S4B)

S4B). uncovered consistent genetic SR1078 alterations that explain the progression to a highly metastatic state (7-10). While genomic alterations create stable changes that increase cancer growth, transient alterations in the metastatic state of cancer cells can be induced by interactions with stromal cells, diverse physical cues, as well as by changes in the local tumor microenvironment. For example, the epithelial-to-mesenchymal transition (EMT) is a well characterized transcriptional program that endows cancer cells with a transient high metastatic ability (11). However, EMT might not be critical for PDAC dissemination or metastasis (12,13). Subpopulations of PDAC cells with cancer stem cell-like properties have also been described but it is unclear whether these cells are SR1078 the major source of metastases (14,15). In many cancer types, metastasis is thought to be driven by diverse extracellular cues that increased stem-like behavior as well as invasion and metastasis (16). PDAC in particular has an extensive desmoplastic stromal response that generates unique physical properties, including increased extracellular matrix stiffness and areas with limited oxygen and nutrient availability (17). However, whether or not PDAC metastasis is driven by features of the tumor microenvironment is unclear. Identification of key environmental factors could provide insights into the process of metastasis as well as aid in the development of novel therapeutic strategies. Genetically engineered mouse models of PDAC recapitulate key genetic events of the human disease. Cre-mediated expression of oncogenic KrasG12D in pancreatic cells of knock-in mice (or deletion of allows for the development of PDAC that can progress to gain multi-organ metastatic ability (19-23). Importantly, tumors arise from genetically defined lesions and evolve in their native context, providing the opportunity to identify the cancer cell intrinsic Mouse monoclonal to ERBB3 and extrinsic processes that contribute to tumor progression. Here, we developed a novel mouse model of human PDAC, which enabled the isolation and molecular characterization of a highly metastatic subpopulation of pancreatic cancer cells. We demonstrate that these highly metastatic cancer cells exists within hypoxic tumor areas and that the transcription factor Blimp1 drives their high metastatic potential. Gene expression signatures of the metastatic state, as well as of hypoxia-induced Blimp1-dependant genes predicts PDAC patient outcome. These findings highlight microenvironment-induced heterogeneity as a driver of pancreatic cancer progression toward its deadly metastatic phase. Results Generation of a system to identify and isolate a highly metastatic population of PDAC cells The chromatin-associated protein HMGA2 is a marker of increased malignancy in many tumor types, and high HMGA2 expression predicts poor prognosis in several major human cancer types, including PDAC (24-30). To determine whether neoplastic cells in genetically engineered mouse models of human PDAC also express Hmga2, we performed immunohistochemistry (IHC) on tumors at different stages of development. Hmga2 was not expressed in SR1078 cells in SR1078 the normal adult pancreas or PanINs in (mouse model: a Cre-reporter allele (knock-in allele, which is converted by Cre from its wild-type conformation (regulatory elements (20). In mice (referred to as mice), all cancer cells were Tomato positive and Hmga2-expressing cancer cells were both Tomato and GFP positive (Supplementary Fig. S1A and S1E). Open in a separate window Figure 1 Identification of a subpopulation of highly metastatic pancreatic cancer cells(A) Alleles in the model ((mice. FSC/SSC-gated lineageneg (CD45negCD31negF4/80negTer119neg) viable (DAPIneg) Tomatopos cells are shown. (C) Individual primary tumors and metastases (Mets) have variable proportions of GFPpos cells. Each dot is a tumor and the bar is the mean. (D) Metastatic ability of GFPneg and GFPpos subpopulations from individual tumors was assessed by intravenous (transplantation of GFPneg or GFPpos PDAC cells from an individual tumor from a mouse. Scale bars = 0.5 cm. (F) Number SR1078 of cells injected and the number of metastases is indicated for each matched pair. The average number of metastases per 104 GFPneg and GFPpos PDAC cells is shown. p-value < 0.008 by Wilcoxon matched-pair signed rank test. The dual fluorescent marking of cancer cells in mice provided us with the ability to isolate TomposGFPneg and TomposGFPpos cancer cells by fluorescence-activated cell sorting (FACS) (Supplementary Fig. S1F-S1G). Consistent with Hmga2 expression observed by IHC, variable percentages of cancer cells in individual tumors were GFPpos (Fig. 1B-1C). In.