Date of Graduation
12-2015
Document Type
Dissertation (PhD)
Program Affiliation
Cancer Biology
Degree Name
Doctor of Philosophy (PhD)
Advisor/Committee Chair
Kwong-Kwok Wong
Committee Member
Russell Broaddus
Committee Member
Joya Chandra
Committee Member
Samuel Mok
Committee Member
Anil Sood
Abstract
SWI/SNF is mutated in about 20% of all human cancers; in particular ARID1A is the most frequently mutated SWI/SNF subunit. ARID1A is a tumor suppressor gene, inactivating mutations in ARID1A are most frequently found in ovarian and endometrial cancers, specifically uterine corpus endometrioid carcinomas (UCEC), ovarian clear cell carcinomas (OCCC) and ovarian endometrioid carcinomas (OEC). The functional roles of ARID1A are not completely understood and there are limited therapeutic strategies that specifically target ARID1A-mutant cancers. Given that ARID1A expression is lost in cancer, ARID1A mutations cannot be targeted directly and novel therapeutic strategies are required to target ARID1A-mutant cancers.
In this study, drug responses between ARID1A-wildtype and ARID1A-mutant cell lines were compared using the ‘Genomics of Drug Sensitivities in Cancer’ database. From this analysis, I found that ARID1A-mutant cell lines are more sensitive to elesclomol, which is a reactive oxygen species (ROS)-inducing agent. This finding was validated using a panel of ovarian and endometrial cancer cell lines, where ARID1A-mutant cell lines exhibited lower IC50 values and higher apoptotic rates when treated with elesclomol. Knockdown and re-expression of ARID1A in ovarian cancer cells showed that ARID1A is required to protect cancer cells from oxidative stress. In the absence of ARID1A, intracellular ROS levels were increased, and this increase was required for increased cell growth upon ARID1A depletion.
Next, I investigated the relationship between ARID1A and NRF2, the major regulator of the antioxidant response in the cell. I found that ARID1A negatively regulates the expression of NRF2. Knockdown of NRF2 in ovarian cancer cell lines revealed that NRF2 expression may be preferentially required for protection from oxidative stress and cell proliferation in ARID1A-mutant cells. Analysis using The Cancer Genome Atlas (TCGA) UCEC dataset revealed that ARID1A-mutant tumor samples have higher expression of NRF2 and NRF2-target genes.
In summary, this study revealed novel roles of ARID1A in protecting ovarian cancer cells against oxidative stress. In the absence of ARID1A, NRF2 is up-regulated and may be required to compensate for ARID1A deficiency. These findings suggest that ROS-inducing agents and NRF2 inhibitors may be used as therapeutic strategies in targeting ARID1A-mutant ovarian cancer cells.
Keywords
ARID1A, SWI/SNF, oxidative stress, ROS, NRF2, elesclomol