Kristina M. Knapp

Integrated genomic DNA/RNA profiling of hematologic malignancies in the clinical setting

The spectrum of somatic alterations in hematologic malignancies includes substitutions, insertions/deletions (indels), copy number alterations (CNAs), and a wide range of gene fusions; no current clinically available single assay captures the different types of alterations. We developed a novel next-generation sequencing-based assay to identify all classes of genomic alterations using archived formalin-fixed paraffin-embedded blood and bone marrow samples with high accuracy in a clinically relevant time frame, which is performed in our Clinical Laboratory Improvement Amendments-certified College of American Pathologists-accredited laboratory. Targeted capture of DNA/RNA and next-generation sequencing reliably identifies substitutions, indels, CNAs, and gene fusions, with similar accuracy to lower-throughput assays that focus on specific genes and types of genomic alterations. Profiling of 3696 samples identified recurrent somatic alterations that impact diagnosis, prognosis, and therapy selection. This comprehensive genomic profiling approach has proved effective in detecting all types of genomic alterations, including fusion transcripts, which increases the ability to identify clinically relevant genomic alterations with therapeutic relevance.

Combination Targeted Therapy to Disrupt Aberrant Oncogenic Signaling and Reverse Epigenetic Dysfunction in IDH2- and TET2-Mutant Acute Myeloid Leukemia.

Genomic studies in acute myeloid leukemias (AML) have identified mutations that drive altered DNA methylation, including TET2 and IDH2 Here, we show that models of AML resulting from TET2 or IDH2 mutations combined with FLT3ITD mutations are sensitive to 5-azacytidine or to the IDH2 inhibitor AG-221, respectively. 5-azacytidine and AG-221 treatment induced an attenuation of aberrant DNA methylation and transcriptional output and resulted in a reduction in leukemic blasts consistent with antileukemic activity. These therapeutic benefits were associated with restoration of leukemic cell differentiation, and the normalization of hematopoiesis was derived from mutant cells. By contrast, combining AG-221 or 5-azacytidine with FLT3 inhibition resulted in a reduction in mutant allele burden, progressive recovery of normal hematopoiesis from non-mutant stem-progenitor cells, and reversal of dysregulated DNA methylation and transcriptional output. Together, our studies suggest combined targeting of signaling and epigenetic pathways can increase therapeutic response in AML.Significance: AMLs with mutations in TET2 or IDH2 are sensitive to epigenetic therapy through inhibition of DNA methyltransferase activity by 5-azacytidine or inhibition of mutant IDH2 through AG-221. These inhibitors induce a differentiation response and can be used to inform mechanism-based combination therapy. Cancer Discov; 7(5); 494-505. ©2017 AACR.See related commentary by Thomas and Majeti, p. 459See related article by Yen et al., p. 478This article is highlighted in the In This Issue feature, p. 443.

Patient-derived xenotransplants can recapitulate the genetic driver landscape of acute leukemias.

Genomic studies have identified recurrent somatic mutations in acute leukemias. However, current murine models do not sufficiently encompass the genomic complexity of human leukemias. To develop preclinical models, we transplanted 160 samples from patients with acute leukemia (acute myeloid leukemia, mixed lineage leukemia, B-cell acute lymphoblastic leukemia, T-cell ALL) into immunodeficient mice. Of these, 119 engrafted with expected immunophenotype. Targeted sequencing of 374 genes and 265 frequently rearranged RNAs detected recurrent and novel genetic lesions in 48 paired primary tumor (PT) and patient-derived xenotransplant (PDX) samples. Overall, the frequencies of 274 somatic variant alleles correlated between PT and PDX samples, although the data were highly variable for variant alleles present at 0–10%. Seventeen percent of variant alleles were detected in either PT or PDX samples only. Based on variant allele frequency changes, 24 PT-PDX pairs were classified as concordant while the other 24 pairs showed various degree of clonal discordance. There was no correlation of clonal concordance with clinical parameters of diseases. Significantly more bone marrow samples than peripheral blood samples engrafted discordantly. These data demonstrate the utility of developing PDX banks for modeling human leukemia, and emphasize the importance of genomic profiling of PDX and patient samples to ensure concordance before performing mechanistic or therapeutic studies.

