Monosomy 7/del(7q) cause sensitivity to inhibitors of nicotinamide phosphoribosyltransferase in acute myeloid leukemia

ABSTRACT

Monosomy 7 and del(7q) (-7/-7q) are frequent chromosomal abnormalities detected in up to 10% of patients with acute myeloid leukemia (AML). Despite unfavorable treatment outcomes, no approved targeted therapies exist for patients with -7/-7q. Therefore, we aimed to identify novel vulnerabilities. Through an analysis of data from ex vivo drug screens of 114 primary AML samples, we discovered that -7/-7q AML cells are highly sensitive to the inhibition of nicotinamide phosphoribosyltransferase (NAMPT). NAMPT is the rate-limiting enzyme in the nicotinamide adenine dinucleotide salvage pathway. Mechanistically, the NAMPT gene is located at 7q22.3, and deletion of 1 copy due to -7/-7q results in NAMPT haploinsufficiency, leading to reduced expression and a therapeutically targetable vulnerability to the inhibition of NAMPT. Our results show that in -7/-7q AML, differentiated CD34+CD38+ myeloblasts are more sensitive to the inhibition of NAMPT than less differentiated CD34+CD38- myeloblasts. Furthermore, the combination of the BCL2 inhibitor venetoclax and the NAMPT inhibitor KPT-9274 resulted in the death of significantly more leukemic blasts in AML samples with -7/-7q than the NAMPT inhibitor alone. In conclusion, our findings demonstrate that AML with -7/-7q is highly sensitive to NAMPT inhibition, suggesting that NAMPT inhibitors have the potential to be an effective targeted therapy for patients with monosomy 7 or del(7q).

Erythroid/megakaryocytic differentiation confers BCL-XL dependency and venetoclax resistance in acute myeloid leukemia

Myeloid neoplasms with erythroid or megakaryocytic differentiation include pure erythroid leukemia, myelodysplastic syndrome with erythroid features, and acute megakaryoblastic leukemia (FAB M7) and are characterized by poor prognosis and limited treatment options. Here, we investigate the drug sensitivity landscape of these rare malignancies. We show that acute myeloid leukemia (AML) cells with erythroid or megakaryocytic differentiation depend on the antiapoptotic protein B-cell lymphoma (BCL)-XL, rather than BCL-2, using combined ex vivo drug sensitivity testing, genetic perturbation, and transcriptomic profiling. High-throughput screening of >500 compounds identified the BCL-XL-selective inhibitor A-1331852 and navitoclax as highly effective against erythroid/megakaryoblastic leukemia cell lines. In contrast, these AML subtypes were resistant to the BCL-2 inhibitor venetoclax, which is used clinically in the treatment of AML. Consistently, genome-scale CRISPR-Cas9 and RNAi screening data demonstrated the striking essentiality of BCL-XL-encoding BCL2L1 but not BCL2 or MCL1, for the survival of erythroid/megakaryoblastic leukemia cell lines. Single-cell and bulk transcriptomics of patient samples with erythroid and megakaryoblastic leukemias identified high BCL2L1 expression compared with other subtypes of AML and other hematological malignancies, where BCL2 and MCL1 were more prominent. BCL-XL inhibition effectively killed blasts in samples from patients with AML with erythroid or megakaryocytic differentiation ex vivo and reduced tumor burden in a mouse erythroleukemia xenograft model. Combining the BCL-XL inhibitor with the JAK inhibitor ruxolitinib showed synergistic and durable responses in cell lines. Our results suggest targeting BCL-XL as a potential therapy option in erythroid/megakaryoblastic leukemias and highlight an AML subgroup with potentially reduced sensitivity to venetoclax-based treatments.

Implementing a Functional Precision Medicine Tumor Board for Acute Myeloid Leukemia

We generated ex vivo drug-response and multiomics profiling data for a prospective series of 252 samples from 186 patients with acute myeloid leukemia (AML). A functional precision medicine tumor board (FPMTB) integrated clinical, molecular, and functional data for application in clinical treatment decisions. Actionable drugs were found for 97% of patients with AML, and the recommendations were clinically implemented in 37 relapsed or refractory patients. We report a 59% objective response rate for the individually tailored therapies, including 13 complete responses, as well as bridging five patients with AML to allogeneic hematopoietic stem cell transplantation. Data integration across all cases enabled the identification of drug response biomarkers, such as the association of IL15 overexpression with resistance to FLT3 inhibitors. Integration of molecular profiling and large-scale drug response data across many patients will enable continuous improvement of the FPMTB recommendations, providing a paradigm for individualized implementation of functional precision cancer medicine. SIGNIFICANCE: Oncogenomics data can guide clinical treatment decisions, but often such data are neither actionable nor predictive. Functional ex vivo drug testing contributes significant additional, clinically actionable therapeutic insights for individual patients with AML. Such data can be generated in four days, enabling rapid translation through FPMTB.See related commentary by Letai, p. 290.This article is highlighted in the In This Issue feature, p. 275.

Corrigendum: Adult-Onset Anti-Citrullinated Peptide Antibody-Negative Destructive Rheumatoid Arthritis Is Characterized by a Disease-Specific CD8+ T Lymphocyte Signature

[This corrects the article DOI: 10.3389/fimmu.2020.578848.].

Adult-Onset Anti-Citrullinated Peptide Antibody-Negative Destructive Rheumatoid Arthritis Is Characterized by a Disease-Specific CD8+ T Lymphocyte Signature

Rheumatoid arthritis (RA) is a complex autoimmune disease targeting synovial joints. Traditionally, RA is divided into seropositive (SP) and seronegative (SN) disease forms, the latter consisting of an array of unrelated diseases with joint involvement. Recently, we described a severe form of SN-RA that associates with characteristic joint destruction. Here, we sought biological characteristics to differentiate this rare but aggressive anti-citrullinated peptide antibody-negative destructive RA (CND-RA) from early seropositive (SP-RA) and seronegative rheumatoid arthritis (SN-RA). We also aimed to study cytotoxic CD8+ lymphocytes in autoimmune arthritis. CND-RA, SP-RA and SN-RA were compared to healthy controls to reveal differences in T-cell receptor beta (TCRβ) repertoire, cytokine levels and autoantibody repertoires. Whole-exome sequencing (WES) followed by single-cell RNA-sequencing (sc-RNA-seq) was performed to study somatic mutations in a clonally expanded CD8+ lymphocyte population in an index patient. A unique TCRβ signature was detected in CND-RA patients. In addition, CND-RA patients expressed higher levels of the bone destruction-associated TNFSF14 cytokine. Blood IgG repertoire from CND-RA patients recognized fewer endogenous proteins than SP-RA patients’ repertoires. Using WES, we detected a stable mutation profile in the clonally expanded CD8+ T-cell population characterized by cytotoxic gene expression signature discovered by sc-RNA-sequencing. Our results identify CND-RA as an independent RA subset and reveal a CND-RA specific TCR signature in the CD8+ lymphocytes. Improved classification of seronegative RA patients underlines the heterogeneity of RA and also, facilitates development of improved therapeutic options for the treatment resistant patients.

Somatic mutations and T-cell clonality in patients with immunodeficiency

Common variable immunodeficiency and other late-onset immunodeficiencies often co-manifest with autoimmunity and lymphoproliferation. The pathogenesis of most cases is elusive, as only a minor subset harbors known monogenic germline causes. The involvement of both B and T cells is however implicated. To study whether somatic mutations in CD4+ and CD8+ T cells associate with immunodeficiency, we recruited 17 patients and 21 healthy controls. Eight patients had late-onset common variable immunodeficiency and nine patients other immunodeficiency and/or severe autoimmunity. In total, autoimmunity occurred in 94% and lymphoproliferation in 65%. We performed deep sequencing of 2533 immune-associated genes from CD4+ and CD8+ cells. Deep T-cell receptor beta sequencing was used to characterize CD4+ and CD8+ T-cell receptor repertoires. The prevalence of somatic mutations was 65% in all immunodeficiency patients, 75% in common variable immunodeficiency and 48% in controls. Clonal hematopoiesis-associated variants in both CD4+ and CD8+ cells occurred in 24% of immunodeficiency patients. Results demonstrated mutations in known tumor suppressors, oncogenes, and genes that are critical for immune- and proliferative functions, such as STAT5B (two patients), C5AR1 (two patients), KRAS (one patient), and NOD2 (one patient). Additionally, as a marker of T-cell receptor repertoire perturbation, common variable immunodeficiency patients harbored increased frequencies of clones with identical complementarity determining region 3 sequences despite unique nucleotide sequences when compared to controls. In conclusion, somatic mutations in genes implicated for autoimmunity and lymphoproliferation are common in CD4+ and CD8+ cells of patients with immunodeficiency. They may contribute to immune dysregulation in a subset of immunodeficiency patients.

