Browsing by Subject "DNA Helicases"
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Item The Role of RUVBL1/RUVBL2 and Their Potential as Therapeutic Targets in Non-Small Cell Lung Cancer(2019-07-31) Yenerall, Paul Matthew, II; DeBerardinis, Ralph J.; Minna, John D.; Kittler, Ralf; Mangelsdorf, David J.; Kraus, W. LeeBehind heart disease, cancer is the leading cause of death today in Americans. Among cancers, lung cancer is the deadliest, killing as many individuals as next 3 most lethal cancer types combined. Approximately 80% of lung cancers are a type known as non-small cell lung cancer (NSCLC), and despite numerous advances in the treatment of NSCLC, only 18% of all NSCLC patients live 5 years after their initial diagnosis. To identify new therapeutic targets in NSCLC, we performed a viability-based RNA interference (RNAi) screen targeting nuclear receptors, their coregulators and chromatin remodelers. This screen identified RUVBL1 and RUVBL2 (collectively referred to as RUVBL1/2) as differentially required for the viability of NSCLC. We show that RUVBL1/2 require their ATPase activity to support NSCLC viability and have developed an orally bioavailable, potent and specific inhibitor of RUVBL1/2 ATPase activity, known as Compound B. Multiple unbiased analyses suggested that RUVBL1/2 may have roles in DNA replication in NSCLC, and inhibition or depletion of RUVBL1/2 in sensitive NSCLC lines delays S-phase progression and ultimately results in cancer cell death via replication catastrophe. While Compound B treatment in vivo produces modest anti-tumor activity, only a subset of NSCLC cell lines show a therapeutically meaningful response. To enhance the efficacy of Compound B, we searched for therapies that may synergize with Compound B. Various analyses indicated that RUVBL1/2 may have roles in the response to ionizing radiation (IR), and indeed, genetic depletion or pharmacological inhibition of RUVBL1/2 radiosensitized NSCLC cell lines and patient tumors both in vitro and in vivo. Interestingly, Compound B, did not radiosensitize models of non-transformed cells, potentially because key DNA damage proteins such as ATM and DNA-PKcs were more stable after Compound B treatment in normal cells than in tumor cells. The combined necessity of RUVBL1/2 for NSCLC viability and the recovery from radiation, specifically in tumor cells, make RUVBL1/2 an attractive target for future preclinical development as a radiosensitizer in NSCLC.Item SMARCA4/BRG1-Inactivating Mutations as Potential Predictive Markers for Aurora Kinase A-Targeted Therapy in NSCLCs(2014-05-28) Tagal, Vural; White, Michael A.; Roth, Michael G.; Minna, John D.; Cobb, Melanie H.SMARCA4 encodes a catalytic subunit of the SWI/SNF chromatin remodeling complex, BRG1. Frequent occurrence of SMARCA4/BRG1-inactivating mutations and their mutually exclusive nature from EGFR and ALK lesions create one of the largest subsets of Non-Small Cell Lung Cancers (NSCLCs). Since these mutations have been identified as bona fide tumor suppressors, efforts have focused on understanding the pathology of cancer caused by SMARCA4/BRG1 aberrations. However, no therapeutic agent has been identified as synthetically lethal with SMARCA4/BRG1 loss. Utilizing genome-wide high-throughput small interfering RNA (siRNA)-based screening, we show here that Aurora kinase A (AURKA) activity is essential in NSCLCs carrying SMARCA4/BRG1-inactivating mutations. RNAi-mediated depletion or chemical inhibition of AURKA induces apoptosis and diminish cellular viability in SMARCA4/BRG1-mutant NSCLC cells in vitro and in mouse models. The relation between SMARCA4/BRG1 inactivation and increased requirement for AURKA appears to be due to the impairment of functional centrosomes. Thus, AURKA-centered, centrosome-independent, mitotic spindle assembly machinery becomes solely responsible for mitotic spindle formation and proper chromosome segregation during mitosis. DLG7, the only known protein specific to this centrosome-independent mitotic spindle assembly, is required for the survival and proliferation of cells with inactivated SMARCA4/BRG1. Depletion of DLG7 causes no effect in SMARCA4/BRG1-proficient cells, but significant decrease in cell viability occurs in SMARCA/BRG1-deficient NCI-H1819 cells and this cytotoxic effect can be rescued with the restoration of wild-type SMARCA4/BRG1 expression. Altogether, our findings identify AURKA inhibition with VX-680 as a candidate therapeutic strategy for biomarker-driven clinical studies to treat the NSCLCs harboring SMARCA4/BRG1 inactivation mutations, which account for approximately 35% of all NSCLC cases. Furthermore, these observations suggest a previously unrecognized concept of redundancy for mitotic spindle assembly machinery that has a potential use for cancer therapeutics.