INI1 induces interferon signaling and spindle checkpoint in rhabdoid tumors.
OBJECTIVE
Rhabdoid tumors are rare but aggressive pediatric malignancies characterized by biallelic loss of INI1/hSNF5. Reintroduction of INI1 causes cell arrest and senescence in rhabdoid cells. Our purpose was to identify INI1-downstream genes and to determine their functional and therapeutic significance for rhabdoid tumors.


METHODS
INI1 downstream targets in rhabdoid cells were identified using a cDNA microarray analysis and the expression of selected INI1 targets was confirmed by quantitative reverse transcription-PCR, Western analysis, and/or immunohistochemical analysis of rhabdoid cells and primary rhabdoid tumors. To determine the functional significance of downstream targets, activated targets of INI1 were induced and repressed targets of INI1 were knocked down (by using RNA interference) in rhabdoid cells, in the absence of INI1. Consequence of altered expression of INI1 downstream targets for rhabdoid cell survival, cell cycle, and apoptosis was assessed.


RESULTS
Microarray studies indicated that INI1 activated IFN-stimulated genes at early time points and senescence markers at late time points and repressed mitotic genes such as Polo like kinase 1 (PLK1), selectively in rhabdoid cells. Treatment of rhabdoid cells with recombinant IFNs resulted in induction of IFN-stimulated genes, G1 arrest, and flat cell formation. PLK1 was overexpressed in primary human and mouse rhabdoid tumors. RNA interference-mediated knock down of PLK1 in rhabdoid cells resulted in mitotic arrest, aberrant nuclear division, decreased survival, and induction of apoptosis.


CONCLUSIONS
Targeting downstream effectors of INI1 such as IFN pathway and mitotic genes leads to antiproliferative effects in rhabdoid cells. IFN treatment and down-modulation of PLK1 constitute potential novel therapeutic strategies for rhabdoid tumors.
Morozov
Alexei
A
Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Lee
Seung Jae
SJ
Zhang
Zhi-Kai
ZK
Cimica
Velasco
V
Zagzag
David
D
Kalpana
Ganjam V
GV
D017209:Apoptosis; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007372:Interferons / Q000494:pharmacology*; D008938:Mitosis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D017471:Receptors, Interferon / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D018335:Rhabdoid Tumor / Q000378:metabolism* / Q000473:pathology; D000071796:SMARCB1 Protein; D015398:Signal Transduction / Q000502:physiology*; D008941:Spindle Apparatus / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*; D000097869:Polo-Like Kinase 1
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D007372:Interferons; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D017471:Receptors, Interferon; D011994:Recombinant Proteins; D000071796:SMARCB1 Protein; D014157:Transcription Factors; D000097869:Polo-Like Kinase 1; C513266:SMARCB1 protein, human