Clonal B cells in Waldenström's macroglobulinemia exhibit functional features of chronic active B-cell receptor signaling

Waldenström’s macroglobulinemia (WM) is a B-cell non-Hodgkin’s lymphoma (B-NHL) characterized by immunoglobulin M (IgM) monoclonal gammopathy and the medullary expansion of clonal lymphoplasmacytic cells. Neoplastic transformation has been partially attributed to hyperactive MYD88 signaling, secondary to the MYD88 L265P mutation, occurring in the majority of WM patients. Nevertheless, the presence of chronic active B-cell receptor (BCR) signaling, a feature of multiple IgM+ B-NHL, remains a subject of speculation in WM. Here, we interrogated the BCR signaling capacity of primary WM cells by utilizing multiparametric phosphoflow cytometry and found heightened basal phosphorylation of BCR-related signaling proteins, and augmented phosphoresponses on surface IgM (sIgM) crosslinking, compared with normal B cells. In support of those findings we observed high sIgM expression and loss of phosphatase activity in WM cells, which could both lead to signaling potentiation in clonal cells. Finally, led by the high-signaling heterogeneity among WM samples, we generated patient-specific phosphosignatures, which subclassified patients into a ‘high’ and a ‘healthy-like’ signaling group, with the second corresponding to patients with a more indolent clinical phenotype. These findings support the presence of chronic active BCR signaling in WM while providing a link between differential BCR signaling utilization and distinct clinical WM subgroups.

Genomics of primary chemoresistance and remission induction failure in paediatric and adult acute myeloid leukaemia

Cure rates of children and adults with acute myeloid leukaemia (AML) remain unsatisfactory partly due to chemotherapy resistance. We investigated the genetic basis of AML in 107 primary cases by sequencing 670 genes mutated in haematological malignancies. SETBP1, ASXL1 and RELN mutations were significantly associated with primary chemoresistance. We identified genomic alterations not previously described in AML, together with distinct genes that were significantly overexpressed in therapy‐resistant AML. Defined gene mutations were sufficient to explain primary induction failure in only a minority of cases. Thus, additional genetic or molecular mechanisms must cause primary chemoresistance in paediatric and adult AML.

Mutational correlates of response to hypomethylating agent therapy in acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive malignancy with median age at diagnosis of 67 years, stressing the importance of developing treatments that are both effective and tolerable in elderly patients. Hypomethylating agents (HMAs) have been extensively studied in AML, typically in older adults who are deemed to be unfit for standard induction chemotherapy, demonstrating improved complete response (CR) rate and trends toward improvement in overall survival (OS) compared with conventional care regimens in the phase III setting with less favorable responses in the relapsed/refractory setting. Genome-wide studies of AML patients have revealed that 44% of patients with de novo AML harbor mutations in genes affecting DNAmethylation, including DNMT3A (26%), IDH1/2 (20%), TET2 (8%), and WT1 (6%). The presence of these mutations has been suggested to have therapeutic implications in small, retrospective series. Using data from two large referral centers together with previously reported data, we sought to investigate the relationship between somatic gene mutations affecting DNA methylation and HMA response in an expanded AML patient cohort. We did not observe a relationship between response to HMAs and IDH1/2 and TET2 mutations. We identified DNMT3A mutations to predict response to HMAs in patients treated in the frontline setting [odds ratio (OR), 3.12; P=0.001], but not in the total cohort when including relapsed/refractory patients (OR 1.72; P=0.23). This is a dual institution, retrospective study. Permission to review medical records was obtained by the Institutional Review Board of each participating institution. From March 2010 to December 2014, 242 patients were identified at Memorial Sloan Kettering Cancer Center (MSKCC) who had a diagnosis of AML by World Health Organization (WHO) criteria and next-gen-

Hsp90 inhibition disrupts JAK-STAT signaling and leads to reductions in splenomegaly in patients with MPNs.

