Zebrafish as a Model for Translational Immuno-Oncology

Abstract

Despite remarkable progress in cancer immunotherapy, many agents that show efficacy in murine or in vitro models fail to translate clinically. Zebrafish (Danio rerio) have emerged as a powerful complementary model that addresses several limitations of traditional systems. Their optical transparency, genetic tractability, and conserved immune and oncogenic signaling pathways enable high-resolution, real-time imaging of tumor-immune interactions in vivo. Importantly, zebrafish offer a unique opportunity to study the core mechanisms of health and sickness, complementing other models and expanding our understanding of fundamental processes in vivo. This review provides an overview of zebrafish immune system development, highlighting tools for tracking innate and adaptive responses. We discuss their application in modeling immune evasion, checkpoint molecule expression, and tumor microenvironment dynamics using transgenic and xenograft approaches. Platforms for high-throughput drug screening and personalized therapy assessment using patient-derived xenografts ("zAvatars") are evaluated, alongside limitations, such as temperature sensitivity, immature adaptive immunity in larvae, and interspecies differences in immune responses, tumor complexity, and pharmacokinetics. Emerging frontiers include humanized zebrafish, testing of next-generation immunotherapies, such as CAR T/CAR NK and novel checkpoint inhibitors (LAG-3, TIM-3, and TIGIT). We conclude by outlining the key challenges and future opportunities for integrating zebrafish into the immuno-oncology pipeline to accelerate clinical translation.

Keywords: patient-derived xenografts (zAvatars); translational oncology; zebrafish.

Figure 1

In vivo imaging of tumor–immune interactions in a zebrafish xenograft model. Fluorescently labeled 5637 bladder cancer cells (red, CM-DiI) were microinjected into the perivitelline space (PVS) of 2 days post-fertilization (dpf) zebrafish larvae. The image shows the tumor at 1 day post-injection (1 dpi), when larvae were 3 dpf. Tumor localization and interaction with innate immune cells (green) are visible in real time. This model enables live analysis of tumor progression, immune cell recruitment, and drug response. Imaging was acquired at the INFABiC Facility (Unicamp, Brazil). The schematic illustrates functional applications such as immune–tumor interaction analysis and high-throughput drug screening.

Figure 2

Zebrafish as a translational avatar for human cancer xenografts. Illustration of the zebrafish larval xenograft platform as a versatile in vivo model for cancer research. Fluorescently labeled human tumor cells are microinjected into transparent zebrafish larvae at 2–3 days post-fertilization, enabling real-time visualization of tumor behavior, including proliferation, angiogenesis, invasion, and immune cell interactions. The model supports rapid, high-throughput drug screening via compound immersion and allows for phenotypic readouts within a few days. Combined with genetic tools and imaging capabilities, zebrafish xenografts provide a powerful and scalable platform for translational oncology and functional precision medicine.