Multiple myeloma-associated chromosomal translocation activates orphan snoRNA ACA11 to suppress oxidative stress

10.1172/JCI63051Journal of Clinical Investigation12282793-2806JCIN

Mcl1 haploinsufficiency protects mice from Myc-induced acute myeloid leukemia

Antiapoptotic BCL2 family members have been implicated in the pathogenesis of acute myelogenous leukemia (AML), but the functional significance and relative importance of individual proteins (e.g., BCL2, BCL-XL, and myeloid cell leukemia 1 [MCL1]) remain poorly understood. Here, we examined the expression of BCL2, BCL-XL, and MCL1 in primary human hematopoietic subsets and leukemic blasts from AML patients and found that MCL1 transcripts were consistently expressed at high levels in all samples tested. Consistent with this, Mcl1 protein was also highly expressed in myeloid leukemic blasts in a mouse Myc-induced model of AML. We used this model to test the hypothesis that Mcl1 facilitates AML development by allowing myeloid progenitor cells to evade Myc-induced cell death. Indeed, activation of Myc for 7 days in vivo substantially increased myeloid lineage cell numbers, whereas hematopoietic stem, progenitor, and B-lineage cells were depleted. Furthermore, Mcl1 haploinsufficiency abrogated AML development. In addition, deletion of a single allele of Mcl1 from fully transformed AML cells substantially prolonged the survival of transplanted mice. Conversely, the rapid lethality of disease was restored by coexpression of Bcl2 and Myc in Mcl1-haploinsufficient cells. Together, these data demonstrate a critical and dose-dependent role for Mcl1 in AML pathogenesis in mice and suggest that MCL1 may be a promising therapeutic target in patients with de novo AML

SciClone: Inferring clonal architecture and tracking the spatial and temporal patterns of tumor evolution

The sensitivity of massively-parallel sequencing has confirmed that most cancers are oligoclonal, with subpopulations of neoplastic cells harboring distinct mutations. A fine resolution view of this clonal architecture provides insight into tumor heterogeneity, evolution, and treatment response, all of which may have clinical implications. Single tumor analysis already contributes to understanding these phenomena. However, cryptic subclones are frequently revealed by additional patient samples (e.g., collected at relapse or following treatment), indicating that accurately characterizing a tumor requires analyzing multiple samples from the same patient. To address this need, we present SciClone, a computational method that identifies the number and genetic composition of subclones by analyzing the variant allele frequencies of somatic mutations. We use it to detect subclones in acute myeloid leukemia and breast cancer samples that, though present at disease onset, are not evident from a single primary tumor sample. By doing so, we can track tumor evolution and identify the spatial origins of cells resisting therapy

Very Late Antigen-4 (α<inf>4</inf>β<inf>1</inf> Integrin) Targeted PET Imaging of Multiple Myeloma

Biomedical imaging techniques such as skeletal survey and 18F-fluorodeoxyglucose (FDG)/Positron Emission Tomography (PET) are frequently used to diagnose and stage multiple myeloma (MM) patients. However, skeletal survey has limited sensitivity as it can detect osteolytic lesions only after 30-50% cortical bone destruction, and FDG is a marker of cell metabolism that has limited sensitivity for intramedullary lesions in MM. Targeted, and non-invasive novel probes are needed to sensitively and selectively image the unique molecular signatures and cellular processes associated with MM. Very late antigen-4 (VLA-4; also called α4β1 integrin) is over-expressed on MM cells, and is one of the key mediators of myeloma cell adhesion to the bone marrow (BM) that promotes MM cell trafficking and drug resistance. Here we describe a proof-of-principle, novel molecular imaging strategy for MM tumors using a VLA-4 targeted PET radiopharmaceutical, 64Cu-CB-TE1A1P-LLP2A. Cell uptake studies in a VLA-4-positive murine MM cell line, 5TGM1, demonstrated receptor specific uptake (P<0.0001, block vs. non-block). Tissue biodistribution at 2 h of 64Cu-CB-TE1A1P-LLP2A in 5TGM1 tumor bearing syngeneic KaLwRij mice demonstrated high radiotracer uptake in the tumor (12±4.5%ID/g), and in the VLA-4 rich organs, spleen (8.8±1.0%ID/g) and marrow (11.6±2.0%ID/g). Small animal PET/CT imaging with 64Cu-CB-TE1A1P-LLP2A demonstrated high uptake in the 5TGM1 tumors (SUV 6.6±1.1). There was a 3-fold reduction in the in vivo tumor uptake in the presence of blocking agent (2.3±0.4). Additionally, 64Cu-CB-TE1A1P-LLP2A demonstrated high binding to the human MM cell line RPMI-8226 that was significantly reduced in the presence of the cold targeting agent. These results provide pre-clinical evidence that VLA-4-targeted imaging using 64Cu-CB-TE1A1P-LLP2A is a novel approach to imaging MM tumors. © 2013 Soodgupta et al

