Back to Annual Meeting Posters

Background: Alternative splicing of osteopontin (OPN) produces three splice variants: OPNa, OPNb, and OPNc. We have previously demonstrated a role for OPNc in pancreatic ductal adenocarcinoma (PDA) inflammation and proposed its potential as a novel therapeutic target to reduce PDA-associated inflammation. The aims of this study were to examine the expression pattern of OPN splice variants in sera from patients with pancreatic lesions and to determine their correlation with the presence of systemic inflammatory conditions, such as obesity and diabetes. In addition, the functional significance of the individual isoforms was evaluated.
Methods: Serum samples were obtained from 90 patients undergoing pancreatic surgery at a single institution. Patients were grouped into 8 subgroups based on the disease process and presence of obesity and/or diabetes. Sera from age-matched healthy volunteers were analyzed (n=29). Real-time polymerase chain reaction and ultraviolet light illumination of ethidium-bromide gel staining were used to examine the OPN mRNA and its individual isoforms. In vitro, wound healing, cell proliferation and soft-agar colony formation assays evaluated the functional impact of each isoform in PDA cells transfected with isoform-specific cDNA. A panel of inflammation-related genes was also analyzed.
Results: Sera were obtained from PDA patients (mean age 66 ± 1.12(SE) years; 40 male). Histopathology confirmed PDA in 58 patients, IPMN in 32. Diabetes (type 2) alone was detected in 13 PDA and 4 IPMN patients and in combination with obesity in 5 PDA and 1 IPMN patients. In PDA only, the presence of OPNb was seen in 33% of the patients' sera, OPNc in 48%, with both being present in 15%. The presence of diabetes and/or obesity was associated with complete disappearance of OPNb and only expression of OPNc (82% of PDA diabetics, 100% of obese PDA patients, and 100% of obese diabetic patients with PDA). No OPNb or c was detected in the normal sera. OPNc had a significant association with presence of systemic inflammation (OR=6.8 [1.7-65, 95%CI]; p<0.05). In vitro studies show that overexpression of OPNb and c isoforms significantly (P<0.05) and (P<0.02), respectively, increased the activity of PDA cells in soft-agar colony formation and wound healing assays compared with controls.
Conclusions: Our data show for the first time the significant association between OPN splice variant c (OPNc) and the presence of systemic inflammation in patients with obesity and/or diabetes. In vitro data suggest that increased OPNc expression in PDA cells is associated with increased migration capacity. Unraveling the functional role of OPNc in systemic inflammation is essential to understanding its significance as a marker and a therapeutic target during metastasis development in PDA.