The introduction of JAK inhibitors into clinical practice has improved outcomes for patients with myeloproliferative neoplasms (MPNs). Ruxolitinib, the only approved JAK inhibitor for MPN patients, has demonstrated an ability to decrease splenomegaly and relieve constitutional symptoms.[1][1]–[3][

Integrated DNA/RNA targeted genomic profiling of diffuse large B-cell lymphoma using a clinical assay

We sought to define the genomic landscape of diffuse large B-cell lymphoma (DLBCL) by using formalin-fixed paraffin-embedded (FFPE) biopsy specimens. We used targeted sequencing of genes altered in hematologic malignancies, including DNA coding sequence for 405 genes, noncoding sequence for 31 genes, and RNA coding sequence for 265 genes (FoundationOne-Heme). Short variants, rearrangements, and copy number alterations were determined. We studied 198 samples (114 de novo, 58 previously treated, and 26 large-cell transformation from follicular lymphoma). Median number of GAs per case was 6, with 97% of patients harboring at least one alteration. Recurrent GAs were detected in genes with established roles in DLBCL pathogenesis (e.g. MYD88, CREBBP, CD79B, EZH2), as well as notable differences compared to prior studies such as inactivating mutations in TET2 (5%). Less common GAs identified potential targets for approved or investigational therapies, including BRAF, CD274 (PD-L1), IDH2, and JAK1/2. TP53 mutations were more frequently observed in relapsed/refractory DLBCL, and predicted for lack of response to first-line chemotherapy, identifying a subset of patients that could be prioritized for novel therapies. Overall, 90% (n = 169) of the patients harbored a GA which could be explored for therapeutic intervention, with 54% (n = 107) harboring more than one putative target.Key pointsThis study demonstrates the applicability of CLIA-compliant targeted FFPE sequencing for large-scale clinical trials.TP53mut is the main predictor of refractoriness or early relapse.

Abstract 4737: Comprehensive profiling of immunoglobulin sequences using hybrid capture-based next generation sequencing in B-cell hematologic malignancies

Background: Sequencing the genes encoding immunoglobulins is critical in detecting clonal cell populations as well as determining prognosis and therapeutic decisions in patients with lymphoid malignancies including B-cell leukemias, lymphomas and multiple myeloma. Current assays for identifying the rearranged immunoglobulin sequence in B-cell malignancies rely on sequence specific PCR based amplification of conserved immunoglobulin (IG) regions. We have developed a novel, hybrid capture-based approach to sequencing the immunoglobulin chains that enables identification of the heavy and light chain variable domains, complementarity-determining region (CDR) sequences and somatic hypermutation (SHM) status. Method: RNA and DNA were successfully extracted from 60 specimens, including 7 mantle cell lymphoma cell (MCL) lines and 53 clinical chronic lymphocytic leukemia (CLL) bone marrow aspirates. Adaptor-ligated DNA and cDNA sequencing libraries were captured by solution hybridization using custom bait-sets targeting the immunoglobulin variable, joining and class segments. All captured libraries were sequenced to high depth (Illumina HiSeq) in a CLIA-certified laboratory (Foundation Medicine). Results: The capture-based approach was validated using 7 MCL cell lines and 53 CLL samples profiled using a CLIA-certified commercial PCR-based assay (Invivoscribe). The immunoglobulin sequences derived from the 7 MCL cell lines were 100% concordant with identifying the published heavy and light chain variable domain and percent SHM. Comparison to 53 previously clinically tested samples showed 98% (52/53) concordance for identifying the presence of a clonal population, and 100% (39/39) concordance for identifying the IGHV domain. Comparison to 50 CLL samples previously tested for SHM resulted in 96% (48/50) overall concordance with 94% (31/33) concordant for no SHM and 100% (17/17) concordant for the presence of SHM. Additionally, secondary clones were identified in 11 samples. Conclusions: We have demonstrated that hybrid capture-based targeted DNA and RNA sequencing can be used to comprehensively characterize the immunoglobulin sequence of clonal tumor B cell populations. This capability enables quantification of SHM and identification of the variable domain, CDR3 sequence and class restriction. Integration of this methodology with comprehensive genomic profiling approaches will expand the clinical utility of such assays in patients with hematological malignancies and may provide important insights in immune oncology and response of patients to immunotherapies, including patients with solid tumors. Citation Format: Michelle K. Nahas, Lauren E. Young, Jeff Gardner, Omar Abdel-Wahab, Jie He, Amy L. Donahue, Kristina M. Knapp, Geoff A. Otto, Doron Lipson, Vincent A. Miller, Ross L. Levine, Philip J. Stephens. Comprehensive profiling of immunoglobulin sequences using hybrid capture-based next generation sequencing in B-cell hematologic malignancies. [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 4737. doi:10.1158/1538-7445.AM2015-4737

