Analytic validation of an FGFR -focused cell-free DNA liquid biopsy assay (FGFR-Dx).

Commercial liquid biopsy assays are routinely used by oncologists to monitor disease response and resistance to therapy. Additionally, in cases where tumor tissue is not available, clinicians may rely on cell-free DNA (cfDNA) testing as a surrogate for comprehensive tumor testing. While some gene rearrangements are well detected, current commercial liquid biopsy assays exhibit low sensitivity for fibroblast growth factor receptor ( FGFR ) rearrangements. FGFRs are altered in ∼2.5% of all cancers, including FGFR2 rearrangements in 10% of intrahepatic cholangiocarcinoma and FGFR3 point mutations and rearrangements in 10-15% of urothelial carcinoma. Therefore, we developed and analytically validated FGFR-Dx, an FGFR -focused cfDNA assay with improved sensitivity for FGFR rearrangements. FGFR-Dx comprehensively targets the introns in FGFR1-3 previously shown to be involved in gene fusions as well as all coding exons. Custom FGFR synthetic reference standards representing both single nucleotide variants (SNVs) and gene rearrangements were utilized at a range of variant frequencies and revealed a detection limit of 0.5% with sensitivities of 97.2% and 92.9% for SNVs and rearrangements, respectively. Furthermore, FGFR-Dx detected rearrangements and identified the intronic breakpoints from cfDNA collected from 13 of 15 patients with known FGFR fusions.

FGFR2-fusions define a clinically actionable molecular subset of pancreatic cancer.

Genomic alterations in fibroblast growth factor receptor (FGFR) genes are present in a small number of metastatic pancreatic ductal adenocarcinomas (PDAC) and may represent an emerging subgroup of patients likely to benefit from FGFR targeted therapies. Here we present four FGFR2 fusion-positive metastatic PDAC patients who exhibited durable responses or disease control to FGFR kinase inhibitors. Utilizing our custom FGFR focused cell-free DNA assay, FGFR-Dx, we serially monitored variant allele fractions of FGFR2 fusions during FGFR inhibitor treatment and observed dynamic changes correlating with clinical responses. Genomic analysis of 30,229 comprehensively profiled pancreatic cancers revealed FGFR1-3 fusions in 245 cases, an incidence of 0.81%. FGFR fusions were generally mutually exclusive from other known oncogenes. Our findings provide clinical evidence for identifying and treating FGFR2 fusion-positive PDAC patients with FGFR targeted therapy.

Myeloid neoplasm with histiocytosis and spleen tyrosine kinase fusion responds to fostamatinib.

Not available.

Pan-cancer Landscape of Programmed Death Ligand-1 and Programmed Death Ligand-2 Structural Variations.

PURPOSE: Programmed cell death protein-1 (PD-1) receptor and ligand interactions are the target of immunotherapies for more than 20 cancer types. Biomarkers that predict response to immunotherapy are microsatellite instability, tumor mutational burden, and programmed death ligand-1 (PD-L1) immunohistochemistry. Structural variations (SVs) in PD-L1 (CD274) and PD-L2 (PDCD1LG2) have been observed in cancer, but the comprehensive landscape is unknown. Here, we describe the genomic landscape of PD-L1 and PD-L2 SVs, their potential impact on the tumor microenvironment, and evidence that patients with these alterations can benefit from immunotherapy. METHODS: We analyzed sequencing data from cancer cases with PD-L1 and PD-L2 SVs across 22 publications and four data sets, including Foundation Medicine Inc, The Cancer Genome Atlas, International Cancer Genome Consortium, and the Oncology Research Information Exchange Network. We leveraged RNA sequencing to evaluate immune signatures. We curated literature reporting clinical outcomes of patients harboring PD-L1 or PD-L2 SVs. RESULTS: Using data sets encompassing 300,000 tumors, we curated 486 cases with SVs in PD-L1 and PD-L2 and observed consistent breakpoint patterns, or hotspots. Leveraging The Cancer Genome Atlas, we observed significant upregulation in PD-L1 expression and signatures for interferon signaling, macrophages, T cells, and immune cell proliferation in samples harboring PD-L1 or PD-L2 SVs. Retrospective review of 12 studies that identified patients with SVs in PD-L1 or PD-L2 revealed > 50% (52/71) response rate to PD-1 immunotherapy with durable responses. CONCLUSION: Our findings show that the 3'-UTR is frequently affected, and that SVs are associated with increased expression of ligands and immune signatures. Retrospective evidence from curated studies suggests this genomic alteration could help identify candidates for PD-1/PD-L1 immunotherapy. We expect these findings will better define PD-L1 and PD-L2 SVs in cancer and lend support for prospective clinical trials to target these alterations.