Molecular Basis of Mismatch Repair Protein Deficiency in Tumors from Lynch Suspected Cases with Negative Germline Test Results

Some 10–50% of Lynch-suspected cases with abnormal immunohistochemical (IHC) staining remain without any identifiable germline mutation of DNA mismatch repair (MMR) genes. MMR proteins form heterodimeric complexes, giving rise to distinct IHC patterns when mutant. Potential reasons for not finding a germline mutation include involvement of an MMR gene not predicted by the IHC pattern, epigenetic mechanism of predisposition, primary mutation in another DNA repair or replication-associated gene, and double somatic MMR gene mutations. We addressed these possibilities by germline and tumor studies in 60 Lynch-suspected cases ascertained through diagnostics (n = 55) or research (n = 5). All cases had abnormal MMR protein staining in tumors but no point mutation or large rearrangement of the suspected MMR genes in the germline. In diagnostic practice, MSH2/MSH6 (MutS Homolog 2/MutS Homolog 6) deficiency prompts MSH2 mutation screening; in our study, 3/11 index individuals (27%) with this IHC pattern revealed pathogenic germline mutations in MSH6. Individuals with isolated absence of MSH6 are routinely screened for MSH6 mutations alone; we found a predisposing mutation in MSH2 in 1/7 such cases (14%). Somatic deletion of the MSH2-MSH6 region, joint loss of MSH6 and MSH3 (MutS Homolog 3) proteins, and hindered MSH2/MSH6 dimerization offered explanations to misleading IHC patterns. Constitutional epimutation hypothesis was pursued in the MSH2 and/or MSH6-deficient cases plus 38 cases with MLH1 (MutL Homolog 1)-deficient tumors; a primary MLH1 epimutation was identified in one case with an MLH1-deficient tumor. We conclude that both MSH2 and MSH6 should be screened in MSH2/6- and MSH6-deficient cases. In MLH1-deficient cases, constitutional epimutations of MLH1 warrant consideration.

Does breast carcinoma belong to the Lynch syndrome tumor spectrum? - Somatic mutational profiles vs. ovarian and colorectal carcinomas

Inherited DNA mismatch repair (MMR) defects cause predisposition to colorectal, endometrial, ovarian, and other cancers occurring in Lynch syndrome (LS). It is unsettled whether breast carcinoma belongs to the LS tumor spectrum. We approached this question through somatic mutational analysis of breast carcinomas from LS families, using established LS-spectrum tumors for comparison. Somatic mutational profiles of 578 cancer-relevant genes were determined for LS-breast cancer (LS-BC, n = 20), non-carrier breast cancer (NC-BC, n = 10), LS-ovarian cancer (LS-OC, n = 16), and LS-colorectal cancer (LS-CRC, n = 18) from the National LS Registry of Finland. Microsatellite and MMR protein analysis stratified LS-BCs into MMR-deficient (dMMR, n = 11) and MMR-proficient (pMMR, n = 9) subgroups. All NC-BCs were pMMR and all LS-OCs and LS-CRCs dMMR. All but one dMMR LS-BCs were hypermutated (> 10 non-synonymous mutations/Mb; average 174/Mb per tumor) and the frequency of MMR-deficiency-associated signatures 6, 20, and 26 was comparable to that in LS-OC and LS-CRC. LS-BCs that were pMMR resembled NC-BCs with respect to somatic mutational loads (4/9, 44%, hypermutated with average mutation count 33/Mb vs. 3/10, 30%, hypermutated with average 88 mutations/Mb), whereas mutational signatures shared features of dMMR LS-BC, LS-OC, and LS-CRC. Epigenetic regulatory genes were significantly enriched as mutational targets in LS-BC, LS-OC, and LS-CRC. Many top mutant genes of our LS-BCs have previously been identified as drivers of unselected breast carcinomas. In conclusion, somatic mutational signatures suggest that conventional MMR status of tumor tissues is likely to underestimate the significance of the predisposing MMR defects as contributors to breast tumorigenesis in LS.

Abstract 2945: Clinical implementation of precision systems oncology in the treatment of ovarian cancer based on ex-vivo drug testing and molecular profiling

Ovarian cancer (OC) is difficult to treat and has a high mortality rate. There is a strong need for new therapies, but OC is often not the main indication for drug development activities. Hence, here we explored systematic drug repurposing based on clues from ex-vivo testing of human OC patient cells. We established patient-derived cancer cell (PDCs) cultures using ascites or tumor tissue from serous OC patients and applied them to ex vivo Drug Sensitivity and Resistance Testing (DSRT) with a panel of 528 approved and investigational oncology drugs. The representativity of the PDCs was confirmed by genomic and phenotypic profiling in comparison to the original tumor sample. Both 2D and 3D culture conditions were applied and compared for their drug responses. 9 PDCs and 11 high-grade serous OC cell lines were examined. High grade serous OC (HGSOC, 6 cases) with TP53 mutation and CCNE1, CCNE1/KRAS or MYC/KRAS amplifications showed highly resistant drug response profiles, which reflects the clinical challenges in treating this OC subtype. Some HGSOC PDCs showed vulnerability to SMAC mimetics, inhibitors of Apoptosis Protein Antagonists, (e.g. birinapant) and to prexasertib, a checkpoint kinase 1 and 2 inhibitor. In contrast, low-grade serous OC (LGSOC, 3 cases) showed subtype-specific sensitivity to several kinase inhibitors, including EGFR/Her2, MEK, mTOR and PI3K inhibitors. In a metastatic LGSOC patient, RNA-sequencing revealed a CLU-NRG1 fusion gene, which creates an autocrine activation loop of the ErbB family of receptor kinases. DSRT assay confirmed a strong sensitivity of the PDCs ex-vivo to dual-kinase inhibitors, including afatinib. Based on these data, the patient has received approved kinase inhibitors, including afatinib monotherapy followed by a combination of herceptin and pertuzumab. This strategy has managed to keep the disease in control for over 3 years as measured by clinical criteria, including imaging and serum CA125 antigen levels. In conclusion, systems precision cancer medicine with PDCs could provide a valuable approach to reveal patient-specific drug efficacies that can be translated to the clinic in real-time.

Citation Format: Astrid Murumägi, Daniela Ungureanu, Suleiman Khan, Akira Hirasawa, Mariliina Arjama, Katja Välimäki, Piia Mikkonen, Wilhelmiina Niininen, Ashwini Kumar, Samuli Eldfors, Teijo Pellinen, Vilja Pietiäinen, Andrus Mägi, Riitta Koivisto-Korander, Johanna Tapper, Mikko Loukovaara, Tero Aittokallio, Ralf Bützow, Olli Kallioniemi. Clinical implementation of precision systems oncology in the treatment of ovarian cancer based on ex-vivo drug testing and molecular profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2945.

Abstract 458: Precision systems medicine in acute myeloid leukemia: real-time translation of tailored therapeutic opportunities arising from ex-vivo drug sensitivity testing and molecular profiling

Acute myeloid leukemia (AML) is an aggressive disease of clonal hematopoietic progenitor cells. Here, we applied ex-vivo drug sensitivity and resistance testing on AML patient cells with 362 emerging and 153 approved cancer drugs together with genomic and transcriptomic profiling to identify and tailor therapies for patients with advanced disease. Ex-vivo testing with freshly isolated patient cells revealed cancer-specific efficacies of approved drugs in 97% of the 164 patient cases, including 47% of the cases with no actionable driver mutations. We identified 142 statistically significant associations between drug responses and somatic mutations, including increased sensitivity to JAK inhibitors in patients with NPM1 mutations. Transcriptomic profiles predicted drug responses better than genomics and helped to identify additional response markers, especially beyond mutations. For example, overexpression of HOX family genes was associated with sensitivity to JAK inhibitors in patients with NPM1 mutation. In a prospective study, we translated the functional drug response and molecular profile data to the clinic and suggested tailored therapy with targeted drugs for 26 relapsed or refractory AML patients. In an observational intervention study, acting on these recommendations resulted in a temporary complete clinical remission or leukemia-free state in 39% of the cases. In summary, we conclude that ex-vivo testing of drugs on patient AML cells i) revealed clinically actionable drug efficacies in almost all AML patients, including patients with no actionable mutations, ii) predicted cases with actionable driver mutations with no pharmacological dependency on the target, and iii) enabled real-time tailoring of therapy with 39% clinical response rate in chemorefractory advanced AML. Taken together, we believe this real-time systems medicine approach could become a powerful strategy for tailoring therapies for individual patients in the future.

Citation Format: Disha Malani, Ashwni Kumar, Bhagwan Yadav, Mika Kontro, Swapnil Potdar, Oscar Bruck, Säri Kytölä, Jani Saarela, Samuli Eldfors, Riikka Karjalainen, Muntasir M. Majumder, Imre Västrik, Pekka Ellonen, Matti Kankainen, Minna Suvela, Siv Knappila, Alun Parson, Aino Palva, Pirkko Mattila, Evgeny Kulesskiy, Laura Turunen, Karoliina Laamanen, Elina Lehtinen, Maria Nurmi, Katja Suomi, Astrid Muruimägi, Bjorn T. Gjertsen, Satu Mustjoki, Simon Anders, Maija Wolf, Tero Aittokallio, Krister Wennerberg, Caroline Heckman, Kimmo Porkka, Olli Kallioniemi. Precision systems medicine in acute myeloid leukemia: real-time translation of tailored therapeutic opportunities arising from ex-vivo drug sensitivity testing and molecular profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 458.

