Genetic predisposition to acute lymphoblastic leukemia: Overview on behalf of the I-BFM ALL Host Genetic Variation Working Group

Causes of Childhood Cancer: A Review of the Recent Literature: Part I-Childhood Factors

PURPOSE

To review the childhood risk factors for pediatric cancer (diagnosis before age 20).

METHODS

We conducted literature searches using Ovid Medline and Scopus to find primary research studies, review articles, and meta-analyses published from 2014 to 3 March 2021.

RESULTS

Strong evidence indicates that an array of genetic and epigenetic phenomena, structural birth defects, and chromosomal anomalies are associated with an increased risk of various childhood cancers. Increased risk is also associated with prior cancer, likely due to previous treatment agents and therapeutic ionizing radiation. Convincing evidence supports associations between several pediatric cancers and ionizing radiation, immunosuppression, and carcinogenic virus infection both in healthy children and in association with immune suppression following organ transplantation. Breastfeeding and a childhood diet rich in fruits and vegetables appears to reduce the risk of pediatric leukemia but the evidence is less strong. Childhood vaccination against carcinogenic viruses is associated with a lower risk of several cancers; there is less strong evidence that other childhood vaccinations more broadly may also lower risk. Ultraviolet (UV) radiation is associated with increased melanoma risk, although most melanomas following childhood UV exposure occur later, in adulthood. Evidence is weak or conflicting for the role of body mass index, other childhood infections, allergies, and certain treatments, including immunomodulator medications and human growth therapy.

Cytogenetics in the management of hematologic neoplasms with germline predisposition: guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

The number of predisposing genes is continuously growing with the widespread availability of DNA sequencing, increasing the prevalence of hematologic malignancies with germline predisposition. Cytogenetic analyses provide an effective approach for the recognition of these malignancies with germline predisposition, which is critical for proper diagnosis, optimal treatment and genetic counseling. Based on the World Health Organization and the international consensus classifications as well as the European LeukemiaNet recommendations, this review first presents an advanced classification of neoplasms with germline predisposition focused on the acquired cytogenetic alterations during leukemogenesis. The various genetic rescue mechanisms and the progression to transformation are then explained. The review also outlines the specific constitutional and somatic cytogenetic aberrations indicative of germline predisposition disorders in B-acute lymphoblastic leukemia (ALL), T-ALL, bone marrow failure syndrome and myeloid neoplasms. An emphasis is made on monosomy 7 in the predisposition field, its frequency and diagnosis impact as well as its various circumstances of occurrence. Lastly, we propose cytogenetic technical recommendations and guidelines for clinical reporting of these specific aberrations.

Incidence and Mortality Rates for Childhood Acute Lymphoblastic Leukemia in Puerto Rican Hispanics, 2012-2016

BACKGROUND

Acute lymphoblastic leukemia (ALL) accounts for 80% of all leukemias diagnosed in children. Although ALL age patterns are consistent across racial/ethnic groups, their incidence and mortality rates are highly variable. We assessed the age-standardized ALL incidence and mortality rates of Puerto Rican Hispanic (PRH) children and compared them with those of US mainland Hispanics (USH), non-Hispanic Whites (NHW), non-Hispanic Blacks (NHB), and Non-Hispanic Asian or Pacific Islanders (NHAPI).

METHODS

Differences between racial/ethnic groups were assessed by estimating the standardized rate ratio (SRR) for 2010 to 2014. Secondary data analyses of the Puerto Rico Central Cancer Registry and the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) databases were performed for the 2001 to 2016 period.

RESULTS

PRH children had 31% lower incidence rates than USH, but 86% higher incidence rates than NHB. In addition, the incidence trends of ALL increased significantly from 2001 to 2016 among PRH and USH, with 5% and 0.9% per year, respectively. Moreover, PRH have a lower 5-year overall survival (81.7%) when compared with other racial/ethnic groups.

CONCLUSIONS

PRH children were found to have disparities in ALL incidence and mortality rates compared with other racial/ethnic groups in the US. Additional research is warranted to identify the genetic and environmental risk factors that may be associated with the disparities observed.

IMPACT

This is the first study reporting the incidence and mortality rates of childhood ALL for PRH and making comparisons with other racial/ethnic groups in the US. See related commentary by Mejía-Aranguré and Núñez-Enríquez, p. 999.

