Induction of M2-macrophages by tumour cells and tumour growth promotion by M2-macrophages: a quid pro quo in pancreatic cancer.

INTRODUCTION: More effective therapies are required to improve survival of pancreatic cancer. Possible immunologic targets include tumour associated macrophages (TAMs), generally consisting of M1- and M2-macrophages. We have analysed the impact of TAMS on pancreatic cancer in a syngeneic orthotopic murine model. METHODS: 6606PDA murine pancreatic cancer cells were orthotopically injected into C57BL6 mice. Tumour growth was monitored using MRI. Macrophages were depleted by clodronate liposomes. Tumours including microvessel density were evaluated using immunohistochemistry, immunofluorescence and/or cytometric beads assays. Naïve macrophages were generated employing peritoneal macrophages. In vitro experiments included culturing of macrophages in tumour supernatants as well as tumour cells cultured in macrophage supernatants using arginase as well as Griess assays. RESULTS: Clodronate treatment depleted macrophages by 80% in livers (p = 0.0051) and by 60% in pancreatic tumours (p = 0.0169). MRI revealed tumour growth inhibition from 221.8 mm(3) to 92.3 mm(3) (p = 0.0216). Micro vessel densities were decreased by 44% (p = 0.0315). Yet, MCP-1-, IL-4- and IL-10-levels within pancreatic tumours were unchanged. 6606PDA culture supernatants led to a shift from naïve macrophages towards an M2-phenotype after a 36 h treatment (p < 0.0001), reducing M1-macrophages at the same time (p < 0.037). In vivo, M2-macrophages represented 85% of all TAMs (p < 0.0001). Finally, culture supernatants of M2-macrophages induced tumour growth in vitro by 63.2% (p = 0.0034). CONCLUSIONS: This quid pro quo of tumour cells and M2-macrophages could serve as a new target for future immunotherapies that interrupt tumour promoting activities of TAMs and change the iNOS-arginase balance towards their tumoricidal capacities.

A syngeneic orthotopic murine model of pancreatic adenocarcinoma in the C57/BL6 mouse using the Panc02 and 6606PDA cell lines.

BACKGROUND/AIMS: To develop a clinically relevant immunocompetent murine model to study pancreatic cancer using two different syngeneic pancreatic cancer cell lines and to assess MRI for its applicability in this model. METHODS: Two cell lines, 6606PDA and Panc02, were employed for the experiments. Cell proliferation and migration were monitored in vitro. Matrigel™ was tested for its role in tumor induction. Tumor cell growth was assessed after orthotopic injection of tumor cells into the pancreatic head of C57/BL6 mice by MRI and histology. RESULTS: Proliferation and migration of Panc02 were significantly faster than those of 6606PDA. Matrigel did not affect tumor growth/migration but prevented tumor cell spread after injection thus avoiding undesired peritoneal tumor growth. MRI could reliably monitor longitudinal tumor growth in both cell lines: Panc02 had a more irregular finger-like growth, and 6606PDA grew more spherically. Both tumors showed local invasiveness. Histologically, Panc02 showed a sarcoma-like undifferentiated growth pattern, whereas 6606PDA displayed a moderately differentiated glandular tumor growth. Panc02 mice had a significantly shorter (28 days) survival than 6606PDA mice (50 days). CONCLUSION: This model closely mimics human pancreatic cancer. MRI was invaluable for longitudinal monitoring of tumor growth thus reducing the number of mice required. Employing two different cell lines, this model can be used for various treatment and imaging studies.

Missorting of cathepsin B into the secretory compartment of CI-MPR/IGFII-deficient mice does not induce spontaneous trypsinogen activation but leads to enhanced trypsin activity during experimental pancreatitis--without affecting disease severity.

The lysosomal protease cathepsin B is thought to play a crucial role in the intracellular activation cascade of digestive proteases and in the initiation of acute pancreatitis. Although cathepsin B has been shown to be physiologically present in the secretory pathway of pancreatic acinar cells it has been suggested that premature activation of zymogens requires an additional redistribution of cathepsin B into the secretory compartment. Here, we studied the role of cathepsin B targeting during caerulein-induced pancreatitis in mouse mutants lacking the cation-independent mannose 6-phosphate/insulin-like growth factor II receptor (CI-MPR) which normally mediates the trafficking of cathepsin B to lysosomes. Absence of the CI-MPR led to redistribution of cathepsin B to the zymogen granule enriched subcellular fraction and to a substantial formation of large cytoplasmic vacuoles that contained both, trypsinogen and cathepsin B. However, this did not cause premature intracellular trypsin activation in saline-treated control animals lacking the CI-MPR. During caerulein-induced pancreatitis, trypsinogen activation in the pancreas of CI-MPR-deficient animals was about 40% higher than in wild-type animals but serum amylase levels were reduced and lung damage was unchanged. These data suggest that subcellular redistribution of cathepsin B, in itself, induces neither spontaneous trypsinogen activation nor pancreatitis. Furthermore, we clearly show that a marked increase in intracellular trypsinogen activation is not necessarily associated with greater disease severity.