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Supp figure 5

MycERT2 expression in pancreata of Mpdx1 and Mp48 mice is at a level comparable to that of endogenous c-Myc in proliferating neonatal pancreas

Supplementary Methods PDF file - 98K, Supplementary materials and methods

Supplementary Table S2 PDF file - 90K, Ingenuity transcription factor analysis of CIP2A depleted cells

The signature features of pancreatic ductal adenocarcinoma (PDAC) are its fibroinflammatory stroma, poor immune activity, and dismal prognosis. We show that acute activation of Myc in indolent pancreatic intraepithelial neoplasm (PanIN) epithelial cells in vivo is, alone, sufficient to trigger immediate release of instructive signals that together coordinate changes in multiple stromal and immune-cell types and drive transition to pancreatic adenocarcinomas that share all the characteristic stromal features of their spontaneous human counterpart. We also demonstrate that this Myc-driven PDAC switch is completely and immediately reversible: Myc deactivation/inhibition triggers meticulous disassembly of advanced PDAC tumor and stroma and concomitant death of tumor cells. Hence, both the formation and deconstruction of the complex PDAC phenotype are continuously dependent on a single, reversible Myc switch.Significance:We show that Myc activation in indolent KrasG12D-induced PanIN epithelium acts as an immediate pleiotropic switch, triggering tissue-specific signals that instruct all the diverse signature stromal features of spontaneous human PDAC. Subsequent Myc deactivation or inhibition immediately triggers a program that coordinately disassembles PDAC back to PanIN.See related commentary by English and Sears, p. 495.

Activating KRAS mutations are found in nearly all cases of pancreatic ductal adenocarcinoma (PDAC), yet effective clinical targeting of oncogenic KRAS remains elusive. Understanding of KRAS-dependent PDAC-promoting pathways could lead to the identification of vulnerabilities and the development of new treatments. We show that oncogenic KRAS induces BNIP3L/NIX expression and a selective mitophagy program that restricts glucose flux to the mitochondria and enhances redox capacity. Loss of Nix restores functional mitochondria to cells, increasing demands for NADPH reducing power and decreasing proliferation in glucose-limited conditions. Nix deletion markedly delays progression of pancreatic cancer and improves survival in a murine (KPC) model of PDAC. Although conditional Nix ablation in vivo initially results in the accumulation of mitochondria, mitochondrial content eventually normalizes via increased mitochondrial clearance programs, and pancreatic intraepithelial neoplasia (PanIN) lesions progress to PDAC. We identify the KRAS–NIX mitophagy program as a novel driver of glycolysis, redox robustness, and disease progression in PDAC.Significance:NIX-mediated mitophagy is a new oncogenic KRAS effector pathway that suppresses functional mitochondrial content to stimulate cell proliferation and augment redox homeostasis. This pathway promotes the progression of PanIN to PDAC and represents a new dependency in pancreatic cancer.This article is highlighted in the In This Issue feature, p. 1143

Supplementary Figure 5 PDF file - 82K, Prognostic value of CIP2A in advanced human breast cancer patient material and characterization of vinorelbine effects

Comparison of Myc-induced stromal phenotypes in KRasG12D-driven PanIN versus KRasG12D-driven lung adenoma

Supplementary Figure 4 PDF file - 269K, Characterization of hypomorphic CIP2A HOZ mice

Supplementary Figure 3 PDF file - 114K, RB expression is not needed for CIP2A-depletion induced senescence

Supplementary Figure 2 PDF file - 96K, Transcriptional regulation and functional role for CIP2A in response to p53 reactivation

MycVD induces proliferation to a similar extend as MycWT but is impaired in cellular transformation.

Figure legends for supplemental Figures S1-S6.

Liquid extraction surface analysis mass spectrometry differentiates normal from tumour tissue.

Description of additional methods and procedures used in the study. Also includes Supplementary References.