Functional damaging germline variants in ETV6, IKZF1, PAX5 and RUNX1 predisposing to B-cell precursor acute lymphoblastic leukemia

Recent genome-wide studies have demonstrated that a significant proportion of children with cancer carry predisposing germline variants, with varying incidence according to cancer type. In general, there is a lower incidence of underlying germline predisposing variants among patients with B-cell acute lymphoblastic leukemia (B-ALL) compared to other types of cancer, but higher rates may be found in patients with specific leukemia subtypes. Two categories of ALL-predisposing variants have been described: common polymorphisms, conferring low-penetrance ALL susceptibility, and rare variants, conferring high-penetrance ALL susceptibility. Variants in genes encoding hematopoietic transcription factors are an example of the latter, and include ETV6, IKZF1, PAX5 and RUNX1. Here, we present an overview of the germline variants detected in patients with B-ALL in these four genes and a summary of functional studies analyzing the impacts of these variants upon protein function, and hence their effects with regard to leukemia predisposition. Furthermore, we review specific clinical characteristics of patients with B-ALL, including specific features of the patient or family history and associated somatic genetic characteristics, which are suggestive of underlying germline alterations in one of these genes. This review may be of assistance in the interpretation of patient genetic germline findings, made even more challenging by the absence of a suggestive family history or by an unknown familial cancer history. Despite a low incidence of underlying germline alterations in ETV6, IKZF1, PAX5 and RUNX1 in patients with B-ALL, identification of an underlying ALL predisposition syndrome is relevant to the clinical management of patients and their relatives, as the latter are also at risk of developing cancer.

Infectious triggers and novel therapeutic opportunities in childhood B cell leukaemia

B cell acute lymphoblastic leukaemia (B-ALL) is the most common form of childhood cancer. Although treatment has advanced remarkably in the past 50 years, it still fails in ~20% of patients. Recent studies revealed that more than 5% of healthy newborns carry preleukaemic clones that originate in utero, but only a small percentage of these carriers will progress to overt B-ALL. The drivers of progression are unclear, but B-ALL incidence seems to be increasing in parallel with the adoption of modern lifestyles. Emerging evidence shows that a major driver for the conversion from the preleukaemic state to the B-ALL state is exposure to immune stressors, such as infection. Here, we discuss our current understanding of the environmental triggers and genetic predispositions that may lead to B-ALL, highlighting lessons from epidemiology, the clinic and animal models, and identifying priority areas for future research.

Recurrent somatic mutations and low germline predisposition mutations in Korean ALL patients

In addition to somatic mutations, germline genetic predisposition to hematologic malignancies is currently emerging as an area attracting high research interest. In this study, we investigated genetic alterations in Korean acute lymphoblastic leukemia/lymphoma (ALL) patients using targeted gene panel sequencing. To this end, a gene panel consisting of 81 genes that are known to be associated with 23 predisposition syndromes was investigated. In addition to sequence variants, gene-level copy number variations (CNVs) were investigated as well. We identified 197 somatic sequence variants and 223 somatic CNVs. The IKZF1 alteration was found to have an adverse effect on overall survival (OS) and relapse-free survival (RFS) in childhood ALL. We found recurrent somatic alterations in Korean ALL patients similar to previous studies on both prevalence and prognostic impact. Six patients were found to be carriers of variants in six genes associated with primary immunodeficiency disorder (PID). Of the 81 genes associated with 23 predisposition syndromes, this study found only one predisposition germline mutation (TP53) (1.1%). Altogether, our study demonstrated a low probability of germline mutation predisposition to ALL in Korean ALL patients.

Body mass index associated with childhood and adolescent high-risk B-cell acute lymphoblastic leukemia risk: A Children's Oncology Group report

BACKGROUND

Obesity is a risk factor for many adulthood cancers, but its role in childhood, adolescent, and young adult (AYA) cancer is unknown. Childhood and AYA acute lymphoblastic leukemia (ALL) incidence and obesity prevalence have shown concurrent increases. We sought to identify whether obesity may be a risk factor for childhood and AYA ALL.

METHODS

Characteristics from individuals with ALL, aged 2-30 years, diagnosed 2004-2017 and treated on Children's Oncology Group (COG) protocols with available pre-treatment anthropometric data (N = 4726) were compared to National Health and Nutrition Examination Survey controls (COG AALL17D2). Body mass index (BMI) was defined using standard CDC definitions. Multivariate conditional logistic regression assessed associations between BMI and ALL with additional analyses stratified by sex and race/ethnicity.

