Abstract PR03: Mutant p53 promotes adenocarcinoma in pancreatic ductal cells

Background: The “cell of origin” for pancreatic “ductal” neoplasia remains uncertain. Selective activation of Kras in the acinar cell compartment robustly generates mPanIN lesions, while similar activation in pancreatic ductal epithelial cells produces minimal change. These differences are notable considering in human tumorigenesis, mutational oncogene activation is postulated to occur in either single cells or small numbers of cells, followed by clonal expansion and tumor initiation. We have interrogated the comparative ability of adult pancreatic acinar and duct cells to respond to oncogenic Kras using Hnf1b:CreERT2 and Mist1:CreERT2 mice, and applied comprehensive bioinformatics analysis to identify mechanisms of duct cell-specific Kras resistance.

Hypothesis and Methods: We hypothesized that duct cell-specific changes in gene expression would mediate the relative resistance of ductal epithelial cells to Kras-mediated transformation. To identify these changes, we studied the initiation and progression of pancreatic cancer with unprecedented temporal and spatial resolution. Our approach allows for the direct visualization and FACS-based isolation of specific cell populations in which oncogenic Kras has been activated. We have activated KrasG12D and a membrane-tethered GFP in a number of adult pancreatic cell types including the acinar, ductal and centroacinar cells. Using FACS-based isolation and visualization, we have generated whole transcriptome signatures of how the different cell types respond to Kras over time. Our comprehensive bioinformatic approach involves the identification of genes that are increased or decreased at different time points after the induction of oncogenic Kras expression.

Results: Kras activation in the adult acinar cells resulted in brisk PanIN formation, while no evidence of pancreatic neoplasia was observed for up to 6 months following isolated Kras activation in Hnf1b+ duct cells. By comparing gene expression changes occurring following Kras activation in acinar vs. duct cells, we identified a panel of candidate duct cell-specific Kras resistance genes. These included Bcl-2, p21, Stk3, Plkha1, Slc9a9 and Pdcd10. Identification of upregulated Bcl-2 and p21 expression following Kras activation in duct cells, but not acinar cells, suggested involvement of the p53 pathway as a cell type-specific suppressor of pancreatic neoplasia. We recently published that biallelic expression of mutant p53R172H in cooperation with KrasG12D led to the development of pancreatic cancer from ductal cells. We are now investigating both autocrine and paracrine signaling mechanisms of mutant p53 oncogenic transformation in human derived ductal epithelial cells.

This abstract is also being presented as Poster A17

Citation Format: Kishore Polireddy, Audrey Hendley, Melissa A. Pruski, Kelly Lafaro, Mamoun Younes, Anirban Maitra, Florencia McAllister, Christine A. Iacobuzio-Donahue, Wasim A. Dar, John S. Bynon, Steven D. Leach, Jennifer M. Bailey.{Authors}. Mutant p53 promotes adenocarcinoma in pancreatic ductal cells. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr PR03.

Macrophage Ontogeny Underlies Differences in Tumor-Specific Education in Brain Malignancies

Extensive transcriptional and ontogenetic diversity exists among normal tissue-resident macrophages, with unique transcriptional profiles endowing the cells with tissue-specific functions. However, it is unknown whether the origins of different macrophage populations affect their roles in malignancy. Given potential artifacts associated with irradiation-based lineage tracing, it remains unclear if bone-marrow-derived macrophages (BMDMs) are present in tumors of the brain, a tissue with no homeostatic involvement of BMDMs. Here, we employed multiple models of murine brain malignancy and genetic lineage tracing to demonstrate that BMDMs are abundant in primary and metastatic brain tumors. Our data indicate that distinct transcriptional networks in brain-resident microglia and recruited BMDMs are associated with tumor-mediated education yet are also influenced by chromatin landscapes established before tumor initiation. Furthermore, we demonstrate that microglia specifically repress Itga4 (CD49D), enabling its utility as a discriminatory marker between microglia and BMDMs in primary and metastatic disease in mouse and human.

Mutant p53 Together with TGFβ Signaling Influence Organ-Specific Hematogenous Colonization Patterns of Pancreatic Cancer

Purpose: TP53 and the TGFβ pathway are major mediators of pancreatic cancer metastasis. The mechanisms by which they cause hematogenous metastasis have not been fully explored.Experimental Design:KPC (LSL-KRAS^G12D/+;LSL-Trp53^R172H/+; Ptf1a^Cre/+) mice were generated, and the frequency and morphology of organ-specific hematogenous metastases compared with that seen in KPTC and KTC littermates (Tgfbr2^+/-). Key findings were validated in primary cells from each genotype and samples of human pancreatic cancer liver metastases.Results: The frequency of hematogenous metastasis in KPTC mice was significantly lower than for KPC mice (41% vs. 68%, P < 0.05), largely due to a reduction in liver metastases. No differences were found between KPC and KPTC lung metastases, whereas liver metastases in KPTC mice showed a profound extravasation deficiency characterized by sinusoidal growth and lack of desmoplastic stroma. Analogous findings were confirmed in liver samples from patients indicating their clinical relevance. Portal vein colonization as a direct mode of access to the liver was observed in both mice and humans. Secretome analyses of KPC cells revealed an abundance of secreted prometastatic mediators including Col6A1 and Lcn2 that promoted early steps of metastatic colonization. These mediators were overexpressed in primary tumors but not metastases, suggesting that the ability to colonize is, in part, developed within the primary site, a phenomenon we refer to as the "Cinderella effect."Conclusions: These findings establish a novel paradigm for understanding pancreatic cancer metastasis and the observed clinical latencies of liver versus lung metastases specifically. Clin Cancer Res; 23(6); 1607-20. ©2016 AACR.

Metastatic progression is associated with dynamic changes in the local microenvironment

Most cancer-associated deaths result from metastasis. However, it remains unknown whether the size, microenvironment or other features of a metastatic lesion dictate its behaviour or determine the efficacy of chemotherapy in the adjuvant (micrometastatic) setting. Here we delineate the natural history of metastasis in an autochthonous model of pancreatic ductal adenocarcinoma (PDAC), using lineage tracing to examine the evolution of disseminated cancer cells and their associated microenvironment. With increasing size, lesions shift from mesenchymal to epithelial histology, become hypovascular and accumulate a desmoplastic stroma, ultimately recapitulating the primary tumours from which they arose. Moreover, treatment with gemcitabine and nab-paclitaxel significantly reduces the overall number of metastases by inducing cell death in lesions of all sizes, challenging the paradigm that PDAC stroma imposes a critical barrier to drug delivery. These results illuminate the cellular dynamics of metastatic progression and suggest that adjuvant chemotherapy affords a survival benefit by directly targeting micrometastases.

Pancreatic cancer biology and genetics from an evolutionary perspective

Cancer is an evolutionary disease, containing the hallmarks of an asexually reproducing unicellular organism subject to evolutionary paradigms. Pancreatic ductal adenocarcinoma (hereafter referred to as pancreatic cancer) is a particularly robust example of this phenomenon. Genomic features indicate that pancreatic cancer cells are selected for fitness advantages when encountering the geographic and resource-depleted constraints of the microenvironment. Phenotypic adaptations to these pressures help disseminated cells to survive in secondary sites, a major clinical problem for patients with this disease. In this Review we gather the wide-ranging aspects of pancreatic cancer research into a single concept rooted in Darwinian evolution, with the goal of identifying novel insights and opportunities for study.

ETS-Transcription Factor ETV1 Regulates Stromal Expansion and Metastasis in Pancreatic Cancer

BACKGROUND & AIMS

The ETS-transcription factor ETV1 is involved in epithelial-mesenchymal transition during pancreatic development and is induced in mouse pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDAC). We investigated the function of ETV1 in stromal expansion of PDAC and metastasis, as well as its effects on a novel downstream target Sparc, which encodes a matricellular protein found in PDAC stroma that has been associated with invasiveness, metastasis and poor patient outcomes.

