Genes In Pancreatic Ductal Adenocarcinoma Research Articles

Real-Time Targeted Genome Profile Analysis of Pancreatic Ductal Adenocarcinomas Identifies Genetic Alterations That Might Be Targeted With Existing Drugs or Used as Biomarkers

It has been a challenge to select treatment for patients with pancreatic ductal adenocarcinomas (PDACs) based on genome alterations. We performed targeted genomic profile analyses of a large number of PDACs to assess the full spectrum of actionable genomic alterations. We performed targeted genomic profile analyses of 3594 PDAC samples from an international cohort, including capture-based targeted genomic profiling of as many as 315 cancer-associated genes and intron regions of 28 genes that are rearranged in cancer cells. Tumor mutation burden (TMB) and microsatellite instability (MSI) status were also assessed. TMB was calculated across a 1.14-megabase region; TMB-high was defined as ≥20 mutations/megabase. MSI-high status was assigned based on analysis of 114 intron homopolymer loci. KRAS, TP53, CDKN2A, and SMAD4 were the most frequently altered genes in PDAC. We found KRAS mutations in 88% of samples. Among PDACs without mutations in KRAS, we found alterations in genes whose products are in the mitogen-activated protein kinase signaling pathway and are candidate drug targets (actionable targets, n= 132; 4%), as well as gene fusions (n= 51), gene amplifications (n= 35), genes with missense mutations (n= 30), and genes that contain deletions (n= 16). Many of these encode proteins in receptor tyrosine kinase, RAS, or mitogen-activated protein kinase signaling pathways. Aside from TP53, alterations in genes encoding DNA damage repair proteins (BRCA and FANC) were detected in 14% of PDACs. Among PDACs evaluated for MSI (n= 2563) and TMB (n= 1021), MSI-high and/or TMB-high phenotypes were detected in 0.5% of samples. Alterations in FGF23, CCND2, PIK3CA, and FGF6 were more commonly detected in intraductal papillary mucinous neoplasm-associated PDACs. In targeted genomic profile analyses of 3594 PDACs, we found 17% to contain genomic alterations that might make the tumor cells susceptible to currently used anticancer agents. We identified mutations in genes that could contribute to progression of intraductal papillary mucinous neoplasms into malignancies. These alterations might be used as biomarkers for early detection.

Integrative Analysis of Novel Metabolic Subtypes in Pancreatic Cancer Fosters New Prognostic Biomarkers.

Background: Most of the patients with Pancreatic Ductal Adenocarcinoma (PDA) are not eligible for a curative surgical resection. For this reason there is an urgent need for personalized therapies. PDA is the result of complex interactions between tumor molecular profile and metabolites produced by its microenvironment. Despite recent studies identified PDA molecular subtypes, its metabolic classification is still lacking.Methods: We applied an integrative analysis on transcriptomic and genomic data of glycolytic genes in PDA. Data were collected from public datasets and molecular glycolytic subtypes were defined using hierarchical clustering. The grade of purity of the cancer samples was assessed estimating the different amount of stromal and immunological infiltrate among the identified PDA subtypes. Analyses of metabolomic data from a subset of PDA cell lines allowed us to identify the different metabolites produced by the metabolic subtypes. Sera of a cohort of 31 PDA patients were analyzed using Q-TOF mass spectrometer to measure the amount of metabolic circulating proteins present before and after chemotherapy.Results: Our integrative analysis of glycolytic genes identified two glycolytic and two non-glycolytic metabolic PDA subtypes. Glycolytic patients develop disease earlier, have poor prognosis, low immune-infiltrated tumors, and are characterized by a gain in chr12p13 genomic region. This gain results in the over-expression of GAPDH, TPI1, and FOXM1. PDA cell lines with the gain of chr12p13 are characterized by an higher lipid uptake and sensitivity to drug targeting the fatty acid metabolism. Our sera proteomic analysis confirms that TPI1 serum levels increase in poor prognosis gemcitabine-treated patients.Conclusions: We identify four metabolic PDA subtypes with different prognosis outcomes which may have pivotal role in setting personalized treatments. Moreover, our data suggest TPI1 as putative prognostic PDA biomarker.

Identification of key pathways and candidate genes in pancreatic ductal adenocarcinoma using bioinformatics analysis.

