Zebrafish Models for Human Cancer

Abstract

For decades, the advancement of cancer research has relied on in vivo models for examining key processes in cancer pathogenesis, including neoplastic transformation, progression, and response to therapy. These studies, which have traditionally relied on rodent models, have engendered a vast body of scientific literature. Recently, experimental cancer researchers have embraced many new and alternative model systems, including the zebrafish (Danio rerio). The general benefits of the zebrafish model for laboratory investigation, such as cost, size, fecundity, and generation time, were quickly superseded by the discovery that zebrafish are amenable to a wide range of investigative techniques, many of which are difficult or impossible to perform in mammalian models. These advantages, coupled with the finding that many aspects of carcinogenesis are conserved in zebrafish as compared with humans, have firmly established a unique niche for the zebrafish model in comparative cancer research. This article introduces methods for generating cancer models in zebrafish and reviews a range of models that have been developed for specific cancer types. Keywords animal disease models, cancer, genetic modification, zebrafishThe zebrafish (Danio rerio) emerged as a model for scientific research in the 1930s, with many early studies devoted to the investigation of developmental processes in embryos. 53 The use of zebrafish in research has subsequently expanded into a broad range of disciplines. As a research species, zebrafish offer certain advantages over traditional vertebrate models, including rapid generation time, high fecundity, external embryonic development, a capacity for high stocking density in relatively small areas, and lower maintenance costs. 64 In recent years, the zebrafish has come into its own as a relevant comparative model for a diverse spectrum of human diseases.Although zebrafish are relative newcomers to the field of comparative cancer research, these small animals have emerged as a powerful tool for investigators. As vertebrate organisms, they share many features of embryonic development and adult anatomy that are critical for comparative animal models. 64,71 In the world of cancer research, this has important implications ranging from conserved signaling pathways and transcriptional regulatory mechanisms, to organogenesis and tissue differentiation, to cellular transformation and tumor initiation. Zebrafish cancer models have been produced by a variety of methods, leading to a broad spectrum of cancer susceptibilities in animals of multiple age groups. Flexibility in genetic manipulation, adaptability to current tools for cancer analysis, and capacity to define cellular and molecular interactions in vivo provide the zebrafish with its own very unique set of advantages for the investigation of cancer biology. Mechanisms for Developing Cancer Models in ZebrafishZebrafish cancer models have been developed by a number of mechanisms (Table 1). Although initial studies relied on chemical carcinogens for t...

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“…Several strategies have been used to generate cancer models and to identify cancer-related genes in zebrafish: treatment with chemical carcinogens, forward genetic screening, reverse genetic approaches, transgenic models, and xenotransplantation of mammalian cancer cells (Tobia et al 2011, Shive 2013.…”

“…Treating fish with carcinogens is very easy to set-up because the watersoluble carcinogens can be added to the fish water and embryos, larvae, and adult animals can be exposed for longer time periods (Feitsma & Cuppen 2008). Although the routes of exposure to carcinogens may differ between fish and mammalians, the liver is the primary target for many carcinogens in both fish and rodents (Shive 2013).…”

“…Screening is performed by PCR amplification of specific exons from each mutagenized zebrafish followed by mutation detection through direct resequencing of PCR fragments or alternatively, by CEL1 endonucleasemediated mutation discovery (Liu & Leach 2011, Shive 2013. Once a mutant of interest is identified, individuals isolated from the library and mutant lines are established (Moens et al 2008).…”

“…These damages are imprecisely repaired by nonhomologous end joining a DNA repair pathway frequently causing small insertions or deletions at the break site. Therefore, engineered zinc-finger nucleases can be designed to deliver frameshift mutations at specific sites in the genome of the zebrafish (Liu & Leach 2011, Santoriello & Zon 2012, Shive 2013.…”

“…TALENs are chimeric nucleases generated by a transcription activator-like (TAL) effector DNA-binding domain, constructed to bind any desired DNA sequence fused to a DNA cleavage domain. This system enables targeted gene disruption in a wide variety of model organisms, is easier to design and assemble compared with zinc-finger nucleases (Santoriello & Zon 2012, Shive 2013. Recent works have reported that TALENs can induce mutations in endogenous zebrafish genes, showing a high efficiency in inducing locus-specific DNA breaks in somatic and germline tissues (at some loci this efficacy approaches 100%) (Bedell et al 2012, Ma et al 2013.…”