Genomic and Transcriptomic Characterization of Relapsed SCLC Through Rapid Research Autopsy.

INTRODUCTION: Relapsed SCLC is characterized by therapeutic resistance and high mortality rate. Despite decades of research, mechanisms responsible for therapeutic resistance have remained elusive owing to limited tissues available for molecular studies. Thus, an unmet need remains for molecular characterization of relapsed SCLC to facilitate development of effective therapies. METHODS: We performed whole-exome and transcriptome sequencing of metastatic tumor samples procured from research autopsies of five patients with relapsed SCLC. We implemented bioinformatics tools to infer subclonal phylogeny and identify recurrent genomic alterations. We implemented immune cell signature and single-sample gene set enrichment analyses on tumor and normal transcriptome data from autopsy and additional primary and relapsed SCLC data sets. Furthermore, we evaluated T cell-inflamed gene expression profiles in neuroendocrine (ASCL1, NEUROD1) and non-neuroendocrine (YAP1, POU2F3) SCLC subtypes. RESULTS: Exome sequencing revealed clonal heterogeneity (intertumor and intratumor) arising from branched evolution and identified resistance-associated truncal and subclonal alterations in relapsed SCLC. Transcriptome analyses further revealed a noninflamed phenotype in neuroendocrine SCLC subtypes (ASCL1, NEUROD1) associated with decreased expression of genes involved in adaptive antitumor immunity whereas non-neuroendocrine subtypes (YAP1, POU2F3) revealed a more inflamed phenotype. CONCLUSIONS: Our results reveal substantial tumor heterogeneity and complex clonal evolution in relapsed SCLC. Furthermore, we report that neuroendocrine SCLC subtypes are immunologically cold, thus explaining decreased responsiveness to immune checkpoint blockade. These results suggest that the mechanisms of innate and acquired therapeutic resistances are subtype-specific in SCLC and highlight the need for continued investigation to bolster therapy selection and development for this cancer.

Characterization of Clonal Evolution in Microsatellite Unstable Metastatic Cancers through Multiregional Tumor Sequencing.

Microsatellites are short, repetitive segments of DNA, which are dysregulated in mismatch repair-deficient (MMRd) tumors resulting in microsatellite instability (MSI). MSI has been identified in many human cancer types with varying incidence, and microsatellite instability-high (MSI-H) tumors often exhibit increased sensitivity to immune-enhancing therapies such as PD-1/PD-L1 inhibition. Next-generation sequencing (NGS) has permitted advancements in MSI detection, and recent computational advances have enabled characterization of tumor heterogeneity via NGS. However, the evolution and heterogeneity of microsatellite changes in MSI-positive tumors remains poorly described. We determined MSI status in 6 patients using our previously published algorithm, MANTIS, and inferred subclonal composition and phylogeny with Canopy and SuperFreq. We developed a simulated annealing-based method to characterize microsatellite length distributions in specific subclones and assessed the evolution of MSI in the context of tumor heterogeneity. We identified three to eight tumor subclones per patient, and each subclone exhibited MMRd-associated base substitution signatures. We noted that microsatellites tend to shorten over time, and that MMRd fosters heterogeneity by introducing novel mutations throughout the disease course. Some microsatellites are altered among all subclones in a patient, whereas other loci are only altered in particular subclones corresponding to subclonal phylogenetic relationships. Overall, our results indicate that MMRd is a substantial driver of heterogeneity, leading to both MSI and subclonal divergence. IMPLICATIONS: We leveraged subclonal inference to assess clonal evolution based on somatic mutations and microsatellites, which provides insight into MMRd as a dynamic mutagenic process in MSI-H malignancies.

Efficacy of FGFR Inhibitors and Combination Therapies for Acquired Resistance in FGFR2-Fusion Cholangiocarcinoma.

