Method of Tissue Acquisition Affects Success of Comprehensive Genomic Profiling in Lung Cancer

CONTEXT.—

Multiple procedural techniques can be used to obtain tissue to create a formalin-fixed, paraffin-embedded specimen for comprehensive genomic profiling (CGP) in lung cancer. The literature is mixed on whether the procedure affects CGP success.

OBJECTIVE.—

To examine whether biopsy procedure affects lung cancer CGP success.

DESIGN.—

This was a cross-sectional study of all patients with lung cancer whose specimens were submitted for CGP between January and February 2020. Multiple quality control metrics were used to determine whether cases were successfully profiled.

RESULTS.—

In all, 3312 samples were identified. Overall, 67.5% (2236 of 3312) of samples were obtained from biopsies, 13.0% (432 of 3312) from fine-needle aspirations (FNAs), 9.7% (321 of 3312) from resections, 5.3% (174 of 3312) from fluid cytology cell blocks, and 4.5% (149 of 3312) from bone biopsies. Overall, 70.1% (2321 of 3312) of cases passed CGP, 15.4% (510 of 3312) of cases were released as qualified reports, and 14.5% (481 of 3312) of cases failed CGP. Resection samples were the most likely to be successfully sequenced, failing in only 2.8% (9 of 321) of instances, while fluid cytology specimens were the least likely, failing in 23.0% (40 of 174) of instances. Biopsy (14.5% [324 of 2236]), FNA (18.5% [80 of 432]), and bone biopsy (18.8% [28 of 149]) specimens failed at intermediate frequencies. On multivariate logistic regression analysis of CGP success on specimen type, fluid cytology (odds ratio [OR], 0.08; 95% CI, 0.03-0.19), biopsy (OR, 0.25; 95% CI, 0.11-0.52), FNA (OR, 0.14; 95% CI, 0.06-0.32), and bone biopsy (OR, 0.07; 95% CI, 0.03-0.17) specimens had decreased odds of CGP success relative to resection samples. Among patients with successfully sequenced samples, 48.0% were eligible for at least 1 therapy, based on a companion diagnostic or National Comprehensive Cancer Network biomarker.

CONCLUSIONS.—

The method of tissue acquisition was an important preanalytic factor that determined whether a sample would be successfully sequenced and whether a clinically actionable genomic alteration would be detected.

A Phase II Trial of Guadecitabine in Children and Adults with SDH-Deficient GIST, Pheochromocytoma, Paraganglioma, and HLRCC-Associated Renal Cell Carcinoma

PURPOSE

Succinate dehydrogenase (dSDH)-deficient tumors, including pheochromocytoma/paraganglioma, hereditary leiomyomatosis and renal cell cancer-associated renal cell carcinoma (HLRCC-RCC), and gastrointestinal stromal tumors (GIST) without KIT or platelet-derived growth factor receptor alpha mutations are often resistant to cytotoxic chemotherapy, radiotherapy, and many targeted therapies. We evaluated guadecitabine, a dinucleotide containing the DNA methyltransferase inhibitor decitabine, in these patient populations.

PATIENTS AND METHODS

Phase II study of guadecitabine (subcutaneously, 45 mg/m2/day for 5 consecutive days, planned 28-day cycle) to assess clinical activity (according to RECISTv.1.1) across three strata of patients with dSDH GIST, pheochromocytoma/paraganglioma, or HLRCC-RCC. A Simon optimal two-stage design (target response rate 30% rule out 5%) was used. Biologic correlates (methylation and metabolites) from peripheral blood mononuclear cells (PBMC), serum, and urine were analyzed.

RESULTS

Nine patients (7 with dSDH GIST, 1 each with paraganglioma and HLRCC-RCC, 6 females and 3 males, age range 18-57 years) were enrolled. Two patients developed treatment-limiting neutropenia. No partial or complete responses were observed (range 1-17 cycles of therapy). Biologic activity assessed as global demethylation in PBMCs was observed. No clear changes in metabolite concentrations were observed.

CONCLUSIONS

Guadecitabine was tolerated in patients with dSDH tumors with manageable toxicity. Although 4 of 9 patients had prolonged stable disease, there were no objective responses. Thus, guadecitabine did not meet the target of 30% response rate across dSDH tumors at this dose, although signs of biologic activity were noted.

Maternal Periconceptional Folic Acid Supplementation and DNA Methylation Patterns in Adolescent Offspring

BACKGROUND

Folate, including the folic acid form, is a key component of the one-carbon metabolic pathway used for DNA methylation. Changes in DNA methylation patterns during critical development periods are associated with disease outcomes and are associated with changes in nutritional status in pregnancy. The long-term impact of periconceptional folic acid supplementation on DNA methylation patterns is unknown.

OBJECTIVES

To determine the long-term impact of periconceptional folic acid supplementation on DNA methylation patterns, we examined the association of the recommended dosage (400 μg/d) and time period (periconceptional before pregnancy through first trimester) of folic acid supplementation with the DNA methylation patterns in the offspring at age 14-17 y compared with offspring with no supplementation.

METHODS

Two geographic sites in China from the 1993-1995 Community Intervention Program of folic acid supplementation were selected for the follow-up study. DNA methylation at 402,730 CpG sites was assessed using saliva samples from 89 mothers and 179 adolescents (89 male). The mean age at saliva collection was 40 y among mothers (range: 35-54 y) and 15 y among adolescents (range: 14-17 y). Epigenome-wide analyses were conducted to assess the interactions of periconceptional folic acid exposure, the 5,10-methylenetetrahydrofolate reductase (MTHFR)-C677T genotype, and epigenome-wide DNA methylation controlling for offspring sex, geographic region, and background cell composition in the saliva.

RESULTS

In the primary outcome, no significant differences were observed in epigenome-wide methylation patterns between adolescents exposed and those non-exposed to maternal periconceptional folic acid supplementation after adjustment for potential confounders [false discovery rate (FDR) P values < 0.05]. The MTHFR-C677T genotype did not modify this lack of association (FDR P values < 0.05).

CONCLUSIONS

Overall, there were no differences in DNA methylation between adolescents who were exposed during the critical developmental window and those not exposed to the recommended periconceptional/first-trimester dosage of folic acid.

PATH-14. MOLECULAR ANALYSIS OF ASTROCYTOMAS WITH A DOMINANT PILOMYXOID MORPHOLOGY

Pilomyxoid astrocytomas (PMAs) are tumors of infancy occurring in the hypothalamic chiasmatic region, with somewhat worse prognosis than pilocytic astrocytomas (PAs). We report molecular findings in PAs with a dominant pilomyxoid histomorphology across the various age groups and CNS locations. Foundation Medicine comprehensive genomic profiling (CGP) (FoundationOne, FoundationOneCDx, FoundationOneHeme) were performed during routine clinical care. A retrospective cohort analysis was done to evaluate the genomic characteristics of PMAs. 57 PMAs were identified, of which 6 occurred in patients &lt; 12 months old (10.5%); 14 in 1-3 year old (24.6%); 15 in 4-10 y.o. (26.3%); 12 in 11-20 y.o. (21.1%), and 10 occurred in young adults 21-39 y.o. (17.5%). 30/57 (52.6%) were female and 27/57 (47.4%) male. 55 PMAs occurred in the brain and 2 in the spinal cord. Tumors were categorized by notable rearrangements and point mutations. The common fusion, KIAA1549:BRAF, was detected in 23/57 samples (40.4%). BRAF fusions with other gene partners (BRAF, TAX1BP1) occurred in 2, and BRAF V600E mutations in 4 patients. An additional 4 patients had FGFR1 fusions (FGFR1, TACC1) and 14 had FGFR mutations. Other alterations included 3 NF1 mutations, 2 NTRK family receptor tyrosine kinase fusions, 2 RAF gene fusions, 2 other (ATRX, ALK) alterations, and 1 VUS. Tumor Mutational Burden was under 10 mut/Mb for all patients. In this cohort of 57 PMAs, MAPK pathway genetic alterations were dominant drivers, similar to other PAs. We also observed other frequent genetic alterations not involving BRAF, including FGFR and NTRK gene family members that have FDA approved targeted inhibitors. While these also likely cause MAPK pathway activation, these non-BRAF variants are less common in PAs. Our report contributes to growing evidence that PMAs harbor a distinct molecular alteration profile, which is becoming increasingly important in the context of the evolving targeted therapeutics landscape.

Characterization of genetically defined sporadic and hereditary type 1 papillary renal cell carcinoma cell lines

Renal cell carcinoma (RCC) is not a single disease but is made up of several different histologically defined subtypes that are associated with distinct genetic alterations which require subtype specific management and treatment. Papillary renal cell carcinoma (pRCC) is the second most common subtype after conventional/clear cell RCC (ccRCC), representing ~20% of cases, and is subcategorized into type 1 and type 2 pRCC. It is important for preclinical studies to have cell lines that accurately represent each specific RCC subtype. This study characterizes seven cell lines derived from both primary and metastatic sites of type 1 pRCC, including the first cell line derived from a hereditary papillary renal carcinoma (HPRC)‐associated tumor. Complete or partial gain of chromosome 7 was observed in all cell lines and other common gains of chromosomes 16, 17, or 20 were seen in several cell lines. Activating mutations of MET were present in three cell lines that all demonstrated increased MET phosphorylation in response to HGF and abrogation of MET phosphorylation in response to MET inhibitors. CDKN2A loss due to mutation or gene deletion, associated with poor outcomes in type 1 pRCC patients, was observed in all cell line models. Six cell lines formed tumor xenografts in athymic nude mice and thus provide in vivo models of type 1 pRCC. These type 1 pRCC cell lines provide a comprehensive representation of the genetic alterations associated with pRCC that will give insight into the biology of this disease and be ideal preclinical models for therapeutic studies.

Abstract GMM-025: ERBB FAMILY GENOMIC ALTERATIONS IN GYNECOLOGICAL MALIGNANCIES

Activation of HER2 or EGFR signaling is a common, targetable oncogenic mechanism in solid tumors such as breast, gastroesophageal, lung and colorectal carcinomas. In addition, ERBB3 activation has been shown to confer sensitivity to HER2-targeted therapies, and ERBB4 mutation is reported a mechanism of resistance. From a database of 14,692 comprehensive genomic profiles for both common and rare gynecological malignancies, we extracted 9,121 ovarian tumor profiles and evaluated the prevalence of genomic alterations (GA) in the ERBB family (EGFR, ERBB2, ERBB3, ERBB4), including base substitutions, small indels, amplification (AMP), and rearrangements (RE).

