Pancreatic ductal adenocarcinoma: biological hallmarks, current status, and future perspectives of combined modality treatment approaches.

Pancreatic ductal adenocarcinoma (PDAC) is a highly devastating disease with poor prognosis and rising incidence. Late detection and a particularly aggressive biology are the major challenges which determine therapeutic failure. In this review, we present the current status and the recent advances in PDAC treatment together with the biological and immunological hallmarks of this cancer entity. On this basis, we discuss new concepts combining distinct treatment modalities in order to improve therapeutic efficacy and clinical outcome - with a specific focus on protocols involving radio(chemo)therapeutic approaches.

Isolation, bulk cultivation, and characterization of coronary microvascular pericytes: the second most frequent myocardial cell type in vitro.

Densely arranged pericytes engird the endothelial tube of all coronary microvessels. Since the experimental access to these abundant cells in situ is difficult, a prerequisite for broader investigation is the availability of sufficient numbers of fully differentiated pericytes in homogenous culture. To reach this goal, we applied strictly standardized cell isolation techniques, optimized culture methods and specific histological staining. Approximately 1,000-fold enriched pericytes were proteolytically detached from highly purified coronary microvascular networks (density gradient centrifugation) of eight mammalian species including human. Addition of species-autologous fetal or neonatal serum (10-20% vol/vol) was a precondition for longer term survival of homogenous pericyte cultures. This ensured optimal growth (doubling time <14 h) and full expression of pericyte-specific markers. In 3-mo, 10(10) pericytes (15 g) could be cultivated from 1 bovine heart. Pericytes could be stored in liquid N(2), recultured, and passaged repeatedly without loss of typical features. In cocultures with EC or vascular smooth muscle cells, pericytes transferred fluorescent calcein to each other and to EC via their antler-like extensions, organized angiogenetic sprouting of vessels, and rapidly activated coagulation factors X and II via tissue factor and prothrombinase. The interconnected pericytes of the coronary system are functionally closely correlated with the vascular endothelium and may play key roles in the adjustment of local blood flow, the regulation of angiogenic processes, and the induction of procoagulatory processes. Their successful bulk cultivation enables direct experimental access under defined in vitro conditions and the isolation of pericyte specific antigens for the production of specific antibodies.

A critical role for granzymes in antigen cross-presentation through regulating phagocytosis of killed tumor cells.

Granzymes A and B (GrAB) are known principally for their role in mediating perforin-dependent death of virus-infected or malignant cells targeted by CTL. In this study, we show that granzymes also play a critical role as inducers of Ag cross-presentation by dendritic cells (DC). This was demonstrated by the markedly reduced priming of naive CD8(+) T cells specific for the model Ag OVA both in vitro and in vivo in response to tumor cells killed in the absence of granzymes. Reduced cross-priming was due to impairment of phagocytosis of tumor cell corpses by CD8α(+) DC but not CD8α(-) DC, demonstrating the importance of granzymes in inducing the exposure of prophagocytic "eat-me" signals on the dying target cell. Our data reveal a critical and previously unsuspected role for granzymes A and B in dictating immunogenicity by influencing the mode of tumor cell death and indicate that granzymes contribute to the efficient generation of immune effector pathways in addition to their well-known role in apoptosis induction.

Dendritic cell-based vaccination of patients with advanced pancreatic carcinoma: results of a pilot study.

BACKGROUND AND AIMS: Dendritic cell (DC)-based vaccination can induce antitumor T cell responses in vivo. This clinical pilot study examined feasibility and outcome of DC-based tumor vaccination for patients with advanced pancreatic adenocarcinoma. METHODS: Tumor lysate of patients with pancreatic carcinoma was generated by repeated freeze-thaw cycles of surgically obtained tissue specimens. Patients were eligible for DC vaccination after recurrence of pancreatic carcinoma or in a primarily palliative situation. DC were generated from peripheral blood mononuclear cells (PBMC), loaded with autologous tumor lysate, stimulated with TNF-α and PGE(2) and injected intradermally. All patients received concomitant chemotherapy with gemcitabine. Disease response was the primary endpoint. Individual immunological responses to DC vaccination were analyzed by T cell-based immunoassays using pre- and post-vaccination samples of non-adherent PBMC. RESULTS: Twelve patients received DC vaccination and concomitant chemotherapy. One patient developed a partial remission, and two patients remained in stable disease. Median survival was 10.5 months. No severe side effects were observed. Tumor-reactive T cells could be detected prior to vaccination. DC vaccination increased the frequency of tumor-reactive cells in all patients tested; however, the degree of this increase varied. To quantify the presence of tumor-reactive T cells, stimulatory indices (SI) were calculated as the ratio of proliferation-inducing capacity of lysate-loaded versus -unloaded DC. The patient with longest overall survival of 56 months had a high SI of 6.49, indicating that the presence of a pre-vaccination antitumor T cell response might be associated with prolonged survival. Five patients survived 1 year or more. CONCLUSION: DC-based vaccination can stimulate an antitumoral T cell response in patients with advanced or recurrent pancreatic carcinoma receiving concomitant gemcitabine treatment.