Small interfering RNA library screen of human kinases and phosphatases identifies polo-like kinase 1 as a promising new target for the treatment of pediatric rhabdomyosarcomas.
Rhabdomyosarcoma, consisting of alveolar (aRMS) and embryonal (eRMS) subtypes, is the most common type of sarcoma in children. Currently, there are no targeted drug therapies available for rhabdomyosarcoma. In searching for new molecular therapeutic targets, we carried out genome-wide small interfering RNA (siRNA) library screens targeting human phosphatases (n = 206) and kinases (n = 691) initially against an aRMS cell line, RH30. Sixteen phosphatases and 50 kinases were identified based on growth inhibition after 72 hours. Inhibiting polo-like kinase 1 (PLK1) had the most remarkable impact on growth inhibition (approximately 80%) and apoptosis on all three rhabdomyosarcoma cell lines tested, namely, RH30, CW9019 (aRMS), and RD (eRMS), whereas there was no effect on normal muscle cells. The loss of PLK1 expression and subsequent growth inhibition correlated with decreased p-CDC25C and Cyclin B1. Increased expression of WEE 1 was also noted. The induction of apoptosis after PLK1 silencing was confirmed by increased p-H2AX, propidium iodide uptake, and chromatin condensation, as well as caspase-3 and poly(ADP-ribose) polymerase cleavage. Pediatric Ewing's sarcoma (TC-32), neuroblastoma (IMR32 and KCNR), and glioblastoma (SF188) models were also highly sensitive to PLK1 inhibition. Finally, based on cDNA microarray analyses, PLK1 mRNA was overexpressed (>1.5 fold) in 10 of 10 rhabdomyosarcoma cell lines and in 47% and 51% of primary aRMS (17 of 36 samples) and eRMS (21 of 41 samples) tumors, respectively, compared with normal muscles. Similarly, pediatric Ewing's sarcoma, neuroblastoma, and osteosarcoma tumors expressed high PLK1. We conclude that PLK1 could be a promising therapeutic target for the treatment of a wide range of pediatric solid tumors including rhabdomyosarcoma.
Hu
Kaiji
K
Laboratory for Oncogenomic Research, Department of Pediatrics, Experimental Medicine, and Medical Genetics, University of British Columbia, Vancouver, BC, Canada.
Lee
Cathy
C
Qiu
Dexin
D
Fotovati
Abbas
A
Davies
Alastair
A
Abu-Ali
Samah
S
Wai
Daniel
D
Lawlor
Elizabeth R
ER
Triche
Timothy J
TJ
Pallen
Catherine J
CJ
Dunn
Sandra E
SE
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001859:Bone Neoplasms / Q000201:enzymology / Q000235:genetics / Q000628:therapy; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D002648:Child; D002675:Child, Preschool; D020868:Gene Silencing; D015316:Genetic Therapy / Q000379:methods*; D005909:Glioblastoma / Q000201:enzymology / Q000235:genetics / Q000628:therapy; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D009447:Neuroblastoma / Q000201:enzymology / Q000235:genetics / Q000628:therapy; D012516:Osteosarcoma / Q000201:enzymology / Q000235:genetics / Q000628:therapy; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics*; D012208:Rhabdomyosarcoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D012512:Sarcoma, Ewing / Q000201:enzymology / Q000235:genetics / Q000628:therapy; D014162:Transfection; D000097869:Polo-Like Kinase 1
D018797:Cell Cycle Proteins; D010744:Phosphoric Monoester Hydrolases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D000097869:Polo-Like Kinase 1