MYC-mediated pathogenesis in lung cancer continues to attract interest for new therapeutic strategies. In this study, we describe a transgenic mouse model of KRAS-driven lung adenocarcinoma that affords reversible activation of MYC, used here as a tool for lipidomic profiling of MYC-dependent lung tumors formed in this model. Advanced mass spectrometric imaging and surface analysis techniques were used to characterize the spatial and temporal changes in lipid composition in lung tissue. We found that normal lung tissue was characterized predominantly by saturated phosphatidylcholines and phosphatidylglycerols, which are major lipid components of pulmonary surfactant. In contrast, tumor tissues displayed an increase in phosphatidylinositols and arachidonate-containing phospholipids that can serve as signaling precursors. Deactivating MYC resulted in a rapid and dramatic decrease in arachidonic acid and its eicosanoid metabolites. In tumors with high levels of MYC, we found an increase in cytosolic phospholipase A2 (cPLA2) activity with a preferential release of membrane-bound arachidonic acid, stimulating the lipoxygenase (LOX) and COX pathways also amplified by MYC at the level of gene expression. Deactivating MYC lowered cPLA2 activity along with COX2 and 5-LOX mRNA levels. Notably, inhibiting the COX/5-LOX pathways in vivo reduced tumor burden in a manner associated with reduced cell proliferation. Taken together, our results show how MYC drives the production of specific eicosanoids critical for lung cancer cell survival and proliferation, with possible implications for the use of COX and LOX pathway inhibitors for lung cancer therapy. Cancer Res; 76(16); 4608–18. ©2016 AACR.

MycVD-sensitive genes.

Legend for Supplementary Figures S1-S6 and Supplementary Table S1-S3.

Tumors driven by activation of the transcription factor MYC generally show oncogene addiction. However, the gene expression programs that depend upon sustained MYC activity remain unknown. In this study, we employed a mouse model of liver carcinoma driven by a reversible tet-MYC transgene, combined with chromatin immunoprecipitation and gene expression profiling to identify MYC-dependent regulatory events. As previously reported, MYC-expressing mice exhibited hepatoblastoma- and hepatocellular carcinoma–like tumors, which regressed when MYC expression was suppressed. We further show that cellular transformation, and thus initiation of liver tumorigenesis, were impaired in mice harboring a MYC mutant unable to associate with the corepressor protein MIZ1 (ZBTB17). Notably, switching off the oncogene in advanced carcinomas revealed that MYC was required for the continuous activation and repression of distinct sets of genes, constituting no more than half of all genes deregulated during tumor progression and an even smaller subset of all MYC-bound genes. Altogether, our data provide the first detailed analysis of a MYC-dependent transcriptional program in a fully developed carcinoma and offer a guide to identifying the critical effectors contributing to MYC-driven tumor maintenance. Cancer Res; 76(12); 3463–72. ©2016 AACR.

LC-MS/MS method details for eicosanoid analysis (Tables S1 and S2); Lipid ID by accurate mass and tandem MS (Tables S3 and S4); Fold change for eicosanoid-related species with MYC activated (Table S5).

Mouse weights for all experiments.

Supplementary Figure legends

Gene Lists

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense stromal fibroinflammatory reaction that is a major obstacle to effective therapy. The desmoplastic stroma comprises many inflammatory cells, in particular mast cells as key components of the PDAC microenvironment, and such infiltration correlates with poor patient outcome. Indeed, it has been hypothesized that stromal ablation is critical to improve clinical response in patients with PDAC. Ibrutinib is a clinically approved Bruton's tyrosine kinase inhibitor that inhibits mast cells and tumor progression in a mouse model of β-cell tumorigenesis. Here, we show that ibrutinib is highly effective at limiting the growth of PDAC in both transgenic mouse and patient-derived xenograft models of the disease. In these various experimental settings, ibrutinib effectively diminished fibrosis, extended survival, and improved the response to clinical standard-of-care therapy. Our results offer a preclinical rationale to immediately evaluate the clinical efficacy of ibrutinib in patients with PDAC. Cancer Res; 75(8); 1675–81. ©2015 AACR.

Ibrutinib does not affect growth of pancreatic cancer cell lines.

Supplementary Figures 1-2 from Reversible Kinetic Analysis of Myc Targets In vivo Provides Novel Insights into Myc-Mediated Tumorigenesis

Ibrutinib and cromolyn treatment prevent mast cell degranulation in the tumor stroma.