METHODS

Pancreatic ductal cells were isolated from Pdx1Cre;Kras(G12D/+) mice (PanIN), Pdx1Cre;Kras(G12D/+);p53(fl/+) and Pdx1Cre;Kras(G12D/+);p53(fl/+);Rosa26(YFP) mice (PDAC), and Pdx1Cre;Kras(G12D/+);p53(fl/+);Sparc(-/-) mice. Cells were grown in 3-dimensional organoid culture to analyze morphology, proliferation, and invasion. Human PanIN and PDAC tissues were evaluated for ETV1 expression. Orthotopic pancreatic transplants of ETV1-overexpressing PDAC and respective control cells were performed.

RESULTS

ETV1 expression was significantly increased in human PanINs and, even more so, in primary and metastatic PDAC. Analyses of mouse orthotopic xenografts revealed that ETV1 induced significantly larger primary tumors than controls, with significantly increased stromal expansion, ascites and metastases. In 3-dimensional organoids, ETV1 disrupted cyst architecture, induced EMT, and increased invasive capacity. Furthermore, we identified Sparc as a novel functional gene target of Etv1 by luciferase assays, and SPARC and ETV1 proteins co-localized in vivo. Disruption of Sparc abrogates the phenotype of stromal expansion and metastasis found with ETV1 overexpression in vivo. We identified hyaluronan synthase 2 (Has2) as another novel downstream factor of Etv1; that may mediate ETV1's significant expansion of hyaluronic acid in PDAC stroma. Conversely, disruption of Etv1 in PDAC mice (Pdx1Cre;Kras(G12D/+);p53(fl/+);Rosa26(YFP);Cre;Etv1(fl/fl)) reduced levels of SPARC and hyaluronic acid in the stroma.

CONCLUSIONS

ETV1 is critical in the desmoplastic stromal expansion and metastatic progression of pancreatic cancer in mice, mediated functionally in part through Sparc and Has2.

Genomic instability in pancreatic adenocarcinoma: a new step towards precision medicine and novel therapeutic approaches

Pancreatic cancer is one of the most challenging cancers. Whole genome sequencing studies have been conducted to elucidate the underlying fundamentals underscoring disease behavior. Studies have identified a subgroup of pancreatic cancer patients with distinct molecular and clinical features. Genetic fingerprinting of these tumors is consistent with an unstable genome and defective DNA repair pathways, which creates unique susceptibility to agents inducing DNA damage. BRCA1/2 mutations, both germline and somatic, which lead to impaired DNA repair, are found to be important biomarkers of genomic instability as well as of response to DNA damaging agents. Recent studies have elucidated that PARP inhibitors and platinum agents may be effective to induce tumor regression in solid tumors bearing an unstable genome including pancreatic cancer. In this review we discuss the characteristics of genomic instability in pancreatic cancer along with its clinical implications and the utility of DNA targeting agents particularly PARP inhibitors as a novel treatment approach.

Abstract 2374: Reconstructing the evolutionary history of metastatic cancers

The evolution of metastases is responsible for 90% of cancer-related deaths. Genome wide sequencing and phylogenomic methods enable the reconstruction of the evolutionary history of a patient's cancer at unprecedented depth. However, due to a lack of samples from multiple spatially-distinct metastases from untreated patients and a lack of phylogenomic tools applicable to noisy and impure sequencing samples, the evolutionary rules governing metastatic spread have remained poorly understood.

We performed whole-genome sequencing (coverage: median 51x) as well as deep targeted sequencing (coverage: median 347x) on 21 samples from multiple regions of the primary tumor and many distinct liver and lung metastases of two treatment-naïve pancreatic ductal adenocarcinoma patients. We developed a tool, called Treeomics, that leverages computational and statistical advances to reconstruct the phylogeny of a cancer with commonly available sequencing technologies. Treeomics employs a uniquely-designed Bayesian inference model to account for error-prone sequencing and varying low neoplastic cell content (estimated purities 16-44%) to calculate the probability that a specific variant is present or absent in each sequenced lesion. Based on Mixed Integer Linear Programming, a mathematically guaranteed optimal evolutionary tree is produced.

We obtained robust phylogenies consistent with the biological processes underlying cancer evolution. The reconstructed phylogenies show that advanced cancer cells of related subclones were equally capable of seeding lung and liver metastases. Treeomics identified sequencing and biological artifacts such as those resulting from insufficient coverage or loss of heterozygosity; almost 7% of the variants were misclassified by conventional methods. Among the identified false-negatives was the common clonal driver mutation in KRAS within a region that has low sequencing read alignability and a significantly reduced coverage. Such artifacts can skew phylogenies by creating illusory tumor heterogeneity among distinct samples. Additionally, we reanalyzed publicly available data from ovarian, prostate and skin cancers. We further illuminated evolutionary relationships among some samples in a conclusive fashion and show that classical distance-based phylogenetic methods can produce evolutionarily implausible results. Treeomics avoids these common pitfalls and infers robust phylogenies confirmed by high bootstrapping values.

The new approach described here efficiently reconstructs the evolutionary history of metastases, detects potential artifacts in noisy high-throughput sequencing data, and finds subclones of distinct origin. These phylogenies shed new light on seeding patterns and metastatic progression, which has significant implications for clinical decision making and may provide predictive value for a patient's prognosis.

Citation Format: Johannes G. Reiter, Alvin P. Makohon-Moore, Jeffrey M. Gerold, Ivana Bozic, Krishnendu Chatterjee, Christine A. Iacobuzio-Donahue, Bert Vogelstein, Martin A. Nowak. Reconstructing the evolutionary history of metastatic cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2374.

Genotype tunes pancreatic ductal adenocarcinoma tissue tension to induce matricellular fibrosis and tumor progression

Fibrosis compromises pancreatic ductal carcinoma (PDAC) treatment and contributes to patient mortality, yet antistromal therapies are controversial. We found that human PDACs with impaired epithelial transforming growth factor-β (TGF-β) signaling have high epithelial STAT3 activity and develop stiff, matricellular-enriched fibrosis associated with high epithelial tension and shorter patient survival. In several KRAS-driven mouse models, both the loss of TGF-β signaling and elevated β1-integrin mechanosignaling engaged a positive feedback loop whereby STAT3 signaling promotes tumor progression by increasing matricellular fibrosis and tissue tension. In contrast, epithelial STAT3 ablation attenuated tumor progression by reducing the stromal stiffening and epithelial contractility induced by loss of TGF-β signaling. In PDAC patient biopsies, higher matricellular protein and activated STAT3 were associated with SMAD4 mutation and shorter survival. The findings implicate epithelial tension and matricellular fibrosis in the aggressiveness of SMAD4 mutant pancreatic tumors and highlight STAT3 and mechanics as key drivers of this phenotype.

p120 Catenin Suppresses Basal Epithelial Cell Extrusion in Invasive Pancreatic Neoplasia

Aberrant regulation of cellular extrusion can promote invasion and metastasis. Here, we identify molecular requirements for early cellular invasion using a premalignant mouse model of pancreatic cancer with conditional knockout of p120 catenin (Ctnnd1). Mice with biallelic loss of p120 catenin progressively develop high-grade pancreatic intraepithelial neoplasia (PanIN) lesions and neoplasia accompanied by prominent acute and chronic inflammatory processes, which is mediated, in part, through NF-κB signaling. Loss of p120 catenin in the context of oncogenic Kras also promotes remarkable apical and basal epithelial cell extrusion. Abundant single epithelial cells exit PanIN epithelium basally, retain epithelial morphology, survive, and display features of malignancy. Similar extrusion defects are observed following p120 catenin knockdown in vitro, and these effects are completely abrogated by the activation of S1P/S1pr2 signaling. In the context of oncogenic Kras, p120 catenin loss significantly reduces expression of genes mediating S1P/S1pr2 signaling in vivo and in vitro, and this effect is mediated at least, in part, through activation of NF-κB. These results provide insight into mechanisms controlling early events in the metastatic process and suggest that p120 catenin and S1P/S1pr2 signaling enhance cancer progression by regulating epithelial cell invasion. Cancer Res; 76(11); 3351-63. ©2016 AACR.

