Published OnlineFirst September 3, 2019; DOI: 10.1158/1078-0432.CCR-19-1543
CLINICAL CANCER RESEARCH | PRECISION MEDICINE AND IMAGING
Altered Gene Expression along the Glycolysis– Cholesterol Synthesis Axis Is Associated with Outcome in Pancreatic Cancer Joanna M. Karasinska1, James T. Topham1, Steve E. Kalloger1,2, Gun Ho Jang3, Robert E. Denroche3, Luka Culibrk4, Laura M. Williamson4, Hui-Li Wong5, Michael K.C. Lee5, Grainne M. O’Kane6, Richard A. Moore4, Andrew J. Mungall4, Malcolm J. Moore5, Cassia Warren1, Andrew Metcalfe1, Faiyaz Notta3, Jennifer J. Knox6, Steven Gallinger3,6, Janessa Laskin4,5, Marco A. Marra4,7, Steven J.M. Jones4,7, Daniel J. Renouf1,5,8, and David F. Schaeffer1,2,9
ABSTRACT ◥ Purpose: Identification of clinically actionable molecular Results: On the basis of the median normalized expression of subtypes of pancreatic ductal adenocarcinoma (PDAC) is key glycolytic and cholesterogenic genes, four subgroups were iden- to improving patient outcome. Intertumoral metabolic het- tified: quiescent, glycolytic, cholesterogenic, and mixed. Glyco- erogeneity contributes to cancer survival and the balance lytic tumors were associated with the shortest median survival in between distinct metabolic pathways may influence PDAC resectable (log-rank test P ¼ 0.018) and metastatic settings (log- outcome. We hypothesized that PDAC can be stratified into rank test P ¼ 0.027). Patients with cholesterogenic tumors had the prognostic metabolic subgroups based on alterations in the longest median survival. KRAS and MYC-amplified tumors had expression of genes involved in glycolysis and cholesterol higher expression of glycolytic genes than tumors with normal or synthesis. lost copies of the oncogenes (Wilcoxon rank sum test P ¼ 0.015). Experimental Design: We performed bioinformatics analysis Glycolytic tumors had the lowest expression of mitochondrial of genomic, transcriptomic, and clinical data in an integrated pyruvate carriers MPC1 and MPC2. Glycolytic and cholestero- cohort of 325 resectable and nonresectable PDAC. The resectable genic gene expression correlated with the expression of prognos- datasets included retrospective The Cancer Genome Atlas tic PDAC subtype classifier genes. (TCGA) and the International Cancer Genome Consortium Conclusions: Metabolic classification specific to glycolytic and (ICGC) cohorts. The nonresectable PDAC cohort studies included cholesterogenic pathways provides novel biological insight into prospective COMPASS, PanGen, and BC Cancer Personalized previously established PDAC subtypes and may help develop OncoGenomics program (POG). personalized therapies targeting unique tumor metabolic profiles.
specific cellular tumor progression pathways contribute to PDAC Introduction prognostic stratification is needed to enable customized treatment The 5-year survival rate in pancreatic ductal adenocarcinoma design and novel therapeutics development. (PDAC) is less than 10% and remains one of the lowest in all Oncogene-driven metabolic adaptations allow cancer cells to sur- cancers. Effective therapy is limited by the treatment-refractory vive and thrive in the tumor microenvironment (9). A pan-cancer nature of PDAC and a short supply of clinically validated biomar- analysis of global metabolic pathways showed that tumor metabolic kers capable of predicting treatment response (1). Emerging molec- heterogeneity is associated with survival, somatic driver mutations, ular subtypes of PDAC have defined intertumoral heterogeneity and tumor subtypes (10), but whether heterogeneity in distinct met- at the genome and transcriptome levels (2–6), driving efforts to abolic pathways can be used to stratify PDAC into clinically relevant identify clinically relevant biomarker signatures and actionable subgroups has not been well established. A vast majority of PDACs genomic alterations (7, 8). However, a better understanding of how harbor oncogenic KRAS and loss-of-function TP53 mutations (6), in
1Pancreas Centre BC, Vancouver, British Columbia, Canada. 2Department of Clinical trial information: Personalized OncoGenomics (POG) Program of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia: Utilization of Genomic Analysis to Better Understand Tumour British Columbia, Canada. 3Ontario Institute for Cancer Research, Toronto, Heterogeneity and Evolution (NCT02155621); Prospectively Defining Metastatic Ontario, Canada. 4Canada's Michael Smith Genome Sciences Centre, Vancouver, Pancreatic Ductal Adenocarcinoma Subtypes by Comprehensive Genomic British Columbia, Canada. 5Division of Medical Oncology, BC Cancer, Vancouver, Analysis (PanGen; NCT02869802); Comprehensive Molecular Characterization British Columbia, Canada. 6University Health Network, University of Toronto, of Advanced Pancreatic Ductal Adenocarcinoma for Better Treatment Selection Toronto, Ontario, Canada. 7Department of Medical Genetics, University of British (COMPASS; NCT02750657). Columbia, Vancouver, British Columbia, Canada. 8Department of Medicine, Corresponding Author: David F. Schaeffer, University of British Columbia, University of British Columbia, Vancouver, British Columbia, Canada. 9Division Vancouver General Hospital, 910 West 10th Avenue, Vancouver V5Z 1M9, of Anatomic Pathology, Vancouver General Hospital, Vancouver, British Colum- Canada. Phone: 604-875-4480; Fax: 604-875-5707; E-mail: bia, Canada. [email protected] Note: Supplementary data for this article are available at Clinical Cancer Clin Cancer Res 2019;XX:XX–XX Research Online (http://clincancerres.aacrjournals.org/). doi: 10.1158/1078-0432.CCR-19-1543 J.M. Karasinska, J.T. Topham, S.E. Kalloger, D.J. Renouf, and D.F. Schaeffer contributed equally to this article. 2019 American Association for Cancer Research.
