Mutant p53R270H drives altered metabolism and increased invasion in pancreatic ductal adenocarcinoma.

Pancreatic cancer is characterized by nearly universal activating mutations in KRAS. Among other somatic mutations, TP53 is mutated in more than 75% of human pancreatic tumors. Genetically engineered mice have proven instrumental in studies of the contribution of individual genes to carcinogenesis. Oncogenic Kras mutations occur early during pancreatic carcinogenesis and are considered an initiating event. In contrast, mutations in p53 occur later during tumor progression. In our model, we recapitulated the order of mutations of the human disease, with p53 mutation following expression of oncogenic Kras. Further, using an inducible and reversible expression allele for mutant p53, we inactivated its expression at different stages of carcinogenesis. Notably, the function of mutant p53 changes at different stages of carcinogenesis. Our work establishes a requirement for mutant p53 for the formation and maintenance of pancreatic cancer precursor lesions. In tumors, mutant p53 becomes dispensable for growth. However, it maintains the altered metabolism that characterizes pancreatic cancer and mediates its malignant potential. Further, mutant p53 promotes epithelial-mesenchymal transition (EMT) and cancer cell invasion. This work generates new mouse models that mimic human pancreatic cancer and expands our understanding of the role of p53 mutation, common in the majority of human malignancies.

Mesenchymal Stem Cells Promote Pancreatic Tumor Growth by Inducing Alternative Polarization of Macrophages.

UNLABELLED: Pancreatic cancer is characterized by an extensive desmoplastic stroma, the functional relevance of which is poorly understood. Activated fibroblasts are a prevalent component of the stroma, and traditionally, these cells have been considered as a homogenous population derived from pancreatic stellate cells. In this study, we highlight a previously unappreciated heterogeneity of the fibroblast population within the stroma. In particular, a subset of stromal fibroblasts has characteristics of mesenchymal stem cells (MSCs). MSCs are present in the normal pancreas as well as in the carcinomatous pancreas (CA-MSCs). Here, we determine that CA-MSCs have increased tumor-promoting function compared with MSCs in normal pancreas. This ability to promote tumor growth is associated with CA-MSCs' unique ability to promote alternative macrophage polarization. Thus, our study identifies a previously uncharacterized cell population within the stroma and sheds light on tumor-promoting interactions between different components of the stroma. SIGNIFICANCE: Targeting the stroma is emerging as a new paradigm in pancreatic cancer; however, efforts to that effect are hampered by our limited understanding of the nature and function of stromal components. Here, we uncover previously unappreciated heterogeneity within the stroma and identify interactions among stromal components that promote tumor growth and could be targeted therapeutically.