Pancreatic ductal adenocarcinoma (PDAC) is a malignant tumor with a high degree of malignancy that is difficult to diagnose and treat. The present study integrated PDAC cohort profile datasets to identify key candidate genes and pathways involved in the pathogenesis of the disease. The expression profiles of GSE28735 included 45 PDCA and matching pairs of adjacent non-tumor tissue. Differentially expressed genes (DEGs) were sorted and candidate genes and pathway enrichment were analyzed. A DEG-associated protein-protein interaction (PPI) network was constructed. A total of 424 DEGs were identified in PDAC, including 159 upregulated genes and 265 downregulated genes. Gene Ontology analysis results indicated that upregulated DEGs were significantly enriched in biological process, molecular function and cellular component categories. Kyoto Encyclopedia of Genes and Genomes pathway analysis demonstrated that the upregulated DEGs were enriched in ‘pancreatic secretion’, ‘protein digestion’ and ‘absorption’. Downregulated DEGs were enriched in ‘ECM-receptor interaction’, ‘focal adhesion’ and ‘PI3K/AKT’ signaling pathways. The PPI network revealed that these genes were involved in significant pathways, including ‘ECM organization’ signaling pathways (Hippo signaling pathway, TGF-β signaling pathway, Hedgehog signaling pathway and Wnt signaling pathway), ‘serine-type peptidase activity’ signaling pathway (PI3K-Akt signaling pathway, TNF-α signaling pathway and Wnt signaling pathway) and ‘extracellular region’ signaling pathways (RTP signaling pathway, G protein-coupled receptor signaling pathway and RAS-RAF-MAPK signaling pathway). The identification of these candidate genes and pathways sheds light on the etiology and molecular mechanisms of PDAC and may guide the development of novel therapies for pancreatic cancer.

KRAS and TP53 status as a predictor of survival in patients with resected pancreatic ductal adenocarcinoma.

276 Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers. KRAS, TP53, CDKN2A and SMAD4 are established driver genes in PDAC. We aimed to determine if the mutational status of these 4 driver genes, and other frequently altered genes, are predictive of clinical outcomes in patients who undergo resection. Methods: Patients who underwent resection of PDAC and consented to targeted sequencing of their primary tumor using MSK-IMPACT, were included. Genomic alterations were determined based on MSK-IMPACT sequencing results of formalin-fixed, paraffin-embedded tumor. A prospectively maintained database and electronic medical record were queried for clinical and pathologic variables. Gene mutation status was compared with overall survival (OS) and recurrence free survival (RFS) using the log-rank test, and with pathologic variables using Wilcoxon rank-sum and Fisher’s exact tests. Results: Targeted genomic sequencing was performed on N = 285 primary tumors resected between 2004-2017. N = 55 (19%) patients received neoadjuvant therapy prior to sequencing and N = 220 (77%) received adjuvant therapy. Median OS was 39 months with a median follow up of 22 months. Frequency of genomic alterations and their association with OS and RFS are shown in Table 1. Alterations in both KRAS and TP53 were associated with worse OS, but not RFS, as compared to wildtype. Mutant KRAS was also associated with larger tumor size (median, 3.0 vs 2.2cm, p = 0.009). Conclusions: Alterations in KRAS and TP53 were associated with worse OS in patients with resected PDAC. Further analysis will include the association of driver gene variants, as well as other gene alterations, with clinical and pathologic outcomes. [Table: see text]

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Upregulation of HOX Genes in Pancreatic Ductal Adenocarcinoma Associated with Exceptionally Long Survival

Journal of the American College of Surgeons 227(4):p e180-e181, October 2018. | DOI: 10.1016/j.jamcollsurg.2018.08.492

