Manabu Soda

Leukemic evolution of donor-derived cells harboring IDH2 and DNMT3A mutations after allogeneic stem cell transplantation.

Leukemic evolution of donor-derived cells harboring IDH2 and DNMT3A mutations after allogeneic stem cell transplantation

Genomic characterization of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare malignancy confined to the central nervous system (CNS), and majority of PCNSL is pathologically classified as diffuse large B-cell lymphoma (DLBCL). We have now performed whole-exome sequencing for 41 tumor tissues of DLBCL-type PCNSL and paired normal specimens and also RNA-sequencing for 30 tumors, revealing a very high frequency of nonsynonymous somatic mutations in PIM1 (100xa0%), BTG2 (92.7xa0%), and MYD88 (85.4xa0%). Many genes in the NF-κB pathway are concurrently mutated within the same tumors. Further, focal deletion or somatic mutations in the HLA genes are associated with poor prognosis. Copy number amplification and overexpression of genes at chromosome 7q35 were both found to predict short progression-free survival as well. Oncogenic mutations in GRB2 were also detected, the effects of which in cultured cells were attenuated by inhibitors of the downstream kinases MAP2K1 and MAP2K2. Individuals with tumors positive for MYD88 mutations also harbored the same mutations at a low frequency in peripheral blood mononuclear cells, suggesting that MYD88 mutation-positive precancerous cells originate outside of the CNS and develop into lymphoma after additional genetic hits that confer adaptation to the CNS environment.

Epigenetic regulation of the nuclear-coded GCAT and SHMT2 genes confers human age-associated mitochondrial respiration defects

Age-associated accumulation of somatic mutations in mitochondrial DNA (mtDNA) has been proposed to be responsible for the age-associated mitochondrial respiration defects found in elderly human subjects. We carried out reprogramming of human fibroblast lines derived from elderly subjects by generating their induced pluripotent stem cells (iPSCs), and examined another possibility, namely that these aging phenotypes are controlled not by mutations but by epigenetic regulation. Here, we show that reprogramming of elderly fibroblasts restores age-associated mitochondrial respiration defects, indicating that these aging phenotypes are reversible and are similar to differentiation phenotypes in that both are controlled by epigenetic regulation, not by mutations in either the nuclear or the mitochondrial genome. Microarray screening revealed that epigenetic downregulation of the nuclear-coded GCAT gene, which is involved in glycine production in mitochondria, is partly responsible for these aging phenotypes. Treatment of elderly fibroblasts with glycine effectively prevented the expression of these aging phenotypes.

Integrative analysis of genomic alterations in triple-negative breast cancer in association with homologous recombination deficiency

Triple-negative breast cancer (TNBC) cells do not express estrogen receptors, progesterone receptors, or human epidermal growth factor receptor 2. Currently, apart from poly ADP-ribose polymerase inhibitors, there are few effective therapeutic options for this type of cancer. Here, we present comprehensive characterization of the genetic alterations in TNBC performed by high coverage whole genome sequencing together with transcriptome and whole exome sequencing. Silencing of the BRCA1 gene impaired the homologous recombination pathway in a subset of TNBCs, which exhibited similar phenotypes to tumors with BRCA1 mutations; they harbored many structural variations (SVs) with relative enrichment for tandem duplication. Clonal analysis suggested that TP53 mutations and methylation of CpG dinucleotides in the BRCA1 promoter were early events of carcinogenesis. SVs were associated with driver oncogenic events such as amplification of MYC, NOTCH2, or NOTCH3 and affected tumor suppressor genes including RB1, PTEN, and KMT2C. Furthermore, we identified putative TGFA enhancer regions. Recurrent SVs that affected the TGFA enhancer region led to enhanced expression of the TGFA oncogene that encodes one of the high affinity ligands for epidermal growth factor receptor. We also identified a variety of oncogenes that could transform 3T3 mouse fibroblasts, suggesting that individual TNBC tumors may undergo a unique driver event that can be targetable. Thus, we revealed several features of TNBC with clinically important implications.

