A Bayesian framework to study tumor subclone-specific expression by combining bulk DNA and single-cell RNA sequencing data.

Genetic and gene expression heterogeneity is an essential hallmark of many tumors, allowing the cancer to evolve and to develop resistance to treatment. Currently, the most commonly used data types for studying such heterogeneity are bulk tumor/normal whole-genome or whole-exome sequencing (WGS, WES); and single-cell RNA sequencing (scRNA-seq), respectively. However, tools are currently lacking to link genomic tumor subclonality with transcriptomic heterogeneity by integrating genomic and single-cell transcriptomic data collected from the same tumor. To address this gap, we developed scBayes, a Bayesian probabilistic framework that uses tumor subclonal structure inferred from bulk DNA sequencing data to determine the subclonal identity of cells from single-cell gene expression (scRNA-seq) measurements. Grouping together cells representing the same genetically defined tumor subclones allows comparison of gene expression across different subclones, or investigation of gene expression changes within the same subclone across time (i.e., progression, treatment response, or relapse) or space (i.e., at multiple metastatic sites and organs). We used simulated data sets, in silico synthetic data sets, as well as biological data sets generated from cancer samples to extensively characterize and validate the performance of our method, as well as to show improvements over existing methods. We show the validity and utility of our approach by applying it to published data sets and recapitulating the findings, as well as arriving at novel insights into cancer subclonal expression behavior in our own data sets. We further show that our method is applicable to a wide range of single-cell sequencing technologies including single-cell DNA sequencing as well as Smart-seq and 10x Genomics scRNA-seq protocols.

SIRT5 IS A DRUGGABLE METABOLIC VULNERABILITY IN ACUTE MYELOID LEUKEMIA.

We discovered that the survival and growth of many primary acute myeloid leukemia (AML) samples and cell lines, but not normal CD34+ cells, are dependent on SIRT5, a lysine deacylase implicated in regulating multiple metabolic pathways. Dependence on SIRT5 is genotype-agnostic and extends to RAS- and p53-mutated AML. Results were comparable between SIRT5 knockdown and SIRT5 inhibition using NRD167, a potent and selective SIRT5 inhibitor. Apoptosis induced by SIRT5 disruption is preceded by reductions in oxidative phosphorylation and glutamine utilization, and an increase in mitochondrial superoxide that is attenuated by ectopic superoxide dismutase 2. These data indicate that SIRT5 controls and coordinates several key metabolic pathways in AML and implicate SIRT5 as a vulnerability in AML.

JAK2 ex13InDel drives oncogenic transformation and is associated with chronic eosinophilic leukemia and polycythemia vera.

The V617F mutation in the JH2 domain of Janus kinase 2 (JAK2) is an oncogenic driver in several myeloproliferative neoplasms (MPNs), including essential thrombocythemia, myelofibrosis, and polycythemia vera (PV). Other mutations in JAK2 have been identified in MPNs, most notably exon 12 mutations in PV. Here, we describe a novel recurrent mutation characterized by a common 4-amino-acid deletion and variable 1-amino-acid insertion (Leu583-Ala586DelInsSer/Gln/Pro) within the JH2 domain of JAK2. All 4 affected patients had eosinophilia, and both patients with Leu583-Ala586DelInsSer fulfilled diagnostic criteria of both PV and chronic eosinophilic leukemia (CEL). Computational and functional studies revealed that Leu583-Ala586DelInsSer (herein referred to as JAK2ex13InDel) deregulates JAK2 through a mechanism similar to JAK2V617F, activates signal transducer and activator of transcription 5 and extracellular signal-regulated kinase, and transforms parental Ba/F3 cells to growth factor independence. In contrast to JAK2V617F, JAK2ex13InDel does not require an exogenous homodimeric type 1 cytokine receptor to transform Ba/F3 cells and is capable of activating ß common chain family cytokine receptor (interleukin-3 receptor [IL-3R], IL-5R, and granulocyte-macrophage colony stimulating factor receptor) signaling in the absence of ligand, with the maximum effect observed for IL-5R, consistent with the clinical phenotype of eosinophilia. Recognizing this new PV/CEL-overlap MPN has significant clinical implications, as both PV and CEL patients are at high risk for thrombosis, and concomitant cytoreduction of red cells, neutrophils, and eosinophils may be required for prevention of thromboembolic events. Targeted next-generation sequencing for genes recurrently mutated in myeloid malignancies in patients with unexplained eosinophilia may reveal additional cases of Leu583-Ala586DelInsSer/Gln/Pro, allowing for complete characterization of this unique MPN.

The transcriptome of CMML monocytes is highly inflammatory and reflects leukemia-specific and age-related alterations.

Chronic myelomonocytic leukemia (CMML) is an aggressive myeloid neoplasm of older individuals characterized by persistent monocytosis. Somatic mutations in CMML are heterogeneous and only partially explain the variability in clinical outcomes. Recent data suggest that cardiovascular morbidity is increased in CMML and contributes to reduced survival. Clonal hematopoiesis of indeterminate potential (CHIP), the presence of mutated blood cells in hematologically normal individuals, is a precursor of age-related myeloid neoplasms and associated with increased cardiovascular risk. To isolate CMML-specific alterations from those related to aging, we performed RNA sequencing and DNA methylation profiling on purified monocytes from CMML patients and from age-matched (old) and young healthy controls. We found that the transcriptional signature of CMML monocytes is highly proinflammatory, with upregulation of multiple inflammatory pathways, including tumor necrosis factor and interleukin (IL)-6 and -17 signaling, whereas age per se does not significantly contribute to this pattern. We observed no consistent correlations between aberrant gene expression and CpG island methylation, suggesting that proinflammatory signaling in CMML monocytes is governed by multiple and complex regulatory mechanisms. We propose that proinflammatory monocytes contribute to cardiovascular morbidity in CMML patients and promote progression by selection of mutated cell clones. Our data raise questions of whether asymptomatic patients with CMML benefit from monocyte-depleting or anti-inflammatory therapies.

