Author ORCID Identifier

https://orcid.org/0000-0001-5112-7288

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department

Molecular and Cellular Biochemistry

First Advisor

Dr. Jessica Blackburn

Second Advisor

Dr. Tianyan Gao

Abstract

T-cell Acute Lymphoblastic Leukemia (T-ALL) is an aggressive blood cancer. There are no immunotherapies and few molecularly targeted therapeutics available for the treatment of this malignancy. The identification and characterization of genes and pathways that drive T-ALL progression is critical for the development of new therapies for T-ALL. The protein tyrosine phosphatase PTP4A3, also known as PRL-3, has been extensively reported to play a causative role in numerous cancers, including several types of blood malignancies. However, its role in T-ALL is not well defined.

Here, we determined that the PRL-3 plays a critical role in T-ALL initiation and progression by promoting leukemia cell migration. PRL-3 is highly expressed in patient T-ALL samples at both mRNA and protein levels compared to normal lymphocytes. Knock-down of PRL-3 expression using short-hairpin RNA (shRNA) in human T-ALL cell lines significantly impeded T-ALL cell migration capacity in vitro and reduced their ability to engraft and proliferate in xenograft mouse models. Additionally, PRL-3 over-expression in a Myc-induced zebrafish T-ALL model significantly accelerated disease onset and shortened the time needed for cells to enter blood circulation. Reverse phase protein array (RPPA) and gene set enrichment analysis (GSEA) revealed that the SRC signaling pathway is affected by PRL-3. Immunoblot analyses validated that manipulation of PRL-3 expression in T-ALL cells affected the SRC signaling pathway, which is directly involved in cell migration, although SRC was not a direct substrate of PRL-3. More importantly, T-ALL cell growth and migration was inhibited by small molecule inhibition of PRL-3, suggesting that PRL-3 has potential as a therapeutic target in T-ALL.

Finally, we identified a pool of PRL-3 interacting proteins in T-ALL using BioID-based proximal labeling approach. Co-immunoprecipitation assays were used to validate a number of direct interacting partners of PRL-3, including LCK and CD3.

Taken together, our study identifies PRL-3 as an oncogenic driver in T-ALL both in vitro and in vivo and provides a strong rationale for targeted therapies that interfere with PRL-3 function. We also identified PRL-3 interactomes in T-ALL, which lays foundation for future PRL-3 substrates study.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.278

Funding Information

St. Baldrick’s Foundation Research Grant, 2017

NIH grants DP2CA228043, R01CA227656 (to J.S.B.), 2018

NIH Training Grant T32CA165990 (M.G.H.), 2018

Included in

Biochemistry Commons

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