title: Inactivation of Eed impedes MLL-AF9-mediated leukemogenesis through Cdkn2a-dependent and Cdkn2a-independent mechanisms in a murine model.
abstract: Polycomb repressive complex 2 (PRC2) is a chromatin regulator with central roles in development and cancer. The canonical function of PRC2 is the trimethylation of histone 3 on lysine residue 27. This epigenetic modification is associated with gene silencing. Both tumor suppressor and oncogenic functions have been reported for PRC2, depending on cellular context. In leukemia mediated by the leukemogenic fusion MLL-AF9, complete ablation of canonical PRC2 function by genetic inactivation of the core component embryonic ectoderm development (Eed) or by combined pharmacologic inhibition of the PRC2 methyltransferases EZH2 and EZH1 has a strong anti-leukemic effect, and this effect has been linked to de-repression of the PRC2 target locus Cdkn2a. We asked whether inactivation of Cdkn2a is sufficient to restore leukemic activity of Eed-inactivated MLL-AF9 leukemia cells, using combined genetic inactivation of Cdkn2a and Eed. We found that Cdkn2a inactivation partially rescues in vitro and in vivo growth of Eed-inactivated MLL-AF9 cells. However, the growth of Eed-null Cdkn2a-null MLL-AF9 cells in the absence of Cdkn2a remained severely compromised in vitro and in vivo, compared with that of their Eed-floxed Cdkn2a-null counterparts. RNA sequencing analysis revealed that several genes previously implicated in inefficient growth of MLL-AF9-transformed cells, including Gata2, Egr1, and Cdkn2b were de-repressed as a consequence of Eed inactivation. Furthermore, we found that direct binding targets of MLL fusion proteins are negatively enriched in Eed-inactivated Cdkn2a-null MLL-AF9-transformed cells. Our data indicate that interference with PRC2 function affects MLL-AF9-mediated leukemogenesis by both Cdkn2a-dependent and Cdkn2a-independent mechanisms.
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Etienne
authors.initials: E
authors.lastname: Danis
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Taylor
authors.initials: T
authors.lastname: Yamauchi
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Kristen
authors.initials: K
authors.lastname: Echanique
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Haladyna
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Roshni
authors.initials: R
authors.lastname: Kalkur
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Simone
authors.initials: S
authors.lastname: Riedel
authors.affiliation: Human Oncology and Pathogenesis Program, and Leukemia Service, Department of Medicine; Memorial Sloan-Kettering Cancer Center, Zuckerman Research Center, 417 East 68th Street New York, NY 10065New York, NY 10065, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhu
authors.affiliation: Dana Farber Cancer Institute and Boston Children's Hospital, Harvard Medical School and HHMI, 450 Brookline Avenue, Boston, MA 02215, USA.
authors.forename: Huafeng
authors.initials: H
authors.lastname: Xie
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Kathrin M
authors.initials: KM
authors.lastname: Bernt
authors.affiliation: Dana Farber Cancer Institute and Boston Children's Hospital, Harvard Medical School and HHMI, 450 Brookline Avenue, Boston, MA 02215, USA.
authors.forename: Stuart H
authors.initials: SH
authors.lastname: Orkin
authors.affiliation: Human Oncology and Pathogenesis Program, and Leukemia Service, Department of Medicine; Memorial Sloan-Kettering Cancer Center, Zuckerman Research Center, 417 East 68th Street New York, NY 10065New York, NY 10065, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Armstrong
authors.affiliation: Center for Cancer and Blood Disorders, Children's Hospital Colorado, and Department of Pediatrics, Section of Pediatric Hematology/Oncology/Bone Marrow Transplantation, University of Colorado Denver, 13123 East 16th Avenue, Aurora, CO 80045, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Neff
mesh_terms: D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D007938:Leukemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D009374:Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D063151:Polycomb Repressive Complex 2 / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: C417743:Cdkn2a protein, mouse; D019941:Cyclin-Dependent Kinase Inhibitor p16; C107275:Eed protein, mouse; C551356:MLL-AF9 fusion protein, mouse; D015514:Oncogene Proteins, Fusion; D063151:Polycomb Repressive Complex 2