Epidemiological, clinical and molecular characterization of Lynch-like syndrome: A population-based study

Colorectal carcinomas that are mismatch repair (MMR)-deficient in the absence of MLH1 promoter methylation or germline mutations represent Lynch-like syndrome (LLS). Double somatic events inactivating MMR genes are involved in the etiology of LLS tumors. Our purpose was to define the clinical and broader molecular hallmarks of LLS tumors and the population incidence of LLS, which remain poorly characterized. We investigated 762 consecutive colorectal carcinomas operated in Central Finland in 2000-2010. LLS cases were identified by a stepwise protocol based on MMR protein expression, MLH1 methylation and MMR gene mutation status. LLS tumors were profiled for CpG Island Methylator Phenotype (CIMP) and somatic mutations in 578 cancer-relevant genes. Among 107 MMR-deficient tumors, 81 (76%) were attributable to MLH1 promoter methylation and 9 (8%) to germline mutations (Lynch syndrome, LS), leaving 14 LLS cases (13%) (3 remained unclassified). LLS carcinomas were diagnosed at a mean age of 65 years (vs. 44 years in LS, p < 0.001), had a proximal to distal ratio of 1:1, and all were BRAF V600E-negative. Two somatic events in MMR genes were identifiable in 11 tumors (79%). As novel findings, the tumors contained an average of 31 nonsynonymous somatic mutations/Mb and 13/14 were CIMP-positive. In conclusion, we establish the epidemiological, clinical and molecular characteristics of LLS in a population-based study design. Significantly more frequent CIMP-positivity and lower rates of somatic mutations make a distinction to LS. The absence of BRAF V600E mutation separates LLS colorectal carcinomas from MLH1-methylated colorectal carcinomas with CIMP-positive phenotype.

Clonal heterogeneity influences drug responsiveness in renal cancer assessed by ex vivo drug testing of multiple patient-derived cancer cells

Renal cell cancer (RCC) has become a prototype example of the extensive intratumor heterogeneity and clonal evolution of human cancers. However, there is little direct evidence on how the genetic heterogeneity impacts on drug response profiles of the cancer cells. Our goal was to determine how genomic clonal evolution impacts drug responses. Finding from our study could help to define the challenge that clonal evolution poses on cancer therapy. We established multiple patient-derived cells (PDCs) from different tumor regions of four RCC patients, verified their clonal relationship to each other and to the uncultured tumor tissue by genome sequencing. Furthermore, comprehensive drug-sensitivity testing with 460 oncological drugs was performed on all PDC clones. The PDCs retained many cancer-specific copy number alterations and mutations in driver genes such as VHL, PBRM1, PIK3C2A, KMD5C and TSC2 genes. The drug testing highlighted vulnerability in the PDCs toward approved RCC drugs, such as the mTOR-inhibitor temsirolimus, but also novel sensitivities were uncovered. The individual PDC clones from different tumor regions in a patient showed distinct drug-response profiles, suggesting that genomic heterogeneity contributes to the variability in drug responses. Studies of multiple PDCs from a patient with cancer are informative for elucidating cancer heterogeneity and for the determination on how the genomic evolution is manifested in cancer drug responsiveness. This approach could facilitate tailoring of drugs and drug combinations to individual patients.

Abstract 2199: Establishment and high-throughput drug testing of multiple patient-derived cells from each renal cancer; intratumor heterogeneity of drug response and implications for precision medicine

Renal cell cancer (RCC) has become a prototype example of the extensive intra-tumor genetic heterogeneity and clonal evolution of human cancers. There is, however, little information on how the genetic heterogeneity will impact on drug responsiveness of the cancer cells. Establishment of multiple patient-derived cells (PDCs) from individual patients may help us to understand genomic clonal evolution pathways in cancer, explore intratumor heterogeneity of drug response across tumors, as well as help to define combinatorial treatments needed to target multiple subclones in a cancer patient. Here, we established several PDCs from different tumor regions of four RCC patients, verified clonal relationships of the PDCs with each others and with the uncultured tumor tissue by genome sequencing. PDCs retained cancer-specific copy number alterations and mutations in driver genes such as VHL, PBRM1, PIK3C2A, KMD5C and TSC2 genes, but also showed differences indicating genetic heterogeneity and clonal evolution, and thus generating a set of natural isogenic variants. Comprehensive drug-sensitivity testing of the PDC clones with 460 oncology drugs was performed. The drug testing analysis identified shared vulnerability of the PDCs towards several approved RCC drugs, such as mTOR-inhibitor (temsirolimus) and multi-kinase-inhibitor (pazopanib). The individual RCC PDC clones from different tumor regions in one patient showed distinct drug response profiles, confirming that genomic heterogeneity contributes to the variability in drug responses. We developed a capability to map drug response evolution on top of genomic evolution in cancer. In conclusion, our study suggested that comparison of drug response profiles among multiple (isogenic) PDC variants from a cancer patient may be informative for i) assessing intratumor heterogeneity in drug response ii) elucidating pharmacogenomic biomarkers among natural isogenic cell variants and iii) identifying drugs and drug combinations that may kill the multiple cancer subclones in a patient. Funding: EU-FP7-Systems Microscopy Network of Excellence, Sigrid Juselius Foundation, Cancer Society of Finland, Academy of Finland, the Magnus Ehrnrooth Foundation, TEKES FiDiPro Fellow Grant and Knut and Alice Wallenberg Foundation.

Citation Format: Khalid Saeed, Poojitha Ojamies, Teijo Pellinen, Samuli Eldfors, Riku Turkki, Johan Lundin, Harry Nisen, Petrus Järvinen, Kimmo Taari, Taija af Hällström, Antti Rannikko, Tuomas Mirtti, Olli Kallioniemi, Päivi Östling. Establishment and high-throughput drug testing of multiple patient-derived cells from each renal cancer; intratumor heterogeneity of drug response and implications for precision medicine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2199.

Abstract 5369: Tumorigenesis in Lynch syndrome: Somatic mutation profiles compared to sporadic counterparts

Lynch syndrome (LS) is the most prevalent cancer predisposition syndrome in which germline mutation in one of four DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2 causes significantly increased lifetime risks of colorectal, endometrial, ovarian, and other cancers. Whether or not breast cancer is part of LS tumor spectrum is currently debated. Moreover, the reasons for organ selectivity in germline mutation carriers are unknown. We have reported that breast carcinoma from LS individuals resembles common breast carcinoma in many respects, but differs with respect to genomic instability (Lotsari et al. 2012, Cancer Res.). To extend these preliminary observations, we are now carrying out an in-depth investigation into the spectra of somatic mutations in LS and sporadic breast carcinomas. All available breast carcinomas among 300 LS families from the nation-wide Hereditary Colon Cancer Registry of Finland have been identified and the tumors investigated for MMR status, DNA methylator phenotype, mechanisms of two-allele inactivation for MMR genes, and somatic mutation status. For the latter, we use massive parallel sequencing as described in our recent publication (Porkka et al. 2017, Oncotarget). To define the unique vs. shared molecular features of LS breast tumorigenesis, profiles of somatic alterations in LS breast carcinomas are compared to those of established LS spectrum carcinomas (colorectal and ovarian) as well as sporadic breast carcinomas with sequence information available from large electronic data-sets. Of 14 LS breast carcinoma samples, 9 (64 %) were MMR-deficient and 5 (36 %) MMR-proficient. This contrasts with LS colorectal and ovarian carcinomas, all of which were MMR-deficient (p=0.0012). MMR-deficient LS breast carcinomas harbored an average of 783 non-synonymous mutations and MMR-proficient tumors 555 mutations (statistically non-significant). In contrast to colorectal and ovarian carcinomas, in which loss of heterozygosity (LOH) or somatic MMR gene mutation provided a second hit consistent with two-hit inactivation in 89 % (25/28) of the tumors, a detectable second hit (mainly LOH) was present in only 43 % (6/14) of breast carcinomas (p=0.0025). Genes harboring high-frequency mutations in at least one-third of tumors were regarded candidates for driver genes. There were 133 such genes in LS colorectal carcinomas, 10 in ovarian carcinomas, and 18 in breast carcinomas. Genes involved in epigenetic regulation were significantly enriched in all three tumor types. In addition, a significant enrichment of NOTCH signaling associated genes characterized LS breast carcinomas. This research is likely to shed light to the mechanisms of organ-specific cancer susceptibility in germline carriers of MMR gene mutations. Our results are expected to guide the surveillance and other clinical management of LS individuals with breast carcinoma.

Citation Format: Noora Porkka, Alisa Olkinuora, Satu Mäki-Nevala, Samuli Eldfors, Päivi Peltomäki. Tumorigenesis in Lynch syndrome: Somatic mutation profiles compared to sporadic counterparts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5369.

Abstract 3899: Discovery and clinical implementation of individualized therapies in acute myeloid leukemia based on ex vivo drug sensitivity testing and multi-omics profiling

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by multiple molecular subtypes and lack of effective targeted therapies. Here, we performed extensive molecular profiling and ex vivo drug testing with 515 approved and emerging cancer drugs on 164 AML patient samples. The aim was to i) assign individualized treatment options to advanced AML patients in real time, ii) explore drug response patterns across the molecular subtypes of AML and iii) identify opportunities to repurpose existing and emerging cancer drugs.

Bone marrow samples (n=164) from 129 consecutive AML patients and 17 healthy donors were studied from the Helsinki University Hospital and the Haukeland University Hospital, Bergen. Mononuclear cells were resuspended either in mononuclear cell medium (MCM) or stroma conditioned medium (CM) and tested for drug sensitivity and resistance as previously described (PMID: 24056683) and studied by exome and transcriptome sequencing. The study protocol allowed us to return data to the clinician for consideration of novel treatment options. For the meta-analysis of associations between drug responses and molecular and clinical parameters, Wilcoxon signed ranked test and logistic regression were applied.