At least 50ng of DNA was extracted from FFPE specimens and sequenced to high, uniform median coverage (&gt;500X) by hybridization capture of exons from up to 406 cancer-related genes and select introns from up to 31 genes commonly rearranged in cancer. For some samples, RNA sequencing of 265 genes was also performed. Tumor mutational burden (TMB, mutations/Mb [mut/Mb]) was determined on ~1.1 Mbp of sequenced DNA, and microsatellite instability (MSI) and overall genomic loss of heterozygosity was evaluated for subsets of the samples.

Of 9,121 tumors, most were serous carcinomas (n = 6,847). A total of 615 (6.7%) tumors had ≥1 oncogenic GA in an ERBB gene, with 40 (0.4%) having ≥2 ERBB GA. ERBB+ were most often mucinous (15.9%) or clear cell (13.9%) carcinomas. Serous carcinomas were ERBB+ in 4.3-7.1% of samples. Patient age was comparable in both the ERBB+ and ERBB- tumors (median 61 y vs. 61 y, range 19-94 y vs. 2-95 y).

ERBB2 (HER2) AMP was the most common ERBB GA; 2.7% of serous carcinomas had amplified ERBB2. GA distribution by ERBB gene was as follows: ERBB2 4.5% (n=394; of those AMP were 78.4%, n=309), ERBB3 0.8% (n=87; AMP 50.6%, n=44), EGFR 0.9% (n=90; AMP 45.6%, n=41), and ERBB4 0.6% (n=66; AMP 65.1%, n=43). Known or potential oncogenic rearrangements, fusions, and splice site GA were observed in both ERBB2 (n=20) and EGFR (n=10), including a kinase domain duplication in EGFR and exon 16 deletions in ERBB2. Although ERBB2 AMP is concordant with HER2+ by IHC or FISH, 70/615 (11.4%) HER2-driven samples harbored targetable, oncogenic GA that would not be detected by these methods, including the well-characterized A775_G776insYVMA (n=13), S310Y/F (n=10), and V842I (n=8).

In ERBB+ tumors, the most commonly co-occurring GA affected TP53 (76.6%), PIK3CA (19.5%), MYC (15.7%), TERC (14.6%), ARID1A (18.3%), and CCNE1 (20.5%). Pathways likely to confer some level of resistance to ERBB-targeted therapies were often mutated: PI3K-AKT-MTOR 35.0% (n=215), RAS-RAF-MEK 18.2% (n=112), and FGFR 5.5% (n=34). ERBB+ tumors had slightly higher TMB scores: median 3.5 mut/Mb vs 2.6 mut/Mb, and average 6.7 vs 3.7 mut/Mb. Of 502 samples analyzed for microsatellite instability, 12 were MSI high. In conclusion, nearly 7% of ovarian tumors harbor potentially targetable GA in an ERBB family gene, including HER2 and EGFR. Of these, 49.6% of samples would not be positive by HER2 IHC or FISH. Further exploration into the efficacy of HER2- or EGFR-targeted therapies, and the effects of co-altered pathways, in ovarian carcinomas may be promising.

Citation Format: Laurie M Gay, Jo-Anne Vergilio, J Keith Killian, Shakti Ramkissoon, Eric Severson, Sugganth Daniel, Amanda Hemmerich, Jeffrey S Ross, Julia A Elvin. ERBB FAMILY GENOMIC ALTERATIONS IN GYNECOLOGICAL MALIGNANCIES [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-025.

A Phase II Trial of Vandetanib in Children and Adults with Succinate Dehydrogenase-Deficient Gastrointestinal Stromal Tumor

PURPOSE

Gastrointestinal stromal tumors (GIST) are resistant to cytotoxic chemotherapy and radiotherapy. Most GIST in children are wild-type for KIT and PDGFRA (WT GIST) and deficient in expression of succinate dehydrogenase (dSDH GIST). We tested the activity of vandetanib, an oral small-molecule inhibitor of VEGFR2, EGFR, and RET, in patients with dSDH GIST.

PATIENTS AND METHODS

Phase II study of vandetanib (300 mg orally once daily to patients ≥18 years, and 100 mg/m²/dose to patients < 18 years) on a continuous dosing schedule (1 cycle = 28 days) to assess the clinical activity (partial and complete response rate RECIST v1.1) in patients with dSDH GIST. A Simon optimal two-stage design (target response rate 25%, rule out 5%) was used: If ≥1 of 9 patients in stage 1 responded, enrollment would be expanded to 24 patients, and if ≥3 of 24 responded, vandetanib would be considered active.

RESULTS

Nine patients (7 female and 2 male; median age, 24 years; range, 11-52) with metastatic disease were enrolled. Three of the initial 5 adult patients developed treatment-modifying toxicities. After a protocol amendment, two adults received vandetanib at 200 mg/dose with improved tolerability. The two children (<18 years old) enrolled did not experience treatment-modifying toxicities. No partial or complete responses were observed (median number of cycles, 4; range, 2-18).

CONCLUSIONS

Vandetanib at a dose of 300 mg daily was not well tolerated by adults with dSDH GIST. Two of 9 patients had prolonged stable disease, but no partial or complete responses were observed, and vandetanib is thus not considered active in dSDH GIST.

ONCOGENE PANEL SEQUENCING ANALYSIS IDENTIFIES CANDIDATE ACTIONABLE GENES IN ADVANCED WELL-DIFFERENTIATED GASTROENTEROPANCREATIC NEUROENDOCRINE TUMORS

Objective: To report the rate of candidate actionable somatic mutations in patients with locally advanced and metastatic gastro-enteropancreatic (GEP) neuroendocrine tumors (NET) and of other genetic alterations that may be associated with tumorigenesis. Methods: A phase II mutation targeted therapy trial was conducted in patients with advanced well-differentiated G1/G2 GEP-NET. Mutations found in the mTOR pathway-associated genes led to treatment with the mTOR inhibitor everolimus, and were defined as actionable. Tumor deoxyribonucleic acid (DNA) from GEP-NET were sequenced and compared with germline DNA, using the OncoVAR-NET assay, designed for hybrid capture sequencing of 500 tumor suppressor genes and oncogenes. Somatic variants were called and copy-number (CN) variant analysis was performed. Results: Thirty patients (14 small-intestine, 8 pancreatic, 3 unknown primary NET, and 5 of other primary sites) harbored 37 lesions (4 patients had DNA of multiple lesions sequenced). Only 2 patients with sporadic NET (n = 26) had an actionable mutation leading to treatment with everolimus. Driver somatic mutations were detected in 18 of 30 patients (21/37 lesions sequenced). In the remaining samples without a driver mutation, CN alterations were found in 11/16 tumors (10/12 patients), including CN loss of chromosome (Chr) 18 (P<.05), CN gain of Chr 5, and loss of Chr 13. CN losses in Chr 18 were more common in patients without driver mutations detected. Pronounced genetic heterogeneity was detected in patients with multiple lesions sequenced. Conclusion: Genome-wide DNA sequencing may identify candidate actionable genes and lead to the identification of novel target genes for advanced well-differentiated GEP-NET. Abbreviations: Chr = chromosome; CN = copy number; DNA = deoxyribonucleic acid; FDA = Food and Drug Administration; GEP = gastro-enteropancreatic; MEN-1 = multiple endocrine neoplasia syndrome type 1; mTOR = mammalian target of rapamycin; NET = neuroendocrine tumor; PFS = progression-free survival; PNET = pancreatic neuroendocrine tumors; SINET = small-intestine neuroendocrine tumor.

Molecular Classification of Epithelial Ovarian Cancer Based on Methylation Profiling: Evidence for Survival Heterogeneity

PURPOSE

Ovarian cancer is a heterogeneous disease that can be divided into multiple subtypes with variable etiology, pathogenesis, and prognosis. We analyzed DNA methylation profiling data to identify biologic subgroups of ovarian cancer and study their relationship with histologic subtypes, copy number variation, RNA expression data, and outcomes.

EXPERIMENTAL DESIGN

A total of 162 paraffin-embedded ovarian epithelial tumor tissues, including the five major epithelial ovarian tumor subtypes (high- and low-grade serous, endometrioid, mucinous, and clear cell) and tumors of low malignant potential were selected from two different sources: The Polish Ovarian Cancer study, and the Surveillance, Epidemiology, and End Results Residual Tissue Repository (SEER RTR). Analyses were restricted to Caucasian women. Methylation profiling was conducted using the Illumina 450K methylation array. For 45 tumors array copy number data were available. NanoString gene expression data for 39 genes were available for 61 high-grade serous carcinomas (HGSC).

RESULTS

Consensus nonnegative matrix factorization clustering of the 1,000 most variable CpG sites showed four major clusters among all epithelial ovarian cancers. We observed statistically significant differences in survival (log-rank test, P = 9.1 × 10^-7) and genomic instability across these clusters. Within HGSC, clustering showed three subgroups with survival differences (log-rank test, P = 0.002). Comparing models with and without methylation subgroups in addition to previously identified gene expression subtypes suggested that the methylation subgroups added significant survival information (P = 0.007).

CONCLUSIONS

DNA methylation profiling of ovarian cancer identified novel molecular subgroups that had significant survival difference and provided insights into the molecular underpinnings of ovarian cancer.See related commentary by Ishak et al., p. 5729.

Abstract P3-06-18: Comprehensive genomic profiling of carcinosarcomas of the breast

Background:

Carcinosarcomas of the breast (BCSC) are exceptionally rare and the underlying genomic drivers are still being elucidated. Comprehensive genomic profiling (CGP) determines the tumor mutation burden (TMB) and identifies all four classes of genomic alterations (GA) that have potential to direct personalized treatment strategies.

Methods:

CGP by hybridization capture of exons from up to 315 cancer-related genes and select introns of 28 genes commonly rearranged in cancer was applied to ≥ 50ng of DNA extracted from 9 consecutive BCSC and sequenced to high, uniform median coverage (&gt;500X). Tumor mutational burden (TMB) was determined on 1.1 Mbp of sequenced DNA and microsatellite instability (MSI) was determined by principal components analysis of optimized loci.

