Life under aerobic conditions has shaped peroxiredoxins (Prx) as ubiquitous thiol-dependent hydroperoxidases and redox sensors. Structural features that balance the catalytically active or inactive redox states of Prx, and, therefore, their hydroperoxidase or sensor function, have so far been analyzed predominantly for Prx1-type enzymes. Here we identify and characterize two modulatory residues of the Prx5-type model enzyme PfAOP from the malaria parasite Plasmodium falciparum. Gain- and loss-of-function mutants reveal a correlation between the enzyme parameters and the inactivation susceptibility of PfAOP with the size of residue 109 and the presence or absence of a catalytically relevant but nonessential cysteine residue. Based on our kinetic data and the crystal structure of PfAOP(L109M), we suggest a novel mechanism for balancing the hydroperoxidase activity and inactivation susceptibility of Prx5-type enzymes. Our study provides unexpected insights into Prx structure-function relationships and contributes to our understanding of what makes Prx good enzymes or redox sensors.

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LBA4505 Background: Adjuvant 5-FU/FA (ESPAC-1 trial) and GEM (CONKO-001 trial) provide improved survival for patients with resected pancreatic cancer compared to no chemotherapy. The aim of the ESPAC-3 (v2) trial was to compare 5FU/FA vs GEM to identify if either adjuvant chemotherapy was associated with a significantly better survival. Methods: Patients with an R0/R1 resection for pancreatic ductal adenocarcinoma were randomized (stratified for resection margin status and country) <8 weeks of surgery to receive either 5FU/FA (FA, 20 mg/m2, iv bolus injection followed by 5-FU, 425 mg/m2, iv bolus injection given 1–5d every 28 days) or GEM (1,000mg/m2 iv infusion 1d, 8d and 15d every 4 weeks) for 6 months. The primary outcome measure was overall survival; the secondary measures were toxicity, progression free survival and quality of life. 1,030 patients were needed to detect a 10% difference in 2-year survival rates with 90% power. Results: 1,088 patients from 16 countries were randomized from July 2000 to Jan 2007 (5FU/FA = 551, GEM = 537). Median (range) age was 63 (31–85) years; 598 (55%) were men. Median tumor size was 30 (20–350) mm; 384 (35%) were R1 resections; 777 (72%) were node positive; and 263 (25%) were poorly differentiated tumors. Final analysis was carried out on an intention to treat basis with a minimum of 2 years follow-up after 753 (69%) patients had died. Median (IQR) follow-up of 335 alive patients was 34.2 (27.1–43.4) months, equal across treatment groups. Median survival from resection of patients treated with 5FU/FA was 23.0 (95% CI: 21.1, 25.0) months and for patients treated with GEM this was 23.6 (95%CI: 21.4, 26.4) months. Log-rank analysis revealed no statistically significant difference in survival estimates between the treatment groups (c2LR=0.7, p=0.39, HRGEM=0.94 (95%CI: 0.81, 1.08)). There was no significant difference in the effect of treatment across subgroups according to R status (test of heterogeneity c21=0.3, p=0.56). Conclusions: This is the largest adjuvant trial ever conducted for pancreatic ductal adenocarcinoma and showed no significant difference in survival between adjuvant 5FU/FA and adjuvant GEM. [Table: see text]

Abstract. Pancreatic carcinoma is a very aggressive disease and little is known about its immunobiology. We here describe the presence in pancreatic cancer patients of spontaneously induced functional CD4 and CD8 memory/effector T cells reactive to autologous tumor cells or to the pancreatic cancer associated antigen, MUC-1. Such specific cells were present in the bone marrow or peripheral blood of most of the 23 tested patients. Low dose stimulation of primary cultures of pancreatic cancer cells with 500 IU/ml IFN-Á for 72 h enhanced HLA-I expression and induced the de novo expression of HLA-II molecules. This led to a much better immune recognition by autologous HLA-I restricted and purified CD8 T cells and allowed tumor cell recognition by HLA-II restricted purified CD4 T-helper cells. Thus, interferon-Á appears to be a useful adjuvant cytokine to enhance the immunogenicity of a patients' tumor cells and their recognition by tumor reactive immune cells.