While some attempts in this direction have been made [44], these and other diverse solid tumors will require further development. One of the biggest challenges in experimental cancer research is to

demonstrate that the model in question recapitulates the human disease. While zebrafish tumors generally resemble their intended human cancers on a histological level [1•, 7, 8 and 24], there remain differences in tumor spectrum, incidence and onset [3•, 5 and 24] that are still not well understood. An emerging mode of comparison is through new genomic technologies, which, with careful exploitation, may also point to genetic events that are important for malignant human tumor evolution. Several studies have begun to compare genomic aberrations in zebrafish cancer to those in human. Rudner et al. [ 45] employed high-density array comparative genomic hybridization (aCGH) Thiazovivin in vivo Venetoclax supplier to zebrafish and human T-ALL and found a small number of repeatedly altered genes in zebrafish that also recur in human. Greater overlap was shown in samples from advanced stages of the disease, indicating a heightened conservation for genes under selective pressure. In another study, Zhang et al. [ 46] sequenced a large cohort of zebrafish malignant peripheral nerve

sheath tumors (MPNSTs) and distinguished amplified genes that were shared with the human disease. While the identification of these commonly mutated genes is a promising first step, their experimental validation will be critical toward demonstrating their biological significance. Our group recently investigated the full spectrum of coding mutations in a zebrafish cancer through exome sequencing of melanomas derived from BRAF and NRAS-driven transgenic lines [ 76]. In probing for secondary genetic events important for melanoma development, we found that the mutation burden in zebrafish melanomas was sparse compared to human cancer, and equally heterogeneous BCKDHA to the point that cross-species comparisons were

difficult. Despite the mutation load, we were able to quantify the multi-hit model of these engineered cancers and highlight a potential new cooperating event with BRAF and p53 mutation through the protein kinase A-cyclic AMP pathway. The work provides the first insights into the mutagenic processes of an engineered zebrafish cancer and will be instructive in guiding future studies of this type in zebrafish. In particular, it is clear from our experience that there are technical challenges in adapting sequencing tools to zebrafish that require substantial optimization and development. The tremendous diversity both within and between zebrafish strains [47 and 48], nearly a magnitude greater than that of human, combined with the duplicated genome and other species-specific differences can complicate alignment and overwhelm somatic mutation algorithms with false calls.