Results:

The 9 BCSC patients had a median age of 57 yrs (range 49-78 yrs). CGP was performed on the primary BCSC in 4 cases and on metastasis biopsies in 5 cases (4 lung and 1 lymph node). The mean GA/tumor was 6.6 and clinically relevant GA (CRGA)/tumor was 1.3. The most frequent non-CRGA were in TP53 (89%), MYC (56%) and LYN (40%). The most frequent CRGA were in PIK3CA (33%), and NF1, BRCA1, PTEN, RICTOR, FGFR1, AKT2 and STK11 (all at 11%). The median TMB for all BCSC was 2.4 mut/Mb with 1 (11%) tumor with a TMB &gt; 20 mut/Mb and 8 BCSC (88%) with TMB &lt; 5 mut/Mb. Five of 5 BCSC (100%) that were available for MSI status testing were microsatellite stable.

Conclusions:

On CGP, BCSC feature a high frequency of GA, but only a modest frequency of CRGA and high TMB. However, when the CRGA and TMB positive cases are combined (77.8% overall in this series), the opportunity for personalized targeted and immunotherapies are significant. Thus, further investigation of precision therapies for BCSC in the clinical trial setting appear warranted.

Citation Format: Gay LM, Elvin JA, Vergilio J-A, Killian JK, Ramkissoon S, Severson E, Daniel S, Hammerich A, Sokol E, Frampton G, Chung J, Trabucco S, Ali S, Reddy P, Schrock AB, Miller VA, Ross JS. Comprehensive genomic profiling of carcinosarcomas of the breast [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-06-18.

CDC73 Germline Mutation in a Family With Mixed Epithelial and Stromal Tumors

OBJECTIVE

To describe a family in which 3 members presented with mixed epithelial tumor of the kidney (MEST) and were found to possess a germline mutation in CDC73, a gene which is associated with hyperparathyroidism-jaw tumor syndrome (HPT-JT).

MATERIALS AND METHODS

Blood and tumor DNA from three family members who presented with a primary diagnosis of MEST was subjected to targeted gene sequencing to identify potential genetic components.

RESULTS

A germline start codon mutation (p.M1I) in CDC73 was identified in all 3 family members who presented with MEST and 2 tumors from 1 patient demonstrated somatic copy-neutral loss of heterozygosity. Patients presented with no evidence of hyperparathyroidism or jaw tumors, but both female patients had hysterectomies at an early age due to excessive bleeding and numerous fibroids, which is common in HPT-JT. A germline p.M1I mutation has been previously reported in a family with clinical features of HPT-JT.

CONCLUSION

Patients with MEST may be at risk for HPT-JT and CDC73 germline mutation testing of MEST patients should be considered.

Characterization of BK Polyomaviruses from Kidney Transplant Recipients Suggests a Role for APOBEC3 in Driving In-Host Virus Evolution

BK polyomavirus (BKV) frequently causes nephropathy (BKVN) in kidney transplant recipients (KTRs). BKV has also been implicated in the etiology of bladder and kidney cancers. We characterized BKV variants from two KTRs who developed BKVN followed by renal carcinoma. Both patients showed a swarm of BKV sequence variants encoding non-silent mutations in surface loops of the viral major capsid protein. The temporal appearance and disappearance of these mutations highlights the intra-patient evolution of BKV. Some of the observed mutations conferred resistance to antibody-mediated neutralization. The mutations also modified the spectrum of receptor glycans engaged by BKV during host cell entry. Intriguingly, all observed mutations were consistent with DNA damage caused by antiviral APOBEC3 cytosine deaminases. Moreover, APOBEC3 expression was evident upon immunohistochemical analysis of renal biopsies from KTRs. These results provide a snapshot of in-host BKV evolution and suggest that APOBEC3 may drive BKV mutagenesis in vivo.

Aneuploidy, TP53 mutation, and amplification of MYC correlate with increased intratumor heterogeneity and poor prognosis of breast cancer patients

The clinical course of breast cancer varies from one patient to another. Currently, the choice of therapy relies on clinical parameters and histological and molecular tumor features. Alas, these markers are informative in only a subset of patients. Therefore, additional predictors of disease outcome would be valuable for treatment stratification. Extensive studies showed that the degree of variation of the nuclear DNA content, i.e., aneuploidy, determines prognosis. Our aim was to further elucidate the molecular basis of aneuploidy. We analyzed five diploid and six aneuploid tumors with more than 20 years of follow-up. By performing FISH with a multiplexed panel of 10 probes to enumerate copy numbers in individual cells, and by sequencing 563 cancer-related genes, we analyzed how aneuploidy is linked to intratumor heterogeneity. In our cohort, none of the patients with diploid tumors died of breast cancer during follow-up in contrast to four of six patients with aneuploid tumors (mean survival 86.4 months). The FISH analysis showed markedly increased genomic instability and intratumor heterogeneity in aneuploid tumors. MYC gain was observed in only 20% of the diploid cancers, while all aneuploid cases showed a gain. The mutation burden was similar in diploid and aneuploid tumors, however, TP53 mutations were not observed in diploid tumors, but in all aneuploid tumors in our collective. We conclude that quantitative measurements of intratumor heterogeneity by multiplex FISH, detection of MYC amplification and TP53 mutation could augment prognostication in breast cancer patients.

ADHFE1 is a breast cancer oncogene and induces metabolic reprogramming

Metabolic reprogramming in breast tumors is linked to increases in putative oncogenic metabolites that may contribute to malignant transformation. We previously showed that accumulation of the oncometabolite, 2-hydroxyglutarate (2HG), in breast tumors was associated with MYC signaling, but not with isocitrate dehydrogenase (IDH) mutations, suggesting a distinct mechanism for increased 2HG in breast cancer. Here, we determined that D-2HG is the predominant enantiomer in human breast tumors and show that the D-2HG-producing mitochondrial enzyme, alcohol dehydrogenase, iron-containing protein 1 (ADHFE1), is a breast cancer oncogene that decreases patient survival. We found that MYC upregulates ADHFE1 through changes in iron metabolism while coexpression of both ADHFE1 and MYC strongly enhanced orthotopic tumor growth in MCF7 cells. Moreover, ADHFE1 promoted metabolic reprogramming with increased formation of D-2HG and reactive oxygen, a reductive glutamine metabolism, and modifications of the epigenetic landscape, leading to cellular dedifferentiation, enhanced mesenchymal transition, and phenocopying alterations that occur with high D-2HG levels in cancer cells with IDH mutations. Together, our data support the hypothesis that ADHFE1 and MYC signaling contribute to D-2HG accumulation in breast tumors and show that D-2HG is an oncogenic metabolite and potential driver of disease progression.

DNA Methylation-Based Classifier for Accurate Molecular Diagnosis of Bone Sarcomas

Purpose

Pediatric sarcomas provide a unique diagnostic challenge. There is considerable morphologic overlap between entities, increasing the importance of molecular studies in the diagnosis, treatment, and identification of therapeutic targets. We developed and validated a genome-wide DNA methylation based classifier to differentiate between osteosarcoma, Ewing's sarcoma, and synovial sarcoma.

Materials and Methods

DNA methylation status of 482,421 CpG sites in 10 Ewing's sarcoma, 11 synovial sarcoma, and 15 osteosarcoma samples were determined using the Illumina Infinium HumanMethylation450 array. We developed a random forest classifier trained from the 400 most differentially methylated CpG sites within the training set of 36 sarcoma samples. This classifier was validated on data drawn from The Cancer Genome Atlas (TCGA) synovial sarcoma, TARGET Osteosarcoma, and a recently published series of Ewing's sarcoma.

Results

Methylation profiling revealed three distinct patterns, each enriched with a single sarcoma subtype. Within the validation cohorts, all samples from TCGA were accurately classified as synovial sarcoma (10/10, sensitivity and specificity 100%), all but one sample from TARGET-OS were classified as osteosarcoma (85/86, sensitivity 98%, specificity 100%) and 14/15 Ewing's sarcoma samples classified correctly (sensitivity 93%, specificity 100%). The single misclassified osteosarcoma sample demonstrated high EWSR1 and ETV1 expression on RNA-seq although no fusion was found on manual curation of the transcript sequence. Two additional clinical samples, that were difficult to classify by morphology and molecular methods, were classified as osteosarcoma when previously suspected to be a synovial sarcoma and Ewing's sarcoma on initial diagnosis, respectively.

Conclusion

Osteosarcoma, synovial sarcoma, and Ewing's sarcoma have distinct epigenetic profiles. Our validated methylation-based classifier can be used to provide diagnostic assistance when histological and standard techniques are inconclusive.

Genomic and metabolic characterization of a chromophobe renal cell carcinoma cell line model (UOK276)

Chromophobe renal cell carcinoma (ChRCC) represents 5% of all RCC cases and frequently demonstrates multiple chromosomal losses and an indolent pattern of local growth, but can demonstrate aggressive features and resistance to treatment in a metastatic setting. Cell line models are an important tool for the investigation of tumor biology and therapeutic drug efficacy. Currently, there are few ChRCC-derived cell lines and none is well characterized. This study characterizes a novel ChRCC-derived cell line model, UOK276. A large ChRCC tumor with regions of sarcomatoid differentiation was used to establish a spontaneously immortal cell line, UOK276. UOK276 was evaluated for chromosomal, mutational, and metabolic aberrations. The UOK276 cell line is hyperdiploid with a modal number of 49 chromosomes per cell, and evidence of copy-neutral loss of heterozygosity, as opposed to the classic pattern of ChRCC chromosomal losses. UOK276 demonstrated a TP53 missense mutation, expressed mutant TP53 protein, and responded to treatment with a small-molecule therapeutic agent, NSC319726, designed to reactivate mutated TP53. Xenograft tumors grew in nude mice and provide an in vivo animal model for the investigation of potential therapeutic regimes. The xenograft pathology and genetic analysis suggested that UOK276 was derived from the sarcomatoid region of the original tumor. In summary, UOK276 represents a novel in vitro and in vivo cell line model for aggressive, sarcomatoid-differentiated, TP53 mutant ChRCC. This preclinical model system could be used to investigate the novel biology of aggressive, sarcomatoid ChRCC and evaluate the new therapeutic regimes.