Identification of potential target genes in pancreatic ductal adenocarcinoma by bioinformatics analysis.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most complicated and fatally pathogenic human malignancies. Therefore, there is an urgent need to improve our understanding of the underlying molecular mechanism that drives the initiation, progression, and metastasis of PDAC. The aim of the present study was to identify the key genes and signaling pathways associated with PDAC using bioinformatics analysis. Four transcriptome microarray datasets (GSE15471, GSE55643, GSE62165 and GSE91035) were acquired from Gene Expression Omnibus datasets, which included 226 PDAC samples and 65 normal pancreatic tissue samples. We screened differentially expressed genes (DEGs) with GEO2R and investigated their biological function by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analysis. The overall survival data was obtained from UALCAN, which calculated the data shared with The Cancer Genome Atlas. In addition, a protein-protein interaction (PPI) network of the DEGs was constructed by STRING and Cytoscape software. The four sets of DEGs exhibited an intersection consisting of 205 genes (142 up-regulated and 63 down-regulated), which may be associated with PDAC. GO analysis showed that the 205 DEGs were significantly enriched in the plasma membrane, cell adhesion molecule activity and the Energy pathways, and glycine, serine, threonine metabolism were the most enriched pathways according to KEGG pathway analysis. Kaplan-Meier survival analysis revealed that 22 of 205 common genes were significantly associated with the overall survival of pancreatic cancer patients. In the PPI network and sub-network, DKK1 and HMGA2 were considered as hub genes with high connectivity degrees. DKK1 and HMGA2 are strongly associated with WNT3A and TP53 separately, which indicates that they may play an important role in the Wnt and P53 signaling pathways. Using integrated bioinformatics analysis, we identified DKK1 and HMGA2 as candidate genes in PDAC, which may improve our understanding of the mechanisms of the pathogenesis and integration; the two genes may be therapeutic targets and prognostic markers for PDAC.

Mutations in BRCA1, BRCA2, and PALB2, and a panel of 50 cancer-associated genes in pancreatic ductal adenocarcinoma

Mutations in genes of the breast cancer susceptibility gene (BRCA) pathway, namely, BRCA1, BRCA2, and PALB2, can provide useful information for the efficacy of platinum-based or poly ADP-ribose polymerase inhibitors chemotherapeutic regimens. Pancreatic ductal adenocarcinoma (PDAC) is an important target for such precision chemotherapies because of its dismal prognosis. We analyzed mutations in the entire coding regions of the BRCA pathway genes, expression of breast cancer 2 (BRCA2), and mutations in hotspots of 50 cancer-associated genes in 42 surgically resected PDACs, and evaluated their associations with clinicopathological features. We identified 13 rare germline mutations in the BRCA pathway genes; 68 somatic mutations in KRAS, TP53, SMAD4, CDKN2A, GNAS, SMARCB1, and RB1; and 2 germline variations in MLH1. Among them, BRCA2S2148fs was known to be pathogenic. BRCA2R18H and BRCA2G2044V were enriched in tumor tissues. BRCA2K799R and BRCA2R2964T were novel germline variations. Patients harboring potentially deleterious mutations in the BRCA pathway genes showed significantly better prognosis than those with benign mutations or no mutation. These results indicate that rare germline variations in BRCA pathway genes could be found more frequently than previously anticipated and, more importantly, potentially deleterious mutations of them could be a favorable prognostic factor in patients with resectable PDACs.

Abstract PR04: p120 catenin loss drives pancreatic cancer EMT and metastasis through activation of calcium signaling

