Tracing and Targeting the Origins of Childhood Cancer

Despite the success of treating childhood cancers with cytotoxic agents, novel therapeutic strategies are required to achieve the next leap in cure rates. A promising avenue may be to target the origin of childhood cancers. Here, we review recent advances in tracing the origins of pediatric tumors. Cancer-to-normal cell comparisons by single-cell mRNA sequencing reveal the fetal state of cancer cells, as well as their cell of origin. Recent phylogenetic analyses have uncovered large tissue-resident precursor clones to childhood cancers, which already possess key genomic alterations leading to tumor formation. Both the transcriptional fetalness and genomic status of the premalignant tissue bed provide further avenues for targeted therapy. Overall, these advances begin to describe the precise origins of pediatric tumors and pave the way for novel methods in detecting, treating, and perhaps even preventing childhood cancers. Expected final online publication date for the Annual Review of Cancer Biology, Volume 6 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Therapeutic Targeting of Exportin-1 in Childhood Cancer

Overexpression of Exportin-1 (XPO1), a key regulator of nuclear-to-cytoplasmic transport, is associated with inferior patient outcomes across a range of adult malignancies. Targeting XPO1 with selinexor has demonstrated promising results in clinical trials, leading to FDA approval of its use for multiple relapsed/refractory cancers. However, XPO1 biology and selinexor sensitivity in childhood cancer is only recently being explored. In this review, we will focus on the differential biology of childhood and adult cancers as it relates to XPO1 and key cargo proteins. We will further explore the current state of pre-clinical and clinical development of XPO1 inhibitors in childhood cancers. Finally, we will outline potentially promising future therapeutic strategies for, as well as potential challenges to, integrating XPO1 inhibition to improve outcomes for children with cancer.

The Use of Inhibitors of Tyrosine Kinase in Paediatric Haemato-Oncology—When and Why?

The fundamental pathophysiology of malignancies is dysregulation of the signalling pathways. Protein tyrosine kinases (PTKs) are among the enzymes which, if mutated, play a critical role in carcinogenesis. The best-studied rearrangement, which enhances PTK activity and causes atypical proliferation, is BCR-ABL1. Abnormal expression of PTKs has proven to play a significant role in the development of various malignancies, such as chronic myelogenous leukaemia, brain tumours, neuroblastoma, and gastrointestinal stromal tumours. The use of tyrosine kinase inhibitors (TKIs) is an outstanding example of successful target therapy. TKIs have been effectively applied in the adult oncology setting, but there is a need to establish TKIs’ importance in paediatric patients. Many years of research have allowed a significant improvement in the outcome of childhood cancers. However, there are still groups of patients who have a poor prognosis, where the intensification of chemotherapy could even cause death. TKIs are designed to target specific PTKs, which lead to the limitation of severe adverse effects and increase overall survival. These advances will hopefully allow new therapeutic approaches in paediatric haemato-oncology to emerge. In this review, we present an analysis of the current data on tyrosine kinase inhibitors in childhood cancers.

MALIGNANCY MASQUERADING AS JOINT INFECTION- A CASE REPORT

ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) is the most common malignancy in children. It accounts for 25% of all childhood cancers and approximately 75% of all cases of childhood leukemia. ALL presents usually with fever, lassitude, pallor, bone pains+/- bleeds. Here, we present a case of a child presenting with prolonged fever and swelling and pain in joints. Child was initially diagnosed as one hematological disorder and presented with joint effusion within a week.

Fanconi Anaemia, Childhood Cancer and the BRCA Genes

Fanconi anaemia (FA) is an inherited chromosomal instability disorder characterised by congenital and developmental abnormalities and a strong cancer predisposition. In less than 5% of cases FA can be caused by bi-allelic pathogenic variants (PGVs) in BRCA2/FANCD1 and in very rare cases by bi-allelic PGVs in BRCA1/FANCS. The rarity of FA-like presentation due to PGVs in BRCA2 and even more due to PGVs in BRCA1 supports a fundamental role of the encoded proteins for normal development and prevention of malignant transformation. While FA caused by BRCA1/2 PGVs is strongly associated with distinct spectra of embryonal childhood cancers and AML with BRCA2-PGVs, and also early epithelial cancers with BRCA1 PGVs, germline variants in the BRCA1/2 genes have also been identified in non-FA childhood malignancies, and thereby implying the possibility of a role of BRCA PGVs also for non-syndromic cancer predisposition in children. We provide a concise review of aspects of the clinical and genetic features of BRCA1/2-associated FA with a focus on associated malignancies, and review novel aspects of the role of germline BRCA2 and BRCA1 PGVs occurring in non-FA childhood cancer and discuss aspects of clinical and biological implications.

