Discovery of TP53 splice variants in two novel papillary urothelial cancer cell lines.
BACKGROUND
Using a novel cell culture technique, we established two new cell lines, BC44 and BC61, from papillary urothelial carcinoma and analyzed them for genetic changes typical of this tumor type.


RESULTS
Karyotyping revealed aneuploid karyotypes with loss of chromosome 9 and rearranged chromosome 5p. Molecular analysis showed CDKN2A deletions but wild-type PIK3CA. BC61 contained a G372C FGFR3 mutation. TP53 was not mutated in either cell line and BC61 expressed normal full-length protein. In contrast, BC44 exclusively expressed cytoplasmic and nuclear p53Δ40 and 133 isoforms from the alternative promoter P2 as revealed by Western blotting, immunocytochemistry and PCR. The only discernible difference in TP53 in BC44 was homozygosity for the deletion allele of the rs17878362 polymorphism in the P2 promoter. Expression of p53 isoforms was also detected in a few other urothelial carcinoma cell lines and tumor cultures and in 4 out of 28 carcinoma tissues.


CONCLUSIONS
In urothelial cancers, TP53 is typically inactivated by mutations in one allele and loss of the wildtype allele and more frequently in invasive compared to papillary carcinomas. We show that some urothelial carcinomas may predominantly or exclusively express isoforms which are not detected by commonly used antibodies to epitopes located in the p53 TA amino-terminal region. Expression of these isoforms may constitute a further mode of p53 inactivation in urothelial carcinoma. Our findings raise the question to which extent this mechanism may compromise wildtype p53 function in papillary tumors in particular, where point mutations in the gene are rare.
Urologische Klinik, Heinrich-Heine-Universität, Düsseldorf, Germany.
Annemarie
A
Koch
Jiri
J
Hatina
Harald
H
Rieder
Hans-Helge
HH
Seifert
Wolfgang
W
Huckenbeck
Frank
F
Jankowiak
Andrea R
AR
Florl
Robert
R
Stoehr
Wolfgang A
WA
Schulz
D017398:Alternative Splicing; D001483:Base Sequence; D015153:Blotting, Western; D002291:Carcinoma, Papillary / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002869:Chromosome Aberrations; D055028:Comparative Genomic Hybridization; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D004252:DNA Mutational Analysis; D006801:Humans; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D032681:Spectral Karyotyping; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019459:Urothelium / Q000378:metabolism* / Q000473:pathology
D019941:Cyclin-Dependent Kinase Inhibitor p16; D020033:Protein Isoforms; D016159:Tumor Suppressor Protein p53; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3