Genomic analyses identify molecular subtypes of pancreatic cancer

Integrated genomic analysis of 456 pancreatic ductal adenocarcinomas identified 32 recurrently mutated genes that aggregate into 10 pathways: KRAS, TGF-β, WNT, NOTCH, ROBO/SLIT signalling, G1/S transition, SWI-SNF, chromatin modification, DNA repair and RNA processing. Expression analysis defined 4 subtypes: (1) squamous; (2) pancreatic progenitor; (3) immunogenic; and (4) aberrantly differentiated endocrine exocrine (ADEX) that correlate with histopathological characteristics. Squamous tumours are enriched for TP53 and KDM6A mutations, upregulation of the TP63∆N transcriptional network, hypermethylation of pancreatic endodermal cell-fate determining genes and have a poor prognosis. Pancreatic progenitor tumours preferentially express genes involved in early pancreatic development (FOXA2/3, PDX1 and MNX1). ADEX tumours displayed upregulation of genes that regulate networks involved in KRAS activation, exocrine (NR5A2 and RBPJL), and endocrine differentiation (NEUROD1 and NKX2-2). Immunogenic tumours contained upregulated immune networks including pathways involved in acquired immune suppression. These data infer differences in the molecular evolution of pancreatic cancer subtypes and identify opportunities for therapeutic development.

TGF-β Tumor Suppression through a Lethal EMT

TGF-β signaling can be pro-tumorigenic or tumor suppressive. We investigated this duality in pancreatic ductal adenocarcinoma (PDA), which, with other gastrointestinal cancers, exhibits frequent inactivation of the TGF-β mediator Smad4. We show that TGF-β induces an epithelial-mesenchymal transition (EMT), generally considered a pro-tumorigenic event. However, in TGF-β-sensitive PDA cells, EMT becomes lethal by converting TGF-β-induced Sox4 from an enforcer of tumorigenesis into a promoter of apoptosis. This is the result of an EMT-linked remodeling of the cellular transcription factor landscape, including the repression of the gastrointestinal lineage-master regulator Klf5. Klf5 cooperates with Sox4 in oncogenesis and prevents Sox4-induced apoptosis. Smad4 is required for EMT but dispensable for Sox4 induction by TGF-β. TGF-β-induced Sox4 is thus geared to bolster progenitor identity, whereas simultaneous Smad4-dependent EMT strips Sox4 of an essential partner in oncogenesis. Our work demonstrates that TGF-β tumor suppression functions through an EMT-mediated disruption of a lineage-specific transcriptional network.

Genomic landscape of pancreatic adenocarcinoma: Does age matter?

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Background: State-of the art genomic analyses of pancreatic adenocarcinoma (PDAC) has yielded insights into signaling pathways underlying carcinogenesis. PDAC is characterized by substantial genomic heterogeneity. We aimed to determine if early-onset PDAC ( ≤ 55 yrs) displays a distinctive molecular landscape from average-age onset PDAC ( ≥ 70 yrs). Methods: Three distinct datasets of PDAC in age groups ≤ 55 and ≥ 70 years old were analyzed. In the first, patients undergoing treatment at MSKCC were consented for MSK-IMPACT (Integrated Mutation Profiling of Actionable Cancer Targets) next generation sequencing. The second cohort analyzed was The Cancer Genome Atlas (TCGA) dataset for differences in somatic mutations, gene expression and protein expression. The third dataset was the Australian cohort of PDAC (Waddell et al, Nature, 2015). Clinical data were correlated with genomic analyses. Results: One hundred and eighty-three samples were analyzed, yielding N = 56 patients (pts) aged ≤ 55 years and N = 127 pts aged ≥ 70 years. Several genes known to be associated with carcinogenesis differed in mutation frequency across age groups: SMAD4, MYC and PIK3CA displayed higher mutation rates in younger patients (p < 0.05, table below). Comprehensive analysis by cellular pathways indicated that the PI3Kpathway is further altered in the younger population. Protein expression had different patterns in younger versus older patients. Smoking was more prevalent in the early-onset group in all three cohorts (59% vs. 47%). Survival outcomes revealed no differences between the age groups. Conclusions: This exploratory analysis suggests that there may be somatic gene alterations within the population of early onset PDAC patients that involve unique cellular pathways compared with average onset PDAC. Former studies imply these cellular pathways may play a role in smoking-related PDAC carcinogenesis. Larger genomic datasets are warranted for future analysis to support this observation. [Table: see text]

p53 mutations cooperate with oncogenic Kras to promote adenocarcinoma from pancreatic ductal cells

Pancreatic cancer is one of the most lethal malignancies, with virtually all patients eventually succumbing to their disease. Mutations in p53 have been documented in >50% of pancreatic cancers. Owing to the high incidence of p53 mutations in PanIN 3 lesions and pancreatic tumors, we interrogated the comparative ability of adult pancreatic acinar and ductal cells to respond to oncogenic Kras and mutant Tp53(R172H) using Hnf1b:CreER(T2) and Mist1:CreER(T2) mice. These studies involved co-activation of a membrane-tethered GFP lineage label, allowing for direct visualization and isolation of cells undergoing Kras and mutant p53 activation. Kras activation in Mist1(+) adult acinar cells resulted in brisk PanIN formation, whereas no evidence of pancreatic neoplasia was observed for up to 6 months following Kras activation in Hnf1beta(+) adult ductal cells. In contrast to the lack of response to oncogenic Kras alone, simultaneous activation of Kras and mutant p53 in adult ductal epithelium generated invasive PDAC in 75% of mice as early as 2.5 months after tamoxifen administration. These data demonstrate that pancreatic ductal cells, whereas exhibiting relative resistance to oncogenic Kras alone, can serve as an effective cell of origin for pancreatic ductal adenocarcinoma in the setting of gain-of-function mutations in p53.

Molecular signature of pancreatic adenocarcinoma: an insight from genotype to phenotype and challenges for targeted therapy

INTRODUCTION

Pancreatic adenocarcinoma remains one of the most clinically challenging cancers despite an in-depth characterization of the molecular underpinnings and biology of this disease. Recent whole-genome-wide studies have elucidated the diverse and complex genetic alterations which generate a unique oncogenic signature for an individual pancreatic cancer patient and which may explain diverse disease behavior in a clinical setting.

AREAS COVERED

In this review article, we discuss the key oncogenic pathways of pancreatic cancer including RAS-MAPK, PI3KCA and TGF-β signaling, as well as the impact of these pathways on the disease behavior and their potential targetability. The role of tumor suppressors particularly BRCA1 and BRCA2 genes and their role in pancreatic cancer treatment are elaborated upon. We further review recent genomic studies and their impact on future pancreatic cancer treatment.

EXPERT OPINION

Targeted therapies inhibiting pro-survival pathways have limited impact on pancreatic cancer outcomes. Activation of pro-apoptotic pathways along with suppression of cancer-stem-related pathways may reverse treatment resistance in pancreatic cancer. While targeted therapy or a 'precision medicine' approach in pancreatic adenocarcinoma remains an elusive challenge for the majority of patients, there is a real sense of optimism that the strides made in understanding the molecular underpinnings of this disease will translate into improved outcomes.

Widespread somatic L1 retrotransposition occurs early during gastrointestinal cancer evolution

Somatic L1 retrotransposition events have been shown to occur in epithelial cancers. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds, and many were present in multiple tumor sections, implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth.

Semaphorin 3D autocrine signaling mediates the metastatic role of annexin A2 in pancreatic cancer

Most patients with pancreatic ductal adenocarcinoma (PDA) present with metastatic disease at the time of diagnosis or will recur with metastases after surgical treatment. Semaphorin-plexin signaling mediates the migration of neuronal axons during development and of blood vessels during angiogenesis. The expression of the gene encoding semaphorin 3D (Sema3D) is increased in PDA tumors, and the presence of antibodies against the pleiotropic protein annexin A2 (AnxA2) in the sera of some patients after surgical resection of PDA is associated with longer recurrence-free survival. By knocking out AnxA2 in a transgenic mouse model of PDA (KPC) that recapitulates the progression of human PDA from premalignancy to metastatic disease, we found that AnxA2 promoted metastases in vivo. The expression of AnxA2 promoted the secretion of Sema3D from PDA cells, which coimmunoprecipitated with the co-receptor plexin D1 (PlxnD1) on PDA cells. Mouse PDA cells in which SEMA3D was knocked down or ANXA2-null PDA cells exhibited decreased invasive and metastatic potential in culture and in mice. However, restoring Sema3D in AnxA2-null cells did not entirely rescue metastatic behavior in culture and in vivo, suggesting that AnxA2 mediates additional prometastatic mechanisms. Patients with primary PDA tumors that have abundant Sema3D have widely metastatic disease and decreased survival compared to patients with tumors that have relatively low Sema3D abundance. Thus, AnxA2 and Sema3D may be new therapeutic targets and prognostic markers of metastatic PDA.