Deregulated expression of the Myc transcription factor is a frequent causal mutation in human cancer. Thousands of putative Myc target genes have been identified in in vitro studies, indicating that Myc exerts highly pleiotropic effects within cells and tissues. However, the complexity and diversity of Myc gene targets has confounded attempts at identifying which of these genes are the critical targets mediating Myc-driven tumorigenesis in vivo. Acute activation of Myc in a reversibly switchable transgenic model of Myc-mediated β cell tumorigenesis induces rapid tumor onset, whereas subsequent Myc deactivation triggers equally rapid tumor regression. Thus, sustained Myc activity is required for tumor maintenance. We have used this reversibly switchable kinetic tumor model in combination with high-density oligonucleotide microarrays to develop an unbiased strategy for identifying candidate Myc-regulated genes responsible for maintenance of Myc-dependent tumors. Consistent with known Myc functions, some Myc-regulated genes are involved in cell growth, cycle, and proliferation. In addition, however, many Myc-regulated genes are specific to β cells, indicating that a significant component of Myc action is cell type specific. Finally, we identify a very restricted cadre of genes with expression that is inversely regulated upon Myc activation-induced tumor progression and deactivation-induced tumor regression. By definition, such genes are candidates for tumor maintenance functions. Combining reversibly switchable, transgenic models of tumor formation and regression with genomic profiling offers a novel strategy with which to deconvolute the complexities of oncogenic signaling pathways in vivo. (Cancer Res 2006; 66(9): 4591-601)

Background and aims: Hepatocytes undergo profound metabolic rewiring when primed to proliferate during compensatory regeneration and in hepatocellular carcinoma (HCC). However, the metabolic control of these processes is not fully understood. In order to capture the metabolic signature of proliferating hepatocytes, we applied state-of-the-art systems biology approaches to models of liver regeneration, pharmacologically and genetically activated cell proliferation, and HCC.Approach and results: Integrating metabolomics, lipidomics, and transcriptomics, we link changes in the lipidome of proliferating hepatocytes to altered metabolic pathways including lipogenesis, fatty acid desaturation, and generation of phosphatidylcholine (PC). We confirm this altered lipid signature in human HCC and show a positive correlation of monounsaturated PC with hallmarks of cell proliferation and hepatic carcinogenesis.Conclusions: Overall, we demonstrate that specific lipid metabolic pathways are coherently altered when hepatocytes switch to proliferation. These represent a source of targets for the development of therapeutic strategies and prognostic biomarkers of HCC.

It is unclear why some tissues are refractory to the mitogenic effects of the oncogene Myc. Here we show that Myc activation induces rapid transcriptional responses followed by proliferation in some, but not all, organs. Despite such disparities in proliferative response, Myc is bound to DNA at open elements in responsive (liver) and non-responsive (heart) tissues, but fails to induce a robust transcriptional and proliferative response in the heart. Using heart as an exemplar of a non-responsive tissue, we show that Myc-driven transcription is re-engaged in mature cardiomyocytes by elevating levels of the positive transcription elongation factor (P-TEFb), instating a large proliferative response. Hence, P-TEFb activity is a key limiting determinant of whether the heart is permissive for Myc transcriptional activation. These data provide a greater understanding of how Myc transcriptional activity is determined and indicate modification of P-TEFb levels could be utilised to drive regeneration of adult cardiomyocytes for the treatment of heart myopathies., Levels of the transcription factor Myc are deregulated in a range of different cancers. Here the authors show that Myc induces rapid transcriptional responses in some mouse tissues (liver), but not others (heart), and that transcriptional and proliferative responses in cardiomyocytes depend on the positive transcription elongation factor (P-TEFb).

Gerard Evan is Head of Department and Sir William Dunn Professor at the Department of Biochemistry, University of Cambridge, UK. Driven by his innate passion to understand how things work, Gerard has devoted much of his career to understanding the molecular basis of cancer, particularly the roles played by oncogenes such as Myc. His work has helped elucidate the complex role that this gene plays in cell proliferation and apoptosis, and paved new avenues for the treatment of aggressive cancers. In this interview, Gerard provides an overview of what is known about the role of Myc in normal and cancer cells and provides a persuasive argument for the application of 'impersonalised therapy' involving Myc inhibition as part of future chemotherapeutic drug regimes.

