title: Pooled shRNA screen for sensitizers to inhibition of the mitotic regulator polo-like kinase (PLK1).
abstract: RNAi screening holds the promise of systemizing the search for combination therapeutic strategies. Here we performed a pooled shRNA library screen to look for promising targets to inhibit in combination with inhibition of the mitotic regulator polo-like kinase (PLK1). The library contained ~4,500 shRNAs targeting various signaling and cancer-related genes and was screened in four lung cancer cell lines using both high (IC80) and low (IC20) amounts of the PLK1 inhibitor GSK461364. The relative abundance of cells containing individual shRNAs following drug treatment was determined by microarray analysis, using the mock treatment replicates as the normalizing reference. Overall, the inferred influences of individual shRNAs in both high and low drug treatment were remarkably similar in all four cell lines and involved a large percentage of the library. To investigate which functional categories of shRNAs were most prominent in influencing drug response, we used statistical analysis of microarrays (SAM) in combination with a filter for genes that had two or more concordant shRNAs. The most significant functional categories that came out of this analysis included receptor tyrosine kinases and nuclear hormone receptors. Through individual validation experiments, we determined that the two shRNAs from the library targeting the nuclear retinoic acid receptor gene RARA did indeed silence RARA expression and as predicted conferred resistance to GSK461364. This led us to test whether activation of RARA receptor with retinoids could sensitize cells to GSK461364. We found that retinoids did increase the drug sensitivity and enhanced the ability of PLK1 inhibition to induce mitotic arrest and apoptosis. These results suggest that retinoids could be used to enhance the effectiveness of GSK461364 and provide further evidence that RNAi screens can be effective tools to identify combination target strategies.
authors.affiliation: Cancer Genome Center, Cold Spring Harbor Laboratory, Woodbury, NY 11797, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Liu-Sullivan
authors.forename: Jianping
authors.initials: J
authors.lastname: Zhang
authors.forename: Amy
authors.initials: A
authors.lastname: Bakleh
authors.forename: John
authors.initials: J
authors.lastname: Marchica
authors.forename: Jinyu
authors.initials: J
authors.lastname: Li
authors.forename: Despina
authors.initials: D
authors.lastname: Siolas
authors.forename: Sylvie
authors.initials: S
authors.lastname: Laquerre
authors.forename: Yan Y
authors.initials: YY
authors.lastname: Degenhardt
authors.forename: Richard
authors.initials: R
authors.lastname: Wooster
authors.forename: Kenneth
authors.initials: K
authors.lastname: Chang
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Hannon
authors.forename: Scott
authors.initials: S
authors.lastname: Powers
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001562:Benzimidazoles / Q000494:pharmacology*; D054316:Biomarkers, Pharmacological; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D046228:Microarray Analysis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics* / Q000494:pharmacology; D018168:Receptors, Retinoic Acid / Q000037:antagonists & inhibitors / Q000235:genetics; D000072482:Retinoic Acid Receptor alpha; D012176:Retinoids / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics; D013876:Thiophenes / Q000494:pharmacology*; D000097869:Polo-Like Kinase 1
chemical_list: D001562:Benzimidazoles; D054316:Biomarkers, Pharmacological; D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D012176:Retinoids; D013876:Thiophenes; D000097869:Polo-Like Kinase 1; C561573:GSK 461364; C000607071:RARA protein, human