Abstract Purpose: We have generated a mouse model to delete the gene Ctnnd1, whose gene product p120 catenin (p120ctn) is necessary for E-CADHERIN stability, resulting in enhanced metastasis in the conventional KPC pancreatic tumor mouse model. An unbiased screen of tumor cells isolated from these mice identified misregulated calcium signaling as a previously unappreciated contributor to epithelial-to-mesenchymal transition (EMT) and metastasis. Thus, our overarching hypothesis is that p120ctn loss in pancreatic cancer drives EMT and metastasis through functional upregulation of the calcium signaling component PTHLH. Background: Pancreatic ductal adenocarcinoma (PDAC) is a major health issue, with only 7% of patients surviving beyond 5 years, and increases in PDAC-associated deaths project this disease to be the second leading cause of cancer deaths by 2020. An unbiased approach to discover candidate cancer genes in PDAC identified the p120 catenin gene as one of the top 20 PDAC cancer genes, and further analysis revealed that p120ctn loss was associated with reduced PDAC patient survival. Recent work from our lab further demonstrated that conditional p120ctn/Ctnnd1 deletion in the esophagus was sufficient to drive invasive squamous cell carcinoma, establishing p120ctn/Ctnnd1 as a bona fide tumor-suppressor gene. Results presented herein determined the in vivo role of p120ctn loss in PDAC tumorigenesis and metastasis through genetic mouse models and unbiased RNA-seq analysis. Methods: A PDAC mouse model was established to study the role of p120ctn in pancreatic carcinogenesis and metastasis. Specifically, LSL-KrasG12D/+; p53fl/+; Pdx1cre; Rosa26LSL-YFP; Ctnnd1fl/wt mice (herein KPCY-p120CKO) were generated to determine the effect of conditional p120ctn loss on pancreatic cancer. Furthermore, RNA-seq was performed on p120-intact or p120-null pancreatic tumor cells isolated from these mice to identify novel mechanisms of pancreatic tumorigenesis and metastasis. Results: We demonstrate p120ctn loss as a catastrophic event for tumor epithelial cell identity in vivo, leading to enhanced EMT and metastasis. Specifically, we show that KPCY-p120CKO mice have an enhanced metastatic phenotype relative to KPCY controls. Our data therefore suggest that p120ctn is a critical factor in metastatic cell dissemination, and that p120ctn loss results in tumor cells being “locked” in a mesenchymal phenotype by failing to stabilize E-cadherin at the metastatic site. To determine the mechanism of enhanced EMT and metastasis, RNA-seq analysis of p120ctn-null tumor cells was performed, which surprisingly revealed aberrant activation of calcium signaling. Unexpectedly, two of the top five most upregulated genes in p120ctn-null cells were the secreted factor Pthlh and the kinase Camk2b, both of which are key signaling molecules involved in calcium signaling. We demonstrate that PTHLH binding to its cognate receptor leads to cytosolic calcium ion (Ca2+) release, resulting in phosphorylation and activation of CaMKII. We further establish that genetic deletion or pharmacologic inhibition of Pthlh results in proliferation and migration defects. Moreover, orthotopic implantation of KPC-PthlhNULL tumor cell lines reduced tumor growth and metastasis in vivo. Finally, we show that PDAC patients with high expression of Pthlh have significantly decreased survival, suggesting that calcium signaling may be a potent oncogenic pathway in pancreatic cancer and that blocking this pathway may be of therapeutic benefit. Conclusions: This work has demonstrated the importance of the previously unappreciated role of calcium signaling in pancreatic cancer progression and metastasis, and future studies will look to determine the efficacy of calcium-modulating therapeutics in preclinical models of pancreatic cancer. This abstract is also being presented as Poster A42. Citation Format: Jason R. Pitarresi, Maximilian Reichert, Basil Bakir, Leticia Moreira, Lauren Simon, Anil K. Rustgi. p120 catenin loss drives pancreatic cancer EMT and metastasis through activation of calcium signaling [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr PR04.

Targeted deep sequencing of circulating tumor DNA in metastatic pancreatic cancer.

PurposePrecision medicine in pancreatic ductal adenocarcinoma (PDAC) could be substantially supported by tools that allow to establish and monitor the molecular setup of the tumor. In particular, noninvasive approaches are desirable, but not validated. Characterization of circulating tumor DNA (ctDNA) may help to achieve this goal.Experimental DesignBlood samples from patients with metastatic PDAC prior to and during palliative treatment were collected. ctDNA and corresponding tumor tissue were analyzed by targeted next generation sequencing and droplet digital PCR for the 7 most frequently mutated genes in PDAC (TP53, SMAD4, CDKN2A, KRAS, APC, ATM, and FBXW7). Findings were correlated with clinical and imaging data.ResultsA total of 20 patients (therapy naïve n = 11; pretreated n = 9) were included. All therapy naïve patients (n = 11/11) presented with detectable ctDNA at baseline. In pretreated patients, 3/7 (prior to 2nd line treatment) and 2/2 (prior to 3rd line chemotherapy) had detectable ctDNA. The combined mutational allele frequency (CMAF) of KRAS and TP53 was chosen to reflect the amount of ctDNA. The median CMAF level significantly decreased during treatment (P = 0.0027) and increased at progression (P = 0.0104). CA19-9 analyses did not show significant differences. In treatment naïve patients, the CMAF levels during therapy significantly correlated with progression-free survival (Spearman, r = −0.8609, P = 0.0013).ConclusionsMonitoring of ctDNA and its changes during treatment may enable to adapt therapeutic strategies to the specific molecular changes present at a certain time during treatment of mPDAC.

SOX9 activity is induced by oncogenic Kras to affect MDC1 and MCMs expression in pancreatic cancer.