Significance Breast cancer remains a leading cause for cancer-related mortality worldwide. All breast cancers, including the more difficult-to-treat, higher-grade, and triple-negative subtypes of breast cancer, exhibit strong genetic heterogeneity, which hampers treatment and fuels relapse. Our study advances the development of successful treatment approaches by unravelling the mechanistic basis of one form of heterogeneity arising from mutualism between high- and low-Myc–expressing clones in breast cancer. We use this mechanistic understanding to build an executable in silico model of oncogenic Myc/Ras/p53/Wnt signal cross talk for each Myc-expressing clone, separately and together, and then use this model to identify potential therapeutic vulnerabilities, which we then verify experimentally., Cells with higher levels of Myc proliferate more rapidly and supercompetitively eliminate neighboring cells. Nonetheless, tumor cells in aggressive breast cancers typically exhibit significant and stable heterogeneity in their Myc levels, which correlates with refractoriness to therapy and poor prognosis. This suggests that Myc heterogeneity confers some selective advantage on breast tumor growth and progression. To investigate this, we created a traceable MMTV-Wnt1–driven in vivo chimeric mammary tumor model comprising an admixture of low-Myc– and reversibly switchable high-Myc–expressing clones. We show that such tumors exhibit interclonal mutualism wherein cells with high-Myc expression facilitate tumor growth by promoting protumorigenic stroma yet concomitantly suppress Wnt expression, which renders them dependent for survival on paracrine Wnt provided by low-Myc–expressing clones. To identify any therapeutic vulnerabilities arising from such interdependency, we modeled Myc/Ras/p53/Wnt signaling cross talk as an executable network for low-Myc, for high-Myc clones, and for the 2 together. This executable mechanistic model replicated the observed interdependence of high-Myc and low-Myc clones and predicted a pharmacological vulnerability to coinhibition of COX2 and MEK. This was confirmed experimentally. Our study illustrates the power of executable models in elucidating mechanisms driving tumor heterogeneity and offers an innovative strategy for identifying combination therapies tailored to the oligoclonal landscape of heterogenous tumors.

Aberrant activation of the Wnt/β-catenin signaling pathway is associated with numerous human cancers and often correlates with the overexpression or amplification of the c-myc oncogene. Paradoxical to the cellular transformation potential of c-Myc is its ability to also induce apoptosis. Using an inducible c-MycER expression system, we found that Wnt/β-catenin signaling suppressed apoptosis by inhibiting c-Myc–induced release of cytochrome c and caspase activation. Both cyclooxygenase 2 and WISP-1 were identified as effectors of the Wnt-mediated antiapoptotic signal. Soft agar assays showed that neither c-Myc nor Wnt-1 alone was sufficient to induce cellular transformation, but that Wnt and c-Myc coordinated in inducing transformation. Furthermore, coexpression of Wnt-1 and c-Myc induced high-frequency and rapid tumor growth in nude mice. Extensive apoptotic bodies were characteristic of c-Myc–induced tumors, but not tumors induced by coactivation of c-Myc and Wnt-1, indicating that the antiapoptotic function of Wnt-1 plays a critical role in the synergetic action between c-Myc and Wnt-1. These results elucidate the molecular mechanisms by which Wnt/β-catenin inhibits apoptosis and provide new insight into Wnt signaling-mediated oncogenesis.

Zacarías-Fluck, et al identify and validate the Wnt receptor Fzd9 as a key effector of Myc-Wnt signaling cross-talk in a mouse model of Myc-driven pancreatic insulinomas., The huge cadre of genes regulated by Myc has obstructed the identification of critical effectors that are essential for Myc-driven tumorigenesis. Here, we describe how only the lack of the receptor Fzd9, previously identified as a Myc transcriptional target, impairs sustained tumor expansion and β-cell dedifferentiation in a mouse model of Myc-driven insulinoma, allows pancreatic islets to maintain their physiological structure and affects Myc-related global gene expression. Importantly, Wnt signaling inhibition in Fzd9-competent mice largely recapitulates the suppression of proliferation caused by Fzd9 deficiency upon Myc activation. Together, our results indicate that the Wnt signaling receptor Fzd9 is essential for Myc-induced tumorigenesis in pancreatic islets.

Myc+/−haploinsufficient mice and mice with deletedMycenhancers express reduced levels of the pleiotropic transcription factor Myc. Such mice are viable, with relatively mild pathologies, but show delay in onset of certain cancers. However, many phenotypes arising from germline gene perturbation are indirect consequences of adaptive developmental compensation and so do not translate to equivalent phenotypes when applied to adults. To ascertain whether systemic Myc hypomorphism also conferred cancer protection when acutely imposed in adults, and what the side-effects of this might be, we constructed a genetically engineered mouse model in which Myc expression may be systemically and reversibly hypomorphed at will. Acute imposition of Myc hypomorphism in adult mice conferred potent protection against both KRasG12D-driven lung and pancreatic cancers yet elicited only mild haematopoietic side effects. These side effects were completely suppressed by imposing Myc hypomorphism metronomically – a regimen that nonetheless retained potent cancer prophylaxis. Our data identify a key bottleneck at the transition from pre-malignant hyperplasia to overt tumour that is peculiarly reliant on levels of Myc that are higher than those required for most adult physiology, offering a possible window of opportunity for Myc inhibition in cancer prophylaxis.