Clustering of all patient samples based on ex vivo drug response patterns in both media types identified 7 distinct functional groups of AML. For example, a subgroup of samples was highly resistant to chemotherapeutics and all targeted drugs except BCL-2 inhibitors. The differences in drug responses in the two media types highlighted the importance of assay conditions for ex vivo drug testing. Strong clustering of several drugs in the same drug classes was often observed as well as clustering across different classes, for example between BET (JQ1, I-BET151, birabresib) and MEK (trametinib, cobimetinib) inhibitors. About 24 percent of the FLT3 negative AML patients manifested strong ex vivo sensitivity to glucocorticoids, highlighting a potential drug repositioning opportunity in this subset of AML patients. Overall, we identified 320 significant associations between drugs and mutated driver genes including association between NPM1 mutation and sensitivity to JAK inhibitors.

Altogether, targeted treatment opportunities were clinically tested in 25 occasions in chemorefractory AML patients. The tailored clinical therapy led to transient complete remission or leukemia free state in 36% (9/25) of these cases.

In conclusion, we discovered and clinically implemented individualized therapeutic options for AML patients, which resulted in a 36% clinical responses in a non-randomized proof-of-concept study. The associations identified between ex-vivo drug response and driver mutations provided novel drug repositioning opportunities in specific molecular subtypes.

Citation Format: Disha Malani, Ashwini Kumar, Bhagwan Yadav, Mika Kontro, Swapnil Potdar, Oscar Brück, Sari Kytölä, Jani Saarela, Samuli Eldfors, Poojitha Ojamies, Karjalainen Riikka, Muntasir Mamun Majumder, Imre Västrik, Pekka Ellonen, Matti Kankainen, Minna Suvela, Siv Knappila, Alun Parson, Aino Palva, Pirkko Mattila, Evgeny Kulesskiy1, Laura Turunen, Karoliina Laamanen, Elina Lehtinen, Piia Mikkonen, Maria Nurmi, Sanna Timonen, Astrid Murumägi, Bjorn Tore Gjersten, Satu Mustjoki, Tero Aittokallio, Krister Wennerberg, Simon Anders, Maija Wolf, Caroline Heckman, Kimmo Porkka, Olli Kallioniemi. Discovery and clinical implementation of individualized therapies in acute myeloid leukemia based on ex vivo drug sensitivity testing and multi-omics profiling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3899.

Abstract 3277: Identification of internal tandem duplication within the FLT3 gene from AML patient next-generation sequence data

Introduction

The presence of the Fms Related Tyrosine Kinase 3 (FLT3) internal tandem duplication (FLT3-ITD) is associated with a poor prognosis and an increased rate of relapse in acute myeloid leukemia (AML). Identification of FLT3-ITD from next-generation sequencing (NGS) data is currently impeded by lack of reliable algorithms to identify large insertions. Therefore, despite the wide adoption of NGS in recent years, FLT3-ITD mutations are still being detected with PCR/electrophoresis assays which are expensive and time consuming. Algorithms that reliably identify FLT3-ITDs from NGS data are urgently required.

Methods

We developed a computational algorithm for FLT3-ITD calling from next-generation sequencing data. The method is based on iterative realignment of unaligned sequence read fragments. The algorithm uses sequence reads mapped to FLT3 exon 14 and unmapped sequence reads sharing similarity (at least 25bp aligned with the Smith-Waterman algorithm) with FLT3 exon 14. The procedure has two steps: (1) Smith-Waterman local pairwise alignment of each read to the reference sequence, and (2) trimming unaligned parts of each read. If a read has an unaligned part(s) identified at step 2, then these are returned to the step 1, and the whole procedure is repeated. The procedure is iterated until each read is fully-aligned to the reference sequence. A sample is considered to be ITD negative if all reads are fully-aligned after the first iteration. Otherwise, the algorithm returns fragmentized reads aligned to the reference sequence. This output can be used to discriminate between ITD positive and negative samples based on the pattern produced by aligned fragments of the reads. Reads coming from FLT3-ITD have an intrinsic property to cluster at the boundaries of the duplicated region; therefore, samples with reads ends clustering at a shared genomic position are considered ITD positive. We calculate the p-value of reads ends clustering at the same genomic position using generalized birthday-problem theory.

Results

We analyzed a total of 273 AML samples from 125 patients. The algorithm assigned 221 samples (~81%) as FLT3-ITD negative, forty-seven (~17%) samples as FLT3-ITD positive and 5 samples (~1.8%) were assigned as undefined (with a p-value between 0.005 and 0.1). We visually inspected the patterns produced by realigned fragments to assign a FLT3-ITD status for each of the undefined samples.

We compared these results with FLT3-ITD status determined by a clinical PCR/electrophoresis assay. Our algorithm was able to recall all the 13 samples where ITD was detected by the clinical assay. Notably, FLT3-ITD mutation in two samples were detected with our method but not by the clinical assay.

Conclusions

1. Our novel algorithm enables accurate identification of FLT3-ITD mutations from NGS sequence data.

2. The method was able to detect FLT3-ITD positive samples that were missed by the clinical assay.

Citation Format: Yevhen Akimov, Samuli Eldfors, Disha Malani, Tero Aittokallio, Caroline Heckman. Identification of internal tandem duplication within the FLT3 gene from AML patient next-generation sequence data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3277.

Converging endometrial and ovarian tumorigenesis in Lynch syndrome: Shared origin of synchronous carcinomas

OBJECTIVE

The diagnosis of carcinoma in both the uterus and the ovary simultaneously is not uncommon and raises the question of synchronous primaries vs. metastatic disease. Targeted sequencing of sporadic synchronous endometrial and ovarian carcinomas has shown that such tumors are clonally related and thus represent metastatic disease from one site to the other. Our purpose was to investigate whether or not the same applies to Lynch syndrome (LS), in which synchronous cancers of the gynecological tract are twice as frequent as in sporadic cases, reflecting inherited defects in DNA mismatch repair (MMR).

METHODS

MMR gene mutation carriers with endometrial or ovarian carcinoma or endometrial hyperplasia were identified from a nationwide registry. Endometrial (n = 35) and ovarian carcinomas (n = 23), including 13 synchronous carcinoma pairs, were collected as well as endometrial hyperplasias (n = 56) and normal endometria (n = 99) from a surveillance program over two decades. All samples were studied for MMR status, ARID1A and L1CAM protein expression and tumor suppressor gene promoter methylation, and synchronous carcinomas additionally for somatic mutation profiles of 578 cancer-relevant genes.

RESULTS

Synchronous carcinomas were molecularly concordant in all cases. Prior or concurrent complex (but not simple) endometrial hyperplasias showed a high degree of concordance with endometrial or ovarian carcinoma as the endpoint lesion.

CONCLUSIONS

Our investigation suggests shared origins for synchronous endometrial and ovarian carcinomas in LS, in analogy to sporadic cases. The similar degrees of concordance between complex hyperplasias and endometrial vs. ovarian carcinoma highlight converging pathways for endometrial and ovarian tumorigenesis overall.

Aggressive natural killer-cell leukemia mutational landscape and drug profiling highlight JAK-STAT signaling as therapeutic target

Aggressive natural killer-cell (NK-cell) leukemia (ANKL) is an extremely aggressive malignancy with dismal prognosis and lack of targeted therapies. Here, we elucidate the molecular pathogenesis of ANKL using a combination of genomic and drug sensitivity profiling. We study 14 ANKL patients using whole-exome sequencing (WES) and identify mutations in STAT3 (21%) and RAS-MAPK pathway genes (21%) as well as in DDX3X (29%) and epigenetic modifiers (50%). Additional alterations include JAK-STAT copy gains and tyrosine phosphatase mutations, which we show recurrent also in extranodal NK/T-cell lymphoma, nasal type (NKTCL) through integration of public genomic data. Drug sensitivity profiling further demonstrates the role of the JAK-STAT pathway in the pathogenesis of NK-cell malignancies, identifying NK cells to be highly sensitive to JAK and BCL2 inhibition compared to other hematopoietic cell lineages. Our results provide insight into ANKL genetics and a framework for application of targeted therapies in NK-cell malignancies.

Aggressive natural killer-cell leukemia (ANKL) has few targeted therapies. Here ANKL patients are reported to harbor STAT3, RAS-MAPK pathway, DDX3X and epigenetic modifier mutations; and drug sensitivity profiling uncovers the importance of the JAK-STAT pathway, revealing potential ANKL therapeutic targets.

Sequencing of Lynch syndrome tumors reveals the importance of epigenetic alterations

Genomic instability and epigenetic aberrations are important classifiers of human tumors, yet, their interrelations are poorly understood. We used Lynch syndrome (LS) to address such relationships. Forty-five tumors (11 colorectal adenomas, 18 colorectal carcinomas, and 16 ovarian carcinomas) were profiled for CpG Island Methylator Phenotype (CIMP) and somatic mutations. All tumors showed high-degree microsatellite instability. Panel sequencing of 578 cancer-relevant genes revealed the average number of 1433, 1124, and 657 non-synonymous somatic mutations per colorectal adenoma, colorectal carcinoma, and ovarian carcinoma, respectively. Genes harboring mutations with allele frequency 25 % or higher in at least 31 % of tumors were regarded to be possible drivers. Among 72 and 10 such genes identified in colorectal and ovarian tumors, respectively, the most frequently mutated genes BRD4 and MLL2 (62 % of colorectal tumors) and ARID1A (50 % of ovarian carcinomas) are involved in epigenetic regulation. The total number of somatic mutations or mutant genes per tumor were significantly associated with CIMP. Our results suggest that even in an inherited disease, tumor type-specific epigenetic changes are significant and may result from regulatory changes (CIMP) or structural events (mutations of epigenetic regulatory genes). The findings are clinically relevant since many of the affected pathways can be therapeutically targeted.