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Karasinska et al.
NCT02750657) studies at the BC Cancer Agency (PanGen, POG) Translational Relevance and Ontario Institute for Cancer Research (COMPASS) as Pancreatic ductal adenocarcinoma (PDAC) has one of the described previously (7, 29). The PanGen and POG studies were lowest survival rates of all cancers due in part to a limited approved by the University of British Columbia Research Ethics knowledge of clinically relevant tumor subtypes that would facil- Committee (REB# H12-00137, H14-00681, H16-00291) and itate better treatment stratification and the development of new the COMPASS study was approved by the University Health therapies targeting unique molecular signatures. Tumor metabolic Network Research Ethics Board (REB# 15-9596). The studies were heterogeneity contributes to clinical outcome in cancer and repre- conducted in accordance with international ethical guidelines. sents a potential avenue for the development of personalized Written informed consent was obtained from each patient prior treatment strategies. How alterations in distinct metabolic path- to genomic profiling. ways influence PDAC outcome is not well known. We profiled the expression of glycolytic and cholesterogenic genes in 325 resectable Whole genome and transcriptome sequencing and non-resectable PDAC patients and identified distinct sub- POG and PanGen samples were subjected to whole genome and fl groups associated with differences in survival and known prog- transcriptome sequencing as described previously (30). Brie y, nostic pancreatic tumor subtypes. Our findings demonstrate that fresh tumor biopsies were sequenced to a depth of approximately distinct metabolic gene expression pathways may provide a func- 80 , with approximately 200 million reads generated for transcrip- tional correlate to transcriptome-based pancreatic cancer subtypes, tomes. RNA sequencing (RNA-seq) libraries were prepared using fi which may enable the development of subtype-specific treatment inactive magnetic bead-based mRNA puri cation. RNA-seq was strategies targeting unique metabolic vulnerabilities. performed on COMPASS samples as described previously (7). TCGA (PAAD-US) and ICGC (PACA-CA) data Normalized RNA-seq data (sequence-based gene expression; GRCh37) for all available PAAD-US (n ¼ 142) and PACA-CA addition to prevalent hypoxia (11), which are known inducers of the (n ¼ 234) samples were downloaded from the ICGC data portal – glycolytic pathway in cancer (12 15), and glycolysis contributes to (dcc.icgc.org/) on November 8, 2018 (ICGC data release 27). PACA- tumor progression and chemoresistance in PDAC (13, 16, 17). The CA samples were filtered to exclude any samples labeled as cell lines, effects of glycolysis on tumor progression can be diminished by xenografts, metastatic, normal, or non-laser microdissected enriched. diverting the metabolite pyruvate from conversion to lactate in part PAAD-US samples were filtered to exclude non-PDAC samples as through transport into the mitochondria via the activity of the outlined in a previous study (6). mitochondrial pyruvate complex (MPC), comprised of pyruvate car- Somatic mutation data [those with both copy number variants – rier 1 and 2 (MPC1 and MPC2; refs. 18 20). Reduced MPC activity is (CNV) and single nucleotide variants/indels (SNV/indels) available; associated with poor prognosis in some cancer types (20). Pyruvate is a GRCh37] for all filtered samples with RNA-seq data available (PAAD- metabolic intermediate for the tricarboxylic cycle, providing the US n ¼ 60, PACA-CA n ¼ 86) were downloaded from the ICGC data precursor citrate for lipogenesis including cholesterol and free fatty portal on November 8, 2018. acid biosynthesis (9, 21). Oncogene-induced activation of the meva- lonate pathway, which is essential for de novo cholesterol synthesis and RNA-seq data processing contributes to tumor growth (22), supports the use of pathway POG RNA-seq data were aligned (GRCh37) as described previ- inhibitors such as statins in cancer. However, studies on the association ously (30). COMPASS RNA-seq reads were trimmed to 75 bp using of statins with cancer risk or survival have produced mixed fastx (hannonlab.cshl.edu/fastx_toolkit/; parameters: -l 75 -Q33) results (23–26), and statin response heterogeneity may be linked to and aligned to GRCh37 using BWA-mem v.0.7.6 (31) and JAGuaR distinct tumor molecular signatures (22, 24, 27). The association of v.2.2 (default parameters; ref. 32). Raw read counts for POG MPC1 and MPC2 expression with cancer outcomes (20) raises the and COMPASS samples were assigned to Ensembl 75 genes using possibility that intertumoral differences in pyruvate flux and the Subread v.1.4.6 (parameters: -T 3 -s 1 -C -t ‘gene‘;ref.33).POG balance between glycolysis and cholesterol synthesis could regulate and COMPASS gene expression values were RPKM normalized and þ tumor aggressiveness. PDAC cell lines have distinct glycolytic and log-transformed (log10(RPKM 1)). PAAD-US