Establishment and characterization of a novel pancreatic cancer tissue xenograft model.

Abstract

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Pancreatic cancer has a 5-year survival rate of only 3% and is the fourth leading cause of cancer deaths. It is usually only detected at an advanced stage and highly resistant to chemotherapy. There is a need for clinically relevant experimental pancreatic cancer models that can be used toward a better understanding of the disease at the molecular level, its earlier detection and improved therapy. We have previously shown that primary human cancer tissues, irrespective of grade, can be successfully grown or maintained as subrenal capsule xenografts in immuno-deficient mice. In the present study we have used this methodology to develop a new pancreatic cancer model. Pieces of pancreatic tumor tissue from patients were grafted under renal capsules of Rag-2M or NOD-SCID mice. Two tumor types were used, i.e. poorly-differentiated infiltrating adenocarcinoma and pancreatobiliary adenocarcinoma. After 1-3 months, grafts were harvested for transplantation and comparison with original tissues. Tissues were characterized via H&E and immunohistochemical staining using a variety of markers. Sensitivity of xenografts to chemotherapy was assessed via treatment of mice carrying transplantable tumors with gemcitabine, a drug used with minor success in clinical treatment of pancreatic cancer. The effects of the treatment were evaluated via changes in tumor size and survival time. It was found that both types of primary pancreatic cancers could be successfully engrafted; in both cases transplantable tumor tissue lines were developed. Histopathological analysis using e.g., cytokeratins, Smad4, human Ki-67 as markers showed great similarity between post-graft and original tissues indicating major preservation of immunophenotypes. From the transplantable infiltrating adenocarcinoma line a highly metastatic as well as a much less aggressive subline were developed. Treatment with gemcitabine led to significant inhibition of the growth of the two sublines and increased host survival. The pancreatobiliary adenocarcinoma transplantable line contains two tissue types; two sublines showing marked differences in immunohistopathology (Smad4, CK7, CK20 and S100A4) and growth rate have been established via microdissection. The results of the present study show that subrenal capsule grafting of primary human pancreatic cancer tissues in immuno-deficient mice can lead to viable xenografts and transplantable tumor tissue lines retaining major characteristics of the original tissues and showing responsiveness to gemcitabine. The methodology also allows isolation of different tumor sublines. As such, the subrenal capsule pancreatic cancer xenografts appear to provide useful models for studying the tumor biology (e.g., heterogeneity) of the disease and for evaluating its response to chemotherapeutic agents.