The Origin and Evolution of Mutations in Acute Myeloid Leukemia

SummaryMost mutations in cancer genomes are thought to be acquired after the initiating event, which may cause genomic instability and drive clonal evolution. However, for acute myeloid leukemia (AML), normal karyotypes are common, and genomic instability is unusual. To better understand clonal evolution in AML, we sequenced the genomes of M3-AML samples with a known initiating event (PML-RARA) versus the genomes of normal karyotype M1-AML samples and the exomes of hematopoietic stem/progenitor cells (HSPCs) from healthy people. Collectively, the data suggest that most of the mutations found in AML genomes are actually random events that occurred in HSPCs before they acquired the initiating mutation; the mutational history of that cell is “captured” as the clone expands. In many cases, only one or two additional, cooperating mutations are needed to generate the malignant founding clone. Cells from the founding clone can acquire additional cooperating mutations, yielding subclones that can contribute to disease progression and/or relapse

The creatine kinase pathway is a metabolic vulnerability in EVI1-positive acute myeloid leukemia

Expression of the MECOM (also known as EVI1) proto-oncogene is deregulated by chromosomal translocations in some cases of acute myeloid leukemia (AML) and is associated with poor clinical outcome. Here, through transcriptomic and metabolomic profiling of hematopoietic cells, we reveal that EVI1 overexpression alters cellular metabolism. A screen using pooled short hairpin RNAs (shRNAs) identified the ATP-buffering, mitochondrial creatine kinase CKMT1 as necessary for survival of EVI1-expressing cells in subjects with EVI1-positive AML. EVI1 promotes CKMT1 expression by repressing the myeloid differentiation regulator RUNX1. Suppression of arginine-creatine metabolism by CKMT1-directed shRNAs or by the small molecule cyclocreatine selectively decreased the viability, promoted the cell cycle arrest and apoptosis of human EVI1-positive cell lines, and prolonged survival in both orthotopic xenograft models and mouse models of primary AML. CKMT1 inhibition altered mitochondrial respiration and ATP production, an effect that was abrogated by phosphocreatine-mediated reactivation of the arginine-creatine pathway. Targeting CKMT1 is thus a promising therapeutic strategy for this EVI1-driven AML subtype that is highly resistant to current treatment regimens. Keywords: AML; RUNX1; CKMT1; cyclocreatine; arginine metabolismNational Cancer Institute (U.S.) (NIH 1R35 CA210030-01)Stand Up To CancerBridge ProjectNational Cancer Institute (U.S.) (David H. Koch Institute for Integrative Cancer Research at MIT. Grant P30-CA14051

Antagonizing Integrin β3 Increases Immunosuppression in Cancer

Integrin β3 is critical for tumor invasion, neoangiogenesis, and inflammation, making it a promising cancer target. However, preclinical and clinical data of integrin β3 antagonists have demonstrated no benefit or worse outcomes. We hypothesized that integrin β3 could affect tumor immunity and evaluated tumors in mice with deletion of integrin β3 in macrophage lineage cells (β3KOM). β3KOM mice had increased melanoma and breast cancer growth with increased tumor-promoting M2 macrophages and decreased CD8+ T cells. Integrin β3 antagonist, cilengitide, also enhanced tumor growth and increased M2 function. We uncovered a negative feedback loop in M2 myeloid cells, wherein integrin β3 signaling favored STAT1 activation, an M1-polarizing signal, and suppressed M2-polarizing STAT6 activation. Finally, disruption of CD8+ T cells, macrophages, or macrophage integrin β3 signaling blocked the tumor-promoting effects of integrin β3 antagonism. These results suggest that effects of integrin β3 therapies on immune cells should be considered to improve outcomes. Cancer Res; 76(12); 3484–95. ©2016 AACR