Effect of the serine proteases inhibitor gabexate mesylate (GM) on the activity of gemcitabine (G) in cell lines of pancreatic cancer (PC)

e15645 Background: Negligible advances for PC treatment have been done over the last decade and G remains the standard. Proteolitic degradation of extracellular matrix (ECM) is essential for early local invasion, metastasis and desmoplastic reaction characterizing PC. Differently from MMPs, the serine proteases (uPA and TAT) action is earlier and larger, degradating not only ECM, but also basement membrane, and activating trypsin, plasmin, angiogenesis via TGF-β1 and proliferation via PAR-2. GM is an inhibitor of u-PA,TAT, trypsin and plasmin, used in Italy and Japan for prophylaxis of acute pancreatitis after ERCP. In a previous study, GM demonstrated antinvasion and antimetastatic activity. Study aim: to evaluate if GM increases G efficacy on pancreatic cancer cell line. Methods: In vitro study of phenotypic effects of GM and G in poor differentiated PANC-1 PC cell line using:1) Cell vitality test (Trypan blu);2) Invasion test (Matrigel invasion assay);3) Cell cycle analysis (cytofluorimeter);4) Antiangiogenic test (tube formation assay in extracellular matrix using E.A.hy926 endothelial cells with matrigel). Different doses of G and GM (100,200,250,500 μM;1mM) alone or combined (concomitant or sequential) have been tested vs controls (PANC-1 without any treatment). All tests have been done in triplicate. Results: G alone (250 μM) decreases invasion by 40% (±5,6%) and cell vitality by 15% (±1,3%.). GM alone (100 μM) decreases invasion by 30% (±4,6%.) but 1mM is needed for similar vitality decrease. GM+G together are detrimental vs G alone while sequential treatment (GM before G with or without 24 hours of interval) enhances G activity. GM (200 μM) and G (250 μM) in immediate sequence show better results decreasing ability of invasion by 75% (±8,3%). Cell vitality is better inhibited from GM (100)/G (250) 24 h-delayed sequence by 28% (±3,8%). Combined treatment mainly blocks cells in G1 phase of cell cycle (5%±0,5%) vs controls. Concerning antiangiogenic assay, the administration of G alone is ineffective to inhibit angiogenesis, while pre-treatment with GM results in a strong anti-angiogenic effect. Conclusions: Association of GM to G could represent a new effective approach to inhibit invasion, angiogenesis and growth in pancreatic cancer. No significant financial relationships to disclose.