The fibroblast growth factor receptor (FGFR) signaling pathway is aberrantly activated in approximately 15% to 20% of patients with intrahepatic cholangiocarcinoma. Currently, several FGFR kinase inhibitors are being assessed in clinical trials for patients with FGFR-altered cholangiocarcinoma. Despite evidence of initial responses and disease control, virtually all patients eventually develop acquired resistance. Thus, there is a critical need for the development of innovative therapeutic strategies to overcome acquired drug resistance. Here, we present findings from a patient with FGFR2-altered metastatic cholangiocarcinoma who enrolled in a phase II clinical trial of the FGFR inhibitor, infigratinib (BGJ398). Treatment was initially effective as demonstrated by imaging and tumor marker response; however, after 8 months on trial, the patient exhibited tumor regrowth and disease progression. Targeted sequencing of tumor DNA after disease progression revealed the FGFR2 kinase domain p.E565A and p.L617M single-nucleotide variants (SNV) hypothesized to drive acquired resistance to infigratinib. The sensitivities of these FGFR2 SNVs, which were detected post-infigratinib therapy, were extended to include clinically relevant FGFR inhibitors, including AZD4547, erdafitinib (JNJ-42756493), dovitinib, ponatinib, and TAS120, and were evaluated in vitro Through a proteomics approach, we identified upregulation of the PI3K/AKT/mTOR signaling pathway in cells harboring the FGFR2 p.E565A mutation and demonstrated that combination therapy strategies with FGFR and mTOR inhibitors may be used to overcome resistance to FGFR inhibition, specific to infigratinib. Collectively, these studies support the development of novel combination therapeutic strategies in addition to the next generation of FGFR inhibitors to overcome acquired resistance in patients.

Detection of Microsatellite Instability Biomarkers via Next-Generation Sequencing.

A high level of microsatellite instability (MSI-H+) is an emerging predictive and prognostic biomarker for immunotherapy response in cancer. Recently, MSI-H+ has been detected in a variety of cancer types, in addition to the classical cancers associated with Lynch Syndrome. Clinical testing for MSI-H+ is currently performed primarily through traditional polymerase chain reaction (PCR) or immunohistochemistry (IHC) assays. However, next-generation sequencing (NGS)-based approaches have been developed which have multiple advantages over traditional assays. For instance, NGS has the ability to interrogate thousands of microsatellite loci compared with just 5-7 loci that are detected by PCR. In this chapter, we detail the biochemical and computational steps to detect MSI-H+ from analysis of paired tumor and normal samples through NGS. We begin with DNA extraction, describe sequencing library preparation and quality control (QC), and outline the bioinformatics steps necessary for sequence alignment, preprocessing, and MSI-H+ detection using the software tool MANTIS. This workflow is intended to facilitate more widespread usage and adaptation of NGS-powered MSI detection, which can be eventually standardized for routine clinical testing.

Tumor heterogeneity and acquired drug resistance in FGFR2-fusion-positive cholangiocarcinoma through rapid research autopsy.

Cholangiocarcinoma is a highly aggressive and lethal malignancy, with limited treatment options available. Recently, FGFR inhibitors have been developed and utilized in FGFR-mutant cholangiocarcinoma; however, resistance often develops and the genomic determinants of resistance are not fully characterized. We completed whole-exome sequencing (WES) of 11 unique tumor samples obtained from a rapid research autopsy on a patient with FGFR-fusion-positive cholangiocarcinoma who initially responded to the pan-FGFR inhibitor, INCB054828. In vitro studies were carried out to characterize the novel FGFR alteration and secondary FGFR2 mutation identified. Multisite WES and analysis of tumor heterogeneity through subclonal inference identified four genetically distinct cancer cell populations, two of which were only observed after treatment. Additionally, WES revealed an FGFR2 N549H mutation hypothesized to confer resistance to the FGFR inhibitor INCB054828 in a single tumor sample. This hypothesis was corroborated with in vitro cell-based studies in which cells expressing FGFR2-CLIP1 fusion were sensitive to INCB054828 (IC50 value of 10.16 nM), whereas cells with the addition of the N549H mutation were resistant to INCB054828 (IC50 value of 1527.57 nM). Furthermore, the FGFR2 N549H secondary mutation displayed cross-resistance to other selective FGFR inhibitors, but remained sensitive to the nonselective inhibitor, ponatinib. Rapid research autopsy has the potential to provide unprecedented insights into the clonal evolution of cancer throughout the course of the disease. In this study, we demonstrate the emergence of a drug resistance mutation and characterize the evolution of tumor subclones within a cholangiocarcinoma disease course.