Discovery of novel drug sensitivities in T-PLL by high-throughput ex vivo drug testing and mutation profiling

T-cell prolymphocytic leukemia (T-PLL) is a rare and aggressive neoplasm of mature T-cells with an urgent need for rationally designed therapies to address its notoriously chemo-refractory behavior. The median survival of T-PLL patients is <2 years and clinical trials are difficult to execute. Here we systematically explored the diversity of drug responses in T-PLL patient samples using an ex vivo drug sensitivity and resistance testing platform and correlated the findings with somatic mutations and gene expression profiles. Intriguingly, all T-PLL samples were sensitive to the cyclin-dependent kinase inhibitor SNS-032, which overcame stromal-cell-mediated protection and elicited robust p53-activation and apoptosis. Across all patients, the most effective classes of compounds were histone deacetylase, phosphoinositide-3 kinase/AKT/mammalian target of rapamycin, heat-shock protein 90 and BH3-family protein inhibitors as well as p53 activators, indicating previously unexplored, novel targeted approaches for treating T-PLL. Although Janus-activated kinase-signal transducer and activator of transcription factor (JAK-STAT) pathway mutations were common in T-PLL (71% of patients), JAK-STAT inhibitor responses were not directly linked to those or other T-PLL-specific lesions. Overall, we found that genetic markers do not readily translate into novel effective therapeutic vulnerabilities. In conclusion, novel classes of compounds with high efficacy in T-PLL were discovered with the comprehensive ex vivo drug screening platform warranting further studies of synergisms and clinical testing.

Abstract 410: Identifying ovarian cancer specific targeted drugs using high-throughput drug sensitivity profiles of primary cancer cells

Ovarian cancer (OvCa) is the sixth most common cancer in women and leading cause of death from gynecologic diseases. Poor prognosis in OvCa is due to late diagnosis and acquired resistance to the commonly used platinum-based regimens. A significant setback for OvCa treatment is the lack of reliable biomarkers and effective targeted therapies. In order to discover novel therapeutic opportunities with approved and emerging drugs for OvCa, we have established primary cultures using ascites or tumor tissue samples from chemo-refractory ovarian cancer patients for ex vivo Drug Sensitivity and Resistance Testing (DSRT) and genomic profiling. In addition, we have performed DSRT with 31 established OvCa cell lines. Comparison of the drug sensitivity profiles of ten primary cancer cell cultures and 31 OvCa cell lines revealed previously unanticipated cancer selective drug vulnerabilities. Several drug groups were identified suggesting that the sensitive samples were addicted to the corresponding signaling networks. For example, in a 53-year old chemorefractory low grade serous OvCa patient, genomic and transcriptomic analyses revealed a fusion gene of NRG-1, a target that was recently reported to involve the NRG1/ERBB3 activation loop in OvCa. We found high expression of ERBB2 and ERBB3 by RNA-seq as well as high levels of phospho-ERBB3, phospho-ERBB2 and phospho-EGFR by immunohistochemistry. In agreement with the molecular mechanism, DSRT analysis identified significant sensitivity of primary cancer cells to EGFR inhibitors, such as erlotinib and to dual EGFR and Her2 inhibitor afatinib. The patient has received combination therapy of gemcitabine and erlotinib during nine months, followed by afatinib monotheraphy that has lead to complete remission after six months treatment. We have detected activated NRG1/ERBB3 activation loop also in several additional ovarian cancer patient cases, highlighting the importance of this signaling pathway in ovarian cancer pathogenesis. Our study reveals that a subset of serous ovarian cancer patients with activating NRG1/ERBB3 signaling loop have clinical benefits from repurposing dual EGFR/Her2 inhibitor afatinib, providing a basis for the clinical use of EGFR and dual EGFR/Her2 tyrosine kinase inhibitors in clinical treatment. In conclusion, DSRT technology together with molecular profiling provides a powerful strategy to identify tumor driver signals and select clinically actionable inhibitors. Hence, this type of systems medicine approach can significantly improve the power of mainly genomics-oriented personalized medicine approaches.

Citation Format: Astrid Murumägi, Akira Hirasawa, Suleiman Khan, Daniela Ungureanu, Mariliina Arjama, Teijo Pellinen, Samuli Eldfors, Riitta Koivisto-Korander, Arto Leminen, Ralf Bützow, Tero Aittokallio, Olli Kallioniemi. Identifying ovarian cancer specific targeted drugs using high-throughput drug sensitivity profiles of primary cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 410. doi:10.1158/1538-7445.AM2017-410

Abstract 424: Landscape of somatic mutations in drug-resistant acute myeloid leukemia

Introduction: Most patients with acute myeloid leukemia (AML) initially respond to cytarabine-anthracycline induction chemotherapy. However, in many patients, the disease recurs in a lethal drug-resistant form. Somatic mutations underlying the pathogenesis of AML have been extensively characterized by sequencing of newly diagnosed AMLs. However, the mutations driving therapy resistance and disease progression at relapse have not been well characterized. In this study, we have exome sequenced a cohort of relapsed and refractory AMLs and compared the landscape of somatic mutations at relapse to diagnosis phase AMLs to identify mutations that contribute to therapy resistance and disease progression.

Materials and Methods: We performed exome sequencing of diagnosis phase AMLs (n=70) and relapsed or primary refractory AMLs (n=54). Patients with AML M3 subtype were excluded from the study. Paired diagnosis and relapse samples were available from 27 patients. A skin biopsy was used as the germline control. Nine patients had received an allogeneic hematopoietic stem cell transplant before relapse. Somatic mutations were called using varscan2 and copy number aberrations using copyCat. Since the identification of large insertions from next-generation sequencing data remains challenging using existing algorithms, FLT3 internal tandem duplications (FLT3-ITDs) were identified using a novel custom algorithm optimized for FLT3-ITD detection. Population variants were filtered out to remove donor-derived germline variants in chimeric post-transplant relapse samples.

Results: Comparison of somatic mutation frequencies in diagnosis and relapse and refractory samples showed that on average relapsed tumors have a higher number of driver mutations than tumors at diagnosis. WT1, TP53, CBL, IDH1 and PTPN11 were mutated at a higher frequency in relapsed samples than at diagnosis, with 13 %, 11 %, 11 %, 9 % and 9 % of relapsed or refractory samples and 4 %, 6 %, 3 %, 4 % and 7 % of diagnosis mutated respectively. Analysis of paired diagnosis-relapse samples showed that in patients with WT1, CBL or PTPN11 mutation at diagnosis the second allele is frequently mutated or lost due to uniparental disomy occurring at relapse.

Conclusions: On average relapsed AMLs have a higher number of driver mutations than diagnosis phase AMLs indicating that acquisition of additional driver mutations contributes to relapse. AMLs frequently acquire additional mutations in the same genes and pathways that already harbored mutations at diagnosis.

Citation Format: Samuli Eldfors, Mika Kontro, Yevhen Akimov, Olli Kallioniemi, Kimmo Porkka, Caroline Heckman. Landscape of somatic mutations in drug-resistant acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 424. doi:10.1158/1538-7445.AM2017-424

Enhanced sensitivity to glucocorticoids in cytarabine-resistant AML

We sought to identify drugs that could counteract cytarabine resistance in acute myeloid leukemia (AML) by generating eight resistant variants from MOLM-13 and SHI-1 AML cell lines by long-term drug treatment. These cells were compared with 66 ex vivo chemorefractory samples from cytarabine-treated AML patients. The models and patient cells were subjected to genomic and transcriptomic profiling and high-throughput testing with 250 emerging and clinical oncology compounds. Genomic profiling uncovered deletion of the deoxycytidine kinase (DCK) gene in both MOLM-13- and SHI-1-derived cytarabine-resistant variants and in an AML patient sample. Cytarabine-resistant SHI-1 variants and a subset of chemorefractory AML patient samples showed increased sensitivity to glucocorticoids that are often used in treatment of lymphoid leukemia but not AML. Paired samples taken from AML patients before treatment and at relapse also showed acquisition of glucocorticoid sensitivity. Enhanced glucocorticoid sensitivity was only seen in AML patient samples that were negative for the FLT3 mutation (P=0.0006). Our study shows that development of cytarabine resistance is associated with increased sensitivity to glucocorticoids in a subset of AML, suggesting a new therapeutic strategy that should be explored in a clinical trial of chemorefractory AML patients carrying wild-type FLT3.