The genomic complexity and heterogeneity of high-grade serous ovarian cancer (HGSOC) has hampered the realisation of successful therapies and effective personalised treatment is an unmet clinical need. Here we show that primary HGSOC spheroid models can be used to predict drug response and use them to demonstrate that somatic copy number alterations (SCNAs) in frequently amplified HGSOC cancer genes significantly correlate with gene expression and drug response. These genes are often located in areas of the genome with frequent clonal SCNAs. MYC chromosomal copy number is associated with ex-vivo and clinical response to paclitaxel and ex-vivo response to mTORC1/2 inhibition. Activation of the mTOR survival pathway in the context to MYC-amplified HGSOC is mostly due to increased prevalence of SCNAs in genes from the PI3K pathway. These results suggest that SCNAs encompassing driver genes could be used to inform therapeutic response in the context of clinical trials testing personalised medicines.

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related deaths. Whilst mutations in Kras and over-expression of Myc are commonly found in patients, the role of altered lipid metabolism in lung cancer and its interplay with oncogenic Myc is poorly understood. Here we use a transgenic mouse model of Kras-driven lung adenocarcinoma with reversible activation of Myc, in combination with surface analysis lipid profiling of lung tumours and transcriptomics, to study the effect of Myc activity on cholesterol homeostasis. Our findings reveal that activation of Myc leads to the accumulation of cholesteryl esters (CE), stored in lipid droplets. Subsequent Myc deactivation leads to further increases in CEs, in contrast to tumours in which Myc was never activated. Gene expression analysis linked cholesterol transport and storage pathways to Myc activity. Our results suggest that increased Myc activity is associated with increased cholesterol influx, reduced efflux and accumulation of CE-rich lipid droplets in lung tumours. Targeting cholesterol homeostasis is proposed as a promising avenue to explore for novel treatments of lung cancer, with diagnostic and stratification potential in human NSCLC.

The signature features of pancreatic ductal adenocarcinoma (PDAC) are its fibroinflammatory stroma, poor immune activity, and dismal prognosis. We show that acute activation of Myc in indolent pancreatic intraepithelial neoplasm (PanIN) epithelial cells in vivo is, alone, sufficient to trigger immediate release of instructive signals that together coordinate changes in multiple stromal and immune-cell types and drive transition to pancreatic adenocarcinomas that share all the characteristic stromal features of their spontaneous human counterpart. We also demonstrate that this Myc-driven PDAC switch is completely and immediately reversible: Myc deactivation/inhibition triggers meticulous disassembly of advanced PDAC tumor and stroma and concomitant death of tumor cells. Hence, both the formation and deconstruction of the complex PDAC phenotype are continuously dependent on a single, reversible Myc switch. Significance: We show that Myc activation in indolent KrasG12D-induced PanIN epithelium acts as an immediate pleiotropic switch, triggering tissue-specific signals that instruct all the diverse signature stromal features of spontaneous human PDAC. Subsequent Myc deactivation or inhibition immediately triggers a program that coordinately disassembles PDAC back to PanIN. See related commentary by English and Sears, p. 495.

Improving the early detection and chemoprevention of lung cancer are key to improving outcomes. The pathobiology of early squamous lung cancer is poorly understood. We have shown that amplification of sex-determining region Y-box 2 (SOX2) is an early and consistent event in the pathogenesis of this disease, but its functional oncogenic potential remains uncertain. We tested the impact of deregulated SOX2 expression in a novel organotypic system that recreates the molecular and microenvironmental context in which squamous carcinogenesis occurs.(1) To develop an in vitro model of bronchial dysplasia that recapitulates key molecular and phenotypic characteristics of the human disease; (2) to test the hypothesis that SOX2 deregulation is a key early event in the pathogenesis of bronchial dysplasia; and (3) to use the model for studies on pathogenesis and chemoprevention.We engineered the inducible activation of oncogenes in immortalized bronchial epithelial cells. We used three-dimensional tissue culture to build an organotypic model of bronchial dysplasia.We recapitulated human bronchial dysplasia in vitro. SOX2 deregulation drives dysplasia, and loss of tumor promoter 53 is a cooperating genetic event that potentiates the dysplastic phenotype. Deregulated SOX2 alters critical genes implicated in hallmarks of cancer progression. Targeted inhibition of AKT prevents the initiation of the dysplastic phenotype.In the appropriate genetic and microenvironmental context, acute deregulation of SOX2 drives bronchial dysplasia. This confirms its oncogenic potential in human cells and affords novel insights into the impact of SOX2 deregulation. This model can be used to test therapeutic agents aimed at chemoprevention.

