**10.2 Melanoma**

By crossing the *tp53* mutant zebrafish with a transgenic line expressing a mutant, constitutively active form of BRAF (V600E, which is the same mutation frequently observed in human melanomas) under control of the melanocyte microphthalmiaassociated transcription factor (*mitfa*) promoter, it was found that these fish develop melanomas spontaneously in preference to MPNSTs. In these fish formation of small nevi can be observed already at a young age, and these nevi continue to progress into large malignant, metastatic melanomas in multiple locations from approximately 4-6 months of age.

Malignant melanoma tumor cells from the tumor bearing fish can be transplanted into sublethally gamma irradiated wild type zebrafish, where they will grow and spread much like tumors in the mouse xenograft models described previously (Patton et al, 2005).

### **10.3 T-ALL**

Aberrant expression of Myc in humans induces lymphoma and leukemia. Similarly in zebrafish a T cell acute lymphoblastic leukemia (T-ALL) zebrafish model was generated by microinjection of the mouse *c-myc* (*mMyc*) gene under control of the zebrafish *Rag2*

promoter (*zRag2*). Onset of tumors varied between 30 to 131 days post injection of the *Rag2 mMyc* expression plasmid. Fish developing T-ALL were characterized by inflated abdominal cavities and infiltration of malignant cells (transformed lymphoblasts) throughout the body, under the skin, into base of the pectoral fin, olfactory region, and the retrorbital soft tissue that led to splayed eyes.

These malignant lymphoblasts were transplantable into irradiated wild type adult zebrafish giving rise to small tumors appearing already one week post transplantation (Langenau et al, 2003)

## **10.4 Rhabdomyocarcoma**

Rhabdomyosarcoma (RMS) is a very aggressive soft tissue sarcoma with high incidence seen among children compared to other types of cancer. The zebrafish RMS model was generated by injecting a Rag2-kRASG12D construct, expressing a constitutively active isoform of RAS under the Rag2 promoter, into the zebrafish embryo at one cell stage. Visible highly invasive tumors in liver, intestine, kidney, and testes appeared already 10 days post injection, in accordance with the early onset of these tumors in human patients, distinguishing this model as one of the fastest spontaneous, vertebrate tumor models available (Langenau et al, 2007).
