Decreased DOC-2/DAB2 expression in urothelial carcinoma of the bladder.

PURPOSE

DOC-2/DAB2 (differentially expressed in ovarian carcinoma-2/disabled-2), a potential tumor suppressor gene, is underexpressed in several cancers. Little is known about the expression of this gene in urothelial carcinoma of the bladder (UCB). We profiled DOC-2/DAB2 expression in mouse and human normal and neoplastic urothelia.

EXPERIMENTAL DESIGN

Immunohistochemical staining for DOC-2/DAB2 was carried out on tissue specimens from two transgenic mouse models with urothelium-specific molecular alterations and on a tissue microarray containing cores from 9 normal controls, 44 patients who underwent transurethral resection of the bladder tumor (TURBT), 195 patients who underwent radical cystectomy for UCB, and 39 lymph nodes with metastatic UCB.

RESULTS

Normal mouse urothelium stained uniformly with DOC-2/DAB2. Weaker staining was observed in low-grade, superficial papillary bladder tumors from transgenic mice harboring constitutively active Ha-Ras, whereas carcinoma in situ-like lesions and high-grade bladder tumors from transgenic mice expressing a SV40 T antigen completely lacked DOC-2/DAB2 expression. In human tissues, DOC-2/DAB2 expression was decreased in 11% of normal bladder specimens, 59% of TURBT specimens, 65% of radical cystectomy specimens, and 77% of the metastatic lymph node specimens. Decreased DOC-2/DAB2 expression was associated with advanced pathologic stage (P = 0.023), lymph node metastases (P = 0.050), and lymphovascular invasion (P < 0.001). In univariable, but not in multivariable analysis, decreased DOC-2/DAB2 was associated with an increased probability of bladder cancer recurrence (log-rank test, P = 0.020) and bladder cancer-specific mortality (log-rank test, P = 0.023).

CONCLUSIONS

Decreased DOC-2/DAB2 expression seems to occur early in bladder tumorigenesis and becomes more prominent in advanced stages of UCB.