RESULTS

Among cases (72% high-risk (HR) B-ALL, 28% T-ALL), 5% had underweight, 58% normal weight, 17% overweight, and 20% obesity. Underweight (OR 2.11, 95% CI 1.56-2.85) and obesity (OR 1.32, 95% CI 1.15-1.53) were associated with B-ALL diagnosis. Specifically, obesity was associated with B-ALL among males (OR 1.57, 95% CI 1.30-1.91) and Hispanic children (OR 1.78, 95% CI 1.39-2.29). Obesity was also associated with central nervous system (CNS) involvement.

CONCLUSION

Pre-treatment obesity is associated with HR B-ALL among males and Hispanics, as well as with CNS involvement, suggesting common physiology between obesity and leukemogenesis. An association between underweight and ALL was confirmed, likely due to cancer-associated wasting. These results have important public health implications for obesity prevention and treatment in children and adolescents to reduce cancer risk.

B-cell acute lymphoblastic leukemia with high mutation burden presenting in a child with constitutional mismatch repair deficiency

Constitutional mismatch repair deficiency syndrome should be considered in children with acute leukemia and characteristic skin lesions. The high mutation burden of CMMRD-related cancers contributes to treatment resistance, necessitating individualized treatment strategies.

Clinical efficacy and safety of 6-thioguanine in the treatment of childhood acute lymphoblastic leukemia: A protocol for systematic review and meta-analysis

BACKGROUND

To systematic review the efficacy and safety of 6-thioguanine (6-TG) in the substitute of 6-mercaptopurine (6-MP) in the treatment for patients with childhood acute lymphoblastic leukemia (ALL) in the maintenance phase, and to explore its clinical application value. It provides theoretical guidance for the maintenance treatment of ALL in children from the perspective of evidence-based medicine.

METHODS

By means of computer retrieval, Chinese databases were searched: Chinese Biomedical Database (CBM), China national knowledge internet (CNKI), Chongqing Weipu Database (VIP), and Wanfang Database; Foreign databases: PubMed, The Cochrane Library, Embase, and Web of Science were applied to find out randomized controlled trial (RCT) for 6-TG in childhood acute lymphoblastic leukemia. By manual retrieval, documents without electronic edition and related conference papers were retrieved. The retrieval time ranges from the beginning of the establishment of the databases to September 1st, 2019. According to the inclusion, and exclusion criteria by 3 researchers, the literature screening, data extraction, and research methodological quality evaluation were completed. RevMan 5.3 software was applied to evaluate the quality of the included literature, and Stata 12.0 software was used to conduct meta-analysis of the outcome indicators of the included literature.

RESULTS

This study systematically evaluated the efficacy and safety of 6-TG in the substitute of 6-MP as a maintenance drug for childhood acute lymphoblastic leukemia. Through the key outcome indicators, this study is expected to draw a scientific, practical conclusion for 6-TG in the treatment of childhood acute lymphoblastic leukemia. This conclusion will provide evidence-based medical direction for clinical treatment.

CONCLUSION

The efficacy and safety of 6-TG in the substitute of 6-MP in the maintenance treatment of childhood acute lymphoblastic leukemia will be confirmed through this study. The conclusions will be published in relevant academic journals.

REGISTRATION

PROSPERO (registration number is CRD42020150466).

Predisposition to childhood acute lymphoblastic leukemia caused by a constitutional translocation disrupting ETV6

Pathogenic germline variants in ETV6 have been associated with familial predisposition to thrombocytopenia and hematological malignancies, predominantly childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In addition, overrepresentation of a high hyperdiploid subtype and older age at diagnosis have been reported among sporadic BCP-ALL cases with germline variants in ETV6 We studied a family with 2 second-degree relatives who developed childhood high hyperdiploid BCP-ALL at ages 8 and 12 years, respectively. A constitutional balanced reciprocal translocation t(12;14)(p13.2;q23.1) was discovered in both patients by routine karyotyping at diagnosis and, subsequently, in 7 healthy family members who had not experienced hematological malignancies. No carriers had thrombocytopenia. Whole-genome sequencing confirmed the translocation, resulting in 2 actively transcribed but nonfunctional fusion genes, causing heterozygous loss and consequently monoallelic expression of ETV6 Whole-genome sequencing analysis of the affected female subjects' leukemia excluded additional somatic aberrations in ETV6 and RTN1 as well as shared somatic variants in other genes. Expression studies, performed to confirm decreased expression of ETV6, were not conclusive. We suggest that germline aberrations resulting in monoallelic expression of ETV6 contribute to leukemia susceptibility, whereas more severe functional deficiency of ETV6 is required for developing THC5. To our knowledge, this report is the first of a constitutional translocation disrupting ETV6 causing predisposition to childhood ALL.

