Discussing and managing hematologic germ line variants

Transcription factor genetics and biology in predisposition to bone marrow failure and hematological malignancy

Transcription factors (TFs) play a critical role as key mediators of a multitude of developmental pathways, with highly regulated and tightly organized networks crucial for determining both the timing and pattern of tissue development. TFs can act as master regulators of both primitive and definitive hematopoiesis, tightly controlling the behavior of hematopoietic stem and progenitor cells (HSPCs). These networks control the functional regulation of HSPCs including self-renewal, proliferation, and differentiation dynamics, which are essential to normal hematopoiesis. Defining the key players and dynamics of these hematopoietic transcriptional networks is essential to understanding both normal hematopoiesis and how genetic aberrations in TFs and their networks can predispose to hematopoietic disease including bone marrow failure (BMF) and hematological malignancy (HM). Despite their multifaceted and complex involvement in hematological development, advances in genetic screening along with elegant multi-omics and model system studies are shedding light on how hematopoietic TFs interact and network to achieve normal cell fates and their role in disease etiology. This review focuses on TFs which predispose to BMF and HM, identifies potential novel candidate predisposing TF genes, and examines putative biological mechanisms leading to these phenotypes. A better understanding of the genetics and molecular biology of hematopoietic TFs, as well as identifying novel genes and genetic variants predisposing to BMF and HM, will accelerate the development of preventative strategies, improve clinical management and counseling, and help define targeted treatments for these diseases.

Genetic predisposition to cancers in children and adolescents

PURPOSE OF REVIEW

Childhood cancer is rare, but it remains the leading cause of disease-related mortality among children 1-14 years of age. As exposure to environmental factors is lower in children, inherited genetic factors become an important player in the cause of childhood cancer. This review highlights the current knowledge and approach for cancer predisposition syndromes in children.

RECENT FINDINGS

Current literature suggests that 10-18% of paediatric cancer patients have an underlying genetic susceptibility to their disease. With better knowledge and technology, more genes and syndromes are being discovered, allowing tailored treatment and surveillance for the probands and their families.Studies have demonstrated that focused surveillance can detect early malignancies and increase overall survival in several cancer predisposition syndromes. Various approaches have been proposed to refine early tumour detection strategies while minimizing the burden on patients and families. Newer therapeutic strategies are being investigated to treat, or even prevent, tumours in children with cancer predisposition.

SUMMARY

This review summarizes the current knowledge about different cancer predisposition syndromes, focusing on the diagnosis, genetic counselling, surveillance and future directions.

Adult-onset hereditary myeloid malignancy and allogeneic stem cell transplantation

Hereditary myeloid malignancies, especially in adults or elderly persons, had been considered quite rare before the next-generation sequencing era; however, increased usage of clinical sequencing has revealed much higher prevalence of inherited myeloid malignancies. DDX41 and various pathogenic germline mutations have newly been recognized as the cause of adult-onset familial leukemia and myeloid malignancies. Although germline predisposition to myeloid neoplasms had been categorized as a provisional entity in the World Health Organization classification of hematopoietic neoplasms in 2016, methodology for the identification of hereditary myeloid malignancies has not been fully established yet. In addition, many unresolved problems, such as epidemiology, the exact pathogenic mechanisms, and ideal treatment strategy, including indications of allogeneic hematopoietic stem cell transplantation, still remain. Related donor selection for stem cell transplant is a particularly sensitive issue due to the possibility of germline mutation of the candidate relatives and the risk of donor cell leukemia after transplantation. Here, we reviewed the current evidence regarding epidemiology, diagnosis, mechanisms of progression, and transplantation strategy for hereditary myeloid malignancies.

Clinical Interpretation Challenges of Germline-Shared Somatic Variants in Cancer

OBJECTIVE

To investigate the interpretation differences of germline-shared somatic variants.

METHODS

A total of 123,302 COSMIC variants associated with hematologic malignant neoplasms were used. The pathogenicity and actionability of shared variants were analyzed based on the standardized guidelines.

RESULTS

The overall frequency of variants shared in ClinVar/HGMD and COSMIC was 10%. The pathogenicity of 54 shared variants was pathogenic/likely pathogenic (P/LP; n = 30), variants of unknown significance (n = 3), and benign/likely benign (n = 21). In total, 30 P/LP variants were reclassified to tier I/tier II (83%) and tier III (17%) variants.

CONCLUSIONS

This is the first study about different clinical interpretations of shared variants based on the current standard guidelines. This study takes a meaningful step in bridging the interpretation gap between the somatic and germline variants.