Abstract 3570: Development and validation of a clinical next generation sequencing-based assay for hematologic malignancies

Background: Next-generation sequencing (NGS) is rapidly becoming an indispensable cancer diagnostic, as it can detect most genomic alterations in a single assay from limited tissue. We developed a novel, NGS-based assay designed to provide targeted assessment of the genomic landscape of hematologic malignancies from archived FFPE, blood and bone marrow aspirate samples, sequencing both DNA and RNA to improve sensitivity for driver fusion events which are common in these tumors. Methods: The high accuracy of the assay for detection of substitutions, indels and CNAs was previously demonstrated by extensive validation studies achieving 95-99% across all alteration types with high specificity (PPV>99%) [Frampton et al, Nat Biotech, 2013]. To validate assay performance in detecting gene fusions we created reference samples by mixing 21 cell-lines with previously characterized fusions in 39 combinations representing 167 fusion events in 10-50% tumor cell fractions. In addition, we confirmed accuracy in 76 clinical hematologic FFPE and bone-marrow samples profiled for 212 substitutions, indels and fusions in 11 genes by Sanger sequencing, PCR, fragment sizing and FISH. DNA and RNA were extracted from all samples; adaptor ligated sequencing libraries were captured by solution hybridization using custom baits targeting 405 cancer related genes by DNA-seq, and 265 frequently rearranged genes by RNA-seq. All captured libraries were sequenced to high depth (Illumina HiSeq) in a CLIA-certified laboratory (Foundation Medicine), averaging 467x for DNA and 6M unique pairs for RNA. Results: On reference samples, sensitivity for detection of fusions events reached >99% for tumor cell fractions of 20-50%, and 97% for tumor fraction of 10%, all with high specificity (PPV>95%). Robust performance translated to the clinical samples: we observed a concordance rate of 98.6% relative to prior calls, with only 3/212 differing calls (2+, 1-) by NGS. 129 additional known oncogenic alterations in 57 different genes were detected in these samples, for a total of 3.1 alterations per sample. Analysis of 290 additional leukemia, lymphoma and myeloma patient samples revealed known and novel gene fusions in 15% of cases, more than half of which were identifiable only by RNA-seq. Conclusions: We describe the analytic validation of a sensitive, high throughput assay to detect somatic alterations in hundreds of genes known to be deregulated in hematologic malignancies, which can be used to identify a spectrum of somatic alterations from blood, bone marrow and paraffin embedded patient samples. We demonstrate that targeted DNA and RNA sequencing can be used to identify all classes of genomic alterations, including gene fusions, with high accuracy. This approach offers the opportunity to streamline the characterization of genomic alterations in hematologic malignancies and to expand targeted treatment options for patients with liquid tumors. Citation Format: Doron Lipson, Michelle K. Nahas, Geoff A. Otto, Jie He, Kai Wang, Kristina M. Knapp, Kristina W. Brennan, Amy L. Donahue, Lauren E. Young, Geneva Young, Alex Fichtenholtz, Jeffrey S. Ross, Roman Yelensky, Philip J. Stephens, Vincent A. Miller, Ross Levine. Development and validation of a clinical next generation sequencing-based assay for hematologic malignancies. [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 3570. doi:10.1158/1538-7445.AM2014-3570