Transflip mutations produce deletions in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is driven by the inactivation of the tumor suppressor genes (TSGs), CDKN2A (P16) and SMAD4 (DPC4), commonly by homozygous deletions (HDs). Using a combination of high density single-nucleotide polymorphism (SNP) microarray and whole genome sequencing (WGS), we fine-mapped novel breakpoints surrounding deletions of CDKN2A and SMAD4 and characterized them by their underlying structural variants (SVs). Only one third of CDKN2A and SMAD4 deletions (6 of 18) were simple interstitial deletions, rather, the majority of deletions were caused by complex rearrangements, specifically, a translocation on one side of the TSG in combination with an inversion on the other side. We designate these as "TransFlip" mutations. Characteristics of TransFlip mutations are: (1) a propensity to target the TSGs CDKN2A and SMAD4 (P < 0.005), (2) not present in the germline of the examined samples, (3) non-recurrent breakpoints, (4) relatively small (47 bp to 3.4 kb) inversions, (5) inversions can be either telomeric or centromeric to the TSG, and (6) non-reciprocal, and non-recurrent translocations. TransFlip mutations are novel complex genomic rearrangements with unique breakpoint signatures in pancreatic cancer. We hypothesize that they are a common but poorly understood mechanism of TSG inactivation in human cancer. © 2015 Wiley Periodicals, Inc.

Whole genomes redefine the mutational landscape of pancreatic cancer

Pancreatic cancer remains one of the most lethal of malignancies and a major health burden. We performed whole-genome sequencing and copy number variation (CNV) analysis of 100 pancreatic ductal adenocarcinomas (PDACs). Chromosomal rearrangements leading to gene disruption were prevalent, affecting genes known to be important in pancreatic cancer (TP53, SMAD4, CDKN2A, ARID1A and ROBO2) and new candidate drivers of pancreatic carcinogenesis (KDM6A and PREX2). Patterns of structural variation (variation in chromosomal structure) classified PDACs into 4 subtypes with potential clinical utility: the subtypes were termed stable, locally rearranged, scattered and unstable. A significant proportion harboured focal amplifications, many of which contained druggable oncogenes (ERBB2, MET, FGFR1, CDK6, PIK3R3 and PIK3CA), but at low individual patient prevalence. Genomic instability co-segregated with inactivation of DNA maintenance genes (BRCA1, BRCA2 or PALB2) and a mutational signature of DNA damage repair deficiency. Of 8 patients who received platinum therapy, 4 of 5 individuals with these measures of defective DNA maintenance responded.

Phase 2 multi-institutional trial evaluating gemcitabine and stereotactic body radiotherapy for patients with locally advanced unresectable pancreatic adenocarcinoma

Background

This phase 2 multi-institutional study was designed to determine whether gemcitabine (GEM) with fractionated stereotactic body radiotherapy (SBRT) results in acceptable late grade 2 to 4 gastrointestinal toxicity when compared with a prior trial of GEM with single-fraction SBRT in patients with locally advanced pancreatic cancer (LAPC).

Methods

A total of 49 patients with LAPC received up to 3 doses of GEM (1000 mg/m²) followed by a 1-week break and SBRT (33.0 gray [Gy] in 5 fractions). After SBRT, patients continued to receive GEM until disease progression or toxicity. Toxicity was assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0] and the Radiation Therapy Oncology Group radiation morbidity scoring criteria. Patients completed the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (QLQ-C30) and pancreatic cancer-specific QLQ-PAN26 module before SBRT and at 4 weeks and 4 months after SBRT.

Results

The median follow-up was 13.9 months (range, 3.9-45.2 months). The median age of the patients was 67 years and 84% had tumors of the pancreatic head. Rates of acute and late (primary endpoint) grade ≥2 gastritis, fistula, enteritis, or ulcer toxicities were 2% and 11%, respectively. QLQ-C30 global quality of life scores remained stable from baseline to after SBRT (67 at baseline, median change of 0 at both follow-ups; P>.05 for both). Patients reported a significant improvement in pancreatic pain (P = .001) 4 weeks after SBRT on the QLQ-PAN26 questionnaire. The median plasma carbohydrate antigen 19-9 (CA 19-9) level was reduced after SBRT (median time after SBRT, 4.2 weeks; 220 U/mL vs 62 U/mL [P<.001]). The median overall survival was 13.9 months (95% confidence interval, 10.2 months-16.7 months). Freedom from local disease progression at 1 year was 78%. Four patients (8%) underwent margin-negative and lymph node-negative surgical resections.

Conclusions

Fractionated SBRT with GEM results in minimal acute and late gastrointestinal toxicity. Future studies should incorporate SBRT with more aggressive multiagent chemotherapy.

To the authors' knowledge, the current study is the first prospective multi-institutional trial evaluating the role of stereotactic body radiotherapy in patients with locally advanced pancreatic cancer. The results suggest that fractionated stereotactic body radiotherapy with gemcitabine achieves favorable toxicity, quality of life, and preliminary efficacy compared with historical data.

MUC1 Promoter-Driven DTA as a Targeted Therapeutic Strategy against Pancreatic Cancer

Mucin1 (MUC1) is overexpressed in pancreatic ductal adenocarcinoma (PDA) and is associated with tumor aggressiveness, suggesting that MUC1 is a promising therapeutic target for promoter-driven diphtheria toxin A (DTA). Endogenous MUC1 transcript levels were analyzed by quantitative PCR (qPCR) in multiple PDA cells (Capan1, HPAFII, Su.86.86, Capan2, Hs766T, MiaPaCa2, and Panc1). Expression levels were correlated with luciferase activity and cell death after transfection with MUC1 promoter-driven luciferase and DTA constructs. MUC1-positive (+) cells had significantly elevated MUC1 mRNA expression compared with MUC1-negative (-) cells. Luciferase activity was significantly higher in MUC1(+) cells when transfected with MUC1 promoter-driven luciferase and MUC1(+) cells underwent enhanced cell death after transfection with a single dose of MUC1 promoter-driven DTA. IFNγ pretreatment enhanced MUC1 expression in MUC1(-) cells and induced sensitivity to MUC1-DTA therapy. Matched primary and metastatic tumor lesions from clinical specimens revealed similar MUC1 IHC labeling patterns, and a tissue microarray of human PDA biopsies revealed increased immunolabeling with a combination of MUC1 and mesothelin (MSLN) antibodies, compared with either antibody alone. Combining MUC1 with MSLN-targeted DTA enhanced drug efficacy in an in vitro model of heterogeneous PDA. These data demonstrate that MUC1 promoter-driven DTA preferentially kills MUC1-expressing PDA cells and drugs that enhance MUC1 expression sensitize PDA cells with low MUC1 expression.

IMPLICATIONS

MUC1 expression in primary and metastatic lesions provides a rationale for the development of a systemic MUC1 promoter-driven DTA therapy that may be further enhanced by combination with other promoter-driven DTA constructs.

Functional p38 MAPK identified by biomarker profiling of pancreatic cancer restrains growth through JNK inhibition and correlates with improved survival

PURPOSE

Numerous biomarkers for pancreatic cancer have been reported. We determined the extent to which such biomarkers are expressed throughout metastatic progression, including those that effectively predict biologic behavior.