Genetic defects in hematopoietic transcription factors and predisposition to acute lymphoblastic leukemia

Recent genome-wide studies have revealed a plethora of germline variants that significantly influence the susceptibility to acute lymphoblastic leukemia (ALL), thus providing compelling evidence for genetic inheritance of this blood cancer. In particular, hematopoietic transcription factors (eg, ETV6, PAX5, IKZF1) are most frequently implicated in familial ALL, and germline variants in these genes confer strong predisposition (albeit with incomplete penetrance). Studies of germline risk factors for ALL provide unique insights into the molecular etiology of this leukemia.

Primary Immunodeficiency and Cancer Predisposition Revisited: Embedding Two Closely Related Concepts Into an Integrative Conceptual Framework

Common understanding suggests that the normal function of a "healthy" immune system safe-guards and protects against the development of malignancies, whereas a genetically impaired one might increase the likelihood of their manifestation. This view is primarily based on and apparently supported by an increased incidence of such diseases in patients with specific forms of immunodeficiencies that are caused by high penetrant gene defects. As I will review and discuss herein, such constellations merely represent the tip of an iceberg. The overall situation is by far more varied and complex, especially if one takes into account the growing difficulties to define what actually constitutes an immunodeficiency and what defines a cancer predisposition. The enormous advances in genome sequencing, in bioinformatic analyses and in the functional in vitro and in vivo assessment of novel findings together with the availability of large databases provide us with a wealth of information that steadily increases the number of sequence variants that concur with clinically more or less recognizable immunological problems and their consequences. Since many of the newly identified hard-core defects are exceedingly rare, their tumor predisposing effect is difficult to ascertain. The analyses of large data sets, on the other hand, continuously supply us with low penetrant variants that, at least in statistical terms, are clearly tumor predisposing, although their specific relevance for the respective carriers still needs to be carefully assessed on an individual basis. Finally, defects and variants that affect the same gene families and pathways in both a constitutional and somatic setting underscore the fact that immunodeficiencies and cancer predisposition can be viewed as two closely related errors of development. Depending on the particular genetic and/or environmental context as well as the respective stage of development, the same changes can have either a neutral, predisposing and, in some instances, even a protective effect. To understand the interaction between the immune system, be it "normal" or "deficient" and tumor predisposition and development on a systemic level, one therefore needs to focus on the structure and dynamic functional organization of the entire immune system rather than on its isolated individual components alone.

It's ALL in the Family: IKZF1 and Hereditary Leukemia

IKZF1 plays an essential role in lymphopoiesis, and somatic IKZF1 variants in acute lymphoblastic leukemia (ALL) are associated with poor prognosis. In this issue of Cancer Cell, Churchman et al. add to the list of leukemia predisposition genes with the identification and characterization of germline IKZF1 variants in childhood ALL.

Constitutional abnormalities of IDH1 combined with secondary mutations predispose a patient with Maffucci syndrome to acute lymphoblastic leukemia

Maffucci syndrome is a nonhereditary disorder caused by somatic mosaic isocitrate dehydrogenase 1 or 2 (IDH1 or IDH2) mutations and is characterized by multiple enchondromas along with hemangiomas. Malignant transformation of enchondromas to chondrosarcomas and secondary neoplasms, such as brain tumors or acute myeloid leukemia, are serious complications. A 15-year-old female with Maffucci syndrome developed B-cell precursor acute lymphoblastic leukemia (BCP-ALL). A somatic mutation in IDH1 was detected in hemangioma and leukemic cells. KRAS mutation and deletion of IKZF1 were detected in leukemic cells. Patients with Maffucci syndrome may, therefore, be at risk of BCP-ALL associated with secondary genetic events that affect lymphocyte differentiation.