Transforming somatic mutations of mammalian target of rapamycin kinase in human cancer

Mammalian target of rapamycin (mTOR) is a serine–threonine kinase that acts downstream of the phosphatidylinositol 3‐kinase signaling pathway and regulates a wide range of cellular functions including transcription, translation, proliferation, apoptosis, and autophagy. Whereas genetic alterations that result in mTOR activation are frequently present in human cancers, whether the mTOR gene itself becomes an oncogene through somatic mutation has remained unclear. We have now identified a somatic non‐synonymous mutation of mTOR that results in a leucine‐to‐valine substitution at amino acid position 2209 in a specimen of large cell neuroendocrine carcinoma. The mTOR(L2209V) mutant manifested marked transforming potential in a focus formation assay with mouse 3T3 fibroblasts, and it induced the phosphorylation of p70 S6 kinase, S6 ribosomal protein, and eukaryotic translation initiation factor 4E–binding protein 1 in these cells. Examination of additional tumor specimens as well as public and in‐house databases of cancer genome mutations identified another 28 independent non‐synonymous mutations of mTOR in various cancer types, with 12 of these mutations also showing transforming ability. Most of these oncogenic mutations cluster at the interface between the kinase domain and the FAT (FRAP, ATM, TRRAP) domain in the 3‐D structure of mTOR. Transforming mTOR mutants were also found to promote 3T3 cell survival, and their oncogenic activity was sensitive to rapamycin. Our data thus show that mTOR acquires transforming activity through genetic changes in cancer, and they suggest that such tumors may be candidates for molecularly targeted therapy with mTOR inhibitors.

Oncogenic activity of BIRC2 and BIRC3 mutants independent of nuclear factor-κB-activating potential.

BIRC2 and BIRC3 are closely related members of the inhibitor of apoptosis (IAP) family of proteins and play pivotal roles in regulation of nuclear factor‐κB (NF‐κB) signaling and apoptosis. Copy number loss for and somatic mutation of BIRC2 and BIRC3 have been frequently detected in lymphoid malignancies, with such genetic alterations being thought to contribute to carcinogenesis through activation of the noncanonical NF‐κB signaling pathway. Here we show that BIRC2 and BIRC3 mutations are also present in a wide range of epithelial tumors and that most such nonsense or frameshift mutations confer direct transforming potential. This oncogenic function of BIRC2/3 mutants is largely independent of their ability to activate NF‐κB signaling. Rather, all of the transforming mutants lack an intact RING finger domain, with loss of ubiquitin ligase activity being essential for transformation irrespective of NF‐κB regulation. The serine‐threonine kinase NIK was found to be an important, but not exclusive, mediator of BIRC2/3‐driven carcinogenesis, although this function was independent of NF‐κB activation. Our data thus suggest that, in addition to the BIRC2/3–NIK–NF‐κB signaling pathway, BIRC2/3–NIK signaling targets effectors other than NF‐κB and thereby contributes directly to carcinogenesis. Identification of these effectors may provide a basis for the development of targeted agents for the treatment of lymphoid malignancies and other cancers with BIRC2/3 alterations.

Pancreatic tumor microenvironment confers highly malignant properties on pancreatic cancer cells

Tumor microenvironment plays a pivotal role in cancer progression; however, little is known regarding how differences in the microenvironment affect characteristics of cancer cells. Here, we investigated the effects of tumor microenvironment on cancer cells by using mouse tumor models. After three cycles of inoculation and extraction of human pancreatic cancer cells, including SUIT-2 and Panc-1 cells, from tumors, distinct cancer cell lines were established: 3P cells from the pancreas obtained using the orthotopic tumor model and 3sc cells from subcutaneous tissue obtained using the subcutaneous tumor model. On re-inoculation of these cells, the 3sc cells and, more prominently, the 3P cells, exhibited higher tumorigenic activity than the parental cells. The 3P cells specifically exhibited low E-cadherin expression and high invasiveness, suggesting that they were endowed with the highest malignant characteristics. RNA-sequence analysis demonstrated that distinct signaling pathways were activated in each cell line and that the 3P cells acquired a cancer stem cell-like phenotype. Among cancer stem cell-related genes, those specifically expressed in the 3P cells, including NES, may be potential new targets for cancer therapy. The mechanisms underlying the development of highly malignant cancer cell lines were investigated. Individual cell clones within the parental cells varied in tumor-forming ability, indicating the presence of cellular heterogeneity. Moreover, the tumor-forming ability and the gene expression profile of each cell clone were altered after serial orthotopic inoculations. The present study thus suggests that both selection and education processes by tumor microenvironment are involved in the development of highly malignant cancer cells.

