Non-canonical functions of SNAIL drive context-specific cancer progression

SNAIL is a key transcriptional regulator in embryonic development and cancer. Its effects in physiology and disease are believed to be linked to its role as a master regulator of epithelial-to-mesenchymal transition (EMT). Here, we report EMT-independent oncogenic SNAIL functions in cancer. Using genetic models, we systematically interrogated SNAIL effects in various oncogenic backgrounds and tissue types. SNAIL-related phenotypes displayed remarkable tissue- and genetic context-dependencies, ranging from protective effects as observed in KRAS- or WNT-driven intestinal cancers, to dramatic acceleration of tumorigenesis, as shown in KRAS-induced pancreatic cancer. Unexpectedly, SNAIL-driven oncogenesis was not associated with E-cadherin downregulation or induction of an overt EMT program. Instead, we show that SNAIL induces bypass of senescence and cell cycle progression through p16^INK4A-independent inactivation of the Retinoblastoma (RB)-restriction checkpoint. Collectively, our work identifies non-canonical EMT-independent functions of SNAIL and unravel its complex context-dependent role in cancer.

Genetic Screens Identify a Context-Specific PI3K/p27Kip1 Node Driving Extrahepatic Biliary Cancer

Biliary tract cancer ranks among the most lethal human malignancies, representing an unmet clinical need. Its abysmal prognosis is tied to an increasing incidence and a fundamental lack of mechanistic knowledge regarding the molecular basis of the disease. Here, we show that the Pdx1-positive extrahepatic biliary epithelium is highly susceptible toward transformation by activated PIK3CAH1047R but refractory to oncogenic KrasG12D. Using genome-wide transposon screens and genetic loss-of-function experiments, we discover context-dependent genetic interactions that drive extrahepatic cholangiocarcinoma (ECC) and show that PI3K signaling output strength and repression of the tumor suppressor p27Kip1 are critical context-specific determinants of tumor formation. This contrasts with the pancreas, where oncogenic Kras in concert with p53 loss is a key cancer driver. Notably, inactivation of p27Kip1 permits KrasG12D-driven ECC development. These studies provide a mechanistic link between PI3K signaling, tissue-specific tumor suppressor barriers, and ECC pathogenesis, and present a novel genetic model of autochthonous ECC and genes driving this highly lethal tumor subtype.

SIGNIFICANCE

We used the first genetically engineered mouse model for extrahepatic bile duct carcinoma to identify cancer genes by genome-wide transposon-based mutagenesis screening. Thereby, we show that PI3K signaling output strength and p27Kip1 function are critical determinants for context-specific ECC formation. This article is highlighted in the In This Issue feature, p. 2945.

Abstract 391: Evolutionary trajectories and KRAS gene dosage define pancreatic cancer phenotypes

Pancreatic ductal adenocarcinoma (PDAC) has frequent alterations in few genes (KRAS, CDKN2A/TP53/SMAD4) and extensive heterogeneity of cancer drivers beyond. The expectation that mutational landscapes of rare drivers could explain phenotypic diversity has -with few exceptions- not come true. Likewise, PDAC metastasis is not understood, and comparisons of primary/metastasis pairs did not find recurrently mutated “metastasis genes”. Here we show that key aspects of PDAC biology are defined by gene-dosage variation of PDAC signature genes, evolving along distinct evolutionary routes. We found increased gene dosage of the initiating KRAS mutation (KRASMUT-iGD) in human PDAC precursors. Mouse models revealed the importance of KrasMUT-iGD for both, early progression and metastasis, rationalizing the high frequency of PDAC dissemination at diagnosis. To overcome limitations posed to gene dosage studies by PDAC´s stroma-richness, we developed murine cell culture resources comprising 135 primaries/metastases. Integrative analyses of their genomes, transcriptomes and tumor phenotypes, combined with human studies and functional analyses revealed a series of additional KrasMUT-dosage effects: different KrasMUT-levels define distinct cellular morphologies, histopathologies and clinical outcomes, with highest KrasMUT-expression underlying the most aggressive undifferentiated phenotypes. We also observed KrasMUT-dosage-associated cellular plasticity, including epithelial-to-mesenchymal transition. Mechanistically, oncogenic dosage-variation is linked to distinct evolutionary routes, characterized by defined types/states of tumor-suppressor alterations: Phylogenetic tracking studies revealed convergent evolution of KrasMUT-iGD-gains, with dependence on prior homozygous Cdkn2a- or Trp53-loss. By contrast, in Cdkn2aHET cancers, amplifications of known and novel oncogenes (Myc, Yap1, Nfkb2) collaborate with KrasMUT-HET to drive progression, yet with lower metastatic potential. These results also reveal oncogene-selective/context-dependent Cdkn2a-haploinsufficiency, for which Tgfβ pathway alterations provide permissiveness. Our study uncovers universal principles underlying PDAC biology and phenotypic diversification. It describes evolutionary trajectories, identifies their genetic hallmarks and shows how oncogenic dosage-variation is differentially licensed along individual routes to control critical disease characteristics, including early progression, histopathology, metastasis, cellular plasticity and clinical aggressiveness.

