Zebrafish Models of Paediatric Brain Tumours

Abstract

Paediatric brain cancer is the second most common childhood cancer and is the leading cause of cancer-related deaths in children. Despite significant advancements in the treatment modalities and improvements in the 5-year survival rate, it leaves long-term therapy-associated side effects in paediatric patients. Addressing these impairments demands further understanding of the molecularity and heterogeneity of these brain tumours, which can be demonstrated using different animal models of paediatric brain cancer. Here we review the use of zebrafish as potential in vivo models for paediatric brain tumour modelling, as well as catalogue the currently available zebrafish models used to study paediatric brain cancer pathophysiology, and discuss key findings, the unique attributes that these models add, current challenges and therapeutic significance.

Keywords: animal models; paediatric brain cancer; zebrafish.

Figure 1

Paediatric brain and CNS tumour locations. (A) The paediatric brain tumour types and their location within the brain and CNS and (B) zebrafish brain anatomy [28] are shown. CNS-PNET, central nervous system–primitive neuroectodermal tumour; AT/RT, atypical teratoid rhabdoid tumour.

Figure 2

Paediatric cancer modelling in zebrafish involves three main approaches, (A) Genetic mutagenesis, (B) transgenesis and (C) transplantation models. Genetic modelling (A) involves the use of multiple techniques, such as historical engineered nucleases, including Zinc Finger Nucleases (ZFNs), Transcription Activator-Like Effector Nucleases (TALENs) and the current generation of engineered nucleases, and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology with different variants, such as Cas9 and Cas12a, as well as approaches such as multi-targeting to achieve bi-allelic somatic mutations in F0 generation. Transgenesis approach (B) allows tumour modelling with spatial (a) and temporal (b) control on the expression of a target gene or an oncogene (ONC) of interest. Spatial transgenesis techniques, such as tol2 transposon system, Gal4/UAS and Cre-Lox, offer the tissue-specific expression of target gene with the help of a tissue-specific promotor (TSP), where temporal control is offered by Tet-on and Tet-off systems as well as the heat shock promoter, hsp70. Transplantation approach (C) involves the injection of human cancer cells or patient-derived xenografts (PDXs) (a) into 2 days post-fertilized (dpf) wild-type (WT) or casper embryos and/or immune-deficient casper adults (prkdc^−/− il2rgc.a^−/−) or injecting tumour cells derived from zebrafish brain tumours (b) into casper adults to study tumour formation and metastasis. HDR—homology-directed repair, NHEJ—non-homologous end joining, ssODNs—single-stranded oligonucleotides, dpf—days post-fertilization.

Figure 2

Paediatric cancer modelling in zebrafish involves three main approaches, (A) Genetic mutagenesis, (B) transgenesis and (C) transplantation models. Genetic modelling (A) involves the use of multiple techniques, such as historical engineered nucleases, including Zinc Finger Nucleases (ZFNs), Transcription Activator-Like Effector Nucleases (TALENs) and the current generation of engineered nucleases, and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology with different variants, such as Cas9 and Cas12a, as well as approaches such as multi-targeting to achieve bi-allelic somatic mutations in F0 generation. Transgenesis approach (B) allows tumour modelling with spatial (a) and temporal (b) control on the expression of a target gene or an oncogene (ONC) of interest. Spatial transgenesis techniques, such as tol2 transposon system, Gal4/UAS and Cre-Lox, offer the tissue-specific expression of target gene with the help of a tissue-specific promotor (TSP), where temporal control is offered by Tet-on and Tet-off systems as well as the heat shock promoter, hsp70. Transplantation approach (C) involves the injection of human cancer cells or patient-derived xenografts (PDXs) (a) into 2 days post-fertilized (dpf) wild-type (WT) or casper embryos and/or immune-deficient casper adults (prkdc^−/− il2rgc.a^−/−) or injecting tumour cells derived from zebrafish brain tumours (b) into casper adults to study tumour formation and metastasis. HDR—homology-directed repair, NHEJ—non-homologous end joining, ssODNs—single-stranded oligonucleotides, dpf—days post-fertilization.