normalized gene lipogenic profiles which affect their response to metabolic agents (28); expression values were converted to transcripts per million (TPM) 6 þ however, whether gene expression heterogeneity in discrete metabolic and log-transformed (log10((normalized_count 1e ) 1)). PACA- pathways influences clinical outcome or underlies actionable meta- CA normalized gene expression values were log-transformed þ fi bolic vulnerabilities in PDAC is not completely understood. (log10(normalized_count 1)). All samples were ltered to exclude Here, we stratify PDAC into subgroups based on the expression those with tumor content values <30%. patterns of glycolytic and cholesterogenic genes, and report their association with survival, mutational, and prognostic gene expression Batch correction signatures. Data from POG, COMPASS, PAAD-US, and PACA-CA cohorts were batch-corrected using gene-wise location scaling within each Materials and Methods cohort (34). Principal component analysis of the top 25% (n ¼ 4,534) most variable genes confirmed a reduction in between-sample batch fi Patients were enrolled in the ongoing Prospectively De ning effects after normalization (Supplementary Fig. S1). Metastatic Pancreatic Ductal Adenocarcinoma Subtypes by Comprehensive Genomic Analysis (PanGen, NCT02869802), Metabolic subgrouping the BC Cancer Personalized OncoGenomics program (POG, Genesbelongingtomolecularsignaturesdatabase(mSigDB; NCT02155621), and Comprehensive Molecular Characterization ref. 35) gene sets “REACTOME_GLYCOLYSIS” (n ¼ 29) and of Advanced PDAC For Better Treatment Selection (COMPASS, “REACTOME_CHOLESTEROL_BIOSYNTHESIS” (n ¼ 24) were
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Metabolic Gene Expression Heterogeneity and Survival in PDAC
used as glycolytic and cholesterogenic genes, respectively. Consen- alternate copy number fits for each set of clusters. We then fitted a sus clustering was performed on glycolytic and cholesterogenic linear model to each set of selected clusters and computed the penalty genes using ConsensusClusterPlus (36) v1.38 (parameters: reps ¼ for each model. The penalty is an empirically derived function of the 100, pItem ¼ 0.8, pFeature ¼ 1). Ward.D2 and Euclidean distances standard error of fit, proportion of data explained by fit, and the were used as the clustering algorithm and distance metric, respec- relative proportion of predicted versus observed copy number states. tively, with k ¼ 3. Median expression levels of coexpressed glyco- Next, allelic frequencies of heterozygous germline SNPs within the lytic and cholesterogenic genes were used to assign quiescent selected clusters were used to determine the absolute copy number of (glycolytic 0, cholesterogenic 0), glycolytic (glycolytic > 0, each cluster. Assuming that all reads mapping to homozygously cholesterogenic 0), cholesterogenic (glycolytic 0, cholestero- deleted regions originate from normal tissue contamination, the genic > 0), and mixed (glycolytic > 0, cholesterogenic > 0) metabolic number of reads mapping to homozygous regions was proportional subgroups to each sample. to the normal contamination. This value was used to compute tumor content. When tumor content was not able to be predicted compu- Classification of preexisting PDAC subtypes tationally, the pathology-measured value was used. Samples were classified according to Collisson (3), Bailey (2), and Tumor content values for COMPASS and PACA-CA samples were Moffitt (4) subtypes using consensus clustering, as outlined by a determined as described previously (7). Tumor content (ABSOLUTE; previous study (7). Collisson subtyping was based on the 62 gene ref. 37) for PAAD-US samples were downloaded from the GDC data signature in the original publication (3). Bailey subtyping was based portal on February 1, 2016. For the pan-TCGA analysis, tumor content on genes from differential expression analysis results from the values were obtained from a previous publication (38). original publication (2), which were filtered for genes with an P < > adjusted 0.05 and log2 fold change 0, resulting in 240 ADEX, Mutation analysis 1,061 squamous, 268 progenitor, and 370 immunogenic genes. All mutation data were derived from hg19. SNV/indels and Moffitt subtyping was based on genes belonging to the 50 gene CNVs in POG, COMPASS, and PACA-CA samples were identified signature in the original publication (4). For each subtyping pro- as described previously (7, 30). Relative to tumor ploidy, DNA cedure, samples underwent consensus clustering based on each segments with copy state 4and 1 were considered amplifica- classifiers genes, followed by semi-automatic subtype assignment tions and deletions, respectively. PAAD-US mutation data were based on gene expression patterns (7). downloaded February 1, 2016, from the GDC data portal. PAAD- US copy number events were filtered for those with at least 10 MPC1/2 analysis supporting probes and a segment mean >0.2 (amplifications) or When comparing MPC1/2 mRNA levels between metabolic <