Impact of somatic and germline mutations on the outcome of systemic mastocytosis

Systemic mastocytosis (SM) is a highly heterogeneous disease with indolent and aggressive forms, with the mechanisms leading to malignant transformation still remaining to be elucidated. Here, we investigated the presence and frequency of genetic variants in 34 SM patients with multilineal KIT D816V mutations. Initial screening was performed by targeted sequencing of 410 genes in DNA extracted from purified bone marrow cells and hair from 12 patients with nonadvanced SM and 8 patients with advanced SM, followed by whole-genome sequencing (WGS) in 4 cases. Somatic mutations were further investigated in another 14 patients with advanced SM. Despite the fact that no common mutation other than KIT D816V was found in WGS analyses, targeted next-generation sequencing identified 67 nonsynonymous genetic variants involving 39 genes. Half of the mutations were somatic (mostly multilineal), whereas the other half were germline variants. The presence of ≥1 multilineal somatic mutation involving genes other than KIT D816V, ≥3 germline variants, and ≥1 multilineal mutation in the SRSF2, ASXL1, RUNX1, and/or EZH2 genes (S/A/R/E genes), in addition to skin lesions, splenomegaly, thrombocytopenia, low hemoglobin levels, and increased alkaline phosphatase and β2-microglobulin serum levels, were associated with a poorer patient outcome. However, the presence of ≥1 multilineal mutation, particularly involving S/A/R/E genes, was the only independent predictor for progression-free survival and overall survival in our cohort.

Germ line predisposition to myeloid malignancies appearing in adulthood

INTRODUCTION

Germ line predisposition to myeloid neoplasms has been incorporated in the WHO 2016 classification of myeloid neoplasms and acute leukemia. The new category of disease is named hereditary myeloid disorder (HMD). Although most myeloid neoplasms are sporadic, germ line mutations and familial predisposition can contribute to development of chronic myeloid diseases and acute myeloid leukemia. This finding and upcoming frequent use of genome wide detection of molecular aberrations will lead to a higher detection rate of a genetic predisposition and influence treatment decisions. Hereditary predisposition is responsible for 5-10% of myeloid malignancies. Management of affected patients begins by the awareness of treating physicians of the problem and a precise work up of the patient and family members. Areas covered: This review focuses on current knowledge about germ line predisposition for myeloid neoplasms including diagnostic, prognostic, and therapeutic aspects in adult patients. Essential information for clinical routine is provided. Expert commentary: Compared to a patient without predisposition, adaptation of treatment strategy for patients with an HMD is often necessary, especially to avoid higher risk of relapse or higher toxicity during chemotherapy or transplantation. Mistakes in choice of a related donor can be omitted. Relatives at risk of developing a HMD need specific surveillance.

Recommendations for Surveillance for Children with Leukemia-Predisposing Conditions

Leukemia, the most common childhood cancer, has long been recognized to occasionally run in families. The first clues about the genetic mechanisms underlying familial leukemia emerged in 1990 when Li-Fraumeni syndrome was linked to TP53 mutations. Since this discovery, many other genes associated with hereditary predisposition to leukemia have been identified. Although several of these disorders also predispose individuals to solid tumors, certain conditions exist in which individuals are specifically at increased risk to develop myelodysplastic syndrome (MDS) and/or acute leukemia. The increasing identification of affected individuals and families has raised questions around the efficacy, timing, and optimal methods of surveillance. As part of the AACR Childhood Cancer Predisposition Workshop, an expert panel met to review the spectrum of leukemia-predisposing conditions, with the aim to develop consensus recommendations for surveillance for pediatric patients. The panel recognized that for several conditions, routine monitoring with complete blood counts and bone marrow evaluations is essential to identify disease evolution and enable early intervention with allogeneic hematopoietic stem cell transplantation. However, for others, less intensive surveillance may be considered. Because few reports describing the efficacy of surveillance exist, the recommendations derived by this panel are based on opinion, and local experience and will need to be revised over time. The development of registries and clinical trials is urgently needed to enhance understanding of the natural history of the leukemia-predisposing conditions, such that these surveillance recommendations can be optimized to further enhance long-term outcomes. Clin Cancer Res; 23(11); e14-e22. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Incidental detection of germline variants of potential clinical significance by massively parallel sequencing in haematological malignancies

Massively parallel sequencing (MPS) technology has become routinely available for diagnosis, prognostication and therapeutic decision-making in haematological malignancies. However, increased throughput and wider coverage of genes can have unintended consequences. Germline variants of potential clinical significance (GVPCSs) detected during cancer testing may have implications for patients and families beyond the biological evaluation of a specific tumour. 721 reports generated from MPS panels used in the routine testing of myeloid and lymphoid malignancies were reviewed and variants within genes of potential germline relevance (TP53, RUNX1, GATA2 and WT1 in all contexts and CBL, KRAS and NRAS in the setting of juvenile myelomonocytic leukaemia) were analysed. A variant allele fraction threshold of ≥33.09% for considering germline origin of variants within cancer samples was established. The detection rate of incidental, pathogenic germline variants was 0.42%. Patient education and confirmatory germline sample testing of GVPCSs in appropriate circumstances are recommended.