Advancing Diagnostics and Therapy to Reach Universal Cure in Childhood ALL

Mutational mechanisms in multiply relapsed pediatric acute lymphoblastic leukemia

Pediatric acute lymphoblastic leukemia (ALL) is marked by low mutational load at initial diagnosis, which increases at relapse. To determine which processes are active in (relapsed) ALL and how they behave during disease progression before and after therapy, we performed whole genome sequencing on 97 tumor samples of 29 multiply relapsed ALL patients. Mutational load increased upon relapse in 28 patients and upon every subsequent relapse in 22 patients. In addition to two clock-like mutational processes, we identified UV-like damage, APOBEC activity, reactive oxygen species, thiopurine-associated damage and an unknown therapy component as drivers of mutagenesis. Mutational processes often affected patients over longer time periods, but could also occur in isolated events, suggesting the requirement of additional triggers. Thiopurine exposure was the most prominent source of new mutations in relapse, affecting over half of the studied patients in first and/or later relapse and causing potential relapse-driving mutations in multiple patients. Our data demonstrate that multiple mutational processes frequently act in parallel as prominent secondary drivers with dynamic activity during ALL development and progression.

C-C Chemokine Receptor 7 Promotes T-Cell Acute Lymphoblastic Leukemia Invasion of the Central Nervous System via β2-Integrins

C-C Chemokine Receptor 7 (CCR7) mediates T-cell acute lymphoblastic leukemia (T-ALL) invasion of the central nervous system (CNS) mediated by chemotactic migration to C-C chemokine ligand 19 (CCL19). To determine if a CCL19 antagonist, CCL198-83, could inhibit CCR7-induced chemotaxis and signaling via CCL19 but not CCL21, we used transwell migration and Ca2+ mobilization signaling assays. We found that in response to CCL19, human T-ALL cells employ β2 integrins to invade human brain microvascular endothelial cell monolayers. In vivo, using an inducible mouse model of T-ALL, we found that we were able to increase the survival of the mice treated with CCL198-83 when compared to non-treated controls. Overall, our results describe a targetable cell surface receptor, CCR7, which can be inhibited to prevent β2-integrin-mediated T-ALL invasion of the CNS and potentially provides a platform for the pharmacological inhibition of T-ALL cell entry into the CNS.

IKZF1 in acute lymphoblastic leukemia: the rise before the fall?

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and adolescents and in recent decades, the survival rates have risen to >90% in children largely due the introduction of risk adapted therapy. Therefore, knowledge of factors influencing risk of relapse is important. The transcription factor IKAROS is a regulator of lymphocyte development and alterations of its coding gene, IKZF1, are frequent in ALL and are associated with higher relapse risk. This concise review will discuss the normal function of IKAROS together with the effect of gene alterations in ALL such as relieved energy restriction and altered response to anti-leukemic drugs. Besides the biology, the clinical impact of gene alterations in the different subtypes of ALL will be discussed. Finally, possibilities for treating ALL with IKZF1 alterations will be considered including novel therapies like cell signaling inhibitors and immunotherapy.

Increased risk of subsequent neoplasm after hematopoietic stem cell transplantation in 5-year survivors of childhood acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) survivors are at risk for developing subsequent neoplasms, but there is limited information on long-term risks and risk factors for both subsequent malignant neoplasms (SMNs) and subsequent non-malignant neoplasms (SNMNs). We analyzed long-term risk and risk factors for SMNs and SNMNs among 3291 5-year ALL survivors from the Dutch Childhood Cancer Survivor Study-LATER cohort (1963-2014). We calculated standardized incidence ratios (SIRs) and cumulative incidences and used multivariable Cox proportional hazard regression analyses for analyzing risk factors. A total of 97 survivors developed SMNs and 266 SNMNs. The 30-year cumulative incidence was 4.1% (95%CI: 3.5-5.3) for SMNs and 10.4%(95%CI: 8.9-12.1) for SNMNs. Risk of SMNs was elevated compared to the general population (SIR: 2.6, 95%CI: 2.1-3.1). Survivors treated with hematopoietic stem cell transplantation (HSCT) with total body irradiation (TBI) (HR:4.2, 95%CI: 2.3-7.9), and without TBI (HR:4.0,95%CI: 1.2-13.7) showed increased SMN risk versus non-transplanted survivors. Cranial radiotherapy (CRT) was also a risk factor for SMNs (HR:2.1, 95%CI: 1.4-4.0). In conclusion, childhood ALL survivors have an increased SMN risk, especially after HSCT and CRT. A key finding is that even HSCT-treated survivors without TBI treatment showed an increased SMN risk, possibly due to accompanied chemotherapy treatment. This emphasizes the need for careful follow-up of HSCT and/or CRT-treated survivors.

