Author ORCID Identifier
0000-0002-8222-3827
Date of Graduation
5-2017
Document Type
Dissertation (PhD)
Program Affiliation
Cancer Biology
Degree Name
Doctor of Philosophy (PhD)
Advisor/Committee Chair
Karen H Lu
Committee Member
Russell R Broaddus
Committee Member
Wenliang Li
Committee Member
Samuel C Mok
Committee Member
Kwong-Kwok Wong
Abstract
Uterine papillary serous carcinoma (UPSC) is an aggressive form of endometrial cancer with poor survival rates and a high risk of recurrence. The rarity of UPSC poses challenges to the discovery of novel targeted therapies. Therefore, the purpose of this dissertation was to identify novel therapeutic targets that could aid in the management of UPSC. To do so, we began with the relatively large cohort of UPSC cases in the TCGA data set, which was used to identify differentially expressed genes between UPSC and low-grade endometrioid endometrial carcinoma (EEC) and normal tissue.
We identified Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) to be a gene of interest, as it was significantly upregulated in UPSC and correlated with poorer overall survival. These findings were validated through immunohistochemical analysis of an independent cohort of tumor samples. Due to its role as a deubiquitinating enzyme, we hypothesized that UCHL1 contributes to UPSC tumor progression by modulating the protein stability of target genes.
To test this hypothesis, we first examined the functional role of UCHL1 in UPSC progression. Subsequently, we found that UCHL1 silencing reduced cell proliferation in vitro and in vivo. The treatment of UPSC-bearing mice with the UCHL1-specific inhibitor LDN-57444 via intraperitoneal injection also reduced tumor growth and increased overall survival times.
Next, we found that the effect of UCHL1 on increased cell proliferation was due to its ability to stabilize cyclin B1 protein, an essential protein in mitotic progression. Specifically, we demonstrated that UCHL1 and cyclin B1 interact with each other in both the cytoplasm and nuclear space prior to mitosis. UCHL1 silencing increased the deubiquitination of cyclin B1, suggesting that UCHL1 counteracts the ubiquitination of cyclin B1 by the anaphase-promoting complex. Accordingly, UCHL1 silencing slowed the progression of cells into mitosis. Taken together, our findings indicate that UCHL1 impairs the degradation of cyclin B1, leading to uncontrolled cell cycle progression. In summary, we have identified UCHL1 as a prognostic marker for UPSC and a viable therapeutic target.
Keywords
Endometrial cancer, uterine papillary serous carcinoma, UCHL1, cyclin B1