Citation Format: Sebastian Mueller, Thomas Engleitner, Roman Maresch, Magdalena Zukowska, Sebastian Lange, Thorsten Kaltenbacher, Björn Konukiewitz, Rupert Öllinger, Maximilian Zwiebel, Alex Strong, Hsi-Yu Yen, Ruby Banerjee, Sandra Louzada, Beiyuan Fu, Barbara Seidler, Juliana Götzfried, Kathleen Schuck, Zonera Hassan, Nina Schönhuber, Sabine Klein, Christian Veltkamp, Mathias Friedrich, Lena Rad, Maxim Barenboim, Christoph Ziegenhain, Julia Hess, Oliver M. Dovey, Stefan Eser, Swati Parekh, Fernando Constantino-Casas, Jorge de la Rosa, Marta I. Sierra, Mario Fraga, Julia Mayerle, Günter Klöppel, Roland M. Schmid, Juan Cadiñanos, Pentao Liu, George Vassiliou, Wilko Weichert, Katja Steiger, Wolfgang Enard, Fengtang Yang, Kristian Unger, Günter Schneider, Ignacio Varela, Allan Bradley, Dieter Saur, Roland Rad. Evolutionary trajectories and KRAS gene dosage define pancreatic cancer phenotypes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 391.

Evolutionary routes and KRAS dosage define pancreatic cancer phenotypes

The poor correlation of mutational landscapes with phenotypes limits our understanding of the pathogenesis and metastasis of pancreatic ductal adenocarcinoma (PDAC). Here we show that oncogenic dosage-variation has a critical role in PDAC biology and phenotypic diversification. We find an increase in gene dosage of mutant KRAS in human PDAC precursors, which drives both early tumorigenesis and metastasis and thus rationalizes early PDAC dissemination. To overcome the limitations posed to gene dosage studies by the stromal richness of PDAC, we have developed large cell culture resources of metastatic mouse PDAC. Integration of cell culture genomes, transcriptomes and tumour phenotypes with functional studies and human data reveals additional widespread effects of oncogenic dosage variation on cell morphology and plasticity, histopathology and clinical outcome, with the highest KrasMUT levels underlying aggressive undifferentiated phenotypes. We also identify alternative oncogenic gains (Myc, Yap1 or Nfkb2), which collaborate with heterozygous KrasMUT in driving tumorigenesis, but have lower metastatic potential. Mechanistically, different oncogenic gains and dosages evolve along distinct evolutionary routes, licensed by defined allelic states and/or combinations of hallmark tumour suppressor alterations (Cdkn2a, Trp53, Tgfβ-pathway). Thus, evolutionary constraints and contingencies direct oncogenic dosage gain and variation along defined routes to drive the early progression of PDAC and shape its downstream biology. Our study uncovers universal principles of Ras-driven oncogenesis that have potential relevance beyond pancreatic cancer.

