c-myc in bladder cancer. Clinical findings and analysis of mechanism.
The c-myc gene product is known to be involved in the regulation of cell proliferation and differentiation. Altered c-myc gene expression is a common event in a variety of tumors. This study was designed to investigate c-myc overexpression in transitional cell carcinoma (TCC). The first part was designed to investigate the frequency of c-myc overexpression in relation to tumor stage and tumor grade. A second set of experiments was directed at the mechanisms underlying c-myc overexpression in TCC. A total of 185 paraffin-embedded urothelial tissue specimens were investigated immunohistochemically for c-myc overexpression. A single case of overexpression (6%) was observed in normal urothelial tissue (n = 16). c-myc overexpression was also infrequent in carcinoma in situ (TIS) (7/39 = 18%). In contrast, papillary urothelial tumors (n = 65) yielded c-myc overexpression in 38 cases (58%). Investigation of infiltrating bladder tumors revealed c-myc overexpression in 56% of T1 tumors and 59% of muscle-infiltrating tumors. The staining pattern in multifocal tumors was heterogeneous in 10 of 18 cases. Similarly, only 12 of 28 patients with tumor recurrences showed the same c-myc staining pattern in the primary tumor and in tumor recurrences. c-myc overexpression did not correlate with tumor grade or tumor progression. Nevertheless, the high frequency of c-myc overexpression in urothelial carcinoma suggests an important role for this protein in urothelial carcinoma. Therefore, the mechanism underlying c-myc overexpression was further investigated in six bladder carcinoma cell lines. Southern blot experiments under standardized conditions showed no significant gene amplification. The comparison of c-myc mRNA expression to that of histone H3 as a measure of cell proliferation revealed a moderate correlation (r = 0.45) in the six cell lines examined. These data suggest that in accord with its established role as a cell cycle competence factor, c-myc may be necessary but not sufficient for the induction of proliferation in urothelial carcinoma.
Schmitz-Dräger
B J
BJ
Urologische Klinik, Heinrich-Heine Universität, Dusseldorf, Germany.
Schulz
W A
WA
Jürgens
B
B
Gerharz
C D
CD
van Roeyen
C R
CR
Bültel
H
H
Ebert
T
T
Ackermann
R
R
D000368:Aged; D015152:Blotting, Northern; D015139:Blotting, Southern; D002295:Carcinoma, Transitional Cell / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division; D005260:Female; D006657:Histones / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology
D006657:Histones; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger