pyrimidinones and Rhabdomyosarcoma

The RAS isoforms are frequently mutated in many types of human cancers, including PAX3/PAX7 fusion-negative rhabdomyosarcoma. Pediatric RMS arises from skeletal muscle progenitor cells that have failed to differentiate normally. The role of mutant RAS in this differentiation blockade is incompletely understood. We demonstrate that oncogenic RAS, acting through the RAF-MEK [mitogen-activated protein kinase (MAPK) kinase]-ERK (extracellular signal-regulated kinase) MAPK effector pathway, inhibits myogenic differentiation in rhabdomyosarcoma by repressing the expression of the prodifferentiation myogenic transcription factor, MYOG. This repression is mediated by ERK2-dependent promoter-proximal stalling of RNA polymerase II at the

Topics: Animals; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Cell Survival; Chromatin; Enhancer Elements, Genetic; Extracellular Signal-Regulated MAP Kinases; Genes, ras; Humans; MAP Kinase Signaling System; Mice; Mitogen-Activated Protein Kinase Kinases; Muscle Development; Myoblasts; Myogenin; Oncogene Proteins, Fusion; Protein Kinase Inhibitors; Pyridones; Pyrimidinones; Receptor, IGF Type 1; Rhabdomyosarcoma; Transcription, Genetic; Xenograft Model Antitumor Assays

Paediatric solid tumours arise from endodermal, ectodermal, or mesodermal lineages. Although the overall survival of children with solid tumours is 75%, that of children with recurrent disease is below 30%. To capture the complexity and diversity of paediatric solid tumours and establish new models of recurrent disease, here we develop a protocol to produce orthotopic patient-derived xenografts at diagnosis, recurrence, and autopsy. Tumour specimens were received from 168 patients, and 67 orthotopic patient-derived xenografts were established for 12 types of cancer. The origins of the patient-derived xenograft tumours were reflected in their gene-expression profiles and epigenomes. Genomic profiling of the tumours, including detailed clonal analysis, was performed to determine whether the clonal population in the xenograft recapitulated the patient's tumour. We identified several drug vulnerabilities and showed that the combination of a WEE1 inhibitor (AZD1775), irinotecan, and vincristine can lead to complete response in multiple rhabdomyosarcoma orthotopic patient-derived xenografts tumours in vivo.

Topics: Animals; Bortezomib; Camptothecin; Cell Cycle Proteins; Child; Clone Cells; Drug Therapy, Combination; Epigenesis, Genetic; Female; Heterografts; High-Throughput Screening Assays; Humans; Hydroxamic Acids; Indoles; Irinotecan; Mice; Neoplasms; Nuclear Proteins; Panobinostat; Protein-Tyrosine Kinases; Pyrazoles; Pyrimidines; Pyrimidinones; Rhabdomyosarcoma; Vincristine; Xenograft Model Antitumor Assays

Musculoskeletal sarcomas are aggressive malignancies of bone and soft tissues often affecting children and adolescents. Histone deacetylase inhibitors (HDACi) have been proposed to counteract cancer stem cells (CSCs) in solid neoplasms. When tested in human osteosarcoma, rhabdomyosarcoma, and Ewing's sarcoma stem cells, the new HDACi MC1742 (1) and MC2625 (2) increased acetyl-H3 and acetyl-tubulin levels and inhibited CSC growth by apoptosis induction. At nontoxic doses, 1 promoted osteogenic differentiation. Further investigation with 1 will be done in preclinical sarcoma models.

Topics: Aminopyridines; Apoptosis; Bone Neoplasms; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Drug Screening Assays, Antitumor; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Neoplastic Stem Cells; Osteogenesis; Osteosarcoma; Pyrimidinones; Rhabdomyosarcoma; Sarcoma; Sarcoma, Ewing; Structure-Activity Relationship

Paediatric solid tumours exhibit steep dose-response curves to alkylating agents and are therefore considered candidates for high-dose chemotherapy and autologous stem cell support. There is growing evidence that autologous stem cell grafts from patients with solid tumours are frequently contaminated with live tumour cells. The objective of this study was to perform, in a preclinical purging model, an initial assessment of the safety and efficacy of a two-step purging procedure that combined Merocyanine 540-mediated photodynamic therapy (MC540-PDT) with a brief exposure to the alkyl-lysophospholipid, Edelfosine. Human and murine bone marrow cells and Neuro-2a murine neuroblastoma, SK-N-SH human neuroblastoma, SK-ES-1 and U-2 OS human osteosarcoma, G-401 and SK-NEP-1 human Wilms' tumour, and A-204 human rhabdomyosarcoma cells were exposed to a fixed dose of MC540-PDT followed by a brief incubation with graded concentrations of Edelfosine. Survival was subsequently assessed by in vitro clonal assay or, in the case of CD34-positive haematopoietic stem cells, by an immunohistochemical method. Combination purging with MC540-PDT and Edelfosine depleted all tumour cells by >4 log while preserving at least 15% of murine granulocyte/macrophage progenitors (CFU-GM), 34% of human CFU-GM, and 31% of human CD34-positive cells. The data suggest that combination purging with MC540-PDT and Edelfosine may be useful for the ex vivo purging of autologous stem cell grafts from patients with paediatric solid tumours.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Survival; Dose-Response Relationship, Drug; Hematopoietic Stem Cell Transplantation; Humans; Mice; Neuroblastoma; Osteosarcoma; Phospholipid Ethers; Photochemotherapy; Photosensitizing Agents; Pyrimidinones; Rhabdomyosarcoma; Tumor Cells, Cultured; Wilms Tumor