RNAi-based technologies have the potential to enhance many aspects of the anti-cancer drug development process. The increased use of anti-cancer therapeutics targeting specific genetic characteristics (e.g., a fusion transcript or over-expression/amplification of a gene) illustrates the impact molecular analysis has had on the development of anti-tumor agents. Further, there is growing awareness that the genetic background of an individual can influence a patients response to anti-cancer therapeutics. Studies focused on assessing the contribution of genetic and transcriptional variation to a drug response phenotype have become more sophisticated as larger data sets integrating drug-activity with genome-wide DNA/RNA analysis are reported. However, functional approaches to understanding the relationships predicted by these studies have been lacking. We are using RNAi analysis and screening to probe the impact of gene-specific expression on drug-activity, including identification of new proteins that directly or indirectly modulate the pharmacology of anti-cancer therapeutics. We have used the power of RNAi analysis to investigate gene-drug interactions, including study of multi-drug resistance and the activity of the anti-leukemia agent L-Asparaginase. We have also initiated screens that combine RNAi with drug administration. The identification of molecular targets that can act to modulate the activity of anti-cancer drugs has become an important application for RNAi screening approaches. This approach combines RNAi with administration of a small molecule compound or biologic to identify proteins whose down-regulation modulates the activity of a therapeutic agent. This approach has the potential to enhance the clinical application of an established or investigational drug by: (1) identifying synergistic molecular targets that exploit complementary vulnerabilities within a cancer cell, (2) enabling the use of lower concentrations of a drug that exhibits dose-dependent non-specific toxicities, (3) overcoming drug resistance, and, (4) broadening the clinical application of a drug to other cancer types. We began our drug-RNAi screening projects focusing on a chemosensitization (synthetic-lethal) approach using a clinical relevant drug with a defined molecular target and mode of action, the topoisomerase 1 inhibitor camptothecin (CPT), to enable validation of our screens in the context of established drug activity. In FY11 we published a study that identified TGF beta activated kinase 1 TAK1 as a sensitizing target of CPT. Silencing of TAK1 through RNAi enhances the sensitivity of several cell types to CPT. We also identified TAB2 a binding partner of TAK1 and TRAF6, an upstream activator of TAK1 as sensitizing targets of CPT. This work is likely to enhance our understanding of the cell response to the DNA damage induced by topoisomerase 1 inhibitors and could be used as the basis of improved application of these inhibitors through the use of agents that target the TRAF6/TAK1/TAB2 signaling response. We are currently using RNAi screening strategies to examine drugs with less defined or more complex mechanisms of action and/or drugs undergoing pre-clinical or early clinical testing.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Investigator-Initiated Intramural Research Projects (ZIA)
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National Cancer Institute Division of Basic Sciences
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Maachani, Uday Bhanu; Kramp, Tamalee; Hanson, Ryan et al. (2015) Targeting MPS1 Enhances Radiosensitization of Human Glioblastoma by Modulating DNA Repair Proteins. Mol Cancer Res 13:852-62
Garimella, Sireesha V; Gehlhaus, Kristie; Dine, Jennifer L et al. (2014) Identification of novel molecular regulators of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in breast cancer cells by RNAi screening. Breast Cancer Res 16:R41
Tandle, Anita T; Kramp, Tamalee; Kil, Whoon J et al. (2013) Inhibition of polo-like kinase 1 in glioblastoma multiforme induces mitotic catastrophe and enhances radiosensitisation. Eur J Cancer 49:3020-8
Bennett, Christina N; Tomlinson, Christine C; Michalowski, Aleksandra M et al. (2012) Cross-species genomic and functional analyses identify a combination therapy using a CHK1 inhibitor and a ribonucleotide reductase inhibitor to treat triple-negative breast cancer. Breast Cancer Res 14:R109
Martin, S E; Wu, Z-H; Gehlhaus, K et al. (2011) RNAi screening identifies TAK1 as a potential target for the enhanced efficacy of topoisomerase inhibitors. Curr Cancer Drug Targets 11:976-86
Murrow, Lyndsay M; Garimella, Sireesha V; Jones, Tamara L et al. (2010) Identification of WEE1 as a potential molecular target in cancer cells by RNAi screening of the human tyrosine kinome. Breast Cancer Res Treat 122:347-57
Zhang, Yong-Wei; Jones, Tamara L; Martin, Scott E et al. (2009) Implication of checkpoint kinase-dependent up-regulation of ribonucleotide reductase R2 in DNA damage response. J Biol Chem 284:18085-95
Jobson, Andrew G; Lountos, George T; Lorenzi, Philip L et al. (2009) Cellular inhibition of checkpoint kinase 2 (Chk2) and potentiation of camptothecins and radiation by the novel Chk2 inhibitor PV1019 [7-nitro-1H-indole-2-carboxylic acid {4-[1-(guanidinohydrazone)-ethyl]-phenyl}-amide]. J Pharmacol Exp Ther 331:816-26
Calcagno, A M; Fostel, J M; To, K K W et al. (2008) Single-step doxorubicin-selected cancer cells overexpress the ABCG2 drug transporter through epigenetic changes. Br J Cancer 98:1515-24