Abstract 2378: Responses of AML patients to tailored drug regimens: monitoring cancer subclones by ultra-deep resequencing

As part of our individualized systems medicine (ISM) program, personalized treatment options are provided to clinicians based on in-depth genomic and molecular profiling as well as ex vivo drug sensitivity and resistance testing (DSRT) of leukemia patients (Pemovska et al. Cancer Discovery, 2013). In chemorefractory AML patients (n = 17), the ISM strategy has resulted in up to 35% response rate when individually selected targeted drugs have been applied in patient treatment. The responses achieved have, however, been transient and patients have typically relapsed quickly. Here, we aimed to understand the molecular basis of such treatment failures by quantitating the kinetics of individual cancer subclones before, during and after targeted treatments, as well as at the time of relapse and disease progression. Longitudinal serial samples from 13 AML patients were studied at multiple steps during leukemia progression and drug response. Clonal evolution of leukemic subclones was studied by both exome sequencing to get genome-wide overviews of disease progression, as well as by ultra-deep (&gt;10,000x) amplicon resequencing with unique molecular identifiers to identify rare clones carrying specific cancer-relevant mutations.

Nine of the 13 patients (69%) had multiple clones by exome sequencing and displayed branching evolution. In five patients who received treatment with targeted inhibitors we observed a significant differential therapeutic response of the individual AML subclones during therapy. In some cases, this could be directly attributed to the molecular mechanisms of drug response and resistance, such as the loss of NF1 in a subclone leading to cytarabine resistance or the loss of the FLT3-positive subclone in a patient responding to sunitinib treatment. Despite a prominent drug response at the level of the subclone carrying the driver mutations, in all these patients a new subclone emerged that led to progression of the disease. In three of the patients, the dominant clone appearing at relapse was already detected as a minor subclone in the diagnostic sample by amplicon resequencing. Amplicon sequencing enabled us to detect these minor subclones (down to 0,5% frequency) that were missed by exome sequencing. The results suggest that relapses in AML may arise because the drug-resistant subclone exists already before the onset of therapy.

Overall, it is necessary to quantify tumor evolution and drug responses at the level of cancer subclones. Ultra-deep resequencing can be used to monitor drug responses at the subclone level, even at very low frequencies. This could facilitate early detection of small subclones with important prognostic implications, as well as the design of intelligent combinations of targeted drugs that could block such subclones.

Citation Format: Poojitha N Ojamies, Mika Kontro, Henrik Edgren, Pekka Ellonen, Sonja Lagstrom, Henrikki Almusa, Timo Miettinen, Samuli Eldfors, David Tamborero, Krister Wennerberg, Caroline Heckman, Kimmo Porkka, Maija Wolf, Olli Kallioniemi. Responses of AML patients to tailored drug regimens: monitoring cancer subclones by ultra-deep resequencing. [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 2378.

Abstract 4679: Acquisition of cytarabine resistance leads to increased glucocorticoid sensitivity in AML

Acquired resistance to standard chemotherapeutic agents, such as cytarabine, is a major challenge in the treatment of acute myeloid leukemia (AML). Here, we hypothesized that development of resistance to one chemotherapeutic agent may lead to increased sensitivity to other drugs. Hence, we sought to identify novel drug vulnerabilities that arise during the development of cytarabine resistance using both cytarabine resistant AML cell lines and samples from AML patients who had relapsed during cytarabine containing chemotherapy.

We developed resistant variants of AML cell lines MOLM-13 and SHI-1 by long-term drug treatment with increasing doses of cytarabine. Profiling data from the in vitro generated cytarabine resistant cell line variants were systematically compared with corresponding data from 31 chemorefractory AML patient samples. All samples were subjected to genomic and transcriptomic profiling and high-throughput drug sensitivity and resistance testing with a panel of 250 chemical compounds (each in five doses).

Cytarabine resistant AML cell line variants and patient samples showed co-resistance to other nucleoside analogues, such as cladribine, clofarabine and gemcitabine. Genomic profiling showed deletion of the deoxycytidine kinase gene DCK, a well-known genetic lesion related to cytarabine resistance, in both MOLM-13 and SHI-1 cytarabine resistant cell lines and in one chemorefractory AML patient. Importantly, comprehensive drug testing revealed that cytarabine resistant SHI-1 cell variants developed increased sensitivity to glucocorticoids, such as dexamethasone, methylprednisolone and prednisolone when compared to parental cells. This was accompanied by up-regulation of the glucocorticoid receptor NR3C1. We also observed acquisition of glucocorticoid sensitivity in paired samples from two AML patient cases who had relapsed after cytarabine containing chemotherapy. Systematic ex vivo drug testing of 31 relapsed and chemorefractory AML patient samples showed high sensitivity to dexamethasone in five (20%) and to prednisolone and methylprednisolone in four (13%) patient samples.

In conclusion, our results from both cytarabine resistant AML cell lines and chemorefractory patient samples indicate that a subset of AML samples develop sensitivity to glucocorticoids. This novel finding indicates the need of detailed investigation of glucocorticoid efficacy in the clinic.

Citation Format: Disha Malani, Astrid Murumägi, Bhagwan Yadav, Mika Kontro, Samuli Eldfors, Ashwini Kumar, Krister Wennerberg, Caroline Heckman, Kimmo Porkka, Maija Wolf, Tero Aittokallio, Olli Kallioniemi. Acquisition of cytarabine resistance leads to increased glucocorticoid sensitivity in AML. [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 4679.

Systematic drug screening reveals specific vulnerabilities and co-resistance patterns in endocrine-resistant breast cancer

Background

The estrogen receptor (ER) inhibitor tamoxifen reduces breast cancer mortality by 31 % and has served as the standard treatment for ER-positive breast cancers for decades. However, 50 % of advanced ER-positive cancers display de novo resistance to tamoxifen, and acquired resistance evolves in 40 % of patients who initially respond. Mechanisms underlying resistance development remain poorly understood and new therapeutic opportunities are urgently needed. Here, we report the generation and characterization of seven tamoxifen-resistant breast cancer cell lines from four parental strains.

Methods

Using high throughput drug sensitivity and resistance testing (DSRT) with 279 approved and investigational oncology drugs, exome-sequencing and network analysis, we for the first time, systematically determine the drug response profiles specific to tamoxifen resistance.

Results

We discovered emerging vulnerabilities towards specific drugs, such as ERK1/2-, proteasome- and BCL-family inhibitors as the cells became tamoxifen-resistant. Co-resistance to other drugs such as the survivin inhibitor YM155 and the chemotherapeutic agent paclitaxel also occurred.

Conclusion

This study indicates that multiple molecular mechanisms dictate endocrine resistance, resulting in unexpected vulnerabilities to initially ineffective drugs, as well as in emerging co-resistances. Thus, combatting drug-resistant tumors will require patient-tailored strategies in order to identify new drug vulnerabilities, and to understand the associated co-resistance patterns.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2452-5) contains supplementary material, which is available to authorized users.

Comprehensive Drug Testing of Patient-derived Conditionally Reprogrammed Cells from Castration-resistant Prostate Cancer

BACKGROUND

Technology development to enable the culture of human prostate cancer (PCa) progenitor cells is required for the identification of new, potentially curative therapies for PCa.

OBJECTIVE

We established and characterized patient-derived conditionally reprogrammed cells (CRCs) to assess their biological properties and to apply these to test the efficacies of drugs.

DESIGN, SETTING, AND PARTICIPANTS

CRCs were established from seven patient samples with disease ranging from primary PCa to advanced castration-resistant PCa (CRPC). The CRCs were characterized by genomic, transcriptomic, protein expression, and drug profiling.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The phenotypic quantification of the CRCs was done based on immunostaining followed by image analysis with Advanced Cell Classifier using Random Forest supervised machine learning. Copy number aberrations (CNAs) were called from whole-exome sequencing and transcriptomics using in-house pipelines. Dose-response measurements were used to generate multiparameter drug sensitivity scores using R-statistical language.

RESULTS AND LIMITATIONS

We generated six benign CRC cultures which all had an androgen receptor-negative, basal/transit-amplifying phenotype with few CNAs. In three-dimensional cell culture, these cells could re-express the androgen receptor. The CRCs from a CRPC patient (HUB.5) displayed multiple CNAs, many of which were shared with the parental tumor. We carried out high-throughput drug-response studies with 306 emerging and clinical cancer drugs. Using the benign CRCs as controls, we identified the Bcl-2 family inhibitor navitoclax as the most potent cancer-specific drug for the CRCs from a CRPC patient. Other drug efficacies included taxanes, mepacrine, and retinoids.

CONCLUSIONS

Comprehensive cancer pharmacopeia-wide drug testing of CRCs from a CRPC patient highlighted both known and novel drug sensitivities in PCa, including navitoclax, which is currently being tested in clinical trials of CRPC.

PATIENT SUMMARY

We describe an approach to generate patient-derived cancer cells from advanced prostate cancer and apply such cells to discover drugs that could be applied in clinical trials for castration-resistant prostate cancer.

Abstract 606: Novel somatic mutations in the DNA-binding and coiled-coil domain of the STAT3 gene in LGL-leukemia

Introduction

T-cell large granular lymphocyte (T-LGL) leukemia is a rare, clonal disease characterized by the expansion of CD8+ cytotoxic T-cells. We recently discovered that 40% of T-LGL leukemia patients have somatic mutations in the SH2-domain of the STAT3 gene (Koskela et al. NEJM 2012). As aberrant STAT3 activation can be observed in all patients with LGL-leukemia, we now aimed to discover whether patients without mutations in the STAT3 hotspot area harbor mutations in the other parts of the STAT3 gene.

