p73 expression and function in vestibular schwannoma.
OBJECTIVE
To determine the expression of the p53 family member p73 in vestibular schwannoma (VS) and to determine the potential role of this tumor suppressor in regulating the proliferation of HEI193, a human papillomavirus E6-E7 immortalized VS cell line.


METHODS
Immunohistochemical staining was used to investigate the expression of p73 in 34 cases of archived VS tissue, while Western blot analysis and immunofluorescence were performed to demonstrate the expression and localization of p73 in HEI193. After transfection of a full-length p73 plasmid (TAp73alpha), flow cytometry analysis was performed to determine the effect of p73 expression on cell cycle distribution, while annexin V-FITC (fluorescein isothiocyanate) analysis and TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling) assay were used to measure apoptosis. The effect of p73 expression on ionizing radiation-induced cell death was also investigated with annexin V staining, TUNEL assay, and flow cytometry analysis.


RESULTS
Of the 34 vestibular schwannoma tissues examined, p73 was expressed in 14 (41%) but was not expressed in HEI193. Transfection of p73 alone resulted in increased apoptosis and necrosis, and G(1) accumulation with concomitant induction of p21. The presence of p73 also significantly increased early apoptosis (P = .046), late apoptosis (P < .001), and necrosis (P = .009) on exposure of the HEI193 cells to ionizing radiation.


CONCLUSIONS
Forced expression of p73, perhaps by gene therapy, to induce apoptosis directly or to sensitize VS tumors to ionizing radiation may have relevant therapeutic applications.
Ahmad
Zana K
ZK
Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of California, San Diego, La Jolla, CA 92093-0612, USA.
Altuna
Xabier
X
Lopez
Jay Patrick
JP
An
Yi
Y
Wang-Rodriguez
Jessica
J
Juneja
Vikram R
VR
Chen
Jocelyn S
JS
Arandazi
Maria Jesus
MJ
Aguilera
Joseph
J
Harris
Jeffrey P
JP
Ongkeko
Weg M
WM
D000328:Adult; D000368:Aged; D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis / Q000502:physiology; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D015316:Genetic Therapy; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000378:metabolism* / Q000628:therapy; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D050725:Papillomavirus E7 Proteins; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D012189:Retrospective Studies; D014162:Transfection; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000502:physiology*
D017304:Annexin A5; D004268:DNA-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D012097:Repressor Proteins; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; C059731:oncogene protein E7, Human papillomavirus type 16; D011505:Protein-Tyrosine Kinases