Mutational Landscape and Antiproliferative Functions of ELF Transcription Factors in Human Cancer

ELF4 (also known as MEF) is a member of the ETS family of transcription factors. An oncogenic role for ELF4 has been demonstrated in hematopoietic malignancies, but its function in epithelial tumors remains unclear. Here, we show that ELF4 can function as a tumor suppressor and is somatically inactivated in a wide range of human tumors. We identified a missense mutation affecting the transactivation potential of ELF4 in oral squamous cell carcinoma cells. Restoration of the transactivation activity through introduction of wild-type ELF4 significantly inhibited cell proliferation in vitro and tumor xenograft growth. Furthermore, we found that ELF1 and ELF2, closely related transcription factors to ELF4, also exerted antiproliferative effects in multiple cancer cell lines. Mutations in ELF1 and ELF2, as in ELF4, were widespread across human cancers, but were almost all mutually exclusive. Moreover, chromatin immunoprecipitation coupled with high-throughput sequencing revealed ELF4-binding sites in genomic regions adjacent to genes related to cell-cycle regulation and apoptosis. Finally, we provide mechanistic evidence that the antiproliferative effects of ELF4 were mediated through the induction of HRK, an activator of apoptosis, and DLX3, an inhibitor of cell growth. Collectively, our findings reveal a novel subtype of human cancer characterized by inactivating mutations in the ELF subfamily of proteins, and warrant further investigation of the specific settings where ELF restoration may be therapeutically beneficial. Cancer Res; 76(7); 1814-24. ©2016 AACR.

Secondary EML4–ALK-positive Lung Adenocarcinoma in a Patient Previously Treated for Acute Lymphoblastic Leukemia in Childhood: A Case Report

It is widely recognized that the risk of secondary neoplasms increases as childhood cancer survivors progress through adulthood. These are mainly hematological malignancies, and recurrent chromosome translocations are commonly detected in such cases. On the other hand, while secondary epithelial malignancies have sometimes been reported, chromosome translocations in these epithelial malignancies have not. A 33-year-old man who had been diagnosed with acute lymphoblastic leukemia and treated with chemotherapy almost 20 years earlier was diagnosed with lung adenocarcinoma. After chromosomal rearrangement of echinoderm microtubule-associated protein-like 4 gene and the anaplastic lymphoma kinase gene was detected in this adenocarcinoma, he responded to treatment with crizotinib. It was therefore concluded that this echinoderm microtubule-associated protein-like 4 gene-anaplastic lymphoma kinase gene-positive lung adenocarcinoma was a secondary epithelial malignancy.

Identification of a novel fusion gene HMGA2-EGFR in glioblastoma: HMGA2-EGFR in glioblastoma progression

Glioblastoma is one of the most malignant forms of cancer, for which no effective targeted therapy has been found. Although The Cancer Genome Atlas has provided a list of fusion genes in glioblastoma, their role in progression of glioblastoma remains largely unknown. To search for novel fusion genes, we obtained RNA‐seq data from TGS‐01 human glioma‐initiating cells, and identified a novel fusion gene (HMGA2‐EGFR), encoding a protein comprising the N‐terminal region of the high‐mobility group AT‐hook protein 2 (HMGA2) fused to the C‐terminal region of epidermal growth factor receptor (EGFR), which retained the transmembrane and kinase domains of the EGFR. This fusion gene product showed transforming potential and a high tumor‐forming capacity in cell culture and in vivo. Mechanistically, HMGA2‐EGFR constitutively induced a higher level of phosphorylated STAT5B than EGFRvIII, an in‐frame exon deletion product of the EGFR gene that is commonly found in primary glioblastoma. Forced expression of HMGA2‐EGFR enhanced orthotopic tumor formation of the U87MG human glioma cell line. Furthermore, the EGFR kinase inhibitor erlotinib blocked sphere formation of TGS‐01 cells in culture and inhibited tumor formation in vivo. These findings suggest that, in addition to gene amplification and in‐frame exon deletion, EGFR signaling can also be activated by gene fusion, suggesting a possible avenue for treatment of glioblastoma.