No abstract

Background: The analysis of angiogenesis factors in the blood of tumor patients has given diverse results on their prognostic or predictive value. Since mediators of angiogenesis are stored in platelets, their measurement in plasma is sensitive to inadvertent platelet activation during blood processing. Methods: Variants of blood withdrawal and plasma preparation were evaluated by ELISA for the detection of TSP-1, PF-4, VEGF and PD-ECGF. A total of 22 pancreatic cancer patients and 29 healthy volunteers were evaluated. Results: Plasma preparation with the anticoagulant mix of citrate, theophylline, adenosine, dipyridamole (CTAD) and immediate blood processing at 4°C was required for reproducible measurements of TSP-1, PF-4 and VEGF. Blood collection by venflon or inadvertent hemolysis during blood withdrawal caused significantly elevated TSP-1 and PF4 values. When optimized plasma preparation was applied, a significant increase of TSP-1 and VEGF in cancer patients was detected (P = 0.006; P < 0.001). Conclusion: The reliable plasma analysis of circulating platelet-stored angiogenesis factors requires preparation with CTAD at 4°C and blood collection by butterfly needle. Suboptimal procedures of plasma preparation are commonly applied in clinical monitoring of angiogenesis parameters which may account for the differences in reported plasma values and may have masked their predictive or prognostic marker potential.

Summary.  Background:  Measuring platelet activation in patients has become a potent method to investigate pathophysiological processes. However, the commonly applied markers are sensitive to detrimental influences by in vitro platelet activation during blood analysis. Objectives:  Protein isoforms of platelet‐derived thrombospondin‐1 (TSP‐1) were investigated for their potential to identify in vitro platelet activation when monitoring in vivo processes. Methods:  TSP‐1 was determined in plasma, serum or supernatant of purified platelets by ELISA and immunoblotting and was compared with standard markers of platelet activation. A collective of 20 healthy individuals and 30 cancer patients was analyzed. Results:  While in vitro platelet degranulation led to a selective increase in the 200‐kDa full‐length molecule, an in vivo process involving platelet activation such as wound healing resulted in the predominant rise of the 140‐kDa TSP‐1 protein. The physiological ratio of circulating TSP‐1 variants was determined and a cut‐off level at 1.0 was defined to identify plasma samples with artificial in vitro platelet activation exceeding the cut‐off level. In contrast, cancer patients known to frequently exhibit increased in vivo activation of platelets presented with a significantly decreased ratio of TSP‐1 variants as compared with healthy volunteers. Conclusions:  In comparison to standard platelet markers, TSP‐1 constitutes a sensitive and stable parameter suited to monitor in vitro platelet activation. The analysis of TSP‐1 protein isoforms further offers a valuable tool to reliably discriminate between in vitro and in vivo effects, to exclude variability introduced during blood processing and improve clinical monitoring.

NeoGemTax was safe and resection was feasible in a number of patients after systemic neoadjuvant treatment. Further randomized clinical trials are needed to identify novel multimodal regimens that would be able to increase the percentage of patients undergoing curative pancreatic cancer surgery despite advanced tumor stage at the time of diagnosis.