Rapidly progressing acute myeloid leukemia with KAT6A-LEUTX fusion in a newborn

The MOZ-BRPF1 acetyltransferase complex in epigenetic crosstalk linked to gene regulation, development, and human diseases

Acetylation of lysine residues on histone tails is an important post-translational modification (PTM) that regulates chromatin dynamics to allow gene transcription as well as DNA replication and repair. Histone acetyltransferases (HATs) are often found in large multi-subunit complexes and can also modify specific lysine residues in non-histone substrates. Interestingly, the presence of various histone PTM recognizing domains (reader domains) in these complexes ensures their specific localization, enabling the epigenetic crosstalk and context-specific activity. In this review, we will cover the biochemical and functional properties of the MOZ-BRPF1 acetyltransferase complex, underlining its role in normal biological processes as well as in disease progression. We will discuss how epigenetic reader domains within the MOZ-BRPF1 complex affect its chromatin localization and the histone acetyltransferase specificity of the complex. We will also summarize how MOZ-BRPF1 is linked to development via controlling cell stemness and how mutations or changes in expression levels of MOZ/BRPF1 can lead to developmental disorders or cancer. As a last touch, we will review the latest drug candidates for these two proteins and discuss the therapeutic possibilities.

Neoplasia-associated Chromosome Translocations Resulting in Gene Truncation

Chromosomal translocations in cancer as well as benign neoplasias typically lead to the formation of fusion genes. Such genes may encode chimeric proteins when two protein-coding regions fuse in-frame, or they may result in deregulation of genes via promoter swapping or translocation of the gene into the vicinity of a highly active regulatory element. A less studied consequence of chromosomal translocations is the fusion of two breakpoint genes resulting in an out-of-frame chimera. The breaks then occur in one or both protein-coding regions forming a stop codon in the chimeric transcript shortly after the fusion point. Though the latter genetic events and mechanisms at first awoke little research interest, careful investigations have established them as neither rare nor inconsequential. In the present work, we review and discuss the truncation of genes in neoplastic cells resulting from chromosomal rearrangements, especially from seemingly balanced translocations.

A novel BRD4-LEUTX fusion in a pediatric sarcoma with epithelioid morphology and diffuse S100 expression

Malignant epithelioid soft tissue tumors encompass a wide spectrum of lesions. Among them, Epithelioid Malignant Peripheral Nerve Sheath Tumors (MPNST) constitute a distinct subgroup, accounting for <5% of all MPNST. Epithelioid MPNST are infrequently associated with neurofibromatosis type 1, occasionally arise in a schwannoma and show diffuse S100 and CD34 expression, often combined with INI-1 loss. However, the molecular mechanisms underlying the tumorigenesis of epithelioid MPNST remain largely unknown. We describe a case of a 10-year-old girl with an epithelioid malignancy of the orbit. The tumor proved positive for S100, CD34 and SOX10, and, although INI-1 expression was maintained, the overall features suggested the possibility of an epithelioid MPNST, arising in an unusual location. NGS analysis revealed a novel in-frame BRD4-LEUTX fusion gene. LEUTX plays an important role in embryonal genome activation and its expression is mostly suppressed postnatally. We were able to detect increased levels of LEUTX transcript in the tumor, indicating that BRD4-LEUTX fusion leads to LEUTX re-activation. To our knowledge, this fusion has never been reported previously. Whether the current case represents an example of epithelioid MPNST or a distinct tumor entity remains to be determined.

Case Report: A Unique Case of Pediatric Central Nervous System Embryonal Tumor Harboring the CIC-LEUTX Fusion, Germline NBN Variant and Somatic TSC2 Mutation: Expanding the Spectrum of CIC-Rearranged Neoplasia

Central nervous system (CNS) embryonal tumors (WHO grade IV) are a heterogeneous group of rare, poorly differentiated neuroepithelial malignant neoplasms that commonly occur in children, and they have a poor prognosis. The 2016 WHO (World Health Organization) classification of CNS tumors created a major shift in paradigm of the classification of embryonal tumors. However, some cases were still difficult to classify. Further integrative genomic analysis is needed to improve the precise classification, diagnosis and treatment of CNS embryonal tumors. Herein, we firstly report a case of CNS embryonal tumor harboring the pathogenic CIC–LEUTX gene fusion. A 2-year-old male infant presented with a solid cystic mass in the left temporal lobe-basal ganglia and left parietal lobe (maximum diameter, 75 mm) and underwent gross tumor resection. The tumor was classified as a poorly differentiated embryonal neoplasm of neuroectodermal origin that lacked specific features and rosettes. By immunohistochemistry, the tumor cells were strongly positive for synaptophysin, and the Ki67 proliferation index was high (>50%). FISH (Fluorescence in situ hybridization) results indicated no change in the copy number at the 19q13.42 C19MC locus. Next generation sequencing showed a CIC–LEUTX gene fusion, a somatic TSC2 c.G2714A mutation, and a heterozygous germline NBN c.C127T mutation. One month after surgery, there was recurrence of the intracranial tumor (maximum diameter, 55 mm) as well as spinal cord implantation metastasis. The patient received chemotherapy (CTX+CBP+VCR/DDP+VP-16), radiotherapy, and a drug targeting the TSC2 gene (everolimus). At the time of this writing, the patient is alive without evidence of disease for 11 months. This is the first report of the CIC–LEUTX gene fusion in a case of CNS embryonal tumor.