EXPERIMENTAL DESIGN

Biomarker profiling was performed for 35 oncoproteins in matched primary and metastatic pancreatic cancer tissues from 36 rapid autopsy patients. Proteins of significance were validated by immunolabeling in an independent sample set, and functional studies were performed in vitro and in vivo.

RESULTS

Most biomarkers were similarly expressed or lost in expression in most samples analyzed, and the matched primary and metastases from a specific patient were most similar to each other than to other patients. However, a subset of proteins showed extensive interpatient heterogeneity, one of which was p38 MAPK. Strong positive pp38 MAPK immunolabeling was significantly correlated with improved postresection survival by multivariate analysis (median overall survival 27.9 months, P = 0.041). In pancreatic cancer cells, inhibition of functional p38 by SB202190 increased cell proliferation in vitro in both low-serum and low-oxygen conditions. High functional p38 activity in vitro corresponded to lower levels of pJNK protein expression, and p38 inhibition resulted in increased pJNK and pMKK7 by Western blot analysis. Moreover, JNK inhibition by SP600125 or MKK7 siRNA knockdown antagonized the effects of p38 inhibition by SB202190. In vivo, SP600125 significantly decreased growth rates of xenografts with high p38 activity compared with those without p38 expression.

CONCLUSIONS

Functional p38 MAPK activity contributes to overall survival through JNK signaling, thus providing a rationale for JNK inhibition in pancreatic cancer management.

Heterogeneity of pancreatic cancer metastases in a single patient revealed by quantitative proteomics

Many patients with pancreatic cancer have metastases to distant organs at the time of initial presentation. Recent studies examining the evolution of pancreatic cancer at the genetic level have shown that clonal complexity of metastatic pancreatic cancer is already initiated within primary tumors, and organ-specific metastases are derived from different subclones. However, we do not yet understand to what extent the evolution of pancreatic cancer contributes to proteomic and signaling alterations. We hypothesized that genetic heterogeneity of metastatic pancreatic cancer results in heterogeneity at the proteome level. To address this, we employed a model system in which cells isolated from three sites of metastasis (liver, lung, and peritoneum) from a single patient were compared. We used a SILAC-based accurate quantitative proteomic strategy combined with high-resolution mass spectrometry to analyze the total proteome and tyrosine phosphoproteome of each of the distal metastases. Our data revealed distinct patterns of both overall proteome expression and tyrosine kinase activities across the three different metastatic lesions. This heterogeneity was significant because it led to differential sensitivity of the neoplastic cells to small molecule inhibitors targeting various kinases and other pathways. For example, R428, a tyrosine kinase inhibitor that targets Axl receptor tyrosine kinase, was able to inhibit cells derived from lung and liver metastases much more effectively than cells from the peritoneal metastasis. Finally, we confirmed that administration of R428 in mice bearing xenografts of cells derived from the three different metastatic sites significantly diminished tumors formed from liver- and lung-metastasis-derived cell lines as compared with tumors derived from the peritoneal metastasis cell line. Overall, our data provide proof-of-principle support that personalized therapy of multiple organ metastases in a single patient should involve the administration of a combination of agents, with each agent targeted to the features of different subclones.

Long interspersed element-1 protein expression is a hallmark of many human cancers

Cancers comprise a heterogeneous group of human diseases. Unifying characteristics include unchecked abilities of tumor cells to proliferate and spread anatomically, and the presence of clonal advantageous genetic changes. However, universal and highly specific tumor markers are unknown. Herein, we report widespread long interspersed element-1 (LINE-1) repeat expression in human cancers. We show that nearly half of all human cancers are immunoreactive for a LINE-1-encoded protein. LINE-1 protein expression is a common feature of many types of high-grade malignant cancers, is rarely detected in early stages of tumorigenesis, and is absent from normal somatic tissues. Studies have shown that LINE-1 contributes to genetic changes in cancers, with somatic LINE-1 insertions seen in selected types of human cancers, particularly colon cancer. We sought to correlate this observation with expression of the LINE-1-encoded protein, open reading frame 1 protein, and found that LINE-1 open reading frame 1 protein is a surprisingly broad, yet highly tumor-specific, antigen.

dCK expression correlates with 5-fluorouracil efficacy and HuR cytoplasmic expression in pancreatic cancer: a dual-institutional follow-up with the RTOG 9704 trial

Deoxycytidine kinase (dCK) and human antigen R (HuR) have been associated with response to gemcitabine in small studies. The present study investigates the prognostic and predictive value of dCK and HuR expression levels for sensitivity to gemcitabine and 5-fluorouracil (5-FU) in a large phase III adjuvant trial with chemoradiation backbone in pancreatic ductal adenocarcinoma (PDA). The dCK and HuR expression levels were determined by immunohistochemistry on a tissue microarray of 165 resected PDAs from the Radiation Therapy Oncology Group (RTOG) 9704 trial. Association with overall survival (OS) and disease-free survival (DFS) status were analyzed using the log-rank test and the Cox proportional hazards model. Experiments with cultured PDA cells were performed to explore mechanisms linking dCK and HuR expression to drug sensitivity. dCK expression levels were associated with improved OS for all patients analyzed from RTOG 9704 (HR: 0.66, 95% CI [0.47-0.93], P = 0.015). In a subset analysis based on treatment arm, the effect was restricted to patients receiving 5-FU (HR: 0.53, 95% CI [0.33-0.85], P = 0.0078). Studies in cultured cells confirmed that dCK expression rendered cells more sensitive to 5-FU. HuR cytoplasmic expression was neither prognostic nor predictive of treatment response. Previous studies along with drug sensitivity and biochemical studies demonstrate that radiation interferes with HuR's regulatory effects on dCK, and could account for the negative findings herein based on the clinical study design (i.e., inclusion of radiation). Finally, we demonstrate that 5-FU can increase HuR function by enhancing HuR translocation from the nucleus to the cytoplasm, similar to the effect of gemcitabine in PDA cells. For the first time, in the pre-treatment tumor samples, dCK and HuR cytoplasmic expression were strongly correlated (chi-square P = 0.015). This dual-institutional follow up study, in a multi-institutional PDA randomized clinical trial, observed that dCK expression levels were prognostic and had predictive value for sensitivity to 5-FU.

CpG island methylator phenotype and its association with malignancy in sporadic duodenal adenomas

CpG island methylator phenotype (CIMP) has been found in multiple precancerous and cancerous lesions, including colorectal adenomas, colorectal cancers, and duodenal adenocarcinomas. There are no reports in the literature of a relationship between CIMP status and clinicopathologic features of sporadic duodenal adenomas. This study sought to elucidate the role of methylation in duodenal adenomas and correlate it with KRAS and BRAF mutations. CIMP+ (with more than 2 markers methylated) was seen in 33.3% of duodenal adenomas; 61% of these CIMP+ adenomas were CIMP-high (with more than 3 markers methylated). Furthermore, CIMP+ status significantly correlated with older age of patients, larger size and villous type of tumor, coexistent dysplasia and periampullary location. MLH1 methylation was seen in 11.1% of duodenal adenomas and was significantly associated with CIMP+ tumors, while p16 methylation was an infrequent event. KRAS mutations were frequent and seen in 26.3% of adenomas; however, no BRAF mutations were detected. Furthermore, CIMP-high status was associated with larger size and villous type of tumor and race (non-white). These results suggest that CIMP+ duodenal adenomas may have a higher risk for developing malignancy and may require more aggressive management and surveillance.