Sustained viral remission with directly acting antivirals in the treatment of chronic hepatitis C among adolescent (12-17 years) survivors of childhood leukemia

Studies from India highlight the high prevalence of hepatitis C (6-25%) infection in survivors of childhood cancers. Recently Directly acting antivirals (DAA) have been approved for treatment of Chronic hepatitis C (CHC) in children >12 years of age. Even though there are reports of efficacy and safety of DAAs in the treatment of CHC in hematologic disorders like thalassemia, there is minimal data on the efficacy of DAA in the management of chronic hepatitis C among adolescent survivors of childhood leukaemia. We performed this retrospective analysis to study Sustained viral remission (SVR) with DAA in the treatment of CHC among adolescent (12-17 years) survivors of childhood leukemia. This study also aimed to analyze the genotypic profile of hepatitis C virus and adverse effects of the DAA in this group of adolescents (12-17 years). 5 adolescents (12-17 years) who were diagnosed with CHC during August 2017 to May 2020 were enrolled in this observational study. All belonged to genotype 1; received DAA regimen comprising of sofosbuvir 400 mg and ledipasvir 90 mg for 12 weeks with good drug compliance and no major adverse effects. All of them attained SVR at 12 weeks after completing treatment. This study among adolescent survivors of childhood leukaemia with chronic hepatitis C genotype 1, augments data regarding efficacy of a 12 weeks DAA regimen comprising of sofosbuvir 400 mg and ledipasvir 90 mg in the attainment of SVR at 12 weeks after completing treatment.

DEVOLUTION—A method for phylogenetic reconstruction of aneuploid cancers based on multiregional genotyping data

Phylogenetic reconstruction of cancer cell populations remains challenging. There is a particular lack of tools that deconvolve clones based on copy number aberration analyses of multiple tumor biopsies separated in time and space from the same patient. This has hampered investigations of tumors rich in aneuploidy but few point mutations, as in many childhood cancers and high-risk adult cancer. Here, we present DEVOLUTION, an algorithm for subclonal deconvolution followed by phylogenetic reconstruction from bulk genotyping data. It integrates copy number and sequencing information across multiple tumor regions throughout the inference process, provided that the mutated clone fraction for each mutation is known. We validate DEVOLUTION on data from 56 pediatric tumors comprising 253 tumor biopsies and show a robust performance on simulations of bulk genotyping data. We also benchmark DEVOLUTION to similar bioinformatic tools using an external dataset. DEVOLUTION holds the potential to facilitate insights into the development, progression, and response to treatment, particularly in tumors with high burden of chromosomal copy number alterations.

Therapeutic targeting of the PLK1-PRC1-axis triggers cell death in genomically silent childhood cancer

Chromosomal instability (CIN) is a hallmark of cancer1. Yet, many childhood cancers, such as Ewing sarcoma (EwS), feature remarkably ‘silent’ genomes with minimal CIN2. Here, we show in the EwS model how uncoupling of mitosis and cytokinesis via targeting protein regulator of cytokinesis 1 (PRC1) or its activating polo-like kinase 1 (PLK1) can be employed to induce fatal genomic instability and tumor regression. We find that the EwS-specific oncogenic transcription factor EWSR1-FLI1 hijacks PRC1, which physiologically safeguards controlled cell division, through binding to a proximal enhancer-like GGAA-microsatellite, thereby promoting tumor growth and poor clinical outcome. Via integration of transcriptome-profiling and functional in vitro and in vivo experiments including CRISPR-mediated enhancer editing, we discover that high PRC1 expression creates a therapeutic vulnerability toward PLK1 inhibition that can repress even chemo-resistant EwS cells by triggering mitotic catastrophe.Collectively, our results exemplify how aberrant PRC1 activation by a dominant oncogene can confer malignancy but provide opportunities for targeted therapy, and identify PRC1 expression as an important determinant to predict the efficacy of PLK1 inhibitors being used in clinical trials.