SRY (sex determining region Y)-box 9 (SOX9) is required for oncogenic Kras-mediated acinar-to-ductal metaplasia (ADM), pancreatic intraepithelial neoplasias (PanINs) and ultimately pancreatic ductal adenocarcinoma (PDAC). However, how oncogenic Kras affects SOX9 activity is not yet understood, and SOX9-associated genes in PDAC are also unknown at all. Here, we investigated the mechanistic link between SOX9 and oncogenic Kras, studied biological function of SOX9, and identified SOX9-related genes and their clinical significance in patients with PDAC. Our studies reveal that oncogenic Kras induces SOX9 mRNA and protein expression as well as phosphorylated SOX9 expression in human pancreatic ductal progenitor cells (HPNE) and pancreatic ductal cells (HPDE). Moreover, oncogenic Kras promoted nuclear translocation and transcriptional activity of SOX9 in these cells. TAK1/IκBα/NF-κB pathway contributed to induction of SOX9 by oncogenic Kras, and SOX9 in turn enhanced NF-κB activation. SOX9 promoted the proliferation of HPNE and PDAC cells, and correlated with minichromosome maintenance complex components (MCMs) and mediator of DNA damage checkpoint 1 (MDC1) expression. The overexpressive MDC1 was associated with less perineural and lymph node invasion of tumors and early TNM-stage of patients. Our results indicate that oncogenic Kras induces constitutive activation of SOX9 in HPNE and HPDE cells, and Kras/TAK1/IκBα/NF-κB pathway and a positive feedback between SOX9 and NF-κB are involved in this inducing process. SOX9 accelerates proliferation of cells and affects MCMs and MDC1 expression. MDC1 is associated negatively with invasion and metastasis of PDAC.

Deubiquitinase USP9X promotes cell migration, invasion and inhibits apoptosis of human pancreatic cancer.

Ubiquitin specific peptidase9, X-linked (USP9X), a significant regulatory protease in protein ubiquitination, has been proven to act as a proto-oncogene in several types of cancers, such as cervix, colon, breast, brain and lung cancers. The prognosis of patients with pancreatic ductal adenocarcinoma (PDAC) is extremely poor due to its high invasive and metastatic abilities. Nevertheless, whether USP9X acts as a proto-oncogene or a tumor-suppressor gene in PDAC is controversial and the mechanism of metastasis remains unknown. The present study focused on the effect of USP9X on the migration, invasion and apoptosis of PADC cells. We analyzed the expression of USP9X in pancreatic cancer tissues of different pathologic grades by immunohistochemical analysis. USP9X expression in the pancreatic cancer tissues was markedly increased in contrast to that noted in the adjacent non-tumor tissues. USP9X expression in PANC-1 cells was downregulated after transfection of shRNA-USP9X. Knockdown of endogenous USP9X expression evidently inhibited the migration and invasion of PANC-1 cells, and promoted cell apoptosis. Meanwhile, expression levels of Snail, Twist, N-cadherin and vimentin were downregulated. E-cadherin expression was negatively correlated with USP9X expression and the expression of survivin was also downregulated in the PANC-1 cells. In brief, USP9X promoted the migration and invasion of PANC-1 cells probably by provoking epithelial-mesenchymal transition, and also inhibited apoptosis. We believe that USP9X is a major oncogene that may play a significant role in the treatment and prognosis of PDAC.

Modulation of RAB5A early endosome trafficking in response to KRas mediated macropinocytic fluxes in pancreatic cancer cells

KRAS is the key mutated gene in pancreatic ductal adenocarcinoma (PDAC). Emerging evidence indicates that KRas modulates endocytic uptake. The present study aimed to explore the fate of early endosomal trafficking under the control of KRas expression in PDAC.Surprisingly, PANC-1 cells lacking KRas exhibited significantly enlarged early and late endosomes containing internalized dextran and epidermal growth factor. Endosome enlargement was accompanied by reduced endosomal degradation. Both KRas silencing and lysosomal blockade caused an upregulation of the master regulator of early endosome biogenesis, RAB5A, which is likely responsible for the expansion of the early endosomal compartment, because simultaneous KRAS/RAB5A knockdown abolished endosome enlargement. In contrast, early endosome shrinkage was seen in MIA PaCa-2 cells despite RAB5A upregulation, indicating that distinct KRas-modulated responses operate in different metabolic subtypes of PDAC.In conclusion, mutant KRAS promotes endosomal degradation in PDAC cell lines, which is impaired by KRAS silencing. Moreover, KRAS silencing activates RAB5A upregulation and drives PDAC subtype-dependent modulation of endosome trafficking.

