Abstract 3559: Ubiquitin C-terminal hydrolase L1 (UCHL1) modulates uterine papillary serous cancer progression through interaction with cyclin B1

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Background: Uterine papillary serous carcinoma (UPSC) comprises less than 10% of all endometrial cancers but accounts for a disproportionately high number of deaths. Few prospective studies focus solely on this aggressive subtype, making it difficult to determine optimal treatment strategies. The purpose of this study was therefore to identify novel therapeutic targets that could aid in the management of UPSC. Methods: Clinical and RNA sequencing data from The Cancer Genome Atlas (TCGA) was used to identify genes that were differentially expressed between endometrioid endometrial carcinoma (EEC) and UPSC, which also showed a significant association with overall patient survival duration in UPSC patients. Ubiquitin C-terminal hydrolase L1 (UCHL1) upregulation and correlation with survival was validated by immunohistochemical staining of an independent cohort of paraffin samples. UCHL1 was silenced by siRNA transfection and lentiviral shRNA transduction in UPSC cell lines ARK1, ARK2 and HEC50 to evaluate the role of UCHL1 on cell proliferation, migration and cell cycle progression. RPPA data from TCGA was used to identify proteins whose expression correlated with UCHL1 expression. Interaction between UCHL1 and cyclin B1 was determined by co-immunoprecipitation. The effect of UCHL1 silencing on cyclin B1 levels was evaluated by Western blot analysis, and the effect on cell cycle progression was determined by flow cytometry. Results: UCHL1 mRNA and protein expression levels were significantly higher in in UPSC compared to EEC. Kaplan-Meier analysis and cox regression of the TCGA data set and an independent cohort of patient samples revealed that UCHL1 expression correlated significantly with poorer overall survival in UPSC, especially in late-stage patients. siRNA-mediated silencing did not affect cell migration, but reduced the proliferation rates of ARK1, ARK2 and HEC50 in vitro. UCHL1 RNA expression was positively correlated with cyclin B1 protein levels in the TCGA data set. Accordingly, UCHL1 silencing reduced cyclin B1 protein but not mRNA expression levels in ARK1, ARK2 and HEC50. Cell cycle analysis of ARK1, ARK2 and HEC50 after UCHL1 silencing showed a reduction in the percentage of cells in the S and G2/M phases, with or without cell synchronization. Conclusion: These findings indicate that UCHL1 contributes to the aggressiveness of UPSC by stabilizing cyclin B1 and increasing cell proliferation, suggesting that it may be a therapeutic target for UPSC. Citation Format: Suet Ying Kwan, Samuel C. Mok, Kwong-Kwok Wong, Rosemarie E. Schmandt, Karen H. Lu. Ubiquitin C-terminal hydrolase L1 (UCHL1) modulates uterine papillary serous cancer progression through interaction with cyclin B1. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3559. doi:10.1158/1538-7445.AM2015-3559