Association of ALDH-expressing cancer stem cells with survival in patients with resected pancreatic adenocarcinoma treated with adjuvant chemoradiation

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Background: We and others have identified aldehyde dehydrogenase (ALDH) activity as a marker of pancreatic cancer stem cells (or tumor-initiating cells). The presence of cancer stem cells (CSCs) has been associated with decreased survival and treatment resistance in pancreatic adenocarcinoma. We investigate the role of ALDH expression in predicting survival and patterns of disease recurrence in patients treated with chemoradiation (CRT) following pancreatectomy. Methods: Tissue microarrays using surgical specimens from 1998 to 2002 were stained for ALDH1 and scored as ALDH-positive or ALDH-negative by two expert pancreatic pathologists blinded to patient outcomes. Physician documentation and radiology reports were used to determine follow-up information. Time to local failure (TLF), time to distant metastases (TDM), progression-free survival (PFS), and overall survival (OS) were analyzed using SPSS software. Results: Previously we found that ALDH expression was associated with worse OS in a cohort of 269 patients with resected pancreatic adenocarcinoma (Rasheed, JNCI 2009). From this cohort, adjuvant treatment information was available for 87 patients with ALDH-negative tumors (48.6%) and 41 patients with ALDH-positive tumors (45.6%). In patients treated with adjuvant CRT, median overall survival was superior in the ALDH-negative cohort vs. the ALDH-positive cohort, 26.3 months vs. 18.2 months (p=0.011). Further, in patients treated with adjuvant CRT, ALDH-negative patients had statistically greater TLF, TDM, and PFS than their ALDH-positive counterparts (see table). On multivariate analysis, ALDH positive tumor staining (HR 1.94, p=0.004) and tumor grade (HR 1.54, p=0.041) predicted lower OS, and ALDH positive tumor staining (HR 1.83, p=0.008), tumor grade (HR 1.52, p=0.038), and tumor size >3 cm (HR 1.65, p=0.023) predicted decreased PFS. Conclusions: This study suggests that adjuvant CRT improves TLF, TDM, PFS, and OS in patients with localized pancreatic adenocarcinoma not enriched with ALDH-expressing CSCs. Laboratory studies will help elucidate the mechanisms of treatment resistance in ALDH expressing CSCs.

The association between circulating high-sensitivity C-reactive protein concentration and pathologic measures of colonic inflammation

PURPOSE

C-reactive protein (CRP), an inflammation marker, is associated with colorectal cancer (CRC) risk in some prospective studies. Whether increased CRP is indicative of colonic inflammation, a possible CRC cause, or of other sources of inflammation (e.g., adiposity), is unknown. Thus, we evaluated the association between CRP and colonic mucosal measures of inflammation.

METHODS

151 adults undergoing colonoscopy provided a blood sample and random left- and right-side colonic mucosal biopsies. Height and weight were measured, and lifestyle information was collected. High-sensitivity C-reactive protein (hsCRP) was measured by immunoturbidometric assay. A gastrointestinal pathologist evaluated biopsies for seven colonic inflammation measures. Of 119 participants with complete information, 24 had an inflammatory bowel disease (IBD) history and were analyzed separately. We calculated the number of colonic inflammation measures present in both biopsies, and separately for right and left biopsies. Adjusted geometric mean hsCRP was calculated using linear regression, overall, by demographic and lifestyle factors, and inflammation measures.

RESULTS

Most participants had ≥ 1 colonic inflammation measure (0: 21 %, 1: 39 %, ≥ 2: 40 %). Adjusted mean hsCRP did not increase with increasing number of inflammation measures (0: 1.67; 1: 1.33; ≥ 2: 1.01 mg/L; p trend = 0.21). Obese (2.03 mg/L) and overweight (1.61 mg/L) participants had higher adjusted mean hsCRP than normal-weight participants (0.62 mg/L; p trend <0.0001). Patterns were similar for participants with a history of IBD.

CONCLUSIONS

hsCRP concentration was not associated with colonic inflammation, although hsCRP increased with adiposity. The hsCRP-CRC association may be explained by residual confounding by other risk factors, such as adiposity, rather than by CRP marking colonic inflammation.

Hypersensitivities for acetaldehyde and other agents among cancer cells null for clinically relevant Fanconi anemia genes

Large-magnitude numerical distinctions (>10-fold) among drug responses of genetically contrasting cancers were crucial for guiding the development of some targeted therapies. Similar strategies brought epidemiological clues and prevention goals for genetic diseases. Such numerical guides, however, were incomplete or low magnitude for Fanconi anemia pathway (FANC) gene mutations relevant to cancer in FANC-mutation carriers (heterozygotes). We generated a four-gene FANC-null cancer panel, including the engineering of new PALB2/FANCN-null cancer cells by homologous recombination. A characteristic matching of FANCC-null, FANCG-null, BRCA2/FANCD1-null, and PALB2/FANCN-null phenotypes was confirmed by uniform tumor regression on single-dose cross-linker therapy in mice and by shared chemical hypersensitivities to various inter-strand cross-linking agents and γ-radiation in vitro. Some compounds, however, had contrasting magnitudes of sensitivity; a strikingly high (19- to 22-fold) hypersensitivity was seen among PALB2-null and BRCA2-null cells for the ethanol metabolite, acetaldehyde, associated with widespread chromosomal breakage at a concentration not producing breaks in parental cells. Because FANC-defective cancer cells can share or differ in their chemical sensitivities, patterns of selective hypersensitivity hold implications for the evolutionary understanding of this pathway. Clinical decisions for cancer-relevant prevention and management of FANC-mutation carriers could be modified by expanded studies of high-magnitude sensitivities.

Novel methylation biomarker panel for the early detection of pancreatic cancer

PURPOSE

Pancreatic cancer is the fourth leading cause of cancer deaths and there currently is no reliable modality for the early detection of this disease. Here, we identify cancer-specific promoter DNA methylation of BNC1 and ADAMTS1 as a promising biomarker detection strategy meriting investigation in pancreatic cancer.

EXPERIMENTAL DESIGN

We used a genome-wide pharmacologic transcriptome approach to identify novel cancer-specific DNA methylation alterations in pancreatic cancer cell lines. Of eight promising genes, we focused our studies on BNC1 and ADAMTS1 for further downstream analysis, including methylation and expression. We used a nanoparticle-enabled methylation on beads (MOB) technology to detect early-stage pancreatic cancers by analyzing DNA methylation in patient serum.

RESULTS

We identified two novel genes, BNC1 (92%) and ADAMTS1 (68%), that showed a high frequency of methylation in pancreatic cancers (n = 143), up to 100% in PanIN-3 and 97% in stage I invasive cancers. Using the nanoparticle-enabled MOB technology, these alterations could be detected in serum samples (n = 42) from patients with pancreatic cancer, with a sensitivity for BNC1 of 79% [95% confidence interval (CI), 66%-91%] and for ADAMTS1 of 48% (95% CI, 33%-63%), whereas specificity was 89% for BNC1 (95% CI, 76%-100%) and 92% for ADAMTS1 (95% CI, 82%-100%). Overall sensitivity using both markers is 81% (95% CI, 69%-93%) and specificity is 85% (95% CI, 71%-99%).

CONCLUSIONS

Promoter DNA methylation of BNC1 and ADAMTS1 is a potential biomarker to detect early-stage pancreatic cancers. Assaying the promoter methylation status of these genes in circulating DNA from serum is a promising strategy for early detection of pancreatic cancer and has the potential to improve mortality from this disease.

Resection of borderline resectable pancreatic cancer after neoadjuvant chemoradiation does not depend on improved radiographic appearance of tumor-vessel relationships

OBJECTIVE

Neoadjuvant therapy increases rates of margin-negative resection of borderline resectable pancreatic ductal adenocarcinoma (BL-PDAC). Criteria for BL-PDAC resection following neoadjuvant chemotherapy and radiation therapy (NCRT) have not been clearly defined.

METHODS

Fifty consecutive patients with BL-PDAC who received NCRT from 2007 to 2012 were identified. Computed tomography (CT) scans pre- and post-treatment were centrally reviewed.

RESULTS

Twenty-nine patients (58 %) underwent resection following NCRT, while 21 (42 %) remained unresected. Patients selected for and successfully undergoing resection were more likely to have better performance status and absence of the following features on pre- and post-treatment CT: superior mesenteric vein/portal vein encasement, superior mesenteric artery involvement, tumor involvement of two or more vessels, and questionable/overt metastases (all p <0.05). Tumor volume and degree of tumor-vessel involvement did not significantly change in both groups after NCRT (all p > 0.05). The median overall survival was 22.9 months in resected versus 13.0 months in unresected patients (p < 0.001). Of patients undergoing resection, 93 % were margin-negative, 72 % were node-negative, and 54 % demonstrated moderate pathologic response to NCRT.