Abstract 4395: Somatic genomic alteration of 412 cancer-targeted genes of periampullary and pancreatic ductal adenocarcinoma in Indian patient population

Abstract Introduction: Pancreatic Ductal Adenocarcinoma (PDAC), the most common primary malignant disease of the pancreas and the periampullary region, accounts for about 75% of all nonendocrine tumors arising in this region. It is 4th most lethal malignancies. The 5 year survivability rate is below 5%. At the beginning of the 21st century, the estimated number of PC worldwide was 110,000, with an estimated global mortality rate of 98%. Incidence of periampullary adenocarinoma (PACs) is low, approximately 0.5-2% of all gastrointestinal malignancies and 20% of all tumors of the extrahepatic biliary tree. Aims & Objectives: To identify the somatic single nucleotide variants (SNV’s) in 412 cancer related genes in PDAC & PAC’s. To identify possible altered biological pathways enriched in these cancers. Methodology: DNA samples from Tissue and blood were sequenced for exon sequencing of 412 cancer related genes (NIMBLGNE panel, Custom). Raw fastq files processed using GATK tools and variants identified by Varscan2, & MuTect. Altered pathways identified by KEEG. Result: A total 105 Somatic exonic Single Nucleotide Variants (SNV’s), 9 somatic exonic Indels, 22 LOH mutations (both Indel and SNV’s) were identified in our sample set. Among the candidate genes of PDAC somatic SNV’s were found in TP53, SMAD4 in some patient whereas frequency of KRAS mutation was less frequent. Fourteen SNV’s were reported in cosmic database which includes 5 pathogenic variants, whereas 91 SNV’s were novel. A total 75 non-synonymous, 6 stopgain, and 24 synonymous SNV’s were observed among 105 SNV’s. Fifty eight percent of transversion and 52% of transition observed from all SNVs. Among all transversion fifty five percent SNV’s were C>T, G>T. PI3-Akt, Proteoglycans in cancer, Transcription misregulation, Rap1, ErbB, Neurotrophin pathways were found to be most commonly enriched in our patient population. Our data strongly suggest PI3-Akt, Proteoglycans in cancer pathways play a critical role in the disease. Conclusion: This study implicates a landscape of somatic SNV’s in PDAC’s and PAC’s and alteration of biological pathways in our patient population. We also observeed ERBB2 and KMT2C genes are predominantly alerted in PDAC’s and PAC’s. P53, KRAS and SMAD4 are the known mutated genes contributes very similar mutational pattern. Citation Format: Nilabja Sikdar, Gourab Saha, Richa Singh, Dhiraj Anchlia, Paromita Roy, Supriyo Ghatak, Sudeep Banerjee, Sumit Gulati, Shibajyoti Ghosh. Somatic genomic alteration of 412 cancer-targeted genes of periampullary and pancreatic ductal adenocarcinoma in Indian patient population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4395. doi:10.1158/1538-7445.AM2017-4395

Stromal SPOCK1 supports invasive pancreatic cancer growth.

Pancreatic ductal adenocarcinoma (PDAC) is marked by an abundant stromal deposition. This stroma is suspected to harbor both tumor‐promoting and tumor‐suppressing properties. This is underscored by the disappointing results of stroma targeting in clinical studies. Given the complexity of tumor–stroma interaction in PDAC, there is a need to identify the stromal proteins that are predominantly tumor‐promoting. One possible candidate is SPOCK1 that we previously identified in a screening effort in PDAC. We extensively mined PDAC gene expression datasets, and used species‐specific transcript analysis in mixed‐species models for PDAC to study the patterns and driver mechanisms of SPOCK1 expression in PDAC. Advanced organotypic coculture models with primary patient‐derived tumor cells were used to further characterize the function of this protein. We found SPOCK1 expression to be predominantly stromal. Expression of SPOCK1 was associated with poor disease outcome. Coculture and ligand stimulation experiments revealed that SPOCK1 is expressed in response to tumor cell‐derived transforming growth factor‐beta. Functional assessment in cocultures demonstrated that SPOCK1 strongly affects the composition of the extracellular collagen matrix and by doing so, enables invasive tumor cell growth in PDAC. By defining the expression pattern and functional properties of SPOCK1 in pancreatic cancer, we have identified a stromal mediator of extracellular matrix remodeling that indirectly affects the aggressive behavior of PDAC cells. The recognition that stromal proteins actively contribute to the protumorigenic remodeling of the tumor microenvironment should aid the design of future clinical studies to target specific stromal targets.

