Recurrent ubiquitin B silencing in gynecological cancers establishes dependence on ubiquitin C
Alexia T. Kedves, … , Michael S. Goldberg, William C. Forrester
Alexia T. Kedves, … , Michael S. Goldberg, William C. Forrester
Published November 13, 2017
Citation Information: J Clin Invest. 2017;127(12):4554-4568. https://doi.org/10.1172/JCI92914.
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Research Article Genetics Oncology

Recurrent ubiquitin B silencing in gynecological cancers establishes dependence on ubiquitin C

Abstract

Transcriptional repression of ubiquitin B (UBB) is a cancer-subtype-specific alteration that occurs in a substantial population of patients with cancers of the female reproductive tract. UBB is 1 of 2 genes encoding for ubiquitin as a polyprotein consisting of multiple copies of ubiquitin monomers. Silencing of UBB reduces cellular UBB levels and results in an exquisite dependence on ubiquitin C (UBC), the second polyubiquitin gene. UBB is repressed in approximately 30% of high-grade serous ovarian cancer (HGSOC) patients and is a recurrent lesion in uterine carcinosarcoma and endometrial carcinoma. We identified ovarian tumor cell lines that retain UBB in a repressed state, used these cell lines to establish orthotopic ovarian tumors, and found that inducible expression of a UBC-targeting shRNA led to tumor regression, and substantial long-term survival benefit. Thus, we describe a recurrent cancer-specific lesion at the level of ubiquitin production. Moreover, these observations reveal the prognostic value of UBB repression and establish UBC as a promising therapeutic target for ovarian cancer patients with recurrent UBB silencing.

Authors

Alexia T. Kedves, Scott Gleim, Xiaoyou Liang, Dennis M. Bonal, Frederic Sigoillot, Fred Harbinski, Sneha Sanghavi, Christina Benander, Elizabeth George, Prafulla C. Gokhale, Quang-De Nguyen, Paul T. Kirschmeier, Robert J. Distel, Jeremy Jenkins, Michael S. Goldberg, William C. Forrester

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Figure 5

Low UBB expression is sufficient to establish dependency on UBC in diverse-lineage tumors.

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Low UBB expression is sufficient to establish dependency on UBC in diver...
(A) PLK1 and UBC siRNAs were serially diluted and transfected into UBBWT (black) and UBBLO (red) cells. Concentrations of target siRNA ranged from 0.16 to 20 nM and included a complementary amount of control nontargeting (NT) siRNA for a final total concentration of 20 nM. Dashed line denotes the 10% viability level (gray). This study was performed 3 times with each point in the siRNA dilution series as a singlicate. (B) Long-term viability in colony formation assays following transfection with siRNAs for PLK1, NT, and 2 independent siRNAs for UBC. After 14 days, cells were fixed and stained with crystal violet. Cell line names shown in red are UBBLO, black are UBBWT. The study was performed multiple times in different configurations. (C) Cell cycle analysis 30 hours after transfection of UBBWT and UBBLO cells with siRNAs against PLK1, UBC, NT, or no-siRNA controls. Distribution across the cell cycle is shown as percentage G1 (top) and G2 (bottom) with SD of biological replicates and repeated twice. Cell cycle data from UBBLO and UBBWT cells are shown as red and black bars, respectively. (D) A histogram of DNA content per cell is shown for OVCAR8 transfected with NT siRNA control (top) and UBC siRNA (bottom). This study was performed twice.