Editors' ChoiceCell Survival

RNAi Screen for Sensitivity to Chemotherapeutics

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Science's STKE  07 Jun 2005:
Vol. 2005, Issue 287, pp. tw211
DOI: 10.1126/stke.2872005tw211

Inappropriate cell death or cell survival can lead to various diseases, such as neurodegenerative disorders (excessive cell death) and cancer (excessive cell survival). MacKeigan et al. performed large-scale RNA interference (RNAi) screens using small interfering RNAs (siRNAs) transfected into cultured human cell lines to identify kinases and phosphatases involved in cell survival. The authors identified 73 kinases (11% of the kinases in HeLa cells) and 72 phosphatases (32% of the phosphatases in HeLa cells) as positively contributing to cell survival, based on an increase in markers for apoptotic cell death upon the knockdown of these proteins. The phosphatase siRNA library was also used to screen for phosphatases that attenuate cell death. HeLa cells were transfected with the phosphatase siRNAs and then also exposed to apoptosis-inducing pharmaceuticals (cisplatin, Taxol, etopside), and 12 phosphatases were identified that, when knocked down, conferred resistance to apoptosis. The RNAi screens were also used to identify kinases that, when knocked down, conferred an increased sensitivity to apoptosis-inducing drugs. Using this approach, it is possible to predict what combinations of chemotherapeutic agents may be most effective. The authors demonstrated that Taxol combined with the siRNA for SGK (serum and glucocorticoid-regulated kinase), the siRNA for the tyrosine kinase FER, the siRNA for CDK8 (cyclin-dependent kinase 8), or the siRNA for mTOR all increased cell death compared with the siRNA alone or the drug alone. This type of screen may lead to new combinations of therapies for cancers and can be applied to cell lines or cancers with different cell survival signaling pathways, thus allowing tailoring of the chemotherapy to the cancer. For example, the authors also tested for sensitization to apoptosis-inducing drugs in the breast carcinoma cell line BT474, which exhibits less sensitivity to survival kinase knockdown than do the HeLa cells. Indeed, Taxol synergized with siRNA for FER, JIK (JNK inhibitory kinase, also known as Ste20-like kinase), or PLK2 (Polo-like kinase 2) to promote cell death. Thus, this type of global genomic screen may serve to point to novel chemotherapeutic combination therapies with existing drugs, as well as to identify novel targets for regulating cell death.

J. P. MacKeigan, L. O. Murphy, J. Blenis, Sensitized RNAi screen of human kinases and phosphatases identifies new regulators of apoptosis and chemoresistance. Nat. Cell Biol. 7, 591-600 (2005). [PubMed]

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