Identification of lenalidomide resistance pathways in myeloma and targeted resensitization using cereblon replacement, inhibition of STAT3 or targeting of IRF4.

To understand immunomodulatory drug (IMiD) resistance in multiple myeloma (MM), we created isogenic human multiple myeloma cell lines (HMCLs) sensitive and resistant to lenalidomide, respectively. Four HMCLs were demonstrated to be resistant to all IMiDs including lenalidomide, pomalidomide, and CC-220, but not to Bortezomib. In three HMLCs (MM.1.SLenRes, KMS11LenRes and OPM2LenRes), CRBN abnormalities were found, including chromosomal deletion, point mutation, and low CRBN expression. The remaining HMCL, XG1LenRes, showed no changes in CRBN but exhibited CD147 upregulation and impaired IRF4 downregulation after lenalidomide treatment. Depletion of CD147 in XG1LenRes and three additional HMCLs had no significant impact on MM viability and lenalidomide response. Further analysis of XG1LenRes demonstrated increased IL6 expression and constitutive STAT3 activation. Inhibition of STAT3 with a selective compound (PB-1-102) re-sensitized XG1LenRes to lenalidomide. Since XG1LenRes harbors a truncated IRF4 that is not downregulated by lenalidomide, we targeted IRF4/MYC axis with a selective inhibitor of the bromodomain of CBP/EP300 (SGC-CBP30), which restored lenalidomide response in XG1LenRes. This strategy also appeared to be more broadly applicable as SGC-CBP30 could re-sensitize two resistant HMCLs with low but detectable CRBN expression to lenalidomide, suggesting that targeting CBP/E300 is a promising approach to restore IMiD sensitivity in MM with detectable CRBN expression.

Nuclear-Cytoplasmic Transport Is a Therapeutic Target in Myelofibrosis.

PURPOSE: Myelofibrosis is a hematopoietic stem cell neoplasm characterized by bone marrow reticulin fibrosis, extramedullary hematopoiesis, and frequent transformation to acute myeloid leukemia. Constitutive activation of JAK/STAT signaling through mutations in JAK2, CALR, or MPL is central to myelofibrosis pathogenesis. JAK inhibitors such as ruxolitinib reduce symptoms and improve quality of life, but are not curative and do not prevent leukemic transformation, defining a need to identify better therapeutic targets in myelofibrosis. EXPERIMENTAL DESIGN: A short hairpin RNA library screening was performed on JAK2V617F-mutant HEL cells. Nuclear-cytoplasmic transport (NCT) genes including RAN and RANBP2 were among top candidates. JAK2V617F-mutant cell lines, human primary myelofibrosis CD34+ cells, and a retroviral JAK2V617F-driven myeloproliferative neoplasms mouse model were used to determine the effects of inhibiting NCT with selective inhibitors of nuclear export compounds KPT-330 (selinexor) or KPT-8602 (eltanexor). RESULTS: JAK2V617F-mutant HEL, SET-2, and HEL cells resistant to JAK inhibition are exquisitely sensitive to RAN knockdown or pharmacologic inhibition by KPT-330 or KPT-8602. Inhibition of NCT selectively decreased viable cells and colony formation by myelofibrosis compared with cord blood CD34+ cells and enhanced ruxolitinib-mediated growth inhibition and apoptosis, both in newly diagnosed and ruxolitinib-exposed myelofibrosis cells. Inhibition of NCT in myelofibrosis CD34+ cells led to nuclear accumulation of p53. KPT-330 in combination with ruxolitinib-normalized white blood cells, hematocrit, spleen size, and architecture, and selectively reduced JAK2V617F-mutant cells in vivo. CONCLUSIONS: Our data implicate NCT as a potential therapeutic target in myelofibrosis and provide a rationale for clinical evaluation in ruxolitinib-exposed patients with myelofibrosis.

Loss of FAM46C Promotes Cell Survival in Myeloma.

FAM46C is one of the most recurrently mutated genes in multiple myeloma; however its role in disease pathogenesis has not been determined. Here we demonstrate that wild-type (WT) FAM46C overexpression induces substantial cytotoxicity in multiple myeloma cells. In contrast, FAM46C mutations found in multiple myeloma patients abrogate this cytotoxicity, indicating a survival advantage conferred by the FAM46C mutant phenotype. WT FAM46C overexpression downregulated IRF4, CEBPB, and MYC and upregulated immunoglobulin (Ig) light chain and HSPA5/BIP Furthermore, pathway analysis suggests that enforced FAM46C expression activated the unfolded protein response pathway and induced mitochondrial dysfunction. CRISPR-mediated depletion of endogenous FAM46C enhanced multiple myeloma cell growth, decreased Ig light chain and HSPA5/BIP expression, activated ERK and antiapoptotic signaling, and conferred relative resistance to dexamethasone and lenalidomide treatments. Genes altered in FAM46C-depleted cells were enriched for signaling pathways regulating estrogen, glucocorticoid, B-cell receptor signaling, and ATM signaling. Together these results implicate FAM46C in myeloma cell growth and survival and identify FAM46C mutation as a contributor to myeloma pathogenesis and disease progression via perturbation in plasma cell differentiation and endoplasmic reticulum homeostasis. Cancer Res; 77(16); 4317-27. ©2017 AACR.