Annual Review of Pathology: Mechanisms of Disease, 5, 99C118. bypass in tumors that spontaneously arise from premalignant lesions remains unclear. In particular, there is an extensive reprogramming of the cancer genome resulting in loss of genetic programs of cell differentiation and gain of gene expression programs of embryonic stem cells (ESCs) (Ben\Porath et al., 2008). While many comparisons have been made between tumor cells and their normal counterparts, there is much to learn by comparing malignant cells to their precursor premalignant lesions being both populations expressing the same driving oncogene. To investigate the molecular changes associated with the transition from premalignant senescent lesions to malignant tumors, we took gamma-secretase modulator 2 advantage of genetically engineered mouse models (GEMMs) of pancreatic ductal adenocarcinoma (PDAC) gamma-secretase modulator 2 that mimic the progression of the human disease. Activating Kras mutations in the pancreas lead to premalignant lesions known as pancreatic intraepithelial neoplasias (PanINs), which are largely nonproliferative and contain cells with markers of cellular senescence (Caldwell et al., 2012). We thus compared the transcriptome and biological properties of PanIN and PDAC cells. PDAC cells express genes regulated by Stat3 and Myc and have low levels of genes repressed by NF\B. They also expressed mitochondrial genes and genes in common with stem cells. Consistent with their transcriptome, PDAC cells exhibited stem cell properties and displayed sensitivity to treatment with the mitochondrial complex I inhibitor metformin or to shRNAs against Stat3. Stemness was also stimulated in PanIN cells by LPS and in human primary cells that bypassed Ras\induced senescence due to attenuation of ERK signaling. Mouse monoclonal to Glucose-6-phosphate isomerase Taken together, our results link bypass of senescence with Stat3\dependent stemness and metformin sensitivity and provide insights into the association between cancer and aging. 2.?RESULTS 2.1. The transition from PanIN to PDAC involves acquisition of stem cell and epithelial\mesenchymal transition gene expression modules Low\grade PanIN lesions (PanIN1) are frequent in old individuals without pancreatic cancer but high\grade lesions (PanIN2 and PanIN3) are rare in the normal pancreas. In contrast, PanIN3 lesions are frequent in patients with pancreatic cancer (Liszka et al., 2011). These findings are consistent with the idea that PanIN lesions are precursors of pancreatic adenocarcinoma, thereby rising important questions about the mechanisms of progression from PanIN to cancer. Since PanIN lesions display markers of cellular senescence, their progression to cancer must bypass this tumor suppressor mechanism. To understand the changes associated with the transition of premalignant to malignant lesions, we developed in vitro models of different stages of pancreatic cancer progression. For early\stage disease, we established pancreatic epithelial cell lines from activation (Kras*) in vivo. Adapted from Wilentz et al. (2000). Mouse pancreatic ductal cell lines were established from the indicated lesions of of triplicates of 100 cells counts are indicated at the bottom of each panel, test were analyzed with the Babelomics 4.3 platform. The number of transcripts in each category (nonmutually exclusive) is usually indicated. (b) Validation by qPCR of the microarray data in the indicated cell lines and for the indicated genes, which are involved in epithelial\mesenchymal transition (EMT). Mean of triplicates??test were analyzed with the Babelomics 4.3 platform. The terms obtained which may explain the transformed phenotype of the gamma-secretase modulator 2 IMR90 hTERT/HRasG12V/shERK2\expressing cells and their associated transcripts are grouped in the indicated general categories. The number of transcripts in each category (nonmutually exclusive) is usually indicated. (c) Several stem cell gene expression signatures showing dedifferentiation in IMR90 hTERT/HRasG12V/shERK2\expressing cells were revealed by GSEA. (d) GSEA for the most significant signature in (c) (WONG EMBRYONIC STEM CELL CORE; M7079). (e) Gene expression signatures suggesting upregulation of STAT3, c\MYC, and the WNT pathway in IMR90 hTERT/HRasG12V/shERK2\expressing cells. (f) Immunoblots for the indicated proteins in extracts from wild\type (WT) or Erk2\null MEF, and IMR90 or human mammary epithelial cell (HMEC) cells expressing hTERT and the indicated vectors: shCTR, nontargeting shRNA; shERK, shRNA targeting ERK2; V, empty vector; R, vector expressing HRasG12V 2.3. Bypass from senescence is usually associated with the emergence of cells with stemness properties To determine whether our findings at the gene expression level are transposable to a phenotype of CSCs,.