Characterization of a KLK2-FGFR2 fusion gene in two cases of metastatic prostate cancer.

BACKGROUND: The fibroblast growth factor receptor (FGFR) signaling pathway is activated in multiple tumor types through gene amplifications, single base substitutions, or gene fusions. Multiple small molecule kinase inhibitors targeting FGFR are currently being evaluated in clinical trials for patients with FGFR chromosomal translocations. Patients with novel gene fusions involving FGFR may represent candidates for kinase inhibitors. METHODS: A targeted RNA-sequencing assay identified a KLK2-FGFR2 fusion gene in two patients with metastatic prostate cancer. NIH3T3 cells were transduced to express the KLK2-FGFR2 fusion. Migration assays, Western blots, and drug sensitivity assays were performed to functionally characterize the fusion. RESULTS: Expression of the KLK2-FGFR2 fusion protein in NIH3T3 cells induced a profound morphological change promoting enhanced migration and activation of downstream proteins in FGFR signaling pathways. The KLK2-FGFR2 fusion protein was determined to be highly sensitive to the selective FGFR inhibitors AZD-4547, BGJ398, JNJ-42756943, the irreversible inhibitor TAS-120, and the non-selective inhibitor Ponatinib. The KLK2-FGFR2 fusion did not exhibit sensitivity to the non-selective inhibitor Dovitinib. CONCLUSIONS: Importantly, the KLK2-FGFR2 fusion represents a novel target for precision therapies and should be screened for in men with prostate cancer.

Genomic characterization of metastatic ultra-hypermutated interdigitating dendritic cell sarcoma through rapid research autopsy.

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare cancer of dendritic cell origin that lacks a standardized treatment approach. Here, we performed genomic characterization of metastatic IDCS through whole exome sequencing (WES) of tumor tissues procured from a patient who underwent research autopsy. WES was also performed on a treatment-naïve tumor biopsy sample obtained from prior surgical resection. Our analyses revealed ultra-hypermutation, defined as >100 mutations per megabase, in this patient's cancer, which was further characterized by the presence of three distinct mutational signatures including UV radiation and APOBEC signatures. To characterize clonal heterogeneity, we used the bioinformatics tool Canopy to leverage single nucleotide and copy number variants to catalog six subclones across various metastatic tumors. Truncal alterations, defined as being present in all clonal tumor cell populations, in this patient's cancer include point mutations in TP53 and CDKN2A and amplifications of c-KIT and APOBEC3A-H, which are likely driver mutations. In summary, we have performed genomic characterization evaluating tumor mutational burden (TMB) and heterogeneity in a patient with metastatic IDCS. Despite ultra-hypermutation, this patient's cancer was not responsive to treatment with PD-1 inhibition. Our results underscore the importance of characterizing clonal heterogeneity in TMB-high cancers.

Targeting BRAF Mutations in High-Grade Neuroendocrine Carcinoma of the Colon.

Mutations in the RAS/RAF/MEK/ERK pathway leading to constitutive activation and uncontrolled cellular growth have been identified in various human malignancies, making this pathway a target for potential therapeutics. The activating BRAFV600E mutation is one well-characterized oncogenic mutation that has been described and targeted with clinical success in various malignancies, including melanoma and hairy cell leukemia. Although BRAF-directed treatments have yielded clinical benefit in a subset of tumor types, such as melanoma, thyroid cancer, and lung cancer, BRAF inhibition fails to confer a clinical benefit in colon cancer. Identification of patients for whom BRAF inhibition may produce clinically meaningful outcomes is imperative. The incidence of BRAF mutations in neuroendocrine carcinoma (NEC) is estimated to be 5% to 10%. A recent case series demonstrated benefit in targeting the BRAFV600E mutation in metastatic high-grade rectal NECs. Combination BRAF and MEK inhibition is known to yield improved outcomes compared with BRAF inhibition alone in melanoma. This report presents 2 patients with high-grade colorectal NECs who had different responses to treatment with combined BRAF/MEK inhibition after experiencing disease progression through first-line platinum-based chemotherapy. One patient experienced an excellent initial response to therapy before ultimately experiencing progression, and in the other patient initially had stable disease before eventually experiencing progression. These cases highlight the complicated role BRAF mutations play in gastrointestinal NECs, and the need for further research to identify not only patients who may benefit from BRAF-directed therapies but also strategies to avoid development of resistance.