Naked antibodies and antibody-drug conjugates: targeted therapy for childhood acute lymphoblastic leukemia

The treatment of childhood acute lymphoblastic leukemia (ALL) has reached overall survival rates exceeding 90%. The present and future challenges are to cure the remainder of patients still dying from disease, and to reduce morbidity and mortality in those who can be cured with standard-of-care chemotherapy by replacing toxic chemotherapy elements while retaining cure rates. With the novel therapeutic options introduced in the last years, including immunotherapies and targeted antibodies, the treatment of ALL is undergoing major changes. For B-cell precursor ALL, blinatumomab, an anti-CD19 bispecific antibody, has established its role in the consolidation treatment for both high- and standard-risk first relapse of ALL, in the presence of bone marrow involvement, and may also have an impact on the outcome of high-risk subsets such as infant ALL and Philadelphia chromosome-positive ALL. Inotuzumab ozogamicin, an anti-CD22 drug conjugated antibody, has demonstrated high efficacy in inducing complete remission in relapsed ALL, even in the presence of high tumor burden, but randomized phase III trials are still ongoing. For T-ALL the role of CD38-directed treatment, such as daratumumab, is gaining interest, but randomized data are needed to assess its specific benefit. These antibodies are currently being tested in patients with newly diagnosed ALL and may lead to major changes in the present paradigm of treatment of pediatric ALL. Unlike the past, lessons may be learned from innovations in adult ALL, in which more drastic changes are piloted that may need to be translated to pediatrics.

Distinct Responses to Menin Inhibition and Synergy with DOT1L Inhibition in KMT2A-Rearranged Acute Lymphoblastic and Myeloid Leukemia

Pediatric acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) exhibit favorable survival rates. However, for AML and ALL patients carrying KMT2A gene translocations clinical outcome remains unsatisfactory. Key players in KMT2A-fusion-driven leukemogenesis include menin and DOT1L. Recently, menin inhibitors like revumenib have garnered attention for their potential therapeutic efficacy in treating KMT2A-rearranged acute leukemias. However, resistance to menin inhibition poses challenges, and identifying which patients would benefit from revumenib treatment is crucial. Here, we investigated the in vitro response to revumenib in KMT2A-rearranged ALL and AML. While ALL samples show rapid, dose-dependent induction of leukemic cell death, AML responses are much slower and promote myeloid differentiation. Furthermore, we reveal that acquired resistance to revumenib in KMT2A-rearranged ALL cells can occur either through the acquisition of MEN1 mutations or independently of mutations in MEN1. Finally, we demonstrate significant synergy between revumenib and the DOT1L inhibitor pinometostat in KMT2A-rearranged ALL, suggesting that such drug combinations represent a potent therapeutic strategy for these patients. Collectively, our findings underscore the complexity of resistance mechanisms and advocate for precise patient stratification to optimize the use of menin inhibitors in KMT2A-rearranged acute leukemia.

Late Complications in Long-Term Childhood Cancer Survivors: What the Oral Health Professional Needs to Know

With diagnostic and therapeutic advances, over 80% of children diagnosed with cancer become long-term survivors. As the number of childhood cancer survivors (CCS) continues to increase, dental practitioners become more likely to have CCS among their patients. CCS may develop late complications from damage caused by their cancer treatment to endocrine, cardiovascular, musculoskeletal, and other organ systems. These complications may surface decades after the completion of treatment. Adverse outcomes of childhood cancer treatment frequently involve oral and craniofacial structures including the dentition. Tooth development, salivary gland function, craniofacial growth, and temporomandibular joint function may be disturbed, increasing oral health risks in these individuals. Moreover, CCS are at risk of developing subsequent malignancies, which may manifest in or near the oral cavity. It is important that dental practitioners are aware of the childhood cancer history of their patients and have knowledge of potential late complications. Therefore, this narrative review aims to inform dental practitioners of late oral complications of cancer treatment modalities commonly used in pediatric oncology. Furthermore, selected common non-oral late sequelae of cancer therapy that could have an impact on oral health and on delivering dental care will be discussed.