CRISPR Knockout of the HuR Gene Causes a Xenograft Lethal Phenotype.

Pancreatic ductal adenocarcinoma (PDA) is the third leading cause of cancer-related deaths in the United States, whereas colorectal cancer is the third most common cancer. The RNA-binding protein HuR (ELAVL1) supports a pro-oncogenic network in gastrointestinal (GI) cancer cells through enhanced HuR expression. Using a publically available database, HuR expression levels were determined to be increased in primary PDA and colorectal cancer tumor cohorts as compared with normal pancreas and colon tissues, respectively. CRISPR/Cas9 technology was successfully used to delete the HuR gene in both PDA (MIA PaCa-2 and Hs 766T) and colorectal cancer (HCT116) cell lines. HuR deficiency has a mild phenotype, in vitro, as HuR-deficient MIA PaCa-2 (MIA.HuR-KO(-/-)) cells had increased apoptosis when compared with isogenic wild-type (MIA.HuR-WT(+/+)) cells. Using this isogenic system, mRNAs were identified that specifically bound to HuR and were required for transforming a two-dimensional culture into three dimensional (i.e., organoids). Importantly, HuR-deficient MIA PaCa-2 and Hs 766T cells were unable to engraft tumors in vivo compared with control HuR-proficient cells, demonstrating a unique xenograft lethal phenotype. Although not as a dramatic phenotype, CRISPR knockout HuR HCT116 colon cancer cells (HCT.HuR-KO(-/-)) showed significantly reduced in vivo tumor growth compared with controls (HCT.HuR-WT(+/+)). Finally, HuR deletion affects KRAS activity and controls a subset of pro-oncogenic genes.Implications: The work reported here supports the notion that targeting HuR is a promising therapeutic strategy to treat GI malignancies. Mol Cancer Res; 15(6); 696-707. ©2017 AACR.

Non-invasive diagnosis and tracking of tumor evolution by targeted sequencing of circulating tumor DNA in metastatic pancreatic cancer patients.

e15769 Background: Treatment of stage IV pancreatic ductal adenocarcinoma (PDAC) has made substantial progress over the last years, therapy monitoring still is at an early stage. This could be substantially supported by tools that allow to establish and monitor the molecular setup of the tumor even during treatment. In particular, non-invasive approaches are desirable. Characterization of circulating tumor DNA (ctDNA) may help to achieve this goal. Methods: We analyzed a cohort of 20 patients with histologically confirmed metastatic PDAC (mPDAC) prior to and during palliative treatment including disease progression. ctDNA and corresponding tumor tissue were analyzed by targeted NGS and droplet digital PCR for the 7 most frequently mutated genes in PDAC ( TP53, SMAD4, CDKN2A, KRAS, APC, ATM, FBXW7). Findings were correlated with clinical and imaging data to establish its prognostic and predictive value. Results: ctDNA was analyzed at baseline prior to initiation of the respective line of treatment. Mutations in either of the genes examined were detectable in 15/20 patients (75%). Tissue-blood concordance was 80% in therapy naïve patients. 96% of mutations in ctDNA of therapy naïve patients were in KRAS and/or TP53. The combined mutated allele frequencies (CMAF) of theese 2 genes significantly decreased (p = 0.0173) during therapy and increased at progression (p = 0.0145) across all treatment lines. By sequential ctDNA analyses we detected a change in the mutational landscape compared to the respective baseline ctDNA status in 7/11 patients during 1st line, in 3/7 patients during 2nd line and 2/2 patients during 3rdline treatment. In therapy naïve patients, the decline of the CMAF during therapy significantly correlated with progression-free survival (p = 0.0013). Conclusions: Molecular genotyping of ctDNA in mPDAC patients proved to be feasible and there was a high concordance between tumor tissue and ctDNA. The molecular genotype changed significantly during treatment and changes correlated with outcome. Monitoring of ctDNA may enable to adapt therapeutic strategies to the specific molecular changes present at a certain time during treatment of mPDAC.