Metaplastic breast cancer in a patient with neurofibromatosis type 1 and somatic loss of heterozygosity.

Metaplastic breast carcinoma (MBC) is rare and has a poor prognosis. Here we describe genetic analysis of a 41-yr-old female patient with MBC and neurofibromatosis type I (NF1). She initially presented with pT3N1a, grade 3 MBC, but lung metastases were discovered subsequently. To identify the molecular cause of her NF1, we screened for germline mutations disrupting NF1 or SPRED1, revealing a heterozygous germline single-nucleotide variant (SNV) in exon 21 of NF1 at c.2709G>A, Chr 17: 29556342. By report, this variant disrupts pre-mRNA splicing of NF1 transcripts. No pathogenic mutations were identified in SPRED1 A potential association between MBC and NF1 was reported in eight previous cases, but none underwent detailed genomics analysis. To identify additional candidate germline variants potentially predisposing to MBC, we conducted targeted exome sequencing of 279 established cancer-causing genes in a control blood sample, disclosing four rare SNVs. Analysis of her breast tumor showed markedly altered variant allelic fractions (VAFs) for two (50%) of them, revealing somatic loss of heterozygosity (LOH) at germline SNVs. Of these, only the VAF of the pathogenic SNV in NF1 was increased in the tumor. Tumor sequencing demonstrated five somatic mutations altering TP53, BRCA1, and other genes potentially contributing to cancer formation. Because somatic LOH at certain germline SNVs can enhance their impacts, we conclude that increased allelic imbalance of the pathogenic SNV in NF1 likely contributed to tumorigenesis. Our results highlight a need to assess predisposing genetic factors and LOH that can cause rare, aggressive diseases such as MBC in NF1.

Validation of a Targeted RNA Sequencing Assay for Kinase Fusion Detection in Solid Tumors.

Kinase gene fusions are important drivers of oncogenic transformation and can be inhibited with targeted therapies. Clinical grade diagnostics using RNA sequencing to detect gene rearrangements in solid tumors are limited, and the few that are available require prior knowledge of fusion break points. To address this, we have analytically validated a targeted RNA sequencing assay (OSU-SpARKFuse) for fusion detection that interrogates complete transcripts from 93 kinase and transcription factor genes. From a total of 74 positive and 36 negative control samples, OSU-SpARKFuse had 93.3% sensitivity and 100% specificity for fusion detection. Assessment of repeatability and reproducibility revealed 96.3% and 94.4% concordance between intrarun and interrun technical replicates, respectively. Application of this assay on prospective patient samples uncovered OLFM4 as a novel RET fusion partner in a small-bowel cancer and led to the discovery of a KLK2-FGFR2 fusion in a patient with prostate cancer who subsequently underwent treatment with a pan-fibroblast growth factor receptor inhibitor. Beyond fusion detection, OSU-SpARKFuse has built-in capabilities for discovery research, including gene expression analysis, detection of single-nucleotide variants, and identification of alternative splicing events.

Akt Activation Mediates Acquired Resistance to Fibroblast Growth Factor Receptor Inhibitor BGJ398.

Activation of FGFR signaling through mutations, amplifications, or fusions involving FGFR1, 2, 3, or 4 is seen in multiple tumors, including lung, bladder, and cholangiocarcinoma. Currently, several clinical trials are evaluating the role of novel FGFR inhibitors in solid tumors. As we move forward with FGFR inhibitors clinically, we anticipate the emergence of resistance with treatment. Consequently, we sought to study the mechanism(s) of acquired resistance to FGFR inhibitors using annotated cancer cell lines. We identified cancer cell lines that have activating mutations in FGFR1, 2, or 3 and treated them chronically with the selective FGFR inhibitor, BGJ398. We observed resistance to chronic BGJ398 exposure in DMS114 (small-cell lung cancer, FGFR1 amplification) and RT112 (urothelial carcinoma, FGFR3 fusion/amplification) cell lines based on viability assays. Reverse-phase protein array (RPPA) analysis showed increased phosphorylation of Akt (T308 and S473) and its downstream target GSK3 (S9 and S21) in both the resistant cell lines when compared with matching controls. Results of RPPA were confirmed using immunoblots. Consequently, the addition of an Akt inhibitor (GSK2141795) or siRNA was able to restore sensitivity to BGJ398 in resistant cell lines. These data suggest a role for Akt pathway in mediating acquired resistance to FGFR inhibition. Mol Cancer Ther; 16(4); 614-24. ©2017 AACR.