Molecular Subtypes of KIT/PDGFRA Wild-Type Gastrointestinal Stromal Tumors: A Report From the National Institutes of Health Gastrointestinal Stromal Tumor Clinic

IMPORTANCE

Wild-type (WT) gastrointestinal stromal tumors (GISTs), which lack KIT and PDGFRA gene mutations, are the primary form of GIST in children and occasionally occur in adults. They respond poorly to standard targeted therapy. Better molecular and clinical characterization could improve management.

OBJECTIVE

To evaluate the clinical and tumor genomic features of WT GIST.

DESIGN, SETTING, AND PARTICIPANTS

Patients enrolled in an observational study at the National Institutes of Health starting in 2008 and were evaluated in a GIST clinic held once or twice yearly. Patients provided access to existing medical records and tumor specimens. Self-referred or physician-referred patients younger than 19 years with GIST or 19 years or older with known WT GIST (no mutations in KIT or PDGFRA) were recruited; 116 patients with WT GIST were enrolled, and 95 had adequate tumor specimen available. Tumors were characterized by immunohistochemical analysis (IHC) for succinate dehydrogenase (SDH) subunit B, sequencing of SDH genes, and determination of SDHC promoter methylation. Testing of germline SDH genes was offered to consenting patients and families.

MAIN OUTCOMES AND MEASURES

For classification, tumors were characterized by SDHA, B, C, or D (SDHX) mutations and other genetic and epigenetic alterations, including presence of mutations in germline. Clinical characteristics were categorized.

RESULTS

Wild-type GIST specimens from 95 patients (median age, 23 [range, 7-78] years; 70% female) were classified into 3 molecular subtypes: SDH-competent (n = 11), defined by detection of SDHB by IHC; and 2 types of SDH-deficient GIST (n = 84). Of SDH-deficient tumors, 63 (67%) had SDH mutations, and in 31 of 38 (82%), the SDHX mutation was also present in germline. Twenty-one (22%) SDH-deficient tumors had methylation of the SDHC promoter leading to silencing of expression. Mutations in known cancer-associated pathways were identified in 9 of 11 SDH-competent tumors. Among patients with SDH-mutant tumors, 62% were female (39 of 63), median (range) age was 23 (7-58) years, and approximately 30% presented with metastases (liver [12 of 58], peritoneal [6 of 58], lymph node [15 of 23]). SDHC-epimutant tumors mostly affected young females (20 of 21; median [range] age, 15 [8-50] years), and approximately 40% presented with metastases (liver [7 of 19], peritoneal [1 of 19], lymph node [3 of 8]). SDH-deficient tumors occurred only in the stomach and had an indolent course.

CONCLUSIONS AND RELEVANCE

An observational study of WT GIST permitted the evaluation of a large number of patients with this rare disease. Three molecular subtypes with implications for prognosis and clinical management were identified.

Abstract IS01: METHYLATION PROFILING OF OVARIAN CANCER TO STUDY ETIOLOGIC AND PROGNOSTIC HETEROGENEITY AND TO DEVELOP A MOLECULAR CLASSIFIER

BACKGROUND. Ovarian cancer is a heterogeneous disease that is divisible into multiple subtypes with variable pathogenesis, etiology and biological behavior. We analyzed DNA methylation profiling data to identify biologic subgroups of ovarian cancer and study their relationship with histologic subtypes and prognosis. Additionally, we developed a molecular classifier for classification of ovarian tumors in epidemiologic studies.

METHODS. A total of 176 paraffin embedded ovarian epithelial tumor tissues, including the four major epithelial ovarian tumor subtypes (serous, endometrioid, mucinous and clear cell) and tumors of low malignant potential (LMP) were selected from two different sources: The Polish Ovarian Cancer study, an incident population–based case–control study conducted from 2001–2004, and the Surveillance, Epidemiology, and End Results Residual Tissue Repository (SEER RTR), which included ovarian tumors blocks collected between 1994 and 2004 from the Iowa and Hawaii SEER registries. The distributions of tumor histologic subtypes and grades from the studies were similar. All analyses were restricted to Caucasian women. Methylation profiling was conducted using the Illumina 450K methylation array. Analyses were restricted to the 22 autosomal chromosomes and non–SNP probes. Fourteen samples that did not pass quality control were excluded from the analysis.

RESULTS. Among 162 samples, 32 were from the Polish study and 130 were from the SEER RTR. Unsupervised hierarchical clustering of the 5,000 most variable CpG sites showed 4 major clusters: Cluster 1 with 79% invasive serous and 14% endometrioid carcinomas, including the majority of high grade carcinomas; cluster 2 with 77% either endometrioid or clear cell carcinomas; cluster 3 with 71% serous LMP; and cluster 4 with 73% mucinous carcinomas. We observed significant survival differences across these clusters (long–rank test P= 4.27×10–6), similar to differences observed for histologic subtypes. Within high grade (HG) serous carcinomas, clustering showed three subgroups with prognostic significance (long–rank test P= 0.008).

CONCLUSIONS. Our results suggest that methylation–based subtypes provide a classification of ovarian tumors that are in agreement with morphologic subtypes and probable mechanisms of origin. Unsupervised clustering analysis of HG serous carcinomas showed subtypes within HG serous with significance survival difference. Ongoing analyses will compare performance of the methylation classifier with histologic subtype in relation to risk factors and prognosis.

Citation Format: Clara Bodelon, J. Keith Killian, Joshua N. Sampson, Holly Stevenson, William F. Anderson, Rayna Matsuno, Louise A. Brinton, Jolanta Lissowska, Mark E. Sherman, Nicolas Wentzensen. METHYLATION PROFILING OF OVARIAN CANCER TO STUDY ETIOLOGIC AND PROGNOSTIC HETEROGENEITY AND TO DEVELOP A MOLECULAR CLASSIFIER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr IS01.

Discovery and validation of candidate host DNA methylation markers for detection of cervical precancer and cancer

Human papillomavirus (HPV) testing has been recently introduced as an alternative to cytology for cervical cancer screening. However, since most HPV infections clear without causing clinically relevant lesions, additional triage tests are required to identify women who are at high risk of developing cancer. We performed DNA methylation profiling on formalin-fixed, paraffin-embedded tissue specimens from women with benign HPV16 infection and histologically confirmed cervical intraepithelial neoplasia grade 3, and cancer using a bead-based microarray covering 1,500 CpG sites in over 800 genes. Methylation levels in individual CpG sites were compared using a t-test, and results were summarized by computing p-values. A total of 12 candidate genes (ADCYAP1, ASCL1, ATP10, CADM1, DCC, DBC1, HS3ST2, MOS, MYOD1, SOX1, SOX17 and TMEFF2) identified by DNA methylation profiling, plus an additional three genes identified from the literature (EPB41L3, MAL and miR-124) were chosen for validation in an independent set of 167 liquid-based cytology specimens using pyrosequencing and targeted, next-generation bisulfite sequencing. Of the 15 candidate gene markers, 10 had an area under the curve (AUC) of ≥ 0.75 for discrimination of high grade squamous intraepithelial lesions or worse (HSIL+) from <HSIL cytology using at least one assay. Overall, SOX1, DCC, and EPB41L3 showed the best discrimination with AUC values of ≥0.80, irrespective of methylation detection assay. In addition to verifying candidate markers from the literature (e.g., SOX1 and EPB41L3), we identified novel markers that may be considered for detection of cervical precancer and cancer and warrant further validation in prospective studies.

Imprints and DPPA3 are bypassed during pluripotency- and differentiation-coupled methylation reprogramming in testicular germ cell tumors

Testicular germ cell tumors (TGCTs) share germline ancestry but diverge phenotypically and clinically as seminoma (SE) and nonseminoma (NSE), the latter including the pluripotent embryonal carcinoma (EC) and its differentiated derivatives, teratoma (TE), yolk sac tumor (YST), and choriocarcinoma. Epigenomes from TGCTs may illuminate reprogramming in both normal development and testicular tumorigenesis. Herein we investigate pure-histological forms of 130 TGCTs for conserved and subtype-specific DNA methylation, including analysis of relatedness to pluripotent stem cell (ESC, iPSC), primordial germ cell (PGC), and differentiated somatic references. Most generally, TGCTs conserve PGC-lineage erasure of maternal and paternal genomic imprints and DPPA3 (also known as STELLA); however, like ESCs, TGCTs show focal recurrent imprinted domain hypermethylation. In this setting of shared physiologic erasure, NSEs harbor a malignancy-associated hypermethylation core, akin to that of a diverse cancer compendium. Beyond these concordances, we found subtype epigenetic homology with pluripotent versus differentiated states. ECs demonstrate a striking convergence of both CpG and CpH (non-CpG) methylation with pluripotent states; the pluripotential methyl-CpH signature crosses species boundaries and is distinct from neuronal methyl-CpH. EC differentiation to TE and YST entails reprogramming toward the somatic state, with loss of methyl-CpH but de novo methylation of pluripotency loci such as NANOG. Extreme methyl-depletion among SE reflects the PGC methylation nadir. Adjacent to TGCTs, benign testis methylation profiles are determined by spermatogenetic proficiency measured by Johnsen score. In sum, TGCTs share collective entrapment in a PGC-like state of genomic-imprint and DPPA3 erasure, recurrent hypermethylation of cancer-associated targets, and subtype-dependent pluripotent, germline, or somatic methylation.

Optimizing Workflows and Processing of Cytologic Samples for Comprehensive Analysis by Next-Generation Sequencing: Memorial Sloan Kettering Cancer Center Experience

The value and suitability of cytology specimens for molecular diagnosis has been demonstrated by numerous studies. In practice, however, the success rates vary widely across institutions depending on the disease setting, institutional practices of acquisition, handling/processing, and testing methodologies. As the number of clinically relevant biomarkers continues to increase, more laboratories are turning to next-generation sequencing platforms for testing. Although amplicon-based next-generation sequencing assays, interrogating a limited genomic territory, can be performed with minimal input material, broader-based next-generation sequencing assays have higher DNA input requirements that may not be met if the small tissue samples are not acquired and handled appropriately. We briefly describe some of the process changes we have instituted in our laboratories when handling cytologic material to maximize the tissue available for broad hybrid-capture-based next-generation sequencing assays. Among the key changes established were the consolidation and preservation of previously discarded supernatant material in cytologic samples, the introduction of mineral oil for deparaffinization of cell blocks, and adjustments in the molecular laboratory process and bioinformatics pipelines. We emphasize that even minimal changes can have broad implications for test performance, highlighting the importance of a cohesive group-based approach among clinical, cytopathology, surgical pathology, molecular, and bioinformatics teams.

