A comprehensive characterization of pancreatic ductal carcinoma cell lines: towards the establishment of an in vitro research platform

Resistance of pancreatic cancer to gemcitabine treatment is dependent on mitochondria-mediated apoptosis

Palliative chemotherapy with gemcitabine, a common mode of treatment of pancreatic cancer, has little influence on patients' survival. We investigated the impact of anti-apoptotic Bcl-xL protein and its antagonist Bax on gemcitabine-induced apoptosis in human pancreatic carcinoma cells in vitro and in vivo. The level of Bcl-xL and Bax expression was determined in 3 established pancreatic cancer cell lines that differ in their sensitivity to gemcitabine-mediated apoptosis. Bcl-xL and Bax genes were transduced into Colo357 cells by retroviral infection. In addition, cells were transfected with c-FLIP to assess involvement of CD95 and caspase-8. The impact of Bax/Bcl-xL expression on gemcitabine-sensitivity in vivo was evaluated in orthotopic Colo357 tumors in SCID mice. The apoptotic index revealed a strong inverse correlation between Bcl-xL expression and gemcitabine-induced apoptosis in the pancreatic carcinoma cell lines tested. Caspase-8 and Bid were cleaved in Colo357 cells exposed to gemcitabine, and there was no correlation with either Bcl-xL or with Bax expression. In contrast, the lack of mitochondrial transmembrane potential transition, release of cytochrome-c and absence of caspase-9- and PARP-cleavage showed a strong correlation with Bcl-xL expression. Expression of c-FLIP significantly increased the resistance towards gemcitabine. Orthotopically growing Colo357-bcl-xl tumors in SCID mice were refractory to gemcitabine treatment, and in contrast to the in vitro data, Colo357-bax tumors exhibited a 12-fold greater tumor regression than Colo357-wild-type tumors in the control group. Gemcitabine-induced apoptosis involves the mitochondria-mediated signaling pathway. A functional restoration of this pathway appears to be essential to overcome the resistance mechanisms of pancreatic tumor cells and to improve the response to therapy as demonstrated by Bax overexpression in a clinically relevant tumor model.

Terminally modified oligodeoxynucleotides directed against p53 in an orthotopic xenograft model: a novel adjuvant treatment strategy for pancreatic ductal carcinoma

OBJECTIVES

Investigation of a terminally modified oligodeoxynucleotide (ODN) directed against p53 mRNA (p53-3' polyethylene glycol-5' tocopherol ODN as a novel drug for pancreatic ductal carcinoma therapy in vitro and in vivo.

METHODS

The impact of lipophilic modifications at the 5' end of p53-directed ODNs on cellular uptake was analyzed in vitro using proliferation assays, fluorescence-activated cell sorting analysis, and confocal laser scanning microscopy. The in vivo effects of p53-PT-ODN on the growth of orthotopically xenografted human pancreatic ductal carcinoma cells (PancTuI) were studied in SCID beige mice. Distribution was examined in vitro and in vivo using Cy3-labeled ODNs.

RESULTS

Terminally modified p53-PT-ODN showed excellent cellular uptake without using transfection reagents. Microscopically detectable levels of p53-PT-ODN were reached in vivo within 3 hours after intraperitoneal injection, even in extraperitoneal organs. At this time, Cy3-labeled p53-PT-ODN was found in solid tumor formations. We observed a significant inhibition of tumor growth (50%) in vivo at low doses of p53-PT-ODN, whereas at high doses, 2 of 9 animals had no detectable tumors at necropsy. When p53-PT-ODN was injected on the day of tumor cell inoculation, the growth inhibition of solid tumors was significantly stronger compared with that with delayed treatment.

CONCLUSIONS

p53-Directed modified ODNs might be of therapeutic value in pancreatic ductal carcinoma, particularly as adjuvant therapy after pancreatic tumor resection.

