p73 Expression in human normal and tumor tissues: loss of p73alpha expression is associated with tumor progression in bladder cancer.
OBJECTIVE
To characterize the expression profile of p73 in human normal tissues by immunohistochemistry (IHC) and to analyze the correlation between p73 expression and bladder cancer progression.


METHODS
CJDp73 was characterized for p73alpha detection in Western blot and IHC through its application to isoform-transfected 293 cells. Normal tissues were analyzed by IHC with the CJDp73 antiserum. Transitional cell carcinoma (TCC)-derived cell lines were subjected to reverse transcription-PCR and Western blot. TCC tissue microarrays were analyzed for p73alpha expression by IHC, and the results were statistically analyzed.


RESULTS
p73 immunostaining was nuclear and restricted to epithelial cells of certain organs such as squamous epithelium of the epidermis and transitional epithelium of the bladder. The expression was also observed in certain specialized glandular epithelia such as acinar cells of breast and parotid gland. Four of seven TCC-derived cell lines had low to undetectable p73alpha protein levels. We found undetectable or low p73alpha expression in 104 of 154 (68%) TCC cases, this phenotype being more frequently observed in invasive tumors when compared with superficial lesions. This association was statistically significant (P < 0.0001). We also observed a significant association between p53, p63, and p73alpha alterations with bladder cancer progression (P < 0.0001).


CONCLUSIONS
p73alpha plays a tumor suppressor role in bladder cancer, and its inactivation occurs through an epigenetic mechanism, most probably involving protein degradation.
Puig
Pere
P
Division of Molecular Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Capodieci
Paola
P
Drobnjak
Marija
M
Verbel
David
D
Prives
Carol
C
Cordon-Cardo
Carlos
C
Di Como
Charles J
CJ
D002460:Cell Line; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics*; D018450:Disease Progression; D005260:Female; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics*; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000032:analysis; D012016:Reference Values; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000473:pathology*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012334:RNA, Neoplasm; D011994:Recombinant Proteins; C000606460:TP73 protein, human; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D012313:RNA