Abstract 2660: A renal CpG island methylator phenotype (R-CIMP) in kidney tumors associated with germline mutations of FH and SDHB

Germline mutations of the genes encoding the Krebs cycle enzymes fumarate hydratase (FH) and succinate dehydrogenase (SDHB, SDHC, SDHD) have both been associated with an increased risk of renal cell carcinoma (RCC). These renal tumors demonstrate complete loss of enzyme activity and significantly increased levels of intracellular fumarate or succinate that are predicted to infer with the actions of multiple cellular processes primarily through the inhibition of 2-oxoglutarate-dependent dioxygenases, such as the prolyl hydroxylases that regulate the HIF pathway and the TET enzymes that regulate DNA methylation.

This study evaluated and compared the genome-wide methylation profiles of 33 tumor samples (including 9 FH -/- and 7 SDHB -/- tumors), 10 associated normal samples and 13 cell-lines (including cell-line models derived from FH -/- and SDHB -/- tumors) using the Illumina HumanMethylation450 BeadChip arrays. Tumors derived from patients

with germline FH or SDHB mutations demonstrated a distinct pattern of hypermethylation across the genome with enrichment for hypermethylation within the CpG island regions. SDHB mutation associated tumors demonstrated that was more variable and less extensive pattern of hypermethylation than the tumors associated with germline FH mutations. Cell-line models derived from HLRCC or SDHB tumors demonstrated patterns of hypermethylation similar to the patterns observed in the tumors, yet re-expression of either wild-type FH or SDHB within these cell-line models did not alter the methylation profiles. All the HLRCC and SDHB-RCC cell lines, including the cell-line re-expressing of either wild-type FH or SDHB, demonstrated growth inhibition and reduced invasion rates in response to treatment with 5-aza-2′-deoxycytidine.

Thus, renal cell carcinomas associated with FH or SDHB germline mutation demonstrate a specific R-CIMP hypermethylation profile that differentiates these tumors from tumors derived from other RCC susceptibility syndromes. These tumors represent the most aggressive

types of familial-associated RCC and this could provide a useful biomarker for identifying these tumors and de-methylating agents, such as 5-aza-2′-deoxycytidine, may be effective as part of a therapeutic regime for the treatment of these tumors.

Citation Format: Christopher Ricketts, J. Keith Killian, Cathy D. Vocke, Carole Sourbier, Youfeng Yang, Maria J. Merino, Paul S. Meltzer, W. Marston Linehan. A renal CpG island methylator phenotype (R-CIMP) in kidney tumors associated with germline mutations of FH and SDHB. [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 2660.

Whole Genome Sequencing of Newly Established Pancreatic Cancer Lines Identifies Novel Somatic Mutation (c.2587G>A) in Axon Guidance Receptor Plexin A1 as Enhancer of Proliferation and Invasion

The genetic profile of human pancreatic cancers harbors considerable heterogeneity, which suggests a possible explanation for the pronounced inefficacy of single therapies in this disease. This observation has led to a belief that custom therapies based on individual tumor profiles are necessary to more effectively treat pancreatic cancer. It has recently been discovered that axon guidance genes are affected by somatic structural variants in up to 25% of human pancreatic cancers. Thus far, however, some of these mutations have only been correlated to survival probability and no function has been assigned to these observed axon guidance gene mutations in pancreatic cancer. In this study we established three novel pancreatic cancer cell lines and performed whole genome sequencing to discover novel mutations in axon guidance genes that may contribute to the cancer phenotype of these cells. We discovered, among other novel somatic variants in axon guidance pathway genes, a novel mutation in the PLXNA1 receptor (c.2587G>A) in newly established cell line SB.06 that mediates oncogenic cues of increased invasion and proliferation in SB.06 cells and increased invasion in 293T cells upon stimulation with the receptor's natural ligand semaphorin 3A compared to wild type PLXNA1 cells. Mutant PLXNA1 signaling was associated with increased Rho-GTPase and p42/p44 MAPK signaling activity and cytoskeletal expansion, but not changes in E-cadherin, vimentin, or metalloproteinase 9 expression levels. Pharmacologic inhibition of the Rho-GTPase family member CDC42 selectively abrogated PLXNA1 c.2587G>A-mediated increased invasion. These findings provide in-vitro confirmation that somatic mutations in axon guidance genes can provide oncogenic gain-of-function signals and may contribute to pancreatic cancer progression.

SDHB-Deficient Cancers: The Role of Mutations That Impair Iron Sulfur Cluster Delivery

BACKGROUND

Mutations in the Fe-S cluster-containing SDHB subunit of succinate dehydrogenase cause familial cancer syndromes. Recently the tripeptide motif L(I)YR was identified in the Fe-S recipient protein SDHB, to which the cochaperone HSC20 binds.

METHODS

In order to characterize the metabolic basis of SDH-deficient cancers we performed stable isotope-resolved metabolomics in a novel SDHB-deficient renal cell carcinoma cell line and conducted bioinformatics and biochemical screening to analyze Fe-S cluster acquisition and assembly of SDH in the presence of other cancer-causing SDHB mutations.

RESULTS

We found that the SDHBR46Q mutation in UOK269 cells disrupted binding of HSC20, causing rapid degradation of SDHB. In the absence of SDHB, respiration was undetectable in UOK269 cells, succinate was elevated to 351.4 ± 63.2 nmol/mg cellular protein, and glutamine became the main source of TCA cycle metabolites through reductive carboxylation.Furthermore, HIF1α, but not HIF2α, increased markedly and the cells showed a strong DNA CpG island methylatorphenotype (CIMP). Biochemical and bioinformatic screening revealed that 37% of disease-causing missense mutations in SDHB were located in either the L(I)YR Fe-S transfer motifs or in the 11 Fe-S cluster-ligating cysteines.

CONCLUSIONS

These findings provide a conceptual framework for understanding how particular mutations disproportionately cause the loss of SDH activity, resulting in accumulation of succinate and metabolic remodeling in SDHB cancer syndromes.

Patterns of somatic uniparental disomy identify novel tumor suppressor genes in colorectal cancer

Colorectal cancer (CRC) is characterized by specific patterns of copy number alterations (CNAs), which helped with the identification of driver oncogenes and tumor suppressor genes (TSGs). More recently, the usage of single nucleotide polymorphism arrays provided information of copy number neutral loss of heterozygosity, thus suggesting the occurrence of somatic uniparental disomy (UPD) and uniparental polysomy (UPP) events. The aim of this study is to establish an integrative profiling of recurrent UPDs/UPPs and CNAs in sporadic CRC. Our results indicate that regions showing high frequencies of UPD/UPP mostly coincide with regions typically involved in genomic losses. Among them, chromosome arms 3p, 5q, 9q, 10q, 14q, 17p, 17q, 20p, 21q and 22q preferentially showed UPDs/UPPs over genomic losses suggesting that tumor cells must maintain the disomic state of certain genes to favor cellular fitness. A meta-analysis using over 300 samples from The Cancer Genome Atlas confirmed our findings. Several regions affected by recurrent UPDs/UPPs contain well-known TSGs, as well as novel candidates such as ARID1A, DLC1, TCF7L2 and DMBT1. In addition, VCAN, FLT4, SFRP1 and GAS7 were also frequently involved in regions of UPD/UPP and displayed high levels of methylation. Finally, sequencing and fluorescence in situ hybridization analysis of the gene APC underlined that a somatic UPD event might represent the second hit to achieve biallelic inactivation of this TSG in colorectal tumors. In summary, our data define a profile of somatic UPDs/UPPs in sporadic CRC and highlights the importance of these events as a mechanism to achieve the inactivation of TSGs.

Recurrent epimutation of SDHC in gastrointestinal stromal tumors

Succinate dehydrogenase (SDH) is a conserved effector of cellular metabolism and energy production, and loss of SDH function is a driver mechanism in several cancers. SDH-deficient gastrointestinal stromal tumors (dSDH GISTs) collectively manifest similar phenotypes, including hypermethylated epigenomic signatures, tendency to occur in pediatric patients, and lack of KIT/PDGFRA mutations. dSDH GISTs often harbor deleterious mutations in SDH subunit genes (SDHA, SDHB, SDHC, and SDHD, termed SDHx), but some are SDHx wild type (WT). To further elucidate mechanisms of SDH deactivation in SDHx-WT GIST, we performed targeted exome sequencing on 59 dSDH GISTs to identify 43 SDHx-mutant and 16 SDHx-WT cases. Genome-wide DNA methylation and expression profiling exposed SDHC promoter-specific CpG island hypermethylation and gene silencing in SDHx-WT dSDH GISTs [15 of 16 cases (94%)]. Six of 15 SDHC-epimutant GISTs occurred in the setting of the multitumor syndrome Carney triad. We observed neither SDHB promoter hypermethylation nor large deletions on chromosome 1q in any SDHx-WT cases. Deep genome sequencing of a 130-kbp (kilo-base pair) window around SDHC revealed no recognizable sequence anomalies in SDHC-epimutant tumors. More than 2000 benign and tumor reference tissues, including stem cells and malignancies with a hypermethylator epigenotype, exhibit solely a non-epimutant SDHC promoter. Mosaic constitutional SDHC promoter hypermethylation in blood and saliva from patients with SDHC-epimutant GIST implicates a postzygotic mechanism in the establishment and maintenance of SDHC epimutation. The discovery of SDHC epimutation provides a unifying explanation for the pathogenesis of dSDH GIST, whereby loss of SDH function stems from either SDHx mutation or SDHC epimutation.

Abstract LB-171: Collaborating mutations in gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor of the gastrointestinal tract, is driven most commonly by activating mutations in the receptor tyrosine kinases KIT or PDGFRA. Alternatively, inactivating mutations of genes for the succinate dehydrogenase complex (SDH) constitute a distinct oncogenic mechanism in GIST. Using integrated genomic analyses we have recently reported that SDH deficiency in GIST may also arise from epigenomic inactivation of SDHC, reflected by coupled DNA methylation and expression silencing (1). SDHC epimutation is particularly frequent in, though not restricted to, patients with the cancer predisposition syndrome Carney Triad. It is well established that these primary driver mechanisms correlate with unique clinical, molecular, and epidemiological profiles. In order to identify collaborating oncogenic pathways associated with specific GIST subtypes we have extended our integrated genomic profiling of over 70 tumors enriched for SDH deficient cases. The primary focus is sequencing a panel of 200 cancer related genes for both somatic and inherited variants. We also include RNA expression arrays, DNA methylation arrays, and SNP arrays in this analysis. We have identified mutations in several known cancer associated genes including PTEN, KRAS, ARID1A, and TP53. In conclusion, collaborating mutations and deregulated pathways are identifiable in GIST and can increase our understanding of the underlying cancer biology as well as suggesting treatment possibilities for this malignancy. We acknowledge the contributions of the NIH Wild-Type GIST clinic investigators to this project.

