PROJECT SUMMARY

Long-term complications of cancer therapy with chemotherapy and radiotherapy are well recognized, and have prompted careful follow-up of cancer survivors. One such complication is the development of secondary blood cancers, including therapy-related myeloid neoplasms (t–MNs) such as myelodysplastic syndromes (t-MDS) and acute myeloid leukemia (t-AML). Therapy-related blood cancers have a relatively poor response to conventional treatment regimens with chemotherapy and blood stem cell transplantation. The biological and genetic characteristics of the therapy-related malignances are largely unknown, but these features likely contribute to their high resistance to treatment. We proposed to model and study the initiation of treatment-related myeloid leukemia in a zebrafish model. Zebrafish are vertebrate organisms and have a high degree of similarity to human biology and genetics, especially in the blood system making this model an attractive platform for discoveries in blood diseases like leukemia.

The goal of our proposal was to study the process that leads to therapy-related blood cancers, and find novel treatment regimens for this unique set of diseases. Recent discoveries of unique genetic mutations in t-MDS or t-AML provided us with an opportunity to model these diseases in the zebrafish and use this model organism to answer questions about the initiation of these diseases and to test drugs at the organismal level to treat or to prevent these cancers. We focused on two genes that are most commonly found in t-MDS and t-AML, TP53 and PPM1D. Using CRISPR-Cas9 approach, we introduced mutations in these genes in zebrafish at the time of development, and tested the effect of radiation in adulthood on the behavior of the mutations and possible disease initiation. In addition, to better study the nature of mutations in TP53 and PPM1D gene, we made zebrafish lines that have particular mutations in their blood from birth, and will be using them to study the role of secondary mutations that occur in t-MDS and t-AML which promote the disease establishment and the mechanism by which they do so. These mutant zebrafish lines will also serve as the platform for in vivo drug screening to test compounds that are able to prevent leukemia development from mutated TP53 or PPM1D.