CONCLUSION

Apparent radiographic extent of vascular involvement does not change significantly after NCRT. Patients without metastatic disease should be chosen for surgical exploration based on adequate performance status and lack of disease progression.

Is successful resection following neoadjuvant radiation therapy for borderline resectable pancreatic cancer dependent on improved tumor-vessel relationships?

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Background: Margin-negative (R0) surgical resection is the only potentially curative therapy for pancreatic cancer. For patients deemed borderline resectable (BL), neoadjuvant chemoradiotherapy (NRT) increases the likelihood of subsequent R0 resection and improves overall survival. Prognostic factors for achieving resection following NRT have yet to be clearly identified. Methods: Fifty consecutive patients with BL-PDAC evaluated by a multidisciplinary tumor board who received NRT from 2007-2012 were retrospectively identified. Computed tomography (CT) scans pre- and post-radiation and surgical specimens were centrally reviewed. Results: 29 patients underwent resection following NCRT, while 21 remained unresectable. Between the two groups, age, gender, mean RT dose, and proportion of pancreatic head tumors were not significantly different. Smaller tumor volume and lack of the following factors was associated with selection for resection: superior mesenteric/portal vein encasement (p=0.01), superior mesenteric artery involvement (p=0.02), ascites (p=0.01), and questionable/overt metastases (p=0.01). Notably, celiac artery involvement/encasement, common hepatic artery encasement, and percentage change in tumor volume were not significant predictors of resection (all p>>0.05). Interestingly, tumor volume and degree of individual vessel involvement did not significantly change from scans before and after NCRT (all p>>0.05). Median OS was 22.9 vs.13.0 months in resected and unresected patients, respectively (p<0.001). Of resected patients, 93% had negative margins, 28% had positive nodes, 27% demonstrated <10% viable tumor, and 12% had pathologic complete response at surgery. Dpc4 expression was retained in 68% of specimens with viable tumor. Conclusions: Although the apparent radiographic extent of vascular involvement does not change significantly after NRT, subsequent R0 resection rates are high, nodal involvement is low, and outcomes are similar to resected patients who receive adjuvant therapy. Resection attempts should not be deferred solely based on lack of improvement in tumor-vessel interactions.

FAM190A deficiency creates a cell division defect

Like the p16, SMAD4, and RB1 genes, FAM190A (alias CCSER1) lies at a consensus site of homogeneous genomic deletions in human cancer. FAM190A transcripts in 40% of cancers also contain in-frame deletions of evolutionarily conserved exons. Its gene function was unknown. We found an internal deletion of the FAM190A gene in a pancreatic cancer having prominent focal multinuclearity. The experimental knockdown of FAM190A expression by shRNA caused focal cytokinesis defects, multipolar mitosis, and multinuclearity as observed in time-lapse microscopy. FAM190A was localized to the γ-tubulin ring complex of early mitosis and to the midbody in late cytokinesis by immunofluorescence assay and was present in the nuclear fraction of unsynchronized cells by immunoblot. FAM190A interacted with EXOC1 and Ndel1, which function in cytoskeletal organization and the cell division cycle. Levels of FAM190A protein peaked 12 hours after release from thymidine block, corresponding to M-phase. Slower-migrating phosphorylated forms accumulated toward M-phase and disappeared after release from a mitotic block and before cytokinesis. Studies of FAM190A alterations may provide mechanistic insights into mitotic dysregulation and multinuclearity in cancer. We propose that FAM190A is a regulator or structural component required for normal mitosis and that both the rare truncating mutations and common in-frame deletion alteration of FAM190A may contribute to the chromosomal instability of cancer.

Abstract 3580: Acetaldehyde and drug hypersensitivities of Fanconi anemia defects: Implications for cancer initiation, prevention, and therapy

Studies of cells harboring Fanconi anemia (FA) pathway defects have aided clinical understanding of inherited cancer risks and therapeutic strategies. Here, we observed a novel and large (27X) hypersensitivity of BRCA2- and PALB2-null genotypes to the epidemiologically important ethanol metabolite, acetaldehyde. This prominent acetaldehyde sensitivity may hold evolutionary and clinical significance. Interrogation of a novel panel of cells engineered to be null for various FA genes also revealed two classes of chemical hypersensitivities: the shared and divergent phenotypes. Prominent chemical hypersensitivities to various interstrand crosslinking (ICL) agents in vitro (melphalan, mitomycin C, and cisplatin), to γ-radiation in vitro, and to mitomycin C in vivo were essentially similar among the tested genotypes. A large divergence of responsiveness existed, however, between the cell lines when using the PARP inhibitor KU0058948, the topoisomerase II inhibitor etoposide, and acetaldehyde. These results indicate that, toward some agents, not all FA defects are necessarily equivalent; this divergence among phenotypes may dissect functions differing among FA genes and may presage differing clinical and epidemiological implications. We additionally present the first engineered PALB2-null human cancer cells. The results suggest new applications in cancer epidemiology, prevention, and targeted therapy.

Citation Format: Soma Ghosh, Surojit Sur, Sashidhar R. Yerram, Carlo Rago, Anil K. Bhunia, M. Zulfiquer Hossain, Bogdan C. Paun, Yunzhao R. Ren, Christine A. Iacobuzio-Donahue, Nilofer A. Azad, Scott E. Kern. Acetaldehyde and drug hypersensitivities of Fanconi anemia defects: Implications for cancer initiation, prevention, and therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3580. doi:10.1158/1538-7445.AM2013-3580

Abstract 4006: Smad6 upregulation provides an alternative mechanism for BMP inactivation in SMAD4 wild type pancreatic cancers

Introduction: Genetic inactivation of SMAD4, a central mediator of TGF-β superfamily signaling, is significantly correlated with metastatic behavior in pancreatic cancer patients. However, because some patients with pancreatic cancer have genetically intact TGF-β and BMP pathway components, we investigated the role of alternative mechanisms of inactivation in promoting pancreatic cancer metastasis.

Methods: Eighteen cell lines for which the genetic status of all members of the TGF-β pathway were known were used in this study. TGF-β signaling levels were analyzed in each cell line using a luciferase reporter system under the control of a Smad Binding Element (SBE). Immunoblotting was performed on protein lysates from pancreatic cancer cell lines of known genotype. Cell lines that express high levels of Smad6 were transiently transfected with shRNA constructs targeting Smad6; cell lines that express low levels of Smad6 were transiently transfected with a construct to constitutively express Smad6. The effects of Smad6 modulation were assessed by proliferation assay, migration assay, and invasion assay. Immunohistochemistry was performed on primary and metastatic pancreatic cancer tissues and staining intensity correlated to clinical data.

Results: Functional TGF-β and BMP signaling were eliminated in cell lines with known SMAD4 inactivation, as well as in several cell lines in which these pathways remain intact. Immunoblotting for known TGF-β superfamily antagonists in these cell lines revealed differential expression of Smad6, an inhibitory Smad. Modulation of Smad6 levels in vitro suggests that Smad6 overexpression contributes to increased levels of proliferation, migration, and invasion in SMAD4-intact cell lines. Overexpression of Smad6 did not restore TGF-β signaling, but did increase BMP response. Immunohistochemistry for Smad6 in patient samples revealed a nuclear localization pattern, suggesting that the pro-oncogenic roles of Smad6 are mediated by its ability to act as a transcription factor. High Smad6 levels correlated with worse prognosis and metastatic behavior among SMAD4-intact pancreatic cancers.

Conclusions: Smad6, an inhibitory Smad, is differentially expressed in pancreatic cancer, both in cell lines and patient samples. High levels of Smad6 in patients at autopsy associate with widespread metastasis, irrespective of SMAD4 status. Preliminary studies in vitro support a metastasis-promoting function of Smad6: Smad6 overexpression is associated with increased levels of proliferation, migration, and invasion in SMAD4-intact pancreatic cancer cell lines. Experiments are ongoing to determine the mechanism through which Smad6 is acting in pancreatic cancer.