References

1. Killian JK, Miettinen M, Walker RL, Wang Y, Zhu YJ, Waterfall JJ, et al. Recurrent epimutation of SDHC in gastrointestinal stromal tumors. Sci Transl Med. 2014;6:268ra177.

Citation Format: Joshua Waterfall, J. Keith Killian, Yuelin Jack Zhu, C. Christopher Lau, Markku Miettinen, Lee J. Helman, Paul S. Meltzer. Collaborating mutations in gastrointestinal stromal tumor. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-171. doi:10.1158/1538-7445.AM2015-LB-171

Characterization of genomic alterations in radiation-associated breast cancer among childhood cancer survivors, using comparative genomic hybridization (CGH) arrays

Ionizing radiation is an established risk factor for breast cancer. Epidemiologic studies of radiation-exposed cohorts have been primarily descriptive; molecular events responsible for the development of radiation-associated breast cancer have not been elucidated. In this study, we used array comparative genomic hybridization (array-CGH) to characterize genome-wide copy number changes in breast tumors collected in the Childhood Cancer Survivor Study (CCSS). Array-CGH data were obtained from 32 cases who developed a second primary breast cancer following chest irradiation at early ages for the treatment of their first cancers, mostly Hodgkin lymphoma. The majority of these cases developed breast cancer before age 45 (91%, n = 29), had invasive ductal tumors (81%, n = 26), estrogen receptor (ER)-positive staining (68%, n = 19 out of 28), and high proliferation as indicated by high Ki-67 staining (77%, n = 17 out of 22). Genomic regions with low-copy number gains and losses and high-level amplifications were similar to what has been reported in sporadic breast tumors, however, the frequency of amplifications of the 17q12 region containing human epidermal growth factor receptor 2 (HER2) was much higher among CCSS cases (38%, n = 12). Our findings suggest that second primary breast cancers in CCSS were enriched for an “amplifier” genomic subgroup with highly proliferative breast tumors. Future investigation in a larger irradiated cohort will be needed to confirm our findings.

Mutations of epigenetic regulatory genes are common in thymic carcinomas

Genetic alterations and etiology of thymic epithelial tumors (TETs) are largely unknown, hampering the development of effective targeted therapies for patients with TETs. Here TETs of advanced-stage patients enrolled in a clinical trial of molecularly-guided targeted therapies were employed for targeted sequencing of 197 cancer-associated genes. Comparative sequence analysis of 78 TET/blood paired samples obtained from 47 thymic carcinoma (TC) and 31 thymoma patients revealed a total of 86 somatic non-synonymous sequence variations across 39 different genes in 33 (42%) TETs. TCs (62%; 29/47) showed higher incidence of somatic non-synonymous mutations than thymomas (13%; 4/31; p < 0.0001). TP53 was the most frequently mutated gene in TETs (n = 13; 17%), especially in TCs (26%), and was associated with a poorer overall survival (p < 0.0001). Genes in histone modification [BAP1 (n = 6; 13%), SETD2 (n = 5; 11%), ASXL1 (n = 2; 4%)], chromatin remodeling [SMARCA4 (n = 2; 4%)], and DNA methylation [DNMT3A (n = 3; 7%), TET2 (n = 2; 4%), WT1 (n = 2; 4%)] pathways were recurrently mutated in TCs, but not in thymomas. Our results suggest a potential disruption of epigenetic homeostasis in TCs, and a substantial difference in genetic makeup between TCs and thymomas. Further investigation is warranted into the roles of epigenetic dysregulation in TC development and its potential for targeted therapy.

Abstract 1366: Discovery of biomarkers for antitumor drug resistance using 450K methylation data of NCI60

The National Cancer Institute Antitumor Cell line panel NCI60 is a very frequently used collection of cancer cell lines that has been largely characterized in different biological aspects. Data from proteomic and RNA expression analyses of this panel is already available to the scientific community. Also, the IC50 data for more than 100,000 different compound treatments is accessible in the developmental therapeutic program of NCI (dtp). However, very little has been explored about the epigenetic component of this panel. We have performed a thorough correlational study combining the available molecular information of NCI60, the data of our 450K NCI60 dataset and the IC50 data from the dtp to discover candidate genes for new biomarkers of resistance to antitumor agents. Finding new biomarkers to determine the most probable response to the therapy seems to be a key stage in the development of personalized medicine. Due to its stability and how easy it is to detect its level of methylation, DNA methylation changes appear to be a perfect candidate mark for the construction of this new generation of biomarkers. In this study we obtained multiples candidate genes whose methylation correlated to resistance to different drugs. In order to perform validation analyses we chose a gene that showed a strong positive correlation with the resistance to several DNA damage agents (DDA).Using overexpression and silencing assays we were able to demonstrate that the expression of this gene has a profound influence on the cell sensitivity to the DDA. Furthermore, through gene expression validation assays, such as 5-azacytidine treatments, we demonstrated that the promotor methylation of this gene is associated to its non-expression. In addition, we observed that this gene methylation correlates with a lower overall survival in an ovarian cancer cohort treated with platinum agents. Little is known about our candidate gene but it seems to be related to the DNA repair machine and also to have a function in the cell cycle control. These features could give an explanation to the importance of its presence in the response to DDA treatment. Our studies show that the analysis of DNA methylation changes in cancer cells in combination with other molecular alterations can be used in correlational studies to find trustworthy biomarkers for antitumor drug resistance.

Citation Format: Vanesa Nogales, Catia Moutinho, Anna Martinez-Cardús, Sudhir Varma, J. Keith Killian, William C. Reinhold, Paul S. Meltzer, Yves Pommier, Manel Esteller. Discovery of biomarkers for antitumor drug resistance using 450K methylation data of NCI60. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1366. doi:10.1158/1538-7445.AM2014-1366

The role of mutation of metabolism-related genes in genomic hypermethylation

Genetic mutations, metabolic dysfunction, and epigenetic misregulation are commonly considered to play distinct roles in tumor development and maintenance. However, intimate relationships between these mechanisms are now emerging. In particular, mutations in genes for the core metabolic enzymes IDH, SDH, and FH are significant drivers of diverse tumor types. In each case, the resultant accumulation of particular metabolites inhibits TET enzymes responsible for oxidizing 5-methylcytosine, leading to pervasive DNA hypermethylation.

Discovery and validation of methylation markers for endometrial cancer

The prognosis of endometrial cancer is strongly associated with stage at diagnosis, suggesting that early detection may reduce mortality. Women who are diagnosed with endometrial carcinoma often have a lengthy history of vaginal bleeding, which offers an opportunity for early diagnosis and curative treatment. We performed DNA methylation profiling on population-based endometrial cancers to identify early detection biomarkers and replicated top candidates in two independent studies. We compared DNA methylation values of 1,500 probes representing 807 genes in 148 population-based endometrial carcinoma samples and 23 benign endometrial tissues. Markers were replicated in another set of 69 carcinomas and 40 benign tissues profiled on the same platform. Further replication was conducted in The Cancer Genome Atlas and in prospectively collected endometrial brushings from women with and without endometrial carcinomas. We identified 114 CpG sites showing methylation differences with p values of ≤ 10(-7) between endometrial carcinoma and normal endometrium. Eight genes (ADCYAP1, ASCL2, HS3ST2, HTR1B, MME, NPY and SOX1) were selected for further replication. Age-adjusted odds ratios for endometrial cancer ranged from 3.44 (95%-CI: 1.33-8.91) for ASCL2 to 18.61 (95%-CI: 5.50-62.97) for HTR1B. An area under the curve (AUC) of 0.93 was achieved for discriminating carcinoma from benign endometrium. Replication in The Cancer Genome Atlas and in endometrial brushings from an independent study confirmed the candidate markers. This study demonstrates that methylation markers may be used to evaluate women with abnormal vaginal bleeding to distinguish women with endometrial carcinoma from the majority of women without malignancy.

MYC-driven accumulation of 2-hydroxyglutarate is associated with breast cancer prognosis

Metabolic profiling of cancer cells has recently been established as a promising tool for the development of therapies and identification of cancer biomarkers. Here we characterized the metabolomic profile of human breast tumors and uncovered intrinsic metabolite signatures in these tumors using an untargeted discovery approach and validation of key metabolites. The oncometabolite 2-hydroxyglutarate (2HG) accumulated at high levels in a subset of tumors and human breast cancer cell lines. We discovered an association between increased 2HG levels and MYC pathway activation in breast cancer, and further corroborated this relationship using MYC overexpression and knockdown in human mammary epithelial and breast cancer cells. Further analyses revealed globally increased DNA methylation in 2HG-high tumors and identified a tumor subtype with high tissue 2HG and a distinct DNA methylation pattern that was associated with poor prognosis and occurred with higher frequency in African-American patients. Tumors of this subtype had a stem cell-like transcriptional signature and tended to overexpress glutaminase, suggestive of a functional relationship between glutamine and 2HG metabolism in breast cancer. Accordingly, 13C-labeled glutamine was incorporated into 2HG in cells with aberrant 2HG accumulation, whereas pharmacologic and siRNA-mediated glutaminase inhibition reduced 2HG levels. Our findings implicate 2HG as a candidate breast cancer oncometabolite associated with MYC activation and poor prognosis.