Diagnostic accuracy of contrast-enhanced computed tomography and positron emission tomography with 18-FDG in identifying malignant solitary pulmonary nodules

Contrast-enhanced computed tomography (CECT) and positron emission tomography with 18-FDG (FDG-PET/CT) are used to identify malignant solitary pulmonary nodules. The aim of the study was to evaluate the accuracy of CECT and FDG-PET/CT in diagnosing the etiology of solitary pulmonary nodule (SPN). Eighty patients with newly diagnosed SPN >8 mm were enrolled. The patients were scheduled for either or both, CECT and FDG-PET/CT. The nature of SPN (malignant or benign) was determined either by its pathological examination or radiological criteria. In 71 patients, the etiology of SPN was established and these patients were included in the final analysis. The median SPN diameter in these patients was 13 mm (range 8-30 mm). Twenty-two nodules (31%) were malignant, whereas 49 nodules were benign. FDG-PET/CT was performed in 40 patients, and CECT in 39 subjects. Diagnostic accuracy of CECT was 0.58 (95% confidence interval [CI] 0.41-0.74). The optimal cutoff level discriminating between malignant and benign SPN was an enhancement value of 19 Hounsfield units, for which the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CECT were 100%, 37%, 32%, and 100%, respectively. Diagnostic accuracy of FDG-PET/CT reached 0.9 (95% CI 0.76-0.9). The optimal cutoff level for FDG-PET/CT was maximal standardized uptake value (SUV max) 2.1. At this point, the sensitivity, specificity, PPV, and NPV were 77%, 92%, 83%, and 89%, respectively. The diagnostic accuracy of FDG-PET/CT is higher than that of CECT. The advantage of CECT is its high sensitivity and negative predictive value.

A conditional piggyBac transposition system for genetic screening in mice identifies oncogenic networks in pancreatic cancer

Here we describe a conditional piggyBac transposition system in mice and report the discovery of large sets of new cancer genes through a pancreatic insertional mutagenesis screen. We identify Foxp1 as an oncogenic transcription factor that drives pancreatic cancer invasion and spread in a mouse model and correlates with lymph node metastasis in human patients with pancreatic cancer. The propensity of piggyBac for open chromatin also enabled genome-wide screening for cancer-relevant noncoding DNA, which pinpointed a Cdkn2a cis-regulatory region. Histologically, we observed different tumor subentities and discovered associated genetic events, including Fign insertions in hepatoid pancreatic cancer. Our studies demonstrate the power of genetic screening to discover cancer drivers that are difficult to identify by other approaches to cancer genome analysis, such as downstream targets of commonly mutated human cancer genes. These piggyBac resources are universally applicable in any tissue context and provide unique experimental access to the genetic complexity of cancer.

A next-generation dual-recombinase system for time- and host-specific targeting of pancreatic cancer

Genetically engineered mouse models (GEMMs) have dramatically improved our understanding of tumor evolution and therapeutic resistance. However, sequential genetic manipulation of gene expression and targeting of the host is almost impossible using conventional Cre-loxP-based models. We have developed an inducible dual-recombinase system by combining flippase-FRT (Flp-FRT) and Cre-loxP recombination technologies to improve GEMMs of pancreatic cancer. This enables investigation of multistep carcinogenesis, genetic manipulation of tumor subpopulations (such as cancer stem cells), selective targeting of the tumor microenvironment and genetic validation of therapeutic targets in autochthonous tumors on a genome-wide scale. As a proof of concept, we performed tumor cell-autonomous and nonautonomous targeting, recapitulated hallmarks of human multistep carcinogenesis, validated genetic therapy by 3-phosphoinositide-dependent protein kinase inactivation as well as cancer cell depletion and show that mast cells in the tumor microenvironment, which had been thought to be key oncogenic players, are dispensable for tumor formation.

Relationship between airway inflammation and remodeling in patients with asthma and chronic obstructive pulmonary disease

Despite a number of important differences in the pathogenesis, course and prognosis of asthma and chronic obstructive pulmonary disease (COPD), these two entities also have common features with airway inflammation being one of them. Airway remodeling is a characteristic feature of asthma, but data on the bronchial wall thickening in COPD patients are still scarce.

AIM

To assess the relation between the inflammatory cell count in the bronchoalveolar lavage fluid (BALF) and thickness of bronchial walls assessed by high resolution computed tomography (HRCT) in asthma and COPD patients.