Citation Format: Jacqueline A. Brosnan, Richard Morgan, Catherine M. White, Seung-Mo Hong, Shinichi Yachida, Michael Goggins, Barish Edil, Christine A. Iacobuzio-Donahue. Smad6 upregulation provides an alternative mechanism for BMP inactivation in SMAD4 wild type pancreatic cancers. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4006. doi:10.1158/1538-7445.AM2013-4006

Pancreatic cancer genomics: insights and opportunities for clinical translation

Pancreatic cancer is a highly lethal tumor type for which there are few viable therapeutic options. It is also caused by the accumulation of mutations in a variety of genes. These genetic alterations can be grouped into those that accumulate during pancreatic intraepithelial neoplasia (precursor lesions) and thus are present in all cells of the infiltrating carcinoma, and those that accumulate specifically within the infiltrating carcinoma during subclonal evolution, resulting in genetic heterogeneity. Despite this heterogeneity there are nonetheless commonly altered cellular functions, such as pathways controlling the cell cycle, DNA damage repair, intracellular signaling and development, which could provide for a variety of drug targets. This review aims to summarize current knowledge of the genetics and genomics of pancreatic cancer from its inception to metastatic colonization, and to provide examples of how this information can be translated into the clinical setting for therapeutic benefit and personalized medicine.

Evolution and dynamics of pancreatic cancer progression

Efficient metastasis is believed as the result of multiple genetic, epigenetic and/or post-translational events in the lifetime of a carcinoma. At the genetic level, these events may be categorized into those that occur during carcinogenesis, and those that occur during subclonal evolution. This review summarizes current knowledge of the genetics of pancreatic cancer from its initiation within a normal cell until the time that is has disseminated to distant organs, many features of which can be extrapolated to other solid tumor types. The implications of these findings to personalize genome analyses of an individual patient's tumor are also discussed.

Abstract IA5: Genetics of clonal progression in pancreatic cancer

The goal of our laboratory is to understand the extent to which genetic features of a neoplasm influence its metastatic progression. Towards this goal we have focused on human pancreatic ductal adenocarcinoma (PDAC) as it represents an ideal tumor type for study of the metastatic process. For example, the precursor lesions that give rise to PDAC have been described in detail (pancreatic intraepithelial neoplasia, or PanIN), exomic sequencing has elucidated the major genetic alterations of this tumor type, and the accumulation of these genetic alterations during PanIN formation underlies the well accepted genetic progression model of pancreatic ductal carcinogenesis. Finally, PDAC is a tumor type that is often diagnosed in the advanced stages of disease and thus most patients have their primary carcinoma in situ for comparison to matched metastatic disease. Such is not the case for many other common human tumor types.

We have taken the unique approach of performing rapid autopsies for acquisition of primary and metastatic cancer tissues from a large number of individuals, and have used this resource to make several novel observations related to the timing of acquisition of metastatic traits. First, not all pancreatic cancers are metastatic; of those that do form metastases the range of deposits seen at autopsy ranges from few (&lt;10, oligometastatic disease) to &gt;100 (widely metastatic). Moreover, loss of the SMAD4 tumor suppressor gene that occurs during carcinogenesis is highly correlated with widespread metastatic disease. Second, using a whole exome sequencing approach we have defined the clonal evolution of PDAC. This has shown that the majority of genetic alterations are founder mutations in that they are encompassed with the parental clone of cells that give rise to PDAC, upon which are superimposed additional genetic alterations that accumulate during subclonal evolution. Geographic mapping of subclones based on their unique genetic signatures indicates that metastatic subclones originate within the primary carcinoma; moreover, several years are required for development of metastatic subclones beyond initiation of the infiltrating carcinoma by the parental clone. Thus, even in carcinomas with SMAD4 loss additional events are needed for successful metastasis to occur. Most recently, we have investigated pancreatic cancer progression by utilizing a mathematical framework of metastasis formation together with comprehensive data of PDAC patients obtained at autopsy. This work indicates that primary and metastatic PDAC growth is initially exponential, and that patients with seemingly early stage disease likely harbor metastases at diagnosis. Furthermore, based on the estimating rates of PDAC growth and dissemination, we analyzed the effects of different treatment modalities and found that therapies which efficiently reduce the growth rate of cells earlier in the course of treatment appear to be superior to upfront tumor resection. These lines of investigation not only shed light on this difficult tumor type but also have implications for most other major tumor types for which metastatic progression is common.

Citation Format: Christine A. Iacobuzio-Donahue. Genetics of clonal progression in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr IA5.

Blood-based screening for methylation changes in colorectal cancer patients using novel nanotechnologies

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Background: Identification of blood-based biomarkers for cancer screening is essential in order to develop novel and minimally invasive methods for colorectal cancer screening. Our lab has successfully applied a novel nanotechnology that allows us to detect and amplify a single tumor DNA fragment in a plasma sample. This DNA is tested for methylation of several genes including TFPI2 which has shown to be highly sensitive and specific for the detection colorectal cancer in stool. Methods: Whole blood was obtained from 18 colorectal cancer patients and plasma was isolated. Plasma was processed using Methylation On Beads nanotechnology (MOB) and bisulfate treated. Methylation status was determined via quantitative PCR method. Results: Two genes, TFPI2 and IGFBP3, were detected with a high sensitivity. TFPI2, demonstrated a methylation frequency of 94.4%, which is concordant with the TFPI2 methylation frequency of 99% in primary colorectal cancer tissues. IGFBP3 showed the methylation frequency of 61.1%, which corresponds with the methylation frequency of 52% in retrospective colorectal cancer tissues in previous studies. Quantification using standard curves indicated a single copy level of DNA found in plasma. Conclusions: Blood-based screening is challenging due to extremely low quantities of circulating DNA in blood. Utilizing a novel nanotechnology that detects DNA at a single copy level, the methylation changes in colorectal cancer were successfully detected in plasmas at similar frequencies as in tissue samples. This study has demonstrated the feasablility and applicability to blood-based screening. Future studies will focus on improving the sensitivity and determining the specificity of this method.

KRAS G>A mutation favors poor tumor differentiation but may not be associated with prognosis in patients with curatively resected duodenal adenocarcinoma

KRAS mutations have been found in duodenal adenocarcinomas and may have prognostic significance. The purpose of this study was to classify clinicopathological characteristics, microsatellite instability and KRAS mutations and identify possible prognostic role of KRAS mutations in duodenal adenocarcinomas. Demographics, tumor characteristics and survival were recorded for 78 patients with duodenal adenocarcinomas (Stages I-III). KRAS mutations were detected in 27 (34.6%) cases, of which the majority (74.1%) were G>A transitions. Multivariate logistic regression analysis showed that KRAS G>A mutation was significantly associated with late stage (p = 0.025) and poor tumor differentiation (p = 0.035), when compared with wild-type and other than G>A mutations. KRAS G>A mutation carriers were at increased risk for distant relapse (p = 0.022) and had significantly shorter overall survival (OS; log-rank p = 0.045) and a trend toward shorter relapse-free survival (RFS; log-rank p = 0.062) when compared with those who did not carry the KRAS G>A mutation. In multivariate analyses, there was a significant correlation between ≥ 3 positive lymph nodes and poor OS (p < 0.001) and RFS (p = 0.001) and KRAS G>A mutation carriers demonstrated no effect on clinical outcome. In conclusion, KRAS G>A mutation correlates significantly with late stage and poor tumor differentiation in duodenal adenocarcinoma. Among patients who undergo a curative resection of duodenal adenocarcinoma, KRAS G>A mutation carriers will more likely experience distant relapse but may not exhibit a poor prognosis. The number of positive lymph nodes should be incorporated in future staging systems.

Genetic basis of pancreas cancer development and progression: insights from whole-exome and whole-genome sequencing

Pancreatic cancer is caused by inherited and acquired mutations in specific cancer-associated genes. The discovery of the most common genetic alterations in pancreatic cancer has provided insight into the fundamental pathways that drive the progression from a normal cell to noninvasive precursor lesions and finally to widely metastatic disease. In addition, recent genetic discoveries have created new opportunities to develop gene-based approaches for early detection, personalized treatment, and molecular classification of pancreatic neoplasms.