Post-transcriptional dysregulation by miRNAs is implicated in the pathogenesis of gastrointestinal stromal tumor [GIST]

In contrast to adult mutant gastrointestinal stromal tumors [GISTs], pediatric/wild-type GISTs remain poorly understood overall, given their lack of oncogenic activating tyrosine kinase mutations. These GISTs, with a predilection for gastric origin in female patients, show limited response to therapy with tyrosine kinase inhibitors and generally pursue a more indolent course, but still may prove fatal. Defective cellular respiration appears to underpin tumor development in these wild-type cases, which as a group lack expression of succinate dehydrogenase [SDH] B, a surrogate marker for respiratory chain metabolism. Yet, only a small subset of the wild-type tumors show mutations in the genes coding for the SDH subunits [SDHx]. To explore additional pathogenetic mechanisms in these wild-type GISTs, we elected to investigate post-transcriptional regulation of these tumors by conducting microRNA (miRNA) profiling of a mixed cohort of 73 cases including 18 gastric pediatric wild-type, 25 (20 gastric, 4 small bowel and 1 retroperitoneal) adult wild-type GISTs and 30 gastric adult mutant GISTs. By this approach we have identified distinct signatures for GIST subtypes which correlate tightly with clinico-pathological parameters. A cluster of miRNAs on 14q32 show strikingly different expression patterns amongst GISTs, a finding which appears to be explained at least in part by differential allelic methylation of this imprinted region. Small bowel and retroperitoneal wild-type GISTs segregate with adult mutant GISTs and express SDHB, while adult wild-type gastric GISTs are dispersed amongst adult mutant and pediatric wild-type cases, clustering in this situation on the basis of SDHB expression. Interestingly, global methylation analysis has recently similarly demonstrated that these wild-type, SDHB-immunonegative tumors show a distinct pattern compared with KIT and PDGFRA mutant tumors, which as a rule do express SDHB. All cases with Carney triad within our cohort cluster together tightly.

Abstract 2963: Succinate dehydrogenase mutation underlies global epigenomic divergence in gastrointestinal stromal tumor

Although driver mutations in signal transduction kinases such as KIT are found in the majority of gastrointestinal stromal tumors (GIST), a subset of GISTs lack these mutations and instead exhibit loss-of-function defects in the mitochondrial succinate dehydrogenase (SDH) complex, a component of the Krebs cycle. To examine the effects of this metabolic defect on the epigenome, we used Illumina GoldenGate and 450K Infinium microarray technology to profile DNA methylation in GIST samples and uncovered markedly divergent global DNA methylation between SDH-null GIST (N=24) versus KIT or related tyrosine kinase pathway mutated GIST (N=39). When compared to reference normal tissues including intestinal smooth muscle (N=10) and neuronal tissue (N=13), SDH-deficient GIST was found to have an order of magnitude greater global hypermethylation than the kinase-pathway mutant group (84.9K vs. 8.4K targets, respectively). In a histologically distinct SDH-deficient tumor system, methylation divergence was further found among SDH-mutant paraganglioma/pheochromocytoma (N=29) using an adrenal tissue (N=15) reference baseline. These data expose an essential role for succinate metabolism in the maintenance of DNA methylation programming and tumor suppression. Because defects in other Krebs cycle enzymes are also oncogenic, we further sought to determine whether this phenomenon was confined to SDH-deficient tumors. Analysis of SDH-mutant GIST and isocitrate dehydrogenase (IDH)-mutant gliomas revealed comparable quantities of global hypo- and hypermethylated targets. We propose that this phenomenon may result from a failure of maintenance demethylation, secondary to inactivation of the TET2 5-methylcytosine dioxgenase system by the inhibitory metabolites succinate (in SDH deficient tumors) or 2-hydroxyglutarate (in IDH mutant tumors). While the biological ramifications of this distortion of the epigenome remain to be elucidated, this study clearly implicates the Krebs cycle as mitochondrial custodian of the methylome in diverse cancers.

Citation Format: Paul S. Meltzer, J. Keith Killian, Su Young Kim, Markku Miettinen, Carly Smith, Maria Tsokos, Martha Quezado, William I. Smith, Mona S. Jahromi, Robert L. Walker, Jerzy Lasota, Brandy Klotzle, Zengfeng Wang, Laura Jones, Yuelin Zhu, Yonghong Wang, Joshua J. Waterfall, Marina Bibikova, Maureen J. O'Sullivan, Constantine A. Stratakis, Joshua D. Schiffman, Jian-Bing Fan, Lee Helman. Succinate dehydrogenase mutation underlies global epigenomic divergence in gastrointestinal stromal tumor. [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 2963. doi:10.1158/1538-7445.AM2013-2963

Succinate dehydrogenase mutation underlies global epigenomic divergence in gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GIST) harbor driver mutations of signal transduction kinases such as KIT, or, alternatively, manifest loss-of-function defects in the mitochondrial succinate dehydrogenase (SDH) complex, a component of the Krebs cycle and electron transport chain. We have uncovered a striking divergence between the DNA methylation profiles of SDH-deficient GIST (n = 24) versus KIT tyrosine kinase pathway-mutated GIST (n = 39). Infinium 450K methylation array analysis of formalin-fixed paraffin-embedded tissues disclosed an order of magnitude greater genomic hypermethylation relative to SDH-deficient GIST versus the KIT-mutant group (84.9 K vs. 8.4 K targets). Epigenomic divergence was further found among SDH-mutant paraganglioma/pheochromocytoma (n = 29), a developmentally distinct SDH-deficient tumor system. Comparison of SDH-mutant GIST with isocitrate dehydrogenase-mutant glioma, another Krebs cycle-defective tumor type, revealed comparable measures of global hypo- and hypermethylation. These data expose a vital connection between succinate metabolism and genomic DNA methylation during tumorigenesis, and generally implicate the mitochondrial Krebs cycle in nuclear epigenomic maintenance.

CD8(+) lymphocytes suppress human immunodeficiency virus 1 replication by secreting type I interferons

CD8(+) cells can suppress human immunodeficiency virus 1 (HIV-1) replication by releasing soluble factors. In 26 years of intensive research efforts, the identity of the major CD8(+) cell antiviral factor has remained elusive. To investigate the mechanism for this antiviral immune response, we performed gene expression analyses on primary CD4(+) cells that were exposed to HIV-suppressing CD8(+) cells or CD8(+) cell-conditioned medium having HIV-suppressing activity. These experiments revealed increased levels of multiple genes stimulated by type I interferons (IFN; eg, IFN-α and IFN-β). Further evaluation revealed that primary CD8(+) cells, particularly those from elite controllers and other asymptomatic HIV-1-infected individuals, secrete IFN, and this response directly contributes to the in vitro suppression of HIV replication in CD4(+) cells. This novel immune response, likely mediated by memory CD8(+) T cells, may play an important role in a wide variety of viral infections, cancers, and autoimmune diseases.

Detection and therapeutic implications of c-Met mutations in small cell lung cancer and neuroendocrine tumors

BACKGROUND

We evaluated the mutation status of c-Met in small cell lung cancer (SCLC) and neuroendocrine tumors (NET), for which relatively limited therapeutic targets have been explored.

MATERIALS AND METHODS

c-Met was re-sequenced using cell lines and clinical samples. For in vitro studies, DNA constructs containing a juxtamembrane domain (JMD) and tyrosine kinase domain (TKD) were generated. Detected mutations were introduced into the construct and effects on c-Met phosphorylation and interaction with tyrosine kinase inhibitor drugs BMS777607 and SU11274 were assessed.

RESULTS

97 specimens were analyzed: 13 SCLC and 2 pulmonary carcinoid cell lines, 46 SCLC and 36 NET clinical specimens. Mutations were only detected in the JMD. No mutations were detected in the TKD. Found mutations consisted of the previously reported R988C and T1010I mutations. One novel JMD mutation, P996S, was detected in a SCLC specimen. The mutation rate in SCLC cell lines was 25% (31% including a derivative cell line), and 6.5% in clinical specimens. The mutation rate in NET was 8.3%. In vitro, there were no differences between wild type, R988C or T1010I mutants regarding c-Met phosphorylation at Y1003, located in the JMD, and at Y1234/1235, located in the TKD. BMS777607 and SU11274 were shown to inhibit phosphorylation of c-Met in wild type and R988C and T1010I mutants in a similar fashion.

CONCLUSIONS

In SCLC and neuroendocrine tumors MET mutations are relatively rare. Detected mutations were located in the juxtamembrane domain and were of no functional relevance as they did not influence c-Met phosphorylation, regardless of TKI treatment.

DNA methylation profiling identifies global methylation differences and markers of adrenocortical tumors

CONTEXT

It is not known whether there are any DNA methylation alterations in adrenocortical tumors.

OBJECTIVE

The objective of the study was to determine the methylation profile of normal adrenal cortex and benign and malignant adrenocortical tumors.

METHODS

Genome-wide methylation status of CpG regions were determined in normal (n = 19), benign (n = 48), primary malignant (n = 8), and metastatic malignant (n = 12) adrenocortical tissue samples. An integrated analysis of genome-wide methylation and mRNA expression in benign vs. malignant adrenocortical tissue samples was also performed.

RESULTS

Methylation profiling revealed the following: 1) that methylation patterns were distinctly different and could distinguish normal, benign, primary malignant, and metastatic tissue samples; 2) that malignant samples have global hypomethylation; and 3) that the methylation of CpG regions are different in benign adrenocortical tumors by functional status. Normal compared with benign samples had the least amount of methylation differences, whereas normal compared with primary and metastatic adrenocortical carcinoma samples had the greatest variability in methylation (adjusted P ≤ 0.01). Of 215 down-regulated genes (≥2-fold, adjusted P ≤ 0.05) in malignant primary adrenocortical tumor samples, 52 of these genes were also hypermethylated.

CONCLUSIONS

Malignant adrenocortical tumors are globally hypomethylated as compared with normal and benign tumors. Methylation profile differences may accurately distinguish between primary benign and malignant adrenocortical tumors. Several differentially methylated sites are associated with genes known to be dysregulated in malignant adrenocortical tumors.

Genome-wide methylation profiling in archival formalin-fixed paraffin-embedded tissue samples

New technologies allow for genome-scale measurement of DNA methylation. In an effort to increase the clinical utility of DNA methylation as a biomarker, we have adapted a commercial bisulfite epigenotyping assay for genome-wide methylation profiling in archival formalin-fixed paraffin-embedded pathology specimens. This chapter takes the reader step by step through a biomarker discovery experiment to identify phenotype-correlated DNA methylation signatures in routine pathology specimens.

Genome-wide methylation profiling in archival formalin-fixed paraffin-embedded tissue samples

New technologies allow for genome-scale measurement of DNA methylation. In an effort to increase the clinical utility of DNA methylation as a biomarker, we have adapted a commercial bisulfite epigenotyping assay for genome-wide methylation profiling in archival formalin-fixed paraffin-embedded pathology specimens. This chapter takes the reader step by step through a biomarker discovery experiment to identify phenotype-correlated DNA methylation signatures in routine pathology specimens.