Cancer Driver Log (CanDL): Catalog of Potentially Actionable Cancer Mutations.

Massively parallel sequencing technologies have enabled characterization of genomic alterations across multiple tumor types. Efforts have focused on identifying driver mutations because they represent potential targets for therapy. However, because of the presence of driver and passenger mutations, it is often challenging to assign the clinical relevance of specific mutations observed in patients. Currently, there are multiple databases and tools that provide in silico assessment for potential drivers; however, there is no comprehensive resource for mutations with functional characterization. Therefore, we created an expert-curated database of potentially actionable driver mutations for molecular pathologists to facilitate annotation of cancer genomic testing. We reviewed scientific literature to identify variants that have been functionally characterized in vitro or in vivo as driver mutations. We obtained the chromosome location and all possible nucleotide positions for each amino acid change and uploaded them to the Cancer Driver Log (CanDL) database with associated literature reference indicating functional driver evidence. In addition to a simple interface, the database allows users to download all or selected genes as a comma-separated values file for incorporation into their own analysis pipeline. Furthermore, the database includes a mechanism for third-party contributions to support updates for novel driver mutations. Overall, this freely available database will facilitate rapid annotation of cancer genomic testing in molecular pathology laboratories for mutations.

Evaluation of Hybridization Capture Versus Amplicon-Based Methods for Whole-Exome Sequencing.

Next-generation sequencing has aided characterization of genomic variation. While whole-genome sequencing may capture all possible mutations, whole-exome sequencing remains cost-effective and captures most phenotype-altering mutations. Initial strategies for exome enrichment utilized a hybridization-based capture approach. Recently, amplicon-based methods were designed to simplify preparation and utilize smaller DNA inputs. We evaluated two hybridization capture-based and two amplicon-based whole-exome sequencing approaches, utilizing both Illumina and Ion Torrent sequencers, comparing on-target alignment, uniformity, and variant calling. While the amplicon methods had higher on-target rates, the hybridization capture-based approaches demonstrated better uniformity. All methods identified many of the same single-nucleotide variants, but each amplicon-based method missed variants detected by the other three methods and reported additional variants discordant with all three other technologies. Many of these potential false positives or negatives appear to result from limited coverage, low variant frequency, vicinity to read starts/ends, or the need for platform-specific variant calling algorithms. All methods demonstrated effective copy-number variant calling when evaluated against a single-nucleotide polymorphism array. This study illustrates some differences between whole-exome sequencing approaches, highlights the need for selecting appropriate variant calling based on capture method, and will aid laboratories in selecting their preferred approach.

Comparison of custom capture for targeted next-generation DNA sequencing.

Targeted, capture-based DNA sequencing is a cost-effective method to focus sequencing on a coding region or other customized region of the genome. There are multiple targeted sequencing methods available, but none has been systematically investigated and compared. We evaluated four commercially available custom-targeted DNA technologies for next-generation sequencing with respect to on-target sequencing, uniformity, and ability to detect single-nucleotide variations (SNVs) and copy number variations. The technologies that used sonication for DNA fragmentation displayed impressive uniformity of capture, whereas the others had shorter preparation times, but sacrificed uniformity. One of those technologies, which uses transposase for DNA fragmentation, has a drawback requiring sample pooling, and the last one, which uses restriction enzymes, has a limitation depending on restriction enzyme digest sites. Although all technologies displayed some level of concordance for calling SNVs, the technologies that require restriction enzymes or transposase missed several SNVs largely because of the lack of coverage. All technologies performed well for copy number variation calling when compared to single-nucleotide polymorphism arrays. These results enable laboratories to compare these methods to make informed decisions for their intended applications.