title: p16INK4A and p14ARF tumor suppressor pathways are deregulated in malignant rhabdoid tumors.
abstract: Malignant rhabdoid tumors (MRTs) are aggressive tumors associated with mutations in the SMARCB1 gene. In experimental systems, the loss of SMARCB1 is hypothesized to alter p16(INK4A) pathways resulting in the repression of tumor suppressors. To determine whether these pathways are deregulated in human MRT, we used immunohistochemistry on tissue microarrays to evaluate p16(INK4A)/E2F1/RB and p14(ARF)/MDM2/p53 pathways in 25 atypical teratoid/rhabdoid tumors (AT/RT) and 11 non-CNS MRT. p16(INK4A) was negative or showed focal weak expression. p16(INK4A) downstream targets CDK4/cyclin D1/ppRB were variably expressed at moderate to low levels; E2F1 was negative. Unexpectedly, p14(ARF) expression was seen in many cases, which correlated positively with p53 and inversely with MDM2 immunostaining in AT/RT. TP53 mutational analysis in 19 of 25 AT/RT and in 8 of 11 non-CNS MRT cases showed point mutations in only 3 AT/RT cases, suggesting that p53 expression was driven mainly by p14(ARF). Finally, nucleophosmin, a protein that stabilizes p53, was positive in most cases and colocalized with p53. Together, these data suggest that, in MRT, there is deregulation not only of p16(INK4A) but also of the p14(ARF) pathway. These results provide insights into cell cycle deregulation in the pathogenesis of human MRT and may aid in the design and evaluation of potential therapies for these tumors.
authors.affiliation: Division of Neuropathology, Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania, USA.
authors.forename: Sriram
authors.initials: S
authors.lastname: Venneti
authors.forename: Paul
authors.initials: P
authors.lastname: Le
authors.forename: Daniel
authors.initials: D
authors.lastname: Martinez
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Eaton
authors.forename: Nikhil
authors.initials: N
authors.lastname: Shyam
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Jordan-Sciutto
authors.forename: Bruce
authors.initials: B
authors.lastname: Pawel
authors.forename: Jaclyn A
authors.initials: JA
authors.lastname: Biegel
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Judkins
mesh_terms: D002675:Child, Preschool; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D046228:Microarray Analysis; D000071796:SMARCB1 Protein; D012720:Severity of Illness Index; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D018709:Statistics, Nonparametric; D013724:Teratoma / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53