MATERIAL AND METHODS

The study was conducted in 9 patients with mild-to-moderate asthma (M/F 4/5, mean age 35 +/- 10 years) and 11 patients with mild-to-moderate COPD (M/F 7/4, mean age 57 +/- 9 years). In all subjects lung function tests and HRCT scanning of the chest were performed. External (D) and internal (L) diameters of the airways were assessed at five selected lung levels. The lumen area (A(L)), wall area (WA), wall thickness (WT) and bronchial wall thickness (WT/D ratio) were calculated. Eight patients with asthma and 8 patients with COPD underwent fiberoptic bronchoscopy and bronchoalveolar lavage (BAL). Total and differential cell counts were assessed in the BAL fluid.

RESULTS

Mean FEV(1)% pred was 80 +/- 19%, and 73 +/- 20% in asthma and COPD patients, respectively (NS). No significant differences in the total and differential cell counts in BALF were found in patients with asthma and COPD. There were no significant differences in the airway diameter or airway wall thickness. The mean inner airway diameter was 1.4 +/- 0.3 and 1.2 +/- 0.3 mm and the mean lumen area was 1.8 +/- 0.7 and 1.6 +/- 0.7 mm(2) in asthma and COPD, respectively (NS). Negative correlations between the eosinophil count in BALF and inner airway diameter (r=-0.7, P<0.05) and lumen area (r=-0.7, P<0.05) were found in asthmatics. There was no significant relationship between the BALF cell count and airway wall thickness in COPD patients. -

CONCLUSIONS

In mild-to-moderate asthma and COPD the airway diameter and thickness are similar. In asthmatics, the airway diameter might be associated with eosinophil count in BAL fluid.

Relationship between airway wall thickness assessed by high-resolution computed tomography and lung function in patients with asthma and chronic obstructive pulmonary disease

Airway remodeling in asthma and chronic obstructive pulmonary disease (COPD) results in thickening of bronchial walls and may affect lung function. In the present study we set out to evaluate the relationship between small airway wall thickness and the lung function parameters in patients with asthma and COPD. The study was performed in 10 patients with asthma (4M/6F, the mean age 37+/-13 yr) and 12 patients with COPD (7M/5F, the mean age 57+/-9 yr) with stable, mild to moderate disease. The study group characteristics were based on clinical assessment and lung function testing (spirometry, body plethysmography, methacholine challenge test). All patients underwent chest high resolution computerized tomography with small bronchi (external diameter 1-5 mm) cross section measurements at five selected lung levels. The following parameters were measured in end-inspiratory scans: external (D) and internal (L) diameters, wall area (WA), percentage of the wall area (WA%), wall thickness (WT), and WT/D ratio (BWT). We found no significant correlations between airway wall thickness and spirometric parameters in either group. In the asthma group, the relationships between WA% and BWT, on the one side, and postbronchodilator residual volume, on the other, were noted (r=0.72; P<0.05 and r=0.72; P<0.05, respectively). In the COPD group, WA% related with airway resistance (r=0.72; P<0.05). The correlations between WA% and PC(20) (r=-0.61; P<0.05) and BWT and PC(20) (r=-0.72; P<0.05) were found in the COPD group. There was also a relationship between WA% and airway resistance (Raw) (r=0.72; P<0.05) and BWT and Raw (r=0.45; P=0.1). The number of pack-years correlated with WA and WT in COPD patients. In conclusion, the study shows that the thickening of airway wall in asthma is reflected by an increase in the indices of air trapping and in COPD this thickening results in a higher airway resistance and responsiveness. In COPD, the thickening of airway wall also is related to exposure to tobacco smoke.

[Studies on impaired angiogenesis activity of the leucocytes in patients with oral candidiasis]

The preliminary characteristics is reported of the cells causing active suppression leading to a decrease of the angiogenesis activity of leucocytes isolated from patients with oral candidiasis. The effect of three immunomodulators on this suppression was studied.

Modulatory effect of sera from scleroderma patients on lymphocyte-induced angiogenesis. II. Effector cells for the enhancing effect of acroscleroderma patients' sera

In our previous study, using the modified lymphocyte-induced angiogenesis assay, we found that incubation of normal human peripheral blood mononuclear cells (PBMCs) with sera from patients with acroscleroderma, but not with diffuse scleroderma, markedly enhanced their angiogenic capability. The results of the present work suggest that this enhancement is mediated by lymphocytes bearing receptors for the Fc portion of IgG and belonging mainly to the CD4+ T-cell subset.