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.

The effects of manganese (Mn) toxicity in different organs and tissues in humans and other vertebrates have been studied since the beginning of the past century, but most of its cellular effects remain largely unknown. In this study, we studied the effects of Mn in zebrafish, at the cellular level, due to the transparent nature of zebrafish larvae that enables a powerful analysis under the light microscope. The collection of our results shows that environmental concentrations of 0.5 mg/L affect swim bladder inflation; at concentration of 50 and 100 mg/L Mn (1) induces alterations in viability, swim bladder, heart, and size of zebrafish larvae, (2) induces an increase in melanocyte area and the formation of cellular aggregates in the skin, and (3) induces an accumulation of β-Catenin in mesenchymal cells in the caudal fin of zebrafish larvae. Our data suggest that increased levels of Mn induce cell aggregate formation in the skin and the presence of more melanocytes in the zebrafish caudal fin. Interestingly, the adhesion protein β-Catenin was activated in mesenchymal cells near the cell aggregates. These results open important new questions on the role of Mn toxicity on cellular organization and β-Catenin responses in fishes.

Aim: Oral squamous cell carcinoma (OSCC) often presents as an invasive tumor with poor prognosis. Recent evidence suggests that microRNAs, particularly miR-1-3p, may regulate the molecular pathways associated with tumor invasion. This study aimed to investigate the functional role of miR-1-3p in OSCC invasion using integrated in vitro , in vivo , and ex vivo approaches, and to evaluate its expression in tumors with varying depths of invasion (DOI). Methods: SCC-9 cells were transfected with miR-1-3p mimic and inhibitor. Invasion was assessed using transwell assays. Zebrafish xenografts were generated to evaluate tumor area, invasion depth, migration, and metastasis. Additionally, miR-1-3p expression was quantified by RT-qPCR in 26 human OSCC samples stratified by different groups of DOI. Results: miR-1-3p inhibition significantly increased tumor cell invasion in vitro ( P = 0.039) and resulted in larger, deeper, and more migratory tumors in vivo ( P < 0.05). All in vitro experiments were performed in duplicate, which may limit the precision of quantitative estimates. Metastases were observed in 30.8% of larvae injected with miR-1-3p–inhibited cells, representing a trend toward increased metastatic behavior ( P = 0.052). In human samples, miR-1-3p expression was significantly negatively correlated with DOI (Spearman’s R = − 0.435; P = 0.030), and deeply invasive tumors exhibited lower expression levels ( P = 0.040). Conclusion: This integrative analysis supports an association between miR-1-3p downregulation and increased invasive tumor behavior in OSCC across experimental models and human tumor samples. These findings provide preliminary translational evidence and support further investigation into the potential role of miR-1-3p as a biomarker in OSCC.