Activating KRAS mutations are found in nearly all cases of pancreatic ductal adenocarcinoma (PDAC), yet effective clinical targeting of oncogenic KRAS remains elusive. Understanding of KRAS-dependent PDAC-promoting pathways could lead to the identification of vulnerabilities and the development of new treatments. We show that oncogenic KRAS induces BNIP3L/NIX expression and a selective mitophagy program that restricts glucose flux to the mitochondria and enhances redox capacity. Loss of Nix restores functional mitochondria to cells, increasing demands for NADPH reducing power and decreasing proliferation in glucose-limited conditions. Nix deletion markedly delays progression of pancreatic cancer and improves survival in a murine (KPC) model of PDAC. Although conditional Nix ablation in vivo initially results in the accumulation of mitochondria, mitochondrial content eventually normalizes via increased mitochondrial clearance programs, and pancreatic intraepithelial neoplasia (PanIN) lesions progress to PDAC. We identify the KRAS–NIX mitophagy program as a novel driver of glycolysis, redox robustness, and disease progression in PDAC. Significance: NIX-mediated mitophagy is a new oncogenic KRAS effector pathway that suppresses functional mitochondrial content to stimulate cell proliferation and augment redox homeostasis. This pathway promotes the progression of PanIN to PDAC and represents a new dependency in pancreatic cancer. This article is highlighted in the In This Issue feature, p. 1143

It is unclear why some tissues are refractory to the mitogenic effects of the pleiotropic transcription factor Myc, even when its expression is deregulated. We have developed an in vivo model permitting determination of the early transcriptional consequences of Myc activation across all tissues of an adult mouse. Myc activation induces rapid transcriptional responses, followed by cell proliferation in some, but not all, organs. Despite such disparities in proliferative response, Myc bound DNA at open promotor and enhancer elements, in representative responsive (liver) and non-responsive (heart) tissues, but failed to induce a robust transcriptional and proliferative response in the heart. Therefore, the determinants of transcriptional responsiveness are distinct from chromatin state and DNA binding by Myc. Using heart as an exemplar of a non-responsive tissue, we show that Myc-driven transcription may be re-engaged in mature cardiomyocytes by elevating levels of the P-TEFb, instating a profound proliferative response to Myc. These data indicate that the cardiac epigenomic architecture does not preclude Myc binding to E-boxes; rather, it is the inability of Myc to drive transcriptional output from Myc target genes that thwarts cardiomyocyte proliferation. Hence, P-TEFb activity is a key limiting determinant of whether or not an individual tissue is permissive for Myc transcriptional activation and mitogenesis. These data provide not only a greater understanding of how Myc transcriptional activity is determined in cellular contexts, they also indicate that modification of the expression levels of the transcriptional co-factor P-TEFb could be a means through which adult cardiomyocytes could be regenerated for the treatment of heart conditions.

SUMMARYPancreatic ductal adenocarcinoma (PDAC) is characterized by its dismal prognosis and its signature fibroinflammatory phenotype. We show that activation of Myc in PanIN epithelial cells is alone sufficient to instruct and maintain immediate transition of indolent PanINs to PDACs phenotypically identical to the spontaneous human disease. Myc does this by inducing a distinct, tissue-specific ensemble of instructive signals that, together, coordinate changes in multiple, stromal and inflammatory cell types to generate the signature PDAC stroma. We also demonstrate that the Myc PDAC switch is completely reversible and that Myc deactivation immediately triggers meticulous disassembly of both PDAC tumor and stroma. Hence, both the formation and deconstruction of the complex PDAC phenotype may be mediated by a single, reversible molecular switch.SIGNIFICANCEPancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis and lacks effective therapies. We show that Myc is a single molecular switch that directly and immediately instructs transition from indolent KRasG12D-induced PanIN to the characteristic complex, multi-cell-type fibroinflammatory and immune-cold PDAC phenotype through the release of a distinct, tissuespecific set of instructive signals. The same combination of KRasG12Dand Myc drives a very different phenotype in lung, indicating that the principal phenotypes of adenocarcinomas are dictated by tissue of origin not specific oncogenes. We also show that the Myc switch is immediately and completely reversible: blocking Myc function triggers meticulous disassembly of the entire PDAC tumor-stromal edifice demonstrating that phenotypic complexity is not a barrier to effective treatment of cancers.