Inhibition of Polo-like kinase 1 prevents the growth of metastatic breast cancer cells in the brain

Few therapeutic strategies exist for the treatment of metastatic tumor cells in the brain because the blood-brain barrier (BBB) limits drug access. Thus the identification of molecular targets and accompanying BBB permeable drugs will significantly benefit brain metastasis patients. Polo-like kinase 1 (Plk1) is an attractive molecular target because it is only expressed in dividing cells and its expression is upregulated in many tumors. Analysis of a publicly available database of human breast cancer metastases revealed Plk1 mRNA expression was significantly increased in brain metastases compared to systemic metastases (P = 0.0018). The selective Plk1 inhibitor, GSK461364A, showed substantial uptake in normal rodent brain. Using a breast cancer brain metastatic xenograft model (231-BR), we tested the efficacy of GSK461364A to prevent brain metastatic colonization. When treatment was started 3 days post-injection, GSK461364A at 50 mg/kg inhibited the development of large brain metastases 62% (P = 0.0001) and prolonged survival by 17%. GSK461364A sensitized tumor cells to radiation induced cell death in vitro. Previously, it was reported that mutations in p53 might render tumor cells more sensitive to Plk1 inhibition; however, p53 mutations are uncommon in breast cancer. In a cohort of 41 primary breast tumors and matched brain metastases, p53 immunostaining was increased in 61% of metastases; 44% of which were associated with primary tumors with low p53. The data suggest that p53 overexpression occurs frequently in brain metastases and may facilitate sensitivity to Plk1 inhibition. These data indicate Plk1 may be a new druggable target for the prevention of breast cancer brain metastases.

Methylation profiling of mediastinal gray zone lymphoma reveals a distinctive signature with elements shared by classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma

BACKGROUND

Mediastinal gray zone lymphoma is a newly recognized entity with transitional morphological and immunophenotypic features between the nodular sclerosis subtype of Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma. Diagnostic criteria for mediastinal gray zone lymphoma are still challenging, and the optimal therapy is as yet undetermined. Epigenetic changes have been implicated in the loss of the B-cell program in classical Hodgkin's lymphoma, and might provide a basis for the immunophenotypic alterations seen in mediastinal gray zone lymphoma.

DESIGN AND METHODS

We performed a large-scale DNA methylation analysis of microdissected tumor cells to investigate the biological underpinnings of mediastinal gray zone lymphoma and its association with the related entities classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma, making comparisons with the presumptively less related diffuse large B-cell lymphoma.

RESULTS

Principal component analysis demonstrated that mediastinal gray zone lymphoma has a distinct epigenetic profile intermediate between classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma but remarkably different from that of diffuse large B-cell lymphoma. Analysis of common hypo- and hypermethylated CpG targets in mediastinal gray zone lymphoma, classical Hodgkin's lymphoma, primary mediastinal large B-cell lymphoma and diffuse large B-cell lymphoma was performed and confirmed the findings of the principal component analysis. Based on the epigenetic profiles we were able to establish class prediction models utilizing genes such as HOXA5, MMP9, EPHA7 and DAPK1 which could distinguish between mediastinal gray zone lymphoma, classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma with a final combined prediction of 100%.

CONCLUSIONS

Our data confirm a close relationship between mediastinal gray zone lymphoma and both classical Hodgkin's lymphoma and primary mediastinal large B-cell lymphoma. However, important differences were observed as well, allowing a clear distinction from both parent entities. Thus, mediastinal gray zone lymphoma cannot be assigned to either classical Hodgkin's lymphoma or primary mediastinal large B-cell lymphoma, validating the decision to create an intermediate category in the World Health Organization classification.

A methyl-deviator epigenotype of estrogen receptor-positive breast carcinoma is associated with malignant biology

We broadly profiled DNA methylation in breast cancers (n = 351) and benign parenchyma (n = 47) for correspondence with disease phenotype, using FFPE diagnostic surgical pathology specimens. Exploratory analysis revealed a distinctive primary invasive carcinoma subclass featuring extreme global methylation deviation. Subsequently, we tested the correlation between methylation remodeling pervasiveness and malignant biological features. A methyl deviation index (MDI) was calculated for each lesion relative to terminal ductal-lobular unit baseline, and group comparisons revealed that high-grade and short-survival estrogen receptor-positive (ER(+)) cancers manifest a significantly higher MDI than low-grade and long-survival ER(+) cancers. In contrast, ER(-) cancers display a significantly lower MDI, revealing a striking epigenomic distinction between cancer hormone receptor subtypes. Kaplan-Meier survival curves of MDI-based risk classes showed significant divergence between low- and high-risk groups. MDI showed superior prognostic performance to crude methylation levels, and MDI retained prognostic significance (P < 0.01) in Cox multivariate analysis, including clinical stage and pathological grade. Most MDI targets individually are significant markers of ER(+) cancer survival. Lymphoid and mesenchymal indexes were not substantially different between ER(+) and ER(-) groups and do not explain MDI dichotomy. However, the mesenchymal index was associated with ER(+) cancer survival, and a high lymphoid index was associated with medullary carcinoma. Finally, a comparison between metastases and primary tumors suggests methylation patterns are established early and maintained through disease progression for both ER(+) and ER(-) tumors.

Archival fine-needle aspiration cytopathology (FNAC) samples: untapped resource for clinical molecular profiling

Microarray technologies provide high-resolution maps of chromosome imbalances and epigenomic aberrations in the cancer cell genome. Such assays are often sensitive to sample DNA integrity, voiding the utility of many archival pathology specimens and necessitating the special handling of prospective clinical specimens. We have identified the remarkable preservation of higher-molecular weight DNA in archival fine-needle aspiration cytopathology specimens from patients greater than 10 years of age. We further demonstrate the outstanding technical performance of 57 fine-needle aspiration cytopathology samples for aberration detection on high-resolution comparative genomic hybridization array, DNA methylation, and single nucleotide polymorphism genotyping platforms. Forty-four of 46 malignant aspirates in this study manifested unequivocal genomic aberrations. Importantly, matched Papanicolaou and Diff-Quik fine-needle aspiration cytopathology samples showed critical differences in DNA preservation and DNA integrity. Overall, this study identifies a largely untapped reserve of human pathology specimens for molecular profiling studies, with ramifications for the prospective collection of clinical biospecimens.

Epigenomic alterations and gene expression profiles in respiratory epithelia exposed to cigarette smoke condensate

Limited information is available regarding epigenomic events mediating initiation and progression of tobacco-induced lung cancers. In this study, we established an in vitro system to examine epigenomic effects of cigarette smoke in respiratory epithelia. Normal human small airway epithelial cells and cdk-4/hTERT-immortalized human bronchial epithelial cells (HBEC) were cultured in normal media with or without cigarette smoke condensate (CSC) for up to 9 months under potentially relevant exposure conditions. Western blot analysis showed that CSC mediated dose- and time-dependent diminution of H4K16Ac and H4K20Me3, while increasing relative levels of H3K27Me3; these histone alterations coincided with decreased DNA methyltransferase 1 (DNMT1) and increased DNMT3b expression. Pyrosequencing and quantitative RT-PCR experiments revealed time-dependent hypomethylation of D4Z4, NBL2, and LINE-1 repetitive DNA sequences; up-regulation of H19, IGF2, MAGE-A1, and MAGE-A3; activation of Wnt signaling; and hypermethylation of tumor suppressor genes such as RASSF1A and RAR-beta, which are frequently silenced in human lung cancers. Array-based DNA methylation profiling identified additional novel DNA methylation targets in soft-agar clones derived from CSC-exposed HBEC; a CSC gene expression signature was also identified in these cells. Progressive genomic hypomethylation and locoregional DNA hypermethylation induced by CSC coincided with a dramatic increase in soft-agar clonogenicity. Collectively, these data indicate that cigarette smoke induces 'cancer-associated' epigenomic alterations in cultured respiratory epithelia. This in vitro model may prove useful for delineating early epigenetic mechanisms regulating gene expression during pulmonary carcinogenesis.

Immunoguided laser assisted microdissection techniques for DNA methylation analysis of archival tissue specimens

Altered DNA methylation is a fundamental characteristic of carcinogenesis. The analysis of DNA methylation in tumor cells may help to better understand tumor pathogenesis and more importantly may be used as diagnostic tool with therapeutic consequences. To detect targets relevant in tumorigenesis, it is essential to separate neoplastic cells from nonneoplastic cells. An excellent method for isolating specific cells is laser-assisted microdissection (LAM). Target cell identification for immunoguided LAM (ILAM) requires immunohistochemistry (IHC). Yet, it is unclear whether IHC for ILAM influences DNA methylation. The goals of this study were to establish an optimized protocol for antigen retrieval and IHC of formalin-fixed paraffin-embedded (FFPE) specimens suitable for ILAM and to evaluate its effect on the DNA methylome using a high throughput array. Using ten archival FFPE specimens, we showed specific staining suitable for ILAM. Extracted DNA from microdissected cells of immunohistochemically or H&E-stained tissue sections showed identical DNA quality and a strong correlation (r = 0.94 to 0.98) for CpG target methylation of 1505 analyzed sites in a series of five paired samples. No differential methylation between H&E and IHC was detected in 1501 of 1505 CpG targets (99.7%; P < 0.05). These results demonstrate the validity and utility of the herein described protocol, which allows the application of ILAM for large-scale genomic and epigenetic analyses of archival tissue specimens.

Large-scale profiling of archival lymph nodes reveals pervasive remodeling of the follicular lymphoma methylome

Emerging technologies allow broad profiling of the cancer genome for differential DNA methylation relative to benign cells. Herein, bisulfite-modified DNA from lymph nodes with either reactive hyperplasia or follicular lymphoma (FL) were analyzed using a commercial C/UpG genotyping assay. Two hundred fifty-nine differentially methylated targets (DMT) distributed among 183 unique genes were identified in FL. Comparison of matched formalin-fixed, paraffin-embedded and frozen surgical pathology replicates showed the complete preservation of the cancer methylome among differently archived tissue specimens. Analysis of the DMT profile is consistent with a pervasive epigenomic remodeling process in FL that affects predominantly nonlymphoid genes.