Multiple and synergistic deregulations of apoptosis-controlling genes in pancreatic carcinoma cells

Inability to die by apoptosis is one of the reasons for the deregulated growth of tumour cells and the frequently observed failure of chemotherapy. In this study we thought to identify the common and functionally important characteristics responsible for the apoptosis resistance of pancreatic tumour cells. We analysed cell surface expression level of death receptors CD95 and TRAIL-R1-4 as well as the expression profile of sixteen apoptosis-relevant proteins in five pancreatic carcinoma cell lines Capan1, Colo357, PancTuI, Panc89 and Panc1. These data were evaluated in the context of sensitivity towards anti-CD95 and TRAIL-mediated apoptosis. Here we report that except for resistant Panc1 cells, which only marginally expressed CD95, all other cell lines showed comparable levels of CD95 and TRAIL receptors irrespectively of their apoptotic phenotype. Interestingly, we found that the elevated expression of FLIP, Bcl-x_L and IAP in parallel with a downregulation of FADD and Bid was common for the resistant cell lines. Consequently, stable overexpression of XIAP, Bcl-x_L or dominant negative FADD in sensitive cells significantly reduced the death receptor mediated apoptosis while the overexpression of Bid rendered the resistant cells sensitive.

A novel cell line and xenograft model of ampulla of Vater adenocarcinoma

Ampulla of Vater cancers (AVC) are of clinical relevance, as they represent more than one-third of patients undergoing surgery for pancreaticoduodenal malignancies and have a better prognosis than periampullary cancers of pancreaticobiliary origin. The availability of cellular models is crucial to perform cell biology and pharmacological studies and clarify the relationship between AVC and pancreatic and biliary cancers. Numerous cell lines are available for pancreatic and biliary adenocarcinomas, while only two have been reported recently for AVC. These were derived from a poor and a well-differentiated AVC, and both had wild-type K- ras and mutated p53. We report the establishment of a novel AVC cell line (AVC1) derived from a moderately differentiated cancer, having a mutated K- ras, wild-type p53, and methylated p16. Thus, our cell line adds to the spectrum of available in vitro models representative of the different morphological and molecular presentations of primary AVC. We further characterized AVC1 for the expression of relevant cell surface molecules and sensitivity to chemotherapeutic agents of common clinical use. It expresses MHC-I and CD95/Fas, while HLA-DR, CD40, CD80, CD86, MUC-1, MUC-2, and ICAM-1/CD54 are absent. It has a low to moderate sensitivity to both 5-FU and gemcitabine, at variance with much higher sensitivity displayed by two pancreatic ductal carcinoma cell lines. Lastly, AVC1 can be readily xenografted in immunodeficient mice, making it a suitable model for pre-clinical studies.

Gene expression profiles of microdissected pancreatic ductal adenocarcinoma

In a search for new molecular markers of pancreatic ductal adenocarcinoma (PDAC), we compared the gene expression profiles of seven pancreatic carcinomas and one carcinoma of the papilla Vateri with those of duct cells from three non-neoplastic pancreatic tissues. In addition, the human pancreatic duct cell line and five PDAC cell lines (AsPC-1, BxPC-3, Capan-1, Capan-2, HPAF) were examined. RNA was extracted from microdissected tissue or cultured cell lines and analysed using a custom-made Affymetrix Chip containing 3023 genes, of which 1000 were known to be tumour associated. Hierarchical clustering revealed 81 differentially expressed genes. Of all the genes, 26 were downregulated in PDAC and 14 were upregulated in PDAC. In PDAC cell lines versus normal pancreatic duct cells, 21 genes were downregulated and 20 were upregulated. Of these 81 differentially expressed genes, 15 represented human genes previously implicated in the tumourigenesis of PDAC. From the genes that were so far not known to be associated with PDAC tumorigenesis, we selected ADAM9 for further validation because of its distinct overexpression in tumour tissue. Using immunohistochemistry, the over-expressed gene, ADAM9, was present in 70% of the PDACs analysed. In conclusion, using microarray technology we were able to identify a set of genes whose aberrant expression was associated with PDAC and may be used to target the disease.