compared with controls, OPNb had a similar, but less pronounced effect, and OPNc significantly decreased tubule length compared with controls in each cell line. OPNa overexpression was associated with significant increases in vascular endothelial growth factor secretion, whereas OPNb had no effect and OPNc overexpression was associated with significant decreases in vascular endothelial growth factor compared with controls in each cell line.
Conclusion
We demonstrated divergent effects of osteopontin isoforms on non–small-cell lung cancer angiogenesis and vascular endothelial growth factor secretion. OPNa overexpression was associated with increased bovine capillary endothelial tubule length and vascular endothelial growth factor secretion, whereas OPNc was associated with decreases in both. These findings may lead to therapeutic strategies for selective isoform inhibition in non–small cell lung cancer.
Department of Cardiothoracic Surgery, New York University School of Medicine, New York, NY
Address for reprints: Jessica S. Donington, MD, New York University Medical Center, Department of Cardiothoracic Surgery, 530 First Avenue, Suite 9V, New York, NY 10016.
Funded in part by U01 CA111295-03, Early Detection Research Network, National Cancer Institute, National Institutes of Health, and Belluck and Fox, LLP, New York, New York.
Disclosures: Harvey I. Pass reports advisory fees and grant support from Rosetta Genomics and a patent pending on osteopontin.
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