Significant overexpression of SPARC/osteonectin mRNA in pancreatic cancer compared to cancer of the papilla of Vater.

Cancer of the papilla of Vater (CPV) has a significantly better outcome compared to pancreatic cancer (PC) after curative resection. Increasing evidence suggests that prognostic differences are influenced by a different tumor biology. Secreted protein acidic and rich in cystein (SPARC)/osteonectin is a multifunctional matricellular protein involved in cell-matrix interactions and might be involved in tumor pathogenesis and progression. We examined quantitative SPARC mRNA expression in CPV and PC to evaluate if varying expression might contribute to the different biologic behaviour of these entities. Quantitative real-time reverse transcription-PCR was performed to analyze expression of SPARC mRNA in a series of 31 PC and 8 CPV specimens and corresponding uninvolved pancreatic tissues. Relative mRNA levels (ratio tumor/normal) were calculated as (SPARC/beta-actin in tumor)/(SPARC/beta-actin in paired normal tissue). SPARC expression levels were associated with clinical and histopathological parameters. SPARC mRNA expression was detected in all tumor and normal tissues of the pancreas and papilla of Vater. In pancreatic cancer, 15/31 (48.4%) patients showed overexpression of SPARC (ratio tumor/normal >1) whereas in CPV only 1/8 (12.5%) exhibited SPARC overexpression and this difference was statistically significant (p<0.05, Mann-Whitney test). No associations were detected with T- and N-categories, grading or prognosis. In conclusion, SPARC mRNA overexpression is significantly more frequent in CP than CPV and adds further evidence that CP and CPV are biologically different tumor entities.