Abstract 3019: PRL3 contributes to the onset and progression of T-cell acute lymphoblastic leukemia in a zebrafish model
Authors: Sieg Rachel E. , Hausman Elizabeth S. , Blackburn Jessica 
Published: August 2018

Abstract
T-cell acute lymphoblastic leukemia (T-ALL) is a major clinical challenge, representing 15-25% of all acute lymphoblastic leukemias in children and adults. The survival rate for pediatric patients with relapsed T-ALL is a disheartening &lt;30% in pediatric patients and &lt;10% in adults. Current drugs against T-ALL include highly cytotoxic chemotherapies, which are generally ineffective against relapse and are particularly hard for young children to receive. These harsh therapies can result in a spectrum of developmental issues and potent side effects. Therefore, it is imperative to develop molecular therapies that can effectively inhibit T-ALL development without contributing to the adverse side effects of chemotherapy. We have found that the gene Protein Tyrosine Phosphatase 4A3 (PRL3) plays a role in T-ALL onset and development, making it a possible drug target for molecular therapies. Previously, PRL3 has not been associated with leukemia onset or progression, but here we show overexpression of PRL3 leads to increased T-ALL onset and aggressiveness, while PRL3 knockout leads to reduced T-ALL onset in a zebrafish T-ALL model. We identified PRL3 as an important driver of human T-ALL by performing a comparative genomic hybridization array on single-cell clones that evolved increased LPC frequency after serial transplantation from single leukemic cells in the zebrafish in a screen involving over 6,000 animals. We then overexpressed PRL3 via microinjection into 1-cell stage embryos, and tracked the rate of T-ALL onset and progression using fluorescent and confocal microscopy to generate a Kaplan-Meier graph. We found that overexpression increased the rate of leukemia onset and led to lethality quicker than in control zebrafish. We then knocked out PRL3 using a CRISPR-Cas9 strategy by microinjecting our constructs into 1-cell stage embryos and generating a similar Kaplan-Meier graph. By knocking out PRL3, we found that leukemia onset was delayed and progression to lethality was significantly slower than control zebrafish (p&lt; 0.01). We then treated the T-ALL fish with two specific inhibitors, one that inhibited all PRLs and one that was specific to PRL3 (n= 60). We found that leukemia onset was significantly delayed when treated with the PRL inhibitor (p&lt;0.001), but no significant difference was found when treated with the specific PRL3 inhibitor. We conclude that PRL3 is a novel gene important for T-ALL onset and progression. It has potential as a drug target to inhibit the growth and progression of leukemic cells. Future directions will be identifying and characterizing downstream substrates of this protein tyrosine phosphatase and doing combination drug screens to increase the inhibitory effects on T-ALL. We expect that these data will be directly relevant to future mammal studies and eventual clinical trials as alternatives to the traditional chemotherapy offered now.
Citation Format: Rachel E. Sieg, Elizabeth S. Hausman, Jessica Blackburn. PRL3 contributes to the onset and progression of T-cell acute lymphoblastic leukemia in a zebrafish model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3019.