Methods

Targeted STAT3 sequencing covering all 23 coding exons was done with in-house developed deep amplicon sequencing panel using the Illumina Miseq platform. The data was analyzed with a bioinformatics pipeline, which is based on calling of variants with specific counts/frequencies and filtering out false positives using the estimated error rate and quality data of amplicon reads. All samples with a frequency ratio ≥0.9 were considered to be true mutations after filtering of SNPs and low coverage variants. 111 LGL-leukemia patients with no known STAT3-mutations in the SH2 domain were analyzed.

To explore the functional effects of mutations, expression constructs were generated with the identified variants and wild-type STAT3. The variants were expressed in HEK-293 cells carrying a STAT3-responsive SIE-reporter driven luciferase expression sequence to establish increased basal and IL6-stimulated STAT3 activity.

Results

With targeted amplicon sequencing, 3 patients were discovered to have STAT3 missense mutations in the DNA-binding domain. Two patients presented with the same H410R mutation with a variant allele frequency (VAF) of 49% and 8.8% respectively while another patient had a S381Y mutation (VAF 7%). The mutation H410R occurs in the DNA-binding domain in a highly conserved position, and results in conversion of histidine to arginine, which would predict for a slight increase in hydrophilicity.

In addition to STAT3 DNA-binding domain mutations, one T-LGL patient had a novel F174S mutation in the coiled-coil domain of STAT3 (VAF 43%). The coiled-coil domain of STAT3 has previously been shown to be essential in SH2-domain mediated receptor binding and subsequent activation.

Luciferase measurements of SIE-reporter HEK-293 cells transfected with constructs expressing either wild-type, variant F174S, H410R or Y640F STAT3 (the most common activating mutation in LGL leukemia) revealed the F174S and H410R variants to be as activating as the Y640F mutation in both unstimulated and IL-6 stimulated conditions.

Conclusions

T-LGL leukemia patients without STAT3 SH2-domain mutations harbor novel activating mutations in the DNA-binding and coiled-coil domain of STAT3. The frequency of mutations was 3.6% (4 of 111 patients). These findings further highlight the importance of screening the whole STAT3 gene in the diagnostic workup of LGL-leukemia and the central role of STAT3 in the pathogenesis of the disease.

Citation Format: Emma I. Andersson, Hanna Rajala, Heikki Kuusanmäki, Arjan van Adrichem, Samuli Eldfors, Sonja Lagström, Thomas Olson, Michael Clemente, Pekka Ellonen, Caroline Heckman, Thomas P. Loughran, Jaroslaw P. Maciejewski, Satu Mustjoki. Novel somatic mutations in the DNA-binding and coiled-coil domain of the STAT3 gene in LGL-leukemia. [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 606. doi:10.1158/1538-7445.AM2015-606

Novel TBL1XR1, EPHA7 and SLFN12 mutations in a Sezary syndrome patient discovered by whole exome sequencing

Sezary syndrome (SS) is an aggressive leukaemic variant of cutaneous T-cell lymphoma. Recurrent chromosomal aberrations have been found in SS, but the whole genetic mutation spectrum is unknown. To better understand the molecular pathogenesis of SS, we performed exome sequencing, copy number variation (CNV) and gene expression analysis of primary SS cells. In our index patient with typical SS, we found novel somatic missense mutations in TBL1XR1, EPHA7 and SLFN12 genes in addition to larger chromosomal changes. The mutations are located in biologically relevant genes affecting apoptosis and T-cell maturation. They may play a role in the pathobiology of the disease, but no recurrent mutations were discovered in nine additional patients with SS studied. Thus, screening of larger patient cohorts is needed to confirm their prevalence and biological significance in SS.

Abstract 982: Analysis of clonal evolution of leukemia in vivo following novel targeted treatments

Acute myeloid leukemia (AML) is a genetically heterogeneous disease characterized by significant clonal evolution. It is critical to understand clonal diversity and evolution during cancer progression and drug resistance in order to tailor curative therapies that block the growth of the multiple AML subclones in each patient.

In our individualized systems medicine (ISM) initiative, we performed ex-vivo drug sensitivity and resistance testing (DSRT) with a comprehensive set of 306 cancer drugs on primary cells from 22 AML patients (Pemovska et al, Cancer Discovery, 2013). Objective clinical responses were seen in 3/6 chemorefractory patients treated based on DSRT results. Here, we applied next-generation genome and transcriptome sequencing in order to a) follow clonal progression of adult AML in patients during treatment with novel targeted drugs, b) identify putative cancer predisposing mutations in patients who later develop aggressive relapsed AML.

Serial samples were obtained from each patient during diagnosis, treatment, remission and relapse. The data indicated significant clonal evolution and emergence of new subclones after relapse and drug resistance. In one such case, treatment of an AML patient with a combination of dasatinib-sunitinib-temsirolimus led to the selection of an already existing low-frequency subclone carrying ETV6-NTRK3 fusion. DSRT of the relapsed sample indicated addiction to IGF1R signalling, compatible with the NTRK3-fusion acting as a driver gene for drug resistance after this treatment. Similar trend where a low-frequency subclone was selected for in the resistance sample was seen in 3 other cases analyzed. Thereby, in depth analysis of clonal evolution from paired AML samples should facilitate the design of new combinatorial regimens to block relapse from arising.

Altogether, we analyzed the genomic profile of 20 recurrent, chemorefractory AML cases. The profile was different between the individual patients and showed an overrepresentation of FLT3 and WT1 mutations, whereas previously reported recurrent mutations in primary AML such as DNMT3A, IDH1/2 and RUNX1 mutations were seen only in individual cases.

We also analyzed the germline variants in the 20 cases, of which two had a positive family history. These patients were analyzed to identify putative variants predisposing these patients to refractory AMLs. The finnish population data comprising of exome sequencing data of 3700 individuals was used to filter the germline variants and assess their potential significance. This analysis indicated recurrent germline changes in multidrug resistance superfamily of genes, which suggests potential germline clues to the etiology to the chemorefractory, recurrent AML cases.

Citation Format: Naga Poojitha Ojamies, Mika Kontro, Henrik Edgren, Samuli Eldfors, Pekka Ellonen, Tea Pemovska, Langstrom Sonja, Henrikki Almusa, Maija Lepisto, Tero Aittokallio, Krister Wennerberg, Caroline Heckman, Kimmo Porkka, Olli Kallioniemi. Analysis of clonal evolution of leukemia in vivo following novel targeted treatments. [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 982. doi:10.1158/1538-7445.AM2014-982

Individualized systems medicine strategy to tailor treatments for patients with chemorefractory acute myeloid leukemia

We present an individualized systems medicine (ISM) approach to optimize cancer drug therapies one patient at a time. ISM is based on (i) molecular profiling and ex vivo drug sensitivity and resistance testing (DSRT) of patients' cancer cells to 187 oncology drugs, (ii) clinical implementation of therapies predicted to be effective, and (iii) studying consecutive samples from the treated patients to understand the basis of resistance. Here, application of ISM to 28 samples from patients with acute myeloid leukemia (AML) uncovered five major taxonomic drug-response subtypes based on DSRT profiles, some with distinct genomic features (e.g., MLL gene fusions in subgroup IV and FLT3-ITD mutations in subgroup V). Therapy based on DSRT resulted in several clinical responses. After progression under DSRT-guided therapies, AML cells displayed significant clonal evolution and novel genomic changes potentially explaining resistance, whereas ex vivo DSRT data showed resistance to the clinically applied drugs and new vulnerabilities to previously ineffective drugs.

SIGNIFICANCE

Here, we demonstrate an ISM strategy to optimize safe and effective personalized cancer therapies for individual patients as well as to understand and predict disease evolution and the next line of therapy. This approach could facilitate systematic drug repositioning of approved targeted drugs as well as help to prioritize and de-risk emerging drugs for clinical testing.

Somatic STAT3 mutations in large granular lymphocytic leukemia

BACKGROUND

T-cell large granular lymphocytic leukemia is a rare lymphoproliferative disorder characterized by the expansion of clonal CD3+CD8+ cytotoxic T lymphocytes (CTLs) and often associated with autoimmune disorders and immune-mediated cytopenias.

METHODS

We used next-generation exome sequencing to identify somatic mutations in CTLs from an index patient with large granular lymphocytic leukemia. Targeted resequencing was performed in a well-characterized cohort of 76 patients with this disorder, characterized by clonal T-cell-receptor rearrangements and increased numbers of large granular lymphocytes.

RESULTS

Mutations in the signal transducer and activator of transcription 3 gene (STAT3) were found in 31 of 77 patients (40%) with large granular lymphocytic leukemia. Among these 31 patients, recurrent mutational hot spots included Y640F in 13 (17%), D661V in 7 (9%), D661Y in 7 (9%), and N647I in 3 (4%). All mutations were located in exon 21, encoding the Src homology 2 (SH2) domain, which mediates the dimerization and activation of STAT protein. The amino acid changes resulted in a more hydrophobic protein surface and were associated with phosphorylation of STAT3 and its localization in the nucleus. In vitro functional studies showed that the Y640F and D661V mutations increased the transcriptional activity of STAT3. In the affected patients, downstream target genes of the STAT3 pathway (IFNGR2, BCL2L1, and JAK2) were up-regulated. Patients with STAT3 mutations presented more often with neutropenia and rheumatoid arthritis than did patients without these mutations.