Identification of candidate miRNA biomarkers for pancreatic ductal adenocarcinoma by weighted gene co-expression network analysis.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a dismal prognosis which is, among others, due to a lack of suitable biomarkers and therapeutic targets. Previously, basic gene expression analysis methods have been used for their identification, but recently new algorithms have been developed allowing more comprehensive data analyses. Among them, weighted gene co-expression network analysis (WGCNA) has already been applied to several cancer types with promising results. We applied WGCNA to miRNA expression data from PDAC patients. Specifically, we processed microarray-based expression data of 2555 miRNAs in serum from 100 PDAC patients and 150 healthy subjects. We identified network modules of co-expressed miRNAs in the healthy subject dataset and verified their preservation in the PDAC dataset. In the non-preserved modules, we selected key miRNAs and carried out functional enrichment analyses of their experimentally known target genes. Finally, we tested their prognostic significance using overall survival analyses. Through WGCNA we identified several miRNAs that discriminate healthy subjects from PDAC patients and that, therefore, may play critical roles in PDAC development. At a functional level, we found that they regulate p53, FoxO and ErbB associated cellular signalling pathways, as well as cell cycle progression and various genes known to be involved in PDAC development. Some miRNAs were also found to serve as novel prognostic biomarkers, whereas others have previously already been proposed as such, thereby validating the WGCNA approach. In addition, we found that these novel data may explain at least some of our previous PDAC gene expression analysis results. We identified several miRNAs critical for PDAC development using WGCNA. These miRNAs may serve as biomarkers for PDAC diagnosis/prognosis and patient stratification, and as putative novel therapeutic targets.

Master Regulators of Oncogenic KRAS Response in Pancreatic Cancer: An Integrative Network Biology Analysis.

BackgroundKRAS is the most frequently mutated gene in pancreatic ductal adenocarcinoma (PDAC), but the mechanisms underlying the transcriptional response to oncogenic KRAS are still not fully understood. We aimed to uncover transcription factors that regulate the transcriptional response of oncogenic KRAS in pancreatic cancer and to understand their clinical relevance.Methods and FindingsWe applied a well-established network biology approach (master regulator analysis) to combine a transcriptional signature for oncogenic KRAS derived from a murine isogenic cell line with a coexpression network derived by integrating 560 human pancreatic cancer cases across seven studies. The datasets included the ICGC cohort (n = 242), the TCGA cohort (n = 178), and five smaller studies (n = 17, 25, 26, 36, and 36). 55 transcription factors were coexpressed with a significant number of genes in the transcriptional signature (gene set enrichment analysis [GSEA] p < 0.01). Community detection in the coexpression network identified 27 of the 55 transcription factors contributing to three major biological processes: Notch pathway, down-regulated Hedgehog/Wnt pathway, and cell cycle. The activities of these processes define three distinct subtypes of PDAC, which demonstrate differences in survival and mutational load as well as stromal and immune cell composition. The Hedgehog subgroup showed worst survival (hazard ratio 1.73, 95% CI 1.1 to 2.72, coxPH test p = 0.018) and the Notch subgroup the best (hazard ratio 0.62, 95% CI 0.42 to 0.93, coxPH test p = 0.019). The cell cycle subtype showed highest mutational burden (ANOVA p < 0.01) and the smallest amount of stromal admixture (ANOVA p < 2.2e–16). This study is limited by the information provided in published datasets, not all of which provide mutational profiles, survival data, or the specifics of treatment history.ConclusionsOur results characterize the regulatory mechanisms underlying the transcriptional response to oncogenic KRAS and provide a framework to develop strategies for specific subtypes of this disease using current therapeutics and by identifying targets for new groups.

HDAC2 promotes loss of primary cilia in pancreatic ductal adenocarcinoma.

Loss of primary cilia is frequently observed in tumor cells, including pancreatic ductal adenocarcinoma (PDAC) cells, suggesting that the absence of this organelle may promote tumorigenesis through aberrant signal transduction and the inability to exit the cell cycle. However, the molecular mechanisms that explain how PDAC cells lose primary cilia are still ambiguous. In this study, we found that inhibition or silencing of histone deacetylase 2 (HDAC2) restores primary cilia formation in PDAC cells. Inactivation of HDAC2 results in decreased Aurora A expression, which promotes disassembly of primary cilia. We further showed that HDAC2 controls ciliogenesis independently of Kras, which facilitates Aurora A expression. These studies suggest that HDAC2 is a novel regulator of primary cilium formation in PDAC cells.