Genomic gain at 6p21: a new cryptic molecular rearrangement in secondary myelodysplastic syndrome and acute myeloid leukemia

High Mobility Group A1 Chromatin Keys: Unlocking the Genome During MPN Progression

Patients with chronic, indolent myeloproliferative neoplasms (MPNs) are at risk for transformation to highly lethal leukemia, although targetable mechanisms driving progression remain elusive. We discovered that the High Mobility Group A1 (HMGA1) gene is up-regulated with MPN progression in patients and required for evolution into myelofibrosis (MF) or acute myeloid leukemia (AML) in preclinical models. HMGA1 encodes the HMGA1 epigenetic regulators that modulate the chromatin state during embryogenesis and tissue regeneration. While HMGA1 is silenced in most differentiated cells, it becomes aberrantly re-expressed in JAK2 mutant (JAK2-V617F) MPN, with the highest levels after transformation to secondary MF or AML. Here, we review recent work highlighting HMGA1 function in MPN progression. Though underlying mechanisms continue to emerge, increasing evidence suggests that HMGA1 functions as a "chromatin key" required to "unlock" regions of the genome involved in clonal expansion and progression in MPN. Together, these findings illuminate HMGA1 as a driver of MPN progression and a promising therapeutic target.

Clonal Hematopoiesis Without Malignant Transformation Lasting Over 2 Years in a 9-Year-old Boy, Following Treatment for Acute Lymphocytic Leukemia

Children with acute lymphocytic leukemia rarely develop secondary hematological neoplasms. A 5-year-old boy was diagnosed with standard-risk precursor B-cell acute lymphocytic leukemia. The patient exhibited aberrant chromosomal changes in the bone marrow at 6 months postchemotherapy: 46,XY,der(6) t(1;6)(q12;p22) dup(6)(p22p12)[15]. Clinically, the patient has sustained complete remission and has not developed myeloid malignancy over the subsequent period (27 mo). The cytogenetic aberration was observed in 11% of CD34+ cells isolated from the bone marrow. We infer that the abnormal clone acquires self-renewal potency, differentiation, and growth advantage. Further long-term observation is needed to determine the nature of this cytogenetic aberration.

"Reversible" myelodysplastic syndrome or ineffectual clonal haematopoiesis? - add(6p) myeloid neoplasm with a spontaneous cytogenetic remission

Cytotoxic chemotherapy has inherent mutagenic potential and alters the bone marrow microenvironment after therapy. In some cases, this potentiates expansion of an aberrant clone and may lead to a therapy-related myeloid neoplasm if the clone overcomes selective pressure. We present the case of a 43-year-old woman diagnosed with an indolent, therapy-related myeloid neoplasm with an isolated chromosome 6p abnormality following treatment for de novo Acute Myeloid Leukaemia (AML), who manifest a sustained spontaneous cytogenetic remission two years later, possibly due to an ineffectual or non-dominant founding clone. This case reminds us to be mindful of the possibility that clonal haematopoiesis may not always equate to clinically relevant disease, even in the setting of an abnormal clonal karyotype.

Therapy-related Acute Leukemia With Mixed Phenotype and Novel t(1: 6)(q25;p23) After Treatment for High-risk Neuroblastoma

Neuroblastoma is the most common extracranial malignancy of childhood. Patients with high-risk disease receive multimodal treatment including chemotherapy combinations containing alkylating agents and topoisomerase inhibitors with potential for inducing therapy-related malignancy later in life. Most commonly, cytogenetic changes of pediatric therapy-related myelodysplastic syndrome/acute myeloid leukemia involve chromosome 5 or 7. Here we report a novel case of therapy-related myelodysplastic syndrome/acute myeloid leukemia 30 months after treatment for high-risk neuroblastoma with biphenotypic cell surface markers and a not yet described translocation t(1;6)(q25;p23).

The Human Proteome Organization Chromosome 6 Consortium: integrating chromosome-centric and biology/disease driven strategies

The Human Proteome Project (HPP) is designed to generate a comprehensive map of the protein-based molecular architecture of the human body, to provide a resource to help elucidate biological and molecular function, and to advance diagnosis and treatment of diseases. Within this framework, the chromosome-based HPP (C-HPP) has allocated responsibility for mapping individual chromosomes by country or region, while the biology/disease HPP (B/D-HPP) coordinates these teams in cross-functional disease-based groups. Chromosome 6 (Ch6) provides an excellent model for integration of these two tasks. This metacentric chromosome has a complement of 1002-1034 genes that code for known, novel or putative proteins. Ch6 is functionally associated with more than 120 major human diseases, many with high population prevalence, devastating clinical impact and profound societal consequences. The unique combination of genomic, proteomic, metabolomic, phenomic and health services data being drawn together within the Ch6 program has enormous potential to advance personalized medicine by promoting robust biomarkers, subunit vaccines and new drug targets. The strong liaison between the clinical and laboratory teams, and the structured framework for technology transfer and health policy decisions within Canada will increase the speed and efficacy of this transition, and the value of this translational research.

BIOLOGICAL SIGNIFICANCE

Canada has been selected to play a leading role in the international Human Proteome Project, the global counterpart of the Human Genome Project designed to understand the structure and function of the human proteome in health and disease. Canada will lead an international team focusing on chromosome 6, which is functionally associated with more than 120 major human diseases, including immune and inflammatory disorders affecting the brain, skeletal system, heart and blood vessels, lungs, kidney, liver, gastrointestinal tract and endocrine system. Many of these chronic and persistent diseases have a high population prevalence, devastating clinical impact and profound societal consequences. As a result, they impose a multi-billion dollar economic burden on Canada and on all advanced societies through direct costs of patient care, the loss of health and productivity, and extensive caregiver burden. There is no definitive treatment at the present time for any of these disorders. The manuscript outlines the research which will involve a systematic assessment of all chromosome 6 genes, development of a knowledge base, and development of assays and reagents for all chromosome 6 proteins. We feel that the informatic infrastructure and MRM assays developed will place the chromosome 6 consortium in an excellent position to be a leading player in this major international research initiative. This article is part of a Special Issue: Can Proteomics Fill the Gap Between Genomics and Phenotypes?

New recurrent chromosome change in pediatric therapy-related myelodysplastic syndrome: unbalanced translocation 1/6 with cryptic duplication of short arm of chromosome 6

The incidence of therapy-related myelodysplastic syndrome (t-MDS) in pediatric patients is increasing in parallel with the more successful management of the primary tumor, but scant information is available on clinical and cytogenetic characteristics. We report here two children affected by t-MDS after chemo/radiotherapy for a primary solid tumor, both with an unbalanced translocation 1/6 in their bone marrow. Characterization by array comparative genomic hybridization of the imbalances showed an almost identical pattern: almost complete trisomy of the long arm of chromosome 1, and a terminal deletion and interstitial duplication of the short arm of chromosome 6. The gain of chromosome 6 short arm encompasses regions already highlighted as possibly relevant for t-MDS in adults, and we suggest that the unbalanced translocation reported here be considered a new recurrent, non-random chromosomal abnormality in pediatric patients with t-MDS.