CONCLUSIONS

The SH2 dimerization and activation domain of STAT3 is frequently mutated in patients with large granular lymphocytic leukemia; these findings suggest that aberrant STAT3 signaling underlies the pathogenesis of this disease. (Funded by the Academy of Finland and others.).

Abstract 895: Quantitative drug sensitivity and resistance testing (DSRT) of primary ex vivo AML blasts highlights mTOR and MEK as potential key molecular driver signals of therapeutic significance

Identification of signaling pathways that are required for the growth and differentiation block of cells from adult acute myeloid leukemia (AML) is urgently required to facilitate development of novel therapies. Here, we describe an approach to functionally determine molecular drivers of AML by quantitative drug sensitivity and resistance testing (DSRT) of AML blast cells in primary culture ex vivo. The selection of drugs covered the entire cancer pharmacopeia and much of the pipeline of drugs under development in the industry: 120 FDA approved small molecular cancer drugs and 120 emerging drugs, investigational compounds and signal transduction inhibitors. All compounds were tested over a 10,000-fold concentration range to generate quantitative and reliable dose-response data. In addition, whole exome and transcriptome sequencing and phophoproteomic profiling were also performed to derive a comprehensive understanding of the molecular AML-related aberrations on an individual basis. Comparison of 17 AML patient samples and 3 healthy bone marrow control samples based on ex vivo drug responses identified several classes of approved and investigational drugs that showed selective anti-AML activities: mTOR inhibitors (e.g. temsirolomus, everolimus, sirolimus), MEK inhibitors (e.g. AS703026, GSK1120212, RDEA119, selumetinib), tyrosine kinase inhibitors (e.g. dasatinib, ponatinib, sunitinib), Bcl-2 inhibitors (navitoclax) and HSP90 inhibitors (e.g. BIIB021, NVP-AUY922, tanespimycin). In particular, the rapamycin class of mTOR inhibitors and allosteric MEK inhibitors stood out as effective and selective inhibitors in 8/17 (47%) and 9/17 (52%) of the patients, respectively. Simultaneous data from other targeted inhibitors made it possible to dissect the critical steps in signaling and therapeutic efficacy. For example, PI3K and Akt inhibitors were not effective in these patients, suggesting that the mTOR dependency is mediated through a PI3K-Akt-independent pathway. Similarly, the dependency of MEK signaling appears to be through a Ras-Raf-independent pathway since Raf inhibitors were not effective. In conclusion, the DSRT platform allows us to derive quantitative data on the ex vivo drug response profiles of AML cells from individual patients. This information could be used as a diagnostic tool to optimize personalized therapies in the future. Our data demonstrate that mTOR and MEK signaling and the associated inhibitors are the most promising leads for improved AML therapeutics. This analysis also demonstrates gaps in our current understanding of the redundancy of key cancer cell signaling pathways and proves the significant value of data from experimental drug response testing ex vivo.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 895. doi:1538-7445.AM2012-895

Abstract 5067: Exome sequencing reveals both DNA sequence and copy number changes in AML: Potential driver changes and mechanisms of drug resistance revealed from serial samples from the same patients

Despite significant advances in characterizing the molecular genetics of AML, the clonal evolution of leukemic cells and the dynamic impact of genomic changes on the development of the disease and progression to drug resistance are not well understood. Here, we applied next-generation sequencing to quantify aberrant tumor subclones carrying specific mutant alleles of key cancer genes and developed a method to extract quantitative high-resolution copy number changes across the genome using exome sequencing data from matching cancer and normal DNA. Serial bone marrow (BM) samples collected from diagnosis to relapse to post-treatment drug resistance in a patient-centric manner made it possible to trace the clonal evolution of AML and to identify variants potentially involved in drug resistance. Exome sequencing from AML blast cells and normal skin biopsies was performed as part of the Finnish Hematology Registry and Biobanking (FHRB) effort. Consecutive paired samples from different patients revealed unique genetic patterns of clonal evolution and cancer progression in each patient. In a pre-resistant sample of one AML M5 patient, we identified four closely spaced insertions in the Wilm's Tumor (WT1) suppressor gene, none of which appear on the same sequence reads. This suggests the presence of multiple distinct leukemic subclones even before treatment resistance and underscores the strong selective advantage conferred by WT1 mutations. After relapse, one of the subclones was lost, and another one significantly increased suggesting that the relapse arose from the expansion of a pre-existing resistant subclone. In this patient, recurrent clones otherwise featured similar copy number changes and the same fusion genes as the primary diagnostic sample. In another AML patient developing recurrence an opposite pattern was observed: The relapsed, drug-resistant cells displayed an enormous increase of small microdeletions compared to the diagnostic, pre-treatment sample, while almost all sequence-level alterations in potential cancer genes were the same between the two samples. This suggests that a distinct type of DNA repair deficiency may have contributed to the drug resistant clone in this patient. Conclusions: Exome sequencing from paired samples of AML cells before and after relapse makes it possible to trace the clonal evolution of the disease and study the impact of therapy both at the level of sequence alterations of key cancer genes and simultaneously at the level of copy number changes inferred from exome sequence data. This analysis has highlighted multiple genomic patterns by which resistance may evolve in vivo during cancer treatment. Refined bioinformatic analysis and interpretation of exome-seq data provides a rich resource to identify genetic biomarkers of drug response and minimal residual disease.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5067. doi:1538-7445.AM2012-5067

Abstract 3188: Development of a cancer pharmacopeia-wide ex-vivo drug sensitivity and resistance testing (DSRT) platform for AML: Towards individually optimized therapy and improved understanding of drug resistance patterns

In order to discover unexpected anti-cancer efficacies of approved and emerging drugs, we established a diagnostic ex vivo drug sensitivity and resistance testing (DSRT) platform covering the entire cancer pharmacopeia as well as emerging anti-cancer compounds. Here, the platform was applied to analyze bone marrow (BM) mononuclear cells from 17 adult acute myeloid leukemia (AML) patients, 3 healthy donors as well as 7 AML cell lines. The DSRT panel covered FDA-approved small molecule oncology drugs (n=120), as well as emerging, investigational and pre-clinical oncology compounds (n=120), such as kinase (e.g. RTKs, checkpoint and mitotic kinases, Raf, MEK, JAKs, mTOR, PI3K), and non-kinase inhibitors (e.g. HSP, Bcl, activin, HDAC, PARP, Hh). To generate dose-response curves, each of the drugs was applied over a 10,000-fold concentration range. In addition, the samples underwent deep molecular profiling including exome- and transcriptome sequencing, as well as phosphoproteomic analysis. DSRT provided consistent and reliable data from ex vivo samples with a high correlation between data from individual healthy BM samples (r=0.93). Bioinformatic processing of the data from AML resulted in several key observations. First, overall drug response profiles of AML blast cells were distinctly different from healthy BM controls suggesting several potential leukemia-selective effects, such as multi-kinase (dasatinib), MEK, and mTOR inhibitors. Second, the overall drug responses from AML cell lines and the patient ex vivo samples showed differences, suggesting that ex vivo testing may reveal cancer-selective effects not previously seen in established cancer cell line panels. Third, the response data from patient samples clustered many drugs consistently into the expected functional classes (such as topoisomerase II inhibitors, MEK inhibitors and rapalogs), whereas other drug classes were more dispersed (such as FLT3 inhibitors with quizartinib clustering away from all other tyrosine kinase inhibitors), suggesting secondary targets playing a key role in drug efficacy. Fourth, analysis of serial samples from patients developing clinical resistance to targeted agents showed striking agreement between the ex-vivo DSRT profiles and clinical responses. In conclusion, comprehensive DSRT platform generated powerful novel insights on AML drug response and may enable individual optimization of therapies, particularly for recurrent leukemias. DSRT will also serve as a powerful hypothesis-generator for clinical trials, particularly for emerging drugs. The ability to correlate ex vivo response profiles for hundreds of drugs in clinical samples with deep molecular profiling data will yield exciting new translational and pharmacogenomic opportunities for cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3188. doi:1538-7445.AM2012-3188

Comparison of solution-based exome capture methods for next generation sequencing

Background

Techniques enabling targeted re-sequencing of the protein coding sequences of the human genome on next generation sequencing instruments are of great interest. We conducted a systematic comparison of the solution-based exome capture kits provided by Agilent and Roche NimbleGen. A control DNA sample was captured with all four capture methods and prepared for Illumina GAII sequencing. Sequence data from additional samples prepared with the same protocols were also used in the comparison.

Results

We developed a bioinformatics pipeline for quality control, short read alignment, variant identification and annotation of the sequence data. In our analysis, a larger percentage of the high quality reads from the NimbleGen captures than from the Agilent captures aligned to the capture target regions. High GC content of the target sequence was associated with poor capture success in all exome enrichment methods. Comparison of mean allele balances for heterozygous variants indicated a tendency to have more reference bases than variant bases in the heterozygous variant positions within the target regions in all methods. There was virtually no difference in the genotype concordance compared to genotypes derived from SNP arrays. A minimum of 11× coverage was required to make a heterozygote genotype call with 99% accuracy when compared to common SNPs on genome-wide association arrays.

Conclusions

Libraries captured with NimbleGen kits aligned more accurately to the target regions. The updated NimbleGen kit most efficiently covered the exome with a minimum coverage of 20×, yet none of the kits captured all the Consensus Coding Sequence annotated exons.